全文获取类型
收费全文 | 7744篇 |
免费 | 251篇 |
出版年
2020年 | 82篇 |
2019年 | 132篇 |
2018年 | 171篇 |
2017年 | 181篇 |
2016年 | 208篇 |
2015年 | 151篇 |
2014年 | 142篇 |
2013年 | 2259篇 |
2012年 | 220篇 |
2011年 | 228篇 |
2010年 | 239篇 |
2009年 | 219篇 |
2008年 | 175篇 |
2007年 | 169篇 |
2006年 | 151篇 |
2005年 | 110篇 |
2004年 | 99篇 |
2003年 | 79篇 |
2002年 | 88篇 |
2001年 | 124篇 |
2000年 | 94篇 |
1999年 | 110篇 |
1998年 | 97篇 |
1997年 | 86篇 |
1996年 | 93篇 |
1995年 | 72篇 |
1994年 | 76篇 |
1993年 | 82篇 |
1992年 | 80篇 |
1991年 | 65篇 |
1990年 | 51篇 |
1989年 | 76篇 |
1988年 | 68篇 |
1987年 | 91篇 |
1986年 | 65篇 |
1985年 | 83篇 |
1984年 | 85篇 |
1983年 | 104篇 |
1982年 | 78篇 |
1981年 | 95篇 |
1980年 | 100篇 |
1979年 | 77篇 |
1978年 | 65篇 |
1977年 | 103篇 |
1976年 | 75篇 |
1975年 | 77篇 |
1974年 | 50篇 |
1973年 | 45篇 |
1972年 | 49篇 |
1971年 | 51篇 |
排序方式: 共有7995条查询结果,搜索用时 15 毫秒
151.
152.
G. REX SMITH 《Arabian Archaeology and Epigraphy》1990,1(1):29-37
The article addresses some of the problems arising from the publication of a recent numismatic catalogue including coins from all parts of the Islamic world. The problems concern in particular the coins of the medieval Yemen and the article comprises a critique of those coins listed under the Arabian peninsula and the Yemen.
Catalogue nos. 101 and 104 are dealt with in some detail since they are erroneously ascribed to mints in Mecca and Minā, respectively. The former is struck in the name of a Zaydī imam, the latter is Rasulid and labelled as having been struck "for a special occasion". The intriguing question of the mysterious Ayyubid prince, al-'Ādil Abū Bakr, arises too (nos. 125 etc.), although no definitive answer can yet be suggested. Much more information is now available on the striking of coins in Tha'bāt during Rasulid times. A number of other points bearing on the numismatics, the history, and the geography of the medieval Yemen are discussed in the article. 相似文献
Catalogue nos. 101 and 104 are dealt with in some detail since they are erroneously ascribed to mints in Mecca and Minā, respectively. The former is struck in the name of a Zaydī imam, the latter is Rasulid and labelled as having been struck "for a special occasion". The intriguing question of the mysterious Ayyubid prince, al-'Ādil Abū Bakr, arises too (nos. 125 etc.), although no definitive answer can yet be suggested. Much more information is now available on the striking of coins in Tha'bāt during Rasulid times. A number of other points bearing on the numismatics, the history, and the geography of the medieval Yemen are discussed in the article. 相似文献
153.
F. Albarde J. Blichert‐Toft F. de Callataÿ G. Davis P. Debernardi L. Gentelli H. Gitler F. Kemmers S. Klein C. Malod‐Dognin J. Milot P. Tlouk M. Vaxevanopoulos K. Westner 《Archaeometry》2021,63(1):142-155
The reasons why the Western Mediterranean, especially Carthage and Rome, resisted monetization relative to the Eastern Mediterranean are still unclear. We address this question by combining lead (Pb) and silver (Ag) isotope abundances in silver coinage from the Aegean, Magna Graecia, Carthage and Roman Republic. The clear relationships observed between 109Ag/107Ag and 208Pb/206Pb reflect the mixing of silver ores or silver objects with Pb metal used for cupellation. The combined analysis of Ag and Pb isotopes reveals important information about the technology of smelting. The Greek world extracted Ag and Pb from associated ores, whereas, on the Iberian Peninsula, Carthaginians and Republican‐era Romans applied Phoenician cupellation techniques and added exotic Pb to Pb‐poor Ag ores. Massive Ag recupellation is observed in Rome during the Second Punic War. After defeating the Carthaginians and the Macedonians in the late second century bce , the Romans brought together the efficient, millennium‐old techniques of silver extraction of the Phoenicians, who considered this metal a simple commodity, with the monetization of the economy introduced by the Greeks. 相似文献
154.
Scientists advise limiting global warming to 1.5°C with substantial actions by 2030. Our viewpoint argues that climate response strategies in Canada have underemphasized and underestimated the potential contribution deep energy retrofits can make to greenhouse gas (GHG) emissions reductions, leading to inadequate responses in the building sector, and that Canada can (and should) be ambitious with building retrofits over the next decade. GHG savings from building retrofits can be realized more quickly than GHG reductions from other sectors, and either deliver net cost savings or are cost‐effective when compared to other mitigation measures. Retrofits can also provide social and economic benefits, such as improved health and comfort, and lower energy costs. This paper reviews energy use and building retrofits in Canada and argues the following should be implemented: (1) focus innovation on deep energy retrofit processes, not singular retrofit actions; (2) maximize both social and environmental benefits; (3) improve data gathering and availability for analysis and delivery; (4) innovate for a process of decisions and to avoid “dropouts” during the retrofit process; and (5) focus innovation on business models that maximize benefits. 相似文献
155.
While food allergy prevalence has been studied at the national level, we know little of food allergy prevalence or perceptions of prevalence/management at the local level. This paper uses Waterloo Region as a case study to 1) document self-reported individual and household food allergy and sensitivity prevalence at the local level; 2) investigate perceptions of food allergy prevalence; and 3) explore perceived confidence in anaphylaxis management. Survey data were collected from January to March 2019. Respondents (n = 500) self-reported individual and household food allergy and sensitivity, estimated the percentage of Canadians with food allergy, and were queried about their knowledge of food allergy management. Prevalence estimates were weighted to the structure of the 2016 Canadian Census, and univariate and bivariate analysis were conducted. Prevalence of self-reported food allergy was 12.1% (95%CI, 8.8%-15.3%), and prevalence of self-reported food sensitivity was 26.3% (95%CI, 21.9%-30.7%). When asked to estimate the percentage of Canadians with food allergy, the mean perceived percentage was 35.1% (SD = 22.96). Self-reported prevalence of food allergy appears higher in Waterloo Region, and the estimated percentage of Canadians with food allergy is inflated. Understanding prevalence and perceptions at the local level is important for targeted allocation of public health resources to ensure safe spaces for individuals with food allergy. 相似文献
156.
Juan Luis Gómez-Reino Santiago Lago-Peñas Jorge Martinez-Vazquez 《Journal of regional science》2023,63(4):793-819
The standard theory of optimal jurisdictional size hinges on the existence of economies of scale in the provision of local public goods and services. However, despite its relevance for forced local amalgamation programs and related policies, the empirical evidence on the existence of such economies of scale remains elusive. The main goal of this paper is to produce an updated and comprehensive quantitative review of the existence of economies of scale in the provision of local public goods using a meta-analysis approach to systematize the wide range of empirical approaches and modeling frameworks found in the previous literature. Our analysis confirms the presence of moderately increasing to constant returns to scale in the provision of local services with no reduction in the average costs of production in the delivery of most local public services beyond a certain, modest jurisdictional size, which many studies have estimated at 10,000 residents. Also, the potential for economies of scale differs at least across three traditional services: education, water and sanitation, and garbage collection, being highest for education and lowest for garbage collection. Our analysis also offers guidelines for future empirical research in this area. Physical output and production cost data should be used, together with translog specifications for the modeling of cost functions. Last, we find evidence that the determinants of output cost elasticity include bidirectional publication bias and population density but do not include the presence or absence of modern “lean” production technologies or the (perceived) capital intensity of the sector, contrary to conventional wisdom. These findings have significant policy implications for countries considering jurisdictional consolidation programs. 相似文献
157.
E. J. Fagan 《政策研究杂志》2023,51(2):243-263
This paper develops a theory of the relationship between policy disasters and political institutions. Policy disasters, defined as avoidable, unintended extreme negative policy outcomes, are important political, and historical events above that receive relatively little attention from political scientists and scholars of public policy. Using the predictions of punctuated equilibrium theory, I argue that systems with higher error accumulation will experience more policy disasters. Systems with more veto players and weaker information flows will experience more policy disasters, but information flows will have a stronger impact than veto players. I test this theory using data on financial crises and natural and technological disasters across 70 countries over 60 years. I find strong evidence that systems with weaker information flows and more veto players tend to have greater policy disaster risk. 相似文献
158.
Gísli Pálsson 《Anthropology today》2023,39(3):1-2
This guest editorial reflects on the relevance of anthropology for extinction concerns, a rapidly expanding practical, ethnographic and theoretical space at a time of impending mass extinction. While biological extinction is necessarily a multispecies development (usually implicating humans), traditional species talk – focused on taxonomies, collections and classification – needs critical rethinking as it necessarily diverts attention from the vitality of life. The broad discipline of anthropology has much to offer for understanding processes of extinction and recovery, fleshing out habitat problems and prospects of extinction, and advancing meaningful environmentalist practices. 相似文献
159.
Bruce G. Trigger 《Journal of Archaeological Research》1994,2(1):113-136
Publications and organizational developments relating to the history of archaeology from 1989 until June 1993 are critically examined. Attention is paid to the changing motivations for producing such publications, their shifting intellectual orientation, controversies, especially as they relate to internal vs external approaches and the epistemological status of explanations, problems of verification, and the status of these studies as a subfield within archaeology. 相似文献
160.