首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2242篇
  免费   88篇
  2023年   15篇
  2021年   10篇
  2020年   35篇
  2019年   40篇
  2018年   75篇
  2017年   74篇
  2016年   87篇
  2015年   55篇
  2014年   64篇
  2013年   666篇
  2012年   82篇
  2011年   88篇
  2010年   75篇
  2009年   71篇
  2008年   59篇
  2007年   72篇
  2006年   58篇
  2005年   33篇
  2004年   24篇
  2003年   15篇
  2002年   24篇
  2001年   22篇
  2000年   18篇
  1999年   30篇
  1998年   20篇
  1997年   16篇
  1996年   21篇
  1995年   16篇
  1994年   14篇
  1993年   20篇
  1992年   17篇
  1991年   21篇
  1989年   11篇
  1988年   14篇
  1987年   18篇
  1986年   23篇
  1985年   18篇
  1984年   17篇
  1983年   19篇
  1982年   23篇
  1981年   20篇
  1980年   14篇
  1979年   15篇
  1978年   14篇
  1977年   13篇
  1976年   15篇
  1975年   16篇
  1973年   13篇
  1969年   11篇
  1967年   15篇
排序方式: 共有2330条查询结果,搜索用时 15 毫秒
991.
The author, an authority on the agriculture of Transcaucasia, traces the evolution of the new Soviet system of interfarm integration at the rayon (minor civil division) level and the development of a new agribusiness administration combining all farm-related and food-related activities. Since the initial experimentation with rayon-level integration (known by the Russian acronym RAPO) in the Georgian SSR in the early 1970s (notably in Abasha Rayon), the RAPO system of administration has been introduced throughout the Soviet Union. As of Jan. 1, 1984, there were 3,109 RAPO administrations in the USSR, comprising 95,975 separate enterprises with a total employment of 33.6 million people. The enterprises included 50,435 farms (mainly the nation's 26,000 collective farms and 23,000 state farms), 7,849 agricultural processing plants, 19,587 agricultural service enterprises and 7,361 rural construction agencies. The RAPO system of administration constitutes the lowest level of a new agribusiness hierarchy of management, represented at the republic and national levels of government by the consolidated Agroprom (Agribusiness) agencies.  相似文献   
992.
Two broad regions of the USSR most susceptible to dust storms, the southern East European Plain in the European USSR and the West Siberian Plain and adjacent areas of northern Kazakhstan, are contrasted according to a number of indicators of dust storm frequency and intensity. More specifically, the two regions, although roughly similar according to overall frequency of dust storms, were found to differ in terms of their interannual variability, years of peak activity, prevailing winds associated with dust storms, seasonal frequency, duration and erosive force of individual storms, and synoptic processes contributing to dust storm formation (translated by Jay K. Mitchell, PlanEcon, Inc., Washington, DC 20005).  相似文献   
993.
In areas in which 46 million Soviet citizens live, official statutory time is not observed. Most of these areas lie in the western part of the third Soviet time zone and date from 1930-31 when the Soviet Union adopted Daylight Saving Time on a year round basis. When an additional Summer Time was announced in 1980 (beginning in 1981 from April 1 to October 1), putting the clock two hours ahead of standard time for the summer, it was also announced that local deviations from statutory time would be terminated. In 1982, however, continued local deviations were noted, and some, in fact, permitted by the state. The explanation offered is that citizens and local readers in these areas wish to be on the same time as Moscow.  相似文献   
994.
Present and anticipated future environmental problems associated with past and projected development of the iron ore resources of the Kursk Magnetic Anomaly (KMA) (the most rapidly expanding production basin in the USSR) are outlined. The area's environmental problems recently have become a major concern, as a result of a heavy emphasis on accelerating production from surface mines in the basin, with few resources being allocated for land reclamation and pollution control activities (see Soviet Geography, November 1986, pp. 679-682 and May 1988, p. 537). Major attention is given to identifying development strategies mitigating further environmental disruption and experimentation with promising land reclamation and pollution control measures (translated by Andrew R. Bond).  相似文献   
995.
996.
Abstract

In reaction to the oil‐price shocks of 1973/4 and 1978/9 both of the German states reconsidered coal refinement as a technological answer to economic and political constraints. In the GDR the chemical industry in particular could not do without this technology, but the state did not undertake a major R&D programme, preferring rather to continue with existing plants and processes. The disastrous consequences of this policy were felt when the Soviet Union cut off oil supplies to the GDR in the early 1980s, so damaging irreversibly not only the chemical industry, but the entire East Germany economy too. In the FRG the chemical industry was an active interlocuter with the federal government but notwithstanding the offer of generous subsidies was always prudent about the need for a switch back to coal from oil, and believed that new R&D programmes in the coal refining area were not imperative given Western German leadership in the field. In the event it was sectors of the economy other than the chemical industry which benefitted from the federal government's concerns about the oil price rises in the 1970s.  相似文献   
997.
On a political level, Swedish transport ethanol has always been embedded in visions of an alternative, brighter future. Arguments in support of ethanol have been reiterated throughout the 20th and 21st centuries, exhibiting a striking stability over time. At the same time, the contexts in which arguments for ethanol have been raised have undergone dramatic shifts. This article investigates the historical contingencies of three empirical cases, covering the interwar years, the aftermath of the oil crises of the 1970s and the 21st century's concerns over global warming. It concludes with the observation that despite political convictions about ethanol's commercial, military and environmental potential, domestic production has not managed to take off on its own. It has relied on state support such as tax exemptions, it has been dependent on other industries for feedstock provision and its technical superiority is still waiting for market confirmation.  相似文献   
998.

This paper analyzes the influence the Chemical Institute of Sarrià (IQS) ‐a private institution devoted both to the education of chemists and chemical engineers and to applied research‐ has had on Spain's chemical industry from 1916 onwards. The research reported is based upon three data sources (articles on industrial chemistry published by the IQS’ journal Afinidad and M. Se. theses; IQS graduates’ industrial activities; and technical services carried out by the Institute's staff for several companies). The main conclusion is that the IQS has had a remarkable impact on Catalan and Spanish industry. Although there are no other similar studies on Spanish scientific and technical institutions, the IQS case confirms that technical education and institutionalized research have a positive impact on the economic and industrial development of “latecomers” like Spain.  相似文献   
999.
This paper studies an attempt to replicate the Earth’s biosphere in the second half of the twentieth century with the aim of preserving and refashioning the environment as a self‐reproducing ecological system. Ecosystems dynamics framed the planet Earth as a closed system and directed scientific attention to questions of global environmental management. The image of the Earth as a spacecraft and operable in a similar way supported ideas of placing the environment in a laboratory setting. Using the case of Biosphere 2, launched in the Arizona desert in 1983, this paper studies the images of nature and environment contained in this quest to create an ecosystem and human habitat as good as, or superior to nature on Earth (known in this context as Biosphere 1). The second biosphere was designed as ‘a prototype for a space colony’ that would eventually enable its deteriorating predecessor, the Earthly biosphere, to reproduce and allow human settler societies to migrate to other planets. The paper draws on the cultural history of the ship in Western culture and on ships and spaceships as archetypes of autarkic enclosures set apart from nature. It argues that Biosphere 2 as an example of a technologically controlled endosphere advanced an understanding of the environment as a ‘life support system’ that emphasized not completeness but systems integrity, and was based on principles of functionality and replaceability. The paper will explore how notions of biospheric life support shaped demands on the natural and social environments in Biosphere 2 and Biosphere 1.  相似文献   
1000.
Abstract

The current system of federal advisory committees in the United States is both extensive and expanding. While there are significant differences between specific advisory bodies regarding their constitution, construction, and role in the process of public policy-making, the system itself facilitates the permanent institutionalization of linkages and dependencies between interest associations and federal administrative agencies. Indeed, it moves the role of pressure group influence on the policy-making process from that of a suspect input to that of a welcome withinput. Utilizing data derived from advisory committee compliance with the 1972 Federal Advisory Committee Act and selected case study material this article begins the process of exploring how the system functions, who participates in it, what impact it has on the development and formation of public policy, and who are its ultimate beneficiaries. It concludes by developing a framework for the assessment of potential advisory committee power and influence on the process of administrative policy-making and advances a preliminary assessment of the domination of industry interests on departmental advisory committees.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号