全文获取类型
收费全文 | 3867篇 |
免费 | 155篇 |
出版年
2020年 | 62篇 |
2019年 | 70篇 |
2018年 | 106篇 |
2017年 | 102篇 |
2016年 | 128篇 |
2015年 | 92篇 |
2014年 | 85篇 |
2013年 | 1184篇 |
2012年 | 94篇 |
2011年 | 102篇 |
2010年 | 98篇 |
2009年 | 91篇 |
2008年 | 96篇 |
2007年 | 81篇 |
2006年 | 67篇 |
2005年 | 63篇 |
2004年 | 55篇 |
2003年 | 40篇 |
2002年 | 58篇 |
2001年 | 59篇 |
2000年 | 32篇 |
1999年 | 53篇 |
1998年 | 24篇 |
1997年 | 34篇 |
1996年 | 27篇 |
1995年 | 23篇 |
1994年 | 39篇 |
1993年 | 33篇 |
1992年 | 35篇 |
1990年 | 32篇 |
1989年 | 29篇 |
1988年 | 32篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 36篇 |
1984年 | 52篇 |
1983年 | 55篇 |
1982年 | 48篇 |
1981年 | 39篇 |
1980年 | 34篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 32篇 |
1976年 | 32篇 |
1975年 | 35篇 |
1973年 | 28篇 |
1972年 | 35篇 |
1971年 | 21篇 |
1970年 | 32篇 |
1969年 | 21篇 |
排序方式: 共有4022条查询结果,搜索用时 15 毫秒
111.
H. MOMMSEN TH. BEIER H. DITTMANN D. HEIMERMANN A. HEIN A. ROSENBERG M. BOGHARDT E.-M. HANEBUTT-BENZ H. HALBEY 《Archaeometry》1996,38(2):347-357
Non-destructive X-ray fluorescence analyses induced by white synchrotron radiation (SYXRF) have been performed on a page of the Gutenberg Bible and 21 other different single leaves printed in the years 1470 to 1500. Absolute elemental areal densities for the papers and the inks are reported. The known high Cu and Pb content in Gutenberg's ink is confirmed. The elemental compositions of the other inks, if measurable by XRF at all, are in general very low, governed only by a few additional elements and found to be not distinctive for a known printer. This will render an identification of the printer or printing offices by ink composition analysis in the period after 1470 difficult. 相似文献
112.
113.
ABSTRACT. This paper uses new estimates of metropolitan factor demand and output supply functions to study how federal, state, and local fiscal policies affect metropolitan economies. We illustrate our work with findings for ten metropolitan areas in five states for changes in state corporate income taxes, local property taxes, the federal corporate income tax, an investment tax credit, interest rates, public capital stocks, output prices, and tax and regulatory policies affecting gross wages. It is clear from these simulations that a policy that is nominally the same everywhere will have repercussions that vary widely across regions and cities. 相似文献
114.
115.
M. H. Suryanarayana 《Development and change》1997,28(4):771-789
Although assessments by conventional macro measures show considerable improvement in food security in India, the levels of cereal consumption and calorie intake of even the general population are still below the normative threshold limits. This article brings out the dynamics of changes in institutional and production conditions and their implications for consumption patterns and food security at the micro level. The article uses empirical evidence to raise a number of issues, and calls for emphasis on investment in human capital by way of improvements in food and calorie intake for efficiency and economic growth. 相似文献
116.
117.
Human population groups and the distribution of lithic arrowheads in the Arabian Gulf 总被引:2,自引:1,他引:1
RICHARD H. SPOOR 《Arabian Archaeology and Epigraphy》1997,8(2):143-160
The distribution of lithic implements in the Arabian Gulf suggests two regions, each using a specific set of tools. It is argued here that this distinct pattern is the result of relations on various levels between several human population groups and not solely of ecological adaptions. Consequently, these contacts between indigenous groups might be held responsible, among others, for distributing goods, like'Ubaid pottery, initially brought along by Mesopotamian visitors from the Central Gulf down to the Lower Gulf. 相似文献
118.
The idea that there are certain "laws" of learning (similarity, contrast, contiguity) can be traced to Aristotle. He maintained that external stimuli cause small movements in the vessels to the dominant heart, the vestiges of which can be linked to one another. Aristotle's laws of learning were incorporated into the writings of Hobbes, Locke, and Berkeley, men who said nothing about the physiological correlates of mental associations. This left the door open for David Hartley to combine mental associationism with the Newtonian idea that sensations can cause minute particle vibrations in the nerves. Hartley's amalgam of psychology, philosophy, and neurology was first presented in 1746, as a "trial balloon" at the end a little-known monograph on a treatment for kidney stones. It was repeated three years later in his better-known Observations on Man. In many ways, modern psychobiological connectionism can be traced back to Hartley's Conjectures of 1746, in which Aristotle's original thoughts were modified with then current ideas about functions of the mind and the nervous system. 相似文献
119.
This paper describes the use of electron spin resonance spectroscopy to estimate the degree of heating of quartzite cobbles from hearths on the floor of the archaeological remains of an eighteenth-century Dutch colonial slave lodge. A novel technique based on the comparison of line intensities for the E’and O-2 centres in quartz distinguished successfully between cobbles which had been heated to estimated temperatures ranging from 300 °C to 450° C and controls from an adjacent stream bed. This inexpensive and simple technique could be applied to a wide range of archaeological problems involving the thermal history of objects consisting of or containing quartz. 相似文献
120.