全文获取类型
收费全文 | 5521篇 |
免费 | 537篇 |
国内免费 | 117篇 |
专业分类
6175篇 |
出版年
2023年 | 45篇 |
2022年 | 94篇 |
2021年 | 171篇 |
2020年 | 101篇 |
2019年 | 119篇 |
2018年 | 131篇 |
2017年 | 92篇 |
2016年 | 161篇 |
2015年 | 316篇 |
2014年 | 333篇 |
2013年 | 401篇 |
2012年 | 484篇 |
2011年 | 431篇 |
2010年 | 250篇 |
2009年 | 207篇 |
2008年 | 307篇 |
2007年 | 248篇 |
2006年 | 243篇 |
2005年 | 228篇 |
2004年 | 199篇 |
2003年 | 171篇 |
2002年 | 167篇 |
2001年 | 107篇 |
2000年 | 121篇 |
1999年 | 108篇 |
1998年 | 64篇 |
1997年 | 49篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 43篇 |
1993年 | 41篇 |
1992年 | 70篇 |
1991年 | 57篇 |
1990年 | 45篇 |
1989年 | 55篇 |
1988年 | 50篇 |
1987年 | 35篇 |
1986年 | 39篇 |
1985年 | 30篇 |
1984年 | 50篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 27篇 |
1978年 | 24篇 |
1977年 | 20篇 |
1975年 | 16篇 |
1974年 | 9篇 |
1971年 | 11篇 |
排序方式: 共有6175条查询结果,搜索用时 15 毫秒
11.
An analysis of the unconfined compression of articular cartilage 总被引:7,自引:0,他引:7
Analytical solutions have been obtained for the internal deformation and fluid-flow fields and the externally observable creep, stress relaxation, and constant strain-rate behaviors which occur during the unconfined compression of a cylindrical specimen of a fluid-filled, porous, elastic solid, such as articular cartilage, between smooth, impermeable plates. Instantaneously, the "biphasic" continuum deforms without change in volume and behaves like an incompressible elastic solid of the same shear modulus. Radial fluid flow then allows the internal fluid pressure to equilibrate with the external environment. The equilibrium response is controlled by the Young's modulus and Poisson's ratio of the solid matrix. 相似文献
12.
A Marongiu P Nuvole P Lai F Sau G Bomboi P Bini 《Bollettino della Società italiana di biologia sperimentale》1984,60(2):307-311
It has been studied the total plasma cholesterol rate in lactating or dry sheep and goats of Sardinian breed. The values obtained for the four different groups of subjects have been compared with the "t of Student". While the difference between the sheep groups has seemed very accentuated, it has appeared hardly significant between the goat groups. Highly significant difference has also been found between lactating sheep and goats whereas there was no significant difference among the groups of dry subjects. 相似文献
13.
14.
This paper reviews the systematic status and geographical distribution of 30 odd species of freshwater calanoid copepods in Southeast Asia. Three regions are delineated based on the diversity and abundance of these organisms; Region I being the Southasiatic element, Region II the attenuated belt of copepods and Region III rich in endemic species. The implication of a north-south diminishing of copepod species to inland fisheries is postulated. 相似文献
15.
16.
A double-stranded ribonucleic acid (dsRNA) was isolated from coremial extracts of wild type P. claviforme, by methylated-albumin kieselguhr chromatography. Differential centrifugations of the coremial extracts from WT and Sh mutant strains yielded two classes of virus-like particles (VLP), of dimensions 25-30 nm, and 50-70 nm. The possible ecological significance of fungal viruses is discussed. 相似文献
17.
18.
Due to resource scarcity and environmental degradation, a new development concept emphasizing environmental concerns, called the circular economy (CE), has been enacted in legislation in China. This environmental management concept can be implemented at three levels, namely, region, industrial zone, and individual enterprise, with the objective of boosting economic development while lessening environmental and resource challenges. Environmental supply chain cooperation (ESCC), an approach that utilizes customer and supplier cooperation in environmental management, has been initiated among Chinese enterprises. Using survey data collected from 396 Chinese manufacturers, we examine the role of ESCC practices in influencing the relationship between implementing CE practices and the achievement of performance outcomes by testing the moderation and mediation effects of ESCC practices on the CE practice‐performance relationship through hierarchical regression analysis. Our data analyses indicate that ESCC practices are useful by moderation and, in some cases, essential by mediation, for Chinese manufacturers seeking to realize the performance targets desired in CE practices. The results highlight the need for Chinese manufacturers to improve supply chain coordination in their implementation of CE. On the policy side, our research findings suggest that ESCC practices are beneficial and, in some cases, necessary for the development of CE in China. 相似文献
19.
目的:观察鲍肤索对血管性痴呆大鼠学习与记忆能力的干预及机制。方法:制备生物鲍肤索,分剂量喂饲血管性痴呆大鼠,测试学习与记忆能力、红细胞和血红蛋白。结果:鲍肤素提高大鼠Y型迷宫测试的分值和红细胞、血红蛋白水平。结论:鲍肤素能提高血管性痴呆大鼠的学习与记忆能力和红细胞、血红蛋白水平。 相似文献
20.