全文获取类型
收费全文 | 16074篇 |
免费 | 801篇 |
国内免费 | 21篇 |
出版年
2023年 | 111篇 |
2022年 | 276篇 |
2021年 | 428篇 |
2020年 | 252篇 |
2019年 | 259篇 |
2018年 | 402篇 |
2017年 | 431篇 |
2016年 | 501篇 |
2015年 | 683篇 |
2014年 | 756篇 |
2013年 | 1045篇 |
2012年 | 1162篇 |
2011年 | 1051篇 |
2010年 | 633篇 |
2009年 | 575篇 |
2008年 | 668篇 |
2007年 | 658篇 |
2006年 | 573篇 |
2005年 | 482篇 |
2004年 | 453篇 |
2003年 | 381篇 |
2002年 | 349篇 |
2001年 | 334篇 |
2000年 | 305篇 |
1999年 | 244篇 |
1998年 | 125篇 |
1997年 | 106篇 |
1996年 | 96篇 |
1995年 | 112篇 |
1994年 | 101篇 |
1993年 | 95篇 |
1992年 | 221篇 |
1991年 | 206篇 |
1990年 | 200篇 |
1989年 | 193篇 |
1988年 | 168篇 |
1987年 | 164篇 |
1986年 | 148篇 |
1985年 | 174篇 |
1984年 | 167篇 |
1983年 | 115篇 |
1982年 | 112篇 |
1981年 | 99篇 |
1980年 | 92篇 |
1979年 | 147篇 |
1978年 | 109篇 |
1977年 | 95篇 |
1974年 | 118篇 |
1973年 | 91篇 |
1972年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
911.
Sudhir K. Singh 《Molecular simulation》2016,42(5):413-419
We report the effect of surface-screening parameter of Yukawa potential model on vapour–liquid phase coexistence and critical-point properties of slit–pore-confined Yukawa fluid, using grand canonical transition-matrix Monte Carlo along with the histogram reweighting method. The effect of surface-screening parameter on the vapour–phase coexistence density is insignificant for the studied system. On the other hand, significant effect of surface-screening parameter is observed on liquid phase coexistence density. With increasing surface-screening parameter, liquid phase coexistence density decreases. Critical-point properties have shown monotonic decreasing trends with increase in surface-screening parameter. Moreover, the effect of change of surface-screening parameter is least on critical temperature changes as compared to critical density and critical pressure changes for the studied Yukawa system in this work. 相似文献
912.
913.
914.
915.
916.
917.
Crows (Corvus splendens) and white herons (Ardea alba) inhabit the agricultural landscapes nearby human habitats which represent dynamic ecosystem and show seasonal crop patterns. We studied the movement pattern in these birds at dawn and dusk, during solstices (December and June) and equinoxes (March and September). The movement directions were changed from uniform at dawn to a concentrated distribution at dusk all along the season suggesting that morning movements are more exploratory than evening with seasonal differences. Differential use of directions in December than June could be the effect of temperature, food availability or wind direction and speed. During breeding, less number of directions used suggests that birds might be moving towards the directions having high probability of food availability. It is likely that avian dispersal in space and time is dependent on the food availability however, further studies are required to be carried out. 相似文献
918.
919.
Sheel V. Singh Nicky Staes Elaine E. Guevara Steven J. Schapiro John J. Ely William D. Hopkins Chet C. Sherwood Brenda J. Bradley 《Genes, Brain & Behavior》2019,18(7)
Studying genetic mechanisms underlying primate brain morphology can provide insight into the evolution of human brain structure and cognition. In humans, loss‐of‐function mutations in the gene coding for ASPM (Abnormal Spindle Microtubule Assembly) have been associated with primary microcephaly, which is defined by a significantly reduced brain volume, intellectual disability and delayed development. However, less is known about the effects of common ASPM variation in humans and other primates. In this study, we characterized the degree of coding variation at ASPM in a large sample of chimpanzees (N = 241), and examined potential associations between genotype and various measures of brain morphology. We identified and genotyped five non‐synonymous polymorphisms in exons 3 (V588G), 18 (Q2772K, K2796E, C2811Y) and 27 (I3427V). Using T1‐weighted magnetic resonance imaging of brains, we measured total brain volume, cerebral gray and white matter volume, cerebral ventricular volume, and cortical surface area in the same chimpanzees. We found a potential association between ASPM V588G genotype and cerebral ventricular volume but not with the other measures. Additionally, we found that chimpanzee, bonobo, and human lineages each independently show a signature of accelerated ASPM protein evolution. Overall, our results suggest the potential effects of ASPM variation on cerebral cortical development, and emphasize the need for further functional studies. These results are the first evidence suggesting ASPM variation might play a role in shaping natural variation in brain structure in nonhuman primates. 相似文献
920.
Zafar Rukhsar Chauhan Pooja Salim Mohammad Singh Ghanshyam 《Plasmonics (Norwell, Mass.)》2019,14(4):1013-1017
Plasmonics - Photonics provides a key solution to limit the myriads of challenges offered by existing silicon technology. Here, we propose a simple 2-channel Plasmonic demultiplexer with... 相似文献