全文获取类型
收费全文 | 40737篇 |
免费 | 3106篇 |
国内免费 | 2748篇 |
出版年
2024年 | 55篇 |
2023年 | 487篇 |
2022年 | 1093篇 |
2021年 | 2084篇 |
2020年 | 1401篇 |
2019年 | 1855篇 |
2018年 | 1733篇 |
2017年 | 1256篇 |
2016年 | 1871篇 |
2015年 | 2545篇 |
2014年 | 3049篇 |
2013年 | 3329篇 |
2012年 | 3712篇 |
2011年 | 3376篇 |
2010年 | 2002篇 |
2009年 | 1822篇 |
2008年 | 2155篇 |
2007年 | 1930篇 |
2006年 | 1606篇 |
2005年 | 1301篇 |
2004年 | 1099篇 |
2003年 | 1048篇 |
2002年 | 852篇 |
2001年 | 621篇 |
2000年 | 594篇 |
1999年 | 545篇 |
1998年 | 343篇 |
1997年 | 335篇 |
1996年 | 318篇 |
1995年 | 282篇 |
1994年 | 280篇 |
1993年 | 198篇 |
1992年 | 260篇 |
1991年 | 233篇 |
1990年 | 175篇 |
1989年 | 133篇 |
1988年 | 104篇 |
1987年 | 85篇 |
1986年 | 67篇 |
1985年 | 66篇 |
1984年 | 53篇 |
1983年 | 40篇 |
1982年 | 30篇 |
1981年 | 31篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
The functioning of the vertebrate eye depends on its absolute size, which is presumably adapted to specific needs. Eye size variation in lidless and spectacled colubrid snakes was investigated, including 839 specimens belonging to 49 genera, 66 species and subspecies. Variations of adult eye diameters (EDs) in both absolute and relative terms between species were correlated with parameters reflecting behavioral ecology. In absolute terms, eye of arboreal species was larger than in terrestrial and semiaquatic species. For diurnal species, EDs of terrestrial species do not differ from semiaquatic species; for nocturnal species the ED of terrestrial species is larger than fossorial species but not different from semiaquatic species. In relative terms, ED did not differ significantly by habitat for diurnal species. Although the ED of terrestrial species is larger than fossorial species there were no differences for nocturnal species between semiaquatic and fossorial snakes. In contrast to other vertebrates studied to date, colubrid EDs in absolute and relative terms are larger in diurnal than in nocturnal species. These observations suggest that among colubrid snakes, eye size variation reflects adaptation to specific habitats, foraging strategies and daily activities, independently of phylogeny. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc. 相似文献
4.
Xiao‐Juan Yu Xiao‐Ren Peng Tong‐Huan Li 《Journal of cellular and molecular medicine》2014,18(12):2530-2535
Many studies have examined the association between the FABP2 (rs1799883) Ala54Thr gene polymorphism and type 2 diabetes mellitus risk (T2DM) in various populations, but their results have been inconsistent. To assess this relationship more precisely, A HuGE review and meta‐analysis were performed. The PubMed and CNKI database was searched for case‐control studies published up to April 2014. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Ultimately, 13 studies, comprising 2020 T2DM cases and 2910 controls were included. Overall, for the Thr carriers (Ala/Thr and Thr/Thr) versus the wild‐type homozygotes (Ala/Ala), the pooled OR was 1.18 (95% CI = 1.04–1.34, P = 0.062 for heterogeneity), for Thr/Thr versus Ala/Ala the pooled OR was 1.17 (95% CI = 1.05–1.41 P = 0.087 for heterogeneity). In the stratified analysis by ethnicity, the significantly risks were found among Asians but not Caucasians. This meta‐analysis suggests that the FABP2 (rs1799883) Ala54Thr polymorphisms are associated with increased susceptibility to T2DM risk among Asians but not Caucasians. 相似文献
5.
6.
7.
Plant and Soil - To investigate the effects of polystyrene microplastics (PS-beads) on the soil properties, photosynthesis of Flowering Chinese cabbage, the rhizosphere microbial community and... 相似文献
8.
Yunfan Sun Liang Wu Yu Zhong Kaiqian Zhou Yong Hou Zifei Wang Zefan Zhang Jiarui Xie Chunqing Wang Dandan Chen Yaling Huang Xiaochan Wei Yinghong Shi Zhikun Zhao Yuehua Li Ziwei Guo Qichao Yu Liqin Xu Jia Fan 《Cell》2021,184(2):404-421.e16
- Download : Download high-res image (233KB)
- Download : Download full-size image
9.
10.