全文获取类型
收费全文 | 65685篇 |
免费 | 18995篇 |
国内免费 | 9300篇 |
出版年
2024年 | 118篇 |
2023年 | 738篇 |
2022年 | 1230篇 |
2021年 | 2712篇 |
2020年 | 3975篇 |
2019年 | 5708篇 |
2018年 | 5420篇 |
2017年 | 5487篇 |
2016年 | 5849篇 |
2015年 | 6491篇 |
2014年 | 6820篇 |
2013年 | 7323篇 |
2012年 | 5688篇 |
2011年 | 5084篇 |
2010年 | 5452篇 |
2009年 | 4118篇 |
2008年 | 3335篇 |
2007年 | 2649篇 |
2006年 | 2417篇 |
2005年 | 2172篇 |
2004年 | 1823篇 |
2003年 | 1589篇 |
2002年 | 1416篇 |
2001年 | 1237篇 |
2000年 | 1091篇 |
1999年 | 816篇 |
1998年 | 428篇 |
1997年 | 368篇 |
1996年 | 337篇 |
1995年 | 322篇 |
1994年 | 268篇 |
1993年 | 206篇 |
1992年 | 247篇 |
1991年 | 196篇 |
1990年 | 182篇 |
1989年 | 145篇 |
1988年 | 106篇 |
1987年 | 83篇 |
1986年 | 72篇 |
1985年 | 73篇 |
1984年 | 49篇 |
1983年 | 41篇 |
1982年 | 48篇 |
1981年 | 21篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1950年 | 8篇 |
1873年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 875 毫秒
111.
Q Yuan W M Jiang D Hollander E Leung J D Watson G W Krissansen 《Biochemical and biophysical research communications》1991,176(3):1443-1449
A cDNA clone encoding the N-terminal sequence of the murine integrin beta 7 subunit, a novel member of the leukocyte cell adhesion molecule subset (Leu-CAM), has been isolated. An N-terminal region of 13 contiguous amino acids deduced from the cDNA shows complete identity with the N-terminus of the 120 kDa subunit of the M290 antigen, a surface molecule found highly expressed on mouse intestinal intraepithelial lymphocytes (IEL). This unexpected result focuses two previously unconnected areas of research and suggests that integrins may have a special role to play in the defence of the gut mucosa. 相似文献
112.
After observing specimens of Calligonum pumilum Losinsk. and C. juochiangense Y. X. Liou in both the field and in herbarium collections, it was found that the morphological characters of these two species are quite different, especially with respect of the twisted direction of fruit ribs, number of bristle rows along each rib, rigidity and degree of interweaving of bristles, as well as their geographic distribution. Therefore, it is concluded that C. pumilum and C. juochiangense should be accepted as two independent species. 相似文献
113.
114.
Yao Chen Jie Zhu Jun Mo Hongyu Yang Xueyang Jiang Hongzhi Lin 《Journal of enzyme inhibition and medicinal chemistry》2018,33(1):290-302
Small molecule cholinesterases inhibitor (ChEI) provides an effective therapeutic strategy to treat Alzheimer’s disease (AD). Currently, the discovery of new ChEI with multi-target effect is still of great importance. Herein, we report the synthesis, structure–activity relationship study and biological evaluation of a series of tacrine-cinnamic acid hybrids as new ChEIs. All target compounds are evaluated for their in vitro cholinesterase inhibitory activities. The representatives which show potent activity on cholinesterase, are evaluated for the amyloid β-protein self-aggregation inhibition and in vivo assays. The optimal compound 19, 27, and 30 (human AChE IC50?=?10.2?±?1.2, 16.5?±?1.7, and 15.3?±?1.8?nM, respectively) show good performance in ameliorating the scopolamine-induced cognition impairment and preliminary safety in hepatotoxicity evaluation. These compounds deserve further evaluation for the development of new therapeutic agents against AD. 相似文献
115.
116.
T. RIGOT M. VERCAUTEREN DRUBBEL J.‐C. DELÉCOLLE M. GILBERT 《Medical and veterinary entomology》2013,27(1):29-38
The spatial epidemiology of Bluetongue virus (BTV) at the landscape level relates to the fine‐scale distribution and dispersal capacities of its vectors, midges belonging to the genus Culicoides Latreille (Diptera: Ceratopogonidae). Although many previous researches have carried out Culicoides sampling on farms, little is known of the fine‐scale distribution of Culicoides in the landscape immediately surrounding farms. The aim of this study was to gain a better understanding of Culicoides populations at increasing distances from typical dairy farms in north‐west Europe, through the use of eight Onderstepoort‐type black‐light traps positioned along linear transects departing from farms, going through pastures and entering woodlands. A total of 16 902 Culicoides were collected in autumn 2008 and spring 2009. The majority were females, of which more than 97% were recognized as potential vectors. In pastures, we found decreasing numbers of female Culicoides as a function of the distance to the farm. This pattern was modelled by leptokurtic models, with parameters depending on season and species. By contrast, the low number of male Culicoides caught were homogeneously distributed along the transects. When transects entered woodlands, we found a higher abundance of Culicoides than expected considering the distance of the sampling sites to the farm, although this varied according to species. 相似文献
117.
118.
119.
120.