全文获取类型
收费全文 | 27103篇 |
免费 | 2767篇 |
国内免费 | 12篇 |
出版年
2021年 | 742篇 |
2020年 | 369篇 |
2019年 | 444篇 |
2018年 | 522篇 |
2017年 | 473篇 |
2016年 | 806篇 |
2015年 | 1272篇 |
2014年 | 1370篇 |
2013年 | 1638篇 |
2012年 | 1968篇 |
2011年 | 1921篇 |
2010年 | 1178篇 |
2009年 | 945篇 |
2008年 | 1334篇 |
2007年 | 1369篇 |
2006年 | 1277篇 |
2005年 | 1130篇 |
2004年 | 1042篇 |
2003年 | 920篇 |
2002年 | 921篇 |
2001年 | 501篇 |
2000年 | 454篇 |
1999年 | 422篇 |
1998年 | 268篇 |
1997年 | 200篇 |
1996年 | 209篇 |
1995年 | 156篇 |
1994年 | 190篇 |
1993年 | 173篇 |
1992年 | 285篇 |
1991年 | 267篇 |
1990年 | 274篇 |
1989年 | 246篇 |
1988年 | 232篇 |
1987年 | 259篇 |
1986年 | 195篇 |
1985年 | 228篇 |
1984年 | 208篇 |
1983年 | 192篇 |
1982年 | 158篇 |
1981年 | 145篇 |
1980年 | 138篇 |
1979年 | 190篇 |
1978年 | 183篇 |
1977年 | 142篇 |
1976年 | 135篇 |
1975年 | 148篇 |
1974年 | 155篇 |
1973年 | 138篇 |
1972年 | 153篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
Wendy A. Douglass Robert H. Hyland Christopher D. Buckley Aymen Al-Shamkhani Jacqueline M. Shaw Sarah L. Scarth David L. Simmons S.K.Alex Law 《FEBS letters》1998,440(3):125
The cysteine-rich region (CRR) of the β2 integrin subunit was replaced by that of β1 to give the chimera β2NV1. β2NV1 can combine with αL to form a variant leukocyte-function-associated antigen (LFA)-1 on COS cell surface, suggesting that the specificity of the β2 interaction with αL does not lie in the CRR. Unlike those expressing wild-type LFA-1, COS cells expressing αLβ2NV1 are constitutively active in intercellular adhesion molecule (ICAM)-1 adhesion. These results suggest that activation of LFA-1 involves the release of an intramolecular constraint, which is maintained, in part, by the authentic β2 CRR. 相似文献
2.
3.
4.
Frank J. Turano Kenneth Glade Wilson 《In vitro cellular & developmental biology. Plant》1985,21(3):135-139
Summary The feasibility of using plant cell culture to measure toxicity was determined by investigating the toxicological effects
of three chemical compounds, allyl alcohol, propargylglycine, and cadmium chloride, on cell cultures ofCatharanthus roseus G. Don (Madagascar periwinkle). Suspension cultures ofC. roseus were maintained in modified B5 medium and transferred every 5 d. Five-day-old cell cultures were exposed to various concentrations
(10,3,1,0.3,0.1,0.03,0.01,0.003,0.001,0.0003,0.0001, 0.00003, and 0.0 mM) of the toxicants in both acute and chronic toxicity tests.
In the acute test, cells were exposed to the toxicant for 24 h, washed three times with sterile medium, and plated in petri
plates with an equal volume of 1.4% agar medium. Cells in the chronic test were plated with an equal volume of 1.4% agar medium
containing various concentrations of the toxicant. Cells were incubated 28 d at 30°C in the dark. The colonies were counted
and the results plotted as percent survival versus toxicant concentration. The results indicate, at the concentrations tested,
thatC. roseus assay may be feasible in that it fulfills the criteria for a practical assay (e.g., rapid, simple, quantifiable, and reproducible).
This work was submitted to the faculty of Miami University in partial fulfillment of the requirements for the degree of Master
of Environmental Science, Institute of Environmental Sciences. 相似文献
5.
J. Bastow Wilson 《植被学杂志》2007,18(3):451-452
The recent Forum contribution by Grime (2006) contrasts the MacArthur/Diamond assembly‐rule approach to studying plant communities with the study of environmental trait gradients. Both are valid and useful. In doing so, Grime declares that the assembly rules model, in which negative interactions between plants act with limiting similarity to cause local trait divergence, is “not supported by empirical study of plant communities”. This is, he says, the agony of community ecology. I show that there is now abundant evidence for assembly rules, and no agony. 相似文献
6.
Diego Sustaita Patty Finfrock Quickert Laura Patterson Laureen Barthman-Thompson Sarah Estrella 《The Journal of wildlife management》2011,75(6):1498-1507
We undertook a 2-year (2002–2004) mark–recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. © 2011 The Wildlife Society. 相似文献
7.
8.
The localization of latent brain hexokinase on synaptosomal mitochondria 总被引:10,自引:0,他引:10
J E Wilson 《Archives of biochemistry and biophysics》1972,150(1):96-104
9.
10.