全文获取类型
收费全文 | 42776篇 |
免费 | 3668篇 |
国内免费 | 1366篇 |
出版年
2024年 | 72篇 |
2023年 | 641篇 |
2022年 | 676篇 |
2021年 | 1490篇 |
2020年 | 1696篇 |
2019年 | 2080篇 |
2018年 | 1812篇 |
2017年 | 1235篇 |
2016年 | 1207篇 |
2015年 | 1574篇 |
2014年 | 2595篇 |
2013年 | 2935篇 |
2012年 | 1659篇 |
2011年 | 2127篇 |
2010年 | 1525篇 |
2009年 | 1936篇 |
2008年 | 2034篇 |
2007年 | 2012篇 |
2006年 | 1932篇 |
2005年 | 1682篇 |
2004年 | 1458篇 |
2003年 | 1219篇 |
2002年 | 1071篇 |
2001年 | 799篇 |
2000年 | 718篇 |
1999年 | 566篇 |
1998年 | 624篇 |
1997年 | 603篇 |
1996年 | 637篇 |
1995年 | 602篇 |
1994年 | 594篇 |
1993年 | 535篇 |
1992年 | 547篇 |
1991年 | 475篇 |
1990年 | 457篇 |
1989年 | 393篇 |
1988年 | 348篇 |
1987年 | 348篇 |
1986年 | 293篇 |
1985年 | 355篇 |
1984年 | 347篇 |
1983年 | 195篇 |
1982年 | 311篇 |
1981年 | 250篇 |
1980年 | 203篇 |
1979年 | 198篇 |
1978年 | 138篇 |
1977年 | 124篇 |
1976年 | 113篇 |
1973年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
91.
92.
The assembly of high voltage-activated Ca2+ channels with different β subunits influences channel properties and possibly subcellular targeting. We studied β subunit expression in the somata and axon terminals of the magnocellular neurosecretory cells, which are located in the supraoptic nucleus (SON) and neurohypophysis, respectively. Antibodies directed against the 4 CaVβ subunits (CaVβ1-CaVβ4) were used for immunoblots and for immunostaining of slices of these two tissues. We found that all 4 β subunits are expressed in both locations, but that CaVβ2 had the highest relative expression in the neurohypophysis. These data suggest that the CaVβ2 subunit is selectively targeted to axon terminals and may play a role in targeting and/or regulating the properties of Ca2+ channels. 相似文献
93.
94.
95.
96.
Adaptation to salinity at the plant cell level 总被引:3,自引:0,他引:3
H. R. Lerner 《Plant and Soil》1985,89(1-3):3-14
Summary Various mechanisms of adaptation of plant cells to salinity are reviewed: (1) protection of enzymes and maintenance of turgor by organic solutes; (2) prevention of ion toxicity by compartmentation; and (3) energization of solute transport by the proton pump. All these mechanisms seem to play a role in adaptation. The particular advantages of using salt-adapted cells in suspension culture to identify mechanisms of adaptation are pointed out. 相似文献
97.
98.
G E Brown S A Fischkoff J V Ordonez 《Biochemical and biophysical research communications》1984,123(3):937-943
The ability of a myeloid leukemia cell line (HL-60) to undergo membrane electrical potential changes was followed during neutrophilic differentiation induced by 2 compounds. Membrane-potential changes were induced with 12-O-tetradecanoylphorbol 13-acetate (TPA) or formyl-methionyl-leucyl-phenylalanine (FMLP) and were monitored by flow cytometry. The magnitude of the membrane-potential response to TPA increased in a more uniform manner as the population of cells matured than did acquisition of mature morphology or ability to undergo the respiratory burst in response to TPA. The response to TPA and FMLP of HL-60 cells, maximally induced to differentiate by dimethylsulfoxide, closely resembled that of neutrophils. Thus, HL-60 cells may be a useful tool in the study of the relation between membrane depolarization and subsequent cellular activation. 相似文献
99.
Summary During the course of sea urchin development, from early blastula to pluteus larva, there are two major visible processes toward which all activities seem to be focused. They are the differentiation of the larval skeleton by the primary mesenchyme cells and the differentiation of the primitive gut by the secondary mesenchyme cells. These activities take place within the shell-like layer of epithelial cells, or ectodermal wall. The interactive role of the ectodermal wall with the mesenchyme cells is not yet clearly understood. A number of earlier studies have proposed that the ectoderm may have an inductive influence on the mesenchyme cells and that its inner surface forms a molecular template for guiding the mesenchyme cells. In this report, we suggest an additional role for the ectodermal wall. We show that some primary mesenchyme cells and secondary mesenchyme cells insert between the cells of the ectodermal wall in order to firmly anchor the anlage of the larval skeleton and primitive gut during differentiation. This mechanism may provide a physical basis for maintaining the stable positional relationship of the anlage during development. 相似文献
100.