全文获取类型
收费全文 | 38235篇 |
免费 | 3705篇 |
国内免费 | 22篇 |
出版年
2023年 | 182篇 |
2022年 | 404篇 |
2021年 | 854篇 |
2020年 | 454篇 |
2019年 | 617篇 |
2018年 | 710篇 |
2017年 | 602篇 |
2016年 | 1055篇 |
2015年 | 1802篇 |
2014年 | 1904篇 |
2013年 | 2239篇 |
2012年 | 2934篇 |
2011年 | 2989篇 |
2010年 | 1839篇 |
2009年 | 1534篇 |
2008年 | 2296篇 |
2007年 | 2252篇 |
2006年 | 2195篇 |
2005年 | 1856篇 |
2004年 | 1890篇 |
2003年 | 1668篇 |
2002年 | 1637篇 |
2001年 | 502篇 |
2000年 | 387篇 |
1999年 | 415篇 |
1998年 | 383篇 |
1997年 | 321篇 |
1996年 | 290篇 |
1995年 | 250篇 |
1994年 | 221篇 |
1993年 | 230篇 |
1992年 | 250篇 |
1991年 | 267篇 |
1990年 | 237篇 |
1989年 | 243篇 |
1988年 | 209篇 |
1987年 | 196篇 |
1986年 | 183篇 |
1985年 | 237篇 |
1984年 | 228篇 |
1983年 | 191篇 |
1982年 | 232篇 |
1981年 | 259篇 |
1980年 | 206篇 |
1979年 | 167篇 |
1978年 | 130篇 |
1977年 | 133篇 |
1976年 | 141篇 |
1975年 | 119篇 |
1974年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
New techniques for enzymatic dissociation of mammalian tastecells allowed us to study, for the first time, the morphologyof murine taste receptor cells using high resolution scanningelectron microscopy. Cell shape varied from spindle to bipolarto lamellar, similar to shapes previously described in cellsfrom amphibian taste buds. Cell length varied from 19 to 65µm (39 ± 19 µm), with width averaging 6 ±3.4 µm. A rare picture of the apical microvilli of a tastereceptor cell, and a view of microvilli within a taste pore,suggest that at any given time, five to eight taste cells maybe exposed to the oral cavity. Assuming a cell life-span of10 days, and 50 cells per bud, all of which eventually reachthe taste pore, one can calculate that the average cell is exposedto the oral environment for 相似文献
54.
Andrew Porter 《BMJ (Clinical research ed.)》1981,283(6293):725-726
55.
Andrew W. Saxe Ji-Won Yoon Phillip Gorden Murray F. Brennan 《In vitro cellular & developmental biology. Plant》1982,18(10):884-890
Summary Dispersed cells from both fresh and cryopreserved human insulinoma have been maintained in cell culture. Initial yield of
viable cells was 50% for fresh and 25% for cryopreserved tissue. Viability of cells in culture was documented by increasing
numbers of cells (doubling time approximately 5 d initially and 2 d at the sixth subculture for both fresh and cryopreserved
tissue) and continued release of insulin over time (approximately 100 ng/ml per 105 cells at 10 d and 175 ng/ml per 105 cells at 30 d of culture for both fresh and cryopreserved tissue). Evidence that cells growing in culture were beta cells
was provided by: (a) recovery of intracellular and extracellular immunoreactive insulin (IRI), (b) electron microscopic morphology,
and (c) immunohistochemical staining. Cells from fresh insulinoma incubated with increasing concentrations of extracellular
glucose released increasing amounts of IRI up to approximately 15 mM glucose, which paralleled changes in plasma insulin obtained during a preoperative glucose tolerance test.
Under an Intergovernmental Personnel Act Exchange from the Department of Surgery, University of California, Davis, Sacramento
Medical Center. 相似文献
56.
R. Robinson 《BMJ (Clinical research ed.)》1989,298(6676):819-821
57.
John M. Robinson Sylvia A. Larrimore David W. Craft H.E. Heath Gary L. Sloan 《Biochemical and biophysical research communications》1982,109(3):730-737
The extracellular protease, endopeptidase, and hexosaminidase produced by were neither induced nor repressed by amino acids but required a tryptic digest of casein for their production. Catabolite repression of exoenzyme production by glucose was not affected by exogenous cyclic adenosine 3′, 5′-monophosphate but was partially relieved by di- or monobutyryl derivatives of this compound. 相似文献
58.
59.
60.
Thomas Bell Michael B. Bonsall Angus Buckling Andrew S. Whiteley Timothy Goodall Robert I. Griffiths 《Biology letters》2010,6(5):639-642
Productivity and predation are thought to be crucial drivers of bacterial diversity. We tested how the productivity–diversity of a natural bacterial community is modified by the presence of protist predators with different feeding preferences. In the absence of predators, there was a unimodal relationship between bacterial diversity and productivity. We found that three protist species (Bodo, Spumella and Cyclidium) had widely divergent effects on bacterial diversity across the productivity gradient. Bodo and Cyclidium had little effect on the shape of the productivity–diversity gradient, while Spumella flattened the relationship. We explain these results in terms of the feeding preferences of these predators. 相似文献