全文获取类型
收费全文 | 6533篇 |
免费 | 608篇 |
国内免费 | 2篇 |
出版年
2022年 | 60篇 |
2021年 | 128篇 |
2020年 | 68篇 |
2019年 | 71篇 |
2018年 | 80篇 |
2017年 | 67篇 |
2016年 | 141篇 |
2015年 | 283篇 |
2014年 | 278篇 |
2013年 | 411篇 |
2012年 | 510篇 |
2011年 | 475篇 |
2010年 | 273篇 |
2009年 | 225篇 |
2008年 | 403篇 |
2007年 | 404篇 |
2006年 | 347篇 |
2005年 | 292篇 |
2004年 | 293篇 |
2003年 | 293篇 |
2002年 | 289篇 |
2001年 | 79篇 |
2000年 | 55篇 |
1999年 | 71篇 |
1998年 | 92篇 |
1997年 | 58篇 |
1996年 | 55篇 |
1995年 | 51篇 |
1994年 | 58篇 |
1993年 | 49篇 |
1992年 | 47篇 |
1991年 | 40篇 |
1990年 | 56篇 |
1989年 | 40篇 |
1988年 | 46篇 |
1987年 | 29篇 |
1986年 | 38篇 |
1985年 | 43篇 |
1984年 | 45篇 |
1983年 | 44篇 |
1982年 | 49篇 |
1981年 | 45篇 |
1980年 | 34篇 |
1978年 | 27篇 |
1977年 | 28篇 |
1976年 | 40篇 |
1975年 | 33篇 |
1974年 | 31篇 |
1973年 | 29篇 |
1972年 | 29篇 |
排序方式: 共有7143条查询结果,搜索用时 15 毫秒
11.
Replacement of ~100 mM of sodium chloride in the extracellular medium of quiescent hamster fibroblasts (Nil 8 and BHK cells) by potassium chloride causes an increase in the rate of uridine uptake. This increase is identical with that achieved by addition of 10% serum to the same cultures. The effects of serum and KCl are not additive. The dependence of the rate of uridine uptake on extracellular KCl concentration is of a sigmoid nature. The time course of the activation process is similar to that of serum activation of uridine uptake in the same cells. The high rate of uridine uptake persists for at least 30 min after return to an extracellular medium containing a high concentration of sodium. 相似文献
12.
Ruth Holland 《BMJ (Clinical research ed.)》1986,293(6553):1010
13.
14.
D A Keire P Anton K F Faull E Ruth J H Walsh P Chew D Quisimoro M Territo J R Reeve 《The Journal of biological chemistry》2001,276(52):48847-48853
The structure of a small-molecule, non-peptide chemotactic factor has been determined from activity purified to apparent homogeneity from Helicobacter pylori supernatants. H. pylori was grown in brucella broth media until one liter of solution had 0.9 absorbance units. The culture was centrifuged, and the bacteria re-suspended in physiological saline and incubated at 37 degrees C for 4 h. A monocyte migration bioassay revealed the presence of a single active chemotactic factor in the supernatant from this incubation. The chemotactic factor was concentrated by solid phase chromatography and purified by reverse phase high pressure liquid chromatography. The factor was shown to be indistinguishable from diethyl phthalate (DEP) on the basis of multiple criteria including nuclear magnetic resonance spectroscopy, electron impact mass spectroscopy, UV visible absorption spectrometry, GC and high pressure liquid chromatography retention times, and chemotactic activity toward monocytes. Control experiments with incubated culture media without detectable bacteria did not yield detectable DEP, suggesting it is bacterially derived. It is not known if the bacteria produce diethyl phthalate de novo or if it is a metabolic product of a precursor molecule present in culture media. DEP produced by H. pylori in addition to DEP present in man-made products may contribute to the high levels of DEP metabolites observed in human urine. DEP represents a new class of chemotactic factor. 相似文献
15.
Paola A Gilardoni Stefan Schuck Ruth Jüngling Björn Rotter Ian T Baldwin Gustavo Bonaventure 《BMC plant biology》2010,10(1):66
Background
Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown. 相似文献16.
Reinhold Benesch Samuel Waxman Ruth Benesch Charles Baugh 《Biochemical and biophysical research communications》1982,106(4):1359-1363
Pteroyl polyglutamates bind to hemoglobin with an affinity which leaves only a minor fraction of red cell folate in the free state. This could serve as a regulating mechanism for protein synthesis in the differentiating erythroblast. 相似文献
17.
18.
19.
20.