全文获取类型
收费全文 | 107478篇 |
免费 | 7311篇 |
国内免费 | 18篇 |
专业分类
114807篇 |
出版年
2023年 | 560篇 |
2022年 | 419篇 |
2021年 | 999篇 |
2020年 | 934篇 |
2019年 | 943篇 |
2018年 | 2591篇 |
2017年 | 2305篇 |
2016年 | 3224篇 |
2015年 | 4818篇 |
2014年 | 4908篇 |
2013年 | 6587篇 |
2012年 | 8084篇 |
2011年 | 7564篇 |
2010年 | 4822篇 |
2009年 | 3563篇 |
2008年 | 6241篇 |
2007年 | 6161篇 |
2006年 | 5646篇 |
2005年 | 5290篇 |
2004年 | 4937篇 |
2003年 | 4557篇 |
2002年 | 4194篇 |
2001年 | 2153篇 |
2000年 | 2129篇 |
1999年 | 1852篇 |
1998年 | 786篇 |
1997年 | 607篇 |
1996年 | 532篇 |
1995年 | 548篇 |
1994年 | 564篇 |
1993年 | 426篇 |
1992年 | 1244篇 |
1991年 | 1162篇 |
1990年 | 1025篇 |
1989年 | 954篇 |
1988年 | 895篇 |
1987年 | 761篇 |
1986年 | 692篇 |
1985年 | 771篇 |
1984年 | 670篇 |
1983年 | 559篇 |
1982年 | 438篇 |
1981年 | 424篇 |
1979年 | 575篇 |
1978年 | 444篇 |
1977年 | 395篇 |
1976年 | 385篇 |
1975年 | 431篇 |
1974年 | 452篇 |
1973年 | 458篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
932.
933.
Jacques Dornand Jean-Claude Bonnafous Jean Favero Agnés Gartner Jean-Claude Mani 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1984,804(4):398-403
It is now well established that human lymphoblastoid cell lines showing immaturity characters display ecto-5′-nucleotidase activities lower than normal levels. A recent paper (Sun, A.S., Holland, J.F. and Ohnuma, T. (1983) Biochim. Biophys. Acta 762, 577–584) mentioned that this phenomenon resulted from the presence of a 5′-nucleotidase inhibitor in these cell lines. We demonstrate here that the use of 5′-[3H]AMP as a substrate, and inadequate analysis of the products formed, led them to a misinterpretation. [3H]Adenosine derived from 5′-[3H]AMP hydrolysis was further transformed into [3H]inosine by the adenosine deaminase activity of the leukemic cell lines tested; [3H]inosine was precipitated with the excess substrate and was not taken into account in the ecto-5′-nucleotidase determination, which led the authors to confuse this adenosine deaminase activity with a 5′-nucleotidase inhibitor. We did not observe 5′-nucleotidase inhibition by leukemic cell cytosol when convenient assay methods were used and showed that the presence of such an inhibitor remains to be established. 相似文献
934.
935.
Protein kinase(s) in bovine brain coated vesicles 总被引:2,自引:0,他引:2
Purified bovine brain coated vesicles contain protein kinase activity which phosphorylates 165, 54 and 50 kDa protein substrates. These phosphorylations do not seem to be induced by a unique protein kinase: indeed, the three substrates present different localizations in coated vesicles, the phosphorylation sites are either serine or threonine residues and vanadate and ATP[gamma S] have different effects on 32P incorporation in the substrates. Comparison of the coated vesicle protein and phosphorylation patterns from different tissues and animal origins shows that only the 50 kDa protein phosphorylation is always observed, compared to the great diversity in other minor phosphorylations which are observed or not in the various coated vesicles. The possible presence of a 50 kDa phosphoprotein phosphatase is also discussed. It is suggested that the 50 kDa protein with its connected specific kinase and phosphatase seems to constitute a regulatory system present in coated vesicles. 相似文献
936.
Influence of the conformational state on the isoelectric points of rat brain synaptosomes, mitochondria and mitoplasts 总被引:1,自引:0,他引:1
The isoelectric points of rat brain synaptosomes, mitochondria and mitoplasts have been determined by using different charged two-phase systems containing dextran and poly(ethylene glycol). The cross-partition diagrams of these organelles show isoelectric points at pH 4.1, 4.5 and 4.7, respectively. The influence of the conformational state of mitochondrial membranes upon their partition in two-phase systems has been studied. Shrunk mitoplasts showed a large change in their partition behavior as reflected by an increased affinity for the lower dextran phase, while shrinkage of mitochondria did not affect their partition. Shrunk mitoplasts showed the same isoelectric point of pH 4.7 as swollen mitoplasts, which indicates that no charge changes occurred on the outer side of the inner mitochondrial membrane during shrinkage of mitoplasts. 相似文献
937.
Periodic acid oxidation in methanol followed by incubation with 1, 1-dimethylhydrazine results in release of diacylglycerols from 1,2-diacyl-3-glycosyl-sn-glycerols. During hydrazinolysis of oxidized monogalactosyl diacylglycerol, an intermediate hydrazone derivative was observed which was isolated and identified. The diacylglycerols recovered are 1,2-diacyl isomers containing the same fatty acid mixtures as the intact glycolipids. The yields of diacylglycerols released from plant monogalactosyl-, digalactosyl-, and sulfoquinovosyl diacylglycerols were in the range of 30-50%. The method may be used for analysis of molecular species and for preparative purposes. 相似文献
938.
B D Nelson F Kabir J Kolarov K Luciaková S Kuzela N Latruffe M Lindén 《Archives of biochemistry and biophysics》1984,234(1):24-30
The contents of mitochondrial inner membrane protein complexes were compared in normal liver and in Zajdela hepatoma mitochondria by the immunotransfer technique. Antibodies against core proteins 1 and 2, cytochrome c1, the iron-sulfur protein of Complex III, subunits I and II of cytochrome oxidase, and the alpha and beta subunits of the F1-ATPase were used. In addition, antibodies against a primary dehydrogenase, beta-hydroxybutyrate dehydrogenase, as well as the outer membrane pore protein were used. The results indicate that the components of the cytochrome chain and porin are greatly enriched in hepatoma mitochondria compared to normal rat liver mitochondria. This enrichment was also reflected in the rates of respiration in tumor mitochondria using a variety of substrates. Enrichment of porin may partially account for increased hexokinase binding to tumor mitochondria. In contrast to the respiratory chain components, the F1-ATPase and F0 (measured by DCCD binding) were not increased in tumor mitochondria. Thus, Zajdela hepatoma mitochondria components are nonstoichiometric, being enriched in oxidative capacity but relatively deficient in ATP synthesizing capacity. Finally, beta-hydroxybutyrate dehydrogenase, which is often decreased in hepatoma mitochondria, was shown here by immunological methods to be decreased by only 40%, whereas enzyme activity was less than 5% of that in normal rat liver. 相似文献
939.
Studies on cultures of embryonic rat muscle cells have suggested that the presence of collagen-tailed forms may be correlated with spontaneous contractile activity: these forms disappear in the presence of tetrodotoxin which blocks the sodium channels involved in the propagation of action potentials. The effect of veratridine, a drug which maintains the sodium channels in the open state, was studied. It is shown here that in young cultures veratridine provoked a dramatic increase in total acetylcholinesterase activity and changed the distribution of the molecular forms of the enzyme, increasing the proportion and absolute amount of the A12 form. In order to elucidate the mechanism of action of this drug, the effects of various ions, ionophores, or other agents that modify the ionic permeabilities of membranes were also investigated. 相似文献
940.
Neuropeptide Y receptor in the rat brain 总被引:6,自引:0,他引:6
The specific binding of the chloramine-T iodinated neuropeptide Y (125I-NPY) to membranes from rat cerebral cortex was investigated using equilibrium binding and kinetic methods. The equilibrium binding of 125I-NPY at 37 degrees C was characterized by a Kd value of 0.38 nM. The receptor densities in the cerebral cortex, hypothalamus and cerebellum were 0.45 pmol/mg, 0.47 pmol/mg and 0.04 pmol/mg protein respectively. The binding site for 125I-NPY was sensitive to treatment with proteolytic enzymes and thiol reagents. The binding showed a sharp optimum at pH 7-7.7 and was inhibited by increasing concentrations of Mg2+. 相似文献