全文获取类型
收费全文 | 26690篇 |
免费 | 295篇 |
国内免费 | 575篇 |
专业分类
系统科学 | 429篇 |
丛书文集 | 462篇 |
教育与普及 | 317篇 |
理论与方法论 | 88篇 |
现状及发展 | 5865篇 |
研究方法 | 792篇 |
综合类 | 19285篇 |
自然研究 | 322篇 |
出版年
2021年 | 268篇 |
2015年 | 262篇 |
2014年 | 375篇 |
2013年 | 470篇 |
2012年 | 546篇 |
2011年 | 951篇 |
2010年 | 462篇 |
2009年 | 428篇 |
2008年 | 721篇 |
2007年 | 787篇 |
2006年 | 701篇 |
2005年 | 685篇 |
2004年 | 598篇 |
2003年 | 512篇 |
2002年 | 552篇 |
2001年 | 967篇 |
2000年 | 975篇 |
1999年 | 934篇 |
1998年 | 611篇 |
1997年 | 614篇 |
1996年 | 560篇 |
1995年 | 496篇 |
1994年 | 448篇 |
1993年 | 363篇 |
1992年 | 651篇 |
1991年 | 565篇 |
1990年 | 514篇 |
1989年 | 551篇 |
1988年 | 466篇 |
1987年 | 390篇 |
1986年 | 354篇 |
1985年 | 328篇 |
1984年 | 276篇 |
1983年 | 245篇 |
1979年 | 504篇 |
1978年 | 391篇 |
1977年 | 367篇 |
1976年 | 304篇 |
1975年 | 348篇 |
1974年 | 496篇 |
1973年 | 378篇 |
1972年 | 388篇 |
1971年 | 491篇 |
1970年 | 608篇 |
1969年 | 417篇 |
1968年 | 448篇 |
1967年 | 379篇 |
1966年 | 384篇 |
1965年 | 259篇 |
1958年 | 225篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
M. Caron G. Cherqui D. Wicek J. Capeau J. Bertrand J. Picard 《Cellular and molecular life sciences : CMLS》1988,44(1):34-37
Summary Insulin stimulation of glycogen synthesis was nearly abolished in hepatoma cells shortly treated with 4 ß-phorbol 12 \-myristate, 13 -acetate (protein kinase C activation) but remained unmodified in cells chronically treated with the phorbol ester (protein kinase C depletion). Thus, although exogenous activation of protein kinase C results in an inhibition of insulin action, protein kinase C depletion has no influence on this process. The results suggest that, in hepatoma cells, no endogenous activation of protein kinase C may occur in response to the signal triggered by insulin. 相似文献
102.
D. Porquet M. Appel T. Fournier O. Bertaux D. Biou J. Féger 《Cellular and molecular life sciences : CMLS》1992,48(3):257-261
Both in vivo and in vitro models have certain disadvantages for the study of the chronic hepatotoxicity of drugs. The aim of this work was to evaluate a new approach based on an in vivo/in vitro model. After chronic in vivo treatment of rats with Vincamine and Vindeburnol (an eburnamenine derivative which exhibits hepatotoxic properties in man) liver cells were isolated, and functional and metabolic disorders (metabolic utilization of fructose and protein biosynthesis) were studied to determine injury. The results showed no modification of blood parameters, but a direct relationship between the dose of Vindeburnol administered in vivo and the metabolic disorders observed in vitro, evidencing the high sensitivity and reliability of this model. 相似文献
103.
本文具有对一次仪表转换系数进行校准的功能,温度补偿及模数转换电路设计方法独特,只用一块运算放大器与一块单片模数转换电路完成了pH转换功能。 相似文献
104.
R. Wiesendanger B. Martinoni T. Boller D. Arigoni 《Cellular and molecular life sciences : CMLS》1986,42(2):207-209
Summary Under the action of the appropriate synthase from ripe tomatoes a 11 mixture of (3S, 4R)-[3,4-2H2] and (3R, 4S)-[3,4-2H2]-(2S)-adenosylmethionine is transformed into a 11 mixture of the two meso forms of [2H2]-1-aminocyclopropanecarboxylic acid, a result which proves the operation of an inversion mechanism and which is consistent with direct nucleophilic displacement of the leaving group in the substrate. 相似文献
105.
D. Dubourdieu 《Cellular and molecular life sciences : CMLS》1986,42(8):914-921
Conclusion Current enological research does not aim at developing technological wines whose organoleptic characteristics are basically determined by the methods used in the transformation of grape wine, but rather to refine methods which will highlight the original qualities of different cultivars and viticultural conditions. 相似文献
106.
Evolution of the atmosphere and oceans 总被引:1,自引:0,他引:1
The residence times of most constituents of the atmosphere and oceans are small fractions of the age of the Earth and, in general, their rate of output has been nearly equal to their rate of input. We are disturbing a number of these dynamic equilibria quite severely. The mineralogy of marine evaporites rules out drastic changes in the composition of sea water during the last 900 Myr. The chemistry of soils formed more than 1,000 Myr ago suggests that the atmosphere then contained significantly more CO2 and less O2 than at present. Hydrogen peroxide may well have been the principal oxidant and formaldehyde the main reductant in rain water between 3,000 and 1,000 Myr ago. Major changes in atmospheric chemistry since that time are almost certainly related to the evolution of the biosphere. 相似文献
107.
本文提供了用电子计算机计算分析和绘制Lienard方程极限环的方法及其BASIC 语言程序,并利用此方法构造了具有三个极限环的两个Lienard方程,绘制了极限环 图形,指明了C.C.Pugh猜想中极限环的存在性与特征函数的二阶导数F(Z)的变号 有相当的关系。 相似文献
108.
Antidiuretic effects of oxytocin in the Brattleboro rat 总被引:1,自引:0,他引:1
J. Lyness A. G. Robinson M. N. Sheridan D. M. Gash 《Cellular and molecular life sciences : CMLS》1985,41(11):1444-1446
Summary The antidiuretic activity of oxytocin (OT) was measured in Brattleboro rats with congenital diabetes insipidus. A dose dependent antidiuretic response was found in animals receiving chronic infusions of 0.1 g/h, 1.0 g/h, and 5 g/h of OT. OT infused at the rate of 5 g/h over a 7-day period completely reversed the symptoms of diabetes insipidus. The results support the concept that OT serves as a weak agonist of vasopressin at the level of the kidney and at pharmacological levels exhibits antidiuretic activity. 相似文献
109.
J. R. Aldrich J. P. Kochansky J. D. Sexton 《Cellular and molecular life sciences : CMLS》1985,41(3):420-422
Summary Workers and queens of the eastern yellowjacket,Vespula maculifrons, are attracted to the artificial long-range attractant pheromone of the predaceous pentatomid,Podisus maculiventris. A 11 mixture of linalool or -terpineol and (E)-2-hexenal is as attractive toV. maculifrons workers as the pheromone.We thank A.S. Menke of the Systematic Entomology Laboratory, USDA, for identifying the yellowjackets. Mention of a company name does not imply endorsement by the US Department of Agriculture. 相似文献
110.
N. Akaike K. Hattori Y. Oomura D. O. Carpenter 《Cellular and molecular life sciences : CMLS》1985,41(1):70-71
Summary Using isolated, internally perfused bullfrog dorsal root ganglion cells we have studied the dose-response curves for -aminobutyric acid (GABA) in the presence of internally or externally applied GABA antagonists. With external application of antagonists the inhibition of the GABA current by bicuculline was competitive and that by picrotoxin was noncompetitive. Picrotoxin but not bicuculline blocked when internally perfused.To whom reprint requests should be addressed.Acknowledgments. We thank Drs S. Minakami and S. Yasui for helpful discussions and comments. 相似文献