全文获取类型
收费全文 | 21513篇 |
免费 | 70篇 |
国内免费 | 103篇 |
专业分类
系统科学 | 84篇 |
丛书文集 | 139篇 |
教育与普及 | 47篇 |
理论与方法论 | 43篇 |
现状及发展 | 9246篇 |
研究方法 | 1002篇 |
综合类 | 10902篇 |
自然研究 | 223篇 |
出版年
2013年 | 183篇 |
2012年 | 341篇 |
2011年 | 531篇 |
2009年 | 131篇 |
2008年 | 401篇 |
2007年 | 459篇 |
2006年 | 454篇 |
2005年 | 446篇 |
2004年 | 425篇 |
2003年 | 413篇 |
2002年 | 378篇 |
2001年 | 798篇 |
2000年 | 753篇 |
1999年 | 490篇 |
1994年 | 328篇 |
1992年 | 456篇 |
1991年 | 325篇 |
1990年 | 383篇 |
1989年 | 330篇 |
1988年 | 304篇 |
1987年 | 372篇 |
1986年 | 351篇 |
1985年 | 457篇 |
1984年 | 353篇 |
1983年 | 321篇 |
1982年 | 295篇 |
1981年 | 264篇 |
1980年 | 277篇 |
1979年 | 738篇 |
1978年 | 551篇 |
1977年 | 497篇 |
1976年 | 445篇 |
1975年 | 456篇 |
1974年 | 548篇 |
1973年 | 489篇 |
1972年 | 453篇 |
1971年 | 538篇 |
1970年 | 722篇 |
1969年 | 553篇 |
1968年 | 558篇 |
1967年 | 522篇 |
1966年 | 504篇 |
1965年 | 374篇 |
1959年 | 182篇 |
1958年 | 301篇 |
1957年 | 198篇 |
1956年 | 188篇 |
1955年 | 171篇 |
1954年 | 181篇 |
1948年 | 147篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Descending pathways with monosynaptic action on motoneurones 总被引:2,自引:0,他引:2
63.
J. L. Lacuara S. R. de Barioglio P. P. de Oliva A. S. Bernacchi A. F. de Culasso J. A. Castro B. M. Franke de Cazzulo J. J. Cazzulo 《Cellular and molecular life sciences : CMLS》1991,47(6):612-616
Summary The tricyclic anti-calmodulin drug trifluoperazine (TFP) inhibited growth and motility of epimastigotes ofTrypanosoma cruzi, at concentrations lower than 100 M, and motility and infectivity of the bloodstream trypomastigote form at 200 M. Electron microscopy of TFP-treated epimastigotes showed that the major effect was at the mitochondrial level, with gross swelling and disorganization. The oligomycin-sensitive, mitochondrial ATPase was completely inhibited by 20 M TFP, and the same drug concentration caused a 60% decrease in intracellular ATP content. The results suggest that the trypanocidal effect of TFP may be related more to mitochondrial damage than to the well-known anticalmodulin effect of the drug. 相似文献
64.
65.
Summary The in vitro absorption of calcium from the duodenum was significantly less in a group of rats fed on a wheat diet than in a group fed a wheat and Bengal gram (7030) diet. 相似文献
66.
67.
MDMethodinSolvingMultipleCriteriaDecisionProblemsArisingfromInvestmentSystemsDUWenzhong;CIJianhua(EconomicInformationCenterof... 相似文献
68.
A. V. Edwards M. A. Ghatei S. R. Bloom 《Cellular and molecular life sciences : CMLS》1994,50(8):725-726
Mean plasma insulin concentration was reduced and mean plasma glucose concentration increased following the administration of N-nitro-L-arginine methyl ester (L-NAME; 100 mol kg–1 i.a.) in conscious calves given continuous infusions of exogenous glucose (30–60 mol min–1 kg–1 i.v.). It is concluded that the rise in plasma insulin concentration which occurs in these animals in response to glucose is mediated, at least in part, by a nitric oxide-related factor (NOx). 相似文献
69.
H. Tsuchiya M. Sato M. Iinuma J. Yokoyama M. Ohyama T. Tanaka I. Takase I. Namikawa 《Cellular and molecular life sciences : CMLS》1994,50(9):846-849
Phytoalexins, defensive compounds produced by plants against microbial infections, were purified fromSophora exigua (Leguminosae) and their growth inhibitory effects on oral cariogenic bacteria were determined in vitro. Among three isolated compounds, 5,7,2,4-tetrahydroxy-8-lavandulylflavanone completely inhibited the growth of oral bacteria including primary cariogenic mutans streptococci, other oral streptococci, actinomycetes, and lactobacilli, at concentrations of 1.56 to 6.25 g/ml. 相似文献
70.
Because of possible variation in venom composition, an understanding of venomous snake systematics is of great importance for the optimization of antivenom treatment of snakebite patients. Intraspecific variation in the morphology of many venomous snakes complicates the definition and indentification of some species when allopatric populations are involved. Selectively neutral or near-neutral mtDNA sequences can reveal evolutionary relationships obscured by ecogenetically-caused morphological variation. We use comparative sequencing of the cytochrome oxidase subunit 1 gene to reveal the existence of a widespread, cryptic species of spiting cobra from southeast Asia. This species,Naja siamensis, is widely sympatric with other Asiatic cobra species. This may be of considerable medical significance, and calls for further research into venom composition in Asiatic cobras. 相似文献