全文获取类型
收费全文 | 21660篇 |
免费 | 364篇 |
国内免费 | 504篇 |
专业分类
系统科学 | 478篇 |
丛书文集 | 318篇 |
教育与普及 | 251篇 |
理论与方法论 | 72篇 |
现状及发展 | 5439篇 |
研究方法 | 643篇 |
综合类 | 15119篇 |
自然研究 | 208篇 |
出版年
2022年 | 200篇 |
2021年 | 211篇 |
2016年 | 191篇 |
2015年 | 291篇 |
2014年 | 367篇 |
2013年 | 389篇 |
2012年 | 533篇 |
2011年 | 765篇 |
2010年 | 435篇 |
2009年 | 474篇 |
2008年 | 689篇 |
2007年 | 726篇 |
2006年 | 597篇 |
2005年 | 603篇 |
2004年 | 544篇 |
2003年 | 547篇 |
2002年 | 615篇 |
2001年 | 870篇 |
2000年 | 789篇 |
1999年 | 721篇 |
1998年 | 368篇 |
1997年 | 358篇 |
1996年 | 337篇 |
1995年 | 250篇 |
1994年 | 496篇 |
1993年 | 263篇 |
1992年 | 473篇 |
1991年 | 394篇 |
1990年 | 406篇 |
1989年 | 339篇 |
1988年 | 302篇 |
1987年 | 276篇 |
1986年 | 274篇 |
1985年 | 325篇 |
1984年 | 247篇 |
1979年 | 409篇 |
1978年 | 322篇 |
1977年 | 288篇 |
1976年 | 239篇 |
1975年 | 239篇 |
1974年 | 299篇 |
1973年 | 258篇 |
1972年 | 280篇 |
1971年 | 320篇 |
1970年 | 410篇 |
1969年 | 326篇 |
1968年 | 334篇 |
1967年 | 287篇 |
1966年 | 327篇 |
1965年 | 218篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
In vivo studies indicated that the primary effects of E. coli endotoxin on hepatic clearance of sulfobromophthalein were at the excretory level. Newborns were more sensitive to the LPS than older animals. 相似文献
132.
133.
Incorporation of 32P into adrenal mitochondrial phospholipids (PL) incrased in ACTH-treated rats, but it decreased in diabetics, inspite of the fact that these animals showed adrenal overacity. Since diabetics did not show increased 11 beta-hydroxylation. as opposed to ACTH-treated rats, it is suggested that the stimulation of this enzyme activity by exogenous ACTH is related to an increased turnover of PL at the mitochondrial membrane. The process is impaired in diabetics and prevents the stimulation of 11 beta-hydroxylation. 相似文献
134.
Summary Pronase and -chymotrypsin digested the major glycoprotein in the human and mouse red cell membranes and in SDS gel electrophoresis the glycoprotein disappeared accompanied by the appearance of a new band of lower mol.wt. However in the membranes of sheep, rat and rabbit, no digestion was demonstrated. The effects of pronase on anion permeability were almost identical for human and animal erythrocytes. 相似文献
135.
Summary N-(5-Phosphopyridoxyl)-4-aminobutyric acid, a stable adduct of pyridoxal phosphate and 4-aminobutyric acid, has been shown to be a potent inhibitor of rat brain 4-aminobutyric acid aminotransferase (GABA-T) with a Ki of 1.4 M.Acknowledgments. This work was supported in part by the United Parkinson Foundation, l'Association Canadienne l'Ataxie de Friedreich, and the Medical Research Council of Canada. 相似文献
136.
Summary Homogenates from T. cruzi epimastigotes produced 3.4 pmoles H2O2/min 106 cells, as detected by the cytochrome c peroxidase assay. Addition of NADH or NADPH increased H2O2 production by a factor of 3 and 5, respectively. When supplemented with NADH and NADPH, the mitochondrial, microsomal, and supernatant fractions produced H2O2, the soluble fraction and the mitochondrial membranes being apparently the main generators of H2O2. The epimastigote homogenates showed cyanide-sensitive superoxide dismutase activity, equivalent to 0.28 g bovine superoxide dismutase per mg homogenate protein.This investigation was supported by grants from Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET) Argentina and the Scientific Office, American States Organization.Career Investigator of CONICET. 相似文献
137.
M. D. Adams J. T. Earnhardt B. R. Martin L. S. Harris W. L. Dewey R. K. Razdan 《Cellular and molecular life sciences : CMLS》1977,33(9):1204-1205
Summary Abnormal-8-tetrahydrocannabidiol (ABN-8-THC) failed to elicit central nervous system and cardiovascular effects in laboratory animals. Abnormal-cannabidiol (ABN-CBD) was also devoid of overt behavioral effects but produced marked hypotension with only slight bradycardia in anesthesized dogs.Acknowledgment. This work was supported by NIDA (grant No. DA-00574-01 and DA-00490) and Virginia Heart Society (grant No. RR-05697) 相似文献
138.
H. -J. Hess J. S. Bindra J. W. Constantine W. Elger O. Loge E. Schillinger W. Losert 《Cellular and molecular life sciences : CMLS》1977,33(8):1076-1077
Summary N-methanesulfonyl 16-phenoxy--tetranor PGE2 is a prostaglandin analog which is markedly more tissue selective than PGE2. This compound is 10–30 times more potent than PGE2 in animal models which are considered relevant to antifertility effects in humans. In pharmacological tests which are believed to be predictive for side effects in humans, the compound has potency either equal to or less than that of PGE2. 相似文献
139.
Immune response (Ir) genes are linked to the species histocompatibility complex and define as yet uncharacterised phenotypic products which control the immune response to thymus dependent antigens. Antibody formation and antigen induced T lymphocyte proliferation are two examples of immune phenomena which, in vivo and in vitro, operate under Ir gene influence. To clarify their mechanism of action and cellular location, we have examined the contribution of antigen structure (amino acid sequence and conformation to Ir gene control of antigen recognition by T lymphocytes) as well as to the critical role played by the antigen presenting macrophage in expression of that control. We report that immune response gene control of antigen recognition operates at least in part at the level of the macrophage. 相似文献
140.
Summary Sodium diethyldithiocarbamate, 2,6-di-tert-butylphenol and N,N-diphenyl-p-phenylenediamine inhibited the generation of medullary prostaglandin E, but 1,2-dimethoxyethane (OH scavenger) and 2,5-dimethylfuran (1O2 scavenger) stimulated basal prostaglandin E production 1.2–1.3-fold. These results suggest that the balance between formation and removal of cellular lipid peroxides sets a peroxide level that can regulate the rate of prostaglandin formation in cells. 相似文献