全文获取类型
收费全文 | 79306篇 |
免费 | 298篇 |
国内免费 | 596篇 |
专业分类
系统科学 | 1303篇 |
丛书文集 | 1145篇 |
教育与普及 | 305篇 |
理论与方法论 | 581篇 |
现状及发展 | 39259篇 |
研究方法 | 1899篇 |
综合类 | 33515篇 |
自然研究 | 2193篇 |
出版年
2013年 | 843篇 |
2012年 | 931篇 |
2011年 | 3119篇 |
2008年 | 1213篇 |
2007年 | 1385篇 |
2006年 | 1443篇 |
2005年 | 1600篇 |
2004年 | 2690篇 |
2003年 | 2326篇 |
2002年 | 2066篇 |
2001年 | 2218篇 |
2000年 | 1680篇 |
1999年 | 1402篇 |
1997年 | 784篇 |
1994年 | 691篇 |
1993年 | 699篇 |
1992年 | 1357篇 |
1991年 | 1121篇 |
1990年 | 1236篇 |
1989年 | 1070篇 |
1988年 | 1016篇 |
1987年 | 1065篇 |
1986年 | 1079篇 |
1985年 | 1280篇 |
1984年 | 1057篇 |
1983年 | 917篇 |
1982年 | 956篇 |
1981年 | 979篇 |
1980年 | 1151篇 |
1979年 | 2115篇 |
1978年 | 1874篇 |
1977年 | 1837篇 |
1976年 | 1481篇 |
1975年 | 1561篇 |
1974年 | 1832篇 |
1973年 | 1825篇 |
1972年 | 1906篇 |
1971年 | 2129篇 |
1970年 | 2567篇 |
1969年 | 2081篇 |
1968年 | 2008篇 |
1967年 | 1961篇 |
1966年 | 1663篇 |
1965年 | 1259篇 |
1959年 | 740篇 |
1958年 | 1097篇 |
1957年 | 867篇 |
1956年 | 748篇 |
1955年 | 668篇 |
1954年 | 714篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
731.
Summary The D-galactose specific lectin fromViscum album L. reacts with serum proteins that contain the corresponding D-galactopyranosyl residues. By affinity chromatography of human serum on lectin-sepharose IgM, 2-macroglobulin, haptoglobin and -lipoprotein were quantitatively retained. Only parts of IgA, IgG and transferrin were retarded. The other serum proteins are unbounded as albumin, 1A– and 1C. 相似文献
732.
Summary Physostigmine in a dose of 0.1 mg/kg i.v. expressly stimulated the oxygen uptake in the rat cerebral cortex. This effect was blocked by propranolol and seems be mediated by catecholamines. Since atropine also antagonized the stimulant effect of physostigmine, it appears that the action of physostigmine is primarily cholinergic and that the adrenergic effect is a secondary phenomenon. The higher dose of physostigmine (0.4 mg/kg i.v.) caused a depression of rat brain oxygen uptake.This work was supported by a grant from Serbian Republic Scientific Fund (ZMNU SR Srbija), Belgrade (Yugoslavia).The authors wish to acknowledge the skilful technical assistance of Lj. Krsti. 相似文献
733.
A. Matsuo H. Nozaki H. Kataoka M. Nakayama S. Hayashi 《Cellular and molecular life sciences : CMLS》1979,35(10):1279-1280
Summary A new enantiomeric sesquiterpene alcohol named (–)-maalian-5-ol was isolated from the liverwort, and the structure and absolute configuration was determined to be the stereostructureI by chemical and spectral evidence.The authors express their gratitude to Dr H. Inoue, National Science Museum, for identification of the liverwort, and Prof. T. Tokoroyama, Osaka City University, for sending of the data of (–)--maaliene and (+)-selina-5,11-diene. Thanks are also due to the Ministry of Education for financial support of this work. 相似文献
734.
Three acidic polysaccharide (AP) fractions and the prostaglandin-like substances (PLS) isolated from P. acnes were investigated regarding their chemotactic activities on polymorphonuclear leukocytes. Both AP's and PLS induced a significant chemotatic response, which suggests their involvement in inflammatory acne vulgaris. 相似文献
735.
It was shown that, in physiological concentrations, insulin enhances, in vitro, the immunological phagocytosis of sensitized sheep erythrocytes by cultured mouse peritoneal macrophages. Insulin seems to stimulate macrophage phagocytosis as a cholinomimetic agonist by increasing the intracellular levels of cyclic GMP. 相似文献
736.
Field stimulation of isolated, spirally-cut cervix from day-22 pregnant rats produced contractions which could be inhibited by tetrodotoxin or hyoscine and potentiated by propranolol. The rat cervix would appear to receive both cholinergic and noradrenergic innervations whose transmitters activate muscarinic cholinoceptors and beta-adrenoceptors respectively. 相似文献
737.
M Marx M Kaczorek P Cerutti 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,289(14):1021-1024
Linear unintegrated DNA of Schmidt-Ruppin Rous sarcoma virus, subgroup D (SR-RSV-D), was digested with SmaI restriction endonuclease, analyzed by agarose gel electrophoresis, "blotted" by Southern's method and hybridized with a viral 32P cDNA. SmaI cleaves this DNA at five sites, two of which are localized at the ends of the provirus. Src and env genes seem not to be restrictied by SmaI cleavage. 相似文献
738.
A. F. Furtado 《Cellular and molecular life sciences : CMLS》1979,35(8):1123-1124
Summary 2 factors elaborated by distinct neurosecretory cells in the pars intercerebralis control moulting inPanstrongylus megistus. The 1st, originating probably in the A cells, activates the thoracic gland. The 2nd, produced by the A cells, acts at an earlier stage in a different way.Supported by CNPq., Brésil and DGRST (aide No. 76.7.0716). 相似文献
739.
The enzymes which were extracted by autodigestion from the microsomal fractions of the pig kidney, liver and submaxillary gland and from the serum showed an immunochemical identity by a double immunodiffusion test. But the kidney enzyme had a different pI-value from the pI-values of the enzymes of other organs. 相似文献
740.
Suppressor cell induction can be demonstrated during antigen specific blastogenesis by using the same methods which have shown induction of suppressor cells by Con A. Since suppressor cells are rapidly generated during antigen specific blastogenesis, they must regulate the final level of blastogenesis induced during the seven day in vitro incubation. 相似文献