全文获取类型
收费全文 | 31336篇 |
免费 | 74篇 |
国内免费 | 142篇 |
专业分类
系统科学 | 196篇 |
丛书文集 | 396篇 |
教育与普及 | 82篇 |
理论与方法论 | 103篇 |
现状及发展 | 13677篇 |
研究方法 | 1399篇 |
综合类 | 15262篇 |
自然研究 | 437篇 |
出版年
2013年 | 223篇 |
2012年 | 473篇 |
2011年 | 889篇 |
2010年 | 195篇 |
2008年 | 565篇 |
2007年 | 648篇 |
2006年 | 640篇 |
2005年 | 650篇 |
2004年 | 640篇 |
2003年 | 598篇 |
2002年 | 554篇 |
2001年 | 1067篇 |
2000年 | 1017篇 |
1999年 | 653篇 |
1994年 | 343篇 |
1992年 | 607篇 |
1991年 | 470篇 |
1990年 | 539篇 |
1989年 | 485篇 |
1988年 | 440篇 |
1987年 | 522篇 |
1986年 | 517篇 |
1985年 | 627篇 |
1984年 | 489篇 |
1983年 | 433篇 |
1982年 | 389篇 |
1981年 | 393篇 |
1980年 | 423篇 |
1979年 | 1040篇 |
1978年 | 804篇 |
1977年 | 755篇 |
1976年 | 597篇 |
1975年 | 653篇 |
1974年 | 878篇 |
1973年 | 765篇 |
1972年 | 739篇 |
1971年 | 878篇 |
1970年 | 1171篇 |
1969年 | 856篇 |
1968年 | 780篇 |
1967年 | 843篇 |
1966年 | 742篇 |
1965年 | 529篇 |
1959年 | 292篇 |
1958年 | 481篇 |
1957年 | 345篇 |
1956年 | 323篇 |
1955年 | 269篇 |
1954年 | 268篇 |
1948年 | 235篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
271.
A. Borowska S. Sierakowski J. Maćkowiak K. Wiśniewski 《Cellular and molecular life sciences : CMLS》1979,35(10):1368-1370
Summary A correlation between the postirradiation increase of the small intestine motility and the prostaglandin-like activity in this organ during gastrointestinal syndrome was observed. Indomethacin decreased the elevated motility of intestine and reduced the prostaglandin-like activity in this syndrome.Acknowledgments. The work was supported by the Polish Academy of Sciences. 相似文献
272.
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
273.
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
274.
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
275.
276.
Summary An intermediate stage between the elementary and the initial bodies of theRickettsiella genus is defined as the beginning of an intracellular cycle. It is characterized by several structural changes in the dense elementary body: the cytoplasm becomes less electron-dense; thus, the nucleoid and the ribosomes are visible. The inner layer of the cell-wall becomes progressively clearer and the trilamellar structure of the inner and outer membranes appears distinctly. Preinitial body is proposed as name of this stage of development. 相似文献
277.
P. J. Müller P. Masner Maria Kälin W. S. Bowers 《Cellular and molecular life sciences : CMLS》1979,35(5):704-705
Summary Corpora allata fromOncopeltus fasciatus incubated in vitro in medium containing 10–5.35 M (1 g/ml) of precocene II lose their ability to secrete juvenile hormone when reimplanted into last instar larvae.Acknowledgments. We thank Mr K. Dorn, Mrs L. Dolezal, Mrs V. Nötzli-Graf, Mr K.H. Trautmann and Mr A. Schuler for technical help, Dr W. Vogel and Dr A. Dübendorfer for valuable discussions. 相似文献
278.
MEASUREMENT of the absolute value of absorption by water vapour at microwave frequencies is difficult because the effect is so small. Far in the wings of the absorption lines, in the so-called 'windows' of the spectrum, it is especially difficult to achieve high accuracy in the free atmosphere. But it is in these windows that the behaviour of the absorption is important from both applied and scientific points of view. Satellite communications, remote sensing of the atmosphere, and radioastronomy, are all influenced by this behaviour. Measurements on an Earth-space path are reported here; the results indicate a nonlinear relationship between absorption and water-vapour content. 相似文献
279.
280.
C. P. Sigdestad D. J. Grdina K. Ando 《Cellular and molecular life sciences : CMLS》1979,35(6):815-817
Summary Cells from a murine fibrosarcoma (FSa) have been grown in vitro as multicell tumor spheroids (MTS). The growth rate of these MTS was determined. Follwing selected periods of growth, MTS were made into a single cell suspension and separated on linear density gradients of Renografin. While only 1 population of cells was separated from small spheroids (400 m diameter), at least 3 subpopulations of tumor cells were separated and isolated from large spheroids (800 m in diameter).This investigation was supported in part by grants numbered CA-18628 and CA-06294, awarded by the National Cancer Institute, DHEW. 相似文献