全文获取类型
收费全文 | 1947篇 |
免费 | 9篇 |
国内免费 | 17篇 |
专业分类
系统科学 | 9篇 |
丛书文集 | 16篇 |
教育与普及 | 1篇 |
理论与方法论 | 7篇 |
现状及发展 | 878篇 |
研究方法 | 61篇 |
综合类 | 997篇 |
自然研究 | 4篇 |
出版年
2012年 | 28篇 |
2011年 | 28篇 |
2010年 | 11篇 |
2009年 | 10篇 |
2008年 | 35篇 |
2007年 | 40篇 |
2006年 | 41篇 |
2005年 | 68篇 |
2004年 | 78篇 |
2003年 | 36篇 |
2002年 | 26篇 |
2001年 | 56篇 |
2000年 | 56篇 |
1999年 | 57篇 |
1996年 | 10篇 |
1994年 | 259篇 |
1992年 | 37篇 |
1991年 | 21篇 |
1990年 | 35篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 44篇 |
1984年 | 29篇 |
1983年 | 18篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 27篇 |
1979年 | 60篇 |
1978年 | 23篇 |
1977年 | 38篇 |
1976年 | 28篇 |
1975年 | 28篇 |
1974年 | 38篇 |
1973年 | 43篇 |
1972年 | 43篇 |
1971年 | 42篇 |
1970年 | 39篇 |
1969年 | 38篇 |
1968年 | 42篇 |
1967年 | 46篇 |
1966年 | 30篇 |
1965年 | 21篇 |
1964年 | 18篇 |
1959年 | 14篇 |
1958年 | 16篇 |
1957年 | 17篇 |
1956年 | 12篇 |
1955年 | 13篇 |
排序方式: 共有1973条查询结果,搜索用时 15 毫秒
11.
H. Nawrath J. Rupp H. Jakob U. Sack F. Mertzlufft W. Dick 《Cellular and molecular life sciences : CMLS》1989,45(4):337-339
Summary The opioid agonists morphine (selective for -receptors) and ethylketocyclazocine (selective for kappa-receptors), at concentrations evoking strong effects in neuronal structures, did not significantly affect the configuration of the intracellularly recorded action potential and the force of contraction in ventricular heart muscle isolated from guinea pigs, rabbits and man. These results suggest that any changes of heart functions in vivo in response to opioid-like drugs are probably not mediated postsynaptically at the myocardial cell membrane but rather presynaptically, influencing the release of noradrenaline and/or acetylcholine from the nerve terminals. 相似文献
12.
E. Flückiger U. Briner B. Clark A. Closse A. Enz P. Gull A. Hofmann R. Markstein L. Tolcsvai H. R. Wagner 《Cellular and molecular life sciences : CMLS》1988,44(5):431-436
Summary The profile of action in animals of CQP 201-403, a novel 8-amino-ergoline, is in most aspects that of a very potent dopaminomimetic, both as a prolactin secretion inhibitor, and at the levels of the CNS and the cardiovascular system. Qualitatively CQP 201-403 differs slightly from bromocriptine and apomorphine in its effects on the CNS (no influence on serotonin metabolism in the rat cortex; induction of masculine mounting behavior in rats) and the cardiovascular system of the dog (reflex tachycardia in response to a blood-pressure fall). In man the new compound proved to be highly active in lowering prolactin serum levels and to be more potent than bromocriptine (Parlodel®).In memory of Dr Annemarie Closse, who died 14 June 1987. 相似文献
13.
Summary The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 g retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [3H]-thymidine and [3H]-leucine, respectively. A dose-dependent effect of maternal vitamin A restriction on the metabolism of DNA, RNA and protein was noticed in the developing fetal brain of rats. 相似文献
14.
H. U. Wanner 《Cellular and molecular life sciences : CMLS》1993,49(9):754-758
Most air pollutants do not lead to specific diseases. Depending on the pollutant, the concentration and the duration of exposure, some organs are more affected than others. The most frequent disorders are those caused by irritant gases and particulates on the mucous membranes and respiratory organs. The consequences are eye, nose and throat inflammations, diminished lung function, increased susceptability to respiratory infection and a higher incidence of chronic bronchitis. These disorders and diseases are, of course, influenced by other factors as well, such as immune deficiency, allergies, occupational exposure to pollutants, and particularly smoking. The effects of air pollutants are, therefore, multifactorially conditioned and nonspecific disorders are placed in the foreground. Evidence for an association of air pollution with adverse effects on human health is drawn from three sources: animal experiments, experimental human exposures, and epidemiologic studies of exposed human populations. The burden of atmospheric pollution must be reduced to protect human health by an adequate safety margin. In particular, the increased sensitivity of sick and aged people as well as children should be taken into account. In defining the maximum emmission levels, preventive aspects should have priority so as to keep the risk of damage to health and the harmful influences on the environment to a minimum.This article Effects of atmospheric pollution on human health by H. U. Wanner is a revised version of the same article that was first published in the Proceedings of the 1990 European Aerosol Conference; special issue of the J. Aerosol Sci., Vol. 21, Suppl. 1 (1990) 389–396.Reprinted with kind permission from Pergamon Press Ltd, Headington Hill Hall, Oxford OX3 0BW, Great Britain. 相似文献
15.
Ecological long-term effects of cultigens becoming feral and of naturalization of non-native species
Transgenic cultigens may become feral as we know of some non-transgenic cultigens. The article explains two basic ways how cultigens become feral: through hybridization with a closely related wild plant and through revert to the wild-type. A long list of examples of cultigens becoming feral in Central Europe is presented. The process of becoming feral is compared to the naturalization of non-native species (Exotic Species Model). Ecological long-term effects of both cultigens becoming feral and non-native species being naturalized are discussed with special regard to the predictability of such events. The ecological aspects discussed in the article are as significant for transgenic cultigens as for non-transgenic cultigens. 相似文献
16.
D. V. Amin R. B. Doctor A. O. Girdhar U. H. Shah 《Cellular and molecular life sciences : CMLS》1980,36(12):1410-1411
Summary Prostaglandin (PG) release was measured from the isolated perfused rabbit heart. The effects of -adrenergic stimulation and blockade suggest that PG synthesis is regulated in part by adrenergic mechanisms. 相似文献
17.
18.
19.
H. U. Keller J. H. Wissler J. Ploem 《Cellular and molecular life sciences : CMLS》1979,35(12):1669-1671
Summary Serum peptides containing classical anaphylatoxin (CAT) produce marked chemotactic orientation of human neutrophil granulocytes without modifying cell attachment to the substratum. Furthermore gradients of adhesion produced with gammaglobulins fail to induce morphological orientation of neutrophils. The results suggest that chemotaxis is not a special case of haptotaxis.The excellent technical assistance of Miss M. Schuster, Mrs A. Damschen and Mr M. Arnold is gratefully acknowledged. This work was supported by the Swiss National Science Foundation and the Sandoz-Stiftung zur Förderung der Medizinisch-Biologischen Forschung. 相似文献
20.
系统地阐述了铁氧体可变特征阻抗传输线的设计理论,结合德国重离子物理研究所交叉指强流直线加速器的束载对高频功率馈送的输入阻抗的影响,设计了一个可以在强的加速柬载下实现高频功率源和加速腔高频输入阻抗良好匹配的铁氧体可变阻抗适配器。 相似文献