全文获取类型
收费全文 | 30750篇 |
免费 | 70篇 |
国内免费 | 118篇 |
专业分类
系统科学 | 213篇 |
丛书文集 | 388篇 |
教育与普及 | 66篇 |
理论与方法论 | 124篇 |
现状及发展 | 12364篇 |
研究方法 | 1440篇 |
综合类 | 15741篇 |
自然研究 | 602篇 |
出版年
2013年 | 277篇 |
2012年 | 501篇 |
2011年 | 1136篇 |
2010年 | 205篇 |
2009年 | 140篇 |
2008年 | 567篇 |
2007年 | 682篇 |
2006年 | 684篇 |
2005年 | 667篇 |
2004年 | 658篇 |
2003年 | 586篇 |
2002年 | 598篇 |
2001年 | 1080篇 |
2000年 | 1040篇 |
1999年 | 631篇 |
1992年 | 573篇 |
1991年 | 466篇 |
1990年 | 512篇 |
1989年 | 494篇 |
1988年 | 460篇 |
1987年 | 480篇 |
1986年 | 513篇 |
1985年 | 548篇 |
1984年 | 476篇 |
1983年 | 421篇 |
1982年 | 348篇 |
1981年 | 355篇 |
1980年 | 408篇 |
1979年 | 960篇 |
1978年 | 755篇 |
1977年 | 734篇 |
1976年 | 564篇 |
1975年 | 635篇 |
1974年 | 919篇 |
1973年 | 757篇 |
1972年 | 737篇 |
1971年 | 935篇 |
1970年 | 1193篇 |
1969年 | 822篇 |
1968年 | 794篇 |
1967年 | 804篇 |
1966年 | 731篇 |
1965年 | 513篇 |
1959年 | 278篇 |
1958年 | 465篇 |
1957年 | 349篇 |
1956年 | 275篇 |
1955年 | 242篇 |
1954年 | 247篇 |
1948年 | 204篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
31.
Kang J.Y. Xu F.C. 《中国科学基金(英文版)》2004,(2):57-58,64
1 Introduction
Nanoscale science and technology have attracted greatattention since the novel properties become dominant for well-known materials as their sizes reduced to some critical dimension. These properties frequently originate in lattice distortions, structure transformations etc[1]. The variations of size and structure ofnanocrystals lead to the change of their electronic structures. Very recently, nanoscale materials with different electronic structures were utilized in fabricating nanoscale junctions[2].
…… 相似文献
32.
33.
Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages. 相似文献
34.
Human cytomegalovirus UL97 open reading frame encodes a protein that phosphorylates the antiviral nucleoside analogue ganciclovir. 总被引:32,自引:0,他引:32
Human cytomegalovirus (HCMV, a betaherpes virus) is the cause of serious disease in immunologically compromised individuals, including those with acquired immunodeficiency syndrome. One of the compounds used in the chemotherapy of HCMV infections is the nucleoside analogue 9-(1,3-dihydroxy-2-propoxymethyl)-guanine (ganciclovir). The mechanism of action of this drug is dependent on the formation of the nucleoside triphosphate, which is a strong inhibitor of the viral DNA polymerase. Thymidine kinase, which is encoded by many of the herpesviruses, catalyses the initial phosphorylation of ganciclovir. But there is no evidence for the coding of this enzyme by HCMV, and DNA sequence analysis of the HCMV genome has shown that there is no open reading frame characteristic of a herpesvirus thymidine kinase. Here we present biochemical and immunological evidence that the HCMV UL97 open reading frame codes for a protein capable of phosphorylating ganciclovir. This protein seems to be responsible for the selectivity of ganciclovir and will be useful tool in the understanding and refinement of the antiviral activity of new selective anti-HCMV compounds. 相似文献
35.
A. F. McDonagh Y. -M. Pu D. A. Lightner 《Cellular and molecular life sciences : CMLS》1992,48(3):246-248
The characteristic circular dichroism of bilirubin bound to human serum albumin undergoes a remarkable sign inversion on addition of halothane, chloroform and other volatile anesthetics. This sign inversion, which is completely reversed by removal of the anesthetic, reflects a pronounced conformational change of the bound ligand; probably a complete inversion of chirality. The observation suggests that association of volatile anesthetics with proteins can markedly alter the internal topography of receptor sites and potentially influence the stereoselectivity of ligand binding. 相似文献
36.
37.
We recently reported on a linkage study within a Quarter Horse lineage segregating hyperkalaemic periodic paralysis (HYPP), an autosomal dominant condition showing potassium-induced attacks of skeletal muscle paralysis. HYPP co-segregated with the equine adult skeletal muscle sodium channel alpha subunit gene, the same gene that causes human HYPP. We now describe the Phe to Leu mutation in transmembrane domain IVS3 which courses the horse disease. This represents the first application of molecular genetics to an important horse disease, and the data will provide an opportunity for control or eradication of this condition. 相似文献
38.
本文根据浙江省教委、省基金、舟山市科委关于浙江沿海虾蛄生物学及其开发利用研究的要求,对四年多来的研究进行总结,主要包括资源与分布、生物学习性、暂养及运输技术、营养成份分析、开发利用等诸方面 相似文献
39.
Thyroid cancer after Chernobyl. 总被引:17,自引:0,他引:17
40.