全文获取类型
收费全文 | 24346篇 |
免费 | 711篇 |
国内免费 | 239篇 |
专业分类
系统科学 | 1450篇 |
丛书文集 | 382篇 |
教育与普及 | 73篇 |
理论与方法论 | 336篇 |
现状及发展 | 7262篇 |
研究方法 | 922篇 |
综合类 | 14296篇 |
自然研究 | 575篇 |
出版年
2018年 | 785篇 |
2017年 | 789篇 |
2016年 | 514篇 |
2015年 | 156篇 |
2014年 | 156篇 |
2013年 | 297篇 |
2012年 | 806篇 |
2011年 | 2069篇 |
2010年 | 1182篇 |
2009年 | 795篇 |
2008年 | 1099篇 |
2007年 | 1434篇 |
2006年 | 687篇 |
2005年 | 681篇 |
2004年 | 590篇 |
2003年 | 514篇 |
2002年 | 445篇 |
2001年 | 523篇 |
2000年 | 573篇 |
1999年 | 418篇 |
1992年 | 289篇 |
1991年 | 260篇 |
1990年 | 257篇 |
1989年 | 231篇 |
1988年 | 212篇 |
1987年 | 231篇 |
1986年 | 209篇 |
1985年 | 246篇 |
1984年 | 239篇 |
1983年 | 163篇 |
1982年 | 176篇 |
1981年 | 162篇 |
1980年 | 201篇 |
1979年 | 449篇 |
1978年 | 345篇 |
1977年 | 379篇 |
1976年 | 270篇 |
1975年 | 329篇 |
1974年 | 456篇 |
1973年 | 385篇 |
1972年 | 367篇 |
1971年 | 432篇 |
1970年 | 495篇 |
1969年 | 442篇 |
1968年 | 419篇 |
1967年 | 451篇 |
1966年 | 389篇 |
1965年 | 308篇 |
1958年 | 232篇 |
1957年 | 179篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
阐述了高校图书馆应根据艺术类专业学生的特点,通过开设艺术阅览室、增加艺术类报刊文献的收藏比例、根据艺术专业特点进行文献检索与利用教学、利用网络为学生提供服务等手段和方法,有区别、有针对性地开展特色服务。 相似文献
992.
图书馆环境与读者健康 总被引:4,自引:0,他引:4
吕健 《科技情报开发与经济》2006,16(9):116-116,121
阐述了图书馆环境对读者生理及心理健康方面的影响,指出构建和谐的绿色图书馆是一项长期的工作任务,需要人们转变思想观念,同时争取社会各界的积极支持和广泛参与。 相似文献
993.
994.
排队论在油泵修理中的应用 总被引:2,自引:0,他引:2
吕敬堂 《系统工程理论与实践》2000,20(6):83-90
用一个实例 ,详细说明了排队模型在油泵修理实践中的应用方法 :从研究系统输入过程和服务时间的分布规律着手 ,最终推断出系统所符合的排队模型 ,求解模型的运行参数 ,并对结果进行了优化分析. 相似文献
995.
从解矩阵方程的角度出发 ,在理论上分析了雷达旁瓣对消系统对消旁瓣干扰的工作原理 ,并由此得出了雷达实现最佳旁瓣干扰对消所需满足的条件 ,同时给出了实际的雷达旁瓣对消系统可能的四种工作模式 ,并比较了其优缺点。给出的最佳旁瓣对消条件 ,在雷达旁瓣对消系统的整体设计和对消系统性能的分析中将具有实际的指导意义。 相似文献
996.
997.
Benharrat BELAIDI 《系统科学与复杂性》2007,20(1):41-46
In this paper, we investigate the growth of meromorphic solutions of higher order linear differential equation f^(k) +Ak-1 (z)e^Pk-1^(z) f^(k-1) +…+A1 (z)e^P1(z) f′ +Ao(z)e^Po(z) f = 0 (k ≤ 2), where Pj(z) (j = 0, 1,..., k - 1) are nonconstant polynomials such that deg Pj = n (j = 0, 1,..., k - 1) and Aj(z)(≠ 0) (j = 0, 1,..., k - 1) are meromorphic functions with order p(Aj) 〈 n (j = 0, 1,..., k - 1). 相似文献
998.
Samuel CS Hewitson TD Unemori EN Tang ML 《Cellular and molecular life sciences : CMLS》2007,64(12):1539-1557
The peptide hormone relaxin is emerging as a multi-functional factor in a broad range of target tissues including several
non-reproductive organs, in addition to its historical role as a hormone of pregnancy. This review discusses the evidence
that collectively demonstrates the many diverse and vital roles of relaxin: the homeostatic role of endogenous relaxin in
mammalian pregnancy and ageing; its gender-related effects; the therapeutic effects of relaxin in the treatment of fibrosis,
inflammation, cardioprotection, vasodilation and wound healing (angiogenesis) amongst other pathophysiological conditions,
and its potential mechanism of action. Furthermore, translational issues using experimental models (to humans) and its use
in various clinical trials, are described, each with important lessons for the design of future trials involving relaxin.
The diverse physiological and pathological roles for relaxin have led to the search for its significance in humans and highlight
its potential as a drug of the future.
Received 12 December 2006; received after revision 12 February 2007; accepted 15 March 2007 相似文献
999.
de Wit PJ 《Cellular and molecular life sciences : CMLS》2007,64(21):2726-2732
Plants have an innate immunity system to defend themselves against pathogens. With the primary immune system, plants recognize
microbe-associated molecular patterns (MAMPs) of potential pathogens through pattern recognition receptors (PRRs) that mediate
a basal defense response. Plant pathogens suppress this basal defense response by means of effectors that enable them to cause
disease. With the secondary immune system, plants have gained the ability to recognize effector-induced perturbations of host
targets through resistance proteins (RPs) that mediate a strong local defense response that stops pathogen growth. Both primary
and secondary immune responses in plants depend on germ line-encoded PRRs and RPs. During induction of local immune responses,
systemic immune responses also become activated, which predispose plants to become more resistant to subsequent pathogen attacks.
This review gives an update on recent findings that have enhanced our understanding of plant innate immunity and the arms
race between plants and their pathogens.
Received 24 June 2007; received after revision 18 July 2007; accepted 15 August 2007 相似文献
1000.
Hunt MC Greene S Hultenby K Svensson LT Engberg S Alexson SE 《Cellular and molecular life sciences : CMLS》2007,64(12):1558-1570
Acyl-CoA thioesterases (ACOTs) catalyze the hydrolysis of acyl-CoAs to free fatty acids and coenzyme A. Recent studies have
demonstrated that one gene named Acot7, reported to be mainly expressed in brain and testis, is transcribed in several different isoforms by alternative usage of
first exons. Strongly decreased levels of ACOT7 activity and protein in both mitochondria and cytosol was reported in patients
diagnosed with fatty acid oxidation defects, linking ACOT7 function to regulation of fatty acid oxidation in other tissues.
In this study, we have identified five possible first exons in mouse Acot7 (Acot7a–e) and show that all five first exons are transcribed in a tissue-specific manner. Taken together, these data show that the
Acot7 gene is expressed as multiple isoforms in a tissue-specific manner, and that expression in tissues other than brain and testis
is likely to play important roles in fatty acid metabolism.
Received 5 February 2007: received after revision 3 April 2007; accepted 19 April 2007 相似文献