全文获取类型
收费全文 | 32010篇 |
免费 | 390篇 |
国内免费 | 526篇 |
专业分类
系统科学 | 621篇 |
丛书文集 | 772篇 |
教育与普及 | 266篇 |
理论与方法论 | 93篇 |
现状及发展 | 9588篇 |
研究方法 | 925篇 |
综合类 | 20287篇 |
自然研究 | 374篇 |
出版年
2014年 | 352篇 |
2013年 | 376篇 |
2012年 | 611篇 |
2011年 | 1044篇 |
2010年 | 484篇 |
2009年 | 511篇 |
2008年 | 765篇 |
2007年 | 800篇 |
2006年 | 782篇 |
2005年 | 735篇 |
2004年 | 688篇 |
2003年 | 640篇 |
2002年 | 591篇 |
2001年 | 1074篇 |
2000年 | 1025篇 |
1999年 | 919篇 |
1998年 | 502篇 |
1997年 | 487篇 |
1996年 | 468篇 |
1995年 | 443篇 |
1994年 | 385篇 |
1993年 | 334篇 |
1992年 | 654篇 |
1991年 | 579篇 |
1990年 | 576篇 |
1989年 | 474篇 |
1988年 | 522篇 |
1987年 | 459篇 |
1986年 | 385篇 |
1985年 | 511篇 |
1984年 | 368篇 |
1983年 | 304篇 |
1980年 | 347篇 |
1979年 | 688篇 |
1978年 | 580篇 |
1977年 | 551篇 |
1976年 | 474篇 |
1975年 | 532篇 |
1974年 | 666篇 |
1973年 | 579篇 |
1972年 | 588篇 |
1971年 | 701篇 |
1970年 | 927篇 |
1969年 | 728篇 |
1968年 | 625篇 |
1967年 | 653篇 |
1966年 | 596篇 |
1965年 | 433篇 |
1958年 | 402篇 |
1957年 | 307篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
351.
Global change: hydrocarbon-driven warming 总被引:3,自引:0,他引:3
Dickens GR 《Nature》2004,429(6991):513-515
352.
353.
Minimum information about a microarray experiment (MIAME)-toward standards for microarray data. 总被引:36,自引:0,他引:36
A Brazma P Hingamp J Quackenbush G Sherlock P Spellman C Stoeckert J Aach W Ansorge C A Ball H C Causton T Gaasterland P Glenisson F C Holstege I F Kim V Markowitz J C Matese H Parkinson A Robinson U Sarkans S Schulze-Kremer J Stewart R Taylor J Vilo M Vingron 《Nature genetics》2001,29(4):365-371
Microarray analysis has become a widely used tool for the generation of gene expression data on a genomic scale. Although many significant results have been derived from microarray studies, one limitation has been the lack of standards for presenting and exchanging such data. Here we present a proposal, the Minimum Information About a Microarray Experiment (MIAME), that describes the minimum information required to ensure that microarray data can be easily interpreted and that results derived from its analysis can be independently verified. The ultimate goal of this work is to establish a standard for recording and reporting microarray-based gene expression data, which will in turn facilitate the establishment of databases and public repositories and enable the development of data analysis tools. With respect to MIAME, we concentrate on defining the content and structure of the necessary information rather than the technical format for capturing it. 相似文献
354.
Nuclear transfer into mouse zygotes 总被引:6,自引:0,他引:6
355.
Chiang C Jacobsen JC Ernst C Hanscom C Heilbut A Blumenthal I Mills RE Kirby A Lindgren AM Rudiger SR McLaughlan CJ Bawden CS Reid SJ Faull RL Snell RG Hall IM Shen Y Ohsumi TK Borowsky ML Daly MJ Lee C Morton CC MacDonald ME Gusella JF Talkowski ME 《Nature genetics》2012,44(4):390-7, S1
We defined the genetic landscape of balanced chromosomal rearrangements at nucleotide resolution by sequencing 141 breakpoints from cytogenetically interpreted translocations and inversions. We confirm that the recently described phenomenon of 'chromothripsis' (massive chromosomal shattering and reorganization) is not unique to cancer cells but also occurs in the germline, where it can resolve to a relatively balanced state with frequent inversions. We detected a high incidence of complex rearrangements (19.2%) and substantially less reliance on microhomology (31%) than previously observed in benign copy-number variants (CNVs). We compared these results to experimentally generated DNA breakage-repair by sequencing seven transgenic animals, revealing extensive rearrangement of the transgene and host genome with similar complexity to human germline alterations. Inversion was the most common rearrangement, suggesting that a combined mechanism involving template switching and non-homologous repair mediates the formation of balanced complex rearrangements that are viable, stably replicated and transmitted unaltered to subsequent generations. 相似文献
356.
贺亮才 《萍乡高等专科学校学报》2010,27(1):37-40
诞生于清朝末年的萍乡煤矿,是早期洋务运动的产物,是中国最早采用西方先进生产技术和管理的现代化矿井,位列中国近代工业十大厂矿之一。本文从中国民族产业发展和经济社会转型层面,全新探析了萍乡煤矿创建和发展在中国近代工业经济史上的重要历史意义,以及安源精神的最初形成与发展。 相似文献
357.
Purification and cloning of amyloid precursor protein beta-secretase from human brain 总被引:40,自引:0,他引:40
Sinha S Anderson JP Barbour R Basi GS Caccavello R Davis D Doan M Dovey HF Frigon N Hong J Jacobson-Croak K Jewett N Keim P Knops J Lieberburg I Power M Tan H Tatsuno G Tung J Schenk D Seubert P Suomensaari SM Wang S Walker D Zhao J McConlogue L John V 《Nature》1999,402(6761):537-540
Proteolytic processing of the amyloid precursor protein (APP) generates amyloid beta (Abeta) peptide, which is thought to be causal for the pathology and subsequent cognitive decline in Alzheimer's disease. Cleavage by beta-secretase at the amino terminus of the Abeta peptide sequence, between residues 671 and 672 of APP, leads to the generation and extracellular release of beta-cleaved soluble APP, and a corresponding cell-associated carboxy-terminal fragment. Cleavage of the C-terminal fragment by gamma-secretase(s) leads to the formation of Abeta. The pathogenic mutation K670M671-->N670L671 at the beta-secretase cleavage site in APP, which was discovered in a Swedish family with familial Alzheimer's disease, leads to increased beta-secretase cleavage of the mutant substrate. Here we describe a membrane-bound enzyme activity that cleaves full-length APP at the beta-secretase cleavage site, and find it to be the predominant beta-cleavage activity in human brain. We have purified this enzyme activity to homogeneity from human brain using a new substrate analogue inhibitor of the enzyme activity, and show that the purified enzyme has all the properties predicted for beta-secretase. Cloning and expression of the enzyme reveals that human brain beta-secretase is a new membrane-bound aspartic proteinase. 相似文献
358.
针对一类输出受干扰影响的多输入多输出社会经济系统的效益评价问题,研究了数据包络分析方法中决策单元的有效性、P-生产可能集以及原始性等概念,定义了一个可用于判断输出受随机因素影响的决策单元相对有效程度的指标,并在此基础上给出了一个新的随机DEA评价模型,分析了该模型的性质、求解方法以及与现有模型的一致性等,最后给出了一个评价案例. 相似文献
359.
第二次现代化理论与中国现代化 总被引:4,自引:0,他引:4
何传启 《世界科技研究与发展》1999,21(6):72-76
第二次现代化理论认为:人类社会的发展可分为四个,即原始,农业社会,工业社会和知识社会,第一个阶段又分为四个时期,即起步期,发展期,成就期和过渡期;从农业社会向工业社会的转移过程是第一次现代化,从工业社会向知识社会的转移过程是第二次现代化。 相似文献
360.
Two experiments have been carried out to verify the effect of ethylene on the primary attraction ofPhloeotribus scarabaeoides under both laboratory and field conditions. The experiments were based on the enhancement of ethylene production by olive branches and trunks after the application of (2-chloroethyl)phosphonic acid. Under laboratory conditions, the beetles' response was strongly stimulated on the treated branches. Under field conditions, the treatment aided the location of the olive wood by the flying beetles, and the attack density was significantly greater in the treated wood at the end of the experiment. 相似文献