全文获取类型
收费全文 | 5246篇 |
免费 | 30篇 |
国内免费 | 41篇 |
专业分类
系统科学 | 89篇 |
丛书文集 | 269篇 |
教育与普及 | 250篇 |
理论与方法论 | 23篇 |
现状及发展 | 409篇 |
研究方法 | 593篇 |
综合类 | 3682篇 |
自然研究 | 2篇 |
出版年
2022年 | 10篇 |
2018年 | 10篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 38篇 |
2013年 | 31篇 |
2012年 | 298篇 |
2011年 | 351篇 |
2010年 | 125篇 |
2009年 | 108篇 |
2008年 | 399篇 |
2007年 | 356篇 |
2006年 | 448篇 |
2005年 | 494篇 |
2004年 | 325篇 |
2003年 | 285篇 |
2002年 | 240篇 |
2001年 | 205篇 |
2000年 | 294篇 |
1999年 | 105篇 |
1998年 | 49篇 |
1997年 | 34篇 |
1996年 | 24篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 30篇 |
1992年 | 24篇 |
1991年 | 19篇 |
1990年 | 28篇 |
1989年 | 34篇 |
1988年 | 18篇 |
1987年 | 15篇 |
1986年 | 33篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 30篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1971年 | 16篇 |
1970年 | 28篇 |
1966年 | 15篇 |
1959年 | 68篇 |
1958年 | 124篇 |
1957年 | 91篇 |
1956年 | 66篇 |
1955年 | 88篇 |
1954年 | 84篇 |
1948年 | 25篇 |
排序方式: 共有5317条查询结果,搜索用时 515 毫秒
141.
也许你还没有留意到,在我们的生活中悄然出现了“拼”一族,拼什么?不是拼命,不是血拼,而是拼合、拼盘,也就是正在流行的“拼”起来做事,拼车、拼房、拼班、拼卡、拼饭……既节约资源又其乐融融,他们有滋有味的“拼盘”生活已然成为了一种时尚。 相似文献
142.
Compton G 《Population trends》2008,(132):26-33
The Office for National Statistics conducted a major census field test in May and June 2007 as part of the planning and preparation for the next census of population and housing in England and Wales in 2011. The 2007 Census Test was a large scale test covering approximately 100,000 household in five local authorities (LAs) selected to reflect a range of geographic conditions and social characteristics. Within England the Test covered parts of Bath and North East Somerset, Camden, Liverpool and Stoke on Trent. In Wales the Test took place in Carmarthenshire. The selected LAs were chosen to provide a varied cross section of the population and types of housing that would be covered in a full census. This article summarises the evaluation results and, where decided, decisions for 2011 on four key aspects of the Test: delivery method - post-out compared with hand delivery; inclusion of an income question; outsourcing recruitment, training and pay; and liaison with LAs. 相似文献
143.
中朝板块北缘志留纪海岛的发现 总被引:2,自引:0,他引:2
在内蒙古达尔罕茂明安联合旗北部巴特敖包地区发现了志留纪的海岸带及其底栖无脊椎动物化石(层孔虫、日射与床板珊瑚等),证实当时该地发育一个位于中朝古板块北缘大陆棚上的小海岛,将其命名为巴特岛.该岛的基部由奥陶纪火成岩组成,长、短轴分别为610和200m,现今呈北东-南西向延伸.志留纪罗德洛世(距今约420Ma)的地层围绕该岛分布,产状向四周倾状.巴特岛的南缘(背风)发育皮壳状生物,栖息在火成岩顶面并被 相似文献
144.
145.
Saenz HL Engel P Stoeckli MC Lanz C Raddatz G Vayssier-Taussat M Birtles R Schuster SC Dehio C 《Nature genetics》2007,39(12):1469-1476
The bacterial genus Bartonella comprises 21 pathogens causing characteristic intraerythrocytic infections. Bartonella bacilliformis is a severe pathogen representing an ancestral lineage, whereas the other species are benign pathogens that evolved by radial speciation. Here, we have used comparative and functional genomics to infer pathogenicity genes specific to the radiating lineage, and we suggest that these genes may have facilitated adaptation to the host environment. We determined the complete genome sequence of Bartonella tribocorum by shotgun sequencing and functionally identified 97 pathogenicity genes by signature-tagged mutagenesis. Eighty-one pathogenicity genes belong to the core genome (1,097 genes) of the radiating lineage inferred from genome comparison of B. tribocorum, Bartonella henselae and Bartonella quintana. Sixty-six pathogenicity genes are present in B. bacilliformis, and one has been lost by deletion. The 14 pathogenicity genes specific for the radiating lineage encode two laterally acquired type IV secretion systems, suggesting that these systems have a role in host adaptability. 相似文献
146.
147.
Alcaïs A Alter A Antoni G Orlova M Nguyen VT Singh M Vanderborght PR Katoch K Mira MT Vu HT Ngyuen TH Nguyen NB Moraes M Mehra N Schurr E Abel L 《Nature genetics》2007,39(4):517-522
Host genetics has an important role in leprosy, and variants in the shared promoter region of PARK2 and PACRG were the first major susceptibility factors identified by positional cloning. Here we report the linkage disequilibrium mapping of the second linkage peak of our previous genome-wide scan, located close to the HLA complex. In both a Vietnamese familial sample and an Indian case-control sample, the low-producing lymphotoxin-alpha (LTA)+80 A allele was significantly associated with an increase in leprosy risk (P = 0.007 and P = 0.01, respectively). Analysis of an additional case-control sample from Brazil and an additional familial sample from Vietnam showed that the LTA+80 effect was much stronger in young individuals. In the combined sample of 298 Vietnamese familial trios, the odds ratio of leprosy for LTA+80 AA/AC versus CC subjects was 2.11 (P = 0.000024), which increased to 5.63 (P = 0.0000004) in the subsample of 121 trios of affected individuals diagnosed before 16 years of age. In addition to identifying LTA as a major gene associated with early-onset leprosy, our study highlights the critical role of case- and population-specific factors in the dissection of susceptibility variants in complex diseases. 相似文献
148.
Loss of GLIS2 causes nephronophthisis in humans and mice by increased apoptosis and fibrosis 总被引:4,自引:0,他引:4
149.
Holst F Stahl PR Ruiz C Hellwinkel O Jehan Z Wendland M Lebeau A Terracciano L Al-Kuraya K Jänicke F Sauter G Simon R 《Nature genetics》2007,39(5):655-660
Using an Affymetrix 10K SNP array to screen for gene copy number changes in breast cancer, we detected a single-gene amplification of the ESR1 gene, which encodes estrogen receptor alpha, at 6q25. A subsequent tissue microarray analysis of more than 2,000 clinical breast cancer samples showed ESR1 amplification in 20.6% of breast cancers. Ninety-nine percent of tumors with ESR1 amplification showed estrogen receptor protein overexpression, compared with 66.6% cancers without ESR1 amplification (P < 0.0001). In 175 women who had received adjuvant tamoxifen monotherapy, survival was significantly longer for women with cancer with ESR1 amplification than for women with estrogen receptor-expressing cancers without ESR1 amplification (P = 0.023). Notably, we also found ESR1 amplification in benign and precancerous breast diseases, suggesting that ESR1 amplification may be a common mechanism in proliferative breast disease and a very early genetic alteration in a large subset of breast cancers. 相似文献
150.
St Onge RP Mani R Oh J Proctor M Fung E Davis RW Nislow C Roth FP Giaever G 《Nature genetics》2007,39(2):199-206
Systematic genetic interaction studies have illuminated many cellular processes. Here we quantitatively examine genetic interactions among 26 Saccharomyces cerevisiae genes conferring resistance to the DNA-damaging agent methyl methanesulfonate (MMS), as determined by chemogenomic fitness profiling of pooled deletion strains. We constructed 650 double-deletion strains, corresponding to all pairings of these 26 deletions. The fitness of single- and double-deletion strains were measured in the presence and absence of MMS. Genetic interactions were defined by combining principles from both statistical and classical genetics. The resulting network predicts that the Mph1 helicase has a role in resolving homologous recombination-derived DNA intermediates that is similar to (but distinct from) that of the Sgs1 helicase. Our results emphasize the utility of small molecules and multifactorial deletion mutants in uncovering functional relationships and pathway order. 相似文献