首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1455篇
  免费   4篇
  国内免费   14篇
系统科学   108篇
丛书文集   2篇
教育与普及   10篇
理论与方法论   39篇
现状及发展   215篇
研究方法   194篇
综合类   792篇
自然研究   113篇
  2020年   6篇
  2019年   7篇
  2018年   10篇
  2017年   15篇
  2016年   8篇
  2015年   11篇
  2014年   10篇
  2013年   37篇
  2012年   110篇
  2011年   225篇
  2010年   39篇
  2009年   8篇
  2008年   96篇
  2007年   98篇
  2006年   87篇
  2005年   121篇
  2004年   109篇
  2003年   100篇
  2002年   94篇
  2001年   17篇
  2000年   19篇
  1999年   20篇
  1998年   13篇
  1997年   6篇
  1996年   7篇
  1995年   14篇
  1993年   5篇
  1992年   20篇
  1991年   7篇
  1990年   9篇
  1989年   6篇
  1988年   7篇
  1987年   5篇
  1986年   6篇
  1985年   11篇
  1984年   5篇
  1983年   5篇
  1982年   9篇
  1979年   9篇
  1978年   4篇
  1977年   4篇
  1976年   4篇
  1974年   9篇
  1970年   7篇
  1969年   5篇
  1967年   3篇
  1966年   3篇
  1965年   5篇
  1957年   4篇
  1956年   3篇
排序方式: 共有1473条查询结果,搜索用时 15 毫秒
971.
Cauchy's sum theorem is a prototype of what is today a basic result on the convergence of a series of functions in undergraduate analysis. We seek to interpret Cauchy’s proof, and discuss the related epistemological questions involved in comparing distinct interpretive paradigms. Cauchy’s proof is often interpreted in the modern framework of a Weierstrassian paradigm. We analyze Cauchy’s proof closely and show that it finds closer proxies in a different modern framework.  相似文献   
972.
A new species of Pseudolepturges from Bolivia is described and illustrated; a key to the species is also provided. Based on the similar body size, orange-yellowish colour, behaviour, and close co-occurrence on a Triplaris americana tree, we suggest that Pseudolepturges triplarinus sp. nov. is a mimic of the ant Pseudomyrmex triplarinus.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:6DF38C64-6986-4A79-8D9A-645DA89149F2  相似文献   

973.
ORP2 is a ubiquitously expressed OSBP-related protein previously implicated in endoplasmic reticulum (ER)—lipid droplet (LD) contacts, triacylglycerol (TG) metabolism, cholesterol transport, adrenocortical steroidogenesis, and actin-dependent cell dynamics. Here, we characterize the role of ORP2 in carbohydrate and lipid metabolism by employing ORP2-knockout (KO) hepatoma cells (HuH7) generated by CRISPR-Cas9 gene editing. The ORP2-KO and control HuH7 cells were subjected to RNA sequencing, analyses of Akt signaling, carbohydrate and TG metabolism, the extracellular acidification rate, and the lipidome, as well as to transmission electron microscopy. The loss of ORP2 resulted in a marked reduction of active phosphorylated Akt(Ser473) and its target Glycogen synthase kinase 3β(Ser9), consistent with defective Akt signaling. ORP2 was found to form a physical complex with the key controllers of Akt activity, Cdc37, and Hsp90, and to co-localize with Cdc37 and active Akt(Ser473) at lamellipodial plasma membrane regions, in addition to the previously reported ER–LD localization. ORP2-KO reduced glucose uptake, glycogen synthesis, glycolysis, mRNA-encoding glycolytic enzymes, and SREBP-1 target gene expression, and led to defective TG synthesis and storage. ORP2-KO did not reduce but rather increased ER–LD contacts under basal culture conditions and interfered with their expansion upon fatty acid loading. Together with our recently published work (Kentala et al. in FASEB J 32:1281–1295, 2018), this study identifies ORP2 as a new regulatory nexus of Akt signaling, cellular energy metabolism, actin cytoskeletal function, cell migration, and proliferation.  相似文献   
974.
We carried out whole-genome homozygosity mapping, gene expression analysis and DNA sequencing in individuals with isolated mitochondrial ATP synthase deficiency and identified disease-causing mutations in TMEM70. Complementation of the cell lines of these individuals with wild-type TMEM70 restored biogenesis and metabolic function of the enzyme complex. Our results show that TMEM70 is involved in mitochondrial ATP synthase biogenesis in higher eukaryotes.  相似文献   
975.
We conducted a genome-wide association study of 299,983 tagging SNPs for chronic lymphocytic leukemia (CLL) and performed validation in two additional series totaling 1,529 cases and 3,115 controls. We identified six previously unreported CLL risk loci at 2q13 (rs17483466; P = 2.36 x 10(-10)), 2q37.1 (rs13397985, SP140; P = 5.40 x 10(-10)), 6p25.3 (rs872071, IRF4; P = 1.91 x 10(-20)), 11q24.1 (rs735665; P = 3.78 x 10(-12)), 15q23 (rs7176508; P = 4.54 x 10(-12)) and 19q13.32 (rs11083846, PRKD2; P = 3.96 x 10(-9)). These data provide the first evidence for the existence of common, low-penetrance susceptibility to a hematological malignancy and new insights into disease causation in CLL.  相似文献   
976.
Germline mutations in STK11 (also known as LKB1) are found in individuals with Peutz-Jeghers syndrome (PJS) manifesting with gastrointestinal polyps that contain a prominent stromal component. Epithelia in polyps of Stk11(+/-) mice can retain a functional copy of Stk11 (refs. 2,3), and loss of heterozygosity is not an obligate feature of human polyps, raising the possibility of non-epithelial origins in tumorigenesis. Here we show that either monoallelic or biallelic loss of murine Stk11 limited to Tagln-expressing mesenchymal cells results in premature postnatal death as a result of gastrointestinal polyps indistinguishable from those in PJS. Stk11-deficient mesenchymal cells produced less TGFbeta, and defective TGFbeta signaling to epithelial cells coincided with epithelial proliferation. We also noted TGFbeta signaling defects in polyps of individuals with PJS, suggesting that the identified stromal-derived mechanism of tumor suppression is also relevant in PJS.  相似文献   
977.
Systemic lupus erythematosus (SLE) is a common systemic autoimmune disease with complex etiology but strong clustering in families (lambda(S) = approximately 30). We performed a genome-wide association scan using 317,501 SNPs in 720 women of European ancestry with SLE and in 2,337 controls, and we genotyped consistently associated SNPs in two additional independent sample sets totaling 1,846 affected women and 1,825 controls. Aside from the expected strong association between SLE and the HLA region on chromosome 6p21 and the previously confirmed non-HLA locus IRF5 on chromosome 7q32, we found evidence of association with replication (1.1 x 10(-7) < P(overall) < 1.6 x 10(-23); odds ratio = 0.82-1.62) in four regions: 16p11.2 (ITGAM), 11p15.5 (KIAA1542), 3p14.3 (PXK) and 1q25.1 (rs10798269). We also found evidence for association (P < 1 x 10(-5)) at FCGR2A, PTPN22 and STAT4, regions previously associated with SLE and other autoimmune diseases, as well as at > or =9 other loci (P < 2 x 10(-7)). Our results show that numerous genes, some with known immune-related functions, predispose to SLE.  相似文献   
978.
We identified and replicated an association between ITGAM (CD11b) at 16p11.2 and risk of systemic lupus erythematosus (SLE) in 3,818 individuals of European descent. The strongest association was at a nonsynonymous SNP, rs1143679 (P = 1.7 x 10(-17), odds ratio = 1.78). We further replicated this association in two independent samples of individuals of African descent (P = 0.0002 and 0.003; overall meta-analysis P = 6.9 x 10(-22)). The genetic association between ITGAM and SLE implicates the alpha(M)beta2-integrin adhesion pathway in disease development.  相似文献   
979.
Core formation by gravitational segregation allegedly released sufficient interior heat to melt the Earth. Analysis of the energetics, which compare gravitational potential energy (Ug) of a fictitious,...  相似文献   
980.
Fluid-rock interactions alter the geochemical, isotopic, petrographic and physical character of host rocks, producing a permanent record of hydrothermal activity. Maps of altered rock properties show r...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号