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   36245篇
  免费   723篇
  国内免费   164篇
系统科学   1221篇
丛书文集   499篇
教育与普及   42篇
理论与方法论   410篇
现状及发展   15534篇
研究方法   1414篇
综合类   17559篇
自然研究   453篇
  2018年   781篇
  2017年   814篇
  2016年   573篇
  2013年   305篇
  2012年   753篇
  2011年   1829篇
  2010年   1022篇
  2009年   596篇
  2008年   1097篇
  2007年   1495篇
  2006年   652篇
  2005年   648篇
  2004年   733篇
  2003年   745篇
  2002年   657篇
  2001年   954篇
  2000年   886篇
  1999年   633篇
  1992年   604篇
  1991年   431篇
  1990年   501篇
  1989年   501篇
  1988年   468篇
  1987年   565篇
  1986年   484篇
  1985年   612篇
  1984年   495篇
  1983年   371篇
  1982年   357篇
  1981年   378篇
  1980年   478篇
  1979年   923篇
  1978年   791篇
  1977年   791篇
  1976年   624篇
  1975年   648篇
  1974年   904篇
  1973年   820篇
  1972年   830篇
  1971年   890篇
  1970年   1125篇
  1969年   884篇
  1968年   862篇
  1967年   863篇
  1966年   743篇
  1965年   509篇
  1959年   254篇
  1958年   446篇
  1957年   298篇
  1956年   259篇
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
41.
42.
The method of extracting and describing the intended behavior of software precisely has become one of the key points in the fields of software behavior's dynamic and trusted authentication. In this paper, the author proposes a specified measure of extracting SIBDS (software intended behaviors describing sets) statically from the binary executable using the software's API functions invoking, and also introduces the definition of the structure used to store the SIBDS in detail. Experimental results demonstrate that the extracting method and the storage structure definition offers three strong properties: (i) it can describe the software's intended behavior accurately; (ii) it demands a small storage expense; (iii) it provides strong capability to defend against mimicry attack.  相似文献   
43.
We tested 310,605 SNPs for association in 778 individuals with celiac disease and 1,422 controls. Outside the HLA region, the most significant finding (rs13119723; P = 2.0 x 10(-7)) was in the KIAA1109-TENR-IL2-IL21 linkage disequilibrium block. We independently confirmed association in two further collections (strongest association at rs6822844, 24 kb 5' of IL21; meta-analysis P = 1.3 x 10(-14), odds ratio = 0.63), suggesting that genetic variation in this region predisposes to celiac disease.  相似文献   
44.
Genomic alterations lead to cancer complexity and form a major hurdle for comprehensive understanding of the molecular mechanisms underlying oncogenesis. In this review, we describe recent advances in studying cancer-associated genes from a systems biology point of view. The integration of known cancer genes onto protein and signaling networks reveals the characteristics of cancer genes within networks. This approach shows that cancer genes often function as network hub proteins which are involved in many cellular processes and form focal nodes in information exchange between many signaling pathways. Literature mining allows constructing gene-gene networks, in which new cancer genes can be identified. The gene expression profiles of cancer cells are used for reconstructing gene regulatory networks. By doing so, genes which are involved in the regulation of cancer progression can be picked up from these networks, after which their functions can be further confirmed in the laboratory.  相似文献   
45.
Pancreatitis is usually inflammation of the pancreas without infection. Our understanding of pancreatitis has been built on autopsy studies, surgical biopsies and surrogate markers of inflammation and fibroses, including abdominal imaging techniques and pancreatic functional studies. However, the discovery that a number of different environmental factors and various genetic abnormalities are seen in patients with similar appearing pancreatitis phenotypes teaches us that end-stage pathology is not the disorder. Understanding complex associations and interactions requires that the components and their interactions be organized, stratified and functionally defined. Systems biology, in the broad sense, provides the approach and tools to define the complex mechanisms driving pathology. As the mathematics behind these pathways and mechanisms are defined and calibrated, the potential pathology of patients with early signs of disease can be predicted, and a number of patient-specific targets for intervention can be defined.  相似文献   
46.
Proinsulin C-peptide is known to bind specifically to cell membranes and to exert intracellular effects, but whether it is internalized in target cells is unknown. In this study, using confocal microscopy and immunostained or rhodamine-labeled peptide, we show that C-peptide is internalized and localized to the cytosol of Swiss 3T3 and HEK-293 cells. In addition, transport into nuclei was found using the labeled peptide. The internalization was followed at 37°C for up to 1 h, and was reduced at 4°C and after preincubation with pertussis toxin. Hence, it is concluded to occur via an energy-dependent, pertussis toxin-sensitive mechanism and without detectable degradation within the experimental time course. Surface plasmon resonance measurements demonstrated binding of HEK-293 cell extract components to C-peptide, and subsequent elution of bound material revealed the components to be intracellular proteins. The identification of C-peptide cellular internalization, intracellular binding proteins, absence of rapid subsequent C-peptide degradation and apparent nuclear internalization support a maintained activity similar to that of an intracrine peptide hormone. Hence, the data suggest the possibility of one further C-peptide site of action. Received 31 October 2006; received after revision 27 December 2006; accepted 30 December 2006  相似文献   
47.
1 Results In the coordination system by using complexation with organic ligand, the ff emission of lanthanide(Ⅲ) (Ln(Ⅲ)) is induced the excitation energy transfer form the organic chromophore under the light-irradiation. However, there are not so much number of reports to discuss the energy relaxation mechanism in such complexes with Ln(Ⅲ). Recently, we succeeded firstly to estimate the rate constant of the energy transfer between the ligand and Ln(Ⅲ) in Pr(Ⅲ)-phenanthroline analogs[1]. Here, we will di...  相似文献   
48.
49.
50.
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