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   425967篇
  免费   7494篇
  国内免费   1383篇
电工技术   7957篇
综合类   394篇
化学工业   65092篇
金属工艺   14677篇
机械仪表   12205篇
建筑科学   12453篇
矿业工程   968篇
能源动力   11411篇
轻工业   45826篇
水利工程   3410篇
石油天然气   1854篇
武器工业   13篇
无线电   56250篇
一般工业技术   80353篇
冶金工业   75292篇
原子能技术   5678篇
自动化技术   41011篇
  2021年   2990篇
  2020年   2094篇
  2019年   2719篇
  2018年   4352篇
  2017年   4409篇
  2016年   4703篇
  2015年   3928篇
  2014年   6287篇
  2013年   20477篇
  2012年   10898篇
  2011年   15559篇
  2010年   12031篇
  2009年   13548篇
  2008年   14628篇
  2007年   14983篇
  2006年   13290篇
  2005年   12380篇
  2004年   11908篇
  2003年   11605篇
  2002年   11260篇
  2001年   11413篇
  2000年   10512篇
  1999年   10965篇
  1998年   24183篇
  1997年   17757篇
  1996年   14039篇
  1995年   11126篇
  1994年   9887篇
  1993年   9453篇
  1992年   7213篇
  1991年   6877篇
  1990年   6474篇
  1989年   6179篇
  1988年   5924篇
  1987年   4947篇
  1986年   4889篇
  1985年   6097篇
  1984年   5731篇
  1983年   4915篇
  1982年   4590篇
  1981年   4551篇
  1980年   4285篇
  1979年   4155篇
  1978年   3851篇
  1977年   4610篇
  1976年   6164篇
  1975年   3198篇
  1974年   3069篇
  1973年   2945篇
  1972年   2351篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation.  相似文献   
52.
53.
54.
55.
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies.  相似文献   
56.
57.
58.
59.
60.
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