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   470964篇
  免费   16057篇
  国内免费   6770篇
电工技术   14806篇
技术理论   9篇
综合类   9267篇
化学工业   73262篇
金属工艺   19963篇
机械仪表   18642篇
建筑科学   17609篇
矿业工程   4750篇
能源动力   12159篇
轻工业   40327篇
水利工程   5608篇
石油天然气   12824篇
武器工业   1059篇
无线电   56591篇
一般工业技术   83895篇
冶金工业   67170篇
原子能技术   10033篇
自动化技术   45817篇
  2022年   5950篇
  2021年   8382篇
  2020年   6221篇
  2019年   6073篇
  2018年   8534篇
  2017年   8846篇
  2016年   8481篇
  2015年   8082篇
  2014年   11593篇
  2013年   22970篇
  2012年   16730篇
  2011年   20136篇
  2010年   16419篇
  2009年   17492篇
  2008年   17838篇
  2007年   17264篇
  2006年   15673篇
  2005年   13983篇
  2004年   12435篇
  2003年   12074篇
  2002年   11969篇
  2001年   11767篇
  2000年   10848篇
  1999年   10758篇
  1998年   20172篇
  1997年   14966篇
  1996年   11998篇
  1995年   9553篇
  1994年   8618篇
  1993年   8097篇
  1992年   6453篇
  1991年   6093篇
  1990年   5969篇
  1989年   5746篇
  1988年   5514篇
  1987年   4683篇
  1986年   4717篇
  1985年   5386篇
  1984年   4937篇
  1983年   4640篇
  1982年   4210篇
  1981年   4379篇
  1980年   4046篇
  1979年   4111篇
  1978年   3945篇
  1977年   4494篇
  1976年   5543篇
  1975年   3445篇
  1974年   3338篇
  1973年   3357篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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   
92.
93.
94.
95.
Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique.  相似文献   
96.
  Qing  Xu  Bin  Yu  Yang  Zhan  Wei  Zhao  Yu  Zheng  Jun  Ji  Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...  相似文献   
97.
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.  相似文献   
98.
The machining of metal surfaces and the application of functional coatings by means of a flexible tool (a rotating wire brush) is considered. Frictional cladding may be applied on metal-cutting machines by means of simple attachments or manual angle grinders.  相似文献   
99.
100.
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