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   521402篇
  免费   10537篇
  国内免费   3279篇
电工技术   11850篇
技术理论   3篇
综合类   3086篇
化学工业   76896篇
金属工艺   22319篇
机械仪表   20059篇
建筑科学   15862篇
矿业工程   2753篇
能源动力   12835篇
轻工业   47299篇
水利工程   5137篇
石油天然气   5807篇
武器工业   392篇
无线电   66745篇
一般工业技术   99612篇
冶金工业   82037篇
原子能技术   7071篇
自动化技术   55455篇
  2022年   2629篇
  2021年   4651篇
  2020年   3262篇
  2019年   3528篇
  2018年   13516篇
  2017年   14293篇
  2016年   9815篇
  2015年   5574篇
  2014年   7899篇
  2013年   21668篇
  2012年   15422篇
  2011年   25734篇
  2010年   21612篇
  2009年   21739篇
  2008年   22480篇
  2007年   24525篇
  2006年   14807篇
  2005年   17246篇
  2004年   14471篇
  2003年   13684篇
  2002年   12376篇
  2001年   11964篇
  2000年   11177篇
  1999年   11724篇
  1998年   24725篇
  1997年   18155篇
  1996年   14458篇
  1995年   11434篇
  1994年   10167篇
  1993年   9623篇
  1992年   7359篇
  1991年   6973篇
  1990年   6522篇
  1989年   6197篇
  1988年   5944篇
  1987年   4928篇
  1986年   4873篇
  1985年   6010篇
  1984年   5625篇
  1983年   4855篇
  1982年   4518篇
  1981年   4465篇
  1980年   4226篇
  1979年   4089篇
  1978年   3781篇
  1977年   4558篇
  1976年   6104篇
  1975年   3122篇
  1974年   3014篇
  1973年   2899篇
排序方式: 共有10000条查询结果,搜索用时 352 毫秒
61.
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   
62.
针对基站柜式空调耗电量大的问题,创造性地使用基站分布式冷却的方式,达到精确送风,节能高效的目的.在应用实践中检验了分布式冷却系统实际节能量和应用效果,总结出分布式冷却系统应用场景和范围,为更大范围推广应用DCS分布式冷却系统提供实践依据.  相似文献   
63.
64.
65.
66.
67.
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified.  相似文献   
68.
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   
69.
70.
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