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   412019篇
  免费   6554篇
  国内免费   1376篇
电工技术   7693篇
综合类   349篇
化学工业   61780篇
金属工艺   14288篇
机械仪表   11880篇
建筑科学   11645篇
矿业工程   868篇
能源动力   11126篇
轻工业   43810篇
水利工程   3310篇
石油天然气   1835篇
武器工业   13篇
无线电   55395篇
一般工业技术   76629篇
冶金工业   75076篇
原子能技术   5568篇
自动化技术   38684篇
  2021年   2651篇
  2019年   2436篇
  2018年   3838篇
  2017年   3905篇
  2016年   4150篇
  2015年   3427篇
  2014年   5715篇
  2013年   19293篇
  2012年   10210篇
  2011年   14687篇
  2010年   11295篇
  2009年   12891篇
  2008年   13929篇
  2007年   14290篇
  2006年   12786篇
  2005年   11970篇
  2004年   11586篇
  2003年   11290篇
  2002年   10922篇
  2001年   11140篇
  2000年   10281篇
  1999年   10783篇
  1998年   24051篇
  1997年   17611篇
  1996年   13924篇
  1995年   10993篇
  1994年   9779篇
  1993年   9370篇
  1992年   7122篇
  1991年   6793篇
  1990年   6403篇
  1989年   6106篇
  1988年   5866篇
  1987年   4890篇
  1986年   4839篇
  1985年   5983篇
  1984年   5603篇
  1983年   4832篇
  1982年   4496篇
  1981年   4448篇
  1980年   4209篇
  1979年   4080篇
  1978年   3773篇
  1977年   4551篇
  1976年   6107篇
  1975年   3116篇
  1974年   3011篇
  1973年   2890篇
  1972年   2318篇
  1971年   2003篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
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   
44.
45.
46.
47.
48.
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   
49.
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   
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