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   415313篇
  免费   6956篇
  国内免费   1374篇
电工技术   7763篇
综合类   370篇
化学工业   61827篇
金属工艺   14397篇
机械仪表   11931篇
建筑科学   11831篇
矿业工程   897篇
能源动力   11194篇
轻工业   44125篇
水利工程   3334篇
石油天然气   1714篇
武器工业   13篇
无线电   55813篇
一般工业技术   78247篇
冶金工业   75018篇
原子能技术   5611篇
自动化技术   39558篇
  2021年   2748篇
  2019年   2527篇
  2018年   4064篇
  2017年   4107篇
  2016年   4399篇
  2015年   3615篇
  2014年   5959篇
  2013年   19730篇
  2012年   10499篇
  2011年   15025篇
  2010年   11555篇
  2009年   13179篇
  2008年   14227篇
  2007年   14582篇
  2006年   12996篇
  2005年   12150篇
  2004年   11727篇
  2003年   11447篇
  2002年   11050篇
  2001年   11244篇
  2000年   10355篇
  1999年   10848篇
  1998年   24081篇
  1997年   17654篇
  1996年   13954篇
  1995年   11014篇
  1994年   9814篇
  1993年   9391篇
  1992年   7032篇
  1991年   6707篇
  1990年   6324篇
  1989年   6010篇
  1988年   5761篇
  1987年   4825篇
  1986年   4789篇
  1985年   5976篇
  1984年   5569篇
  1983年   4800篇
  1982年   4460篇
  1981年   4414篇
  1980年   4167篇
  1979年   4051篇
  1978年   3752篇
  1977年   4516篇
  1976年   6071篇
  1975年   3098篇
  1974年   2987篇
  1973年   2871篇
  1972年   2299篇
  1971年   1975篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
44.
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   
45.
46.
47.
48.
49.
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   
50.
In this work, nanofiber scaffolds for surface drug delivery applications were obtained by electrospinning poly(N-vinylcaprolactam) (PNVCL) and its blends with poly(ε-caprolactone) and poly(N-vinylcaprolactam)-b-poly(ε-caprolactone). The process parameters to obtain smooth and beadless PNVCL fibers were optimized. The average fibers diameter was less than 1 μm, and it was determined by scanning electron microscopy analyses. Their affinity toward water was evaluated by measuring the contact angle with water. The ketoprofen release behavior from the fibers was analyzed using independent and model-dependent approaches. The low values of the release exponent (n < 0.5) obtained for 20 and 42 °C, indicating a Fickian diffusion mechanism for all formulations. Dissolution efficiencies (DEs) revealed the effect of polymer composition, methodology used in the electrospinning process, and temperature on the release rate of ketoprofen. PNVCL/poly(N-vinylcaprolactam)-b-poly(ε-caprolactone)-based nanofibers showed greater ability to control the in vitro release of ketoprofen, in view of reduced kinetic constant and DE, making this material promising system for controlling release of hydrophobic drugs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48472.  相似文献   
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