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   260431篇
  免费   8127篇
  国内免费   3477篇
电工技术   7611篇
技术理论   2篇
综合类   4230篇
化学工业   37333篇
金属工艺   11158篇
机械仪表   9506篇
建筑科学   8714篇
矿业工程   2883篇
能源动力   6332篇
轻工业   18348篇
水利工程   2764篇
石油天然气   6755篇
武器工业   531篇
无线电   34866篇
一般工业技术   44934篇
冶金工业   48376篇
原子能技术   4188篇
自动化技术   23504篇
  2023年   1418篇
  2022年   2551篇
  2021年   3809篇
  2020年   2894篇
  2019年   3029篇
  2018年   4033篇
  2017年   4203篇
  2016年   4062篇
  2015年   3951篇
  2014年   5617篇
  2013年   11539篇
  2012年   8481篇
  2011年   10520篇
  2010年   8581篇
  2009年   9262篇
  2008年   9498篇
  2007年   9454篇
  2006年   9271篇
  2005年   8313篇
  2004年   7344篇
  2003年   6868篇
  2002年   6465篇
  2001年   6734篇
  2000年   6457篇
  1999年   7133篇
  1998年   17092篇
  1997年   11559篇
  1996年   9057篇
  1995年   6716篇
  1994年   5830篇
  1993年   5581篇
  1992年   3803篇
  1991年   3617篇
  1990年   3471篇
  1989年   3245篇
  1988年   2962篇
  1987年   2354篇
  1986年   2398篇
  1985年   2664篇
  1984年   2342篇
  1983年   2083篇
  1982年   1929篇
  1981年   2059篇
  1980年   1811篇
  1979年   1668篇
  1978年   1663篇
  1977年   2026篇
  1976年   2714篇
  1975年   1431篇
  1974年   1371篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
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   
52.
53.
54.
55.
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   
56.
57.
Bochkareva  N. I.  Ivanov  A. M.  Klochkov  A. V.  Kogotkov  V. S.  Rebane  Yu. T.  Virko  M. V.  Shreter  Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode...  相似文献   
58.
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.  相似文献   
59.
Mechanical durability of extruded fish feed must be optimized to lower economic losses as well as emission of organic matter to aquatic environments. The glass transition hypothesis for viscoelastic biopolymers is demonstrated and confirmed experimentally to be valid for extruded fish feed pellets. It is proposed and demonstrated that it is important to avoid early glass transition onset, to optimize the obtained mechanical durability. From the proposed glass transition hypothesis, immediate process relevance to the pre-drying transport mechanism is demonstrated. Furthermore, measured mechanical durability is found to range from 1.5 to 5.0% loss, for different combinations of drying parameters.  相似文献   
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