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   28996篇
  免费   1278篇
  国内免费   109篇
电工技术   381篇
综合类   229篇
化学工业   5247篇
金属工艺   626篇
机械仪表   605篇
建筑科学   977篇
矿业工程   93篇
能源动力   954篇
轻工业   3983篇
水利工程   242篇
石油天然气   153篇
武器工业   6篇
无线电   2319篇
一般工业技术   4159篇
冶金工业   6355篇
原子能技术   240篇
自动化技术   3814篇
  2024年   52篇
  2023年   158篇
  2022年   526篇
  2021年   814篇
  2020年   552篇
  2019年   623篇
  2018年   709篇
  2017年   786篇
  2016年   746篇
  2015年   569篇
  2014年   876篇
  2013年   1433篇
  2012年   1275篇
  2011年   1616篇
  2010年   1176篇
  2009年   1235篇
  2008年   1129篇
  2007年   993篇
  2006年   792篇
  2005年   852篇
  2004年   921篇
  2003年   827篇
  2002年   795篇
  2001年   701篇
  2000年   550篇
  1999年   528篇
  1998年   2074篇
  1997年   1347篇
  1996年   946篇
  1995年   609篇
  1994年   488篇
  1993年   535篇
  1992年   220篇
  1991年   285篇
  1990年   224篇
  1989年   191篇
  1988年   207篇
  1987年   157篇
  1986年   163篇
  1985年   181篇
  1984年   129篇
  1983年   90篇
  1982年   121篇
  1981年   125篇
  1980年   119篇
  1979年   93篇
  1978年   80篇
  1977年   146篇
  1976年   229篇
  1975年   86篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
21.
Zhang  Xi  Wang  Xianhai  Zhao  Hongke  Ordóñez de Pablos  Patricia  Sun  Yongqiang  Xiong  Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with...  相似文献   
22.
Neat poly (lactic acid) (PLA) and PLA/cassava bagasse (CB) composites were used to produce seedling tubes by extrusion and injection molding. The tubes were buried in simulated soil, and their biodegradation was investigated by weight loss, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). After 180 days, the composites' biodegradation was higher than neat PLA material, and the higher the CB content, the higher the biodegradation, which caused fissures and voids in the material. The biodegradation of PLA/CB composites increased the phosphorus content in the soil after 180 days. Composites of PLA with CB, an abundant agro-industrial residue in Brazil, are promising because they can reduce the environmental impact due to CB's proper destination, and the composites' costs and biodegradation are faster than pure PLA material. Both the faster biodegradation of the tube and the higher P content are advantageous for seedling tubes.  相似文献   
23.
This study investigates the preparation of polyetherimide (PEI) – LaNi5 composites films for hydrogen storage. Prior to the polymer addition, LaNi5 was ball-milled at different conditions (250, 350, and 450 RPM) and annealed at 500 °C for 1 h under vacuum. The composites were produced with BM-LaNi5-350 (PEI/LaNi5-350) and annealed BM-LaNi5-350 (PEI/LaNi5-350-TT). Membranes were successfully produced through solvent casting assisted by an ultrasonic bath. The particles dispersion and the film morphology did not change after hydrogenation cycles. In the H2 sorption experiments at 43 °C and 20 bar, the films stored H2 without incubation time; both samples reached a capacity of ~0.6 wt%. The H2 sorption kinetics of PEI/LaNi5-350 was comparable to that of BM-LaNi5-350, whereas PEI/LaNi5-350-TT presented significantly slower kinetics. LaNi5 oxidation was hindered by PEI, showing that it can be explored to improve metal hydrides air resistance. The results demonstrated that PEI films filled with LaNi5 are promising materials for hydrogen storage.  相似文献   
24.
25.
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved.  相似文献   
26.
27.
28.
29.
30.
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