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   41199篇
  免费   1773篇
  国内免费   158篇
电工技术   509篇
综合类   250篇
化学工业   7527篇
金属工艺   859篇
机械仪表   810篇
建筑科学   1818篇
矿业工程   140篇
能源动力   1277篇
轻工业   4846篇
水利工程   401篇
石油天然气   202篇
武器工业   7篇
无线电   3114篇
一般工业技术   6442篇
冶金工业   8765篇
原子能技术   294篇
自动化技术   5869篇
  2023年   218篇
  2022年   626篇
  2021年   1010篇
  2020年   693篇
  2019年   776篇
  2018年   943篇
  2017年   978篇
  2016年   1036篇
  2015年   796篇
  2014年   1242篇
  2013年   2223篇
  2012年   1890篇
  2011年   2454篇
  2010年   1830篇
  2009年   1828篇
  2008年   1842篇
  2007年   1698篇
  2006年   1371篇
  2005年   1409篇
  2004年   1397篇
  2003年   1199篇
  2002年   1253篇
  2001年   974篇
  2000年   810篇
  1999年   758篇
  1998年   2269篇
  1997年   1531篇
  1996年   1100篇
  1995年   824篇
  1994年   659篇
  1993年   723篇
  1992年   376篇
  1991年   358篇
  1990年   362篇
  1989年   310篇
  1988年   316篇
  1987年   273篇
  1986年   247篇
  1985年   316篇
  1984年   256篇
  1983年   172篇
  1982年   182篇
  1981年   184篇
  1980年   159篇
  1979年   143篇
  1978年   116篇
  1977年   165篇
  1976年   259篇
  1975年   104篇
  1973年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
25.
26.
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   
27.
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   
28.
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   
29.
30.
The use of proteins as therapeutics has a long history and is becoming ever more common in modern medicine. While the number of protein-based drugs is growing every year, significant problems still remain with their use. Among these problems are rapid degradation and excretion from patients, thus requiring frequent dosing, which in turn increases the chances for an immunological response as well as increasing the cost of therapy. One of the main strategies to alleviate these problems is to link a polyethylene glycol (PEG) group to the protein of interest. This process, called PEGylation, has grown dramatically in recent years resulting in several approved drugs. Installing a single PEG chain at a defined site in a protein is challenging. Recently, there is has been considerable research into various methods for the site-specific PEGylation of proteins. This review seeks to summarize that work and provide background and context for how site-specific PEGylation is performed. After introducing the topic of site-specific PEGylation, recent developments using chemical methods are described. That is followed by a more extensive discussion of bioorthogonal reactions and enzymatic labeling.  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