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   38310篇
  免费   2667篇
  国内免费   62篇
电工技术   247篇
综合类   125篇
化学工业   9636篇
金属工艺   704篇
机械仪表   789篇
建筑科学   1190篇
矿业工程   87篇
能源动力   1021篇
轻工业   7979篇
水利工程   369篇
石油天然气   246篇
武器工业   2篇
无线电   1587篇
一般工业技术   5777篇
冶金工业   6082篇
原子能技术   158篇
自动化技术   5040篇
  2024年   84篇
  2023年   400篇
  2022年   1045篇
  2021年   1489篇
  2020年   975篇
  2019年   1060篇
  2018年   1529篇
  2017年   1533篇
  2016年   1599篇
  2015年   1186篇
  2014年   1609篇
  2013年   3095篇
  2012年   2552篇
  2011年   2526篇
  2010年   1964篇
  2009年   1817篇
  2008年   1693篇
  2007年   1508篇
  2006年   1115篇
  2005年   921篇
  2004年   819篇
  2003年   810篇
  2002年   635篇
  2001年   516篇
  2000年   429篇
  1999年   471篇
  1998年   2174篇
  1997年   1414篇
  1996年   912篇
  1995年   508篇
  1994年   406篇
  1993年   389篇
  1992年   146篇
  1991年   116篇
  1990年   87篇
  1989年   95篇
  1988年   114篇
  1987年   107篇
  1986年   78篇
  1985年   97篇
  1984年   86篇
  1983年   56篇
  1982年   54篇
  1981年   79篇
  1980年   80篇
  1978年   41篇
  1977年   122篇
  1976年   235篇
  1975年   39篇
  1973年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
ABSTRACT

In this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory.  相似文献   
32.
Context: The administration of pharmabiotics is a promising alternative to antimicrobial drugs for the treatment and/or prevention of female urogenital infections.

Objective: To design pharmabiotic formulations including bioactive ingredients of microbial origin combined with non-microbial substances and then to evaluate the stability of the combinations during freeze-drying and storage.

Materials and methods: Different formulations including Lactobacillus gasseri CRL 1263, Lactobacillus salivarius CRL 1328, salivaricin CRL 1328 (a bacteriocin) and non-microbial compounds (lactose, inulin and ascorbic acid) were assayed, and the ingredients were freeze-dried together or separately. The formulations were stored in gelatin capsules at 4?°C for 360?d.

Results: The viability of lactobacilli was affected to different extents depending on the strains and on the formulations assayed. L. salivarius and ascorbic acid were successfully combined only after the freeze-drying process. Salivaricin activity was not detected in formulations containing L. gasseri. However, when combined with ascorbic acid, lactose, inulin or L. salivarius, the bacteriocin maintained its activity for 360?d. The selected microorganisms proved to be compatible for their inclusion in multi-strain formulations together with lactose, inulin and ascorbic acid. Salivaricin could be included only in a L. salivarius CRL 1328 single-strain formulation together with non-microbial substances.

Conclusions: This study provides new insights into the design of urogenital pharmabiotics combining beneficial lactobacilli, salivaricin CRL 1328 and compounds with different functionalities.  相似文献   
33.
34.
35.
36.
Water Resources Management - This paper aims to evaluate the possibility of using non-utilized hydraulic energy in urban water distribution systems. For this purpose, the viability and possible...  相似文献   
37.
38.
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   
39.
40.
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