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   464512篇
  免费   8927篇
  国内免费   2367篇
电工技术   9220篇
技术理论   5篇
综合类   1302篇
化学工业   71034篇
金属工艺   17862篇
机械仪表   13024篇
建筑科学   11052篇
矿业工程   2361篇
能源动力   10266篇
轻工业   42748篇
水利工程   4674篇
石油天然气   8355篇
武器工业   262篇
无线电   52861篇
一般工业技术   86641篇
冶金工业   96512篇
原子能技术   8666篇
自动化技术   38961篇
  2021年   4331篇
  2020年   3218篇
  2019年   4032篇
  2018年   6551篇
  2017年   6451篇
  2016年   6914篇
  2015年   5156篇
  2014年   7984篇
  2013年   20959篇
  2012年   13339篇
  2011年   17025篇
  2010年   13709篇
  2009年   14903篇
  2008年   15900篇
  2007年   15941篇
  2006年   14047篇
  2005年   12613篇
  2004年   11802篇
  2003年   11199篇
  2002年   10967篇
  2001年   11221篇
  2000年   10487篇
  1999年   11058篇
  1998年   29398篇
  1997年   20367篇
  1996年   15446篇
  1995年   11309篇
  1994年   10023篇
  1993年   10029篇
  1992年   7080篇
  1991年   6739篇
  1990年   6694篇
  1989年   6503篇
  1988年   6075篇
  1987年   5098篇
  1986年   5192篇
  1985年   5815篇
  1984年   5418篇
  1983年   4913篇
  1982年   4474篇
  1981年   4827篇
  1980年   4336篇
  1979年   4311篇
  1978年   4205篇
  1977年   4884篇
  1976年   6661篇
  1975年   3697篇
  1974年   3512篇
  1973年   3478篇
  1972年   2958篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
113.
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   
114.
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis...  相似文献   
115.
ABSTRACT

This paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR. In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs.  相似文献   
116.
Strength of Materials - The paper presents a procedure for determining the design parameters of multilayer thick-walled structures with a local load on the inner surface portion located near the...  相似文献   
117.
Powder Metallurgy and Metal Ceramics - The properties of sintered and heat-treated steels produced from the Catamold 8740 material by powder injection molding were examined. Parts made of the...  相似文献   
118.
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   
119.
120.
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