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   247741篇
  免费   4971篇
  国内免费   618篇
电工技术   3791篇
综合类   173篇
化学工业   41433篇
金属工艺   10988篇
机械仪表   7820篇
建筑科学   5353篇
矿业工程   2239篇
能源动力   5855篇
轻工业   20841篇
水利工程   3331篇
石油天然气   7927篇
武器工业   25篇
无线电   23289篇
一般工业技术   51502篇
冶金工业   41982篇
原子能技术   6823篇
自动化技术   19958篇
  2022年   2159篇
  2021年   3309篇
  2020年   2477篇
  2019年   3020篇
  2018年   5191篇
  2017年   5207篇
  2016年   5618篇
  2015年   3520篇
  2014年   5371篇
  2013年   11907篇
  2012年   8165篇
  2011年   9929篇
  2010年   7941篇
  2009年   8457篇
  2008年   8469篇
  2007年   8155篇
  2006年   6808篇
  2005年   6183篇
  2004年   5644篇
  2003年   5473篇
  2002年   5191篇
  2001年   5053篇
  2000年   4714篇
  1999年   4783篇
  1998年   12816篇
  1997年   8886篇
  1996年   6654篇
  1995年   4770篇
  1994年   4136篇
  1993年   4366篇
  1992年   3163篇
  1991年   3171篇
  1990年   3016篇
  1989年   3006篇
  1988年   3016篇
  1987年   2652篇
  1986年   2685篇
  1985年   3004篇
  1984年   2803篇
  1983年   2629篇
  1982年   2385篇
  1981年   2378篇
  1980年   2455篇
  1979年   2412篇
  1978年   2435篇
  1977年   2675篇
  1976年   3230篇
  1975年   2241篇
  1974年   2112篇
  1973年   2226篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
83.
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   
84.
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   
85.
N. Boukortt  S. Patan&#;  G. Crupi 《SILICON》2020,12(7):1585-1591
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra  相似文献   
86.
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   
87.
88.
89.
90.
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