全文获取类型
收费全文 | 464512篇 |
免费 | 8927篇 |
国内免费 | 2367篇 |
专业分类
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 |
出版年
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.
ABSTRACTIn 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.
Akopdzhanyan T. G. Chemagina E. A. Borovinskaya I. P. 《Russian Journal of Non-Ferrous Metals》2020,61(6):686-690
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.
ABSTRACTThis 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.
Zavadiuk S.V. Loboda P.I. Soloviova T.O. Trosnikova I.Iu. Karasevska O.P. 《Powder Metallurgy and Metal Ceramics》2020,59(1-2):22-28
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.
Esteban Vera Pingitore María Silvina Juárez Tomás Birgitt Wiese 《Drug development and industrial pharmacy》2015,41(6):942-952
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.