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   12816篇
  免费   541篇
  国内免费   23篇
电工技术   131篇
综合类   6篇
化学工业   2309篇
金属工艺   250篇
机械仪表   243篇
建筑科学   751篇
矿业工程   29篇
能源动力   365篇
轻工业   1122篇
水利工程   124篇
石油天然气   32篇
无线电   948篇
一般工业技术   2334篇
冶金工业   2550篇
原子能技术   63篇
自动化技术   2123篇
  2023年   69篇
  2022年   84篇
  2021年   224篇
  2020年   189篇
  2019年   230篇
  2018年   253篇
  2017年   264篇
  2016年   280篇
  2015年   244篇
  2014年   363篇
  2013年   781篇
  2012年   608篇
  2011年   880篇
  2010年   575篇
  2009年   554篇
  2008年   686篇
  2007年   605篇
  2006年   517篇
  2005年   481篇
  2004年   403篇
  2003年   376篇
  2002年   361篇
  2001年   205篇
  2000年   215篇
  1999年   239篇
  1998年   451篇
  1997年   346篇
  1996年   268篇
  1995年   212篇
  1994年   196篇
  1993年   187篇
  1992年   134篇
  1991年   107篇
  1990年   131篇
  1989年   113篇
  1988年   87篇
  1987年   104篇
  1986年   102篇
  1985年   129篇
  1984年   115篇
  1983年   106篇
  1982年   83篇
  1981年   85篇
  1980年   66篇
  1979年   70篇
  1978年   61篇
  1977年   75篇
  1976年   100篇
  1975年   48篇
  1974年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A Couette-type torsion wire surface shear viscometer was used to measure the apparent interfacial shear viscosity of pH 7 (I=0.05 M) buffered solutions of sodium caseinate in contact with sunflower oil. The sunflower oil contained 1% fat crystals in either the β or β′ polymorphic form, or was crystal free. In all cases, the fat crystals increased the interfacial shear viscosity synergistically, with the β′ crystals causing the biggest increase. Substituting the protein for a small-molecule surfactant (Tween-40) showed that this was not simply due to the protein lowering the interfacial tension. Sedimentation studies of the different fat crystal slurries suggested that the extent of the interfacial shear viscosity increase was related to the strength of crystal-crystal interactions in the oil phase. It seems likely that when protein is present at the interface, it fixes the adsorbed layer of fat crystals to the cross-linked protein film at the interface. When this film was sheared, the strength of the crystal-crystal interactions in the oil phase became important. However, when Tween-40 was in the aqueous phase instead of the protein, the crystal-crystal interactions were not relevant, presumably because the Tween-40 interfacial film simply flowed around the adsorbed crystals  相似文献   
993.
The empirical focus is two small adjacent estates in West Newcastle; one with a mostly Bangladeshi population, the other white. The contrasts between them form the basis for a discussion of low housing demand and high turnover; forms of social exclusion; community and ethnicity. The Bangladeshi population experience exclusion from housing. Their estate has high demand and low turnover. Their housing options are highly constrained by a combination of low income and fear of crime and harassment. On the other hand they are comparatively well integrated into the local economy and a strong community structure. In contrast, the white population has more housing choice as a result of low demand, but exhibit greater exclusion from the labour market and from 'civil society'. Recent proposals to restructure the housing of the West End could increase housing opportunities for the Bangladeshis, but their impact on the white estate is more uncertain.  相似文献   
994.
In recent years the repeated compromise and loss of personal information, from a variety of sources, both public and private, have led to the issue of privacy being increasingly in the public eye. Concurrently public policy developments in line with the UK's Transformational Government agenda have led to ever greater amounts of personal information being made available electronically, and with greater levels of access being explored in order to exploit greater efficiencies in the delivery of public services. Such a rise in both public concern of the security of their data and the levels of access being afforded to improve efficiency has sometimes been seen as dichotomous. This article looks at some of these underlying concerns to suggest some of the issues that need to be addressed when considering privacy in a public policy context, and examines the dangers of retrofitting privacy as an afterthought, and hence the importance of privacy by design.  相似文献   
995.
Cameroon is blessed with abundant water resources. Rapid population increase, unplanned urbanisation, intensive industrial and socio-economic development have led to poor and unsustainable management of these resources. Integrated Water Resources Management (IWRM) is a promising approach in ensuring sustainable management of Cameroon’s water resources. It entails management of water for various purposes and not for a single purpose which therefore involves different stake holders aiming at achieving sustainable water resources management. This paper seeks to evaluate recent efforts to implement in IWRM in Cameroon by examining the institutional framework for IWRM in Cameroon, conditions for the implementation of IWRM and proposes reforms for improving IWRM in Cameroon. The paper concludes that reforms such as public participation at local council levels, recognition of water as both an economic and a social good, putting IWRM within the larger context of Integrated Natural Resource Management (INRM) and the exploitation of mathematical models within hydrological basins will improve IWRM in Cameroon.  相似文献   
996.
997.
Using peroxide, γ-, and UV-irradiation, free radical addition reactions of hexafluoropropene to diethers and to 18-crown-6 have been investigated and mono-, di-, and poly-adducts have been obtained. Factors influencing these additions, especially polar characteristics of intermediate radicals, have been elucidated. Adducts of 18-crown-6 retain a capacity to complex to alkali-metal ions.  相似文献   
998.
999.
The effects of dry extrusion of mixtures of rapeseed and soya bean on total and individual glucosinolates, selected glucosinolate hydrolysis products, myrosinase, sinapine and tannins have been compared with those of more conventional processing, e.g. lime treatment, micronisation and ammoniation. Extrusion at 150°C effectively inactivated myrosinase but had relatively little effect on glucosinolate content unless chemicals were added before extrusion; the most effective combination, 5% alkali+1% ferrous sulphate, reduced the total glucosinolate content by 80%. Under the latter conditions very high (>30 μmol g?1 defatted meal) levels of nitriles were produced, leading to the suggestion that nitriles in addition to oxazolidine-2-thione and isothiocyanates be used to monitor the effectiveness of processing techniques. None of the extrusion conditions showed any significant effect on reducing sinapine or tannin contents. In view of the chemical data presented, and the probable adverse effects which the processing conditions selected have on the nutritional value of the processed meal it seems unlikely that extrusion will play a significant role in rapeseed detoxification.  相似文献   
1000.
A widespread assumption in theories of emotion is that there exists a small set of basic emotions. From a biological perspective, this idea is manifested in the belief that there might be neurophysiological and anatomical substrates corresponding to the basic emotions. From a psychological perspective, basic emotions are often held to be the primitive building blocks of other, nonbasic emotions. The content of such claims is examined, and the results suggest that there is no coherent nontrivial notion of basic emotions as the elementary psychological primitives in terms of which other emotions can be explained. Thus, the view that there exist basic emotions out of which all other emotions are built, and in terms of which they can be explained, is questioned, raising the possibility that this position is an article of faith rather than an empirically or theoretically defensible basis for the conduct of emotion research. This suggests that perhaps the notion of basic emotions will not lead to significant progress in the field. An alternative approach to explaining the phenomena that appear to motivate the postulation of basic emotions is presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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