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   341191篇
  免费   4119篇
  国内免费   1228篇
电工技术   5867篇
综合类   2642篇
化学工业   48134篇
金属工艺   14867篇
机械仪表   11441篇
建筑科学   8217篇
矿业工程   1627篇
能源动力   7469篇
轻工业   26299篇
水利工程   3786篇
石油天然气   4247篇
武器工业   68篇
无线电   43680篇
一般工业技术   65703篇
冶金工业   49006篇
原子能技术   5664篇
自动化技术   47821篇
  2021年   2038篇
  2019年   2035篇
  2018年   17575篇
  2017年   16569篇
  2016年   13481篇
  2015年   2907篇
  2014年   4254篇
  2013年   11447篇
  2012年   9584篇
  2011年   17990篇
  2010年   15005篇
  2009年   13224篇
  2008年   15240篇
  2007年   16120篇
  2006年   7907篇
  2005年   8277篇
  2004年   7951篇
  2003年   7849篇
  2002年   6883篇
  2001年   6554篇
  2000年   6339篇
  1999年   6304篇
  1998年   14291篇
  1997年   10293篇
  1996年   8154篇
  1995年   6420篇
  1994年   5721篇
  1993年   5590篇
  1992年   4562篇
  1991年   4233篇
  1990年   4048篇
  1989年   3779篇
  1988年   3631篇
  1987年   3170篇
  1986年   3065篇
  1985年   3610篇
  1984年   3382篇
  1983年   3031篇
  1982年   2850篇
  1981年   2951篇
  1980年   2761篇
  1979年   2648篇
  1978年   2499篇
  1977年   2946篇
  1976年   3555篇
  1975年   2316篇
  1974年   2312篇
  1973年   2318篇
  1972年   1849篇
  1971年   1745篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The identification of adequate wastewater treatment for small communities is a complex problem since it demands a combination of data from different sources, such as aspects of the community and landscape, the receiving environment and the available wastewater treatment technologies. The Catalan Water Agency (Agència Catalana de l'Aigua) considered using an EDSS (Environmental Decision Support System) as a tool to help water managers select the most adequate treatment for the urban wastewater of nearly 3,500 small communities in Catalonia (Spain). From that moment, EDSS was applied to all the river basins in Catalonia. In this paper the authors present the results obtained for the 76 small communities located in one of these river basins: the Fluvia River Basin. The characteristics of the community used in the reasoning process of the EDSS, the list of selected wastewater treatment alternatives, the technical environmental justification for the selected treatments and the reasons for discarding, favouring or disadvantaging them are presented. Finally, some results for the Fluvia River Basin are compared with those obtained in other Catalan river basins with different characteristics in order to evaluate which are the significant features in identifying adequate wastewater treatments.  相似文献   
82.
83.
Graduates of clinical training programs were surveyed to determine the degree to which they have found various graduate school experiences useful in their professional work. Samples of academic clinical psychologists and practicing clinical psychologists reported time allocation and preference for various professional activities, perceived usefulness of various theoretical orientations, and the influence on their current professional work of 19 different graduate training topics. Results suggest that where differences exist, academic clinical psychologists are generally more satisfied with Boulder-model-inspired scientific training than are clinical practitioners. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
84.
Book review     
  相似文献   
85.
Dynamic-viscosity measurements are reported for liquid mixtures in the system formed by n-butyraldehyde and isobutyraldehyde.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 321–322, February, 1985.  相似文献   
86.
There are some foods that contain mutagenic or carcinogenic agents, some of which occur naturally and others that may be formed during preparation or cooking. Several foods such as legumes, also contain natural antimutagens and/or anticarcinogens. Lupine is one such legume that contains high amounts of protein (40%) and oils (14%). About 90 species of lupine have been reported throughout Mexico. However, the use of this crop as a source of food has been limited by the presence of antinutritional agents such as phenolic compounds (PC), carbohydrates (CH) and quinolizidinic alkaloids (Qas). It has also been suggested that consuming these compounds can affect human health and may even reduce the risk of disease. The objective of this work was to determine the effect of PC, CH and Qas, isolated and quantified from Lupinus campestris on the mutagenicity of 1-nitropyrene (1-NP) as a model mutagen and we used the Salmonella typhimurium tester strain YG1024 by the Kado microsuspension method. The results indicate that L. campestris seeds have 11 mg (+)catechin equivalent g(-1) seed coat; 120.3 mg g(-1) seeds and 2.13 mg g(-1) seeds of PC, CH and Qas, respectively. 1-NP mutagenicity was inhibited by 86% for PC, 76% for CH and 75% for Qas at concentrations of 200, 512 and 13.6 microg/tube, respectively.  相似文献   
87.
We analyze the non-Fermi liquid behavior in the proximity of the quantum phase transition induced by the strong polarization of the electrons due to local magnetic moments in Ni x Pd1-x alloys. We use the renormalization group approach introduced by Hertz–Mi11is–Moriya (HMM) to estimate the temperature dependence of the electrical resistivity for the case of three dimensional itinerant ferromagnets. We study two different cases, namely, the clean and disordered ferromagnets, and argue that at the present time more experimental data are needed to decide if the HMM theory can accurately describe the physical properties in Ni x Pd1-x alloys.  相似文献   
88.
89.
The operation of a torsional oscillator for detection, of flow-driven textural transitions in, 3He-A is described. The detection technique, tracking the shift of the resonant frequency of the torsional oscillator, allows us to observe textural changes and the presence of vortices in zero magnetic field. It relies on. the anisotropic superfluid density of 3He-A and its change due to reorientation of the Î-texture caused by counterflow.  相似文献   
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