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   1011篇
  免费   110篇
  国内免费   8篇
电工技术   16篇
综合类   14篇
化学工业   363篇
金属工艺   22篇
机械仪表   21篇
建筑科学   43篇
矿业工程   6篇
能源动力   21篇
轻工业   141篇
水利工程   10篇
石油天然气   9篇
武器工业   2篇
无线电   59篇
一般工业技术   181篇
冶金工业   93篇
原子能技术   4篇
自动化技术   124篇
  2024年   4篇
  2023年   13篇
  2022年   45篇
  2021年   70篇
  2020年   48篇
  2019年   32篇
  2018年   42篇
  2017年   38篇
  2016年   53篇
  2015年   45篇
  2014年   47篇
  2013年   72篇
  2012年   86篇
  2011年   81篇
  2010年   59篇
  2009年   66篇
  2008年   46篇
  2007年   41篇
  2006年   39篇
  2005年   33篇
  2004年   25篇
  2003年   23篇
  2002年   16篇
  2001年   19篇
  2000年   7篇
  1999年   5篇
  1998年   6篇
  1997年   7篇
  1996年   11篇
  1995年   5篇
  1994年   3篇
  1993年   7篇
  1992年   5篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1976年   2篇
  1974年   3篇
  1973年   1篇
  1971年   1篇
排序方式: 共有1129条查询结果,搜索用时 15 毫秒
101.
A new classification of ternary reciprocal systems is proposed taking into account the number of thermal effects in the thermograms of complete conversion points. The classification is useful for general evaluation of the liquid surface of the systems.  相似文献   
102.
Identity and overall acceptance of two types of sour rye bread   总被引:1,自引:0,他引:1  
Response surface methodology was employed to study the influence of four recipe variables (wheat: rye flour ratio, bread acidity, ash content of rye flour and sodium chloride content) on the identity and overall acceptance of two rye bread types (soft and crisp rye bread). The subjects ( n = 79) rated attribute intensities, the extent to which the salient sensory properties and the overall sample corresponded to their expectations of rye bread, and the overall acceptance (pleasantness and purchase intentions). The acidity and ash content contributed the most to the extent to which a sample met subjects' expectations. The NaCl content was not critical. Consumer acceptance was affected by ash content, and by the interactions, NaCl content × acidity and wheat:rye ratio × ash content. The non-significance of NaCl content should encourage the baking industry to put low-salt rye products on the market.  相似文献   
103.
A compact, internally heated, catalytic reactor is demonstrated for the low-temperature oxidation of carbon monoxide. Carbon nanofibres were grown on carbon felt and used as a support material for Au/TiO2 catalysts. The carbon composite plays two roles; as a support material for the catalyst and for providing heat to the reaction by the Joule effect. The internal heating offers a stable reactor system with quick temperature response at relatively low energy input. Comparison between external and internal heating shows higher conversion of CO in the low-temperature range when using internal heating. The Au/TiO2 catalyst supported on the carbon-carbon composite shows good stability at 250°C.  相似文献   
104.
105.
The paper deals with jitter measurement in telecommunication networks based on plesiochronous (PDH) or synchronous (SDH) digital hierarchies. The attention is mostly focused on PDH/SDH analysers compliant to the ITU-T recommendations, the accuracy of which seems to be unsatisfying for both designers and manufacturers. Trying to give an answer to this problem, a digital signal-processing method was already proposed by the author. It succeeded in improving jitter measurement accuracy by avoiding the use of timing recovery circuitry, always needed, on the contrary, in the aforementioned analysers.The method is here optimised with the aim both of automating jitter performance test of network elements that operate at the PDH bit rate of 140 Mbit/s and the SDH bit rate of 155 Mbit/s, and further enhancing the accuracy on jitter estimates. In particular, an innovative procedure for automatically recovering the binary information conveyed by the jittered signal under analysis is introduced, and a proper strategy for carrying out instantaneous jitter measurements at uniform time intervals is developed.After a brief outline of the old version of the method, the proposed enhancements are described in detail. Then, the performance of the optimised method is assessed through many laboratory tests on emulated signals, the results of which are given and discussed. At the end, the outcomes of real automatic tests, conducted on PDH/SDH-based equipment produced by Marconi Sud S.p.A., are also presented.  相似文献   
106.
Combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used for investigation of local composition gradients in the hard-phases of cermets. XRD revealed distribution of lattice parameters in hard-phase grains, from which the composition gradients in the hard-phases were estimated using an appropriate microstructure model. This microstructure model was build with the aid of SEM micrographs, which were taken with back-scattered electrons (BSE) and completed by the registration of the electron back-scatter diffraction (EBSD) patterns and characteristic X-ray spectra. SEM/BSE yielded the first information about the spatial distribution of elements in individual hard-phase grains, SEM/EBSD about the morphology, the size and the size distribution of these grains. The final interpretation of the distribution of lattice parameters, which was obtained from the X-ray line profile analysis, was done with the aid of the local elemental analysis that was performed using SEM with the energy dispersive analysis of the characteristic X-ray spectra (EDX) and the known dependence of the lattice parameters on concentration.  相似文献   
107.
The present study evaluated the effect of artificial gravity loading on transporter-mediated uptake and release of L-glutamate using the inhibitors of glutamate transporters as tools. The competitive nontransportable, DL-threo-beta-benzyloxyaspartate (DL-TBOA), and transportable, DL-threo-beta-hydroxyaspartate (DL-THA), inhibitors were demonstrated to better inhibit the L-[14C]glutamate uptake under centrifuge-induced hypergravity compared with the normal gravity control. The effect of DL-TBOA on depolarization-induced carrier-mediated L-[14C]glutamate release also increased after hypergravity loading in Na+- and low [Na+] NMDG- supplemented media. 10 µM DL-TBOA-induced decrease in L-[14C]glutamate release in Na+ — supplemented medium was 15.2±2.2 % in the control experiments and 26.2±3.9 % after centrifuge-induced loading (P≤0,05) and in low [Na+] medium was 37.0±2.5 % and 45.0±3.4 %, respectively.  相似文献   
108.
A training program, based on procedural justice theory, was developed for teaching supervisors to take effective disciplinary action with employees. Canadian supervisors of unionized employees were randomly assigned to the training (n?=?35) or the control group (n?=?36). Analyses of variance revealed that both supervisory self-efficacy and outcome expectancies were significantly higher in the training than in the control conditions. Following simulated role-play exercises derived from organizational incidents, both unionized employees and disciplinary subject matter experts (managers, union officials, and attorneys) rated the trained supervisors higher on disciplinary fairness behavior than the supervisors in the control group. Self-efficacy was found to mediate the relationship between training and perceptions of disciplinary fairness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
109.
Graphene has been long thought of as a perfect barrier material due to its impermeability to all gases as well as mechanical and chemical durability. Moreover, graphene layers are transparent and conductive, significantly widening the field of potential applications beyond simple barrier coatings. However, it is very challenging to realize such barriers on a macro­scopic scale as immaculate large area films are not available. In this work, a highly effective oxygen gas barrier made from multiple layers of chemical vapor deposited graphene is presented. The individual graphene layers are stacked using a modified polymer‐assisted transfer method, avoiding polymer residue yielding an oxygen‐tight arrangement. A stack of three layers of graphene transmitted 6.9 cm3 m−2 d−1 of O2 which corresponds to 1.10 × 10−17 cm3 cm/cm2 s (cm Hg) when normalized to thickness and pressure. This is several orders of magnitude better than any macroscale graphene coating reported to date and performs on a level that can compete with most modern coatings while being much thinner and conductive.  相似文献   
110.
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