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   2936篇
  免费   164篇
  国内免费   40篇
电工技术   42篇
综合类   56篇
化学工业   814篇
金属工艺   73篇
机械仪表   98篇
建筑科学   123篇
矿业工程   10篇
能源动力   121篇
轻工业   252篇
水利工程   25篇
石油天然气   21篇
武器工业   1篇
无线电   229篇
一般工业技术   440篇
冶金工业   294篇
原子能技术   29篇
自动化技术   512篇
  2023年   24篇
  2022年   114篇
  2021年   133篇
  2020年   61篇
  2019年   71篇
  2018年   78篇
  2017年   86篇
  2016年   100篇
  2015年   81篇
  2014年   100篇
  2013年   182篇
  2012年   128篇
  2011年   206篇
  2010年   125篇
  2009年   139篇
  2008年   140篇
  2007年   122篇
  2006年   102篇
  2005年   78篇
  2004年   86篇
  2003年   105篇
  2002年   120篇
  2001年   105篇
  2000年   87篇
  1999年   58篇
  1998年   86篇
  1997年   56篇
  1996年   52篇
  1995年   34篇
  1994年   21篇
  1993年   29篇
  1992年   20篇
  1991年   15篇
  1990年   11篇
  1989年   14篇
  1988年   8篇
  1987年   6篇
  1986年   16篇
  1985年   22篇
  1984年   12篇
  1983年   13篇
  1982年   11篇
  1981年   12篇
  1980年   9篇
  1979年   6篇
  1978年   9篇
  1977年   5篇
  1976年   10篇
  1975年   4篇
  1965年   4篇
排序方式: 共有3140条查询结果,搜索用时 15 毫秒
21.
A sample of 40 adolescents (aged 13–17 yrs), some of whom had attempted suicide (n?=?20) and some who had not (n?=?20), were compared on a number of life history and psychological variables (affective and cognitive). Stepwise discriminant analyses produced 1 discriminant function (the lack of emotional significant other) that differentiated between the groups. This single discriminant function accounted for 77% of the variance in the data. These results are interpreted within the context of the early loss hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
22.
We report on potential-dependent in situ SFG and DFG spectroscopy carried out at Au(111), Au(210), polycrystalline Au, Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing CN and 4-cyanopyridine (4CP). Spectroelectrochemical work was complemented by cyclic voltammetry. The chief stress has been placed on systematising and quantifying the interaction between 4CP and CN and the attending effects on the vibrational and electronic structures of the interface. The voltammetric behaviour of the investigated electrodes, modified by the addition of 4CP to the CN electrolyte, denote changes in the CN adsorption characteristics and effects of the adsorbed CN layer on the electrodic reactivity of 4CP. The differences among the investigated electrodes can be explained in terms of their respective degrees of atomic packing or with alloying effects on the stability of adsorbed CN. The potential-dependent spectra have been analysed quantitatively with a model for the second order non linear susceptibility accounting for vibrational and electronic effects. The spectral changes induced by addition of 4CP denote interaction of the aromatic with the electrode through the CN monolayer. The non-resonant contribution yields information on the effects of 4CP on the fine structure of the bound electron density of states.  相似文献   
23.
用合成材料生产的管道及产品将越来越多,随着要求的不断提高,推动研发工作的深入开展,其技术发展也在日新月异.这些也是法规所制定的高安全标准的结果,作为最终产品是必须要服从这些法规的.  相似文献   
24.
The problems arising when there are outliers in a data set that follow a circular distribution are considered. A robust estimation of the unknown parameters is obtained using the methods of weighted likelihood and minimum disparity, each of which is defined for a general parametric family of circular data. The class of power divergence and the related residual adjustment function is investigated in order to improve the performance of the two methods which are studied for the Von Mises (circular normal) and the Wrapped Normal distributions. The techniques are illustrated via two examples based on a real data set and a Monte Carlo study, which also enables the discussion of various computational aspects.  相似文献   
25.
Here we apply the so-called Horace method for zero-dimensional schemes to error-correcting codes on complete intersections. In particular, we obtain sharper estimates on the minimum distance.  相似文献   
26.
Probabilistic Visual Cryptography Schemes   总被引:1,自引:0,他引:1  
  相似文献   
27.
28.
Vehicular sensor networks are an emerging network paradigm, suitable for various applications in vehicular environment making use of vehicles’ sensors as data sources and Inter-Vehicle Communication systems for the transmissions. We present a solution, based on vehicular sensor networks, for gathering data from a certain geographic area while satisfying with a specific delay bound. The method leverages the time interval during which the query is active in order to make the gathering process efficient, properly alternating data muling and multi-hop forwarding strategies like in delay-bounded routing protocols. Simulations show that our proposed solution succeeds in performing efficient data gathering outperforming other solutions.  相似文献   
29.
Results concerning V3Si films produced by a simple annealed multilayer technique are reported together with X-ray diffraction patterns, Auger spectroscopy, and Rutherford backscattering analysis. Low-temperature electrical resistivity measurements are discussed. It is found that the V3Si films exhibit aT 2 dependence in the temperature rangeT c T23 K and aT 2.6 dependence in the rangeT c T40 K. The normal-state resistivity in the whole temperature range (T c T600 K) is analyzed in the framework of Cote-Meisel theory. Consistent values of the saturation resistivity m and of the Debye temperature are obtained by fitting the experimental data with the Cote-Meisel expression for (T).  相似文献   
30.
The aim of this work is to demonstrate the use of a commercial finite element package, ABAQUS EXPLICIT, to model ultrasonic guided waves in structural components. The particular application of interest is modeling the interaction of a broadband vertical bending mode with transverse-type defects in railroad tracks. This topic is part of a broader project on high-speed defect detection in rails by long-range ultrasonic inspections. Reflection coefficient spectra in the 20–45 kHz range are obtained for four different sizes and three different orientations of transverse head flaws. A preliminary study of Lamb waves in a free plate helps drawing modeling guidelines for the rail.  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