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   11136篇
  免费   1020篇
  国内免费   13篇
电工技术   87篇
综合类   11篇
化学工业   2738篇
金属工艺   139篇
机械仪表   350篇
建筑科学   505篇
矿业工程   27篇
能源动力   242篇
轻工业   2249篇
水利工程   86篇
石油天然气   20篇
无线电   815篇
一般工业技术   2184篇
冶金工业   749篇
原子能技术   26篇
自动化技术   1941篇
  2024年   39篇
  2023年   162篇
  2022年   138篇
  2021年   373篇
  2020年   323篇
  2019年   313篇
  2018年   444篇
  2017年   455篇
  2016年   566篇
  2015年   478篇
  2014年   617篇
  2013年   1135篇
  2012年   985篇
  2011年   779篇
  2010年   577篇
  2009年   560篇
  2008年   591篇
  2007年   517篇
  2006年   467篇
  2005年   313篇
  2004年   282篇
  2003年   250篇
  2002年   242篇
  2001年   151篇
  2000年   129篇
  1999年   114篇
  1998年   160篇
  1997年   136篇
  1996年   93篇
  1995年   92篇
  1994年   83篇
  1993年   77篇
  1992年   45篇
  1991年   33篇
  1990年   23篇
  1989年   23篇
  1988年   27篇
  1987年   19篇
  1986年   27篇
  1985年   31篇
  1984年   25篇
  1983年   19篇
  1982年   23篇
  1981年   18篇
  1980年   20篇
  1979年   24篇
  1978年   14篇
  1976年   19篇
  1974年   13篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The purpose of the study proposed in this paper is to evaluate the Spanish public university websites dedicated to the European Higher Education Area (EHEA). To do so, the quality of these resources has been analysed in the light of data provided by a series of indicators grouped in seven criteria, most of which were used to determine what information is made available and in what way. The criteria used in our analysis are: visibility, authority, updatedness, accesibility, correctness and completeness, quality assessment and navigability. All in all, the results allow us to carry out an overall diagnosis of the situation and also provide us with information about the situation at each university, thus revealing their main strengths, namely authority and navegability, and also their chief shortcomings: updatedness, accessibility and quality assessment. In this way it is possible to detect the best practices in each of the aspects evaluated so that they can serve as an example and guide for universities with greater deficiencies and thus help them to improve their EHEA websites.  相似文献   
22.
We report of a theoretical study on quasi-one dimensional unconventional charge density wave (UCDW) driven by electron–phonon interaction. Within mean field theory, we find that the wavevector dependence of the coupling leads to a momentum dependent single particle gap on the Fermi surface. The presence of small energy single particle excitations around the gap nodes significantly changes the optical conductivity compared to the conventional CDW result. In addition to that, the collective phase excitation arising from fluctuation of the order parameter leads to further qualitative changes of the conductivity and results in an effective mass that is nonmonotonic in temperature.   相似文献   
23.
INTRODUCTION AND DEVELOPMENT: Multiple sclerosis (ME) is an inflammatory disease of the myelin of the central nervous system, the origin of which is still unknown. Genetic, infectious, immunological and environmental factors have all been blamed, but none of these factors on their own can explain the whole spectrum of this disease. Of the environmental factors, fat in the diet has given rise to most discussion. At the present time, it is known that polyunsaturated essential fatty acids form a part of biological membranes. A relationship has been found between the dietary fat consumed and the plasma levels and cell membrane content. CONCLUSIONS: The possible immuno-modulation function of these fatty acids justify rigorous evaluation of this hypothesis.  相似文献   
24.
A multiresolution analysis of digital gray-level images is presented. A gray-level multi-scale framework is determined from two main assumptions: the gray scale is binary at the finest spatial resolution, and the gray levels of composed regions are obtained additively. In order to interrelate the gray-level histograms of the same image at different resolutions, probabilistic linear models are developed, which are then applied for estimation. Linear-optimization theory is used as a way of constructing such models. A general procedure for image processing is sketched, based on gray-level estimation. A versatile algorithm for nonlinear filtering is derived. Some examples of prospective applications are given.This work was partially supported by grant TIC91-646 from the DGYCIT of the Spanish Government.  相似文献   
25.
26.
The first stages of nickel electrodeposition on amorphous carbon and polycrystalline silver substrates have been studied under galvanostatic conditions. An island growth mode is observed on the two types of substrate. For equivalent conditions the cluster density is higher on silver substrates than on carbon substrates. Dissolution of some nickel clusters is observed a short time after the onset of electrolysis on carbon substrates. This is confirmed by the evolution of the current efficiency and the evolution of the metal surface cluster density as a function of the quantity of electricity.  相似文献   
27.
28.
András Nagy 《Polymer Bulletin》1985,14(3-4):259-264
Summary The Kennedy-Smith plot routinely used for the characterization of end-reactive (telechelic) polyisobutylenes has been recast to increase its accuracy and thus to increase its diagnostic value for the compositional analysis of telechelic polymers containing chromophores. A detailed error estimation is given. The plotting method and error limits are shown for representative mono-, di-, and tri-ended telechelic polyisobutylenes.  相似文献   
29.
30.
The defective regulation of the secretory chloride channel and the accelerated rate of sodium absorption in the airway epithelia of patients with cystic fibrosis (CF) contribute to the dehydration of airway secretions which is responsible for secondary damage in the respiratory tract. The sodium-blocker amiloride inhibits sodium absorption depending on the dosage of the drug. This effect is documented by means of measuring transepithelial potential difference which is decreased following to inhalative amiloride administration in CF patients. Clinical long term efficiency has been shown to be probable, but has to be confirmed. Investigation in this field is difficult, because there are some other important factors which influence viscosity of mucus. The use of amiloride can best be evaluated, if it is given immediately after birth. However, the answer to some important questions has to be found before.  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