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   1602470篇
  免费   26942篇
  国内免费   7206篇
电工技术   35222篇
综合类   6515篇
化学工业   277015篇
金属工艺   66178篇
机械仪表   45924篇
建筑科学   48115篇
矿业工程   11785篇
能源动力   50642篇
轻工业   124266篇
水利工程   16222篇
石油天然气   38214篇
武器工业   162篇
无线电   200057篇
一般工业技术   299266篇
冶金工业   208688篇
原子能技术   34520篇
自动化技术   173827篇
  2021年   15844篇
  2020年   12148篇
  2019年   14886篇
  2018年   18592篇
  2017年   18125篇
  2016年   22877篇
  2015年   17792篇
  2014年   29001篇
  2013年   88537篇
  2012年   38276篇
  2011年   52966篇
  2010年   45479篇
  2009年   53234篇
  2008年   48601篇
  2007年   46384篇
  2006年   46598篇
  2005年   42257篇
  2004年   43623篇
  2003年   43308篇
  2002年   41948篇
  2001年   39164篇
  2000年   37225篇
  1999年   37247篇
  1998年   59716篇
  1997年   47991篇
  1996年   40940篇
  1995年   33946篇
  1994年   31379篇
  1993年   31369篇
  1992年   26930篇
  1991年   24134篇
  1990年   24383篇
  1989年   23463篇
  1988年   21956篇
  1987年   20215篇
  1986年   19554篇
  1985年   22849篇
  1984年   22685篇
  1983年   20628篇
  1982年   19544篇
  1981年   19748篇
  1980年   18362篇
  1979年   18740篇
  1978年   18028篇
  1977年   18418篇
  1976年   20342篇
  1975年   16186篇
  1974年   15631篇
  1973年   15742篇
  1972年   13207篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter.  相似文献   
132.
133.
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures.  相似文献   
134.
135.
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs.  相似文献   
136.
137.
138.
The principles and design of “active” self‐propelling particles that can convert energy, move directionally on their own, and perform a certain function is an emerging multidisciplinary research field, with high potential for future technologies. A simple and effective technique is presented for on‐demand steering of self‐propelling microdiodes that move electroosmotically on water surface, while supplied with energy by an external alternating (AC) field. It is demonstrated how one can control remotely the direction of diode locomotion by electronically modifying the applied AC signal. The swimming diodes change their direction of motion when a wave asymmetry (equivalent to a DC offset) is introduced into the signal. The data analysis shows that the ability to control and reverse the direction of motion is a result of the electrostatic torque between the asymmetrically polarized diodes and the ionic charges redistributed in the vessel. This novel principle of electrical signal‐coded steering of active functional devices, such as diodes and microcircuits, can find applications in motile sensors, MEMs, and microrobotics.  相似文献   
139.
140.
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