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   447385篇
  免费   36061篇
  国内免费   21735篇
电工技术   27413篇
技术理论   28篇
综合类   29558篇
化学工业   71234篇
金属工艺   27526篇
机械仪表   28946篇
建筑科学   35888篇
矿业工程   12439篇
能源动力   12698篇
轻工业   28225篇
水利工程   8431篇
石油天然气   24842篇
武器工业   3708篇
无线电   52921篇
一般工业技术   52283篇
冶金工业   22589篇
原子能技术   4946篇
自动化技术   61506篇
  2024年   1708篇
  2023年   6374篇
  2022年   11838篇
  2021年   16388篇
  2020年   12299篇
  2019年   10098篇
  2018年   11148篇
  2017年   13126篇
  2016年   12014篇
  2015年   16195篇
  2014年   21063篇
  2013年   25906篇
  2012年   27753篇
  2011年   32948篇
  2010年   28068篇
  2009年   26664篇
  2008年   25940篇
  2007年   24560篇
  2006年   24598篇
  2005年   21528篇
  2004年   17169篇
  2003年   13949篇
  2002年   13253篇
  2001年   11720篇
  2000年   10279篇
  1999年   11478篇
  1998年   9853篇
  1997年   8268篇
  1996年   7403篇
  1995年   6038篇
  1994年   5112篇
  1993年   4649篇
  1992年   3628篇
  1991年   2660篇
  1990年   2178篇
  1989年   1820篇
  1988年   1370篇
  1987年   858篇
  1986年   676篇
  1985年   540篇
  1984年   361篇
  1983年   300篇
  1982年   285篇
  1981年   223篇
  1980年   202篇
  1979年   139篇
  1978年   72篇
  1977年   78篇
  1976年   89篇
  1973年   46篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Wang  Lijing  Chen  Jiangzhuo  Marathe  Achla 《World Wide Web》2019,22(6):2997-3020
World Wide Web - Infectious diseases such as Influenza and Ebola pose a serious threat to everyone but certain demographics and cohorts face a higher risk of infection than others. This research...  相似文献   
3.
The use of field robots can greatly decrease the amount of time, effort, and associated risk compared to if human workers were to carryout certain tasks such as disaster response. However, transportability and reliability remain two main issues for most current robot systems. To address the issue of transportability, we have developed a lightweight modularizable platform named AeroArm. To address the issue of reliability, we utilize a multimodal sensing approach, combining the use of multiple sensors and sensor types, and the use of different detection algorithms, as well as active continuous closed‐loop feedback to accurately estimate the state of the robot with respect to the environment. We used Challenge 2 of the 2017 Mohammed Bin Zayed International Robotics Competition as an example outdoor manipulation task, demonstrating the capabilities of our robot system and approach in achieving reliable performance in the fields, and ranked fifth place internationally in the competition.  相似文献   
4.
Chen  Meng  Yu  Xiaohui  Liu  Yang 《World Wide Web》2019,22(6):2901-2920
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each...  相似文献   
5.
6.
7.
8.
A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic P m 3 ¯ m upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic P m 3 ¯ m phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling.  相似文献   
9.
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active edge 1T‐MoS 2 / edge Ni ( OH ) 2 heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich edge 1T‐MoS 2 / edge Ni ( OH ) 2 sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions.  相似文献   
10.
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