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   132014篇
  免费   14535篇
  国内免费   9770篇
电工技术   10299篇
技术理论   6篇
综合类   13167篇
化学工业   18060篇
金属工艺   7882篇
机械仪表   8562篇
建筑科学   10436篇
矿业工程   4548篇
能源动力   3435篇
轻工业   15747篇
水利工程   3993篇
石油天然气   5018篇
武器工业   1675篇
无线电   14622篇
一般工业技术   12025篇
冶金工业   4589篇
原子能技术   1860篇
自动化技术   20395篇
  2024年   831篇
  2023年   2318篇
  2022年   5148篇
  2021年   6435篇
  2020年   4911篇
  2019年   3520篇
  2018年   3782篇
  2017年   4386篇
  2016年   3912篇
  2015年   6075篇
  2014年   7615篇
  2013年   8917篇
  2012年   10893篇
  2011年   11319篇
  2010年   10514篇
  2009年   9844篇
  2008年   10048篇
  2007年   9294篇
  2006年   8277篇
  2005年   6802篇
  2004年   4831篇
  2003年   3528篇
  2002年   3493篇
  2001年   3110篇
  2000年   2308篇
  1999年   1278篇
  1998年   582篇
  1997年   458篇
  1996年   403篇
  1995年   271篇
  1994年   214篇
  1993年   182篇
  1992年   172篇
  1991年   131篇
  1990年   101篇
  1989年   84篇
  1988年   53篇
  1987年   40篇
  1986年   41篇
  1985年   12篇
  1984年   19篇
  1983年   21篇
  1982年   21篇
  1981年   16篇
  1980年   41篇
  1979年   26篇
  1977年   2篇
  1964年   1篇
  1959年   15篇
  1951年   21篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
21.
22.
A novel mixed‐mode expanded bed adsorbent with anion‐exchange properties was explored with benzylamine as the functional ligand. The cellulose composite matrix, densified with stainless steel powder, was prepared with the method of water‐in‐oil suspension thermal regeneration. High activation levels of the cellulose matrix were obtained with allyl bromide because of the relative inertness of the allyl group under the conditions of the activation reaction. After the formation of the bromohydrin with N‐bromosuccinimide and coupling with benzylamine, the activated matrix was derived to function as a mixed‐mode adsorbent containing both hydrophobic and ionic groups. The protein adsorption capacity was investigated with bovine serum albumin as a model protein. The results indicated that the prepared adsorbent could bind bovine serum albumin with a high adsorption capacity, and it showed salt tolerance. Effective desorption was achieved by a pH adjustment across the isoelectric point of the protein. The interactions between the cell and adsorbent were studied, and the bioadhesion was shielded by the adjustment of the salt concentration above 0.1M. Stable fluidization in the expanded bed was obtained even in a 2% (dry weight) yeast suspension. The direct capture of target proteins from a biomass‐containing feedstock without extra dilution steps could be expected with the mixed‐mode adsorbent prepared in this work, and this would be especially appropriate for expanded bed adsorption applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
23.
对T形线路的故障测距,现有方法都是先判断故障支路,再将3端线路等效成2端线路进行测距。但在 T节点附近短路,尤其是经高阻短路时,现有的测距方法由于无法正确判别故障支路而存在一定范围的测距死区。针对上述缺陷,分别假设故障发生在某一支路,由假定正常的2段支路端的电压、电流推算求得 T节点电压和注入假定故障支路的电流,从而分别求得3个故障距离。经证明,求得的3个故障距离有且仅有1个在0和对应支路总长度之间,该距离就是真实的故障距离,故障发生在对应支路上。该方法无需事先判别故障支路即可测距,在 T节点附近经高阻故障时无测距死区。其测距精度理论上不受过渡电阻和故障类型影响,无需故障前数据,且对滤波无高要求。EMTP仿真结果表明该方法正确、有效,测距精度高。  相似文献   
24.
25.
Miloon  Kothari  宗菁 《人类居住》2005,(3):10-11
我们即将对第四届妇女大会(北京)召开十年以来的妇女发展状况进行回顾,并且要对千年发展目标的执行情况进行中期评估。因此,我们有必要对那些影响妇女日常生活的关键问题进行审视并采取相应的行动,这些问题一直被各国政府和国际社会所忽视。  相似文献   
26.
A new adaptive controller is presented here for rigid-body robotic manipulators. It is stable and robust with respect to a class of external disturbances. The robustness of the adaptive controller is established without the ‘slow-varying’ assumption and the computationally demanding regressor matrix. The control law consists of a non-adaptive PD control part and an adaptive control part. It uses two adaptive matrices to compensate two uniformly bounded coefficient matrices derived from the original dynamics. A α σ|q?|-modified adaptive law is designed to adjust the adaptive matrices. A Lyapunov-type stability analysis indicates that the closed-loop system is uniformly ultimately bounded. The tracking error and compensation error will eventually converge into a closed region, which can be made arbitrarily small by adjusting the controller parameters. Simulation results are included to demonstrate the performance of the proposed controller.  相似文献   
27.
研究了温度及气体压力对漂移室(工作于正比区)气体放大倍数的影响,温度和气体压力的变化范围分别是5 ̄40℃及90 ̄105kPa。用实验数据拟合得到了函数关系并测量了几种饱和度下函数中的参数值。  相似文献   
28.
Infiltration and localization of preferential infiltration zones at the dam abutment are measured using radioactive tracer tests of flow in boreholes,meanwhile interconnection between boreholes and the energing water points is analysed.The theory and practice of radioactive tracer synthetic detective method are described to give methods and calculation formulae used under the condition of stable flow in single well to measure permeability coefficient and hydrostatic heads.Major single hole techniques including measurement for seepage line,velocity,rate of seepage flow and relationship of recharge of groundwater in aquifers are introduced briefly.The possibilities offered by natureal tracers are analysed,uincluding electric-conduct,pH-value and temperature of water as well as stable isotopes(D,^18O) and tritium.Furthermore,the sensibilities of this theory and methods were confirmed by detecting seepage flow field of Xinanjiang Dam.  相似文献   
29.
Xia  Lei  Lv  Jiancheng  Xie  Chunzhi  Yin  Jing 《Applied Intelligence》2021,51(11):8334-8348

In the context of human-robot and robot-robot interactions, the better cooperation can be achieved by predicting the other party’s subsequent actions based on the current action of the other party. The time duration for adjustment is not sufficient provided by short term forecasting models to robots. A longer duration can by achieved by mid-term forecasting. But the mid-term forecasting models introduce the previous errors into the follow-up forecasting and amplified gradually, eventually invalidating the forecasting. A new mid-term forecasting with error suppression based on restricted Boltzmann machine(RBM) is proposed in this paper. The proposed model can suppress the error amplification by replacing the previous inputs with their features, which are retrieved by a deep belief network(DBN). Furthermore, a new mechanism is proposed to decide whether the forecasting result is accepted or not. The model is evaluated with several datasets. The reported experiments demonstrate the superior performance of the proposed model compared to the state-of-the-art approaches.

  相似文献   
30.
Cotter  John  Wang  Jing  Guldiken  Rasim 《Microsystem Technologies》2021,27(1):307-314
Microsystem Technologies - This paper introduces a method of replicating electrical circuits through a series of specific requirements as part of a design methodology referred to as Intrinsically...  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