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   90898篇
  免费   7634篇
  国内免费   4107篇
电工技术   5714篇
技术理论   2篇
综合类   5804篇
化学工业   14035篇
金属工艺   4959篇
机械仪表   5233篇
建筑科学   6738篇
矿业工程   1871篇
能源动力   2648篇
轻工业   7109篇
水利工程   1822篇
石油天然气   3881篇
武器工业   682篇
无线电   12078篇
一般工业技术   11687篇
冶金工业   4619篇
原子能技术   1029篇
自动化技术   12728篇
  2024年   370篇
  2023年   1372篇
  2022年   2576篇
  2021年   3574篇
  2020年   2503篇
  2019年   2111篇
  2018年   2362篇
  2017年   2808篇
  2016年   2459篇
  2015年   3401篇
  2014年   4460篇
  2013年   5679篇
  2012年   6061篇
  2011年   6775篇
  2010年   5875篇
  2009年   5677篇
  2008年   5604篇
  2007年   5362篇
  2006年   5145篇
  2005年   4197篇
  2004年   2864篇
  2003年   2358篇
  2002年   2377篇
  2001年   2030篇
  2000年   1915篇
  1999年   1939篇
  1998年   1826篇
  1997年   1576篇
  1996年   1412篇
  1995年   1185篇
  1994年   923篇
  1993年   761篇
  1992年   607篇
  1991年   462篇
  1990年   385篇
  1989年   298篇
  1988年   252篇
  1987年   182篇
  1986年   152篇
  1985年   139篇
  1984年   100篇
  1983年   75篇
  1982年   68篇
  1981年   59篇
  1980年   52篇
  1979年   35篇
  1978年   32篇
  1977年   32篇
  1976年   54篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C).  相似文献   
12.
In this note, we revisit the problem of global practical stabilization for planar linear systems subject to actuator saturation and input additive disturbances. A parameterized linear state feedback law is designed such that, by tuning the value of the parameter, all trajectories of the closed-loop system converge to an arbitrarily small neighborhood of the origin in a finite time and remain in there.  相似文献   
13.
This paper is a tutorial on GrÖbner bases and a survey on the applications of GrÖbner bases in the broad field of signals and systems. A reasonably detailed review is given of several fundamental theoretical issues that occur in the use of GrÖbner bases in multidimensional signals and systems applications. These topics include the primeness of multivariate polynomial matrices, multivariate unimodular polynomial matrix completion, and prime factorization of multivariate polynomial matrices. A brief review is also presented on the wide-ranging applications of GrÖbner bases in multidimensional as well as one-dimensional circuits, networks, control, coding, signals, and systems and other related areas like robotics and applied mechanics. The impact and scope of GrÖbner bases in signals and systems are highlighted with respect to what has already been accomplished as a stepping stone to expanding future research.   相似文献   
14.
In this paper, a wavelet transform-based approach is proposed to detect the occurrence of islanding events in distributed generation systems. Thanks to time–frequency localization capabilities exhibited by wavelet transform, the approach embedded with this transform technique has grasped the appearance of the islanding event in a highly effective manner. Moreover, for those regions which are in need of a better visualization, the proposed approach would serve as an efficient aid such that the mains power disconnection can be better distinguished. To validate the feasibility of this approach, the method has been validated through several scenarios. Test results supported the effectiveness of the method for the application considered.  相似文献   
15.
研究了稳定ZrO_2和部份稳定ZrO_2对β″-Al_2O_3陶瓷的强化和韧化作用,观察了不同种类、不同含量的ZrO_2对β″-Al_2O_3陶瓷的显微结构、力学性能和电导率的影响,探讨了β″-Al_2O_3的韧化机理。  相似文献   
16.
The width of the transition layer between the crystalline and amorphous zones in nylon 1010 was determined by SAXS with point collimation and long-slit collimation, respectively. The width of the transition layer, E, was found to be 1.7 nm. The results show that the width of the transition layer is independent of crystallinity.  相似文献   
17.
We have studied lamp configuration design for rapid thermal processing (RTP) systems. We considered a configuration consisting of four concentric circular lamp zones, three of them above the wafer and one circumventing the wafer. We propose a method to determine the geometric parameters, the width, height and radius, of the lamp zones so that the configuration designed has the capacity to achieve a uniform temperature on the wafer. The method is based on a necessary and sufficient condition for uniform temperature tracking and analytic expressions of the view factors. A design example is given in which a least square open-loop control law yields good temperature uniformity  相似文献   
18.
A technique for SiO2 formation by liquid-phase deposition (LPD) at nearly room temperature for low-temperature processed (LTP) polysilicon thin-film transistor (poly-Si TFT) was developed. LPD SiO2 film with a lower P-etch rate shows a dense structure. LPD SiO2 also exhibits good electrical characteristics. LTP poly-Si thin-film transistors (TFTs) with LPD SiO 2 as the gate insulator have been fabricated and investigated. Their characteristics indicate performance adequate for their use as pixel transistors in liquid crystal displays (LCDs)  相似文献   
19.
精彩展品     
环保铁皮船 这艘铁皮船的动力由一支短短的普通蜡烛提供,不但前进、转弯等自如,而且支持时间可长达数小时,令不少买家非常感兴趣。专做德国生意的熊猫贸易老板陈祥龙认为,它既造价低廉又符合环保概念,在国外应该很有市场。凭他经验估计,以8元批发价拿到的产品,售价大约可以卖到12元,利润可观。  相似文献   
20.
In this paper, a gap-statistic-algorithm (GSA)-based data-mining technique is applied to enhance the data debugging in power system operations. In the proposed approach, the GSA technique is embedded into a neural network frame in anticipation of improving the detection capability of bad data. Thanks to the clustering capability exhibited by GSA in which the number of clusters can be optimally determined, the proposed approach becomes highly effective to localize the group of abnormal data. This proposed approach has been tested through the data collected from different scenarios made on an IEEE 30-bus system and 118-bus systems. Test results reveal the feasibility of the method for the data diagnosis applications.  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