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   41775篇
  免费   4160篇
  国内免费   1861篇
电工技术   2543篇
技术理论   5篇
综合类   3133篇
化学工业   6969篇
金属工艺   2376篇
机械仪表   2758篇
建筑科学   3070篇
矿业工程   1182篇
能源动力   1216篇
轻工业   4315篇
水利工程   804篇
石油天然气   2420篇
武器工业   310篇
无线电   4396篇
一般工业技术   4691篇
冶金工业   1757篇
原子能技术   425篇
自动化技术   5426篇
  2024年   376篇
  2023年   836篇
  2022年   1555篇
  2021年   2072篇
  2020年   1670篇
  2019年   1225篇
  2018年   1382篇
  2017年   1563篇
  2016年   1335篇
  2015年   1991篇
  2014年   2380篇
  2013年   2791篇
  2012年   2994篇
  2011年   3236篇
  2010年   2760篇
  2009年   2622篇
  2008年   2586篇
  2007年   2367篇
  2006年   2205篇
  2005年   1692篇
  2004年   1069篇
  2003年   944篇
  2002年   980篇
  2001年   821篇
  2000年   702篇
  1999年   761篇
  1998年   552篇
  1997年   469篇
  1996年   398篇
  1995年   352篇
  1994年   277篇
  1993年   191篇
  1992年   160篇
  1991年   100篇
  1990年   96篇
  1989年   68篇
  1988年   46篇
  1987年   42篇
  1986年   31篇
  1985年   23篇
  1984年   11篇
  1983年   12篇
  1982年   6篇
  1981年   13篇
  1980年   16篇
  1979年   4篇
  1978年   2篇
  1977年   3篇
  1959年   2篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
近年来,防火墙在网络中得到了广泛的应用.它能够比较有效地防范病毒与黑客的攻击,保护网络的安全.但是也带来了一些不利影响,使一些需要进行网络通信的应用软件系统不能正常工作.介绍一个解决方案,并且重点介绍通过HTTP Tunneling技术使用基于文本的HTTP协议传送二进制数据的方法.  相似文献   
42.
该文通过对车辆安全因数的分析、得出子危险集。在分析评价方法特征技术上应用了选用模糊推理模型(FIS)的评价方法对车辆的危险度进行评价与仿真,其结果是可信的。实现了对车辆安全进行量态和动态的评价体系。  相似文献   
43.
本文从各类数据在计算机中存在的状态以及在存储过程中的安全问题,对数据的安全性和保护性进行了论证。  相似文献   
44.
The delay‐dependent stability problem of linear continuous/discrete systems with time‐varying delay is investigated based on a piecewise analysis method (PAM). In the method, the variation interval of the time delay is firstly divided into several subintervals. By checking the variation of the Lyapunov functional in every subinterval, some new delay‐dependent stability criteria are derived. Several numerical examples show that our method can lead to much less conservative results than those in the existing references. Moreover, when the number of the divided subintervals increases, the corresponding criteria can provide an improvement on the results. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
45.
Organic redox-active materials are promising electrode candidates for lithium-ion batteries by virtue of their designable structure and cost-effectiveness. However, their poor electrical conductivity and high solubility in organic electrolytes limit the device's performance and practical applications. Herein, the π-conjugated nitrogen-containing heteroaromatic molecule hexaazatriphenylene (HATN) is strategically embedded with redox-active centers in the skeleton of a Cu-based 2D conductive metal–organic framework (2D c-MOF) to optimize the lithium (Li) storage performance of organic electrodes, which delivers improved specific capacity (763 mAh g−1 at 300 mA g−1), long-term cycling stability (≈90% capacity retention after 600 cycles at 300 mA g−1), and excellent rate performance. The correlation of experimental and computational results confirms that this high Li storage performance derives from the maximum number of active sites (CN sites in the HATN unit and CO sites in the CuO4 unit), favorable electrical conductivity, and efficient mass transfer channels. This strategy of integrating multiple redox-active moieties into the 2D c-MOF opens up a new avenue for the design of high-performance electrode materials.  相似文献   
46.
Despite the outstanding power conversion efficiency (PCE) of perovskite solar cells (PSCs) achieved over the years, unsatisfactory stability and lead toxicity remain obstacles that limit their competitiveness and large-scale practical deployment. In this study, in situ polymerizing internal encapsulation (IPIE) is developed as a holistic approach to overcome these challenges. The uniform polymer internal package layer constructed by thermally triggered cross-linkable monomers not only solidifies the ionic perovskite crystalline by strong electron-withdrawing/donating chemical sites, but also acts as a water penetration and ion migration barrier to prolong shelf life under harsh environments. The optimized MAPbI3 and FAPbI3 devices with IPIE treatment yield impressive efficiencies of 22.29% and 24.12%, respectively, accompanied by remarkably enhanced environmental and mechanical stabilities. In addition, toxic water-soluble lead leakage is minimized by the synergetic effect of the physical encapsulation wall and chemical chelation conferred by the IPIE. Hence, this strategy provides a feasible route for preparing efficient, stable, and eco-friendly PSCs.  相似文献   
47.
Smart grid has drawn a lot of attention and investment in recent years, which not only helps the modern generation and distribution of traditional power but also highly widens the application of renewable energy sources. However, the main challenges in the application of smart grid are 1. the privacy preservation of users' information and 2. the trustful transmission channel among peers. In order to solve these problems, VPN and blockchain can be considered since they have some features perfectly suitable for these situations. In this paper, we propose a smart grid system based on WireGuard and Hyperledger Fabric to solve the problems mentioned above. And we also implement the whole system and give a view by web application. What's more, all the functionalities are displayed and tested, including building a smart device simulator, deploying data visualization and making some performance evaluations about transactions and WireGuard communication. Experiment results show that the introduction of WireGuard into network infrastructure does not cause too much loss of bandwidth and delay, but it ensures a certain degree of communication security. And Fabric provides the consistency and traceability of transactions in smart grid system.  相似文献   
48.
Following logic in the silicon semiconductor industry, the existence of native oxide and suitable fabrication technology is essential for 2D semiconductors in planar integronics, which are surface-sensitive to typical coating technologies. To date, very few types of integronics are found to possess this feature. Herein, the 2D Bi2O2Te developed recently is reported to possess large-area synthesis and controllable thermal oxidation behavior toward single-crystal native oxides. This shows that surface-adsorbed oxygen atoms are inclined to penetrate across [Bi2O2]n2n+ layers and bond with the underlying [Te]n2n− at elevated temperatures, transforming directly into [TeO4]n2n− with the basic architecture remaining stable. The oxide can be adjusted to form in an accurate layer-by-layer manner with a low-stress sharp interface. The native oxide Bi2TeO6 layer (bandgap of ≈2.9 eV) exhibits visible-light transparency and is compatible with wet-chemical selective etching technology. These advances demonstrate the potential of Bi2O2Te in planar-integrated functional nanoelectronics such as tunnel junction devices, field-effect transistors, and memristors.  相似文献   
49.
Qian  Kui  Tian  Lei 《Applied Intelligence》2022,52(10):11160-11171
Applied Intelligence - A robot control system is a multivariable, nonlinear automatic control system, as well as a dynamic coupling system. To address the difficult problem of data prediction under...  相似文献   
50.
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