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   179267篇
  免费   15657篇
  国内免费   8428篇
电工技术   11379篇
技术理论   13篇
综合类   11649篇
化学工业   29319篇
金属工艺   9913篇
机械仪表   11253篇
建筑科学   13706篇
矿业工程   5435篇
能源动力   5296篇
轻工业   12432篇
水利工程   3278篇
石油天然气   10723篇
武器工业   1404篇
无线电   21536篇
一般工业技术   21502篇
冶金工业   8736篇
原子能技术   1922篇
自动化技术   23856篇
  2024年   900篇
  2023年   3413篇
  2022年   6342篇
  2021年   8498篇
  2020年   6403篇
  2019年   5059篇
  2018年   5723篇
  2017年   6393篇
  2016年   5706篇
  2015年   7585篇
  2014年   9400篇
  2013年   11252篇
  2012年   12246篇
  2011年   12873篇
  2010年   10990篇
  2009年   10374篇
  2008年   9903篇
  2007年   9125篇
  2006年   9299篇
  2005年   7962篇
  2004年   5311篇
  2003年   4470篇
  2002年   4003篇
  2001年   3603篇
  2000年   3537篇
  1999年   4148篇
  1998年   3453篇
  1997年   2933篇
  1996年   2742篇
  1995年   2213篇
  1994年   1798篇
  1993年   1297篇
  1992年   1044篇
  1991年   785篇
  1990年   567篇
  1989年   466篇
  1988年   367篇
  1987年   252篇
  1986年   209篇
  1985年   129篇
  1984年   116篇
  1983年   86篇
  1982年   86篇
  1981年   68篇
  1980年   62篇
  1979年   29篇
  1978年   25篇
  1977年   24篇
  1976年   26篇
  1975年   16篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
随着我国有线电视技术的迅速发展,做好有线电视维修技术维护工作显得十分必要,对进一步提高有线广播电视安全优质播出越来越重要,选取有线电视维修技术中出现若干关键性问题并做出相关分析说明。  相似文献   
992.
目前教育部要求高校报送的学生就业报表众多,高校办学层次众多,需要进行一些就业数据的统计,分析,运用传统的VF9.0数据统计操作非常不方便,而SQL Server数据库比较适合用于高校学生就业数据统计。因此,SQL Server数据库在高校学生就业数据统计中的运用就显得尤为重要。本文就SQL Server数据库在高校学生就业数据统计中的运用进行了深入的探讨,具有一定的参考价值。  相似文献   
993.
提出一种基于MCS-51系列单片机控制液晶屏的设计方案,介绍了单片机对LM32019T单色显示屏控制的硬件接口电路以及模块化的程序编写方法,重点说明了SED1335液晶控制器的特点、使用方法及其与单片机的接口电路.  相似文献   
994.
安全与功能是一对矛盾的关系,来自网络的安全威胁是实际存在的,网络安全是首先要解决的问题。本文从安全策略的角度探讨企业网络设计的方法,以期调和安全与开放的关系,从而实现“尽可能安全”的企业网络。  相似文献   
995.
本文就远程教学中出现的流媒体技术做了简要说明,并对Windows Media软件中包含的3个组件进行了重点说明。对利用该组件进行课件采集、制作,Media服务器配置,Media Player功能等做了详细介绍,同时也描述了Windows Media的发展前景。  相似文献   
996.
云存储是一种新兴的网络存储服务,本文介绍云存储的概念,分析云存储的结构模型,总结云存储的优势,并探讨了搭建云存储系统的可行性。  相似文献   
997.
Many methods based on the rough set to deal with incomplete information systems have been proposed in recent years. However, they are only suitable for the incomplete systems with regular attributes whose domains are not preference-ordered. This paper thus attempts to present research focusing on a complex incomplete information system—the incomplete ordered information system. In such incomplete information systems, all attributes are considered as criterions. A criterion indicates an attribute with preference-ordered domain. To conduct classification analysis in the incomplete ordered information system, the concept of similarity dominance relation is first proposed. Two types of knowledge reductions are then formed for preserving two different notions of similarity dominance relations. With introduction of the approximate distribution reduct into the incomplete ordered decision system, the judgment theorems and discernibility matrixes associated with four novel approximate distribution reducts are obtained. A numerical example is employed to substantiate the conceptual arguments.  相似文献   
998.
The shapes of if-part fuzzy sets affect the approximating capability of fuzzy systems. In this paper, the fuzzy systems with the kernel-shaped if-part fuzzy sets are built directly from the training data. It is proved that these fuzzy systems are universal approximators and their uniform approximation rates can be estimated in the single-input-single-output (SISO) case. On the basis of these rates, the relationships between the approximating capability and the shapes of if-part fuzzy sets are developed for the fuzzy systems. Furthermore, the sinc functions that serve as input membership functions are proved to have the almost best approximation property in a particular class of membership functions. The theoretical results are confirmed from the simulation data. In addition, the estimations of the uniform approximation rates are extended to the multi-input-single-output (MISO) case.  相似文献   
999.
With the development of intelligent optical networks and the general multi-protocol label switching (GMPLS) technique, the seamless convergence between IP network and optical network is no longer be a dream but a practical reality. Similar to the Internet, current optical networks have been divided into multiple domains each of which has its own network provider and management policy. Therefore, the development of multi-domain optical networks will be the trend of new-generation intelligent optical networks, and GMPLS-based survivability for multi-domain optical networks will become a hot topic of research in the future. This paper provides a comprehensive review of the existing survivable schemes in multi-domain optical networks and analyzes the shortcomings of current research. Based on previous studies, we present possible challenges and propose new ideas to design efficient survivable schemes to guide the future work of researchers in multi-domain optical networks.  相似文献   
1000.
In the Galapagos Islands of Ecuador, one of the greatest threats to the terrestrial ecosystem is the increasing number and areal extent of invasive species. Increased human presence on the islands has hastened the introduction of plant and animal species that threaten the native and endemic flora and fauna. Considerable research on invasive species in the Galapagos Islands has been conducted by the Charles Darwin Foundation. We complement that work through a spatially- and spectrally-explicit satellite assessment of an important invasive plant species (Psidium guajava — guava) on Isabela Island that integrates diverse remote sensing systems, data types, spatial and spectral resolutions, and analytical and image processing approaches. QuickBird and Hyperion satellite data are processed to characterize the areal extent and spatial structure of guava through the following approaches: (1) QuickBird data are classified through a traditional pixel-based approach (i.e., an unsupervised classification approach using the ISODATA algorithm), as well as an Object-Based Image Analysis (OBIA) approach; (2) multiple approaches for spectral “unmixing” of the Hyperion hyper-spectral data are assessed to construct spectral end-members from QuickBird data using linear and non-linear mixture modeling approaches; and (3) landscape pattern metrics are calculated and compared for the pixel-based, object-based, and spectral unmixing approaches. The spectral–spatial characteristics of guava are interpreted relative to management strategies for the control of guava and the restoration of natural ecosystems in the Galapagos National Park.  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