全文获取类型
收费全文 | 179267篇 |
免费 | 15657篇 |
国内免费 | 8428篇 |
专业分类
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 |
出版年
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.
杨学林 《计算机光盘软件与应用》2010,(9):77-77
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.
杨杰 《计算机光盘软件与应用》2010,(16)
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.
杨浩军 《计算机光盘软件与应用》2010,(6):105-105
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.
Dominance-based rough set approach and knowledge reductions in incomplete ordered information system 总被引:6,自引:0,他引:6
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.
Lei Guo Xingwei Wang Qingyang Song Weigang Hou Fei Yang 《Information Sciences》2008,178(18):3635-3644
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.
Stephen J. Walsh Amy L. McCleary Carlos F. Mena Yang Shao Julie P. Tuttle Augusto Gonzlez Rachel Atkinson 《Remote sensing of environment》2008,112(5):291-1941
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