全文获取类型
收费全文 | 20999篇 |
免费 | 1534篇 |
国内免费 | 863篇 |
专业分类
电工技术 | 1138篇 |
技术理论 | 4篇 |
综合类 | 1118篇 |
化学工业 | 3788篇 |
金属工艺 | 987篇 |
机械仪表 | 1239篇 |
建筑科学 | 1436篇 |
矿业工程 | 569篇 |
能源动力 | 602篇 |
轻工业 | 1161篇 |
水利工程 | 318篇 |
石油天然气 | 1196篇 |
武器工业 | 139篇 |
无线电 | 2734篇 |
一般工业技术 | 2756篇 |
冶金工业 | 1072篇 |
原子能技术 | 195篇 |
自动化技术 | 2944篇 |
出版年
2024年 | 77篇 |
2023年 | 343篇 |
2022年 | 589篇 |
2021年 | 838篇 |
2020年 | 602篇 |
2019年 | 564篇 |
2018年 | 621篇 |
2017年 | 646篇 |
2016年 | 594篇 |
2015年 | 773篇 |
2014年 | 961篇 |
2013年 | 1281篇 |
2012年 | 1223篇 |
2011年 | 1336篇 |
2010年 | 1084篇 |
2009年 | 1093篇 |
2008年 | 1073篇 |
2007年 | 1018篇 |
2006年 | 1067篇 |
2005年 | 953篇 |
2004年 | 636篇 |
2003年 | 617篇 |
2002年 | 538篇 |
2001年 | 464篇 |
2000年 | 549篇 |
1999年 | 599篇 |
1998年 | 545篇 |
1997年 | 469篇 |
1996年 | 454篇 |
1995年 | 331篇 |
1994年 | 312篇 |
1993年 | 215篇 |
1992年 | 175篇 |
1991年 | 141篇 |
1990年 | 127篇 |
1989年 | 96篇 |
1988年 | 77篇 |
1987年 | 52篇 |
1986年 | 44篇 |
1985年 | 38篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 30篇 |
1981年 | 22篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
新型超微晶软磁合金FePCCuMoSi微观结构缺陷的正电子湮没研究 总被引:1,自引:0,他引:1
用正电子湮没方法研究了新型超微晶软磁合金的微观结构缺陷,样品选用的是在不同温度下退火的Fe81P12C3Cu1Mo0.5Si2.5合金,结果表明,合金的微观结构构陷大小,密度随退火温度有规律地变化,这种现象可能与非晶的晶化过程有关。 相似文献
22.
重馏分油加氢脱氮反应动力学模型的研究 总被引:10,自引:1,他引:9
简要地介绍了一些典型的模型氮化物的HDN反应规律。根据胜利VGO在3722B催化剂上的大量HDN实验数据,提出了如下的HDN基本反应动力学方程:dCNdt=-k1+K*CNCNPH2为了扩大上式的应用范围,详细分析了各种因素(如原料油种类和馏程及H2S等)对HDN的影响,并开发了相应的经验关联式,从而得到了一个较完整的馏分油HDN反应动力学模型。验证实验表明,该模型是成功的。 相似文献
23.
本文对CIMS装配线和拆卸线的可靠性问题进行研究。文中分析了它们的运行状况,求出了两种生产线的稳态可用度,并用一个例子加以说明。 相似文献
24.
本文利用等效工作站理论和工件流平衡原理,推导出非串行离散事件生产线可以等价于串联系统,并归结为装配和拆卸两条定理,解决了系统的建模、分析与设计问题。 相似文献
25.
In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study. 相似文献
26.
目前采气井站的安全教育培训工作取得了一定成绩,但也存在不少问题。针对这些问题,提出了3点对策建议:制定长期系统的安全培训计划;建立教育培训信息反馈机制;培训方法不断改进与创新。 相似文献
27.
Years have lapsed since the inauguration of the first Wireless Application Protocol (WAP) application. One of the main reasons for the lukewarm response so far may be attributed to the lack of a “Killer” application. Many companies and developers have attempted to replicate email services (an Internet Killer appplication) within the WAP realm, but till now, no significant success has been reported. This paper will first discuss on the key functions which are lacking in the present WAP-email service, and which are arguably necessary if a much larger user base is to be attracted to these services. A new system will be proposed which can enable the user to send files residing in a remote personal computer (PC) as attachments to his emails using WAP-enabled mobile devices. The implementation of the system will be presented in details. Issue relating to the connection to various types of email servers and the security of the system will also be addressed in the paper. 相似文献
28.
In addition to satisfying several competing objectives, many real-world applications are also characterized by a certain degree of noise, manifesting itself in the form of signal distortion or uncertain information. In this paper, extensive studies are carried out to examine the impact of noisy environments in evolutionary multiobjective optimization. Three noise-handling features are then proposed based upon the analysis of empirical results, including an experiential learning directed perturbation operator that adapts the magnitude and direction of variation according to past experiences for fast convergence, a gene adaptation selection strategy that helps the evolutionary search in escaping from local optima or premature convergence, and a possibilistic archiving model based on the concept of possibility and necessity measures to deal with problem of uncertainties. In addition, the performances of various multiobjective evolutionary algorithms in noisy environments, as well as the robustness and effectiveness of the proposed features are examined based upon five benchmark problems characterized by different difficulties in local optimality, nonuniformity, discontinuity, and nonconvexity 相似文献
29.
本文以淄博广电总台7 1讯道数字分量转播车为例,浅谈该车的视频、音频系统以及设备配置情况. 相似文献
30.