全文获取类型
收费全文 | 41264篇 |
免费 | 5164篇 |
国内免费 | 3310篇 |
专业分类
电工技术 | 3773篇 |
技术理论 | 1篇 |
综合类 | 4550篇 |
化学工业 | 3952篇 |
金属工艺 | 1619篇 |
机械仪表 | 3557篇 |
建筑科学 | 2272篇 |
矿业工程 | 1525篇 |
能源动力 | 1071篇 |
轻工业 | 677篇 |
水利工程 | 1059篇 |
石油天然气 | 1533篇 |
武器工业 | 575篇 |
无线电 | 6060篇 |
一般工业技术 | 3197篇 |
冶金工业 | 976篇 |
原子能技术 | 380篇 |
自动化技术 | 12961篇 |
出版年
2024年 | 242篇 |
2023年 | 555篇 |
2022年 | 978篇 |
2021年 | 1183篇 |
2020年 | 1319篇 |
2019年 | 1122篇 |
2018年 | 1061篇 |
2017年 | 1433篇 |
2016年 | 1529篇 |
2015年 | 1759篇 |
2014年 | 2546篇 |
2013年 | 2360篇 |
2012年 | 2973篇 |
2011年 | 3279篇 |
2010年 | 2440篇 |
2009年 | 2406篇 |
2008年 | 2482篇 |
2007年 | 2923篇 |
2006年 | 2585篇 |
2005年 | 2298篇 |
2004年 | 1925篇 |
2003年 | 1965篇 |
2002年 | 1721篇 |
2001年 | 1513篇 |
2000年 | 1147篇 |
1999年 | 876篇 |
1998年 | 625篇 |
1997年 | 536篇 |
1996年 | 439篇 |
1995年 | 335篇 |
1994年 | 275篇 |
1993年 | 209篇 |
1992年 | 157篇 |
1991年 | 112篇 |
1990年 | 78篇 |
1989年 | 76篇 |
1988年 | 57篇 |
1987年 | 36篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 26篇 |
1983年 | 35篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1959年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
主要讨论印刷电路板(PCB)移动探针测试中软件及检测中遇到特殊情况的处理,并对造成通短路现象的原因进行了分析,以达到保证PCB产品质量的目的。 相似文献
63.
Further evidence was delivered that certain impurities, which could be contained in MgO samples, might be responsible for observed variability in MgO basicity and catalytic performance in oxidative coupling of methane. The surface basicity/base strength distribution of a series of MgO samples containing or not containing Ca and Na impurities was determined by a temperature-programmed desorption of CO2. It was revealed that samples containing Ca and Na impurities have much more medium, strong and very strong basic sites. The surface basicity of MgO samples containing added alkali or alkaline earth compounds or water was characterized by a test reaction of transformation of 2-butanol. It was confirmed that the introduction of these compounds to a pure MgO enhanced both its basicity and activity in oxidative coupling of methane. 相似文献
64.
尼龙6/马来酸酐-苯乙烯多单体接枝聚丙烯反应共混物 总被引:8,自引:0,他引:8
用双螺杆挤出机制备了聚丙烯(PP)与尼龙6(PA6)的共混物.先用多组分熔融接枝的方法将马来酸杆(MAH)和苯乙烯(St)共同接枝于聚丙烯(PP)上,制得多单体接枝聚丙烯PP-g-(MAH-St),该接枝物具有较高的MAH接枝率。利用MFR、SEM、TEM和力学性能测试等分析方法,研究了多组分熔融接枝聚丙烯PP-g-(MAH-St)对PA6/PP共混物的形态结构和力学性能等的影响。结果表明,PP-g-(MAH-St)中的酸酐基团与PA6末端的氨基发生化学反应,原位形成的PP-PA6共聚物能有效地改善PA6与PP的相容性,可以使PP均匀地分散在PA6基体中,相区尺寸明显减小,可至0.1μm,并使共混物的力学性能得到均衡的提高,冲击韧性的提高尤其显著,达到了橡胶改性所难以达到的效果。 相似文献
65.
66.
Jaroslav Mackerle 《International Journal of Pressure Vessels and Piping》1996,69(3):279-339
The paper gives a bibliographical review of the finite element methods (FEMs) applied for the analysis of pressure vessel structures/components and piping from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore the aim of this review is to give the reader an encyclopaedic view of the differnt possibilities that exist today for the finite element analysis in the fields of pressure vessels and piping. The bibliography at the end of the paper contains approximately 1900 references to papers, conference proceedings and theses/dissertations on the subject that were published in 1976–1996. These are classified in the following categories: linear and non-linear, static and dynamic, stress and deflection analysis; stability problems; thermal problems; fracture mechanics problems; contact problems; fluid-structure interaction problems; manufacturing of pipes and tubes; welded pipes and pressure vessel components; development of special finite elements for pressure vessels and pipes; finite element software; and other topics. Also finite element software, general purpose and special purpose codes, used for the analysis of pressure vessels and pipes are briefly discussed and presented. 相似文献
67.
轻便型γ能谱测井仪几个关键技术问题的探讨 总被引:1,自引:0,他引:1
为研制性能好,功能强,微机化学程度高的轻便型γ能谱测井仪,针对非油气测井工作的井口径小(〈φ60mm)井身浅(〈1000m)等特点,探讨了γ能谱测井仪的轻便化,测量精度,信号传输技术,稳谱技术及微机化等关键技术问题。 相似文献
68.
69.
Paul W. Oman 《Software Quality Journal》1993,2(1):13-27
Software quality assurance (SQA) audits are becoming a standard practice in corporations seeking to enter contractual relations with other organizations, or just evaluating their own state of readiness. This paper describes one approach to conducting SQA audits. Excerpts from reports of actual audits conducted on several organizations engaged in software development are used to show how an audit is conducted and what can be achieved through the auditing process. The paper is not meant to be a definitive answer or guide to doing SQA audits. Rather, it serves as an annotated case study of how SQA audits can be conducted with an emphasis on data gathering and reporting.Dr Paul W. Oman is an associate professor of computer science at the University of Idaho, and an independent software consultant who specializes in software analysis. He is the director of the Software Engineering Test Lab within the UI College of Engineering, where he conducts research in software development methods, CASE tools, and software maintainability issues. Oman has published over 50 articles and reports on software tools, software development, and computer science education. He has a PhD in computer science and is a member of the IEEE, IEEE Computer Society, and ACM. 相似文献
70.
本文给出从指称语义自动生成解释器后端的一种技术.解释器被表示成PASCAL_like形式. 相似文献