全文获取类型
收费全文 | 8535篇 |
免费 | 724篇 |
国内免费 | 419篇 |
专业分类
电工技术 | 367篇 |
综合类 | 632篇 |
化学工业 | 883篇 |
金属工艺 | 613篇 |
机械仪表 | 369篇 |
建筑科学 | 1447篇 |
矿业工程 | 239篇 |
能源动力 | 276篇 |
轻工业 | 434篇 |
水利工程 | 228篇 |
石油天然气 | 473篇 |
武器工业 | 504篇 |
无线电 | 376篇 |
一般工业技术 | 1117篇 |
冶金工业 | 1163篇 |
原子能技术 | 117篇 |
自动化技术 | 440篇 |
出版年
2024年 | 25篇 |
2023年 | 129篇 |
2022年 | 162篇 |
2021年 | 214篇 |
2020年 | 215篇 |
2019年 | 236篇 |
2018年 | 218篇 |
2017年 | 279篇 |
2016年 | 304篇 |
2015年 | 270篇 |
2014年 | 424篇 |
2013年 | 602篇 |
2012年 | 434篇 |
2011年 | 640篇 |
2010年 | 492篇 |
2009年 | 528篇 |
2008年 | 484篇 |
2007年 | 595篇 |
2006年 | 511篇 |
2005年 | 391篇 |
2004年 | 349篇 |
2003年 | 348篇 |
2002年 | 285篇 |
2001年 | 192篇 |
2000年 | 159篇 |
1999年 | 148篇 |
1998年 | 107篇 |
1997年 | 122篇 |
1996年 | 92篇 |
1995年 | 100篇 |
1994年 | 84篇 |
1993年 | 65篇 |
1992年 | 58篇 |
1991年 | 45篇 |
1990年 | 34篇 |
1989年 | 36篇 |
1988年 | 24篇 |
1987年 | 25篇 |
1986年 | 10篇 |
1985年 | 27篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1979年 | 8篇 |
1965年 | 14篇 |
1961年 | 8篇 |
1957年 | 11篇 |
1955年 | 16篇 |
1954年 | 11篇 |
排序方式: 共有9678条查询结果,搜索用时 62 毫秒
11.
纤维在沥青混合料中的应用研究 总被引:1,自引:0,他引:1
选用工程中常用的几种纤维,结合工程应用要求,试验分析了纤维的吸湿性、耐热性,并通过网篮析漏试验、动态剪切试验和沉锥试验,讨论了纤维对沥青的稳定和吸附作用,以及纤维对沥青混合料“加筋”效果和作用机理。研究表明有的纤维“吸附、稳定”性能好,而有的纤维“加筋、桥接”效果好,在应用纤维时,应根据纤维的主要特点以及沥青混合料的使用要求来选用。 相似文献
12.
The effects of the cuticle and epicuticular waxes of grapefruit, strawberry and apple on the photodegradation and penetration of chlorpyrifos-methyl were studied. Photodegradation experiments were conducted by exposing the insecticide to the light of a xenon lamp in the presence of a film of wax extracted from the fruit surface. The half-life of chlorpyrifos-methyl irradiated in absence of waxes was 9.6 min. The half-lives of pesticide irradiated in the presence of wax extracts of apple, grapefruit and strawberry were 83, 34 and 26 min, respectively. In penetration studies, fruit with and without wax layers were treated with an aqueous suspension of pesticide. The penetration of the pesticide from the cuticle to the pulp was measured after 24 h. Samples without wax contained a higher total amount of insecticide than those with wax. No pesticide was detected in samples of apple and grapefruit pulp. Residues were detected in all fractions of strawberry. The waxes and cuticle appear to have some effect on the photodegradation and penetration of chlorpyrifos-methyl in fruit samples. 相似文献
13.
Field Static Load Test on Kao-Ping-Hsi Cable-Stayed Bridge 总被引:1,自引:0,他引:1
Field load testing is an effective method for understanding the behavior and fundamental characteristics of a cable-stayed bridge. This paper presents the results of field static load tests on the Kao-Ping-Hsi cable-stayed bridge, the longest cable-stayed bridge in Taiwan, before it was open to traffic. A total of 40 loading cases, including the unit and distributed bending and torsion loading effects, were conducted to investigate the bridge behavior. The atmospheric temperature effect on the variations of the main girder deflections was also monitored. The results of static load testing include the main girder deflections, the flexural strains of the prestressed concrete girder, and the variations of the cable forces. A three-dimensional finite-element model was developed. The results show that the bridge under the planned load test conditions has linear superposition characteristics and the analytical model shows a very good agreement with the bridge responses. Further discussion of deflection and cable forces of the design specifications for a cable-stayed bridge is also presented. 相似文献
14.
15.
涡轮钻具在高陡构造的应用及展望 总被引:1,自引:1,他引:0
介绍了涡轮钻具在秋参1井的应用情况,详细叙述了涡轮钻具在山前高陡构造快速钻进及防斜打直方面的优点,与常规钻井相比,机械钻速明显提高,钻井周期明显缩短,钻井成本明显下降,经济效益显著。 相似文献
16.
17.
Ryba Nancy L.; Cooper Virginia G.; Zapf Patricia A. 《Canadian Metallurgical Quarterly》2003,34(5):499
What is the current standard of practice for evaluations of juvenile competence to stand trial (JCST)? The present study surveyed psychologists regarding the practices used when conducting JCST evaluations. Respondents rated the importance of 17 elements that might be included in a JCST evaluation report. Of these elements, 7 were considered essential by 70% or more of respondents, with 9 additional elements rated as either essential or recommended. A majority of respondents felt that the use of psychological and forensic instruments was important. A list of tests used is provided, and the implications for the development of standards and policy are discussed to provide practitioners with additional knowledge that will help to further the state of the discipline. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
Reinforced concrete slabs are among the most common structural elements. In spite of the large number of slabs designed and built, the effect of their details on their behavior under impact loads are not always appreciated or properly taken into account. This experimental study was aimed at understanding the dynamic behavior of structural concrete slabs under impact loading to improve the state of the art of protective design. This study investigated the effects of different types of slab reinforcements and the applied impact loads on the dynamic response and behavior of reinforced concrete slabs. 相似文献
19.
Recent advances in isotropic conductive adhesives for electronics packaging applications 总被引:4,自引:0,他引:4
Isotropic conductive adhesives (ICAs) have recently received a lot of focus and attention from the researchers in electronics industry as a potential substitute to lead-bearing solders. Numerous studies have shown that ICAs possess many advantages over conventional soldering such as environmental friendliness, finer pitch printing, lower temperature processing and more flexible and simpler processing. However, complete replacement of soldering by ICAs is yet not possible owing to several limitations of ICAs which are mainly related to reliability aspects like limited impact resistance, unstable contact resistance, low adhesion and conductivity etc. Continued efforts for last 15 years have resulted in development of ICAs with improved properties. This review article is aimed at providing a better understanding of ICAs, their principles, performance and significant research and development work addressing the technological utility of ICAs. 相似文献
20.
俄罗斯减速器涡轮钻具驱动PDC钻头在西西伯利亚油田的成功应用 总被引:9,自引:2,他引:7
涡轮钻具由前苏联研制出来以后,得到了迅速发展,目前已发展到减速器涡轮钻具阶段。现在,俄罗斯西西伯利亚地区普遍使用减速器涡轮钻具钻井,而减速器涡轮钻具驱动PDC钻头的使用还是空白。采用俄罗斯生产的几种不同型号的减速器涡轮钻具,在西西伯利亚进行了驱动PDC钻头钻井的阶段性试验。试验结果表明,在优选PDC钻头结构的情况下,用减速器涡轮钻具驱动PDC钻头,钻头进尺和机械钻速都较牙轮钻头有显著的提高,经济和社会效益显著。介绍了试验中使用的3种俄罗斯减速器涡轮钻具(TPM-195,TPⅢ-195和TPO3—195)的结构特点和主要技术参数。 相似文献