全文获取类型
收费全文 | 605085篇 |
免费 | 94344篇 |
国内免费 | 58305篇 |
专业分类
电工技术 | 50275篇 |
技术理论 | 65篇 |
综合类 | 45464篇 |
化学工业 | 93607篇 |
金属工艺 | 44920篇 |
机械仪表 | 33613篇 |
建筑科学 | 45730篇 |
矿业工程 | 26003篇 |
能源动力 | 20319篇 |
轻工业 | 45439篇 |
水利工程 | 14329篇 |
石油天然气 | 37567篇 |
武器工业 | 6924篇 |
无线电 | 76380篇 |
一般工业技术 | 78807篇 |
冶金工业 | 29596篇 |
原子能技术 | 5572篇 |
自动化技术 | 103124篇 |
出版年
2024年 | 4070篇 |
2023年 | 10334篇 |
2022年 | 15871篇 |
2021年 | 21015篇 |
2020年 | 20316篇 |
2019年 | 26974篇 |
2018年 | 29900篇 |
2017年 | 32281篇 |
2016年 | 30810篇 |
2015年 | 34088篇 |
2014年 | 37498篇 |
2013年 | 41201篇 |
2012年 | 41788篇 |
2011年 | 41387篇 |
2010年 | 36261篇 |
2009年 | 32292篇 |
2008年 | 30222篇 |
2007年 | 28579篇 |
2006年 | 28781篇 |
2005年 | 25679篇 |
2004年 | 20811篇 |
2003年 | 17811篇 |
2002年 | 16233篇 |
2001年 | 14875篇 |
2000年 | 14928篇 |
1999年 | 16242篇 |
1998年 | 14019篇 |
1997年 | 11963篇 |
1996年 | 11276篇 |
1995年 | 9905篇 |
1994年 | 8181篇 |
1993年 | 6488篇 |
1992年 | 5607篇 |
1991年 | 4248篇 |
1990年 | 3366篇 |
1989年 | 2937篇 |
1988年 | 2347篇 |
1987年 | 1213篇 |
1986年 | 931篇 |
1985年 | 669篇 |
1984年 | 454篇 |
1983年 | 357篇 |
1982年 | 394篇 |
1981年 | 304篇 |
1980年 | 258篇 |
1978年 | 155篇 |
1976年 | 323篇 |
1975年 | 233篇 |
1972年 | 252篇 |
1960年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
81.
涤纶复合丝(POY+DTY)的研发 总被引:1,自引:0,他引:1
DTY和POY网络复合丝是以聚酯直纺生产的两种不同规格的POY丝为原料,通过对加弹机进行适当改造,利用不同的加工路线,使一股POY丝经过加捻后形成DTY,再与另一股POY丝网络合股形成包芯复合丝.该复合丝利用POY丝和DTY丝的收缩差异和染色差异等不同风格特性,使得布面形成一种具有雪花状的色丁效果.该复合丝属于差别化纤维,是国家鼓励发展的项目,它具有优良的吸湿排汗性能和弹性保暖性能,是保暖内衣的首选面料,市场前景广阔. 相似文献
82.
Feng Wang Chong-Wah Ngo Ting-Chuen Pong 《Multimedia, IEEE Transactions on》2008,10(5):926-935
83.
84.
This paper describesMicroScope, a framework for developing analysis tools for Lisp programs. MicroScope uses a knowledge-intensive approach for program representation and analysis. The analysis tools share a common object oriented program database, and a common Prolog inference engine. The use of Prolog and a declarative representation for programs permits sharing of information, and provides high bandwidth communication between diverse analysis tools. It also supports program specification and debugging activities in the same framework. Extensions to Prolog to support analysis are described, and two tools, theCritic and theExpector, are presented.This work supported in part by Hewlett-Packard Company, the National Science foundation Under Grant Number MCS81-21750 and the Defense Advanced Research Projects Agency under contract number DAAK11-84-K-0017. 相似文献
85.
86.
城市交通对城市的社会经济活动和生态资源环境具有双向作用,是城市功能中最活跃的因素.目前城市交通问题突出表现在交通阻塞和汽车尾气污染两个方面,已成为困扰着大中城市发展的主要问题.交通堵塞不仅给人们的生活和工作带来不便,而且增加了城市经济运行的时间成本,影响到城市功能的发挥和城市的健康发展,同时又进一步加剧了能源的消耗.可见城市交通问题是关系到城市可持续发展的关键问题之一. 相似文献
87.
C. A. Pineda P. Wenzl J. Mayer J. Mesjasz-Przybylowicz W. J. Przybylowicz V. M. Prozesky 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):362-367
A Brachiaria breeding project is being conducted at CIAT, Colombia to combine acid soil adaptation of B. decumbens with other favourable traits of Brachiaria species that are less adapted to acid soils. Micro-PIXE was applied to investigate nutrient uptake and distribution in root tips of different species grown in hydroponic culture under control and simulated acid soil stress conditions. Different sample measurement approaches were evaluated, including: (1) linear scans with single point measurements along the root axis; (2) mapping of whole root tips; and (3) mapping of root cross sections. Different tissue types could be distinguished on the base of differences in nutrient concentrations and/or Al stress. Al, if supplied under nutrient stress conditions, increased P accumulation in the central vascular tissue of the meristematic and elongation zone of B. decumbens and B. brizantha. Furthermore, a negative correlation was found between Al and Cl accumulation in the root cap of B. decumbens. 相似文献
88.
Sverak J.G. Wang W. Gervais Y. Do X.-D. Mukhedkar D. 《Power Delivery, IEEE Transactions on》1992,7(3):1196-1206
An improved multivariable, probabilistic method for the safety analysis of power grounding systems is presented. The application of this method is demonstrated in four examples. The first three examples illustrate the practical evaluation of one new and two existing substation grounding grids when the substation is connected to an overhead distribution system. The fourth example ascertains the relative impact of a difference between the S curve of IEC Publication 479 and Dalziel's equation for the allowable body current used in ANSI/IEEE Std 80-1986 on the validity of an exposure model based on the requirements of Std 80. In this example, the statistical data on ground faults have been taken from actual system records. Further possible refinements of the exposure model are discussed 相似文献
89.
In this paper the results are presented of a test program on the energy absorption of composite cylinders loaded in compression. The influence of the laminate lay-up and of the trigger configuration were determined. Two different failure modes for the different laminates and triggers were observed: a splaying mode and a fragmentation mode. The splaying mode is more efficient in absorbing energy. The failure mode did not change during the crushing process. 相似文献
90.
Exchange and oxidation of C16O were investigated at 450°C on 18O-predosed Rh and Pt catalysts supported on A12O3, CeO2 and CeO2-Al2O3. In all cases, a rapid exchange of C16O with the surface can be observed. CO oxidation leads to C16O2, C16O18O and C18O2. Significant formation of C16O2 is due to the relatively high 16O coverage in reaction resulting from the C16O exchange and from an exchange between O surface species and 16O internal atoms. Hydrogen is also formed via a water-gas shift reaction (CO + surface OH) in higher proportion on CeO2-containing catalysts than on A12O3. Chlorine inhibits all the reactions (exchange, oxidation and WGS) and particularly the internal exchange. 相似文献