全文获取类型
收费全文 | 44564篇 |
免费 | 1854篇 |
国内免费 | 80篇 |
专业分类
电工技术 | 475篇 |
综合类 | 38篇 |
化学工业 | 9505篇 |
金属工艺 | 881篇 |
机械仪表 | 898篇 |
建筑科学 | 2314篇 |
矿业工程 | 133篇 |
能源动力 | 1302篇 |
轻工业 | 3654篇 |
水利工程 | 482篇 |
石油天然气 | 142篇 |
武器工业 | 6篇 |
无线电 | 3413篇 |
一般工业技术 | 7540篇 |
冶金工业 | 7475篇 |
原子能技术 | 339篇 |
自动化技术 | 7901篇 |
出版年
2023年 | 251篇 |
2022年 | 538篇 |
2021年 | 800篇 |
2020年 | 585篇 |
2019年 | 783篇 |
2018年 | 981篇 |
2017年 | 900篇 |
2016年 | 1088篇 |
2015年 | 982篇 |
2014年 | 1358篇 |
2013年 | 2907篇 |
2012年 | 2081篇 |
2011年 | 2595篇 |
2010年 | 2054篇 |
2009年 | 1922篇 |
2008年 | 2206篇 |
2007年 | 2118篇 |
2006年 | 1932篇 |
2005年 | 1715篇 |
2004年 | 1428篇 |
2003年 | 1350篇 |
2002年 | 1286篇 |
2001年 | 846篇 |
2000年 | 714篇 |
1999年 | 725篇 |
1998年 | 733篇 |
1997年 | 718篇 |
1996年 | 694篇 |
1995年 | 694篇 |
1994年 | 651篇 |
1993年 | 603篇 |
1992年 | 590篇 |
1991年 | 357篇 |
1990年 | 517篇 |
1989年 | 473篇 |
1988年 | 375篇 |
1987年 | 415篇 |
1986年 | 362篇 |
1985年 | 498篇 |
1984年 | 503篇 |
1983年 | 394篇 |
1982年 | 371篇 |
1981年 | 347篇 |
1980年 | 318篇 |
1979年 | 339篇 |
1978年 | 278篇 |
1977年 | 284篇 |
1976年 | 254篇 |
1975年 | 222篇 |
1974年 | 211篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
Jean Poerre 《钢铁》2003,38(Z1):101-103
全球变暖给钢铁工业带来了巨大的挑战,挑战涉及使用碳的多少和能量利用率.低强度生产可以短期内达到减轻排放,使处于京都协议要求的水平.从中期看,更多地使用废钢也有助于减轻排放.但是为了实现更多地减少温室气体GHG的排放,也即等于实现京都协议之后的排放目标,钢铁工业必须设想有一个新的生产面貌,这形成了未来时期对它的最大挑战.碳的收集和吸收,碳使用中的代用剂,工艺流程中绿色来源的电和氢的应用,这些在未来10年中是必须要发展的,希望通过广泛地国际合作加以实现. 相似文献
74.
There is a growing trend of research in neuropsychological assessment in Asia: The mean number of published studies increased from 1.8 in the 1980s to 16.0 in 2 recent years. About 40% of the studies reviewed concerned test development or adaptation, with the latter greatly outnumbering the former. To facilitate the test selection for clinical use, 36 clinical measures were evaluated based on some statistical criteria. The results showed that only 8 neuropsychological tests (5 Chinese. 2 Korean, and 1 Japanese) met the criteria. Given that Asian and Western populations differ on certain cognitive processes, future development of neuropsychological assessment measures in Asia should move from the adaptation of Western tests toward the construction of original tests with better ecological validity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
David M. Scott Debendra K. Das Vijayagandeeban Subbaihaannadurai 《Petroleum Science and Technology》2006,24(8):895-909
A finite element scheme is presented to model the dissociation of gas hydrates in porous media by hot water injection. We show a complete derivation of the finite element formulation, including the associated mass and energy conservation equations capable of performing transient analysis of both conductive and convective heat transfer for gas and liquid flow in porous media. The scheme also includes the latent heat effect to accommodate the change of phase due to melting of hydrate. In the companion paper, Part II, this method is successfully applied to hydrate reservoirs. 相似文献
76.
The accuracy of the prediction of criminal violence may be improved by combining psychopathy with other variables that have been found to predict violence. Research has suggested that assessing intelligence (i.e., IQ) as well as psychopathy improves the accuracy of violence prediction. In the present study, the authors tested this hypothesis by using a contemporary measure of psychopathy, the Psychopathy Checklist-Revised (R. D. Hare, 2003), in a sample of 326 European American and 348 African American male offenders. The postdictive power of psychopathy was evident for both ethnic groups and robust across most changes in the operationalization of violence and the analysis conducted, whereas the postdictive power of IQ was not. No Psychopathy x IQ interactions were identified. Implications of these results for violence prediction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
We have developed and implemented techniques that double the performance of dynamically-typed object-oriented languages. Our SELF implementation runs twice as fast as the fastest Smalltalk implementation, despite SELF's lack of classes and explicit variables.To compensate for the absence of classes, our system uses implementation-levelmaps to transparently group objects cloned from the same prototype, providing data type information and eliminating the apparent space overhead for prototype-based systems. To compensate for dynamic typing, user-defined control structures, and the lack of explicit variables, our system dynamically compilesmultiple versions of a source method, eachcustomized according to its receiver's map. Within each version the type of the receiver is fixed, and thus the compiler can statically bind andinline all messages sent toself.Message splitting andtype prediction extract and preserve even more static type information, allowing the compiler to inline many other messages. Inlining dramatically improves performance and eliminates the need to hard-wire low-level methods such as+, ==, andifTrue:.Despite inlining and other optimizations, our system still supports interactive programming environments. The system traverses internal dependency lists to invalidate all compiled methods affected by a programming change. The debugger reconstructs inlined stack frames from compiler-generated debugging information, making inlining invisible to the SELF programmer.This work has been generously supported by National Science Foundation Presidential Young Investigator Grant #CCR-8657631, and by IBM, Texas Instruments, NCR, Tandem Computers, Apple Computer, and Sun Microsystems.This paper was originally published inOOPSLA '89 Conference Proceedings (SIGPLAN Notices, 25, 10 (1989) 49–70). 相似文献
78.
David Mills 《Granular Matter》2004,6(2-3):173-177
For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem. 相似文献
79.
80.
Bissessur H. Charlet G. Gohin E. Simonneau C. Pierre L. Idler W. 《Electronics letters》2003,39(2):192-193
By transmitting 40 channels over 300 km of TeraLight fibre, it is shown that optical differential phase shift keying can be used in 100 GHz-spaced 40 Gbit/s systems, with direct detection and a simple receiving filter. Chromatic dispersion tolerance around 300 ps/nm is also measured, compared to 70 ps/nm for NRZ. 相似文献