全文获取类型
收费全文 | 32331篇 |
免费 | 1414篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 343篇 |
综合类 | 56篇 |
化学工业 | 7043篇 |
金属工艺 | 601篇 |
机械仪表 | 588篇 |
建筑科学 | 1895篇 |
矿业工程 | 77篇 |
能源动力 | 888篇 |
轻工业 | 2694篇 |
水利工程 | 295篇 |
石油天然气 | 166篇 |
武器工业 | 3篇 |
无线电 | 2315篇 |
一般工业技术 | 5951篇 |
冶金工业 | 5263篇 |
原子能技术 | 207篇 |
自动化技术 | 5396篇 |
出版年
2023年 | 278篇 |
2022年 | 453篇 |
2021年 | 700篇 |
2020年 | 507篇 |
2019年 | 597篇 |
2018年 | 730篇 |
2017年 | 695篇 |
2016年 | 908篇 |
2015年 | 820篇 |
2014年 | 1034篇 |
2013年 | 1935篇 |
2012年 | 1680篇 |
2011年 | 2140篇 |
2010年 | 1517篇 |
2009年 | 1471篇 |
2008年 | 1772篇 |
2007年 | 1658篇 |
2006年 | 1452篇 |
2005年 | 1233篇 |
2004年 | 1101篇 |
2003年 | 951篇 |
2002年 | 918篇 |
2001年 | 544篇 |
2000年 | 527篇 |
1999年 | 537篇 |
1998年 | 507篇 |
1997年 | 454篇 |
1996年 | 469篇 |
1995年 | 444篇 |
1994年 | 436篇 |
1993年 | 432篇 |
1992年 | 388篇 |
1991年 | 233篇 |
1990年 | 323篇 |
1989年 | 323篇 |
1988年 | 273篇 |
1987年 | 296篇 |
1986年 | 288篇 |
1985年 | 308篇 |
1984年 | 270篇 |
1983年 | 257篇 |
1982年 | 243篇 |
1981年 | 211篇 |
1980年 | 177篇 |
1979年 | 185篇 |
1978年 | 165篇 |
1977年 | 138篇 |
1976年 | 125篇 |
1975年 | 139篇 |
1974年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Remanufacturing facilities usually face a trade-off between limited information about remanufacturing yields and potentially long supplier lead times. To improve production performance, these firms may attempt to acquire more timely and accurate information about remanufacturing yields or alternatively, to reduce the lead times of purchased parts. We develop four decision-making models to evaluate the impact of yield information and supplier lead time on manufacturing costs. We identify the operating conditions under which these capabilities are valuable, along with their relative impact on facility performance. Each model is formulated as an infinite horizon, stochastic dynamic program (Markov decision process). Our results indicate that the yield information is generally quite valuable, while investments in supplier responsiveness provide trivial returns to products with few parts. However, as product complexity increases with large number of target parts, the value of short lead times increases. 相似文献
2.
Separation tests using hollow-fibre modules were performed for the difficult selective extraction of trivalent actinides over fission lanthanides from acidic media. This article shows that with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine as the extractant, up to 94% americium could be extracted from 1.0 kmol/m3 HNO3, with minimal lanthanide co-extraction. Using a synergistic mixture of bis(chlorophenyl)dithiophosphinic acid and tri-n-octyl phosphine oxide, tests were performed on extraction, lanthanide scrubbing and stripping. In the extraction test, up to 99.99% americium could be extracted from 0.5 kmol/m3 HNO3, with approximately one third of the lanthanides being co-extracted. Mass transfer calculations using a consistent set of input data showed good agreement with the experiments. 相似文献
3.
Maher M. Osman Mounir M. Abd El-Malek Aida B. Tadros Atef M. Michael 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):46-52
4-Amino-3-thio-1,24-triazolidine (L1) and 4-amino-5-thio-1,3,4-thiadiazole (LII) as well as their metal complexes of the general formulae MLI·2H2O and MLIICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(LI)2·2H2O and SnLIICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae. 相似文献
4.
Michael Winder 《Information Systems Management》1994,11(4):65-68
Midrange outsourcers offer small to midsize companies the advanced technologies employed by major corporations, with the added benefits of creative pricing strategies. 相似文献
5.
By analyzing an oblique ionogram several characteristics, such as LOF, MOF, FMUF, FHLOF, FLLOF, and 2FMOF, can be found. These characteristics are important both for ionospheric studies and for terrestrial communication purposes, as they give information about the sky wave communication conditions in the High Frequency (HF) radio spectrum.A RCS-5B sweeping HF receiver for oblique sounding was installed at Chania (Crete, Greece, 35.7°N, 24.0°E) in April 2005 to perform a radio link with Inskip (UK, 53.5°N, 2.5°W). The receiver, able to record the sounding only as a binary file, was not equipped with a tool to display and scale the recorded trace. This work describes software that is able to do this, consequently increasing the speed of the scaling phase performed by the operator. The usefulness of this software for validating FMUF prediction models is also shown. 相似文献
6.
Anastasiya Rybak Patrice A. Fokou Michael A. R. Meier 《European Journal of Lipid Science and Technology》2008,110(9):797-804
Olefin metathesis, awarded with the Nobel Prize in Chemistry 2005 for Chauvin, Grubbs and Schrock, has emerged as a powerful tool for organic as well as polymer chemistry. In oleochemistry, this reaction is well known and has been applied for many decades. Examples include the functionalization of the double bonds of different oleochemicals or the (direct) polymerization of plant oils via metathesis. More recent developments, particularly the development of better and more robust catalysts, allow for highly efficient cross‐metathesis reactions opening new possibilities for the direct introduction of chemical functionalities. Within this contribution, the development of metathesis in oleochemistry will be discussed, covering self‐metathesis as well as more recent developments in the field of cross‐metathesis that lead to desired platform chemicals. 相似文献
7.
8.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
9.
Michael E. G. Ferguson Peter L. Spedding 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):262-278
Experimental data for air–water two-phase co-current flow in two different pipe diameters were used to test the prediction of pressure drop by a number of existing theories and correlations. Several models are shown to be useful for prediction, particularly with the stratified regimes which have proved difficult to handle in the past. The model suggested by Olujic proved to be of particular value. 相似文献
10.