全文获取类型
收费全文 | 636704篇 |
免费 | 8509篇 |
国内免费 | 1914篇 |
专业分类
电工技术 | 12046篇 |
综合类 | 878篇 |
化学工业 | 95774篇 |
金属工艺 | 21914篇 |
机械仪表 | 18054篇 |
建筑科学 | 17307篇 |
矿业工程 | 1578篇 |
能源动力 | 17312篇 |
轻工业 | 63683篇 |
水利工程 | 5155篇 |
石油天然气 | 5163篇 |
武器工业 | 21篇 |
无线电 | 81490篇 |
一般工业技术 | 117873篇 |
冶金工业 | 120480篇 |
原子能技术 | 9433篇 |
自动化技术 | 58966篇 |
出版年
2021年 | 4445篇 |
2019年 | 4106篇 |
2018年 | 6700篇 |
2017年 | 6604篇 |
2016年 | 6934篇 |
2015年 | 5402篇 |
2014年 | 9002篇 |
2013年 | 29881篇 |
2012年 | 15501篇 |
2011年 | 22018篇 |
2010年 | 17074篇 |
2009年 | 19448篇 |
2008年 | 20717篇 |
2007年 | 20854篇 |
2006年 | 18673篇 |
2005年 | 17295篇 |
2004年 | 16838篇 |
2003年 | 16403篇 |
2002年 | 15897篇 |
2001年 | 16050篇 |
2000年 | 15117篇 |
1999年 | 16019篇 |
1998年 | 37305篇 |
1997年 | 27065篇 |
1996年 | 21328篇 |
1995年 | 16587篇 |
1994年 | 14946篇 |
1993年 | 14333篇 |
1992年 | 10710篇 |
1991年 | 10293篇 |
1990年 | 9835篇 |
1989年 | 9478篇 |
1988年 | 9126篇 |
1987年 | 7670篇 |
1986年 | 7766篇 |
1985年 | 9278篇 |
1984年 | 8559篇 |
1983年 | 7724篇 |
1982年 | 7126篇 |
1981年 | 7195篇 |
1980年 | 6755篇 |
1979年 | 6520篇 |
1978年 | 6099篇 |
1977年 | 7412篇 |
1976年 | 9900篇 |
1975年 | 5230篇 |
1974年 | 5005篇 |
1973年 | 4929篇 |
1972年 | 3977篇 |
1971年 | 3490篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
Industries in the US continue to lose ground in international competition. If IS is to help change that trend, it will have to become more creative. Creativity improvement programs are being introduced in other areas of the company— now is the time for IS organizations to follow suit. 相似文献
212.
Although not well known, the University of Toronto had a very early computer-development program and in 1952 was one of the first few institutions with an operable computer in North America. This article describes the university's initial attempt to build the UTEC computer and how it acquired the pioneering Ferut machine 相似文献
213.
É. R. Smolyakov 《Cybernetics and Systems Analysis》1994,30(1):10-17
Translated from Kibernetika i Sistemnyi Analiz, No. 1, pp. 24–33, January–February, 1994. 相似文献
214.
In the editorial by J.C. Bezdek (ibid., p.1), an example is presented to demonstrate differences between fuzzy membership and probability. The authors argue that probability can be used in a way much more closely analogous to this use of fuzzy membership, weakening the argument for the latter 相似文献
215.
First break picking is a pattern recognition problem in seismic signal processing, one that requires much human effort and is difficult to automate. The authors' goal is to reduce the manual effort in the picking process and accurately perform the picking. Feedforward neural network first break pickers have been developed using backpropagation training algorithms applied either to an encoded version of the raw data or to derived seismic attributes which are extracted from the raw data. The authors summarize a study in which they applied a backpropagation fuzzy logic system (BPFLS) to first break picking. The authors use derived seismic attributes as features, and take lateral variations into account by using the distance to a piecewise linear guiding function as a new feature. Experimental results indicate that the BPFLS achieves about the same picking accuracy as a feedforward neural network that is also trained using a backpropagation algorithm; however, the BPFLS is trained in a much shorter time, because there is a systematic way in which the initial parameters of the BPFLS can be chosen, versus the random way in which the weights of the neural network are chosen 相似文献
216.
Panagiotis N. Zarros Myung J. Lee Tarek N. Saadawi 《Journal of Network and Systems Management》1994,2(4):361-382
In this paper, an algorithm to determine the set of packets generated continuously and periodically from different participants that are arriving at a node either for mixing at the master of a conference, or for simply playing back at a regular participant of a conference, is proposed. The essence of the algorithm is to estimate the expected packet arrival time (or reference time) for each participant. With the reference time at hand, the maximum jitter and the optimum waiting time for a mixer to wait packets from all participants can be determined. An enhancement to improve synchronization which deals with the estimation of the time offsets between the individual periods of the sources and the period of the receiver is also presented. The error of the proposed algorithm is enumerated by the Chernoff bound and demonstrated by simulation and is shown to be acceptable in practical application. The algorithm can also be employed when traffic sources operate with different periods. 相似文献
217.
Robotica is a computer aided design package for robotic manipulators developed in the Coordinated Science Laboratory at the University of Illinois at Urbana-Champaign. It encapsulates over 30 functions into a Mathematica package allowing efficient symbolic and numeric calculation of kinematic and dynamic equations for multi-degree-of-freedom manipulators. An X-Windows front end that utilizes the interprocess communication features of Mathematica 2.1 has also been created for ease of use. This paper describes the most important features of the package and how they are used 相似文献
218.
Vascular injuries may occur as complications of elbow dislocation and usually involve the brachial artery. A case report is presented in which only the radial artery was compromised as a result of the dislocation. 相似文献
219.
R Thomas 《Canadian Metallurgical Quarterly》1993,15(4):285-289
The purpose for this study was to evaluate the results of silicone oil use in patients who have undergone vitrectomy for proliferative vitreoretinopathy (PVR). The authors reviewed the 5-year results of 50 consecutive patients (52 eyes) with grade C1/D3 PVR operated on in 1987. Silicone oil has been removed in 42 eyes. The retina remained attached in 38 eyes. Visual acuities were finger counting in 12 eyes and 0.1 or greater in 19 eyes. Glaucoma was thought to be the major cause of loss of visual acuity after an initial improvement (9 eyes), as well as the most frequent complication of surgery (13 eyes). Silicone oil was deemed nonremovable in 10 operated eyes. A questionnaire was developed to determine the patients' perceptions of the use of silicone oil, and 46 patients responded to the questionnaire. Four patients indicated that they would not have elected to have surgery again. Six patients thought that surgery was not worthwhile, but would permit treatment again. Most patients thought that a modest amount of improvement had taken place and that vision was stable. Subjectively, most patients believed that surgery was worthwhile. 相似文献
220.
Variations in lipid profile and incidence of vascular events were evaluated. Group 1 had a 29.3% reduction of total and a 38.3% reduction of LDL cholesterol as against reductions of 9% and 9.6% respectively in group 2. No significant difference was observed between the two groups as far as the vascular events considered were concerned. Pravastatin is an effective and safe drug. The lack of influence on the evolution of vascular disease would appear to be correlated to the small number of subjects studied and the short follow-up. 相似文献