全文获取类型
收费全文 | 225126篇 |
免费 | 23902篇 |
国内免费 | 15229篇 |
专业分类
电工技术 | 14223篇 |
技术理论 | 83篇 |
综合类 | 24889篇 |
化学工业 | 26725篇 |
金属工艺 | 5451篇 |
机械仪表 | 10021篇 |
建筑科学 | 35423篇 |
矿业工程 | 10836篇 |
能源动力 | 5173篇 |
轻工业 | 15863篇 |
水利工程 | 11077篇 |
石油天然气 | 11189篇 |
武器工业 | 2888篇 |
无线电 | 18283篇 |
一般工业技术 | 17259篇 |
冶金工业 | 8377篇 |
原子能技术 | 1590篇 |
自动化技术 | 44907篇 |
出版年
2024年 | 994篇 |
2023年 | 3361篇 |
2022年 | 7535篇 |
2021年 | 8715篇 |
2020年 | 7369篇 |
2019年 | 5997篇 |
2018年 | 6071篇 |
2017年 | 7363篇 |
2016年 | 9557篇 |
2015年 | 10487篇 |
2014年 | 17216篇 |
2013年 | 14607篇 |
2012年 | 15967篇 |
2011年 | 16078篇 |
2010年 | 12748篇 |
2009年 | 12998篇 |
2008年 | 12612篇 |
2007年 | 15511篇 |
2006年 | 14525篇 |
2005年 | 12672篇 |
2004年 | 10187篇 |
2003年 | 8753篇 |
2002年 | 6532篇 |
2001年 | 5061篇 |
2000年 | 4280篇 |
1999年 | 3210篇 |
1998年 | 2340篇 |
1997年 | 1970篇 |
1996年 | 1760篇 |
1995年 | 1429篇 |
1994年 | 1210篇 |
1993年 | 863篇 |
1992年 | 719篇 |
1991年 | 555篇 |
1990年 | 415篇 |
1989年 | 427篇 |
1988年 | 272篇 |
1987年 | 204篇 |
1986年 | 177篇 |
1985年 | 173篇 |
1984年 | 187篇 |
1983年 | 128篇 |
1982年 | 94篇 |
1981年 | 103篇 |
1980年 | 87篇 |
1979年 | 55篇 |
1966年 | 41篇 |
1965年 | 45篇 |
1964年 | 60篇 |
1962年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
D. Roy 《International journal for numerical methods in engineering》2004,61(5):764-790
Sample pathwise numerical integration of noise-driven engineering dynamical systems cannot generally be performed beyond a limited level of accuracy, especially when the noise processes are modelled using (filtered) white noises. Recently, a locally transversal linearization (LTL) strategy has been proposed by the author (Proc Roy Soc London A 2001; 457 :539–566) for direct integration of deterministic and stochastic non-linear dynamical systems. The present effort is focussed on a host of extensions along with detailed theoretical error analyses of the linearization approach, especially as applied to problems in non-linear stochastic engineering dynamics. Thus, to begin with, estimates of local and global error orders in the basic LTL scheme are obtained separately for the displacement and velocity vectors when the system is driven either by a set of additive noises or by an arbitrary combination of (independently evolving) additive and multiplicative noises. Following this, a new family of higher-order LTL schemes is proposed in order to improve upon the basic LTL method and the associated error orders are established. A stepwise implementation of the lower- and higher-order versions of the LTL method, along with certain computational aspects, is also outlined. The proposed schemes are numerically illustrated, to a limited extent, for a single degree-of-freedom (SDOF) and a two degree-of-freedom (TDOF) non-linear engineering systems under additive and/or multiplicative white noise excitations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
122.
Youngjoong Ko Sooyong Park Jungyun Seo Soonhwang Choi 《Information and Software Technology》2007,49(11-12):1128-1140
In order to efficiently develop large-scale and complicated software, it is important for system engineers to correctly understand users’ requirements. Most requirements in large-scale projects are collected from various stakeholders located in various regions, and they are generally written in natural language. Therefore, the initial collected requirements must be classified into various topics prior to analysis phases in order to be usable as input in several requirements analysis methods. If this classification process is manually done by analysts, it becomes a time-consuming task. To solve this problem, we propose a new bootstrapping method which can automatically classify requirements sentences into each topic category using only topic words as the representative of the analysts’ views. The proposed method is verified through experiments using two requirements data sets: one written in English and the other in Korean. The significant performances were achieved in the experiments: the 84.28 and 87.91 F1 scores for the English and Korean data sets, respectively. As a result, the proposed method can provide an effective function for an Internet-based requirements analysis-supporting system so as to efficiently gather and analyze requirements from various and distributed stakeholders by using the Internet. 相似文献
123.
Kyle A. Crawford
Osama K. Eyada PhD PE
《Computers & Industrial Engineering》1989,17(1-4):298-302The worldwide proliferation of fraudulent materials has brought about the need for a new approach to the control of purchased material quality. Nuclear power, defense, aerospace and many other industries are affected by the supply of poor quality clones that presume to be original replacement parts. Safety considerations abound as these highly defective materials are used in systems that are critical to the preservation of human lives. Commonly utilized quality assurance programs have not effectively stopped the influx of fraudulent materials. These programs fail to concentrate inspection efforts on materials and inspection attributes that would effectively prevent the acceptance of fraudulent materials. herein a solution is presented to this problem in the form of an expert system application. Information commonly available in industry is formulated into a knowledge based system wherein advisories are given to the user regarding key purchased material receipt inspection strategies. 相似文献
124.
Rudolf Habison 《International Journal of Project Management》1985,3(3):178-181
Meeting time and cost objectives in complex projects involves specific problems and risks. An attempt is made to analyse the components of total cost increase of a project caused by time delay. An outline is given as to how these considerations can be used to estimate cost increases in investors' decision situations as well as to ascertain fair contractual penalties and claims for compensation and for the evaluation of justified project acceleration costs. 相似文献
125.
126.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
127.
结合山西焦化公司内部网建设实践,分析了建设企业内部网的技术选择,阐述了以太网技术在大中型化工企业网络建设中的具体应用。指出建立信息网络将缩小企业与国外企业之间的营销能力差异,增强我国企业的竞争力。 相似文献
128.
129.
Patricio Toro Raúl Quijada Omar Murillo Mehrdad Yazdani‐Pedram 《Polymer International》2005,54(4):730-734
The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry 相似文献
130.
This paper studies a Kansas Department of Transportation welded plate girder bridge that developed fatigue cracks at small web gaps close to the girder top flange. Repair had been previously performed by softening the connection plate end with a slot retrofit, but cracks were recently found to have reinitiated at some of the repaired details and are again propagating. A comprehensive finite-element method study was performed to investigate the cracking behavior observed in the bridge and to recommend appropriate measures for future bridge retrofit. The analytical results show that stresses developed at the top flange web gaps could exceed yielding under the loading of an HS15 fatigue truck. The current slot repair used in the bridge was found to have introduced higher magnitude fatigue stresses in the web gap. To achieve a permanent repair of the bridge, it is recommended that a welded connection plate to flange attachment be used during future bridge retrofit. The web gap details should be able to withstand unlimited number of load cycles once this additional repair is performed. 相似文献