全文获取类型
收费全文 | 10857篇 |
免费 | 1978篇 |
国内免费 | 1406篇 |
专业分类
电工技术 | 637篇 |
综合类 | 1102篇 |
化学工业 | 291篇 |
金属工艺 | 206篇 |
机械仪表 | 823篇 |
建筑科学 | 204篇 |
矿业工程 | 217篇 |
能源动力 | 224篇 |
轻工业 | 192篇 |
水利工程 | 134篇 |
石油天然气 | 417篇 |
武器工业 | 227篇 |
无线电 | 2556篇 |
一般工业技术 | 692篇 |
冶金工业 | 276篇 |
原子能技术 | 45篇 |
自动化技术 | 5998篇 |
出版年
2024年 | 49篇 |
2023年 | 149篇 |
2022年 | 354篇 |
2021年 | 345篇 |
2020年 | 372篇 |
2019年 | 354篇 |
2018年 | 337篇 |
2017年 | 448篇 |
2016年 | 529篇 |
2015年 | 603篇 |
2014年 | 815篇 |
2013年 | 730篇 |
2012年 | 929篇 |
2011年 | 909篇 |
2010年 | 848篇 |
2009年 | 826篇 |
2008年 | 838篇 |
2007年 | 855篇 |
2006年 | 712篇 |
2005年 | 621篇 |
2004年 | 466篇 |
2003年 | 444篇 |
2002年 | 313篇 |
2001年 | 248篇 |
2000年 | 203篇 |
1999年 | 168篇 |
1998年 | 145篇 |
1997年 | 126篇 |
1996年 | 75篇 |
1995年 | 70篇 |
1994年 | 67篇 |
1993年 | 42篇 |
1992年 | 36篇 |
1991年 | 25篇 |
1990年 | 30篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The history of computer modelling of the Wairakei geothermal field is reviewed. It covers the development of lumped-parameter models during the 1970s and then discusses the evolution and first applications of geothermal reservoir simulation techniques. The development of reservoir models of Wairakei at the University of Auckland began in the early 1980s; current models produces good matches against field data. Many future scenarios have been run using the University's models and have been presented at various regulatory hearings. The general conclusion from these scenarios is that Wairakei can continue producing electricity at the current level for at least another 50 years, and if Wairakei is shut down after 100 years of operation it will recover to its pre-exploitation state after a further 300 years. 相似文献
992.
Two important forces in human behavior are action and inaction. Although action and inaction are commonly associated with the presence and the absence of behavioral activity, they can also be represented as information processing goals. Action (inaction) goals influence decision effort and increase satisfaction with environments that are structured to allow for more (less) processing (Studies 1 and 2). This increased satisfaction can transfer to the decision (Study 3) and can increase the intent to perform a decision-congruent behavior (Studies 4 and 6). Finally, the author shows escalation of action and inaction goals when they are not achieved (Study 5) and rebound of the alternative goal when the focal goal is achieved (Study 6). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Abstract Real-time model-based reservoir management requires efficient computational techniques for optimizing reservoir performance under uncertainty. A variety of algorithms addressing various aspects of this “closed-loop” methodology have been presented by various investigators, but substantial effort is still needed to make the entire process robust and efficient. In our recent work, we introduced an approximate feasible direction optimization algorithm for treating nonlinear path constraints (which are constraints such as maximum liquid production rate, which must be satisfied at every time step) and a new parameterization based on kernel principal component analysis (KPCA) for multipoint geostatistical models. The KPCA representation allows for the use of a gradient-based history-matching procedure that is able to maintain a higher degree of geological realism in the history-matched model. In this article, we combine these procedures with our general adjoint-based optimization technique to provide a full closed-loop capability. This integrated set of algorithms is then applied to a realistic field case. Specifically, we describe the key computational procedures and highlight the linkages required to provide the closed-loop capability. The example case considered is based on a Gulf of Mexico reservoir and involves three injection wells and four production wells operating under bottom hole pressure, total injection rate, and maximum water cut constraints. For this case, it is demonstrated that application of the closed-loop methodology provides a 25% increase in the net present value (NPV) over predictions for a realistic base case. This improvement is almost the same as that achieved using an open-loop approach, which is an idealized formulation in which the geological model is assumed to be known. These results demonstrate that the overall closed-loop procedure will indeed be applicable for practical cases with uncertain geology. 相似文献
994.
During the past years, several papers have been published that question the use of the CIE colour‐matching functions in the case of metameric samples. Visually matching samples produced on CRT (Cathode Ray Tube) monitors are metameric to most colour stimuli created by illuminating reflecting materials. As CRT monitors are often used in colour design applications, it seemed important to check how well CIE colorimetry will predict such colour matches. To investigate this problem, we set up an experiment in which painted samples were matched with samples produced on a CRT monitor. The colour of incandescent lamp irradiated Munsell samples were visually matched to the mixture of the RGB primaries of a CRT monitor. Both the reflected colour stimuli of the Munsell samples and the emitted stimuli of the monitor were measured spectroradiometrically. Our results imply that there is an observer‐dependent variability among the matches, but we could not find a major difference between the tristimulus data of the hard copy and soft copy presentations that would indicate errors in the CIE colour‐matching functions. The measurement accuracy, quantization errors of the monitor, and the achieved accuracy of the colour matches are treated in this study. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 436–441, 2001 相似文献
995.
996.
997.
四环阵天线技术 ,从美国引进以来 ,在 15 0 - 40 0 M频段各类通信系统中 ,已得到了极为广泛的应用 ,但迄今为止 ,尚未见到对这种天线进行讨论的专门文献。作者根据多年来的实践工作与设计经验 ,对四环阵天线进行了基本的分析 ,特别是对有重要实用价值的赋形波瓣异型四环阵的设计进行了充分的讨论。 相似文献
998.
999.
1000.
With the increasing number of available XML documents, numerous approaches for retrieval have been proposed in the literature. They usually use the tree representation of documents and queries to process them, whether in an implicit or explicit way. Although retrieving XML documents can be considered as a tree matching problem between the query tree and the document trees, only a few approaches take advantage of the algorithms and methods proposed by the graph theory. In this paper, we aim at studying the theoretical approaches proposed in the literature for tree matching and at seeing how these approaches have been adapted to XML querying and retrieval, from both an exact and an approximate matching perspective. This study will allow us to highlight theoretical aspects of graph theory that have not been yet explored in XML retrieval. 相似文献