全文获取类型
收费全文 | 1005篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 18篇 |
综合类 | 4篇 |
化学工业 | 239篇 |
金属工艺 | 27篇 |
机械仪表 | 37篇 |
建筑科学 | 20篇 |
能源动力 | 137篇 |
轻工业 | 52篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
无线电 | 85篇 |
一般工业技术 | 220篇 |
冶金工业 | 67篇 |
原子能技术 | 3篇 |
自动化技术 | 126篇 |
出版年
2023年 | 16篇 |
2022年 | 28篇 |
2021年 | 34篇 |
2020年 | 24篇 |
2019年 | 36篇 |
2018年 | 37篇 |
2017年 | 39篇 |
2016年 | 34篇 |
2015年 | 19篇 |
2014年 | 38篇 |
2013年 | 86篇 |
2012年 | 46篇 |
2011年 | 59篇 |
2010年 | 41篇 |
2009年 | 50篇 |
2008年 | 42篇 |
2007年 | 34篇 |
2006年 | 24篇 |
2005年 | 27篇 |
2004年 | 25篇 |
2003年 | 17篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 4篇 |
1999年 | 11篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有1041条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - Now-a-days the most common pretentious disease is the lung cancer, which has become more prevalent in the world that primarily infects the pulmonary nodules of... 相似文献
2.
3.
4.
Beneficial effects of wettability altering surfactants in oil-wet fractured reservoirs 总被引:3,自引:0,他引:3
Subhash C. Ayirala Chandra S. Vijapurapu Dandina N. Rao 《Journal of Petroleum Science and Engineering》2006,52(1-4):261
In fractured reservoirs, an effective matrix-fracture mass transfer is required for oil recovery. Surfactants have long been considered for oil recovery enhancement, mainly in terms of their ability to reduce oil–water interfacial tension. These surfactants are effective when the fractured formations are water-wet, where capillary imbibition of surfactants from the fracture into the matrix contributes to oil recovery. However, another beneficial aspect of surfactants, namely their ability to alter wettability, remains to be explored and exploited. Surfactants capable of altering wettability can be especially beneficial in oil-wet fractured formations, where the surfactant in the fracture diffuses into the matrix and alters the wettability, enabling imbibition of even more surfactant into the matrix. This sequential process of initial diffusion followed by imbibition continues well into the matrix yielding significant enhancements in oil recovery.In order to test this hypothesis of sequential diffusion–imbibition phenomenon, Dual-Drop Dual-Crystal (DDDC) contact angle experiments have been conducted using fractured Yates dolomite reservoir fluids, two types of surfactants (nonionic and anionic) and dolomite rock substrates. A new experimental procedure was developed in which crude oil equilibrated with reservoir brine has been exposed to surfactant to simulate the matrix-fracture interactions in fractured reservoirs. This procedure enables the measurements of dynamic contact angles and oil–water interfacial tensions, in addition to providing the visual observations of the dynamic behavior of crude oil trapped in the rock matrix as it encounters the diffusing surfactant from the fractures. Both the measurements and visual observations indicate wettability alterations of the matrix surface from oil-wet to less oil-wet or intermediate wet by the surfactants. Thus this study is of practical importance to oil-wet fractured formations where surfactant-induced wettability alterations can result in significant oil recovery enhancements. In addition, this study has also identified the need to include contact angle term in the dimensionless Bond number formulations for better quantitative interpretation of rock–fluids interactions. 相似文献
5.
We propose a space-efficient scheme for summarizing multidimensional data streams. Our sketch can be used to solve spatial
versions of several classical data stream queries efficiently. For instance, we can track ε-hot spots, which are congruent
boxes containing at least an ε fraction of the stream, and maintain hierarchical heavy hitters in d dimensions. Our sketch
can also be viewed as a multidimensional generalization of the ε-approximate quantile summary. The space complexity of our
scheme is O((1/ε) log R) if the points lie in the domain [0, R]d, where d is assumed to be a constant. The scheme extends to the sliding window model with a log (ε n) factor increase in
space, where n is the size of the sliding window. Our sketch can also be used to answer ε-approximate rectangular range queries
over a stream of d-dimensional points. 相似文献
6.
Bayesian and Dempster-Shafer fusion 总被引:3,自引:0,他引:3
The Kalman Filter is traditionally viewed as a prediction-correction filtering algorithm. In this work we show that it can
be viewed as a Bayesian fusion algorithm and derive it using Bayesian arguments. We begin with an outline of Bayes theory,
using it to discuss well-known quantities such as priors, likelihood and posteriors, and we provide the basic Bayesian fusion
equation. We derive the Kalman Filter from this equation using a novel method to evaluate the Chapman-Kolmogorov prediction
integral. We then use the theory to fuse data from multiple sensors. Vying with this approach is the Dempster-Shafer theory,
which deals with measures of “belief”, and is based on the nonclassical idea of “mass” as opposed to probability. Although
these two measures look very similar, there are some differences. We point them out through outlining the ideas of the Dempster-Shafer
theory and presenting the basic Dempster-Shafer fusion equation. Finally we compare the two methods, and discuss the relative
merits and demerits using an illustrative example. 相似文献
7.
R Albrecht TC Awes C Baktash P Beckmann F Berger R Bock G Claesson G Clewing L Dragon A Eklund RL Ferguson A Franz S Garpman R Glasow HA Gustafsson HH Gutbrod J Idh P Jacobs K Kampert BW Kolb P Kristiansson IY Lee H Loehner I Lund FE Obenshain A Oskarsson I Otterlund T Peitzmann S Persson F Plasil AM Poskanzer M Purschke H Ritter S Saini R Santo HR Schmidt T Siemiarczuk SP Sorensen E Stenlund ML Tincknell GR Young 《Canadian Metallurgical Quarterly》1991,44(6):2736-2752
8.
Susan J. Masten Kuan‐Chung Chen Jaime Graulau Subhash L. Kari Kyung‐Hyuk Lee 《工程教育杂志》2002,91(1):69-80
The use of computer‐based technology is becoming more prevalent in the classroom. As a part of an educational research project sponsored by the GE Foundation, strategies for augmenting a course, Introduction to Environmental Engineering (CE 280), were investigated including cross‐disciplinary experiences in teamwork, design, and the use of advanced teaching technologies such as the web. Interactive tools to assist student learning were developed and refined. Efforts have focused on developing an extensive website, web‐based quizzes and homework assignments, and tutorials. Base groups were used to provide both intellectual and emotional support to students. This paper summarizes the development of this course and the impact of rapid feedback on the progression of student understanding. 相似文献
9.
Current desktop computers typically use fan-heat sinks for cooling the CPU, referred to as active heat sinks. This work seeks to determine the heat rejection limits for such fan-heat sinks, within specific fan and heat sink space limits. A fixed volume, 80 /spl times/ 60 /spl times/ 50 mm is chosen as the limiting dimensions, which includes the fan volume. The present work addresses plane fin heat sinks, on which a typical 60 mm fan is mounted. Both duct flow and impinging flow are considered. Analytically based models are used to predict the optimum geometry (minimum convection resistance) for plane fins with duct and impinging flow configurations. Also assessed are the effects of increased fan speed (up to 25%) and heat sink base size (33% increase) on air-cooling limits in duct and impinging flow. Tests on fan-heat sinks are done to validate the predictions. Optimization is also done for an enhanced (offset-strip) fin geometry in duct flow. The plane fin is found to outperform the enhanced geometry. 相似文献
10.
Changes in the NHS have supported the idea of targeting health services to those in greatest need. This has meant that health visitors are increasingly having to identify 'vulnerable' families in need of increased health visiting intervention. This paper reports on a qualitative study undertaken in order to explore the ways in which health visitors plan and organize their work in relation to the concept of vulnerability. Focus groups and semi-structured interviews were carried out with health visitors from two separate geographical areas, one an inner city area and the other suburban, in order to explore the criteria by which health visitors define vulnerability and decide to increase their levels of intervention to particular families. It was found that vulnerability was extremely difficult to define but that the health visitors used criteria which were appropriate to the particular localities in which they worked to identify vulnerable families and to increase their levels of intervention to those families. Health visitors were targeting their services within a framework of a basic minimum service to all and were assessing the health needs of individuals or families rather than planning their work on the basis of community or practice profiles. 相似文献