全文获取类型
收费全文 | 312311篇 |
免费 | 3867篇 |
国内免费 | 716篇 |
专业分类
电工技术 | 6204篇 |
综合类 | 562篇 |
化学工业 | 47414篇 |
金属工艺 | 10335篇 |
机械仪表 | 8838篇 |
建筑科学 | 8089篇 |
矿业工程 | 869篇 |
能源动力 | 8616篇 |
轻工业 | 31414篇 |
水利工程 | 2569篇 |
石油天然气 | 3673篇 |
武器工业 | 8篇 |
无线电 | 39833篇 |
一般工业技术 | 58828篇 |
冶金工业 | 57139篇 |
原子能技术 | 5463篇 |
自动化技术 | 27040篇 |
出版年
2021年 | 2432篇 |
2019年 | 2237篇 |
2018年 | 3714篇 |
2017年 | 3530篇 |
2016年 | 3636篇 |
2015年 | 2599篇 |
2014年 | 4531篇 |
2013年 | 14432篇 |
2012年 | 7498篇 |
2011年 | 10326篇 |
2010年 | 8046篇 |
2009年 | 9295篇 |
2008年 | 9744篇 |
2007年 | 9713篇 |
2006年 | 8607篇 |
2005年 | 7957篇 |
2004年 | 7833篇 |
2003年 | 7564篇 |
2002年 | 7374篇 |
2001年 | 7579篇 |
2000年 | 7236篇 |
1999年 | 7565篇 |
1998年 | 17676篇 |
1997年 | 12850篇 |
1996年 | 10116篇 |
1995年 | 7892篇 |
1994年 | 7217篇 |
1993年 | 6916篇 |
1992年 | 5295篇 |
1991年 | 5071篇 |
1990年 | 4948篇 |
1989年 | 4787篇 |
1988年 | 4680篇 |
1987年 | 3891篇 |
1986年 | 4011篇 |
1985年 | 4722篇 |
1984年 | 4279篇 |
1983年 | 4024篇 |
1982年 | 3603篇 |
1981年 | 3764篇 |
1980年 | 3457篇 |
1979年 | 3422篇 |
1978年 | 3227篇 |
1977年 | 3815篇 |
1976年 | 4851篇 |
1975年 | 2781篇 |
1974年 | 2664篇 |
1973年 | 2675篇 |
1972年 | 2215篇 |
1971年 | 1964篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
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
112.
113.
Using boundary element based three dimensional modelling for linear fracture mechanics, we present an analysis of cracking in a homogeneous medium subject to contact load. The proposed iterative solution procedure allows a simultaneous treatment of a reasonable number of partially closed cracks. It is shown that the most probable direction of propagation of a vertical internal crack is strongly dependent on its size compared to the contact radius and its location with respect to the axis of maximum normal load. 相似文献
114.
The dielectric and pyroelectric properties of Ge-doped (0.1 mol %) TlInS2 crystals are studied. The results demonstrate that TlInS2 is a ferroelectric relaxor. The experimental data are used to evaluate, using the Vogel–Fulcher relation, the activation energy (0.045 eV), preexponential factor (f
0 = 2 × 1013 Hz), and the dipole-freezing temperature (T
F = 142 K) and to determine the temperature range of the stable relaxor (nanodomain) state and the temperature of the transition to the ferroelectric (macrodomain) state, accompanied by an anomaly in the temperature-dependent pyroelectric coefficient. 相似文献
115.
This paper describesMicroScope, a framework for developing analysis tools for Lisp programs. MicroScope uses a knowledge-intensive approach for program representation and analysis. The analysis tools share a common object oriented program database, and a common Prolog inference engine. The use of Prolog and a declarative representation for programs permits sharing of information, and provides high bandwidth communication between diverse analysis tools. It also supports program specification and debugging activities in the same framework. Extensions to Prolog to support analysis are described, and two tools, theCritic and theExpector, are presented.This work supported in part by Hewlett-Packard Company, the National Science foundation Under Grant Number MCS81-21750 and the Defense Advanced Research Projects Agency under contract number DAAK11-84-K-0017. 相似文献
116.
A method is developed, based on word-searching, which provides a rapid test for the statistical significance of DNA sequence similarities for use in databank searching. The method makes allowance for the lengths and dinucleotide compositions of the sequences being compared. A way is also described to calculate the power of the test, i.e. the probability of detecting a given similarity as being statistically significant. The effects on the power of the test of the scoring method, word length, sequence length, and sequence composition are examined. A novel scoring method is shown to be superior to the method currently used in most word-searching algorithms. 相似文献
117.
118.
119.
This article presents the development of a ceramic micro heat exchanger. Starting from its geometrical design, results obtained from a simplified simulation of the heat exchanger efficiency will be given. The alumina microcomponents were manufactured by a rapid prototyping process chain. Here, stereolithography was combined with a low‐pressure injection molding process for the rapid and precise manufacturing of ceramic components down to the micrometer range. A micro heat exchanger, joined from sintered components using a glass solder, was applied as a prototype and checked for its performance at a system pressure of 8 bar. 相似文献
120.
E Persson M Ljunggren J la Cour Jansen R Strube L J?nsson 《Water science and technology》2006,53(12):139-147
A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis. 相似文献