全文获取类型
收费全文 | 18102篇 |
免费 | 2179篇 |
国内免费 | 1547篇 |
专业分类
电工技术 | 2126篇 |
技术理论 | 5篇 |
综合类 | 2299篇 |
化学工业 | 1176篇 |
金属工艺 | 536篇 |
机械仪表 | 953篇 |
建筑科学 | 1426篇 |
矿业工程 | 499篇 |
能源动力 | 337篇 |
轻工业 | 1110篇 |
水利工程 | 587篇 |
石油天然气 | 1400篇 |
武器工业 | 134篇 |
无线电 | 1944篇 |
一般工业技术 | 1188篇 |
冶金工业 | 414篇 |
原子能技术 | 160篇 |
自动化技术 | 5534篇 |
出版年
2024年 | 78篇 |
2023年 | 229篇 |
2022年 | 417篇 |
2021年 | 468篇 |
2020年 | 524篇 |
2019年 | 426篇 |
2018年 | 429篇 |
2017年 | 578篇 |
2016年 | 594篇 |
2015年 | 711篇 |
2014年 | 987篇 |
2013年 | 988篇 |
2012年 | 1186篇 |
2011年 | 1411篇 |
2010年 | 1138篇 |
2009年 | 1170篇 |
2008年 | 1250篇 |
2007年 | 1472篇 |
2006年 | 1321篇 |
2005年 | 1080篇 |
2004年 | 965篇 |
2003年 | 763篇 |
2002年 | 633篇 |
2001年 | 484篇 |
2000年 | 411篇 |
1999年 | 360篇 |
1998年 | 299篇 |
1997年 | 216篇 |
1996年 | 196篇 |
1995年 | 195篇 |
1994年 | 195篇 |
1993年 | 125篇 |
1992年 | 95篇 |
1991年 | 70篇 |
1990年 | 60篇 |
1989年 | 55篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1975年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Different NMR techniques were combined to obtain the structure and velocity information for a systematic investigation of fixed beds with low aspect ratio (tube diameter to particle diamter, dt/dp) in the range 1.4 to 32. The structure of the void space was determined for a variety of packed beds of glass beads or regular and irregular porous pellets by magnetic resonance imaging (MRI). Based on the images the radial distribution of the voids within the bed was obtained. Ordering effects were found even for non‐spherical and polydisperse particles, and a maximum of the fluid density near the tube wall was confirmed for all pellet geometries and sizes. By combining MRI with velocity encoding, velocity profiles and distributions of flow velocity components of a single fluid phase through packed beds have been acquired. The radial velocity distribution follows an oscillatory pattern which largely reflects the ordering of the particles, which can be accessed from the density distribution of the interparticle fluid. Maximum velocities of up to four times the average value were found to occur near the tube wall. This wall effect was observed for all but the smallest particles, where the aspect ratio was dt/dp = 32. Moreover, a visualisation of flow pattern in the presence of packed particles was achieved by using a tagging technique, and the stationary flow field could be identified for an experimental time of several hours. 相似文献
32.
33.
在实践经验的基础上,分析了我国匝间绝缘短路的主要原因,提出在匝间绝缘的设计,制造工艺及耐压试验等工序采取合理措施,以提高匝间绝缘的可靠性。 相似文献
34.
This work discusses the issue of approximation in point set matching. In general, one may have two classes of approximations when tackling a matching problem: (1) an algorithmic approximation which consists in using suboptimal procedures to infer the assignment, and (2), a representational approximation which involves a simplified and suboptimal model for the original data. Matching techniques have typically relied on the first approach by retaining the complete model and using suboptimal techniques to solve it. In this paper, we show how a technique based on using exact inference in simple Graphical Models, an instance of the second class, can significantly outperform instances of techniques from the first class. We experimentally compare this method with well-known Spectral and Relaxation methods, which are exemplars of the first class. We have performed experiments with synthetic and real-world data sets which reveal significant performance improvement in a wide operating range. 相似文献
35.
A two‐phase flow CFD model using the volume of fluid (VOF) method is presented for predicting the hydrodynamics of falling film flow on inclined plates, corresponding to the surface texture of structured packing. Using the proposed CFD model the influence of the solid surface microstructure, liquid properties and gas flow rate on the flow behavior was investigated. From the simulated results it was shown that under the condition of no gas flow the liquid flow patterns are dependent on the microstructure of the plates, and proper microstructuring of the solid surface will improve the formation of a continuous liquid film. It was also found that liquid properties, especially surface tension, play an important role in determining the thin‐film pattern. However, there are very different liquid film patterns under the action of gas flow. Thinner liquid films break easily, but thicker liquid films can remain continuous even at higher gas flow rates, which demonstrates that all factors affecting the liquid film thickness will affect the liquid film patterns under conditions of counter‐current two‐phase flow. 相似文献
36.
Failure analysis of hollow glasses The failure analysis is very important to clarify damages of hollow glasses. Damages of glass bottle through over pressure are very often linked with damages to persons. This is the reason why the causal research is from particular importance. Different surface characteristics of glass fragments as well as the fracture pattern give hints to the direction of the crack, the stress just before breakage and the reason of stress. A reconstruction of the bottle is a further helpful instrument for cause studies. The difference of the various characteristics of the surface will be explained. Further on there will be discussed different reasons and mechanism of fracture. 相似文献
37.
38.
化学模式识别法在钢铁工业中的若干应用 总被引:1,自引:0,他引:1
本文涉及一种崭新的非函数数据处理法及其在工业诊断和优化中的应用。并对其进行要因分析和优化决策的原理作了介绍。结合钢铁工业生产中的实例进行了分析。还探讨了该方法在钢铁工业中应用的意义。 相似文献
39.
Gerardo Gabriel Acosta Miguel Angel Mayosky José Maria Catalfo 《Applied Intelligence》1994,4(1):53-66
This article proposes a scheme for the on-line adjustment of three mode controller settings based on experimental measurements of closed-loop performance. It uses a recently developed heuristic tuning procedure to identify estimated process parameters. This method may give rise to conflicting estimates. Fuzzy Set theory is applied to manage the situation in terms of a fuzzy conjunction to combine the various estimates. PID control was chosen because of its wide use in the industrial environment due to driving simplicity and robustness. The article shows design, development, and computer simulation aspects. 相似文献
40.
我们研制了一种8毫米波变张角、半径突变的多模圆锥馈源。计算出其模比并推导出其辐射方向图公式;给出其在两个主平面——E平面与H平面上的辐射方向图和波束场分布特性的测试结果以及电压驻波比VSWR的测量结果;同时给出频带和旁瓣特性。分析与测试共同表明,在34.5GHz~37GHz频带里,该多模馈源的辐射图在大于24dB范围内获得幅度等化且不出现旁瓣,因此具有一定的应用价值。 相似文献