全文获取类型
收费全文 | 18650篇 |
免费 | 2019篇 |
国内免费 | 1465篇 |
专业分类
电工技术 | 680篇 |
技术理论 | 5篇 |
综合类 | 2132篇 |
化学工业 | 894篇 |
金属工艺 | 484篇 |
机械仪表 | 770篇 |
建筑科学 | 4598篇 |
矿业工程 | 416篇 |
能源动力 | 310篇 |
轻工业 | 954篇 |
水利工程 | 558篇 |
石油天然气 | 1364篇 |
武器工业 | 116篇 |
无线电 | 1859篇 |
一般工业技术 | 1039篇 |
冶金工业 | 315篇 |
原子能技术 | 155篇 |
自动化技术 | 5485篇 |
出版年
2024年 | 72篇 |
2023年 | 215篇 |
2022年 | 402篇 |
2021年 | 430篇 |
2020年 | 490篇 |
2019年 | 417篇 |
2018年 | 419篇 |
2017年 | 477篇 |
2016年 | 659篇 |
2015年 | 700篇 |
2014年 | 960篇 |
2013年 | 1065篇 |
2012年 | 1211篇 |
2011年 | 1363篇 |
2010年 | 1096篇 |
2009年 | 1179篇 |
2008年 | 1287篇 |
2007年 | 1633篇 |
2006年 | 1509篇 |
2005年 | 1205篇 |
2004年 | 1119篇 |
2003年 | 906篇 |
2002年 | 596篇 |
2001年 | 451篇 |
2000年 | 375篇 |
1999年 | 312篇 |
1998年 | 261篇 |
1997年 | 187篇 |
1996年 | 179篇 |
1995年 | 188篇 |
1994年 | 165篇 |
1993年 | 110篇 |
1992年 | 90篇 |
1991年 | 61篇 |
1990年 | 55篇 |
1989年 | 53篇 |
1988年 | 24篇 |
1987年 | 21篇 |
1986年 | 17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
81.
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
82.
观察分析了冷却速度对低合金超高强度钢(40CrMnSiMoVA)精细组织的影响。结果表明,在冷却、低温等温(或回火)过程中,钢显微组织中的马氏体或贝氏体存在时效阶段。其组织特征为呢纹花样。α和ε间的取向不满足Jack关系,它属一种新的取向关系。过渡型碳化物可直接从呢纹花样区析出。 相似文献
83.
84.
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
85.
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
87.
空间的塑造--厦门海湾公园设计 总被引:1,自引:1,他引:0
海湾公园利用植物、地形、大海与湖泊的周边环境等景观要素,运用隐喻、对比的手法,创造丰富、神秘、变化的空间,注重空间灵活的使用功能及其良好的人性化. 相似文献
88.
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
89.
生活污水用于园林绿化的实验 总被引:1,自引:0,他引:1
通过对11种在天津石化公司有代表性的绿化植物10年来应用生活污水的跟踪调查及进行的相关实验证明,直接应用生活污水浇灌绿化植物,对绿化植物生长及对环境造成的负面影响不大.根据实验结果认为,生活污水可以有条件地用于园林绿化,并应注意密切跟踪调查. 相似文献
90.