全文获取类型
收费全文 | 618900篇 |
免费 | 16628篇 |
国内免费 | 6993篇 |
专业分类
电工技术 | 15701篇 |
技术理论 | 7篇 |
综合类 | 10049篇 |
化学工业 | 93637篇 |
金属工艺 | 26005篇 |
机械仪表 | 22533篇 |
建筑科学 | 23511篇 |
矿业工程 | 4861篇 |
能源动力 | 16055篇 |
轻工业 | 55233篇 |
水利工程 | 6654篇 |
石油天然气 | 9574篇 |
武器工业 | 893篇 |
无线电 | 78484篇 |
一般工业技术 | 108469篇 |
冶金工业 | 85154篇 |
原子能技术 | 7231篇 |
自动化技术 | 78470篇 |
出版年
2022年 | 5019篇 |
2021年 | 7587篇 |
2020年 | 5559篇 |
2019年 | 5656篇 |
2018年 | 20718篇 |
2017年 | 20365篇 |
2016年 | 16855篇 |
2015年 | 8795篇 |
2014年 | 11863篇 |
2013年 | 26954篇 |
2012年 | 20825篇 |
2011年 | 31848篇 |
2010年 | 26301篇 |
2009年 | 25085篇 |
2008年 | 27017篇 |
2007年 | 28035篇 |
2006年 | 19752篇 |
2005年 | 19031篇 |
2004年 | 16679篇 |
2003年 | 15980篇 |
2002年 | 14844篇 |
2001年 | 14409篇 |
2000年 | 13710篇 |
1999年 | 14326篇 |
1998年 | 27568篇 |
1997年 | 20520篇 |
1996年 | 16556篇 |
1995年 | 13125篇 |
1994年 | 11520篇 |
1993年 | 10638篇 |
1992年 | 8123篇 |
1991年 | 7633篇 |
1990年 | 6980篇 |
1989年 | 6650篇 |
1988年 | 6303篇 |
1987年 | 5184篇 |
1986年 | 5045篇 |
1985年 | 6110篇 |
1984年 | 5692篇 |
1983年 | 4900篇 |
1982年 | 4574篇 |
1981年 | 4512篇 |
1980年 | 4254篇 |
1979年 | 4095篇 |
1978年 | 3780篇 |
1977年 | 4555篇 |
1976年 | 6114篇 |
1975年 | 3125篇 |
1974年 | 3016篇 |
1973年 | 2897篇 |
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
121.
A method for assessing health care technology that models the demand on the clinician's attention exerted by patients' data (diagnostic and therapeutic) can provide a means for simultaneously reducing the cost and improving the quality of health care. The attentional demand exerted by patients' data can be measured by the amount of uncertainty in the data. Uncertainty can be expressed mathematically by the concept of entropy in information theory. 相似文献
122.
Using a continuous, in-line, nondestructive technique based on the maximum bubble pressure method, the surface tension of
the wash water in a mechanical dishwashing machine has been monitored. This technique has enabled surface tension to be used
as a controlled variable, providing feedback to regulate the amount of surfactant added. Assuming the mechanical force of
the water spray is adequate to remove bound soil from the dish surface, the food soil may be titrated against surfactant,
providing an indirect indication as to when the dishes are clean. This technique also could be applied to a recirculated wash
solution for in-place cleaning. 相似文献
123.
124.
125.
Jon T. Carter Paul E. Krajewski Ravi Verma 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(11):77-81
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive
applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect
of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General
Motors Corporation is reviewed. 相似文献
126.
Ploennigs J. Neugebauer M. Kabitzsch K. 《Industrial Informatics, IEEE Transactions on》2008,4(2):71-79
Network performance engineering can verify the design and dimensioning of large-scale control networks like CSMA-based building automation networks. It combines performance analysis with diagnosis methods to evaluate the network utilization and to detect design errors before installation and can therewith save the expenses of overdimensioning and redesign. This paper will develop a diagnosis model based on fault trees that is able to use the huge amount of performance analysis results to identify design errors and analyze their coherences. This enables not only a fast tracing back of fault causes and the derivation of solutions; it can also visualize the fault coherence to the user and help him to understand his design. Additional consulting tools implement best practice strategies, to support the user in parameterization. 相似文献
127.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
128.
J.P. MacDonald B. GualtieriN. Runga E. TelizC.F. Zinola 《International Journal of Hydrogen Energy》2008
The presence of a second metal on platinum surfaces affects the performance of methanol oxidation. However, most of the electrocatalytic reactions are studied by using electrochemically deposited platinum alloys, but in the case of spontaneous deposition the situation is not so clear since the surface distribution, stability and morphology are usually not well documented. The formation of surface decorated samples on mono- and poly-crystalline platinum is followed by electrochemical and spectroscopic techniques and analysis of their performance towards methanol adsorption and oxidation compared with that on pure platinum. Pt/Sn and Pt/Ru are of special interest because of their well-known performance in methanol fuel cells. Methanol oxidation on Pt(111)/Ru, Pt(111)/Sn and Pt(111) shows that ruthenium is the only one able to promote the reaction since the simultaneous dissolution of tin occurs and competes with the process of interest. The in situ infrared spectroscopy is used to compare methanol oxidation on Pt(111)/Ru and Pt(111) in acid media using p-polarized light. The formation of bridge bound carbon monoxide is inhibited in the presence of ruthenium ad-species, whereas on Pt(111) the three adsorption configurations are observed. Linear sweep polarization curves and Tafel slopes (calculated from steady state potentiostatic plots) for methanol oxidation are compared on polycrystalline surfaces modified by tin or ruthenium at different coverages. There is almost no change in the Tafel slopes due to the presence of the foreign metal except for Pt/Ru, where a 0.09 V decade−1 slope was calculated below 0.55 V due to hydroxyl adsorbates on ruthenium islands. The anodic stripping of methanol residues on the three surfaces indicates a lower amount of carbon monoxide-type adsorbates on Pt/Ru, and the simultaneous tin dissolution process leading to residues oxidation on Pt/Sn electrodes. 相似文献
129.
130.
The development of deregulation and demand for high-quality electrical energy has lead to a new requirement in different fields of power systems. In the protection field, this means that high sensitivity and fast operation during the fault are required while maltripping of relay protection is not acceptable. One case that may lead to a maltrip of the high-sensitive overcurrent relay is the starting current of the induction motor or inrush current of the transformer. This transient current has the potential to affect the correct operation of protection relays close to the component being switched. In the case of switching events, such transients must not lead to overcurrent relay operation; therefore, a reliable and secure relay response becomes a critical matter. Meanwhile, proper techniques must be used to prevent maltripping of such relays, due to transient currents in the network. In this paper, the optimal Bayes classifier is utilized to develop a method for discriminating the fault from nonfault events. The proposed method has been designed based on extracting the modal parameters of the current waveform using the Prony method. By feeding the fundamental frequency damping and ratio of the 2nd harmonic amplitude over the fundamental harmonic amplitude to the classifier, the fault case is discriminated from the switching case. The suitable performance of this algorithm is demonstrated by simulation of different faults and switching conditions on a power system using PSCAD/EMTDC software. 相似文献