全文获取类型
收费全文 | 602173篇 |
免费 | 8052篇 |
国内免费 | 1948篇 |
专业分类
电工技术 | 11318篇 |
综合类 | 657篇 |
化学工业 | 89694篇 |
金属工艺 | 21795篇 |
机械仪表 | 17982篇 |
建筑科学 | 15923篇 |
矿业工程 | 1810篇 |
能源动力 | 15699篇 |
轻工业 | 57931篇 |
水利工程 | 5208篇 |
石油天然气 | 5497篇 |
武器工业 | 81篇 |
无线电 | 78117篇 |
一般工业技术 | 112280篇 |
冶金工业 | 112432篇 |
原子能技术 | 9684篇 |
自动化技术 | 56065篇 |
出版年
2021年 | 4309篇 |
2019年 | 4087篇 |
2018年 | 6611篇 |
2017年 | 6758篇 |
2016年 | 7188篇 |
2015年 | 5235篇 |
2014年 | 8762篇 |
2013年 | 27620篇 |
2012年 | 14957篇 |
2011年 | 20996篇 |
2010年 | 16345篇 |
2009年 | 18618篇 |
2008年 | 19954篇 |
2007年 | 20257篇 |
2006年 | 18243篇 |
2005年 | 16775篇 |
2004年 | 16277篇 |
2003年 | 15815篇 |
2002年 | 15345篇 |
2001年 | 15318篇 |
2000年 | 14395篇 |
1999年 | 15075篇 |
1998年 | 34589篇 |
1997年 | 25103篇 |
1996年 | 19824篇 |
1995年 | 15486篇 |
1994年 | 13780篇 |
1993年 | 13313篇 |
1992年 | 10239篇 |
1991年 | 9696篇 |
1990年 | 9149篇 |
1989年 | 8761篇 |
1988年 | 8382篇 |
1987年 | 7253篇 |
1986年 | 7106篇 |
1985年 | 8575篇 |
1984年 | 8004篇 |
1983年 | 7100篇 |
1982年 | 6602篇 |
1981年 | 6663篇 |
1980年 | 6250篇 |
1979年 | 6048篇 |
1978年 | 5674篇 |
1977年 | 6832篇 |
1976年 | 8913篇 |
1975年 | 4929篇 |
1974年 | 4804篇 |
1973年 | 4730篇 |
1972年 | 3772篇 |
1971年 | 3405篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
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
152.
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
153.
154.
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
155.
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
156.
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
157.
This paper deals with accurate recipe implementation for abnormal condition management in a batch process using a case‐based reasoning (CBR) approach. A set of new problems can be solved by reusing proven process solutions. The proposed system integrates quantitative and qualitative parameters for adaptation of cases. A novel methodology to generate accurate recipes and to adapt to the processes is introduced during normal and abnormal conditions. In particular, the differences between current conditions and the references (recipes) should be managed to prevent any hazardous conditions arising. The processes are evaluated using their similarity to the past cases. This intelligent approach distinguishes plausible cases, generates accurate recipes, and adapts to new situations. The aim is to use the offline historical process data and safety related information in order to propose changes and adjustments in the processes. 相似文献
158.
159.
The cooling and solidification of melted drops during their movement in an immiscible cooling medium is widely employed for granulation in the chemical industry, and a study of these processes to provides a basis for the design of the granulation tower height and the temperature of the cooling medium is reported. A physical model of the cooling and solidification of the drop is established and the numerical calculation is performed. The influences of the key factors in the solidification, i.e., Bi number, drop diameter, temperature of the cooling medium, etc. are presented. The cooling and solidification during wax granulation in a water‐cooling tower and during urea granulation in an air‐cooling tower (spraying tower) are described in detail. Characteristics of the solidification and temperature distribution within the particle at different times are shown. The model and calculations can be used for structure design of the granulation tower and optimization of the operation parameters. 相似文献
160.
As a result of shrinking fossil fuels, biomass as a regenerative energy source gains importance. To realize biomass projects it is essential to investigate in convenient thermal procedures. On this evidence an analysis and evaluation of diverse gasification technologies with different boundary conditions and diverse biomasses are indispensable. Form and kind of the biomass as well as the type of the gasification plant cause different compositions of the product gas. The gasifiers show advantages and disadvantages concerning the biomass and the produced gas quality, depending on reactor type, kind of heat supply, gasification medium, and the pressure ratio in the reactor. As the ideal gasifier for different biomass is presently not available, it will be shown, which biomass is suitable for fixed bed or fluidized bed gasifiers. 相似文献