全文获取类型
收费全文 | 1455篇 |
免费 | 58篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 10篇 |
综合类 | 5篇 |
化学工业 | 380篇 |
金属工艺 | 86篇 |
机械仪表 | 24篇 |
建筑科学 | 76篇 |
矿业工程 | 6篇 |
能源动力 | 49篇 |
轻工业 | 163篇 |
水利工程 | 13篇 |
无线电 | 78篇 |
一般工业技术 | 257篇 |
冶金工业 | 140篇 |
原子能技术 | 17篇 |
自动化技术 | 214篇 |
出版年
2023年 | 10篇 |
2022年 | 18篇 |
2021年 | 22篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 31篇 |
2015年 | 38篇 |
2014年 | 41篇 |
2013年 | 49篇 |
2012年 | 87篇 |
2011年 | 95篇 |
2010年 | 74篇 |
2009年 | 70篇 |
2008年 | 79篇 |
2007年 | 75篇 |
2006年 | 47篇 |
2005年 | 43篇 |
2004年 | 42篇 |
2003年 | 33篇 |
2002年 | 39篇 |
2001年 | 23篇 |
2000年 | 34篇 |
1999年 | 29篇 |
1998年 | 34篇 |
1997年 | 39篇 |
1996年 | 16篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 23篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 11篇 |
1975年 | 8篇 |
1973年 | 9篇 |
1971年 | 9篇 |
排序方式: 共有1518条查询结果,搜索用时 15 毫秒
91.
92.
Yunho Hwang Reinhard Radermacher William Kopko 《International Journal of Refrigeration》2001,24(3):238
In this paper, the performance of an innovative evaporatively cooled condenser is compared with that of a conventional air-cooled condenser for a split heat pump system. The system was tested in an environmentally controlled test chamber that was able to simulate test conditions as specified by ASHRAE Standard 116. Tests to optimize refrigerant charge and short tube restrictor size were conducted using refrigerant HCFC-22. The wheel rotation speed of the evaporative condenser was also optimized experimentally to maximize the coefficient of performance. Using these optimum parameters, steady state and cyclic performance tests were conducted. The experimental results showed that the evaporative condenser has a higher capacity than the air-cooled condenser by 1.8 to 8.1%, a higher COP by 11.1 to 21.6%, and a higher SEER by 14.5%. 相似文献
93.
The slags formed in the LD vessel during the refining process turn out with different chemical compositions, mineralogical structures and physical properties, in dependence on the charging and processing conditions. Electron probe microanalysis (EPMA) combined with a data processing method for mineralogical analysis was used to characterize the mineralogical phases in LD slags and moreover to determine their volume fractions. By this method some correlations between the phase contents and the chemical composition of LD slags were established. The diagrams gained from this work have proven to be a valuable aid for understanding the interrelationships between the chemical composition, the mineralogical structure and some physical properties of LD slags. 相似文献
94.
Reinhard Haas Gustav ReschChristian Panzer Sebastian BuschMario Ragwitz Anne Held 《Energy》2011,36(4):2186-2193
Currently, a wide range of strategies is implemented in different countries to increase the share of electricity from renewable energy sources (RES-E). A still controversial discussion is whether quantity-driven (like Tradable Green Certificates (TGCs) based on quotas) or price-driven (like feed-in-tariffs (FIT)) instruments lead to preferable solutions for society. The core objective of this paper is to compare the perspectives of quota-based certificate trading systems for an efficient and effective increase of RES-E with FIT. The major results of this analysis are: (i) The success stories of growth in RES-E in EU member states in recent years has been triggered by FIT implemented in a technology-specific manner at modest costs for European citizens; (ii) At present, TGC systems in most countries applied show a low effectiveness with respect to RES-E deployment of less mature technologies such as solar PV (with improving tendencies in e.g. the UK or Italy with respect to certain technologies); (iii) Compared to short term trading in TGC markets the intrinsic stability of FIT systems appears to be a key element for success; (iv) Hence, currently a well-designed (dynamic) FIT system provides a certain deployment of RES-E in the shortest time and at lowest costs for society. 相似文献
95.
Ramón Quintanilla Reinhard Racke 《International Journal of Heat and Mass Transfer》2008,51(1-2):24-29
In this note we consider two cases in the theory of the heat conduction models with three-phase-lag. For each one we propose a suitable Lyapunov function. These functions are relevant tools which allow to study several qualitative properties. We obtain conditions on the material parameters to guarantee the exponential stability of solutions. The spectral analysis complements the results and we show that if the conditions obtained to prove the exponential stability are not satisfied, then we can obtain the instability of solutions for suitable domains. We believe that this kind of results is fundamental to clarify the applicability of the models. 相似文献
96.
97.
Wet grinding in agitated ball mills. To ensure certain product qualities it is necessary to have very fine particles or a narrow particle size distribution. For this process agitated ball mill grinding can be used as well as crystallisation and precipitation. Cost effective grinding of very fine products to a narrow particle size distribution requires that the effects of variation of strain intensity, frequency of impacts, residence time distribution, size of grinding media, viscosity of liquid and concentration of feed material should be known. The most important parameters and their effects on the grinding result are demonstrated, as well as explained by a model, and the consequences for the operating conditions of agitated ball mills are presented. By using small grinding media in agitated ball mills the production rate can be increased, or at the same energy level smaller particles can be obtained by grinding or deagglomeration. At high flow rates and a narrow residence time distribution the feed material becomes more homogeneous. These facts require the development of new or modified types of agitated ball mills. 相似文献
98.
Friedemann Mattern 《Algorithmica》1990,5(1):325-340
The principle of message counting is used to detect termination of distributed computations which consist of processes asynchronously communicating over non-FIFO channels. The solution is symmetric and not based on a predefined communication structure. An efficient variant of the echo algorithm, which dynamically builds a spanning tree, allows a parallel and distributed evaluation of the termination predicate in time proportional to the diameter of the communication graph. Concurrent and repeated initiation of the detection algorithm by different processes is possible at any time without prior synchronization due to a subtle method of collision detection and wave extinction, which can be regarded as a distributed election scheme where the average message complexity increases only logarithmically with the number of concurrent initiators. Control messages have a small length and additional communication links are not required. Only a fixed number of simple variables is needed in every process, global knowledge such as the total number of processes or the structure of the network is not used, making the scheme useful for dynamic systems. Several variations of the basic principle are presented, important issues such as message complexity and fault-tolerance are discussed.This work was supported by the German National Science Foundation (Deutsche Forschungsgemeinschaft) as part of research project SFB124. 相似文献
99.
Achim Neubrand Reinhard Lindner Peter Hoffmann 《Journal of the American Ceramic Society》2000,83(4):860-864
In the present study, the incongruent dissolution of barium from barium titanate (BaTiO3 ) has been studied as a function of dispersion pH and powder volume fraction for two different BaTiO3 powders. In alkaline dispersions, the barium solubility strongly increases as the pH increases, as suggested by thermodynamic considerations. At pH <7, the barium solubility reaches a plateau, the height of which is dependent on the surface area of the powder and the solids loading of the slip. The BaTiO3 surface is completely depleted of barium in this region. 相似文献
100.
Effect of Surface-Active Substances on the Rheological Properties of Silicon Carbide Suspensions in Paraffin 总被引:1,自引:0,他引:1
Reinhard Lenk Alexander Ph. Krivoshchepov 《Journal of the American Ceramic Society》2000,83(2):273-276
In this paper, the possibility of stabilization of SiC suspensions in paraffin (hot-molding slips) was investigated from the colloid science point of view. By considering the surface properties of finely dispersed silicon carbide, surface-active agents (fatty amine and alkylsuccinimide) which are suitable for surface modification by chemical adsorption on SiC were selected. Adsorption of fatty amines and alkylsuccinimide was carried out in model experiments in chloroform. Increasing the length of the carbon–hydrogen chain caused the adsorption to decrease, and the adsorption area of one molecule in the saturated adsorption layer to increase. The stabilizing effect of surface-active agents resulted in improved flow behavior of hot-molding slips. The efficiency of surface-active agents increased with increased adsorption layer thickness. In highly concentrated SiC hot-molding slips, a combination of alkylsuccinimide and fatty amine proved to be very efficient. This synergistic effect of long- and short-chained surface-active agents is discussed in terms of an adsorption layer model. 相似文献