全文获取类型
收费全文 | 115792篇 |
免费 | 1745篇 |
国内免费 | 867篇 |
专业分类
电工技术 | 1951篇 |
综合类 | 676篇 |
化学工业 | 15585篇 |
金属工艺 | 4007篇 |
机械仪表 | 3486篇 |
建筑科学 | 2464篇 |
矿业工程 | 890篇 |
能源动力 | 2251篇 |
轻工业 | 8361篇 |
水利工程 | 1439篇 |
石油天然气 | 2351篇 |
武器工业 | 45篇 |
无线电 | 8960篇 |
一般工业技术 | 19683篇 |
冶金工业 | 32731篇 |
原子能技术 | 2802篇 |
自动化技术 | 10722篇 |
出版年
2022年 | 687篇 |
2021年 | 1005篇 |
2020年 | 707篇 |
2019年 | 820篇 |
2018年 | 1992篇 |
2017年 | 2222篇 |
2016年 | 2796篇 |
2015年 | 1719篇 |
2014年 | 1966篇 |
2013年 | 3957篇 |
2012年 | 4418篇 |
2011年 | 5201篇 |
2010年 | 3010篇 |
2009年 | 3366篇 |
2008年 | 3207篇 |
2007年 | 3158篇 |
2006年 | 2736篇 |
2005年 | 5210篇 |
2004年 | 4362篇 |
2003年 | 3797篇 |
2002年 | 2536篇 |
2001年 | 2393篇 |
2000年 | 1937篇 |
1999年 | 2138篇 |
1998年 | 9439篇 |
1997年 | 6197篇 |
1996年 | 4297篇 |
1995年 | 2881篇 |
1994年 | 2313篇 |
1993年 | 2388篇 |
1992年 | 1228篇 |
1991年 | 1335篇 |
1990年 | 1349篇 |
1989年 | 1311篇 |
1988年 | 1218篇 |
1987年 | 1083篇 |
1986年 | 1068篇 |
1985年 | 1094篇 |
1984年 | 845篇 |
1983年 | 842篇 |
1982年 | 803篇 |
1981年 | 862篇 |
1980年 | 845篇 |
1979年 | 705篇 |
1978年 | 715篇 |
1977年 | 1369篇 |
1976年 | 2210篇 |
1975年 | 676篇 |
1974年 | 589篇 |
1973年 | 590篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Sorichetti P.A. Matteo C.L. Lambri O.A. Manguzzi G.C. Salvatierra L.M. Herrero O. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(5):1170-1182
This work presents a study of the structural changes in aged EPDM (ethylene-propylene-diene monomer) from outdoor high voltage transmission lines. Samples were taken from failed and non-failed insulators after up to ten years in service on a 33 kV line. Infrared absorption, hydrophobicity index, dynamical mechanical analysis (DMA) and dielectric relaxation (DR) were employed as experimental techniques. The same experimental techniques were also applied to new samples of EPDM that were subjected to high electric fields (up to 14 kV/mm) for several hours. Results from DMA and DR techniques are in good agreement and, together with previous results from neutron irradiation techniques, suggest that the experimental data obtained from outdoor-aged and laboratory tested samples may be explained by a decrease in the degree of crystallinity due to the interaction between electrical and mechanical effects in the dielectric. The proposed model is based on the disentanglement of the crystallites by forces originated in the interaction of the electric field with the polar groups located in the amorphous phase of the polymer matrix. An alternative explanation, based on a relaxation process appearing at the interfaces between the filler (ATH) and the polymer matrix conflicts with several experimental results presented in this work. 相似文献
992.
A three dimensional model of the BTA deep-hole machining system is presented by modelling each of the components separately and later combining to represent the total system. A model for the interaction between the workpiece and the cutting tool is also included. Such a model can determine the response of any component of the machine tool as well as the individual influence on the system performance. Based on this, physical models representing the three working methods in the BTA process can be studied, from which stochastic differential equations are derived to represent the resultant force system on the machine tool
A physical model for the stationary workpiece and rotating cutting tool working method is developed. The assumed modes method along with the Lagrange' equation is used to obtain the stochastic differential equation to represent the influence of axial force and torque, in order to obtain the response of the system under the action of the axial force and torque to predict the stability behaviour. 相似文献
A physical model for the stationary workpiece and rotating cutting tool working method is developed. The assumed modes method along with the Lagrange' equation is used to obtain the stochastic differential equation to represent the influence of axial force and torque, in order to obtain the response of the system under the action of the axial force and torque to predict the stability behaviour. 相似文献
993.
During summer 1982, responses of lactating Holstein and Guernsey cows were measured by milk temperature recorded by a Digital Dataloger with thermocouples attached to Boumatic flow meters. Maximum air temperature and temperature-humidity index averaged 30.8 degrees C and 75.6 for July. Breed did not affect milk temperature, but within-breed milk temperature increased with production. In a second study, benefits of spray cooling were evaluated with 24 Holsteins in midlactation assigned randomly to two groups of 12 and maintained under loose-housing conditions. Spray nozzles were installed in the walkways and under the manger shade for the spray treatment group. Maximum temperature and temperature-humidity index during the spray study were 27 degrees C and 73.9. Rectal temperature taken following milking averaged less for treatment than control (38.8 versus 39.1 degrees C). Milk temperature was similar (37.8 versus 38.1 degrees C). Daily milk yield was .70 kg higher than controls. Milk temperature may provide reliable indication of climate stress similar to rectal temperature, and spray cooling improves cow comfort and lessens summer decline of milk production. 相似文献
994.
995.
996.
A. F. Shevchenko A. V. Komarov O. I. Novokreschenov V. V. Mizevich 《Russian Electrical Engineering》2007,78(9):478-480
Results of the development of a direct-drive electromechanical steering booster (ESB) for a passenger car are considered. Technical characteristics of the ESB and the results of the calculations of characteristics and the simulation of the magnetic system are presented. Availability of application of magnetoelectric motors with fractional tooth windings in the ESB is shown. 相似文献
997.
O. Ya. Shmelev 《Measurement Techniques》1994,37(2):205-208
A measurement and computing system designed for acoustical investigations of liquid crystals, magnetic fluids, etc., in the frequency range 0.15–1.2 MHz is described.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 51–53, February, 1994. 相似文献
998.
Process Variables, Gelatinized Starch and Moisture Effects on Physical Properties of Mungbean Noodles 总被引:2,自引:0,他引:2
The effects of amounts of gelatinized starch and moisture in the final slurry or dough, cooking time, holding time, and holding temperature on physical properties of mungbean noodles were studied. Cooking loss, cutting stress, work to cut, and transparency of noodles were measured. Moisture content of the final slurry or dough, cooking time, and holding temperature were the most important factors that affected physical properties of mungbean noodles. Processing should be done at moisture contents not exceeding 55%, cooking times not longer than 40 set, and holding temperatures not lower than 3° using 5% of total starch as gelatinized starch and holding time of 36 hr. 相似文献
999.
E.O. Adamov I.I. Grozdov S.P. Kuznetsov A.A. Petrov M.I. Rozhdestvensky Yu.M. Cherkashov 《Nuclear Engineering and Design》1994,147(1)
Following the search for new design solutions to develop within the framework of channel trends the reactor with enhanced safety the Research and Development Institute of Power Engineering has developed the design of the multiloop boiling water reactor (MKER). The MKER enhanced safety is attained when involving the inherent safety features, passive safety systems as well as the accident consequences confinement devices. The design realizes several advantages which are typical of the channel-type reactors, namely: the design desintegration simplifying the manufacture, control, equipment delivery and decreasing, versus the pressure vessel reactors, the accident effect if it proceeds in an explosive manner; small operating reactivity margin and fuel burnup increased due to continuous refuelling; fuel cycle flexibility allowing comparatively easily to adopt the reactor to the conjuncture of the country fuel balance; multiloop circuit of the main coolant which reduces the degree and effect of the accidents connected with the equipment and pipings rupture; monitoring of the channels and fuel assemblies leak-tightness. 相似文献
1000.
In two-fluid modelling, accurate prediction of the interfacial transport of mass, momentum and energy is required. Experiments were carried out to obtain a database for the development of interfacial transport models, or correlations, for subcooled water-steam flow in vertical conduits. The experimental data of interest included the interfacial area concentration, interfacial condensation heat transfer and bubble relative velocity. This paper focuses on the interfacial area concentration. The interfacial area concentration was obtained by measuring the distributions of bubble volume and surface area as well as the area-averaged void fraction at various axial locations in subcooled water-steam condensing vertical upward flow under low flow rate and low pressure conditions. The bubble size and surface area were determined using high-speed photography and digital image processing techniques. The area-averaged void fraction was measured by a single-beam gamma densitometer. The results were compared with existing correlations, which were developed on the basis of data obtained for air-water adiabatic flows. Poor agreement between the present data and the existing correlations was obtained. Accordingly, new correlations suitable for subcooled liquid-vapour bubbly flow are proposed. 相似文献