全文获取类型
收费全文 | 641913篇 |
免费 | 8574篇 |
国内免费 | 1872篇 |
专业分类
电工技术 | 11326篇 |
综合类 | 2835篇 |
化学工业 | 93137篇 |
金属工艺 | 28380篇 |
机械仪表 | 22109篇 |
建筑科学 | 15364篇 |
矿业工程 | 3319篇 |
能源动力 | 15892篇 |
轻工业 | 50446篇 |
水利工程 | 6954篇 |
石油天然气 | 10592篇 |
武器工业 | 37篇 |
无线电 | 72059篇 |
一般工业技术 | 126924篇 |
冶金工业 | 109256篇 |
原子能技术 | 11399篇 |
自动化技术 | 72330篇 |
出版年
2022年 | 3167篇 |
2021年 | 4904篇 |
2020年 | 3486篇 |
2019年 | 4566篇 |
2018年 | 25168篇 |
2017年 | 24523篇 |
2016年 | 19235篇 |
2015年 | 6395篇 |
2014年 | 9480篇 |
2013年 | 24252篇 |
2012年 | 18785篇 |
2011年 | 33273篇 |
2010年 | 27784篇 |
2009年 | 26999篇 |
2008年 | 27913篇 |
2007年 | 29818篇 |
2006年 | 15654篇 |
2005年 | 17691篇 |
2004年 | 15846篇 |
2003年 | 15471篇 |
2002年 | 13540篇 |
2001年 | 12956篇 |
2000年 | 12109篇 |
1999年 | 12653篇 |
1998年 | 32859篇 |
1997年 | 22922篇 |
1996年 | 17492篇 |
1995年 | 13051篇 |
1994年 | 11315篇 |
1993年 | 11002篇 |
1992年 | 7929篇 |
1991年 | 7460篇 |
1990年 | 7262篇 |
1989年 | 7013篇 |
1988年 | 6476篇 |
1987年 | 5766篇 |
1986年 | 5656篇 |
1985年 | 6265篇 |
1984年 | 5901篇 |
1983年 | 5170篇 |
1982年 | 4900篇 |
1981年 | 4966篇 |
1980年 | 4705篇 |
1979年 | 4609篇 |
1978年 | 4409篇 |
1977年 | 5334篇 |
1976年 | 6971篇 |
1975年 | 3796篇 |
1974年 | 3551篇 |
1973年 | 3665篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A. I. Nikolaev F. D. Larichkin O. A. Nikolaeva 《Theoretical Foundations of Chemical Engineering》2008,42(5):675-679
The main rules and principles which govern the choice of new variants for chemical technology of combined processing of titanium-rare-metal raw materials are considered. The existing variants of the technology are characterized from the viewpoint of their technological, economical, and ecological efficiency and social importance for a given region. A realistic choice of a technology from a large number of available variants should take into account the entire combination of their advantages and disadvantages The implementation of a rational technological scheme will result in the creation of economically profitable and efficient domestic production satisfying the demands of Russian industry in rare-metal and titanium materials. Directions are noted in which it is expedient to continue studies on designing a rational technology of loparite concentrate or some other concentrate. 相似文献
992.
P. S. Gordienko V. A. Kolzunov L. G. Zorina T. A. Kaidalova S. B. Yarusova 《Theoretical Foundations of Chemical Engineering》2008,42(5):680-683
The possibility of processing fluorine-containing wastes of fluorite ore, which include fluorite, calcite, quartz, and anorthite, has been investigated. A manufacturing flow chart of the complex processing of the ore waste materials with the production of sodium fluoride, alumina, soda ash, and raw materials suitable for the production of Portland cement and wollastonite is suggested. 相似文献
993.
The new emerging area of Enterprise Wide Optimization (EWO) has focused the attention in effectively solving the combined production/distribution scheduling problem. The importance of logistic activities performed in multi-site environments comes from the relative magnitude of the associated transportation costs and the good chance of getting large savings on such expenses. This paper first develops an exact MILP mathematical formulation for the multiple vehicle time-window-constrained pickup and delivery (MVPDPTW) problem. The approach is able to account for many-to-many transportation requests, pure pickup and delivery tasks, heterogeneous vehicles and multiple depots. Optimal solutions for a variety of benchmark problems with cluster/random distributions of pickup and delivery locations and limited sizes in terms of customer requests and vehicles have been discovered. However, the computational cost exponentially grows with the number of requests. For large-scale m-PDPTW problems, a local search improvement algorithm steadily providing a better solution through two evolutionary steps is also presented. A neighborhood structure around the starting solution is generated by first allowing multiple request exchanges among nearby trips and then permitting the reordering of nodes on every individual route. If a better set of routes is found, both steps are repeated until no improved solution is discovered. Compact MILP mathematical formulations for both sub-problems have been developed and solved through an efficient branch-and-bound algorithm. A significant number of large-scale m-PDPTW benchmark problems, some of them including up to 100 transportation requests, were successfully solved in reasonable CPU times. 相似文献
994.
V. N. Babak T. B. Babak L. P. Kholpanov 《Theoretical Foundations of Chemical Engineering》2008,42(6):852-867
Mass transfer with solvent evaporation in the vapor-liquid two-phase film evaporators used for the removal of undesirable
impurities from liquid solutions at low pressure is studied. The average concentrations of solution components in the falling
liquid film are determined. The most efficient operating conditions for impurity removal, in which the resistance to mass
transfer is concentrated in the liquid phase, are found.
Original Russian Text ? V.N. Babak, T.B. Babak, L.P. Kholpanov, 2008, published in Teoreticheskie Osnovy Khimicheskoi Tekhnologii,
2008, Vol. 42, No. 6, pp. 654–670. 相似文献
995.
Some sulfides of gold and silver: Composition,mineral mineral assemblage,and conditions of formation
Characteristic mineral assemblage and special features of the composition of Au and Ag sulfides of gold-silver deposits have been established. The forms of the occurrence of Au and Ag in the minerals of the early and last stages have been analyzed. The conditions for the formation of uytenbogaardtite and petrovskaite in supergene and low-temperature hydrothermal processes have been considered. A thermodynamic model explaining their genesis in the oxidation zones is presented. 相似文献
996.
V. M. Vorotyntsev G. M. Mochalov M. A. Kolotilova S. S. Suvorov A. V. Koroleva A. Yu. Sharov 《Theoretical Foundations of Chemical Engineering》2008,42(2):197-202
The results of theoretical and experimental studies for the kinetics of separating dichlorosilane from a mixture of volatile chlorosilanes and ultrapurifying the dichlorosilane concentrate by batch distillation are reported. A mathematical model of the process is proposed. It is shown that the model and computational algorithm adequately describe both processes. The obtained experimental and theoretical data made it possible to design a concentration and ultrapurification process with a maximal productivity at a specified product purity. 相似文献
997.
The kinetics of the reaction of olefin synthesis from dimethyl ether and methanol is studied. A kinetic model of the nine-route reaction under study is constructed. The constants of the model are estimated using experimental data. The adequacy of the model to the results of experiments is shown 相似文献
998.
Y.M. Wong W.P. Kang J.L. Davidson J.H. Huang D.V. Kerns 《Diamond and Related Materials》2008,17(4-5):552-555
A novel integrated vacuum field emission (VFE) differential amplifier (diff-amp) utilizing carbon nanotube (CNT) emitters has been developed. A dual-mask microfabrication process was employed to achieve a VFE diff-amp by integrating identical CNT VFE transistors with built-in split gates and integrated anodes. The identical pair of triode amplifiers was well-matched in their device characteristics. The measured ac small-signal characteristics of the diff-amp showed a common-mode-rejection ratio (CMRR) of ~ 320 (~ 50 dB). The proposed analytical model of the CMRR was verified to be in good agreement with the experimental data. The successful implementation of the CNT diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics. 相似文献
999.
This paper presents data relating to the performance of sprinklers and detectors in real office fire situations. For sprinklers, these data are additional to that associated with the standardized testing used to determine the design delivery density and pressure requirements for various occupancy situations, and provide a useful insight into the effect of sprinklers on developing fires with various office situations. The data given in this paper include the times for activation of various types of sprinkler heads (normal and fast response), the efficacy of the systems as far as extinguishment is concerned, estimates of the maximum size of the fires prior to commencement of extinguishment and associated air temperatures at various locations within the office enclosures. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
1000.
M. L. Malinkovich 《Glass and Ceramics》2008,65(3-4):136-138
The capabilities of x-ray spectral instruments for fast analysis of raw materials and glass and ceramics were demonstrated. The range of the content of determinable elements in a sample ranges from 1 ppm to 100%. The measurement time is 10–15 sec. 相似文献