全文获取类型
收费全文 | 831442篇 |
免费 | 9498篇 |
国内免费 | 2090篇 |
专业分类
电工技术 | 15380篇 |
综合类 | 705篇 |
化学工业 | 127668篇 |
金属工艺 | 33280篇 |
机械仪表 | 26502篇 |
建筑科学 | 18553篇 |
矿业工程 | 5417篇 |
能源动力 | 22462篇 |
轻工业 | 64539篇 |
水利工程 | 9563篇 |
石油天然气 | 18189篇 |
武器工业 | 46篇 |
无线电 | 93111篇 |
一般工业技术 | 168033篇 |
冶金工业 | 150014篇 |
原子能技术 | 19134篇 |
自动化技术 | 70434篇 |
出版年
2021年 | 7674篇 |
2020年 | 5780篇 |
2019年 | 7372篇 |
2018年 | 12566篇 |
2017年 | 12689篇 |
2016年 | 13375篇 |
2015年 | 8575篇 |
2014年 | 14319篇 |
2013年 | 39190篇 |
2012年 | 22540篇 |
2011年 | 30729篇 |
2010年 | 24540篇 |
2009年 | 27556篇 |
2008年 | 28059篇 |
2007年 | 27668篇 |
2006年 | 24249篇 |
2005年 | 21921篇 |
2004年 | 20922篇 |
2003年 | 20689篇 |
2002年 | 19672篇 |
2001年 | 19283篇 |
2000年 | 18302篇 |
1999年 | 18576篇 |
1998年 | 45425篇 |
1997年 | 32211篇 |
1996年 | 25004篇 |
1995年 | 18903篇 |
1994年 | 16912篇 |
1993年 | 16711篇 |
1992年 | 12496篇 |
1991年 | 11897篇 |
1990年 | 11758篇 |
1989年 | 11345篇 |
1988年 | 10779篇 |
1987年 | 9733篇 |
1986年 | 9371篇 |
1985年 | 10698篇 |
1984年 | 9732篇 |
1983年 | 9103篇 |
1982年 | 8278篇 |
1981年 | 8449篇 |
1980年 | 7889篇 |
1979年 | 7957篇 |
1978年 | 7797篇 |
1977年 | 8802篇 |
1976年 | 11179篇 |
1975年 | 6901篇 |
1974年 | 6622篇 |
1973年 | 6727篇 |
1972年 | 5684篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Yu. F. Patrakov E. S. Pavlusha N. I. Fedorova Yu. A. Strizhakova 《Solid Fuel Chemistry》2008,42(1):10-13
The results of the thermal solution of oil shale in benzene in a flow unit under supercritical conditions are reported. It was found that the conversion of shale organic matter into liquid products increased by a factor of 2.5 with an increase in the solvent pressure from 5 to 15 MPa. 相似文献
992.
A. V. Popov 《Glass and Ceramics》2008,65(3-4):77-78
It was shown that use of AS32–AS50 diamond powders (instead of AS6–AS15 powders) combined with a new metal bond with hardness of HB 75–85 (in comparison to M2-01 binder) allows prolonging the lifetime of wheels by 1.5–2 times in grinding articles made of commercial and art glass, reducing the specific diamond consumption, and increasing the cutability of the instrument. 相似文献
993.
D. Ballutaud F. Jomard T. Kociniewski E. Rzepka H. Girard S. Saada 《Diamond and Related Materials》2008,17(4-5):451-456
Hot filament and microwave plasma CVD micro- nanocrystalline diamond films are analysed by visible and ultra-violet excitation source Raman spectroscopy. The sample grain size varies from 20 nm to 2 μm. The hydrogen concentration in samples is measured by SIMS and compared to the grain size, and to the ratio of sp2 carbon bonds determined by Raman spectroscopy from the 1332 cm− 1 diamond peak and the sp2 1550 cm− 1 G band. Hydrogen concentration appears to be proportional to the sp2 bonds ratio. The 3000 cm− 1 CHx stretching mode band intensity observed on the Raman spectra is decreasing with the G band intensity. Thermal annealing modifies the sp2 phase structure and concentration, as hydrogen outdiffuses. 相似文献
994.
A model of contact thermolysis was constructed based on a combined set of equations for heat transfer from a magmatic intrusion to a coal bed and the kinetics of thermal coal conversion. This model was illustrated by the generation of petroleum hydrocarbons deep in the earth by the thermolysis of the sapropelic matter of boghead. 相似文献
995.
M. Guerioune Y. Amiour W. Bounour O. Guellati A. Benaldjia A. Amara N. E. Chakri M. Ali-Rachedi D. Vrel 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(1):41-48
Aiming at preparation of shape memory alloys (SMAs), we explored the SHS of Cu1 − x
Zn1 − y
Al1 − z
alloys (0.29 < x < 0.30, 0.74 < y < 0.75, and 0.83 < z < 0.96). The most pronounced shape memory effect was exhibited by the alloys of the following compositions (wt %): (1) Cu(70.6)Zn(25.4)Al(4.0),
(2) Cu(70.1)Zn(25.9)Al(4.0), and (3) Cu(69.9)Zn(26.1)Al(4.0). The effect of process parameters on the synthesis of CuZnAl
alloys was studied by XRD, optical microscopy, and scanning electron microscopy (SEM). The grain size of CuZnAl was found
to depend on the relative amount of the primary CuZn and AlZn phases. Changes in the transformation temperature and heat of
transformation are discussed in terms of ignition intensity and compaction. Mechanism of the process depends on the level
of the temperature attained relative to the melting point of components. At the melting point of AlZn, the process is controlled
by the solid-state diffusion of AlZn into a product layer. The ignition temperature for this system depends on the temperature
of the austenite-martensite transformation in CuZnAl alloys. The composition and structure of the products was found to markedly
depend on process parameters. The SHS technique has been successfully used to prepare a variety of SMAs.
相似文献
996.
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
997.
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
998.
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
999.
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
1000.
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