全文获取类型
收费全文 | 529883篇 |
免费 | 5230篇 |
国内免费 | 931篇 |
专业分类
电工技术 | 9673篇 |
综合类 | 640篇 |
化学工业 | 82568篇 |
金属工艺 | 23985篇 |
机械仪表 | 17795篇 |
建筑科学 | 11615篇 |
矿业工程 | 4431篇 |
能源动力 | 11785篇 |
轻工业 | 39028篇 |
水利工程 | 6340篇 |
石油天然气 | 15319篇 |
武器工业 | 34篇 |
无线电 | 56517篇 |
一般工业技术 | 113979篇 |
冶金工业 | 85081篇 |
原子能技术 | 15621篇 |
自动化技术 | 41633篇 |
出版年
2021年 | 4745篇 |
2019年 | 4586篇 |
2018年 | 8404篇 |
2017年 | 8543篇 |
2016年 | 8966篇 |
2015年 | 5272篇 |
2014年 | 9182篇 |
2013年 | 22983篇 |
2012年 | 13804篇 |
2011年 | 17941篇 |
2010年 | 14324篇 |
2009年 | 16259篇 |
2008年 | 16734篇 |
2007年 | 16412篇 |
2006年 | 14011篇 |
2005年 | 12685篇 |
2004年 | 12517篇 |
2003年 | 12141篇 |
2002年 | 11810篇 |
2001年 | 11852篇 |
2000年 | 11438篇 |
1999年 | 11169篇 |
1998年 | 23757篇 |
1997年 | 17820篇 |
1996年 | 13865篇 |
1995年 | 11037篇 |
1994年 | 10119篇 |
1993年 | 10071篇 |
1992年 | 8104篇 |
1991年 | 8017篇 |
1990年 | 8004篇 |
1989年 | 7787篇 |
1988年 | 7535篇 |
1987年 | 6804篇 |
1986年 | 6835篇 |
1985年 | 7694篇 |
1984年 | 7185篇 |
1983年 | 6850篇 |
1982年 | 6255篇 |
1981年 | 6487篇 |
1980年 | 6209篇 |
1979年 | 6333篇 |
1978年 | 6373篇 |
1977年 | 6945篇 |
1976年 | 8432篇 |
1975年 | 5701篇 |
1974年 | 5664篇 |
1973年 | 5726篇 |
1972年 | 4967篇 |
1971年 | 4501篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This paper presents some improvements to the load flow solution in rectangular coordinates. First, in an attempt to use as linear a model as possible, both the nodal equations and the bus constraints are retained. The Newton-Raphson (NR) method is then applied to the enlarged set of equations, and written in terms of bus voltages and currents. This scheme, combined with a simple procedure to handle PV buses, leads to a computationally efficient algorithm, particularly advantageous in the presence of zero-injection buses. Experimental results are provided comparing the performance of the proposed approach with that of the conventional formulation 相似文献
992.
C. N. Cacaval E. C. BuruianÎ D. Rou E. Rusu G. E. Grigoriu V. Brboiu 《Polymer International》1985,17(4):343-346
Thermogravimetry and pyrolysis in combination with gas chromatography and infrared spectroscopy were the experimental techniques applied to the thermal degradation of cinnamoylated poly(vinyl alcohol) samples, constituted from vinyl alcohol-vinyl cinnamate photocrosslinkable copolymers. The thermal decomposition products include gases, liquids and solids. The gases are formed from saturated and unsaturated volatile hydrocarbons C1? C4, carbon monoxide and carbon dioxide. The liquid fraction includes aromatic hydrocarbons and some oxygenated organic compounds. The solid product identified in the greatest amount was cinnamic acid. The content in the thermal decomposition products varies considerably both with copolymer composition and temperature. 相似文献
993.
994.
P. V. Pakshin V. V. Pozdyaev 《Journal of Computer and Systems Sciences International》2006,45(5):681-689
The necessary and sufficient conditions for solvability of a second-order system of linear matrix inequalities that can be reduced to two or three scalar inequalities of the second order are presented. 相似文献
995.
996.
Currently, two motivators are effecting change in power systems education. First, the industry's transition to a more competitive environment is requiring changes in the content and pedagogy of power systems education. Second, engineering education as a whole is seeking to modify its curriculum to reflect a better balance between science and education in order to better meet the needs of industry. These curricular changes are largely a result of revised Accreditation Board for Engineering and Technology (ABET) accreditation requirements. In response to these changes, new curriculum and analysis tools were developed for a power systems capstone design course. The project integrates market economics and socio-political considerations with transient stability analysis and transmission planning. A power systems analysis package and an economic analysis tool were developed for use with this project. Student evaluations of the course in which the project was implemented indicate that the curriculum successfully addresses a broad range of ABET accreditation criteria. 相似文献
997.
S. O. Shiryaeva A. I. Grigor’ev V. A. Koromyslov A. S. Golovanov 《Technical Physics Letters》2002,28(1):41-43
A dispersion equation for the capillary oscillations of a charged drop of incompressible liquid possessing a finite electric
conductivity is derived with an allowance for the energy lost as a result of the electromagnetic wave emission. The magnitude
of the electromagnetic radiation losses of the oscillating drop linearly increases with the electric conductivity and the
surface mobility of charge carriers. 相似文献
998.
V. V. Skurat N. M. Shiryaeva N. K. Myshkina A. A. Gvozdev G. Z. Serebryanyi N. B. Golikova 《Journal of Engineering Physics and Thermophysics》2002,75(5):1200-1206
Unsatisfactory conditions of storage of decontamination waste (DW) in the storages formed in the territory of Belarus after the Chernobyl accident require the evaluation of the level of protection of the environment and population. The potential hazard of the decontamination waste burial grounds (DWBGs) has been evaluated based on the use of a generalized multichamber model that was verified by comparing the calculation results and the results obtained by the American (GW SCREEN) model. The characteristics of the 24 largest and most hazardous DWBGs are given and the evaluations of their safety are presented. The zones of influence of these storages, whose size varies from 100 to 330 m, have been determined. The reliability of the prediction evaluation of a possible hazardous radioactive contamination of water near the storages has been verified using the Dudichi DWBG as an example. 相似文献
999.
V. G. Gorobets 《Journal of Engineering Physics and Thermophysics》2002,75(5):1130-1138
A mathematical model of heat transfer has been developed and numerical calculations for a vertical surface with discrete fins arranged in staggered order have been carried out. The model accounts for the influence of the heat-conduction properties of the finning material and of the fin size on the conditions of heat transfer. A comparison of the results obtained with the existing numerical and experimental data has been made. This comparison shows that the discretization intensifies the heat-transfer process by 50–70%, and neglect of the heat-conduction properties of the fins leads to overstated values of the removed heat fluxes. 相似文献
1000.