全文获取类型
收费全文 | 168385篇 |
免费 | 1323篇 |
国内免费 | 193篇 |
专业分类
电工技术 | 2553篇 |
综合类 | 119篇 |
化学工业 | 26611篇 |
金属工艺 | 9471篇 |
机械仪表 | 5715篇 |
建筑科学 | 3008篇 |
矿业工程 | 1887篇 |
能源动力 | 2703篇 |
轻工业 | 8815篇 |
水利工程 | 2729篇 |
石油天然气 | 8692篇 |
武器工业 | 12篇 |
无线电 | 14495篇 |
一般工业技术 | 38250篇 |
冶金工业 | 27794篇 |
原子能技术 | 6933篇 |
自动化技术 | 10114篇 |
出版年
2018年 | 2979篇 |
2017年 | 3094篇 |
2016年 | 3346篇 |
2015年 | 1672篇 |
2014年 | 2955篇 |
2013年 | 6338篇 |
2012年 | 4314篇 |
2011年 | 5399篇 |
2010年 | 4422篇 |
2009年 | 4894篇 |
2008年 | 4940篇 |
2007年 | 4868篇 |
2006年 | 4143篇 |
2005年 | 3819篇 |
2004年 | 3634篇 |
2003年 | 3520篇 |
2002年 | 3450篇 |
2001年 | 3463篇 |
2000年 | 3361篇 |
1999年 | 3213篇 |
1998年 | 7018篇 |
1997年 | 5148篇 |
1996年 | 3821篇 |
1995年 | 2916篇 |
1994年 | 2593篇 |
1993年 | 2720篇 |
1992年 | 2254篇 |
1991年 | 2304篇 |
1990年 | 2409篇 |
1989年 | 2315篇 |
1988年 | 2313篇 |
1987年 | 2190篇 |
1986年 | 2246篇 |
1985年 | 2292篇 |
1984年 | 2206篇 |
1983年 | 2135篇 |
1982年 | 1980篇 |
1981年 | 2193篇 |
1980年 | 2053篇 |
1979年 | 2269篇 |
1978年 | 2431篇 |
1977年 | 2430篇 |
1976年 | 3095篇 |
1975年 | 2244篇 |
1974年 | 2307篇 |
1973年 | 2342篇 |
1972年 | 2155篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
1969年 | 1632篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
891.
The excavation of soil for the construction of basements or cut-and-cover tunnels results in ground movements. One particular concern is that the excavation-induced lateral soil movements may adversely affect any nearby pile foundation. The lateral loads imposed by the soil movements induce bending moments and deflections in the pile, which may lead to structural distress and failure. This paper presents the results of an actual full-scale instrumented study that was carried to examine the behavior of an existing pile due to nearby excavation activities resulting from the construction of a 16 m deep cut-and-cover tunnel. The pile was located 3 m behind a 0.8 m thick diaphragm wall. Excavation to the formation level that was 16 m below the ground surface resulted in a maximum lateral pile movement of 28 mm. A simplified numerical procedure based on the finite-element method was used to analyze the pile response. Generally, the theoretical predictions were in reasonable agreement with the measured results. 相似文献
892.
L. V. Krylov Yu. N. Melent'ev V. I. Yatsenko V. V. Nikitin L. V. Maksimova I. N. Knyazeva 《Metallurgist》1991,35(2):32-32
Magnitogorsk Metallurgical Combine. Translated from Metallurg, No. 2, p. 37, February, 1991. 相似文献
893.
Y Paltieli A Weichselbaum N Hoffman I Eibschitz Z Kam 《Canadian Metallurgical Quarterly》1995,10(7):1638-1641
Based on a laser light scattering technique and fibre optic probe, we have developed and tested a simple and practical device for real time measurements of ciliary activity in human Fallopian tubes during laparoscopy and laparotomy. A further aim was to investigate the relationship between the ciliary beat frequency (CBF) and the morphology of the ciliary epithelium. The mean +/- SE of CBF in the fimbria and in the ampulla were 5.4 +/- 0.3 Hz and 5.0 +/- 0.1 Hz respectively. Small pieces of fimbria and ampulla epithelium were taken from the same sites at which the CBF was measured, and the percentage of ciliary cells was determined by scanning electron microscopy. A high positive correlation was found between CBF and the percentage of ciliary cells in the fimbria (r = 0.84) and in the ampulla (r = 0.88). The instrument presented in this study provided, for the first time, a quantitative examination of the CBF in intact human Fallopian tubes and may be used for the investigation of ciliary activity in patients with infertility. 相似文献
894.
Summary The cationic polymerization of 2-ethyl-2-oxazoline using CH3I as initiator at different monomer/initiator ratios, temperatures, solvents and times of polymerization was carried out. The effect of these variables on the polymerization yield and viscosity of the polymers was studied. The poly(N-propionyl)iminoethylene was hydrolyzed in acid medium obtaining a linear poly(ethyleneimine) (PEI). All the polymers were characterized by elemental analysis, IR,1H NMR, and13C NMR spectroscopy. 相似文献
895.
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 3, pp. 20–22, March, 1991. 相似文献
896.
G. T. Vigant A. B. Énglin N. N. Zakharova I. V. Klimyuk 《Chemistry and Technology of Fuels and Oils》1991,27(5):244-248
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, 11–13, May, 1991. 相似文献
897.
A polypropylene-based binder system was used to injection mould test bars containing 65 vol% aluminium powder. Specimens, 3 and 6 mm thick, made from these bars were used for pyrolytic binder removal experiments in static air and nitrogen. The development of a carefully defined experimental procedure for the determination of the heating rate at which binder removal can be carried out at a given temperature without the creation of macro defects is fully described. The use of isothermal heat treatments during pyrolysis are also considered and results are presented as temperature-heating rate diagrams for each atmosphere and thickness investigated. These diagrams show a lower and an upper boundary. Defect formation occurs if the temperature-heating rate relationship lies between the boundaries. Near optimum binder removal schedules deduced from each diagram have been experimentally verified. 相似文献
898.
We report on first computations considering effects of a rough wall on the counterflow state in superfluid 3He-B for high flow velocities. Using the quasiclassical Green's-function formalism supplemented by the boundary conditions for a diffusive wall, we calculate the order-parameter field and the supercurrent near a container wall for various pressures and temperatures. One of our results is that the current density at the wall as a function of the flow has a maximum at the velocity which is about half of the pair breaking velocity. 相似文献
899.
This paper is a summary of an extensive research program carried out by the authors on the structure of rapidly solidified aluminum alloys; and a comparison with the work of others also involved in this field. The paper discusses the changes in the dendritic and non-dendritic structure of the matrix at cooling rates from 10–3 to 1010 K/s and discusses the hetergeneity of the structure caused by interdendritic-segretion during solidification. 相似文献
900.