首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   702391篇
  免费   17911篇
  国内免费   7065篇
电工技术   18598篇
技术理论   9篇
综合类   9169篇
化学工业   112352篇
金属工艺   30982篇
机械仪表   26815篇
建筑科学   22013篇
矿业工程   7834篇
能源动力   17879篇
轻工业   54972篇
水利工程   9621篇
石油天然气   22233篇
武器工业   1084篇
无线电   75269篇
一般工业技术   134888篇
冶金工业   102829篇
原子能技术   17225篇
自动化技术   63595篇
  2022年   8040篇
  2021年   11206篇
  2020年   8296篇
  2019年   8785篇
  2018年   13269篇
  2017年   13876篇
  2016年   13797篇
  2015年   11136篇
  2014年   16636篇
  2013年   33747篇
  2012年   24222篇
  2011年   30073篇
  2010年   24624篇
  2009年   26250篇
  2008年   26429篇
  2007年   25628篇
  2006年   22876篇
  2005年   20363篇
  2004年   18151篇
  2003年   17817篇
  2002年   17455篇
  2001年   16651篇
  2000年   15506篇
  1999年   14942篇
  1998年   29899篇
  1997年   21863篇
  1996年   17277篇
  1995年   13498篇
  1994年   12055篇
  1993年   11551篇
  1992年   9194篇
  1991年   8805篇
  1990年   8609篇
  1989年   8332篇
  1988年   7967篇
  1987年   7181篇
  1986年   6889篇
  1985年   7705篇
  1984年   6995篇
  1983年   6698篇
  1982年   6067篇
  1981年   6188篇
  1980年   5902篇
  1979年   6045篇
  1978年   5993篇
  1977年   6478篇
  1976年   8015篇
  1975年   5426篇
  1974年   5202篇
  1973年   5291篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
A series of small–capacity units has recently been constructed in regions of oil field development and crude oil and gas condensate production to satisfy the requirements for such petroleum products as naphtha, diesel fuel, kerosene, and boiler fuel and to reduce costs for delivery of these products. There are almost no data in the technical literature, particularly in periodicals, on the construction and operation of small–capacity units. We attempt to generalize the experience of Orgeneftekhimzavody Trust in this area. We hope that this experience will be useful to specialists in the development and management of small–capacity plants.  相似文献   
22.
The magneto-optical Kerr effect for red (628 nm) and green (532 nm) light is used to study magnetization processes in 2D magnonic crystals obtained by etching pits with the diameter D ≈ 32 μm to a depth of t ≤ 2 μm in a 16.1-μm-thick film of yttrium iron garnet (YIG). Hysteresis loops obtained in the case of the inplane crystal magnetization at 628 nm are characterized by lower saturation fields H s and higher remanent magnetizations than those obtained at 532 nm, a result that is attributed to different absorption coefficients of the YIG film at these wavelengths. This difference between the magnetization curves reflects the fact that the magnonic-crystal surface probed with the green light makes a greater contribution to the magneto-optical Kerr effect. Therefore, the green light is more sensitive to the demagnetizing fields, which govern magnetization processes in the magnonic crystals.  相似文献   
23.
A VQ-based blind image restoration algorithm   总被引:5,自引:0,他引:5  
Learning-based algorithms for image restoration and blind image restoration are proposed. Such algorithms deviate from the traditional approaches in this area, by utilizing priors that are learned from similar images. Original images and their degraded versions by the known degradation operator (restoration problem) are utilized for designing the VQ codebooks. The codevectors are designed using the blurred images. For each such vector, the high frequency information obtained from the original images is also available. During restoration, the high frequency information of a given degraded image is estimated from its low frequency information based on the codebooks. For the blind restoration problem, a number of codebooks are designed corresponding to various versions of the blurring function. Given a noisy and blurred image, one of the codebooks is chosen based on a similarity measure, therefore providing the identification of the blur. To make the restoration process computationally efficient, the principal component analysis (PCA) and VQ-nearest neighbor approaches are utilized. Simulation results are presented to demonstrate the effectiveness of the proposed algorithms.  相似文献   
24.
A nonstationary model of SO2 absorption from a gas phase to a countercurrent falling film of absorbing slurry was developed. Laminar, wavy and turbulent film structures were considered based on published information. Resistances to the mass transfer on the gas and the liquid sides of the interphase were considered, together with chemical reactions in the liquid phase. Relevant chemical equilibria in the liquid phase were modeled. Original experimental data on the neutralization reagent dissolution rate presented as a polydispersed two‐phase system of solids and on the rate of dissolved sulfite oxidation were used. The model was verified with experimental data from a laboratory‐scale falling‐film absorber using a single vertical tube under various geometrical and operating conditions, and a very good agreement was found with the experiment. Parametric sensitivity analysis showed the critical parts of the model.  相似文献   
25.
The microstructure evolution in nonstoichiometric titanium carbide is studied during high-temperature deformation at high strain rates and low strains (shock compression) and at slow strain rates and high strains (superplastic regime). The results demonstrate that high-temperature deformation in a broad range of strain rates offers a means of controlling the microstructure of titanium carbide. By varying deformation conditions, one can obtain materials differing in microstructure and chemical composition, in particular, with equilibrium and nonequilibrium microstructures. Accordingly, the physicochemical properties of such materials also differ.  相似文献   
26.
水电站运行过程中河床变形会使河底高程逐渐降低。从而导致下游流量特性曲线下降以及水电站水头增大。水头增大使水电站气蚀特性发生变化,导致动力设备的正常工作条件受到破坏。并对其运行安全性和效率造成不利影响。以卡马河的沃特金水电站为例,阐述了河床变形对水电站动力设备工作条件的影响。  相似文献   
27.
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.  相似文献   
28.
29.
Phase equilibria involving spinel solid solutions, delafossite, and hematite in the Fe–Cu–O system are studied by emf measurements in solid-electrolyte galvanic cells. The results demonstrate that, above 1250 K, Fe3O4 and CuFe2O4 form a continuous series of solid solutions. At lower temperatures, the solid solution disproportionates with the formation of delafossite and Fe2O3, and two spinel solid solutions appear: one based on Fe3O4 and the other based on Cu2FeO4. The compositions of the spinel phases in equilibrium with delafossite and Fe2O3 are determined in the range 1100–1250 K.  相似文献   
30.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号