全文获取类型
收费全文 | 12041篇 |
免费 | 1196篇 |
国内免费 | 239篇 |
专业分类
电工技术 | 382篇 |
综合类 | 348篇 |
化学工业 | 2860篇 |
金属工艺 | 593篇 |
机械仪表 | 711篇 |
建筑科学 | 458篇 |
矿业工程 | 148篇 |
能源动力 | 526篇 |
轻工业 | 1113篇 |
水利工程 | 108篇 |
石油天然气 | 158篇 |
武器工业 | 23篇 |
无线电 | 1760篇 |
一般工业技术 | 2173篇 |
冶金工业 | 578篇 |
原子能技术 | 122篇 |
自动化技术 | 1415篇 |
出版年
2024年 | 32篇 |
2023年 | 184篇 |
2022年 | 335篇 |
2021年 | 458篇 |
2020年 | 347篇 |
2019年 | 331篇 |
2018年 | 415篇 |
2017年 | 405篇 |
2016年 | 456篇 |
2015年 | 480篇 |
2014年 | 637篇 |
2013年 | 828篇 |
2012年 | 887篇 |
2011年 | 953篇 |
2010年 | 752篇 |
2009年 | 780篇 |
2008年 | 691篇 |
2007年 | 562篇 |
2006年 | 550篇 |
2005年 | 432篇 |
2004年 | 341篇 |
2003年 | 392篇 |
2002年 | 350篇 |
2001年 | 265篇 |
2000年 | 226篇 |
1999年 | 214篇 |
1998年 | 233篇 |
1997年 | 138篇 |
1996年 | 132篇 |
1995年 | 115篇 |
1994年 | 80篇 |
1993年 | 65篇 |
1992年 | 70篇 |
1991年 | 46篇 |
1990年 | 45篇 |
1989年 | 42篇 |
1988年 | 25篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 11篇 |
1984年 | 17篇 |
1983年 | 18篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1978年 | 6篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1975年 | 6篇 |
1973年 | 3篇 |
1969年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
We propose an efficient scheme for camera motion characterization in MPEG‐compressed video. The proposed scheme detects six types of basic camera motions through threshold‐based qualitative interpretation, in which fixed thresholds are applied to motion model parameters estimated from MPEG motion vectors (MVs). The efficiency and robustness of the scheme are validated by the experiment with real compressed video sequences. 相似文献
42.
Animesh Chakrabarti Man Mohan Sharma 《Journal of the American Oil Chemists' Society》1992,69(12):1251-1253
Anhydrous esterification of myristic acid with propylene was carried out in the temperature range of 110–145°C and pressure
from 190–195 psig in the presence of Amberlyst-15 (cation exchange resin) and Filtrol-24 (acid-treated clay) as catalysts.
The product ester, isopropyl myristate finds use in cosmetic and topical medicinal preparations where good absorption through
the skin is desired. Filtrol-24 is the catalyst of choice, and the recommended operating temperature is 130°C with a pressure
of 190 psig. 相似文献
43.
44.
Joo-Wan Kim Byung Sung Kim Sangwook Nam Choong Woong Lee 《Antennas and Propagation, IEEE Transactions on》1996,44(7):996-999
To specify manufacturing tolerances of a reflector antenna, various errors such as random surface errors and misalignment errors must be considered at one time because superposition of the effects of those errors may not hold. Based on the Rahmat-Samii's formulation (1983), a method for computing efficiently the average power pattern of a reflector antenna with those errors is presented. Simulation results show that superposition of the effects of errors does not generally hold and demonstrate how those errors degrade the peak-gain and sidelobe levels 相似文献
45.
The energy release rate, which is the total derivative of the energy with respect to crack length, is recognized as corresponding to the shape sensitivity analysis with the crack length change represented by the tangential component of design velocity. In this paper the sensitivity formula recently developed for a changing boundary condition has been further extended to cover crack kinking under mixed mode loading. Due to difficulty in defining the velocity field at the corner, the energy release rate at the onset of crack kinking is obtained by extrapolating the energy release rates for finite length kinked cracks. A rectangular plate with a single edge slant crack under uniform tension is taken as a numerical example. The multi-region technique in the numerical implementation of the boundary integral equation is adopted to consider the asymmetry of the problem. Excellent accuracy is observed as compared with reference analytic solutions. 相似文献
46.
The humidity response characteristics of La doped BaTiO3 with different sintered densities and room temperature electrical conductivities were investigated using complex impedance measurement. The samples with low density and high resistivity showed the large and nearly linear sensitivity to the change of humidity. The impedance spectra of samples, when exposed to high humidity, can exhibit microstructure-related features, even though they do not give rise to a noticeable characteristic change when exposed to low humidity. The observed impedance patterns were dependent upon the density, and hence the oxidation kinetics of BaTiO3. 相似文献
47.
48.
Balasa F. Catthoor F. Hugo De Man 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1995,3(2):157-172
Memory cost is responsible for a large amount of the chip and/or board area of customized video and image processing system realizations. In this paper, we present a novel technique-founded on data-flow analysis which allows one to address the problem of background memory size evaluation for a given nonprocedural algorithm specification, operating on multidimensional signals with affine indexes. Most of the target applications are characterized by a huge number of signals, so a new polyhedral data-flow model operating on groups of scalar signals is proposed. These groups are obtained by a novel analytical partitioning technique, allowing to select a desired granularity, depending on the application complexity. The method incorporates a way to tradeoff memory size with computational and controller complexity 相似文献
49.
Hoon C. Park Chahngmin Cho Sung W. Lee 《International journal for numerical methods in engineering》1995,38(24):4101-4122
The present paper describes an assumed strain finite element model with six degrees of freedom per node designed for geometrically non-linear shell analysis. An important feature of the present paper is the discussion on the spurious kinematic modes and the assumed strain field in the geometrically non-linear setting. The kinematics of deformation is described by using vector components in contrast to the conventional formulation which requires the use of trigonometric functions of rotational angles. Accordingly, converged solutions can be obtained for load or displacement increments that are much larger than possible with the conventional formulation with rotational angles. In addition, a detailed study of the spurious kinematic modes and the choice of assumed strain field reveals that the same assumed strain field can be used for both geometrically linear and non-linear cases to alleviate element locking while maintaining kinematic stability. It is strongly recommended that the element models, described in the present paper, be used instead of the conventional shell element models that employ rotational angles. 相似文献
50.
刍议小型水电站项目收购风险管理 总被引:1,自引:0,他引:1
相对于其他项目的收购风险评估,小型水电站(电站总装机容量5万kW以下)收购有其特殊性。在总结和归纳小型水电站特点的基础上,结合一般项目收购风险评估方法,分析项目收购各个阶段存在的风险和对策。为有收购水电项目意向的企业和个人提供决策依据。图1幅。 相似文献