全文获取类型
收费全文 | 69533篇 |
免费 | 5707篇 |
国内免费 | 3020篇 |
专业分类
电工技术 | 3939篇 |
技术理论 | 10篇 |
综合类 | 4580篇 |
化学工业 | 11608篇 |
金属工艺 | 3604篇 |
机械仪表 | 3977篇 |
建筑科学 | 5488篇 |
矿业工程 | 1878篇 |
能源动力 | 1943篇 |
轻工业 | 5427篇 |
水利工程 | 1313篇 |
石油天然气 | 3719篇 |
武器工业 | 539篇 |
无线电 | 8308篇 |
一般工业技术 | 8586篇 |
冶金工业 | 3444篇 |
原子能技术 | 728篇 |
自动化技术 | 9169篇 |
出版年
2024年 | 315篇 |
2023年 | 1189篇 |
2022年 | 2106篇 |
2021年 | 2914篇 |
2020年 | 2269篇 |
2019年 | 1801篇 |
2018年 | 2067篇 |
2017年 | 2159篇 |
2016年 | 2113篇 |
2015年 | 2701篇 |
2014年 | 3382篇 |
2013年 | 3927篇 |
2012年 | 4360篇 |
2011年 | 4766篇 |
2010年 | 3930篇 |
2009年 | 3741篇 |
2008年 | 3728篇 |
2007年 | 3492篇 |
2006年 | 3320篇 |
2005年 | 2900篇 |
2004年 | 2169篇 |
2003年 | 1922篇 |
2002年 | 1752篇 |
2001年 | 1567篇 |
2000年 | 1707篇 |
1999年 | 2040篇 |
1998年 | 1735篇 |
1997年 | 1421篇 |
1996年 | 1403篇 |
1995年 | 1158篇 |
1994年 | 1010篇 |
1993年 | 703篇 |
1992年 | 550篇 |
1991年 | 398篇 |
1990年 | 341篇 |
1989年 | 311篇 |
1988年 | 221篇 |
1987年 | 156篇 |
1986年 | 111篇 |
1985年 | 81篇 |
1984年 | 61篇 |
1983年 | 42篇 |
1982年 | 52篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1979年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The effect of the atomic mobility on a film surface has been studied by using a three-dimensional atomistic thin-film deposition model which simulates three-dimensional thin-film images, surface profiles and cross-sectional area pictures. In addition, quantitative results of surface RMS roughness, average film thickness, atomic coordination number and its distribution, and solid fraction of the deposited thin films, were obtained from the simulations. When the film surface mobility increased from 0.3 to 3.0, RMS roughness decreased from 6.5 to 1.1, solid fraction increased from 0.27 to 0.56 and average film thickness decreased from 40 to 28, due to the reduction of the voids within the film. The full-width half magnitude of the atomic coordination distribution became narrower indicating the increased degree of crystallization. With increase in surface mobility crossing the boundary to 1.5, the film evolved from a porous or loose columnar structure with voids, to a densely packed fibrous grain structure which can be categorized by the zone structure models. 相似文献
22.
23.
24.
25.
26.
Lada E.K. Jye-Chyi Lu Wilson J.R. 《Semiconductor Manufacturing, IEEE Transactions on》2002,15(1):79-90
To detect faults in a time-dependent process, we apply a discrete wavelet transform (DWT) to several independently replicated data sets generated by that process. The DWT can capture irregular data patterns such as sharp "jumps" better than the Fourier transform and standard statistical procedures without adding much computational complexity. Our wavelet coefficient selection method effectively balances model parsimony against data reconstruction error. The few selected wavelet coefficients serve as the "reduced-size" data set to facilitate an efficient decision-making method in situations with potentially large-volume data sets. We develop a general procedure to detect process faults based on differences between the reduced-size data sets obtained from the nominal (in-control) process and from a new instance of the target process that must be tested for an out-of-control condition. The distribution of the test statistic is constructed first using normal distribution theory and then with a new resampling procedure called "reversed jackknifing" that does not require any restrictive distributional assumptions. A Monte Carlo study demonstrates the effectiveness of these procedures. Our methods successfully detect process faults for quadrupole mass spectrometry samples collected from a rapid thermal chemical vapor deposition process 相似文献
27.
28.
29.
Aerodynamic loads on a multi-bladed helicopter rotor in hovering flight were calculated by solving the three-dimensional incompressible Navier-Stokes equations. The rotor wake effects were accounted by the correction of local geometric angle of attack according to a free-wake modeling in addition to an empirical modification for the tip flow effect. The validity and efficiency of the present method were verified by the comparisons between numerical results and experimental data. 相似文献
30.
The development and test of a PLC control program takes time, increases equipment down-time, and might damage hardware due to program errors. All of these problems can be eliminated if there is a computer simulation system for testing control programs off line. This paper presented a new method, called Direct Sequential Method, for simulating PLCs. This method resolves a ladder logic sequentially by applying a series of logic deductions. This simulation system has been implemented in C and tested successfully. 相似文献