全文获取类型
收费全文 | 29698篇 |
免费 | 3365篇 |
国内免费 | 2050篇 |
专业分类
电工技术 | 3060篇 |
技术理论 | 1篇 |
综合类 | 5030篇 |
化学工业 | 3651篇 |
金属工艺 | 866篇 |
机械仪表 | 1740篇 |
建筑科学 | 1338篇 |
矿业工程 | 526篇 |
能源动力 | 736篇 |
轻工业 | 1112篇 |
水利工程 | 800篇 |
石油天然气 | 1711篇 |
武器工业 | 368篇 |
无线电 | 2914篇 |
一般工业技术 | 3665篇 |
冶金工业 | 803篇 |
原子能技术 | 456篇 |
自动化技术 | 6336篇 |
出版年
2024年 | 75篇 |
2023年 | 311篇 |
2022年 | 534篇 |
2021年 | 702篇 |
2020年 | 775篇 |
2019年 | 784篇 |
2018年 | 824篇 |
2017年 | 928篇 |
2016年 | 1022篇 |
2015年 | 1035篇 |
2014年 | 1503篇 |
2013年 | 1943篇 |
2012年 | 2206篇 |
2011年 | 2159篇 |
2010年 | 1682篇 |
2009年 | 1689篇 |
2008年 | 1667篇 |
2007年 | 1851篇 |
2006年 | 1807篇 |
2005年 | 1452篇 |
2004年 | 1281篇 |
2003年 | 1216篇 |
2002年 | 1023篇 |
2001年 | 805篇 |
2000年 | 788篇 |
1999年 | 731篇 |
1998年 | 642篇 |
1997年 | 546篇 |
1996年 | 512篇 |
1995年 | 476篇 |
1994年 | 387篇 |
1993年 | 322篇 |
1992年 | 280篇 |
1991年 | 241篇 |
1990年 | 199篇 |
1989年 | 169篇 |
1988年 | 119篇 |
1987年 | 78篇 |
1986年 | 55篇 |
1985年 | 59篇 |
1984年 | 40篇 |
1983年 | 28篇 |
1982年 | 39篇 |
1981年 | 28篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1964年 | 10篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
A recently proposed argument to explain the improved performance of the eight-point algorithm that results from using normalized
data (Chojnacki, W., et al. in IEEE Trans. Pattern Anal. Mach. Intell. 25(9):1172–1177, 2003) relies upon adoption of a certain model for statistical data distribution. Under this model, the cost function that underlies
the algorithm operating on the normalized data is statistically more advantageous than the cost function that underpins the
algorithm using unnormalized data. Here we extend this explanation by introducing a more refined, structured model for data
distribution. Under the extended model, the normalized eight-point algorithm turns out to be approximately consistent in a
statistical sense. The proposed extension provides a link between the existing statistical rationalization of the normalized
eight-point algorithm and the approach of Mühlich and Mester for enhancing total least squares estimation methods via equilibration.
The paper forms part of a wider effort to rationalize and interrelate foundational methods in vision parameter estimation. 相似文献
73.
本文提出了求解非线性问题的一种新方法——逐次迭代法,本方法先是给出一个初始近似解,然后将这个近似解进行校正迭代,使之接近于真实解,把一个非线性问题转化为一个线性问题来解决。 相似文献
74.
石蜡微胶囊中脲醛树脂壁材渗透性的研究 总被引:7,自引:0,他引:7
利用差示扫描量热法研究了石蜡微胶囊中脲醛树脂壁材对水及甲苯的渗透性 ,结果表明 ,水不能透过脲醛树脂壁材 ,而甲苯则易透过脲醛树脂壁材。因此 ,该石蜡微胶囊不能用于芳香族溶剂存在的场合。 相似文献
75.
Qing-Chang Zhong Author Vitae 《Automatica》2003,39(3):499-508
This paper generalizes the frequency-domain results on the delay-type Nehari problem in the stable case to the unstable case. The solvability condition of the delay-type Nehari problem is formulated in terms of the nonsingularity of three matrices. The optimal value γopt is the maximal γ∈(0,∞) such that one of the three matrices becomes singular. All sub-optimal compensators are parameterized in a transparent structure incorporating a modified Smith predictor. 相似文献
76.
根据双点后方交会的图形特点和已知条件,列出了方程组,推导出了双点后方交会直接计算座标的简便公式,同时求出了精度计算公式,以供测量人员参考 相似文献
77.
A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional
conductor. The negative differential resistance region appears afterV
m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms
of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals. 相似文献
78.
用保形样条方法求解非定常对流扩散方程 总被引:1,自引:0,他引:1
在欧拉-拉格朗日分裂方法的基础上,本文发展了一种固定网格上的欧拉-拉格朗日分裂方法.保形样条方法(SPSM)被用来解决倒特征线插值问题.通过求解几个有精确解的例子,说明SPSM方法的解是单调无振荡的,并且数值耗散也是比较小的. 相似文献
79.
J.M Mäkynen J.K Jokiniemi P.P Ahonen E.I Kauppinen R Zilliacus 《Nuclear Engineering and Design》1997,178(1):74
Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at different temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m3 total free volume. Homogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were measured continuously during the experiments using a Condensation Nucleus Counter and a Tapered Element Oscillating Microbalance. The particle size distribution and chemical composition in the test conditions were measured by Berner low pressure impactors. In the case of NaOH the half life of the aerosol mass concentration was more than four times longer at low RH (22%) as compared to high RH (96%). The half lives of the CsOH and CsI aerosols were only twice as long at low RH as compared to high RH. Thus at high RH (96–97%) the half lives of CsOH and CsI were twice as long as the half life for the NaOH aerosol. The faster decay of the NaOH aerosol is due to the smaller density decrease of NaOH during water condensation. CsOH particles grew rapidly to their equilibrium size at all humidities. The measured equilibrium size for CsOH aerosol agree well with the calculated particle size at different RHs. Experimental results were also compared with calculations obtained by severe accident computer codes. These calculated results will be presented in a later paper. 相似文献
80.