全文获取类型
收费全文 | 26221篇 |
免费 | 3340篇 |
国内免费 | 2272篇 |
专业分类
电工技术 | 2413篇 |
技术理论 | 7篇 |
综合类 | 3813篇 |
化学工业 | 657篇 |
金属工艺 | 239篇 |
机械仪表 | 1302篇 |
建筑科学 | 8423篇 |
矿业工程 | 397篇 |
能源动力 | 393篇 |
轻工业 | 391篇 |
水利工程 | 305篇 |
石油天然气 | 502篇 |
武器工业 | 280篇 |
无线电 | 3077篇 |
一般工业技术 | 1847篇 |
冶金工业 | 271篇 |
原子能技术 | 173篇 |
自动化技术 | 7343篇 |
出版年
2024年 | 115篇 |
2023年 | 345篇 |
2022年 | 653篇 |
2021年 | 746篇 |
2020年 | 793篇 |
2019年 | 721篇 |
2018年 | 693篇 |
2017年 | 814篇 |
2016年 | 982篇 |
2015年 | 1129篇 |
2014年 | 1958篇 |
2013年 | 1624篇 |
2012年 | 2161篇 |
2011年 | 2280篇 |
2010年 | 1952篇 |
2009年 | 1877篇 |
2008年 | 1863篇 |
2007年 | 1981篇 |
2006年 | 1719篇 |
2005年 | 1354篇 |
2004年 | 1057篇 |
2003年 | 859篇 |
2002年 | 715篇 |
2001年 | 616篇 |
2000年 | 551篇 |
1999年 | 443篇 |
1998年 | 319篇 |
1997年 | 245篇 |
1996年 | 211篇 |
1995年 | 203篇 |
1994年 | 167篇 |
1993年 | 125篇 |
1992年 | 132篇 |
1991年 | 73篇 |
1990年 | 65篇 |
1989年 | 68篇 |
1988年 | 54篇 |
1987年 | 28篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1960年 | 3篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献
32.
Until recently, numerical simulations of discontinuities in highly super-Alfvénic plasmas have been severely limited by comparatively crude resolution and accuracy. Significant progress in the numerical simulation of such plasmas was achieved with the recently implemented Central Weighted Essentially Non-Oscillatory (CWENO) scheme. Combining this technique with that of adaptive mesh refinement (AMR), we have developed a third-order numerical scheme, which is able to efficiently capture strong gradients on spatial scales being small compared to the overall scale of the plasma system considered. Here, we first describe important algorithmic aspects of the scheme as well as the physics included in it. Second, we present the results of various performance tests. And, third, we illustrate its application to ‘real world problems’ using the example of the dynamics of a Sedov-type explosion. 相似文献
33.
钻一口通过主采盐层的水平井与已完成的直井对接,形成连通井(形如“U”字),一口井注水溶解盐/芒硝矿,另一口井采出卤水,这是盐化工业对钻井提出的要求。针对水平对接盐井井身轨迹设计、着陆段、水平段的轨迹控制和连通技术,介绍了水平段侧钻时的钻井液技术。 相似文献
34.
35.
中心加权中值滤波具有较好的边缘保持特性及快速实现的特点,但滤噪能力低于其它中值滤波。此文探
讨对中心加权中值滤波的改进方法,提出了中心加权分级实现的思想,使之同时具有边缘保持、快速滤波和噪声去
除的理想效果。 相似文献
36.
Abstract— The yield criterion is interpreted as defining the metric of the stress space. Hydrostatic stresses correspond to null geodesies. The plastic strain increment represents a normal projection of the increment undergone by a certain scalar function (hardening function) which depends only on the distance between stress points. This establishes a flow rule formally equivalent to the Prandtl-Reuss equations. Consideration of un-loading processes leads to the analysis of equivalent paths and to the definition of a generalized length or separation which provides a new representation of kinematic hardening. 相似文献
37.
线加权余量法及其在正交异性板弯曲分析中的应用 总被引:2,自引:1,他引:1
利用有限差分法对控制方程和边界条件进行半离散化,使其定义在一些离散线上,然后采用加权余量法求解。这就是本文提出的线加权余量法,也可称之为有限差分-加权余量分维耦合法。文中以正交各向异性薄板弯曲平衡问题为例推导了有关具体算式,给出了数值算例,说明了本文方法的有效性。 相似文献
38.
Melt index is considered an important quality variable determining product specifications. Reliable prediction of melt index (MI) is crucial in quality control of practical propylene polymerization processes. In this paper a least squares support vector machines (LS‐SVM) soft‐sensor model of propylene polymerization process is developed to infer the MI of polypropylene from other process variables. Considering the use of a SSE cost function without regularization might lead to less robust estimates; the weighted least squares support vector machines (weighted LS‐SVM) approach of propylene polymerization process is further proposed to obtain a robust estimation of melt index. The performance of standard SVM model is taken as a basis of comparison. A detailed comparison research among the standard SVM, LS‐SVM, and weighted LS‐SVM models is carried out. The research results confirm the effectiveness of the presented methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 285–289, 2006 相似文献
39.
40.
Preparation of nanocrystalline ZSM-5 has been proven possible with carbon matrix by using confined space synthesis. In combination with the hydrothermal method, by the use of a mesoporous carbon nanotube as the inert support material, ZSM-5 with SiO2/Al2O3 ratios of 100 was successfully synthesized with an average crystal size of 27 nm. Their structures were preliminarily characterized by x-ray power diffraction (XRPD) and infrared spectroscopy (IR), and scanning electron microscopy (SEM), respectively. At the same time, we put forward the mechanism about the confined space synthesis in terms of the results. 相似文献