全文获取类型
收费全文 | 7563篇 |
免费 | 1465篇 |
国内免费 | 950篇 |
专业分类
电工技术 | 871篇 |
综合类 | 1102篇 |
化学工业 | 481篇 |
金属工艺 | 153篇 |
机械仪表 | 395篇 |
建筑科学 | 386篇 |
矿业工程 | 143篇 |
能源动力 | 199篇 |
轻工业 | 188篇 |
水利工程 | 262篇 |
石油天然气 | 250篇 |
武器工业 | 79篇 |
无线电 | 1223篇 |
一般工业技术 | 1029篇 |
冶金工业 | 160篇 |
原子能技术 | 57篇 |
自动化技术 | 3000篇 |
出版年
2024年 | 37篇 |
2023年 | 156篇 |
2022年 | 251篇 |
2021年 | 324篇 |
2020年 | 392篇 |
2019年 | 374篇 |
2018年 | 333篇 |
2017年 | 383篇 |
2016年 | 457篇 |
2015年 | 451篇 |
2014年 | 585篇 |
2013年 | 641篇 |
2012年 | 728篇 |
2011年 | 656篇 |
2010年 | 502篇 |
2009年 | 483篇 |
2008年 | 431篇 |
2007年 | 479篇 |
2006年 | 388篇 |
2005年 | 326篇 |
2004年 | 274篇 |
2003年 | 214篇 |
2002年 | 176篇 |
2001年 | 153篇 |
2000年 | 112篇 |
1999年 | 103篇 |
1998年 | 80篇 |
1997年 | 88篇 |
1996年 | 53篇 |
1995年 | 47篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 34篇 |
1991年 | 32篇 |
1990年 | 32篇 |
1989年 | 25篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1980年 | 2篇 |
1964年 | 3篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1957年 | 3篇 |
1956年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有9978条查询结果,搜索用时 31 毫秒
11.
Seog Geun Kang 《ETRI Journal》2006,28(2):235-238
In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR. 相似文献
12.
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
13.
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
14.
本文对多信道光纤环形网络结构进行了详细分析,推导出环网内平均路经长度和最大直径计算公式,并分析了最佳多信道光纤环网结构。 相似文献
15.
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
16.
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
17.
18.
主要探讨了以理论推算为主,根据物料成分建立不同配比方案,再以实践累积经验为辅组建系统配料方案。此系统方案的建立,克服了烧结原料品种变换频繁带来的质量波动,稳定了混匀料和烧结矿的化学成分。 相似文献
19.
P. I. Stetsyuk 《Cybernetics and Systems Analysis》2006,42(1):54-64
New quadratic models are proposed to improve the upper-bound estimates in the maximum weighted cut problem. They are found
by two original methods for deriving redundant quadratic constraints. A well-known linear model is shown to follow from the
models proposed. Recommendations on how to develop its strengthened analogs are given.
This study is partially sponsored from the grant UM2-2574-KV-03 (CRDF Cooperative Grants Program).
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 1, pp. 63—75, January–February 2006. 相似文献
20.
Biases in social comparative judgments, such as those illustrated by above-average and comparative-optimism effects, are often regarded as products of motivated reasoning (e.g., self-enhancement). These effects, however, can also be produced by information-processing limitations or aspects of judgment processes that are not necessarily biased by motivational factors. In this article, the authors briefly review motivational accounts of biased comparative judgments, introduce a 3-stage model for understanding how people make comparative judgments, and then describe how various nonmotivational factors can influence the 3 stages of the comparative judgment process. Finally, the authors discuss several unresolved issues highlighted by their analysis, such as the interrelation between motivated and nonmotivated sources of bias and the influence of nonmotivated sources of bias on behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献