全文获取类型
收费全文 | 5857篇 |
免费 | 842篇 |
国内免费 | 435篇 |
专业分类
电工技术 | 130篇 |
技术理论 | 1篇 |
综合类 | 227篇 |
化学工业 | 1130篇 |
金属工艺 | 206篇 |
机械仪表 | 53篇 |
建筑科学 | 276篇 |
矿业工程 | 35篇 |
能源动力 | 215篇 |
轻工业 | 95篇 |
水利工程 | 77篇 |
石油天然气 | 150篇 |
武器工业 | 11篇 |
无线电 | 1039篇 |
一般工业技术 | 1241篇 |
冶金工业 | 75篇 |
原子能技术 | 51篇 |
自动化技术 | 2122篇 |
出版年
2024年 | 76篇 |
2023年 | 102篇 |
2022年 | 68篇 |
2021年 | 121篇 |
2020年 | 147篇 |
2019年 | 97篇 |
2018年 | 74篇 |
2017年 | 140篇 |
2016年 | 161篇 |
2015年 | 198篇 |
2014年 | 313篇 |
2013年 | 421篇 |
2012年 | 560篇 |
2011年 | 653篇 |
2010年 | 515篇 |
2009年 | 614篇 |
2008年 | 466篇 |
2007年 | 617篇 |
2006年 | 532篇 |
2005年 | 276篇 |
2004年 | 162篇 |
2003年 | 104篇 |
2002年 | 119篇 |
2001年 | 83篇 |
2000年 | 105篇 |
1999年 | 91篇 |
1998年 | 62篇 |
1997年 | 54篇 |
1996年 | 39篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 15篇 |
1987年 | 20篇 |
1986年 | 21篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1967年 | 7篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1964年 | 5篇 |
1963年 | 2篇 |
1962年 | 2篇 |
1961年 | 3篇 |
排序方式: 共有7134条查询结果,搜索用时 31 毫秒
1.
2.
《Engineering Analysis with Boundary Elements》2006,30(9):799-807
This paper describes a new method for direct numerical evaluation of multidimensional hypersingular integrals assigned on smooth curves and surfaces. These integrals arise when the boundary integral equations are used to solve problems of mechanics, electrodynamics, aerodynamics, etc. The hypersingular integrals are considered, in the sense of Hadamard, as finite parts. The main advantage of the proposed method is the numerical computation of the hypersingular integrals by the direct application of the developed cubature formulas, thus requiring little analytical pre-work. The method is not restricted to the type of problem however and may be easily applied to any hypersingular integrals. The convergence of the proposed technique has been proved and error estimates are given. An illustrative example demonstrates the accuracy and efficiency of the method. 相似文献
3.
《Diamond and Related Materials》2007,16(3):526-530
Vickers hardness of the cubic BC2N has been investigated using the microscopic hardness model, in which the parameters have been obtained using first principles calculations. Ionicities of the chemical bonds in the cubic BC2N depend on their surrounding chemical environments, which are included in the hardness calculations of the cubic BC2N using the population ionicity scale. For the four selected configurations of the cubic BC2N, the theoretical Vickers hardness has been found to lie between 70 and 72 GPa, consistent with the experimental value of 76 GPa. According to our calculations, it should be the cubic BC2N that ranks second among the superhard materials instead of the cubic BN. 相似文献
4.
In this paper, genetic algorithm is used to help improve the tolerance of feedforward neural networks against an open fault. The proposed method does not explicitly add any redundancy to the network, nor does it modify the training algorithm. Experiments show that it may profit the fault tolerance as well as the generalisation ability of neural networks. 相似文献
5.
《Intermetallics》2007,15(12):1497-1503
The coherent precipitate γ1-Ti4Nb3Al9 in the Nb-modified TiAl-based intermetallic compound with a nominal composition of Ti–48 at% Al–10 at% Nb was investigated by transmission electron microscopy. The crystallographic and morphologic characteristics of the precipitating phase have been calculated based on invariant line theory. It is revealed that in the γ-TiAl(Nb)/γ1-Ti4Nb3Al9 couples, both the morphological and crystallographical characteristics of the precipitate γ1-Ti4Nb3Al9 could be predicted by the three-dimensional phase transformation invariant line model. The needle direction of [001] at the early stage for coherent precipitate γ1-Ti4Nb3Al9 and [111] for equilibrium phase γ1-Ti4Nb3Al9 have both been explained well. The characterization of morphology and crystallography of the precipitate reaction in γ-TiAl/γ1-Ti4Nb3Al9 system sustain the postulate that precipitates are bounded by unrotated planes (eigenplanes) when three real eigenvalues exist. 相似文献
6.
针对农村生活污水直接排放已经成为影响我国农村水环境质量主要因素之一的现状,从适合我国农村的以村落或居民点为单位进行生活污水分散式处理的思维入手,介绍了我国现今主要的分散式生活污水处理技术的原理、特点、不足及其应用现状;继而综合比较了这些技术的技术经济指标,提出了适合我国农村的分散式生活污水处理技术的设计原则;最后提出发展有较高水力负荷,并具备小规模设备化特征和多种生物处理单元复合的创新技术是我国农村生活污水处理技术发展的主要方向。 相似文献
7.
决策模型组装是智能决策系统中的重要功能。基于本体的决策模型组装在模型之间的匹配上提供了丰富的语义信息,但本体推理的效率造成的响应速度较慢依然是需要解决的问题。本文提出一种基于方案本体的决策模型组装方法,可有效地减少本体建模的复杂度,并设计了相应的算法实现这种方法。 相似文献
8.
Jiang Lei Ding Yang Xue Xialin Zhou Sensen Li Cheng Zhang Xiaoke Jiang Xiqun 《Nano Research》2018,11(11):6062-6073
Nano Research - Developing multifunctional nanoparticles to support new therapy models is a promising and challenging task to address the current dilemma on antitumor treatment. Herein, we... 相似文献
9.
文章针对美国一流大学的计算机组成与系统结构实验课程进行研究,重点介绍UC Berkeley,MIT,Stanford University,CMU相关实验课程的内容和特色,为我国大学计算机组成与系统结构实验课程今后的改革与发展提供参考。 相似文献
10.
Segmenting center of interests (COIs) from pictures is an important but highly challenging problem for researchers in computer vision and image processing. The capability of understanding the meanings of pictures by computers can lead to breakthroughs in a wide range of applications including Web image search and online picture-sharing communities. In this paper, a two-level strategy is presented, which consists of a rough segmentation stage and a fine segmentation stage. In the first level, a picture is partitioned into four regions by using a block clustering method based on color and texture features, and the COI within the picture is distinguished from the background according to the principles of photographic composition. This stage aims to determine the approximate region of the target. In the second level, a novel active contour model is established based on shape information and vector method, where the image energy is defined by a hue gradient and the external energy is generated from either a triangular inner force or a supplementary force. This stage tries to extract the boundary of the target accurately. Experimental results on photos downloaded from the Internet show the feasibility and effectiveness of the proposed method. 相似文献