全文获取类型
收费全文 | 38090篇 |
免费 | 4403篇 |
国内免费 | 3153篇 |
专业分类
电工技术 | 2771篇 |
技术理论 | 12篇 |
综合类 | 5336篇 |
化学工业 | 1444篇 |
金属工艺 | 696篇 |
机械仪表 | 1886篇 |
建筑科学 | 9558篇 |
矿业工程 | 741篇 |
能源动力 | 630篇 |
轻工业 | 1268篇 |
水利工程 | 731篇 |
石油天然气 | 1783篇 |
武器工业 | 348篇 |
无线电 | 4315篇 |
一般工业技术 | 2485篇 |
冶金工业 | 552篇 |
原子能技术 | 317篇 |
自动化技术 | 10773篇 |
出版年
2024年 | 135篇 |
2023年 | 442篇 |
2022年 | 871篇 |
2021年 | 961篇 |
2020年 | 1060篇 |
2019年 | 869篇 |
2018年 | 879篇 |
2017年 | 1082篇 |
2016年 | 1264篇 |
2015年 | 1479篇 |
2014年 | 2495篇 |
2013年 | 2184篇 |
2012年 | 2800篇 |
2011年 | 3153篇 |
2010年 | 2661篇 |
2009年 | 2677篇 |
2008年 | 2727篇 |
2007年 | 3062篇 |
2006年 | 2672篇 |
2005年 | 2133篇 |
2004年 | 1786篇 |
2003年 | 1438篇 |
2002年 | 1177篇 |
2001年 | 961篇 |
2000年 | 847篇 |
1999年 | 701篇 |
1998年 | 538篇 |
1997年 | 395篇 |
1996年 | 364篇 |
1995年 | 347篇 |
1994年 | 308篇 |
1993年 | 215篇 |
1992年 | 204篇 |
1991年 | 117篇 |
1990年 | 102篇 |
1989年 | 105篇 |
1988年 | 68篇 |
1987年 | 46篇 |
1986年 | 39篇 |
1985年 | 46篇 |
1984年 | 34篇 |
1983年 | 27篇 |
1982年 | 29篇 |
1981年 | 26篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 16篇 |
1975年 | 7篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
161.
塔里木盆地是经历了多个原型盆地发育演化的大型叠合盆地,具有多期构造运动,发育多个区域构造不整合面。通过对构造层序和主要构造不整合分布的研究,总体上可以将塔里木盆地划分为5个一级构造层序和13个二级构造层序;主要构造不整合显示出一定的分布特征,大体从隆起区、斜坡区和坳陷区,常由高角度不整合、微角度或平行不整合到整合接触带。高角度不整合带,对油气的分布、运聚成藏起着一定的促进作用和破坏作用。不整合的发育,可以成为油气侧向运移的良好通道;可以为油气提供良好的储集场所和空间;也可以使先期油气藏遭到破坏和封闭重建,发生二次成藏。阐明不整合界面的特征,可以对分析盆地演化、古隆起古地貌恢复提供有利的依据.对油气的运移、聚集、成藏研究有着重要的意义。 相似文献
162.
An Efficient Code-Based Voxel-Traversing Algorithm 总被引:3,自引:1,他引:2
The paper considers an efficient approach to traversing a uniformly-subdivided space pierced by a line segment. A voxel, as the basic constituent element of the uniformly subdivided space, is restricted to having the form of a cube. The algorithm works in two steps. In the first step, the so-called Bresenham voxels are identified and, by comparing their position codes, their type of connectivity is determined. To achieve the required connectivity between neighbouring voxels, the second step of the algorithm is applied to find the missing voxels. In this way, the algorithm efficiently switches between face-, edge- and vertex-connectivity. Although the algorithm works with oating-point precision, it is extremely computationally efficient, and tests of speed compared with the Müller, Cleary & Wyvill, Amanatides & Woo, and Zemčik algorithms are described. 相似文献
163.
阮芙英 《纺织高校基础科学学报》1995,8(1):91-95
现代光学和通讯理论由于引入了傅里叶变换的方法,使计算光学系统和通讯系统的物像的对应关系简洁、清晰。该文用傅氏变换计算长为2a、照度为A的均匀缝光源在观察面上的光强分布为I(x)=│E(x)│^2=AA^2a^2(sin2πfa/2πfa)此方法也可运用于矩形孔、圆孔等。 相似文献
164.
Automated techniques for satellite imagery navigation and co-location are especially required for environmental monitoring activities intensively using satellite data. In this work are presented the results obtained after 2 years of operational use of the Subpixel Automatic Navigation of AVHRR (SANA) scheme. An automatic method for accuracy assessment of satellite navigation techniques, which permits a preliminary evaluation of their performances, dealing with a large collection of test images is also proposed. The navigation accuracy assessment, performed by using a selection of small islands as reference points, is discussed.Results achieved over more than 400 Advanced Very-High-Resolution Radiometer (AVHRR) scenes confirm that the SANA scheme is a very accurate one (computed mean navigation error is generally about one AVHRR pixel). Furthermore, because of its high processing speed, it can be considered a suitable tool for intensive satellite data processing in multitemporal analyses, especially required for environmental studies as well as for operational monitoring purposes. 相似文献
165.
In this paper we show that finding solutions of a system of multivariate polynomial equalities and inequalities in the max algebra is equivalent to solving an Extended Linear Complementarity Problem. This allows us to find all solutions of such a system of multivariate polynomial equalities and inequalities and provides a geometrical insight in the structure of the solution set. We also demonstrate that this enables us to solve many important problems in the max algebra and the max-min-plus algebra such as matrix decompositions, construction of matrices with a given characteristic polynomial, state space transformations and the (minimal) state space realization problem.Research assistant with the N.F.W.O. (Belgian National Fund for Scientific Research).Senior research associate with the N.F.W.O. 相似文献
166.
Approximate string matching is used for spelling correction and personal name matching. In this paper we show how to use string matching techniques in conjunction with lexicon indexes to find approximate matches in a large lexicon. We test several lexicon indexing techniques, including n-grams and permuted lexicons, and several string matching techniques, including string similarity measures and phonetic coding. We propose methods for combining these techniques, and show experimentally that these combinations yield good retrieval effectiveness while keeping index size and retrieval time low. Our experiments also suggest that, in contrast to previous claims, phonetic codings are markedly inferior to string distance measures, which are demonstrated to be suitable for both spelling correction and personal name matching. 相似文献
167.
Aleksej G. Voloboj 《Computer Graphics Forum》1993,12(5):289-296
The paper describes the colour approximation problem and the method of dynamic palette construction is suggested for its solution. The method uses the graphic display palette based on the computed true colour of the individual picture. Some aspects of human colour perception are considered. Two metrics in colour space are introduced to estimate closeness of the suggested colour approximation. The method was applied to visualize 3D scenes generated by ray tracing. 相似文献
168.
On-Line Shape recognition with incremental training using binary synaptic weights algorithm 总被引:2,自引:0,他引:2
Recognition of hand drawn shapes is beneficial in drawing packages and automated sketch entry in handheld computers. In this paper, we propose a new approach to on-line geometric shape recognition with incremental training function, which utilizes a heuristic function to reduce noise and a neural network for classification and on-line training. Instead of recognizing segments of a drawing and then performing syntactical analysis to match with a predefined shape, which is weak in terms of generalization and dealing with noise, we examine the shape as a whole. The main concept of the recognition method is derived from the fact that internal angles are very important in the perceived shape of outlines. Our application's aim is to recognize elliptic, rectangular, and triangular shapes in a way similar to human cognition of these shapes. Human beings recognize such basic shapes regardless of the variations in size, noise on the shape border, rotation and in the case of triangles, regardless of the type of the triangle. The key concept is that the neural network learns the relationships between the internal angles of a shape and its classification, therefore only a few training samples which represent the class of the shape are sufficient. Fast meremental training, which is performed on-line, is accomplished by the use of the Binary Synaptic Weights algorithm, a one pass, feedforward neural network training algorithm. Incremental training offers the advantage of adjusting the recognition capability of the system to the user's drawings. the results are very successful, such that the neural network correctly classified shapes that did not have any resemblance to the shapes in the initial training set. 相似文献
169.
对天线方向图计算中涉及的最大副瓣电平的分析方法进行了探讨,提出了用方向图搜索求解最大副瓣电平;同时给出了用该方法求得在同相矩形口径两种分布形式下Intercardinal面上的最大副瓣电子平,并给出了Intercardinal面的定义。 相似文献
170.
宋晓东 《数码设计:surface》2012,(6):77-79
在消费社会的背景下,消费文化观念获得重要突破——"消费是一种体验",消费文化催生了现代商业空间环境的体验功能。本文归纳了在消费文化影响下体验型商业空间环境的特质,以案例为基础讨论了各类体验型商业空间环境的特点,并在设计理念的层面上对情境体验空间、主题体验空间、超现实体验空间的营造思路做出了探索。 相似文献