全文获取类型
收费全文 | 23574篇 |
免费 | 4197篇 |
国内免费 | 3047篇 |
专业分类
电工技术 | 4296篇 |
综合类 | 3365篇 |
化学工业 | 607篇 |
金属工艺 | 389篇 |
机械仪表 | 1850篇 |
建筑科学 | 394篇 |
矿业工程 | 461篇 |
能源动力 | 436篇 |
轻工业 | 448篇 |
水利工程 | 305篇 |
石油天然气 | 333篇 |
武器工业 | 312篇 |
无线电 | 3102篇 |
一般工业技术 | 1363篇 |
冶金工业 | 200篇 |
原子能技术 | 64篇 |
自动化技术 | 12893篇 |
出版年
2024年 | 191篇 |
2023年 | 538篇 |
2022年 | 956篇 |
2021年 | 991篇 |
2020年 | 828篇 |
2019年 | 763篇 |
2018年 | 728篇 |
2017年 | 896篇 |
2016年 | 1052篇 |
2015年 | 1221篇 |
2014年 | 1562篇 |
2013年 | 1478篇 |
2012年 | 2075篇 |
2011年 | 2149篇 |
2010年 | 1735篇 |
2009年 | 1820篇 |
2008年 | 1846篇 |
2007年 | 1994篇 |
2006年 | 1679篇 |
2005年 | 1300篇 |
2004年 | 926篇 |
2003年 | 731篇 |
2002年 | 561篇 |
2001年 | 450篇 |
2000年 | 403篇 |
1999年 | 307篇 |
1998年 | 230篇 |
1997年 | 238篇 |
1996年 | 183篇 |
1995年 | 169篇 |
1994年 | 142篇 |
1993年 | 110篇 |
1992年 | 102篇 |
1991年 | 78篇 |
1990年 | 85篇 |
1989年 | 68篇 |
1988年 | 59篇 |
1987年 | 20篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1984年 | 24篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
GIS中矢量图形的结构分析与VC++中的实现 总被引:2,自引:0,他引:2
简要讨论了GIS各类矢量图形元素间的空间拓朴结构及基位置关系 ,并用VC 6 . 0及MFC具体分析了圆弧与多边形区域的相交关系及实现。为利用VC开发专用图形软件提供了有用帮助。 相似文献
42.
We propose an efficient scheme for camera motion characterization in MPEG‐compressed video. The proposed scheme detects six types of basic camera motions through threshold‐based qualitative interpretation, in which fixed thresholds are applied to motion model parameters estimated from MPEG motion vectors (MVs). The efficiency and robustness of the scheme are validated by the experiment with real compressed video sequences. 相似文献
43.
Sixiong Han Yasuaki Ichikawa 《International journal for numerical methods in engineering》1995,38(24):4081-4100
In this paper, a mathematical model is proposed for the problem of the scattering of plane waves in a three-dimensional cracked materials. Instead of obtaining closed-form solutions as in conventional theoretical analysis methods, this approach, called the Equivalent Nodal Force (ENF) method formulates the mechanical effects of cracks as an equivalent nodal force in a numerical procedure, and physically translates cracked material into an equivalent continuous one. Several mechanical relations between waves and cracks are evident from this method. Also the results of several numerical calculations are presented and these are compared with those obtained by the conventional methods. 相似文献
44.
A new method for computing the node-pair reliability of network systems modeled by random graphs with nodes arranged in sequence is presented. It is based on a recursive algorithm using the “sliding window” technique, the window being composed of several consecutive nodes. In a single step, the connectivity probabilities for all nodes included in the window are found. Subsequently, the window is moved one node forward. This process is repeated until, in the last step, the window reaches the terminal node. The connectivity probabilities found at that point are used to compute the node-pair reliability of the network system considered. The algorithm is designed especially for graphs with small distances between adjacent nodes, where the distance between two nodes is defined as the absolute value of the difference between the nodes’ numbers. The maximal distance between any two adjacent nodes is denoted by Γ(G), where G symbolizes a random graph. If Γ(G)=2 then the method can be applied for directed as well as undirected graphs whose nodes and edges are subject to failure. This is important in view of the fact that many algorithms computing network reliability are designed for graphs with failure-prone edges and reliable nodes. If Γ(G)=3 then the method's applicability is limited to undirected graphs with reliable nodes. The main asset of the presented algorithms is their low numerical complexity—O(n), where n denotes the number of nodes. 相似文献
45.
Stanley C. Ahalt Prakoon Chen Cheng-Taou Chou Tzyy-Ping Jung 《The Journal of supercomputing》1992,5(4):307-330
We describe an implementation of a vector quantization codebook design algorithm based on the frequencysensitive competitive learning artificial neural network. The implementation, designed for use on high-performance computers, employs both multitasking and vectorization techniques. A C version of the algorithm tested on a CRAY Y-MP8/864 is discussed. We show how the implementation can be used to perform vector quantization, and demonstrate its use in compressing digital video image data. Two images are used, with various size codebooks, to test the performance of the implementation. The results show that the supercomputer techniques employed have significantly decreased the total execution time without affecting vector quantization performance.This work was supported by a Cray University Research Award and by NASA Lewis research grant number NAG3-1164. 相似文献
46.
RLL码的计算机辅助设计 总被引:1,自引:1,他引:0
本文着重讨论计算机辅助设计RLL码的具体实现问题.该过程首先根据RLL码两个参数d,k确定一个编码率p/q,然后构造出RLL码的高阶状态转换-输出符号矩阵并求相应的近似特征向量.最后通过状态分裂和状态归并过程,即可得到一个满足d,k约束的编码输出表.其中状态转换-输出符号矩阵为实现计算机辅助设计RLL码提供了有效的数据结构,而且要优化RLL码编码器,就必须有选择地进行状态分裂. 相似文献
47.
48.
49.
50.
在异步电动机磁场定向数学模型的基础上,给出了恒磁条件下异步电动机的解耦模型及传动系统的线性状态方程,并提出了重构负载扰动转矩的线性状态观测器。利用重构的负载转矩在矢量控制系统中进行扰动前馈,明显地提高了系统的抗负载扰动能力,从而为进一步提高矢量控制系统的动态性能开辟了一条有效的途径。 相似文献