全文获取类型
收费全文 | 66473篇 |
免费 | 12537篇 |
国内免费 | 9046篇 |
专业分类
电工技术 | 8225篇 |
技术理论 | 1篇 |
综合类 | 8563篇 |
化学工业 | 1355篇 |
金属工艺 | 1265篇 |
机械仪表 | 5212篇 |
建筑科学 | 1189篇 |
矿业工程 | 936篇 |
能源动力 | 1378篇 |
轻工业 | 677篇 |
水利工程 | 1090篇 |
石油天然气 | 774篇 |
武器工业 | 1188篇 |
无线电 | 12412篇 |
一般工业技术 | 4147篇 |
冶金工业 | 492篇 |
原子能技术 | 268篇 |
自动化技术 | 38884篇 |
出版年
2024年 | 538篇 |
2023年 | 1256篇 |
2022年 | 2365篇 |
2021年 | 2544篇 |
2020年 | 2820篇 |
2019年 | 2349篇 |
2018年 | 2344篇 |
2017年 | 2715篇 |
2016年 | 3134篇 |
2015年 | 3726篇 |
2014年 | 4842篇 |
2013年 | 4585篇 |
2012年 | 5794篇 |
2011年 | 6033篇 |
2010年 | 4926篇 |
2009年 | 5038篇 |
2008年 | 5312篇 |
2007年 | 5741篇 |
2006年 | 4505篇 |
2005年 | 3682篇 |
2004年 | 2967篇 |
2003年 | 2346篇 |
2002年 | 1736篇 |
2001年 | 1354篇 |
2000年 | 1157篇 |
1999年 | 903篇 |
1998年 | 725篇 |
1997年 | 577篇 |
1996年 | 445篇 |
1995年 | 313篇 |
1994年 | 270篇 |
1993年 | 198篇 |
1992年 | 194篇 |
1991年 | 96篇 |
1990年 | 128篇 |
1989年 | 85篇 |
1988年 | 59篇 |
1987年 | 22篇 |
1986年 | 33篇 |
1985年 | 34篇 |
1984年 | 24篇 |
1983年 | 22篇 |
1982年 | 24篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 9篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
变压器故障分为放电性故障和过热性故障两大类别,它们均会在变压器油中有所反映。本文通过对变压器油中主要气体的分析,判断变压器的故障类型。具体方法是:利用改进算法的BP网络和信息融合技术,以变压器油中五种主要特征气体作为神经网络的输入,以六种变压器状态作为相应的输出,通过加入动量因子,可以提高学习率系数,充分发挥改进算法的BP网络具有自适应学习能力的优势。仿真测试结果表明,本方法能够在较大范围内准确有效地进行变压器的故障诊断。 相似文献
132.
单薇 《计算机光盘软件与应用》2012,(2):174
图像处理是计算机常用技术之一,模糊算法的运用有助于提高图像处理的效果。传统图像处理存在诸多弊端,影响了用户获取信息的便捷性。本文分析了图像处理的基本操作内容,并阐述了模糊算法在图像处理流程中的运用,以进一步提升原始图像处理的效果。 相似文献
133.
针对未知环境中障碍物种类多样性和位置不确定性的特点,提出了基于约束点的路径规划方法。首先对机器人在未知环境中检测到的局部障碍物信息进行分类和几何特征属性描述,得其约束点信息,然后引入改进后的A*算法,将其搜索范围局限于约束点上,计算约束点的评价函数值后得到子目标点,机器人到达子目标点后,若陷入死区,则采取回溯路径策略,重新选择子目标点,否则根据该点所属的障碍物种类采取跨越或绕行避障策略,最后移动机器人在未知环境中顺利到达目标点。仿真研究说明本文提出的路径规划方法具有可行性和有效性。 相似文献
134.
This paper presents the analysis of a parallel formulation of depth-first search. At the heart of this parallel formulation is a dynamic work-distribution scheme that divides the work between different processors. The effectiveness of the parallel formulation is strongly influenced by the work-distribution scheme and the target architecture. We introduce the concept of isoefficiency function to characterize the effectiveness of different architectures and work-distribution schemes. Many researchers considered the ring architecture to be quite suitable for parallel depth-first search. Our analytical and experimental results show that hypercube and shared-memory architectures are significantly better. The analysis of previously known work-distribution schemes motivated the design of substantially improved schemes for ring and shared-memory architectures. In particular, we present a work-distribution algorithm that guarantees close to optimal performance on a shared-memory/-network-with-message-combining architecture (e.g. RP3). Much of the analysis presented in this paper is applicable to other parallel algorithms in which work is dynamically shared between different processors (e.g., parallel divide-and-conquer algorithms). The concept of isoefficiency is useful in characterizing the scalability of a variety of parallel algorithms.This work was supported by Army Research Office Grant No. DAAG29-84-K-0060 to the Artificial Intelligence Laboratory, and Office of Naval Research Grant N00014-86-K-0763 to the Computer Science Department at the University of Texas at Austin. 相似文献
135.
以文本类型教学资源为研究对象,在领域知识可拓信息网模型和CELTS-3的基础上,阐述了基于信息元的教学资源组织系统设计与实现过程,包括信息特征元数据描述框架、特征词获取、信息元距离度量、信息元匹配规则以及匹配算法等.该系统通过有限的信息元描述无限的资源,实现了教学资源的高效组织,支持学习过程中资源自动重组. 相似文献
136.
137.
Computing scattering rates of electrons and phonons stands at the core of studies of electron transport properties. In the high field regime, the interactions between all electron bands with all phonon bands need to be considered. This full band interaction implies a huge computational burden in calculating scattering rates. In this study, a new accelerated algorithm is presented for this task, which speeds up the computation by two orders of magnitude (100 times) and dramatically simplifies the coding. At the same time, it visually demonstrates the physical process of scattering more clearly. 相似文献
138.
A strengthened analysis of a local algorithm for the minimum dominating set problem in planar graphs
In recent years growing interest in local distributed algorithms has widely been observed. This results from their high resistance to errors and damage, as well as from their good performance, which is independent of the size of the network. A local deterministic distributed algorithm finding an approximation of a Minimum Dominating Set in planar graphs has been presented by Lenzen et al., and they proved that the algorithm returns a 130-approximation of the Minimum Dominating Set. In this article we will show that the algorithm is two times more effective than was previously assumed, and we prove that the algorithm by Lenzen et al. outputs a 52-approximation to a Minimum Dominating Set. Therefore the gap between the lower bound and the approximation ratio of the best yet local deterministic distributed algorithm is reduced by half. 相似文献
139.
Design and implementation of division algorithm is one of the most complicated problems in multi-precision arithmetic. Huang et al. [1] proposed an efficient multi-precision integer division algorithm, and experimentally showed that it is about three times faster than the most popular algorithms proposed by Knuth [2] and Smith [3]. This paper reports a bug in the algorithm of Huang et al. [1], and suggests the necessary corrections. The theoretical correctness proof of the proposed algorithm is also given. The resulting algorithm remains as fast as that of [1]. 相似文献
140.
《Expert systems with applications》2014,41(9):4475-4493
Hyper-heuristics are emerging methodologies that perform a search over the space of heuristics in an attempt to solve difficult computational optimization problems. We present a learning selection choice function based hyper-heuristic to solve multi-objective optimization problems. This high level approach controls and combines the strengths of three well-known multi-objective evolutionary algorithms (i.e. NSGAII, SPEA2 and MOGA), utilizing them as the low level heuristics. The performance of the proposed learning hyper-heuristic is investigated on the Walking Fish Group test suite which is a common benchmark for multi-objective optimization. Additionally, the proposed hyper-heuristic is applied to the vehicle crashworthiness design problem as a real-world multi-objective problem. The experimental results demonstrate the effectiveness of the hyper-heuristic approach when compared to the performance of each low level heuristic run on its own, as well as being compared to other approaches including an adaptive multi-method search, namely AMALGAM. 相似文献