全文获取类型
收费全文 | 1901篇 |
免费 | 322篇 |
国内免费 | 287篇 |
专业分类
电工技术 | 73篇 |
综合类 | 230篇 |
化学工业 | 49篇 |
金属工艺 | 24篇 |
机械仪表 | 101篇 |
建筑科学 | 198篇 |
矿业工程 | 16篇 |
能源动力 | 16篇 |
轻工业 | 67篇 |
水利工程 | 13篇 |
石油天然气 | 11篇 |
武器工业 | 7篇 |
无线电 | 185篇 |
一般工业技术 | 130篇 |
冶金工业 | 66篇 |
原子能技术 | 9篇 |
自动化技术 | 1315篇 |
出版年
2024年 | 16篇 |
2023年 | 37篇 |
2022年 | 66篇 |
2021年 | 72篇 |
2020年 | 91篇 |
2019年 | 78篇 |
2018年 | 64篇 |
2017年 | 93篇 |
2016年 | 102篇 |
2015年 | 118篇 |
2014年 | 144篇 |
2013年 | 153篇 |
2012年 | 142篇 |
2011年 | 186篇 |
2010年 | 141篇 |
2009年 | 139篇 |
2008年 | 129篇 |
2007年 | 123篇 |
2006年 | 109篇 |
2005年 | 78篇 |
2004年 | 67篇 |
2003年 | 52篇 |
2002年 | 52篇 |
2001年 | 31篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 22篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2510条查询结果,搜索用时 31 毫秒
1.
When a mission arrives at a random time and lasts for a duration, it becomes an interesting problem to plan replacement policies according to the health condition and repair history of the operating unit, as the reliability is required at mission time and no replacement can be done preventively during the mission duration. From this viewpoint, this paper proposes that effective replacement policies should be collaborative ones gathering data from time of operations, mission durations, minimal repairs and maintenance triggering approaches. We firstly discuss replacement policies with time of operations and random arrival times of mission durations, model the policies and find optimum replacement times and mission durations to minimize the expected replacement cost rates analytically. Secondly, replacement policies with minimal repairs and mission durations are discussed in a similar analytical way. Furthermore, the maintenance triggering approaches, i.e., replacement first and last, are also considered into respective replacement policies. Numerical examples are illustrated when the arrival time of the mission has a gamma distribution and the failure time of the unit has a Weibull distribution. In addition, simple case illustrations of maintaining the production system in glass factories are given based on the assumed data. 相似文献
2.
We present a new algorithm,
called MCS-M,
for computing minimal triangulations of graphs.
Lex-BFS, a seminal algorithm for recognizing chordal graphs,
was the genesis for two other classical algorithms:
LEX M and MCS.
LEX M extends the fundamental concept used in Lex-BFS,
resulting in an algorithm that not only recognizes chordality,
but also computes a minimal triangulation of an arbitrary graph.
MCS simplifies the fundamental concept used in Lex-BFS,
resulting in a simpler algorithm for recognizing chordal graphs.
The new algorithm MCS-M combines
the extension of LEX M with the simplification of MCS,
achieving all the results of LEX M in the same time complexity. 相似文献
3.
Shannon’s entropy plays an important role in the context of information theory. Since this entropy is not applicable to a system which has survived for some units of time, the concept of residual entropy has been developed in the literature. Here we generalize the residual entropy by choosing a convex function ? with ?(1) = 0. In this paper, some orderings and aging properties have been defined in terms of the generalized residual entropy function and their properties have been studied. Quite a few results available in the literature have been generalized and some distributions (viz. uniform, exponential, Pareto, power series, finite range) have been characterized through the generalized residual entropy. 相似文献
4.
文章详细分析了静电产生的机理,指出积聚静电电荷的多少与材料的电阻率和介电常数有关。讨论了静电火灾发生的条件,指出静电火灾的发生具有隐蔽性、复杂性和突发性。但只要对其规律进行深入地研究,可以找到有效地防止静电火灾发生的办法。 相似文献
5.
Yan Wang 《Computer aided design》2007,39(3):179-189
Current solid and surface modeling methods based on Euclidean geometry in traditional computer aided design are not efficient in constructing a large number of atoms and particles. In this paper, we propose a periodic surface model for computer aided nano design such that geometry of atoms and molecules can be constructed parametrically. At the molecular scale, periodicity of the model allows thousands of particles to be built efficiently. At the meso scale, inherent porosity of the model represents natural morphology of polymer and macromolecule. Surface and volume operations are defined to support crystal and molecular model creation with loci and foci periodic surfaces. The ultimate goal is to enable computer assisted material and system design at atomic, molecular, and meso scales. 相似文献
6.
Evaluate the performance of a stochastic-flow network with cost attribute in terms of minimal cuts 总被引:2,自引:0,他引:2
This paper proposes a performance index to measure the quality level of a stochastic-flow network in which each node has a designated capacity, which will have different lower levels due to various partial and complete failures. The performance index is the probability that the maximum flow of the network equals the demand d without exceeding the budget b. A simple algorithm in terms of minimal cuts is first proposed to generate all upper boundary points for (d, b), and then the probability that the maximum flow is less than or equal to d can be calculated in terms of such points. The upper boundary point for (d, b) is a maximal vector representing the capacity of each arc such that the maximum flow of the network under the budget b is d. The performance index can be calculated by repeating the proposed algorithm to obtain all upper boundary point for (d−1, b). A benchmark example is shown to illustrate the solution procedure. 相似文献
7.
针对二进制分辨矩阵无法处理连续型数据,提出一种基于邻域的改进二进制分辨矩阵及其属性约简方法。实验结果表明,与先数据离散化,后属性约简的方法相比,利用文中方法提取出的特征属性的分类能力更高。 相似文献
8.
9.
A comparative study between dynamic adapted PSO and VNS for the vehicle routing problem with dynamic requests 总被引:1,自引:0,他引:1
Combinatorial optimization problems are usually modeled in a static fashion. In this kind of problems, all data are known in advance, i.e. before the optimization process has started. However, in practice, many problems are dynamic, and change while the optimization is in progress. For example, in the dynamic vehicle routing problem (DVRP), new orders arrive when the working day plan is in progress. In this case, routes must be reconfigured dynamically while executing the current simulation. The DVRP is an extension of a conventional routing problem, its main interest being the connection to many real word applications (repair services, courier mail services, dial-a-ride services, etc.). In this article, a DVRP is examined, and solving methods based on particle swarm optimization and variable neighborhood search paradigms are proposed. The performance of both approaches is evaluated using a new set of benchmarks that we introduce here as well as existing benchmarks in the literature. Finally, we measure the behavior of both methods in terms of dynamic adaptation. 相似文献
10.