全文获取类型
收费全文 | 44358篇 |
免费 | 5189篇 |
国内免费 | 4207篇 |
专业分类
电工技术 | 5283篇 |
技术理论 | 1篇 |
综合类 | 7208篇 |
化学工业 | 1361篇 |
金属工艺 | 978篇 |
机械仪表 | 3783篇 |
建筑科学 | 1751篇 |
矿业工程 | 1293篇 |
能源动力 | 1146篇 |
轻工业 | 840篇 |
水利工程 | 1314篇 |
石油天然气 | 871篇 |
武器工业 | 673篇 |
无线电 | 3157篇 |
一般工业技术 | 3002篇 |
冶金工业 | 640篇 |
原子能技术 | 112篇 |
自动化技术 | 20341篇 |
出版年
2024年 | 126篇 |
2023年 | 448篇 |
2022年 | 766篇 |
2021年 | 873篇 |
2020年 | 1142篇 |
2019年 | 1157篇 |
2018年 | 1041篇 |
2017年 | 1345篇 |
2016年 | 1535篇 |
2015年 | 1718篇 |
2014年 | 2524篇 |
2013年 | 3073篇 |
2012年 | 3069篇 |
2011年 | 3417篇 |
2010年 | 2600篇 |
2009年 | 2865篇 |
2008年 | 3026篇 |
2007年 | 3499篇 |
2006年 | 3142篇 |
2005年 | 2635篇 |
2004年 | 2130篇 |
2003年 | 1890篇 |
2002年 | 1594篇 |
2001年 | 1377篇 |
2000年 | 1200篇 |
1999年 | 986篇 |
1998年 | 800篇 |
1997年 | 657篇 |
1996年 | 553篇 |
1995年 | 469篇 |
1994年 | 409篇 |
1993年 | 297篇 |
1992年 | 272篇 |
1991年 | 204篇 |
1990年 | 148篇 |
1989年 | 166篇 |
1988年 | 120篇 |
1987年 | 72篇 |
1986年 | 57篇 |
1985年 | 41篇 |
1984年 | 56篇 |
1983年 | 41篇 |
1982年 | 40篇 |
1981年 | 26篇 |
1980年 | 26篇 |
1979年 | 31篇 |
1978年 | 11篇 |
1977年 | 25篇 |
1976年 | 16篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
本文利用模糊集理论,提出一种非确定环境的描述方法,并且针对机器人在该类环境中的避障轨迹规划,建立了相应的决策函数和规划策略,最后,给出在PC-386计算机上的仿真试验结果。 相似文献
102.
In this paper, a sensor system, called a fuzzy pulse discriminator, is developed to classify various discharge pulses in electrical discharge machining (EDM). The fuzzy rules of the pulse discriminator are obtained based on the features of the gap voltage and gap current between the tool workpiece. The membership functions of the fuzzy pulse discriminator are automatically synthesized by using genetic algorithms. The effectiveness of this approach is verified under different cutting parameters. 相似文献
103.
We present our machine learning system, that uses inductive logic programming techniques to learn how to identify transmembrane
domains from amino acid sequences. Our system facilitates the use of operators such as ‘contains’, that act on entire sequences,
rather than on individual elements of a sequence. The prediction accuracy of our new system is around 93%, and this compares
favourably with earlier results.
This work was carried out with the support of a research grant from ISIS, Fujitsu Laboratories. 相似文献
104.
This paper demonstrates how the problem of tracking targets, which appear as either straight or curved lines in two-dimensional display images (or data images) can be formulated in terms of a directed weighted graph model and how dynamic programming techniques can be efficiently applied to reach an optimal or sub-optimal solution. In general, track detection algorithms providing optimal solutions have good detective ability, but most of them suffer from the inability to detect discontinuous lines or to resolve efficiently pairs of crossing lines. A sub-optimal solution is provided that efficiently overcomes these weaknesses. We focus on modeling the track detection problem in terms of a graph, formulating fast sequential/parallel sub-optimal track detection algorithms and testing them on simulated data in order to show their detective ability. Moreover, we specify the conditions under which sub-optimal algorithms can perform at least as well as their corresponding optimal algorithms. This is significant for the track detection problem where fast, accurate and real-time detection is considered a necessity. 相似文献
105.
This paper formulates the pickup and delivery problem, also known as the dial-a-ride problem, as an integer program. Its polyhedral structure is explored and four classes of valid inequalities developed. The results of a branch-and-cut algorithm based on these constraints are presented. 相似文献
106.
107.
在对Sirius叠前深度偏移软件应用开发的基础上,分析讨论了Sirius 2D叠前深度偏移速度模型建立、层析成像及演、叠前深度偏移以及深度聚焦等技术环节的基本原理,并以莺歌海盆地某测线的处理为例,具体分析了Sirius 2D叠前深度偏移处理的流程、主要参数及时效.文中还分析讨论了莺歌海盆地中央“泥拱带”叠前深度偏移处理的地质效果.实践表明,莺歌海盆地广泛发育的与“泥拱模糊带”有关的构造各有其特殊性,只有通过3D叠前深度偏移处理才能从根本上解决“泥拱模糊带”的成像问题. 相似文献
108.
在基于单片机的智能化重力加速度测试仪中采用C语言编程简化了程序设计任务,对于汇编语言难于处理的浮点数运算及汉字打印输出可通过C语言编译器的内部库函数调用实现,介绍了一种专为8051系列单片机设计的C语言编译器Frankilin C51,它具有代码优化功能,能产生极高效率的机器码,并且提供了丰富的内部函数库。描述了C51函数库所支持的IEEE标准浮点数的内存格式以及采用sprintf()函数处理包括 相似文献
109.
多目标模糊全局优化设计方法和软件 总被引:2,自引:0,他引:2
分析了优化设计在土木工程中应用不够广泛的原因,由此提出了一个能用于工程设计的多目标模糊全局优化设计方法。介绍了按该方法研制的软件MFD的功能和性能,以及一个用该软件分析的拱坝体型设计实例。 相似文献
110.
J. Dingel 《Formal Aspects of Computing》2002,14(2):123-197
Parallel computers have not yet had the expected impact on mainstream computing. Parallelism adds a level of complexity to
the programming task that makes it very error-prone. Moreover, a large variety of very different parallel architectures exists.
Porting an implementation from one machine to another may require substantial changes. This paper addresses some of these
problems by developing a formal basis for the design of parallel programs in the form of a refinement calculus. The calculus
allows the stepwise formal derivation of an abstract, low-level implementation from a trusted, high-level specification. The
calculus thus helps structuring and documenting the development process. Portability is increased, because the introduction
of a machine-dependent feature can be located in the refinement tree. Development efforts above this point in the tree are
independent of that feature and are thus reusable. Moreover, the discovery of new, possibly more efficient solutions is facilitated.
Last but not least, programs are correct by construction, which obviates the need for difficult debugging. Our programming/specification
notation supports fair parallelism, shared-variable and message-passing concurrency, local variables and channels. The calculus
rests on a compositional trace semantics that treats shared-variable and message-passing concurrency uniformly. The refinement
relation combines a context-sensitive notion of trace inclusion and assumption-commitment reasoning to achieve compositionality.
The calculus straddles both concurrency paradigms, that is, a shared-variable program can be refined into a distributed, message-passing
program and vice versa.
Received July 2001 / Accepted in revised form May 2002 相似文献