全文获取类型
收费全文 | 22803篇 |
免费 | 1215篇 |
国内免费 | 1322篇 |
专业分类
电工技术 | 1101篇 |
技术理论 | 4篇 |
综合类 | 1706篇 |
化学工业 | 714篇 |
金属工艺 | 584篇 |
机械仪表 | 2680篇 |
建筑科学 | 1869篇 |
矿业工程 | 620篇 |
能源动力 | 871篇 |
轻工业 | 323篇 |
水利工程 | 280篇 |
石油天然气 | 418篇 |
武器工业 | 182篇 |
无线电 | 2137篇 |
一般工业技术 | 804篇 |
冶金工业 | 597篇 |
原子能技术 | 240篇 |
自动化技术 | 10210篇 |
出版年
2024年 | 18篇 |
2023年 | 92篇 |
2022年 | 203篇 |
2021年 | 283篇 |
2020年 | 296篇 |
2019年 | 201篇 |
2018年 | 248篇 |
2017年 | 300篇 |
2016年 | 375篇 |
2015年 | 518篇 |
2014年 | 1199篇 |
2013年 | 1063篇 |
2012年 | 1414篇 |
2011年 | 1914篇 |
2010年 | 1403篇 |
2009年 | 1267篇 |
2008年 | 1447篇 |
2007年 | 1731篇 |
2006年 | 1679篇 |
2005年 | 1536篇 |
2004年 | 1287篇 |
2003年 | 1274篇 |
2002年 | 1108篇 |
2001年 | 780篇 |
2000年 | 628篇 |
1999年 | 587篇 |
1998年 | 486篇 |
1997年 | 390篇 |
1996年 | 325篇 |
1995年 | 266篇 |
1994年 | 191篇 |
1993年 | 182篇 |
1992年 | 150篇 |
1991年 | 116篇 |
1990年 | 65篇 |
1989年 | 76篇 |
1988年 | 57篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 25篇 |
1983年 | 25篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1974年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
针对中小型企业销售管理的现状,利用J2EE架构技术设计了面向中小型企业的销售管理信息系统,该系统具有良好的跨平台性和可移植性,并且经过测试运行,达到了预期的效果。 相似文献
72.
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
73.
This paper investigates the two-stage stepwise identification for a class of nonlinear dynamic systems that can be described by linear-in-the-parameters models, and the model has to be built from a very large pool of basis functions or model terms. The main objective is to improve the compactness of the model that is obtained by the forward stepwise methods, while retaining the computational efficiency. The proposed algorithm first generates an initial model using a forward stepwise procedure. The significance of each selected term is then reviewed at the second stage and all insignificant ones are replaced, resulting in an optimised compact model with significantly improved performance. The main contribution of this paper is that these two stages are performed within a well-defined regression context, leading to significantly reduced computational complexity. The efficiency of the algorithm is confirmed by the computational complexity analysis, and its effectiveness is demonstrated by the simulation results. 相似文献
74.
企业网络信息管理系统的总体设计 总被引:1,自引:0,他引:1
介绍了企业网络信息管理系统总体设计方案,提出了软、硬件的设计方案和实现方法。该系统可以实时掌握控制各职能部门的运营状况,有效地调配企业资源,提高企业的市场竞争能力。 相似文献
75.
Open window buses without air-conditioning are a major mode of urban and inter-city transport in most countries. High occupancy
combined with hot and humid conditions makes travel in these buses quite uncomfortable. In this study air flow through a bus
has been studied that could be the basis for low cost and eco-friendly methods of increasing passenger comfort and possibly
reduce drag. The aerodynamics of such a road vehicle has not been studied as previous investigations have been confined to
vehicles with closed windows that present a smooth exterior to air flow. Using a 1:25 scaled Perspex model of an urban bus
in Delhi, flow visualization was performed in a water channel. The Reynolds numbers were one-tenth of a real bus moving at
10 m/s. Smoke and tuft visualizations were also performed on an urban bus at 40 km/h. Numerical simulations were performed
at the actual Reynolds number. Even though there were Reynolds number differences, the broad features were similar. Air enters
the bus from the rear windows, moves to the front (relative to the bus) and exits from the front windows. Inside air velocity
relative to the bus is about one-tenth of the free-stream velocity. The flow is highly three-dimensional and unsteady. 相似文献
76.
本文分析了造成ora-01555错误的原因,并提出解决办法。ora-01555错误一直是DBA与developer争论的焦点,解决其问题应是双方协调的结果。 相似文献
77.
鉴于目前电信的声讯系统中竞争的激烈性,它们急需要提高自身的系统集成度及高可用性,保证以最小的投资获得最丰厚的回报,由此出现了CompactPCI的系列产品,它不仅可以大大提高系统的集成度,同时对于系统的高可用性也进行了充分的考虑。本文将就声讯系统中基于CompactPCI的应用进行分析。 相似文献
78.
L. K. Isaev 《Measurement Techniques》2007,50(11):1214-1217
The main prerequisites are considered in a historical aspect and steps ate taken in creating a world-wide metrology system
with the aim of providing conditions for the mutual recognition of measurement results.
__________
Translated from Izmeritel’naya Tekhnika, No. 11. pp. 59–62, November, 2007. 相似文献
79.
一种数字电视条件接收系统的设计与实现 总被引:2,自引:2,他引:0
为支撑业务的安全开展,有线数字电视系统需提供一个安全可靠的加密系统,即条件接收系统。条件接收系统是对数字电视节目进行加密,以实现有线电视运营商对用户进行管理和收费。本文介绍了一种数字电视系统中的条件接收系统实现方案。 相似文献
80.
随着广播电视技术的不断发展 ,模拟信号传输向数字信号传输的转换已成为必然。介绍模数转换系统中放大器的性能、关键技术 ,并就放大器的选择作详细探讨。 相似文献