全文获取类型
收费全文 | 48986篇 |
免费 | 4255篇 |
国内免费 | 2848篇 |
专业分类
电工技术 | 5416篇 |
综合类 | 3381篇 |
化学工业 | 2896篇 |
金属工艺 | 2130篇 |
机械仪表 | 7388篇 |
建筑科学 | 2860篇 |
矿业工程 | 1369篇 |
能源动力 | 1516篇 |
轻工业 | 1090篇 |
水利工程 | 775篇 |
石油天然气 | 961篇 |
武器工业 | 771篇 |
无线电 | 6623篇 |
一般工业技术 | 5908篇 |
冶金工业 | 1720篇 |
原子能技术 | 941篇 |
自动化技术 | 10344篇 |
出版年
2024年 | 153篇 |
2023年 | 554篇 |
2022年 | 953篇 |
2021年 | 1137篇 |
2020年 | 1259篇 |
2019年 | 988篇 |
2018年 | 1018篇 |
2017年 | 1514篇 |
2016年 | 1697篇 |
2015年 | 1990篇 |
2014年 | 2897篇 |
2013年 | 2673篇 |
2012年 | 3280篇 |
2011年 | 3693篇 |
2010年 | 2651篇 |
2009年 | 2820篇 |
2008年 | 3009篇 |
2007年 | 3471篇 |
2006年 | 3113篇 |
2005年 | 2716篇 |
2004年 | 2334篇 |
2003年 | 2037篇 |
2002年 | 1634篇 |
2001年 | 1353篇 |
2000年 | 1199篇 |
1999年 | 1016篇 |
1998年 | 844篇 |
1997年 | 862篇 |
1996年 | 623篇 |
1995年 | 470篇 |
1994年 | 457篇 |
1993年 | 374篇 |
1992年 | 262篇 |
1991年 | 191篇 |
1990年 | 172篇 |
1989年 | 122篇 |
1988年 | 116篇 |
1987年 | 76篇 |
1986年 | 54篇 |
1985年 | 41篇 |
1984年 | 58篇 |
1983年 | 34篇 |
1982年 | 34篇 |
1981年 | 17篇 |
1979年 | 8篇 |
1977年 | 11篇 |
1973年 | 8篇 |
1959年 | 10篇 |
1956年 | 7篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
32.
一切测量结果都不可避免地具有不确定度,结合实际应用的情况,详细介绍了电子天平示值误差测量结果的不确定度评定方法。 相似文献
33.
34.
文章通过对时差式超声波流量检测方法的分析,提出了基于过零检测技术及积分法的信号处理方法,避免了繁琐的信号处理,降低了整机功耗。结合工作时序的设计,提出了实现低功耗超声波液体流量检测的措施。 相似文献
35.
以一种新的距离度量作为反馈的相关跟踪方法 总被引:5,自引:1,他引:4
基于相关的模板匹配方法在图像跟踪中得到了广泛的应用,但是这种方法的主要缺点是对图像噪声非常敏感,而且由这种方法得出的相关曲面比较平坦。为了有效抑制噪声和局部遮挡对图像的影响,提出用鲁棒统计中的一个值代替相关值作为距离度量。它不是计算两幅图像的对应像素差值,而是计算两幅图像中差别不大的对应像素对的个数。实验证明这样得到的曲面相对 收稿日期:2003 08 31; 修订日期:2003 10 28作者简介:张桂林(1944 ),男,天津人,教授,博士生导师,主要研究方向为自动识别、人体生物统计特征识别、图像处理算法与系统性能评估等。 要尖锐得多。当上述的距离度量应用于跟踪过程中时,模板的合理更新对跟踪非常重要。基于上述的距离度量方法,提出了一种新的模板更新策略。利用两幅图像中近似像素在整修匹配模板像素中所占的比例大小决定加权系数。这种加权策略可以自适应地根据图像序列的变化选择更新相关模板,同时在一定程度上减小模板漂移的危险。 相似文献
36.
The period and damping of the free motion of a body oscillating in a fluid depend on the fluid's viscosity and density. Commonly, a working equation which expresses the damping as a function of the viscosity and density is solved for the viscosity, the damping being measured and the density being treated as an independently supplied parameter. Another working equation exists for the period, and, in general, the period depends on a combination of the viscosity and the density which is linearly independent of the combination that appears in the damping equation. It is, therefore, in principle, possible to determine both the viscosity and the density by a simultaneous solution of the two coupled working equations, since the period also is measured. In this paper, the working equations that describe the oscillating-disk viscometer are reviewed and their simultaneous solution is considered. The effect of fixed plates symmetrically located above and below the oscillating disk is of specific interest. The paper's main result is that fixed plates can dramatically increase the independence of the damping and period working equations, so that it becomes indeed feasible to determine the viscosity and the density of a fluid simultaneously from the damping and period of oscillating motion. A price is paid, however, because the instrument's working equations when plates are present have multiple solutions. Under special conditions, these multiple solutions can coalesce, and then one can only deduce the viscosity from the damping equation if the density is known a priori. 相似文献
37.
M. J. O’Sullivan C. G. Walker M. L. O’Sullivan T. D. Thompson A. B. Philpott 《Telecommunication Systems》2006,33(4):353-376
The problem of designing fibre-optic networks for local-access telecommunications generates (at least) three non-trivial subproblems.
In the first of these subproblems one must determine how many fibre-optic cables (fibres) are required at either end of a
street. In the next subproblem a minimum-cost network must be designed to support the fibres. The network must also provide
distinct paths from either end of the street to the central exchange(s). Finally, the fibre-optic cables must be placed in
protective covers. These covers are available in a number of different sizes, allowing some flexibility when covering each
section of the network. In this paper we describe a dynamic programming (DP) formulation for finding a minimum-cost (protective)
covering for the network (the third of the subproblems). This problem is a generalised set covering problem with side constraints
and is further complicated by the introduction of fixed and variable welding costs. The DP formulation selects covers along
each arc (in the network), but cannot exactly model the fixed costs and so does not guarantee optimality. We also describe
an integer programming (IP) formulation for assessing the quality of the DP solutions. The cost of the networks constructed
by the IP model is less than those designed using the DP model, but the saving is not significant for the problems examined
(less than 0.1%). This indicates that the DP model will generally give very good solutions. Furthermore, as the problem dimensions
grow, DP gives significantly better solution times than IP. 相似文献
38.
39.
A new and original method of calibrating helium leaks that makes it possible to take into account the existence of a number of auxiliary phenomena is described. For this purpose, a hollow leak the purpose of which is to reproduce only desorbed gas flows, is introduced into the vacuum system of the calibration bench. Analysis of the results of corresponding cumulation measurements makes it possible to introduce corrections for these phenomena. 相似文献
40.
A method of measuring and identifying the static parameters of a bipolar transistor is considered. The characteristic of the transistor, from which the parameters of the model are determined, is chosen depending on what group the calculated parameters belong to. The characteristics are measured in such a way that the equations of the model describing them can be reduced to the simplest form. 相似文献