全文获取类型
收费全文 | 48367篇 |
免费 | 4410篇 |
国内免费 | 2557篇 |
专业分类
电工技术 | 9788篇 |
技术理论 | 1篇 |
综合类 | 3421篇 |
化学工业 | 2138篇 |
金属工艺 | 1470篇 |
机械仪表 | 6163篇 |
建筑科学 | 2499篇 |
矿业工程 | 1209篇 |
能源动力 | 2218篇 |
轻工业 | 931篇 |
水利工程 | 1222篇 |
石油天然气 | 835篇 |
武器工业 | 692篇 |
无线电 | 7693篇 |
一般工业技术 | 4861篇 |
冶金工业 | 1463篇 |
原子能技术 | 1241篇 |
自动化技术 | 7489篇 |
出版年
2024年 | 153篇 |
2023年 | 527篇 |
2022年 | 879篇 |
2021年 | 1108篇 |
2020年 | 1238篇 |
2019年 | 920篇 |
2018年 | 926篇 |
2017年 | 1479篇 |
2016年 | 1696篇 |
2015年 | 1875篇 |
2014年 | 2897篇 |
2013年 | 2501篇 |
2012年 | 3241篇 |
2011年 | 3690篇 |
2010年 | 2728篇 |
2009年 | 2739篇 |
2008年 | 2841篇 |
2007年 | 3275篇 |
2006年 | 3105篇 |
2005年 | 2976篇 |
2004年 | 2594篇 |
2003年 | 1997篇 |
2002年 | 1501篇 |
2001年 | 1276篇 |
2000年 | 1104篇 |
1999年 | 1000篇 |
1998年 | 848篇 |
1997年 | 849篇 |
1996年 | 669篇 |
1995年 | 524篇 |
1994年 | 491篇 |
1993年 | 410篇 |
1992年 | 284篇 |
1991年 | 199篇 |
1990年 | 163篇 |
1989年 | 112篇 |
1988年 | 108篇 |
1987年 | 68篇 |
1986年 | 43篇 |
1985年 | 40篇 |
1984年 | 61篇 |
1983年 | 26篇 |
1982年 | 30篇 |
1981年 | 14篇 |
1980年 | 15篇 |
1977年 | 10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 0 毫秒
31.
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
32.
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
33.
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
34.
面向应用的无线传感器网络 总被引:1,自引:0,他引:1
结合具体的应用环境分析了无线传感器网络发展到第二阶段需要考虑的重点问题;探讨了基于上述应用需求的无线传感器网络的协议栈结构和今后的研究方向。 相似文献
35.
37.
38.
P. G. Muzykov Y. I. Khlebnikov S. V. Regula Y. Gao T. S. Sudarshan 《Journal of Electronic Materials》2003,32(6):505-510
To establish fast, nondestructive, and inexpensive methods for resistivity measurements of SiC wafers, different resistivity-measurement
techniques were tested for characterization of semi-insulating SiC wafers, namely, the four-point probe method with removable
graphite contacts, the van der Pauw method with annealed metal and diffused contacts, the current-voltage (I-V) technique,
and the contactless resistivity-measurement method. Comparison of different techniques is presented. The resistivity values
of the semi-insulating SiC wafer measured using different techniques agree fairly well. As a result, application of removable
graphite contacts is proposed for fast and nondestructive resistivity measurement of SiC wafers using the four-point probe
method. High-temperature van der Pauw and room-temperature Hall characterization for the tested semi-insulating SiC wafer
was also obtained and reported in this work. 相似文献
39.
电力系统谐波检测的现状与发展 总被引:7,自引:0,他引:7
准确、实时地对电力系统谐波进行检测有着重要的意义。本文根据电力系统谐波测量的基本方法,对近年来电力系统谐波检测的新方法进行了分析和评述。最后对电力系统的谐波测量进行了总结并提出了看法。 相似文献
40.
通过对地杂波O.94μm激光后向反射率的测试,获取不同入射角的多背景后向反射率测试数据。通过对测试数据的分析处理提供特征信息,为激光探浏器设计提供依据。 相似文献