全文获取类型
收费全文 | 63643篇 |
免费 | 6881篇 |
国内免费 | 4043篇 |
专业分类
电工技术 | 5960篇 |
技术理论 | 3篇 |
综合类 | 5842篇 |
化学工业 | 4749篇 |
金属工艺 | 2828篇 |
机械仪表 | 4477篇 |
建筑科学 | 12480篇 |
矿业工程 | 2465篇 |
能源动力 | 1949篇 |
轻工业 | 3223篇 |
水利工程 | 3561篇 |
石油天然气 | 4095篇 |
武器工业 | 1429篇 |
无线电 | 4771篇 |
一般工业技术 | 6117篇 |
冶金工业 | 2481篇 |
原子能技术 | 728篇 |
自动化技术 | 7409篇 |
出版年
2024年 | 244篇 |
2023年 | 770篇 |
2022年 | 1625篇 |
2021年 | 1964篇 |
2020年 | 2282篇 |
2019年 | 1809篇 |
2018年 | 1721篇 |
2017年 | 2320篇 |
2016年 | 2505篇 |
2015年 | 2664篇 |
2014年 | 4098篇 |
2013年 | 3904篇 |
2012年 | 4910篇 |
2011年 | 5072篇 |
2010年 | 3883篇 |
2009年 | 3847篇 |
2008年 | 3474篇 |
2007年 | 4168篇 |
2006年 | 3762篇 |
2005年 | 3273篇 |
2004年 | 2752篇 |
2003年 | 2244篇 |
2002年 | 1936篇 |
2001年 | 1666篇 |
2000年 | 1350篇 |
1999年 | 1085篇 |
1998年 | 913篇 |
1997年 | 709篇 |
1996年 | 692篇 |
1995年 | 551篇 |
1994年 | 443篇 |
1993年 | 309篇 |
1992年 | 271篇 |
1991年 | 186篇 |
1990年 | 182篇 |
1989年 | 135篇 |
1988年 | 92篇 |
1987年 | 60篇 |
1986年 | 57篇 |
1985年 | 39篇 |
1984年 | 29篇 |
1980年 | 67篇 |
1979年 | 55篇 |
1965年 | 30篇 |
1964年 | 36篇 |
1960年 | 25篇 |
1959年 | 39篇 |
1956年 | 33篇 |
1955年 | 42篇 |
1954年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
52.
A method was developed to assess the heat insulation performance of intumescent coatings. The method consists of temperature measurements using the bench‐scaled experimental set‐up of a cone calorimeter and finite difference simulation to calculate the effective thermal conductivity dependent on time/temperature. This simulation procedure was also adapted to the small scale test furnace, in which the standard time–temperature curve is applied to a larger sample and thus which provides results relevant for approval. Investigations on temperature and calculated effective thermal conduction were performed on intumescent coatings in both experimental set‐ups using various coating thicknesses. The results correspond to each other as well as showing the limits of transferability between both fire tests. It is shown that bench‐scaled cone calorimeter tests are a valuable tool for assessing and predicting the performance of intumescent coatings in larger tests relevant for approval. The correlation fails for processes at surface temperatures above 750°C, which are not reached in the cone calorimeter, but are attained in the small scale furnace set‐up. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
53.
54.
55.
56.
介绍了一种用于冰箱检测的新型测试系统,并在WIN98环境下用VB6.0实现该系统软件。该系统可以同时对四台冰箱的温度参数及其中一台冰箱的耗电量进行检测,该系统具有成本低,性能稳定的优点。 相似文献
57.
钛合金的银脆,镉脆敏感性及其控制 总被引:4,自引:0,他引:4
利用慢应变速率拉伸技术(SSRT),并结合恒载实验,较全面地研究了Ti-6Al-4V合金的银脆行为、固态与液态镉脆行为,确定了应变速率、接触条件、热处理制度、试样取向、温度等因素对Ti-6Al-4V合金银脆与镉脆敏感性的影响,探讨了Ni阻挡层对控制Ti-6Al-4V合金和TC11合金银脆开裂的作用。 相似文献
58.
In this article we propose efficient scan path and BIST schemes for RAMs. Tools for automatic generation of these schemes have been implemented. They reduce the design effort and thus allow the designer to select the more appropriate scheme with respect to various constraints. 相似文献
59.
When a circuit is tested using random or pseudorandom patterns, it is essential to determine the amount of time (test length) required to test it adequately. We present a methodology for predicting different statistics of random pattern test length. While earlier methods allowed estimation only of upper bounds of test length and only for exhaustive fault coverage, the technique presented here is capable of providing estimates of all statistics of interest (including expected value and variance) for all coverage specifications.Our methodology is based on sampling models developed for fault coverage estimation [1]. Test length is viewed as awaiting time on fault coverage. Based on this relation we derive the distribution of test length as a function of fault coverage. Methods of approximating expected value and variance of test length are presented. Accuracy of these approximations can be controlled by the user. A practical technique for predicting expected test length is developed. This technique is based on clustering faults into equal detectability subsets. A simple and effective algorithm for fault clustering is also presented. The sampling model is applied to each cluster independently and the results are then aggregated to yield test lengths for the whole circuit. Results of experiments with several circuits (both ISCAS '85 benchmarks and other practical circuits) are also provided.This work was done while the author was with the Department of Electrical Engineering, Southern Illinois University, Carbondale, IL 62901. 相似文献
60.
In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1×1016 to 1×1017 ions/cm2 at maximum 150°C, using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the cerium ion implantation in the oxide films. Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a 1 N H2SO4 solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will declined with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed. 相似文献