全文获取类型
收费全文 | 75076篇 |
免费 | 7633篇 |
国内免费 | 4651篇 |
专业分类
电工技术 | 8200篇 |
技术理论 | 4篇 |
综合类 | 6917篇 |
化学工业 | 5081篇 |
金属工艺 | 3494篇 |
机械仪表 | 6307篇 |
建筑科学 | 12936篇 |
矿业工程 | 3209篇 |
能源动力 | 2154篇 |
轻工业 | 3578篇 |
水利工程 | 3877篇 |
石油天然气 | 4524篇 |
武器工业 | 1810篇 |
无线电 | 5895篇 |
一般工业技术 | 5809篇 |
冶金工业 | 3197篇 |
原子能技术 | 711篇 |
自动化技术 | 9657篇 |
出版年
2024年 | 278篇 |
2023年 | 854篇 |
2022年 | 1825篇 |
2021年 | 2216篇 |
2020年 | 2665篇 |
2019年 | 1906篇 |
2018年 | 1840篇 |
2017年 | 2495篇 |
2016年 | 2726篇 |
2015年 | 3014篇 |
2014年 | 5045篇 |
2013年 | 4387篇 |
2012年 | 6014篇 |
2011年 | 6143篇 |
2010年 | 4647篇 |
2009年 | 4510篇 |
2008年 | 4135篇 |
2007年 | 5050篇 |
2006年 | 4545篇 |
2005年 | 4023篇 |
2004年 | 3305篇 |
2003年 | 2787篇 |
2002年 | 2350篇 |
2001年 | 2044篇 |
2000年 | 1607篇 |
1999年 | 1296篇 |
1998年 | 1030篇 |
1997年 | 804篇 |
1996年 | 768篇 |
1995年 | 622篇 |
1994年 | 491篇 |
1993年 | 334篇 |
1992年 | 304篇 |
1991年 | 195篇 |
1990年 | 174篇 |
1989年 | 143篇 |
1988年 | 99篇 |
1987年 | 61篇 |
1986年 | 55篇 |
1985年 | 32篇 |
1984年 | 30篇 |
1981年 | 22篇 |
1980年 | 66篇 |
1979年 | 49篇 |
1965年 | 26篇 |
1964年 | 34篇 |
1960年 | 23篇 |
1959年 | 32篇 |
1956年 | 30篇 |
1955年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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
82.
本文简单地回顾了提高VLSI测试效率所采用的一些手段,讨论了在ASIC测试问题研究中出现的一些新观点、新方法、新动向,以及所取得的成果。在此基础上,文章阐明了ASIC测试技术的发展方向,并着重论述了可望在未来得到发展的,针对ASIC的功能测试方法。 相似文献
83.
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
84.
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
85.
Pseudo-random testing techniques for mixed-signal circuits offer several advantages compared to explicit time-domain and frequency-domain test methods, especially in a BIST structure. To fully exploit these advantages a suitable choice of the pseudo-random input parameters should be done and an investigation on the accuracy of the circuit response samples needed to reduce the risk of misclassification should be carried out. Here these issues have been addressed for a testing scheme based on the estimation of the impulse response of the device under test (DUT) by means of input-output cross-correlation. Moreover, new acceptance criteria for the DUT are suggested which solve some ambiguity problems arising if the classification of the DUT as good or bad is based on a few samples of the cross-correlation function. Examples of application of the proposed techniques to real cases are also shown in order to assess the impact of the measurement system inaccuracies on the reliability of the test. 相似文献
86.
计算机在高炉鼓风机上的应用 总被引:1,自引:0,他引:1
本文介绍了捷克和斯洛伐克CKD公司的MARK工业控制计算机构成及其在高炉鼓风机控制系统中的应用,较详细地说明了高炉鼓风机的工艺控制思想。 相似文献
87.
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
88.
The cohesive model is used for the prediction of the crack path during stable crack extension in ductile materials. The problem of crack-path deviation is investigated by means of simulation of crack propagation in a round tensile bar. The respective phenomenon is known as cup-cone fracture. It is shown that the model is able to predict the failure mechanism, which consists of normal fracture in the center and combined normal/shear fracture in the so-called “shear lips” at the specimen’s rim. The damage evolution and crack path predicted by the model are presented. The effect of the normal and shear failure parameters on the crack-deflection point and several aspects of the finite element mesh are discussed. 相似文献
89.
Ozgur Sinanoglu Ismet Bayraktaroglu Alex Orailoglu 《Journal of Electronic Testing》2003,19(4):457-467
Parallel test application helps reduce the otherwise considerable test times in SOCs; yet its applicability is limited by average and peak power considerations. The typical test vector loading techniques result in frequent transitions in the scan chain, which in turn reflect into significant levels of circuit switching unnecessarily. Judicious utilization of logic in the scan chain can help reduce transitions while loading the test vector needed. The transitions embedded in both test stimuli and the responses are handled through scan chain modifications consisting of logic gate insertion between scan cells as well as inversion of capture paths. No performance degradation ensues as these modifications have no impact on functional execution. To reduce average and peak power, we herein propose computationally efficient schemes that identify the location and the type of logic to be inserted. The experimental results confirm the significant reductions in test power possible under the proposed scheme. 相似文献
90.
在非AWGN环境下,针对CW,AM,FM,OOK,PSK,QPSK,16QAM,FSK,MSK,SSB十种混合调制信号,对调制类型特征提取方法和自动识别算法进行了分析、综合、设计和计算机仿真。提出了梯层电平分析方法、频率瞬时信号分析、剔除载波的归一化能量分析、平方后信号的频谱分析、四次方后的信号频谱分析等方法。当SNR=10dB时,计算机仿真结果是正确识别率不低于95%,自动识别的平均处理时间为不超过10s。 相似文献