全文获取类型
收费全文 | 161634篇 |
免费 | 17111篇 |
国内免费 | 11163篇 |
专业分类
电工技术 | 13040篇 |
技术理论 | 3篇 |
综合类 | 19910篇 |
化学工业 | 17141篇 |
金属工艺 | 6970篇 |
机械仪表 | 11473篇 |
建筑科学 | 19621篇 |
矿业工程 | 7795篇 |
能源动力 | 5464篇 |
轻工业 | 8554篇 |
水利工程 | 7446篇 |
石油天然气 | 8688篇 |
武器工业 | 2233篇 |
无线电 | 11181篇 |
一般工业技术 | 19912篇 |
冶金工业 | 6674篇 |
原子能技术 | 2368篇 |
自动化技术 | 21435篇 |
出版年
2024年 | 829篇 |
2023年 | 2304篇 |
2022年 | 4408篇 |
2021年 | 4952篇 |
2020年 | 5367篇 |
2019年 | 4591篇 |
2018年 | 4333篇 |
2017年 | 5355篇 |
2016年 | 6003篇 |
2015年 | 6180篇 |
2014年 | 9898篇 |
2013年 | 9334篇 |
2012年 | 12301篇 |
2011年 | 12483篇 |
2010年 | 9661篇 |
2009年 | 9955篇 |
2008年 | 9207篇 |
2007年 | 11300篇 |
2006年 | 9946篇 |
2005年 | 8396篇 |
2004年 | 6912篇 |
2003年 | 5937篇 |
2002年 | 4940篇 |
2001年 | 4165篇 |
2000年 | 3614篇 |
1999年 | 3167篇 |
1998年 | 2489篇 |
1997年 | 2186篇 |
1996年 | 1818篇 |
1995年 | 1626篇 |
1994年 | 1365篇 |
1993年 | 980篇 |
1992年 | 877篇 |
1991年 | 637篇 |
1990年 | 513篇 |
1989年 | 513篇 |
1988年 | 368篇 |
1987年 | 211篇 |
1986年 | 174篇 |
1985年 | 75篇 |
1984年 | 74篇 |
1983年 | 50篇 |
1982年 | 52篇 |
1981年 | 67篇 |
1980年 | 38篇 |
1979年 | 43篇 |
1978年 | 20篇 |
1977年 | 16篇 |
1975年 | 16篇 |
1959年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
对液压胀形轧辊(即国外的VC轧辊)辊套热装后的弹性变形进行了有限元分析,给出了确定油槽最小深度的计算公式。本文的有限元计算结果与实验结果吻合,某些结论可为液压胀形轧辊的结构设计提供理论依据。 相似文献
72.
Can a few seconds of high school teachers' nonverbal (NV) behavior predict students' ratings of these teachers (SRT)? Yes, but NV-SRT relations varied among various instructional situations. NV behaviors while administering the class and using the board were unrelated to SRT. Positive judgments of NV behavior while disciplining the class and interacting with students were positively related to SRT. NV behaviors in frontal teaching were negatively related to SRT. The most negative NV-SRT relations were found for teachers' differential NV behavior toward high- versus low-achieving students. Teacher differentiality and SRT have rarely been investigated in high school. The structure of SRT seems to differ between high school and college, and students' anger about teachers' differentiality strongly predicted their evaluations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
为了确保安全,核工业和其它一些工业要求某些参数的计算值只能取正的相对误差且不大于5×10-3,这是它们对数值计算的基本要求.例如,反应堆带功率运行时,功率增长总是随时间上升,功率曲线是向下凹的.传统的龙格-库塔法计算值总是小于真实值,并且随着时间的增加,计算值越来越小于真实值.按计算值分析,反应堆是安全的,但实际上反应堆是不安全的.这对反应堆的安全极为不利.为此,本文开拓了一个全新的数值计算方法.与龙格-库塔法相比,该方法计算工作量小,与预测一校正法相比,该方法没有启动问题.更值得指出的是计算值高于真实值,这样,反应堆计算结果总是偏于安全的. 相似文献
74.
本文通过焊接试验对奥氏体不锈钢绕带容器环板与绕带焊接工艺进行了研究分析,并得出了合理的焊接方法和工艺参数。 相似文献
75.
76.
Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
77.
本文给出一个结构不完全对称并联电网的等价定理,它把双输入双输出非线性耦合的微分方程组等价为单输入单输出的非线性微分方程,然后用渐近方法和谐波线性化方法求其一次近似解,得到一些新的物理性质,有助于合理选择电网结构,以提高其结构稳定性. 相似文献
78.
Maciej W. Rogoziski 《Systems & Control Letters》1989,12(5):449-453
An optimal predictor is developed for a singular random process generated by a known system driven by a white noise sequence. The properties of the predictor are compared with those of the optimal predictor for a nonsingular random process. 相似文献
79.
Power devices with high capability have been developed. 8‐kV/3.5‐kA‐class light‐triggered thyristors have the highest capability among power devices. These devices are used in the Kii Channel HVDC transmission system in Japan. In this paper, we report the extracted problems of conventional testing methods of 8‐kV/3.5‐kA‐class light‐triggered thyristors among manufacturers, and the proposed unified testing methods on the basis of element characteristics and operating conditions in the Kii Channel HVDC system. Furthermore, we propose a figure of merit for power devices for the practical use, and try to extract elements used at the Kii Channel HVDC system with small margins and low withstand capabilities. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 61–70, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10024 相似文献
80.
This paper presents a new approach for using stereo and motion correspondences to solve the problem of tracking multiple independently moving features. In this approach, quantitative relational structure (QRS) is proposed as a framework for the integration of stereo–motion correspondences. The similarity function, tightly coupled to stereo and motion cues, is constructed on QRS, and then energy function E2 consisting of the similarity function is defined. The tracking problem can be converted into the maximization problem of the energy function E2. The stereo and motion correspondences that maximize E2 are recovered by applying an extended graduated assignment algorithm. The relaxation labeling method is also presented for the comparison with the proposed method. Experimental results are presented to illustrate the performance of the proposed method. 相似文献