全文获取类型
收费全文 | 53415篇 |
免费 | 9173篇 |
国内免费 | 5687篇 |
学科分类
工业技术 | 68275篇 |
出版年
2024年 | 608篇 |
2023年 | 1656篇 |
2022年 | 2668篇 |
2021年 | 2901篇 |
2020年 | 2834篇 |
2019年 | 2142篇 |
2018年 | 1813篇 |
2017年 | 2335篇 |
2016年 | 2435篇 |
2015年 | 2784篇 |
2014年 | 4243篇 |
2013年 | 3645篇 |
2012年 | 4491篇 |
2011年 | 4689篇 |
2010年 | 3537篇 |
2009年 | 3495篇 |
2008年 | 3539篇 |
2007年 | 3779篇 |
2006年 | 3051篇 |
2005年 | 2574篇 |
2004年 | 1938篇 |
2003年 | 1601篇 |
2002年 | 1201篇 |
2001年 | 835篇 |
2000年 | 679篇 |
1999年 | 534篇 |
1998年 | 455篇 |
1997年 | 324篇 |
1996年 | 319篇 |
1995年 | 221篇 |
1994年 | 161篇 |
1993年 | 133篇 |
1992年 | 119篇 |
1991年 | 98篇 |
1990年 | 90篇 |
1989年 | 49篇 |
1988年 | 54篇 |
1987年 | 27篇 |
1986年 | 32篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
61.
成品油储罐内的腐蚀及防护 总被引:1,自引:0,他引:1
对成品油储罐内各部位腐蚀情况进行了介绍,说明了产生腐蚀的原因和腐蚀机理。介绍了油罐内防护技术,采用节点加固,降低边缘应力,可减缓油罐金属腐蚀速度;对选用油罐内防腐涂料的原则进行了阐述。 相似文献
62.
在简单介绍高程系统的基础上,对影响GPS高程精度的几何水准联测误差、卫星分布不对称、星历误差、多路径误差等因素逐一进行了分析,并提出了相应的改进措施。同时,还对高程拟合使用的稳健估计方法进行了探讨。 相似文献
63.
In a change detection paradigm, a target object in a natural scene either rotated in depth, was replaced by another object token, or remained the same. Change detection performance was reliably higher when a target postcue allowed participants to restrict retrieval and comparison processes to the target object (Experiment 1). Change detection performance remained excellent when the target object was not attended at change (Experiment 2) and when a concurrent verbal working memory load minimized the possibility of verbal encoding. (Experiment 3). Together, these data demonstrate that visual representations accumulate in memory from attended objects as the eyes and attention are oriented within a scene and that change blindness derives, at least in part, from retrieval and comparison failure. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
结合具体工程实例,进行了CFG复合地基作为一种高层建筑地基处理方法的研究,对加固机理和设计步骤作了阐述,并对加固效果进行了检测分析,可供类似工程地基处理作参考。 相似文献
65.
66.
67.
In this paper, a new real-time sensor system has been developed to detect chatter in milling operations. In the developed sensor system, a pattern recognition technique based on an unsupervised neural network using the adaptive resonance theory (ART) is adopted for detection of milling chatter. The features on the cutting force spectrum are fed into the sensor system to classify the milling process with or without chatter. The experimental results indicate that the proposed sensor system can accurately detect milling chatter regardless of the variation in cutting conditions. 相似文献
68.
Akira Ishizaki Kazuhiko Takasaki Shoji Shimomura Kouichi Masaki Kanji Kitazawa 《Electrical Engineering in Japan》1996,116(5):128-137
Although brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current. It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown. It has been confirmed not only by simulation but also experiment that the 2-phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy. 相似文献
69.
形态学边缘检测的新算法及其应用 总被引:3,自引:0,他引:3
刘岚岚 《红外与毫米波学报》1998,17(5):386-390
提出了一种基于数学形态学的边缘检测的所算法,该算法具有简便和灵活可编程控制等优点,比原来主算法更国完善,在实际应用中有着很好的前景,并给出了实验结果。 相似文献
70.
How to study drying shrinkage microcracking in cement-based materials using optical and scanning electron microscopy? 总被引:3,自引:0,他引:3
Three different ‘destructive’ microscopy methods were tested on their ability to show drying shrinkage microcracks on a specimen cross-section. The first two were methods in which the microcracks were impregnated with a fluorescent epoxy and examined with fluorescence microscopy. In one method, the impregnation was applied before making the cross-section and in the other after making the cross-section. In the third method, the sample was kept wet constantly and examined in an environmental scanning electron microscope (ESEM). It was concluded that the method in which the dried specimen was impregnated before making the cross-section was the most reliable method to record drying shrinkage microcracks. With this method, it was possible to impregnate the complete drying shrinkage microcrack pattern in the studied cement-based materials from the surface, and there was no risk of recording microcracks introduced by sample preparation. 相似文献