全文获取类型
收费全文 | 23403篇 |
免费 | 624篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 294篇 |
综合类 | 11篇 |
化学工业 | 4231篇 |
金属工艺 | 338篇 |
机械仪表 | 456篇 |
建筑科学 | 1291篇 |
矿业工程 | 119篇 |
能源动力 | 620篇 |
轻工业 | 1755篇 |
水利工程 | 192篇 |
石油天然气 | 219篇 |
武器工业 | 1篇 |
无线电 | 1603篇 |
一般工业技术 | 3681篇 |
冶金工业 | 6010篇 |
原子能技术 | 238篇 |
自动化技术 | 2989篇 |
出版年
2022年 | 157篇 |
2021年 | 271篇 |
2020年 | 212篇 |
2019年 | 278篇 |
2018年 | 314篇 |
2017年 | 313篇 |
2016年 | 369篇 |
2015年 | 278篇 |
2014年 | 457篇 |
2013年 | 1314篇 |
2012年 | 754篇 |
2011年 | 1042篇 |
2010年 | 810篇 |
2009年 | 785篇 |
2008年 | 1034篇 |
2007年 | 1029篇 |
2006年 | 830篇 |
2005年 | 848篇 |
2004年 | 668篇 |
2003年 | 680篇 |
2002年 | 659篇 |
2001年 | 440篇 |
2000年 | 409篇 |
1999年 | 461篇 |
1998年 | 833篇 |
1997年 | 654篇 |
1996年 | 538篇 |
1995年 | 471篇 |
1994年 | 396篇 |
1993年 | 442篇 |
1992年 | 334篇 |
1991年 | 239篇 |
1990年 | 288篇 |
1989年 | 349篇 |
1988年 | 285篇 |
1987年 | 260篇 |
1986年 | 260篇 |
1985年 | 327篇 |
1984年 | 332篇 |
1983年 | 280篇 |
1982年 | 268篇 |
1981年 | 268篇 |
1980年 | 228篇 |
1979年 | 242篇 |
1978年 | 224篇 |
1977年 | 263篇 |
1976年 | 293篇 |
1975年 | 208篇 |
1974年 | 212篇 |
1973年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Results for optimizing an array of conducting polymer gas sensors for sensing one of five analytes in the presence of up to four interferents are presented. The optimized array consists of subarrays of homogeneous (like) sensors contributing to a larger heterogeneous array of up to ten points (unlike sensors) in multidimensional sensor space. The optimization techniques presented here are linear, since the polymer sensors in their useful (low concentration) operating range exhibit linear and additive response characteristics. The optimization of these arrays produces maximum separability between analytes, demonstrating the trade-off between the addition of both information and variability induced by increasing the size of the heterogeneous array. Optimization results for sensing acetone, hexane, THF, toluene, and ethanol in the presence of interferents result in array sizes that are significantly less than the maximum available number of sensors (ten in the heterogeneous partition of the array). This result adds fuel to the argument that fewer sensors are better; the argument for more sensors, however, is also made in the context of the electronic nose systems where significant chemical diversity is required. Homogeneous subarrays of up to four elements each improve the separability of analytes in these optimized heterogeneous arrays by over 10% and also effectively flag broken or unhealthy sensors in a manner that is independent of analyte and concentration. 相似文献
102.
Correction to Construction of Panoramic Image Mosaics with Global and Local Alignment 总被引:2,自引:1,他引:1
International Journal of Computer Vision - 相似文献
103.
104.
Samuel L. Manzello Richard G. Gann Scott R. Kukuck Kuldeep Prasad Walter W. Jones 《火与材料》2007,31(5):297-310
A gypsum wall assembly was exposed to an intense real‐scale compartment fire. For the wall assembly, temperatures were measured at the exposed face, within the stud cavity, and at the unexposed face during the fire exposure. Total heat flux gauges were used to measure the temporal variation of the energy incident on the walls, and cameras, both visual and infrared, were used to image the unexposed face of the wall assembly during the fire exposure. The behaviour of the wall assembly under the fire load is discussed as are current model results for a simulation of the fire test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
105.
Boesch Ronald D. Magin Richard L. Franke Stevenb J. 《IEEE transactions on bio-medical engineering》1987,(11):904-907
This paper describes a design for an analog phase shifter operating at 915 MHz and suitable for use in a phased array microwave hyperthermia system. Here, the major operating constraint was minimization of amplitude variation over a 1800 phase shift, whereas previous phase shifters were designed to obtain a linear relationship between phase and control voltage. The result is a simple, inexpensive hybrid coupler phase shifter that operates over a narrow bandwidth and provides 180°of continuous phase shift with input powers up to 1 W. 相似文献
106.
107.
The aim of this paper is to evaluate the use of trace diagrams for analysing collaborative problem solving. The paper describes a study where trace diagrams were used to analyse joint navigation in a virtual environment. Ten pairs of undergraduates worked together on a distributed virtual task to collect five flowers using two bees with each participant controlling one of the bees. This task is used extensively in research on multi-robot systems. The joint navigation of the pairs was analysed using trace diagrams. They showed that more successful pairs divided the task up, showed very little overlap and very little backtracking. Whereas, the less successful pairs, showed no task division, there was significant overlap and extensive backtracking. From this analysis we developed numerical measures of task division, overlap and backtracking. Task division was significantly and negatively related with task performance. Backtracking and overlap were significantly and positively correlated. 相似文献
108.
Michael Fox Richard Hastings Scott Lovald Juan Heinrich 《Journal of Failure Analysis and Prevention》2007,7(3):165-174
A failure analysis case study is presented for a two-piece aerosol containing tetrafluoroethane, commonly referred to as Refrigerant
134a. A gentleman was preparing to recharge the air conditioning system of an automobile when the bottom exploded off the
aerosol container, propelling the body of the aerosol container like a rocket, which hit the man in the eye and blinded him
in that eye. The aerosol was never connected to the air conditioner, therefore backpressure from the air conditioner (AC)
compressor was ruled out as a cause for the explosion. The objective of the study was to determine why the aerosol exploded.
Several recently developed test methods were used, including two types of heat-to-burst tests and a puncture chamber to measure
the pressure-versus-temperature behavior of aerosols. More common test methods were also used, such as water bath pressure
tests, hydro pressure burst tests, pneumatic pressure burst tests, hardness measurements, weight measurements, metallography,
scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an accident scenario recreation. A semi-empirical
correlation between the hardness and weights of the container bottoms was used to determine the explosion temperature and/or
pressure. This semi-empirical correlation agrees in principle with an analysis of the explosion pressures using finite-element
analysis (FEA). The root cause for the explosion was determined to be a lack of strength of the bottom of the two-piece aerosol
coupled with heating the aerosol to temperatures significantly above room temperature. 相似文献
109.
In the following paper at first general concepts which have to be considered for the accomplishment of a 3D fatigue crack propagation simulation by the FE‐method in real structures are introduced. In doing so numerical aspects concerning the necessary mesh generation as well as fracture mechanical issues will be discussed. Furthermore the 3D crack simulation program ADAPCRACK3D, which has been developed at the Institute of Applied Mechanics at University of Paderborn, is presented in its general functionality. The simulation example of the crack propagation in a shutter ring of a hydraulic press shows the practical relevance of both the implemented algorithms and fracture mechanical concepts. 相似文献
110.
Claude Robert Concepción S. Wilson Jean-François Gaudy Charles-Daniel Arreto 《Scientometrics》2007,73(2):231-256
During the 1974–2004 period, the sleep literature had quadrupled (2384 publications in 1974, and 9721 in 2004) while overall
scientific productivity had only doubled. The set of the seven most productive countries (USA, Japan, United Kingdom, Germany,
France, Canada and Italy) in sleep research, and the geographical region distribution remained stable over the three decades.
On the other hand several indicators appeared in the sleep research literature during the 1990s: the increasing productivity
of sleep researchers; the growing number of countries publishing on sleep; the continuous creation of sleep-focused journals;
the scattering of sleep publication among increasingly more scientific journals; the turnover among the leading journals;
and the emergence of new entities such as China, Turkey, and the European Union. 相似文献