全文获取类型
收费全文 | 3874篇 |
免费 | 73篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 36篇 |
综合类 | 4篇 |
化学工业 | 671篇 |
金属工艺 | 83篇 |
机械仪表 | 51篇 |
建筑科学 | 189篇 |
矿业工程 | 11篇 |
能源动力 | 134篇 |
轻工业 | 347篇 |
水利工程 | 24篇 |
石油天然气 | 9篇 |
无线电 | 310篇 |
一般工业技术 | 495篇 |
冶金工业 | 1151篇 |
原子能技术 | 36篇 |
自动化技术 | 400篇 |
出版年
2022年 | 23篇 |
2019年 | 36篇 |
2018年 | 29篇 |
2017年 | 39篇 |
2016年 | 49篇 |
2015年 | 37篇 |
2014年 | 46篇 |
2013年 | 172篇 |
2012年 | 97篇 |
2011年 | 132篇 |
2010年 | 106篇 |
2009年 | 111篇 |
2008年 | 120篇 |
2007年 | 115篇 |
2006年 | 105篇 |
2005年 | 119篇 |
2004年 | 93篇 |
2003年 | 90篇 |
2002年 | 99篇 |
2001年 | 65篇 |
2000年 | 69篇 |
1999年 | 79篇 |
1998年 | 207篇 |
1997年 | 169篇 |
1996年 | 107篇 |
1995年 | 90篇 |
1994年 | 104篇 |
1993年 | 86篇 |
1992年 | 57篇 |
1991年 | 54篇 |
1990年 | 58篇 |
1989年 | 50篇 |
1988年 | 54篇 |
1987年 | 40篇 |
1986年 | 55篇 |
1985年 | 63篇 |
1984年 | 70篇 |
1983年 | 49篇 |
1982年 | 54篇 |
1981年 | 65篇 |
1980年 | 47篇 |
1979年 | 43篇 |
1978年 | 35篇 |
1977年 | 69篇 |
1976年 | 82篇 |
1975年 | 61篇 |
1974年 | 33篇 |
1973年 | 42篇 |
1972年 | 42篇 |
1970年 | 32篇 |
排序方式: 共有3951条查询结果,搜索用时 15 毫秒
51.
Gordon J.R. Povey 《Wireless Personal Communications》1998,8(2):151-164
A hybrid correlator architecture is described which combines the serial structure of an active correlator with the parallel structure of a matched filter correlator. The mean PN code acquisition time performance of this hybrid serial-parallel correlator structure is analysed. Results are shown which compare the acquisition performance of the serial, parallel, and serial-parallel structures. The results are for a PN code length of 64 code chips and assumes a Gaussian channel with the receiver detection threshold set to obtain a constant false alarm rate. An enhancement to the serial-parallel acquisition algorithm is also described which can increase the acquisition time performance by about 15% for typical operating conditions. Overall the results demonstrate that the hybrid correlator can provide rapid code acquisition with a limited receiver complexity. 相似文献
52.
V.D. Sandberg L. Bayliss M. Dugan J.S. Frank T. Gordon G. Hart C.M. Hoffman G.E. Hogan H.S. Matis G.H. Sanders H.P. Von Gunten 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,234(3):512-516
A circuit is described that determines the average of the transit time of light from an event in a scintillation counter to the two ends of that counter. The design offers superior time resolution and a novel gating scheme that significantly reduces circuit dead-time. 相似文献
53.
A visual–kinesthetic (V–K) dissociation procedure of neurolinguistic programming (NLP) was used in treating rape-induced anxiety and phobic reactions in 2 18- and 19-yr-old rape victims. NLP theory suggests that anxiety reactions experienced by rape victims is a function of the interrelated processes of synesthesia and anchoring. In these 2 case reports, the use of the V–K dissociation technique is explored. From this preliminary basis, further research entailing the use of this treatment procedure is suggested. Implications for clinical practice are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
55.
Rats with lesions to prefrontal cortex (PFC) or caudate nucleus (CN) were compared on tests of conditional associative learning (CAL) that placed varying demands on conditional rule learning and working-with-memory operations that are essential for response selection. Damage to either structure impaired performance, but the respective deficits resulted from disruption of different processes. CN lesions produced a consistent learning deficit that was thought to reflect a basic impairment in forming stimulus-response (S-R) associations. The behavior of PFC rats was more variable and depended on task requirements. When S-R learning or response selection was relatively easy, the PFC was not critical. However, when either component was made more difficult, thus requiring the contribution of strategic processes, PFC damage produced profound impairments. In addition to clarifying the roles of the PFC and CN in CAL, the results provide further evidence that multiple brain regions participate in relatively simple behavioral tasks and that their respective contributions can be dissociated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
Gordon Chin 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(10):1219-1234
An optically pumped submillimeter laser operating in the 500 μm (600 GHz) to 100 μm (3 THz) spectral range is the primary and, at present, the only available local oscillator (LO) source for laboratory and astronomical heterodyne applications for this wavelength region. A short review of the state-of-the-art of submillimeter lasers as LO sources, with an emphasis given to receiver systems designed for airborne heterodyne observations, will be presented. The characteristics and prospects for constructing a spacequalifiable laser LO system will also be given. 相似文献
57.
Corrosion of iron-base alloys at 982°C (1800°F) by coal char is observed and the phase morphologies are discussed. No sulfidation was observed at 50 hr exposure. After 100 hr internal aluminum-rich sulfides were observed along with thick outer scales of iron oxide. The species causing the hightemperature-induced corrosion are probably sulfides and sulfates, present in most coal chars. Possible mechanisms for the corrosion are also discussed.Department of Materials Science and Mineral Engineering. 相似文献
58.
59.
Howard W. Starkweather Thomas F. Jordan Gordon B. Dunnington 《Polymer Engineering and Science》1974,14(10):678-681
The yield stress is a simple function of the deformation ratio in the direction of testing for specimens oriented by uniaxial or biaxial stretching or rolling. Unless the yield stress increases more rapidly than in proportion to the deformation ratio, there will be instability during tensile creep under high loads. The relative merit of various polymers differs for creep and stress relaxation. Fatigue and bend recovery are also related to the molecular structure. 相似文献
60.
Michel Renou Bernard Lalanne-Cassou Didier Michelot Ginette Gordon Jean-Christophe Doré 《Journal of chemical ecology》1988,14(4):1187-1215
Female-emitted pheromones and sex attractants of Noctuidae were investigated using a specific computer procedure to analyze data collected from the literature. Correspondence analysis was used to survey the structure-activity relationships of sex pheromones in seven subfamilies. Structural, stereochemical, and functional features of active molecules were related to taxonomy. This multidimensional analysis revealed that the prevalent chemical frame of noctuid moth pheromones was a monounsaturated acetate withZ stereochemistry and a double bond on the fifth carbon closest to the nonfunctional branch of the molecule. Possible phylogenetic relationships within Noctuidae and between Noctuidae and other families are discussed in light of the sex pheromone biochemistry. Female sex pheromones appeared to be an additional character to be considered in the classification of noctuid moths. 相似文献