全文获取类型
收费全文 | 7745篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 43篇 |
综合类 | 1篇 |
化学工业 | 206篇 |
金属工艺 | 29篇 |
机械仪表 | 26篇 |
建筑科学 | 44篇 |
矿业工程 | 23篇 |
能源动力 | 32篇 |
轻工业 | 99篇 |
水利工程 | 12篇 |
石油天然气 | 8篇 |
无线电 | 136篇 |
一般工业技术 | 198篇 |
冶金工业 | 6780篇 |
原子能技术 | 9篇 |
自动化技术 | 115篇 |
出版年
2022年 | 11篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 17篇 |
2013年 | 55篇 |
2012年 | 32篇 |
2011年 | 42篇 |
2010年 | 22篇 |
2009年 | 31篇 |
2008年 | 39篇 |
2007年 | 38篇 |
2006年 | 37篇 |
2005年 | 39篇 |
2004年 | 42篇 |
2003年 | 49篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 31篇 |
1999年 | 232篇 |
1998年 | 2105篇 |
1997年 | 1169篇 |
1996年 | 859篇 |
1995年 | 450篇 |
1994年 | 370篇 |
1993年 | 410篇 |
1992年 | 61篇 |
1991年 | 105篇 |
1990年 | 74篇 |
1989年 | 99篇 |
1988年 | 88篇 |
1987年 | 91篇 |
1986年 | 86篇 |
1985年 | 70篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 39篇 |
1981年 | 61篇 |
1980年 | 73篇 |
1979年 | 20篇 |
1978年 | 40篇 |
1977年 | 156篇 |
1976年 | 346篇 |
1975年 | 22篇 |
1974年 | 14篇 |
1973年 | 17篇 |
1972年 | 10篇 |
1971年 | 10篇 |
1967年 | 8篇 |
排序方式: 共有7761条查询结果,搜索用时 15 毫秒
81.
The benefits of using a comprehensive annotation strategy (employing underlining/circling, making connections, asking questions, and making comments) with knowledge maps (spatial/verbal arrays) and traditional, linear text to improve free recall scores for learners with individual differences in vocabulary and comprehension ability were examined. Types and frequencies of annotations generated were also examined for each stimulus format condition. Multiple regression analyses indicate that the frequency of use of two component annotation strategies, asking questions and making connections, were significant predictors of recall scores, while frequency of underlining/circling and generating elaborations failed to predict recall scores. Text users generated more underlining/circling, while knowledge map users generated more connections between ideas, suggesting that knowledge maps may facilitate the application of more productive annotation strategies. Also examined were the interrelationships between vocabulary ability, comprehension ability, and free recall scores. Copyright 1997Academic Press 相似文献
82.
LB Corbeil RP Gogolewski I Kacskovics KH Nielsen RR Corbeil JL Morrill R Greenwood JE Butler 《Canadian Metallurgical Quarterly》1997,61(3):207-213
AIMS/BACKGROUND: To characterise clinically a large kindred segregating retinitis pigmentosa and sensorineural hearing impairment in an autosomal dominant pattern and perform genetic linkage studies in this family. Extensive linkage analysis in this family had previously excluded the majority of loci shown to be involved in the aetiologies of RP, some other forms of inherited retinal degeneration, and inherited deafness. METHODS: Members of the family were subjected to detailed ophthalmic and audiological assessment. In addition, some family members underwent skeletal muscle biopsy, electromyography, and electrocardiography. Linkage analysis using anonymous microsatellite markers was performed on DNA samples from all living members of the pedigree. RESULTS: Patients in this kindred have a retinopathy typical of retinitis pigmentosa in addition to a hearing impairment. Those members of the pedigree examined demonstrated a subclinical myopathy, as evidence by abnormal skeletal muscle histology, electromyography, and electrocardiography. LOD scores of Zmax = 3.75 (theta = 0.10), Zmax = 3.41 (theta = 0.10), and Zmax = 3.25 (theta = 0.15) respectively were obtained with the markers D9S118, D9S121, and ASS, located on chromosome 9q34-qter, suggesting that the causative gene in this family may lie on the long arm (q) of chromosome 9. CONCLUSIONS: These data indicate that the gene responsible for the phenotype in this kindred is located on chromosome 9 q. These data, together with evidence that a murine deafness gene is located in a syntenic area of the mouse genome, should direct the research community to consider this area as a candidate region for retinopathy and/or deafness genes. 相似文献
83.
84.
85.
86.
The electromagnetic properties of electrically thick rectangular microstrip antennas were investigated experimentally. Antennas were fabricated with different patch sizes and with electrical thicknesses ranging from 0.03 to 0.23 wavelengths in the dielectric substrate. The resonant frequencies were measured and compared to existing formulas. The bandwidth was calculated as a function of electrical thickness and the antenna radiation patterns were measured. 相似文献
87.
A. V. Räisänen W. R. McGrath D. G. Crete P. L. Richards 《Journal of Infrared, Millimeter and Terahertz Waves》1985,6(12):1169-1189
Several scaled models have been used to determine the contributions of various waveguide mount parameters to the embedding impedance of a mm-wave SIS mixer. Measured effects of waveguide height, substrate orientation and width, junction location, lead inductance and RF-filter impedance are presented and discussed. 相似文献
88.
89.
90.
The electrical conductivity of hot-pressed polycrystalline aluminium nitride doped with oxygen and beryllium was measured as a function of temperature from 800 to 1200° C and over a range of nitrogen partial pressure from 102 to 105 Pa. The effect of beryllium dopant, the independence of conductivity from nitrogen partial pressure, and the observed activation energy suggested extrinsic electronic species or aluminium vacancies as charge carriers. Polarization measurements made with one electrode blocking to ionic species indicated that the aluminium nitride with oxygen impurity was an extrinsic electronic conductor. 相似文献