全文获取类型
收费全文 | 8892篇 |
免费 | 276篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 100篇 |
综合类 | 1篇 |
化学工业 | 1441篇 |
金属工艺 | 154篇 |
机械仪表 | 152篇 |
建筑科学 | 418篇 |
矿业工程 | 22篇 |
能源动力 | 223篇 |
轻工业 | 738篇 |
水利工程 | 64篇 |
石油天然气 | 41篇 |
武器工业 | 1篇 |
无线电 | 632篇 |
一般工业技术 | 1453篇 |
冶金工业 | 2157篇 |
原子能技术 | 65篇 |
自动化技术 | 1517篇 |
出版年
2021年 | 105篇 |
2020年 | 94篇 |
2019年 | 97篇 |
2018年 | 135篇 |
2017年 | 120篇 |
2016年 | 154篇 |
2015年 | 128篇 |
2014年 | 235篇 |
2013年 | 529篇 |
2012年 | 317篇 |
2011年 | 438篇 |
2010年 | 327篇 |
2009年 | 294篇 |
2008年 | 363篇 |
2007年 | 354篇 |
2006年 | 280篇 |
2005年 | 273篇 |
2004年 | 220篇 |
2003年 | 223篇 |
2002年 | 216篇 |
2001年 | 170篇 |
2000年 | 154篇 |
1999年 | 172篇 |
1998年 | 425篇 |
1997年 | 299篇 |
1996年 | 227篇 |
1995年 | 180篇 |
1994年 | 152篇 |
1993年 | 165篇 |
1992年 | 132篇 |
1991年 | 99篇 |
1990年 | 100篇 |
1989年 | 111篇 |
1988年 | 102篇 |
1987年 | 101篇 |
1986年 | 91篇 |
1985年 | 115篇 |
1984年 | 118篇 |
1983年 | 121篇 |
1982年 | 92篇 |
1981年 | 84篇 |
1980年 | 96篇 |
1979年 | 116篇 |
1978年 | 87篇 |
1977年 | 100篇 |
1976年 | 130篇 |
1975年 | 77篇 |
1974年 | 49篇 |
1973年 | 46篇 |
1972年 | 44篇 |
排序方式: 共有9179条查询结果,搜索用时 31 毫秒
21.
On the learning control of a robot manipulator 总被引:1,自引:0,他引:1
D. M. Dawson Z. Qu J. F. Dorsey F. L. Lewis 《Journal of Intelligent and Robotic Systems》1991,4(1):43-53
This paper derives a learning control law to achieve trajectory following for a robot manipulator. The controller consists of two parts, a computed torque servo for the rigid body terms that can be modelled and a learning law for the unmodelled dynamics. An advantage of this method is that bounds can be assigned to the position and velocity tracking errors. 相似文献
22.
Terahertz (THz) imaging is rapidly developing. We present two new methods, based respectively on (a) a broadband thermal source (globar) and (b) a coherent, monochromatic source (optically-pumped THz laser). A room-temperature detector (Golay cell) is employed. Image quality is similar to that reported by others using more complex sources (quantum cascade lasers) and detectors (superconducting tunneling junctions). 相似文献
23.
24.
Influence of ion bombardment on the properties and microstructure of unbalanced magnetron deposited niobium coatings 总被引:3,自引:0,他引:3
The effect of the ion bombardment to unbalanced magnetron deposited, approximately 1.5 and 4.5 μm thick, Nb coatings have been investigated as the bias voltage was varied from UB=−75 to −150 V. Increasing bias voltage increased the hardness of the coating from 4.5 to 8.0 GPa. This was associated with residual stress and Ar incorporation into the Nb lattice. Strong {110} texture developed in the samples deposited at low bias voltages, while beyond UB=−100 V a {111} texture became dominant. However, strong {111} texture was observed only with the thicker 3Nb coatings. Secondary electron microscopy investigation of the coating topography showed fewer defects in the thicker coatings. All coatings exhibited good corrosion resistance, with the thicker coatings clearly outperforming the thinner ones. Excessive bias voltages (UB=−150 V) was found to lead to poor adhesion and loss of corrosion resistance. 相似文献
25.
Geoffrey Rowden Shirley Dean James Campbell Philip Belitsky 《Microscopy research and technique》1985,2(6):547-555
Aspiration biopsy of tumors and transplanted organs is a popular atraumatic method for diagnosis and also for the management of patients. Apart from the cytological analyses, it is clear that large aggregates of cells are obtained and these may be examined by electron microscopy. A study was carried out with dogs to assess the yield of intact glomeruli and tubules, resulting from a standard fine-needle aspiration procedure. Employing a 20-gauge needle, yields of approximately ten intact glomeruli were obtained with a tissue processing protocol that utilized filtration through a nylon mesh and backwashing, to resuspend the trapped aggregates. Processing for electron microscopy was carried out in microcentrifuge tubes. The ultrastructural preservation was excellent and the extension of these studies to investigations of not only renal transplantation, but also for diagnosis in human renal diseases of a broad spectrum, is suggested. 相似文献
26.
Ozone measurement based on the optical absorption of visible light at 603 nm using polymer optical fibres is investigated and tested. Comparisons with a commercial UV based sensor demonstrate the ability of the visible based sensor to measure high concentrations over a range 27-127 mg/litre. A resolution of 5 mg/litre is also demonstrated for this sensor. 相似文献
27.
28.
29.
The toxins involved in ciguatera (fish poisoning) in the Caribbean Sea were isolated from Caranx latus, a pelagic fish often implicated in ciguatera in the Caribbean region, and purified by mouse bioassay directed fractionation. Five toxins were separated by reverse-phase high-performance liquid chromatography (HPLC). In order of increasing hydrophobicity, these toxins included a sleep-inducing fraction (< 1% of total toxicity), a major Caribbean ciguatoxin (C-CTX-1, 65% of toxicity), a minor Caribbean ciguatoxin (C-CTX-2, 13% of toxicity), a minor toxin (approximately 1% of toxicity) and a hydrophobic, fast-acting toxin (approximately 19% of toxicity). The i.p. injection into mice of each toxin induced signs typical of site-5 sodium channel activator toxins such as the Pacific ciguatoxins and brevetoxins. C-CTX-1 and C-CTX-2 were purified to homogeneity (LD50 = 3.6 and approximately 1 microgram/kg, respectively) and subjected to ion spray mass spectrometry. Both lost up to five H2O molecules and each had a [M+H]+ ion, m/z 1141.7, suggesting that C-CTX-1 and -2 are diastereomers that differ from the Pacific family of ciguatoxins. Turbo-assisted HPLC-mass spectrometry identified C-CTX-1, C-CTX-2 and three C-CTX-1-related compounds in an enriched fraction but no Pacific ciguatoxins were detected. The presence of different families of ciguatoxins in ciguateric fish from the Caribbean Sea and Pacific Ocean probably underlies the clinical differences in the ciguatera syndrome reported in these two regions. A Caribbean strain of the benthic dinoflagellate, Gambierdiscus toxicus, is suspected as source of these ciguatoxins. The extent to which these toxins are biotransformed as they pass through the marine food chain remains to be determined. 相似文献
30.
Liang-Yu Chen Gary W Hunter Philip G Neudeck Dak Knight 《Solid-state electronics》1998,42(12):2209-2214
The surface and interface properties of Pd0.9Cr0.1/SiC Schottky diode gas sensors both before and after annealing are investigated using Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). At room temperature the alloy reacted with SiC and formed PdxSi only in a very narrow interfacial region. After annealing for 250 h at 425°C, the surface of the Schottky contact area has much less silicon and carbon contamination than that found on the surface of an annealed Pd/SiC structure. Palladium silicides (PdxSi) formed at a broadened interface after annealing, but a significant layer of alloy film is still free of silicon and carbon. The chromium concentration with respect to palladium is quite uniform down to the deep interface region. A stable catalytic surface and a clean layer of Pd0.9Cr0.1 film are likely responsible for significantly improved device sensitivity. 相似文献