全文获取类型
收费全文 | 8549篇 |
免费 | 349篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 103篇 |
综合类 | 7篇 |
化学工业 | 1515篇 |
金属工艺 | 178篇 |
机械仪表 | 148篇 |
建筑科学 | 206篇 |
矿业工程 | 13篇 |
能源动力 | 286篇 |
轻工业 | 541篇 |
水利工程 | 39篇 |
石油天然气 | 87篇 |
无线电 | 492篇 |
一般工业技术 | 965篇 |
冶金工业 | 3646篇 |
原子能技术 | 34篇 |
自动化技术 | 669篇 |
出版年
2023年 | 50篇 |
2022年 | 133篇 |
2021年 | 170篇 |
2020年 | 138篇 |
2019年 | 203篇 |
2018年 | 286篇 |
2017年 | 207篇 |
2016年 | 213篇 |
2015年 | 179篇 |
2014年 | 211篇 |
2013年 | 464篇 |
2012年 | 247篇 |
2011年 | 318篇 |
2010年 | 270篇 |
2009年 | 263篇 |
2008年 | 235篇 |
2007年 | 178篇 |
2006年 | 193篇 |
2005年 | 127篇 |
2004年 | 120篇 |
2003年 | 158篇 |
2002年 | 114篇 |
2001年 | 81篇 |
2000年 | 97篇 |
1999年 | 181篇 |
1998年 | 1105篇 |
1997年 | 662篇 |
1996年 | 425篇 |
1995年 | 285篇 |
1994年 | 212篇 |
1993年 | 244篇 |
1992年 | 54篇 |
1991年 | 91篇 |
1990年 | 70篇 |
1989年 | 85篇 |
1988年 | 84篇 |
1987年 | 86篇 |
1986年 | 57篇 |
1985年 | 59篇 |
1984年 | 25篇 |
1983年 | 31篇 |
1982年 | 35篇 |
1981年 | 34篇 |
1980年 | 43篇 |
1979年 | 16篇 |
1978年 | 25篇 |
1977年 | 115篇 |
1976年 | 155篇 |
1975年 | 26篇 |
1973年 | 18篇 |
排序方式: 共有8929条查询结果,搜索用时 11 毫秒
31.
A. A. Nechitaĭlov T. K. Zvonareva A. D. Remenyuk V. A. Tolmachev D. N. Goryachev O. S. El’tsina L. V. Belyakov O. M. Sreseli 《Semiconductors》2008,42(10):1249-1254
Catalytic properties of composite amorphous carbon-platinum layers produced by magnetron cosputtering have been studied. The layers were characterized by electron microscopy, IR spectroscopy, ellipsometry, gravimetry, and spectrophotometric chemical analysis. The catalytic activity of the layers was studied in an air-hydrogen fuel cell by measuring its load and power characteristics. 相似文献
32.
L. V. El’nikova 《Journal of Superconductivity and Novel Magnetism》2007,20(2):197-199
We describe the lyotropic liquid crystalline phase transitions in the lipid mixture dipalmitoil-PC/dilauroy-PC/cholesterol
by 3D spin-1 lattice model. The formation of nanoscale domains with the characteristic size about 300 nm was studied in experiments
on confocal fluorescence microscopy (CFM) (G. V. Feigenson and J. T. Buboltz, Biophys. J.
80, 2775 (2001)). The structure parameters of the lamellar vesicle in dipalmitoil-PC-rich phase, corresponding to these regions,
are verified by numerical Monte Carlo simulations on the lattice. We point its superconductivity analogy properties at the
region of phase stability for composition-dependent nanoscopic region. 相似文献
33.
The corrosion behaviour of tin in different concentrations of citric acid solutions (0.3–1.0 M, pH=1.8) was studied at 30 °C by potentiodynamic technique. The E/I profiles exhibit an active passive behaviour. The active dissolution involves one anodic peak A associated with a dissolution of the metals as Sn(II) species. The passivity is due to the formation of thin film of SnO2 and or Sn(OH)4 on the anode surface. The cathodic sweep shows a small peak C related to the reduction of the passive film. The peak current density Ip of peak A increases with increasing both acid concentration and sweep rate.
The effects of adding increasing concentrations of Na2CrO4, NaMoO4, NaNO3 and NaNO2 on the corrosion of tin in 0.5 M citric acid at 30 °C were investigated. Both CrO42− and MoO42− ions inhibit the corrosion of tin and the extent of inhibition enhances with their concentrations. Addition of either NO3− or NO2− accelerates the corrosion of tin. NO3− ions are more aggressive than NO2− ions. 相似文献
34.
35.
36.
The aim of the present study was to determine the afferent connections of the nucleus accumbens in snakes, in particular its catecholaminergic input. For that purpose, in vitro and in vivo applications of retrograde tracers in the nucleus accumbens of Elaphe guttata were combined with tyrosine hydroxylase (TH) immunohistochemistry. Both techniques revealed telencephalic inputs to the nucleus accumbens originating from the diagonal band of Broca, ventral pallidum, amygdaloid complex, and dorsal cortex. Major diencephalic inputs arise from the dorsomedial thalamic nucleus and the hypothalamus. In the brainstem, a few retrogradely labeled cells were observed in the raphe nucleus and the locus coeruleus. Considerably more cells were found in the midbrain tegmentum. Within the confines of the locus coeruleus and, in particular, the midbrain tegmentum, retrogradely labeled cells stained also for TH suggesting that those areas constitute the major catecholaminergic input to the nucleus accumbens of snakes. The experimental approach used in the present study, in particular the in vitro technique, seems to be very suited for studying the development of basal ganglia organization of reptiles in the near future. 相似文献
37.
38.
We used a new injury device that produces consistent spinal cord contusion injuries (T8) in rats to compare the behavioral and histologic effects of methylprednisolone sodium succinate (MPSS) administration, the clinical standard of therapy after acute spinal cord injury (ASCI), with the 21-aminosteroid, U-74006F (U74), and the TRH analogue, YM-14673 (YM), at different trauma doses. Three sequential experiments were conducted: Experiment 1. U74 (3.0/1.5/1.5 mg/kg; 10/5/5 mg/kg; 30/15/15 mg/kg), MPSS (30/15/15 mg/kg), or vehicle were administered intravenously (i.v.) at 5 min, 2 and 6 h after the injury (n = 8/group). U74 (10/5/5 mg/kg) and MPSS animals scored better than controls (Days 8-43) in open field walking (OFW); no other differences were seen between groups. Experiment 2. Dose-response evaluation of MPSS determined more effective doses. Groups (n = 16) receiving 30/30/30/30 mg/kg and 60/60/60/60 mg/kg i.v. at 5 min and 2, 4, and 6 h after the injury had better OFW scores than controls (Days 8-29; Day 29). Both groups performed better than controls (Days 8-29) on inclined plane (IP); 30 mg/kg animals scored higher on Day 29. Percentage tissue spared (%TS) at the lesion center was greater for 60 mg/kg animals (23.4%) than controls (17.3%). Experiment 3. Compounds were administered as in experiment 2 (n = 15/group); MPSS (60/30/30/30 mg/kg) and YM (1/1/1/1 mg/kg and 1 mg/kg/day ip) were most effective. YM and MPSS combination produced no additive effects. YM animals scored better than MPSS and control animals in OFW (Days 8-29) and better than controls on IP (Days 8-29; Day 29) and grid walking (Day 29). MPSS animals scored better than controls on IP (Days 8-29). YM and MPSS groups had greater %TS than controls. This series of experiments demonstrates the utility of this injury model and simple behavioral measures for preclinical assessment of pharmacologic agents. Under these experimental conditions, U74 demonstrated equivalent efficacy to MPSS, and YM demonstrated greater efficacy than MPSS in the treatment of ASCI. 相似文献
39.
40.
N Iyer MS Reagan KJ Wu B Canagarajah EC Friedberg 《Canadian Metallurgical Quarterly》1996,35(7):2157-2167