全文获取类型
收费全文 | 26427篇 |
免费 | 1527篇 |
国内免费 | 561篇 |
专业分类
电工技术 | 808篇 |
综合类 | 707篇 |
化学工业 | 4824篇 |
金属工艺 | 925篇 |
机械仪表 | 1048篇 |
建筑科学 | 1770篇 |
矿业工程 | 383篇 |
能源动力 | 762篇 |
轻工业 | 1791篇 |
水利工程 | 339篇 |
石油天然气 | 910篇 |
武器工业 | 73篇 |
无线电 | 2719篇 |
一般工业技术 | 4103篇 |
冶金工业 | 3240篇 |
原子能技术 | 147篇 |
自动化技术 | 3966篇 |
出版年
2024年 | 48篇 |
2023年 | 299篇 |
2022年 | 498篇 |
2021年 | 751篇 |
2020年 | 510篇 |
2019年 | 495篇 |
2018年 | 606篇 |
2017年 | 602篇 |
2016年 | 691篇 |
2015年 | 743篇 |
2014年 | 1063篇 |
2013年 | 1644篇 |
2012年 | 1451篇 |
2011年 | 1840篇 |
2010年 | 1469篇 |
2009年 | 1358篇 |
2008年 | 1521篇 |
2007年 | 1442篇 |
2006年 | 1363篇 |
2005年 | 1253篇 |
2004年 | 931篇 |
2003年 | 759篇 |
2002年 | 770篇 |
2001年 | 563篇 |
2000年 | 551篇 |
1999年 | 632篇 |
1998年 | 601篇 |
1997年 | 489篇 |
1996年 | 441篇 |
1995年 | 415篇 |
1994年 | 364篇 |
1993年 | 312篇 |
1992年 | 261篇 |
1991年 | 146篇 |
1990年 | 196篇 |
1989年 | 159篇 |
1988年 | 140篇 |
1987年 | 125篇 |
1986年 | 107篇 |
1985年 | 144篇 |
1984年 | 142篇 |
1983年 | 89篇 |
1982年 | 83篇 |
1981年 | 72篇 |
1980年 | 53篇 |
1979年 | 58篇 |
1978年 | 43篇 |
1977年 | 31篇 |
1976年 | 40篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Thirty six patients of pulmonary or nasopharyngeal carcinoma were treated with Xilixin granule (XLXG) combined with radiotherapy and compared their efficacy with that of 31 patients treated by Zhenqi Fuzheng granule combined with radiotherapy for control. Results showed that the symptoms of Yin Deficiency syndrome in treated group were obviously improved, the leucocyte decreased by 5.6%, while in control group it reached 25.8%, the 3 year survival rate was significantly higher in treated group (75.0%) than that in control group (51.6%). Animal experiment revealed that XLXG had the effects of tumor inhibition, it could increase white blood cells, platelets and hemoglobin of patients, especially in using large dosage. These results suggested that XLXG have some protective effect against radiotherapeutic damage in patients with malignant tumor. 相似文献
63.
The excited state phosphorescence lifetime of alexandrite crystals is used to monitor temperature in the physiological range from 15-45°C with precision and accuracy of 0.2°C. A 500-μm cubic alexandrite crystal bounded to the distal end of an optical fiber of similar core dimensions is excited with pulsed Ne-He laser light. This apparatus uses a sampler for data acquisition and frequency domain methods for data fitting. The instrument amplifies the AC components of the detector output and band limits the signal to 12.5 kHz. The fundamental frequency of the excitation is set to 195.13 Hz to obtain 64 harmonics. This band limited signal is sampled and averaged over few hundred cycles in the time domain. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio of each sampled harmonic are then computed. Five to 50 values of the phase and modulations are averaged before computing the sensor lifetime. The instrument is capable of measuring precise and accurate excited state lifetimes from subpicowatt luminescent signals in plastic optical fibers. A least squares fit yields the lifetimes of single exponentials. A component of zero lifetime is introduced to account for the backscatter excitation seen by the photodetector leaking through optical interference filters. The phosphorescence lifetimes measured reproducibly to about three parts in a thousand are used to monitor physiological temperature. Temperatures are computed employing empirical polynomials. The system drift is negligible over 15 h of continuous operation. The instrumentation and methods allow 1.3-s update times and 30-s full response times 相似文献
64.
DC Sutton R Kluger SU Ahmed SC Reimold JB Mark 《Canadian Metallurgical Quarterly》1994,108(3):576-582
This study assessed the value of biplane transesophageal echocardiographic assessment of diastolic flow reversal in the descending aorta as an alternative to Doppler color flow imaging in determining severity of aortic regurgitation. In 45 patients undergoing cardiac operations, the severity of aortic regurgitation was assessed by semiquantitative grading of the width of the Doppler color flow regurgitant jet relative to the left ventricular outflow tract, and the presence of diastolic flow reversal was assessed with pulsed-wave Doppler measurements at three sites in the descending aorta. In four patients, the diastolic flow reversal method was the only available form of assessment because of inadequate visualization of the left ventricular outflow tract beneath a mitral valve prosthesis. Diastolic flow reversal in the descending aorta was not observed in patients without aortic regurgitation and was always present in patients with severe aortic regurgitation. Aortic valve replacement successfully eliminated descending aortic flow reversal in all 19 patients in whom it was present before valve replacement. Identification of diastolic flow reversal at multiple sites in the descending aorta with biplane transesophageal echocardiography helps to confirm the presence of severe aortic regurgitation and can serve as an alternative method of assessment when visualization of the left ventricular outflow tract is impaired. 相似文献
65.
66.
Roger Norman Rothon Christopher Mark Liauw Graham Clayton Lees Wayne Christopher Edward Schofield 《The Journal of Adhesion》2002,78(7):603-628
The interaction of ammonium stearate (AS) and γ-aminopropyltriethoxysilane (APS) treatments with a magnesium hydroxide flame retardant filler and their effects on its use in an ethylene vinyl acetate copolymer compound have been investigated. The work has shown clear evidence of changes in the structure of the surface layers formed on the filler as the amount of additive is increased and the levels at which these occur can be correlated with theoretical monolayer quantities. Infrared (IR) spectroscopy data suggest that the stearate coating changes from a half salt to a full salt as the coating level is increased and that the APS coating on the filler initially has a significant bicarbonate content, presumably due to reaction with atmospheric carbon dioxide. The effect of coating level on the melt flow rate, insoluble matrix content, crystallisation behaviour, tensile properties, limiting oxygen index, and ageing of the filled compound has been studied. Distinct trends have been observed, many of which can be correlated with the structure of the filler surface layers. Of particular importance is the observation that, unlike APS, excess stearate appears to promote detrimental ageing effects. 相似文献
67.
Examined the effect of lesions of the caudate nucleus or fimbria-fornix on the acquisition of 2 water maze tasks. In both tasks, 2 rubber balls with different visual patterns were used as cues. The correct cue was attached to a submerged rectangular platform and could be mounted by an animal to escape the water. The incorrect cue was attached to a thin round pedestal and could not be mounted. In a spatial version of the task, the correct cue was located in the same quadrant of the maze on all trials, whereas the visual pattern on the cue was varied from trial to trial. Lesions of the fornix, but not the caudate nucleus, impaired acquisition of this spatial task in relation to control animals. In a simultaneous visual discrimination version of the task, the correct cue on all trials was one with a specific visual pattern, and the spatial location of the correct cue was varied from trial to trial. Lesions of the caudate nucleus, but not the fornix, impaired acquisition of this visual discrimination task in relation to control animals. The double dissociation observed supports the hypothesis that the hippocampus and caudate nucleus are parts of systems that differ in the type of memory they mediate. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
69.
70.