首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2109篇
  免费   54篇
  国内免费   2篇
电工技术   17篇
综合类   1篇
化学工业   360篇
金属工艺   24篇
机械仪表   18篇
建筑科学   16篇
能源动力   70篇
轻工业   74篇
水利工程   5篇
石油天然气   1篇
无线电   59篇
一般工业技术   186篇
冶金工业   1232篇
原子能技术   15篇
自动化技术   87篇
  2023年   14篇
  2022年   30篇
  2021年   43篇
  2020年   32篇
  2019年   37篇
  2018年   41篇
  2017年   44篇
  2016年   56篇
  2015年   21篇
  2014年   35篇
  2013年   65篇
  2012年   52篇
  2011年   59篇
  2010年   39篇
  2009年   32篇
  2008年   25篇
  2007年   24篇
  2006年   24篇
  2005年   18篇
  2004年   15篇
  2003年   14篇
  2002年   13篇
  2001年   12篇
  2000年   9篇
  1999年   50篇
  1998年   335篇
  1997年   188篇
  1996年   140篇
  1995年   101篇
  1994年   73篇
  1993年   82篇
  1992年   17篇
  1991年   23篇
  1990年   24篇
  1989年   18篇
  1988年   26篇
  1987年   32篇
  1986年   20篇
  1985年   27篇
  1984年   9篇
  1983年   13篇
  1982年   28篇
  1981年   28篇
  1980年   25篇
  1979年   7篇
  1978年   7篇
  1977年   42篇
  1976年   82篇
  1973年   4篇
  1972年   4篇
排序方式: 共有2165条查询结果,搜索用时 343 毫秒
91.
Density functional theory and polarizable continuum model are used to calculate ionization potential of thin-films of 12 organic molecules. Computed values are compared with experimental values obtained from ultraviolet photoemission spectroscopy. The excellent correlation shows that it is possible to determine the ionization potential of organic molecules in solid-state within ±0.15 eV of the experimental value. This method is useful for chemists in designing molecules for organic electronics.  相似文献   
92.
In sequel to our recent report,[1] we demonstrate in this article the effect of chemistry on nonisothermal tempering and softening behavior of dual-phase steels. The martensite morphology and tempered structure were analyzed using electron microscopy. Electron energy loss spectrometry and energy-dispersive X-ray spectroscopy were used for a compositional analysis. It was observed that characteristic of the tempered structure in dual-phase (DP) steels was a function of prior martensite structure and chemistry, which in turn influence the extent of softening.  相似文献   
93.
Polymer Light Emitting Diodes (PLEDs), the most promising name in the field of display technology has received tremendous attention from various research groups. The research on light emitting polymers are an interdisciplinary zone which has challenging investigates on materials science and engineering, physics of device architecture and technology. This review addresses the wide range of tailored polymers, evolution of LED device structure for high performance, single and multicolor polymer based LEDs. Though, polymers are possessing better efficiency and easy fabrication processes, it has very low stability and short life. This study also reviews, device degradation during device fabrication and operation.  相似文献   
94.
ScienceTomorrow is developing a high-speed, low-cost process for synthesizing high-porosity electrodes for electrochemical double-layer capacitors. Four types of coal (lignite, subbituminous, bituminous, and anthracite) were used as precursor materials for spark discharge activation with multiscale porous structure. The final porosity and pore distribution depended, among other factors, on precursor type. The high gas content in low-grade carbon resulted in mechanical disintegration, whereas high capacitance was attained in higher-grade coal. The properties, including capacitance, mechanical robustness, and internal conductivity, were excellent when the cost is taken into consideration.  相似文献   
95.
Niva Nayak 《Fuel》2010,89(1):53-58
Although fly ash disposal is of environmental concern the quality of residues can be improved with respect to high value applications. Fly ash is considered as a potential source of aluminium and other strategic metals. Leaching and metal extraction behaviour of fly ash collected from Talcher Thermal Power Station have been thoroughly studied using sulphuric acid as extractant. The chemical and mineralogical composition of post-leached samples have been determined. Aluminium extraction by direct leaching at low acid concentration and ambient temperature is not suitable for high recovery. The extraction efficiency of aluminium increases significantly at a higher solid:liquid ratio. It is evident that the leachability of metals from fly ash depends on the nature of leaching medium, solid:liquid ratio, temperature and leaching time.  相似文献   
96.
Crawford JO  Wanibe E  Nayak L 《Ergonomics》2002,45(13):922-933
The following study investigated wrist torque strength measurements of a group of younger and older adults. The aim of the study was to examine the impact of shape, diameter and height of lid on wrist torque opening strength. Forty participants took part in the study in four groups, younger males and females and older males and females. Data were collected for 12 test pieces. Anthropometric data were also obtained for stature, weight, hand breadth, hand length, chuck grip force, grip force, lateral grip force and pinch grip force. The analysis of the wrist torque strength measurements found that participants could exert greater force with square test pieces compared to circular test pieces of the same diameter. Examination of the circular test pieces found that as diameter and height increased, so did torque exertion data for the test pieces between 20 mm and 50 mm diameter. The surface area of the test pieces was found to be highly correlated with the level of torque exertion, thus a linear model was developed to describe this relationship. The model could be used to predict maximal torque closure levels for use in the packaging industry. The anthropometric data revealed that as height, weight, hand length and hand breadth increased, there was a correlation with the levels of torque exerted. Future research needs to further examine the relationship between surface area and torque exerted and the design of spherical lids to increase the contact area between the hand and the lid.  相似文献   
97.
This correspondence presents a novel application of the theta function defined by Lovasz. The problem of coding for transmission of a source through a channel without error when the receiver has side information about the source is analyzed. Using properties of the Lovasz theta function, it is shown that separate source and channel coding is asymptotically suboptimal in general. By contrast, in the case of vanishingly small probability of error, separate source and channel coding is known to be asymptotically optimal. For the zero-error case, it is further shown that the joint coding gain can in fact be unbounded. Since separate coding simplifies code design and use, conditions on sources and channels for the optimality of separate coding are also derived  相似文献   
98.
-FeSi2 is an important semiconducting silicide which is being studied extensively. In this paper, we report our results of the effect of laser and laser-thermal annealing on the properties of -FeSi2. 5N purity Fe was deposited on Si substrate and was subsequently irradiated by CW and pulsed laser separately followed by thermal annealing to reduce the laser induced damage. The samples were then characterized by sheet resistance, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical reflectance and absorption studies. Lastly, -FeSi2/n-Si heterojunctions were fabricated and the effect of laser treatment on the junction ideality factor was investigated. All these characterizations indicated the formation of good quality -FeSi2, particularly after pulsed laser followed by thermal treatment.  相似文献   
99.
A case of cardiac syncope is presented, associated with single vessel coronary disease. The mechanism of the syncope would appear to be a ventricular arrhythmia with transmural myocardial ischaemia due to transient occlusion of the diseased coronary artery. The symptoms and electrocardiographic abnormalities were reproduced and subsequently abolished by percutaneous coronary angioplasty.  相似文献   
100.
The effects of deprenyl on methamphetamine-induced dopamine depletions were studied in mice. Four SC injections of 12.5 mg/kg of methamphetamine at two-hour intervals caused substantial (72-82%) and long-lasting depletions of striatal dopamine. Pretreatment with either 25 or 40 mg/kg of deprenyl did not significantly alter the magnitude of this depletion. These results indicate that, unlike what is observed following MPTP, there is no protection afforded dopaminergic cells by deprenyl pretreatment in the methamphetamine model of parkinsonism.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号