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   452244篇
  免费   37840篇
  国内免费   23026篇
电工技术   58365篇
技术理论   55篇
综合类   41044篇
化学工业   41099篇
金属工艺   16304篇
机械仪表   33621篇
建筑科学   41432篇
矿业工程   19626篇
能源动力   15876篇
轻工业   25555篇
水利工程   16357篇
石油天然气   31483篇
武器工业   6599篇
无线电   41791篇
一般工业技术   25990篇
冶金工业   14695篇
原子能技术   4625篇
自动化技术   78593篇
  2024年   1428篇
  2023年   4376篇
  2022年   9135篇
  2021年   11578篇
  2020年   12057篇
  2019年   9154篇
  2018年   8295篇
  2017年   11726篇
  2016年   13804篇
  2015年   15367篇
  2014年   29998篇
  2013年   25067篇
  2012年   33645篇
  2011年   35329篇
  2010年   26610篇
  2009年   26644篇
  2008年   25953篇
  2007年   32358篇
  2006年   29769篇
  2005年   26136篇
  2004年   22120篇
  2003年   19984篇
  2002年   15926篇
  2001年   13454篇
  2000年   11111篇
  1999年   8908篇
  1998年   6607篇
  1997年   5518篇
  1996年   4562篇
  1995年   3781篇
  1994年   3056篇
  1993年   2107篇
  1992年   1727篇
  1991年   1241篇
  1990年   982篇
  1989年   816篇
  1988年   596篇
  1987年   362篇
  1986年   262篇
  1985年   276篇
  1984年   262篇
  1983年   189篇
  1982年   163篇
  1981年   130篇
  1980年   95篇
  1979年   70篇
  1978年   46篇
  1977年   41篇
  1976年   34篇
  1959年   35篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
2.
3.
文章首先对智能化电子信息技术进行了深入的研究,而后分析了该技术在应用过程中出现的问题,最后结合该技术的相关特点给出了相应的问题解决措施,希望能够对智能化电子信息技术的发展提供帮助。  相似文献   
4.
5.
《Ceramics International》2022,48(11):15207-15217
SCAPS solar cell simulation program was applied to model an inverted structure of perovskite solar cells using Cu-doped Ni1-xO thin films as hole transport layer. The Cu-doped Ni1-xO film were made by co-sputtering deposition under different deposition conditions. By increasing the amount of the Cu-dopant, the film crystallinity enhanced whereas the bandgap energy decreased. The transmittance of the thin films decreased significantly by increasing the sputtering power of copper. High quality, uniform, compact, and pin-hole free films with low surface roughness were achieved. The structural, chemical, surface morphology, optical, electrical, and electronic properties of the Cu doped Ni1-xO films were used as input parameters in the simulation of Pb-based (MAPbI3-xClx) and Pb-free (MAGeI3) perovskite solar cells. Simulation results showed that the performance of both Pb-based and Pb-free perovskite solar cell devices significantly enhanced with Cu-doped Ni1-xO film. The highest power conversion efficiency (PCE) for the Pb-free perovskite solar cell is 8.9% which is lower than the highest PCE of 17.5% for the Pb-based perovskite solar cell.  相似文献   
6.
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated.  相似文献   
7.
On-site hydrogen production through steam-methane reforming (SMR) from city gas or natural gas is believed to be a cost-effective way for hydrogen-based infrastructure due to high cost of hydrogen transportation. In recent years, there have been a lot of on-site hydrogen fueling stations under design or construction in China. This study introduces current developments and technology prospects of skid-mounted SMR hydrogen generator. Also, technical solutions and economic analysis are discussed based on China's first on-site hydrogen fueling station project in Foshan. The cost of hydrogen product from skid-mounted SMR hydrogen generator is about 23 CNY/kg with 3.24 CNY/Nm3 natural gas. If hydrogen price is 60 CNY/kg, IRR of on-site hydrogen fueling station project reaches to 10.8%. While natural gas price fall to 2.3 CNY/Nm3, the hydrogen cost can be reduced to 18 CNY/kg, and IRR can be raised to 13.1%. The conclusion is that skid-mounted SMR technology has matured and is developing towards more compact and intelligent design, and will be a promising way for hydrogen fueling infrastructures in near future.  相似文献   
8.
9.
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results.  相似文献   
10.
In this study, the effects of cell temperature and relative humidity on charge transport parameters are numerically analyzed. In order to perform this analysis, three-dimensional and anisotropic numerical models are developed. The numerical models are integrated into the experimental values for anisotropic electrical conductivities, as depending on cell temperature and relative humidity, that were obtained from our previous study. The achieved results indicate that the values of current densities in the in-plane direction increase with increasing cell temperature and relative humidity, while the current densities reach a maximum in the rib regions for both the numerical model at the through-plane direction. The behaviors of electrolyte potentials are similar with changes in the cell temperature and relative humidity. In addition, the cathode electrical potentials in both the in-plane direction and through-plane direction do not change to a considerable amount with increasing cell temperature and relative humidity.  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