全文获取类型
收费全文 | 14336篇 |
免费 | 1786篇 |
国内免费 | 511篇 |
专业分类
电工技术 | 985篇 |
技术理论 | 1篇 |
综合类 | 721篇 |
化学工业 | 1539篇 |
金属工艺 | 197篇 |
机械仪表 | 327篇 |
建筑科学 | 1369篇 |
矿业工程 | 42篇 |
能源动力 | 4431篇 |
轻工业 | 123篇 |
水利工程 | 73篇 |
石油天然气 | 88篇 |
武器工业 | 24篇 |
无线电 | 3500篇 |
一般工业技术 | 2628篇 |
冶金工业 | 110篇 |
原子能技术 | 167篇 |
自动化技术 | 308篇 |
出版年
2024年 | 34篇 |
2023年 | 415篇 |
2022年 | 391篇 |
2021年 | 555篇 |
2020年 | 607篇 |
2019年 | 604篇 |
2018年 | 507篇 |
2017年 | 765篇 |
2016年 | 881篇 |
2015年 | 800篇 |
2014年 | 1130篇 |
2013年 | 1121篇 |
2012年 | 1144篇 |
2011年 | 1548篇 |
2010年 | 906篇 |
2009年 | 841篇 |
2008年 | 678篇 |
2007年 | 677篇 |
2006年 | 583篇 |
2005年 | 420篇 |
2004年 | 309篇 |
2003年 | 266篇 |
2002年 | 209篇 |
2001年 | 187篇 |
2000年 | 160篇 |
1999年 | 113篇 |
1998年 | 156篇 |
1997年 | 94篇 |
1996年 | 98篇 |
1995年 | 52篇 |
1994年 | 74篇 |
1993年 | 63篇 |
1992年 | 35篇 |
1991年 | 14篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 21篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1975年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
71.
A simple transient performance of floating cum tilted-wick type solar still has been presented by incorporating the effects of water flowing over a glass cover, heat capacity of tilted-wick water surface and floating-wick water surface. Explicit expressions for flowing water, glass, tilted-wick water surface and floating-wick water surface temperature and efficiency of the system have been derived. Numerical calculations have been carried out for a typical day in the month of March 2004. The relative standard deviations between the numerical and experimental results of different temperature components of the proposed still have been found. The results indicate that the relative standard deviations between theoretical and experimental results are less than 8% (glass cover), 2% (tiltedwick water surface), 1% (floating-wick water surface) and 2% (flowing water at the lower end of the glass cover) an average for the working hours of the day. Moreover, based on the numerical results, the following conclusions have been drawn: (i) glass cover temperature decreases significantly; (ii) the effect of water flowing over the glass cover has a fascinating effect on the production of distillate output during peak sunny hours; (iii) water flow rate of 1.5 m/s is optimum, and beyond it the efficiency decreases. Experimental investigations have been performed at Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore, India. 相似文献
72.
T. Hoshikawa 《Electrochimica acta》2006,51(25):5286-5294
Effects of the electrolyte of DSCs on impedance spectra were evaluated by changing concentration of redox couple, viscosity, and additives to electrolyte. The relation with current-voltage characteristics (I-V characteristics) was investigated. In many cases, the impedance component attributed to charge transfer at TiO2|electrolyte interface demonstrated strong relation with the I-V characteristics. The recombination of electrons in TiO2 with I3− in electrolyte was a key factor in determining performance of DSCs. To evaluate the effect of I3−, diffusion-limiting current in the electrolyte for various viscosities was evaluated by cyclic voltammetry. When the short circuit current (SCC) was almost equal to the diffusion-limiting current, strong influence of the diffusion coefficient on the impedance spectra was observed: impedance arcs were enlarged as the diffusion coefficient was decreased. On the other hand, when the diffusion-limiting current was larger than the SCC, photo-excitation and electron injection processes became dominating factors in the DSCs performance. The SCC was regulated by the charge recombination process at TiO2|electrolyte interface, and thus the impedance component ω3 was related to the performance in such condition. 相似文献
73.
采用共形离子溶液模型(conformalionic solution model, CIS) 在二元熔盐体系相图的基础上,对三元熔盐体系LiNO3-NaNO3-KNO3进行了相图计算,得到该三元体系最低共熔点为117.7℃,相应的摩尔分数组成分别为x(LiNO3) = 0.375,x(NaNO3) = 0.075,x(KNO3) = 0.550。按照热力学最低共熔点计算结果,采用熔融法制备了三元硝酸熔盐,通过DSC和TG实验测定其最低共熔点为118.3℃,这与计算得到的结果(117.7℃)基本一致。TG测试结果表明当温度低于587.2℃时,该三元熔盐体系较为稳定,其工作温度范围为118.3~587.2℃,该三元硝酸熔盐适合在太阳能热发电中作为高温传热蓄热材料使用。 相似文献
74.
The degradation and decolourization of direct dye (Everdirect supra turguoise blue, FBL), acidic dye (Isolan orange S-RL) and vat dye (Indanthren red FBB) have been investigated by solar/TiO2 process. The effects of solution pH, dye concentration, dosage of TiO2 and nano-size of TiO2 have been studied. The increase in initial pH (3, 5 and 11) and dye concentration decrease the removal rate. The treatment for FBB and FBL dye solutions is more efficient than that of S-RL.Under optimum conditions, the color removal is found to be almost complete for FBB and FBL while that of S-RL also reaches 95%. Langmuir adsorption isotherm and modified Langmuir-Hinshelwood kinetic model (L-H model) have been fitted to the experimental data and found to correlate the adsorption patterns as well as the kinetics of the dyes studied. 相似文献
75.
A. N. Zolotko Ya. I. Vovchuk V. G. Shevchuk N. I. Poletaev 《Combustion, Explosion, and Shock Waves》2005,41(6):611-621
The ignition and combustion of dust-gas suspensions are considered. It is shown that the ability of these systems to accumulate
heat is determined not only by their kinetic and thermal properties but also by the relation between their reaction surface
and the heat-removal surface (f). Experimental information on flame temperatures, ignition delays, and flame propagation over gas suspensions is processed
using the parameter f, and the postulate on the stimulating role of the developed reaction surface in activating these processes is validated.
It is shown that during overall burning, diffusion combustion of particles occurs only for rather small values of f. The ambiguous effect of the parameter f on the ignition and combustion processes leads to the necessity of optimizing the fuel size distribution and concentration
for the effective operation of the power devices. The role of the macroparameters of two-phase flames of refractory metals
in the synthesis of combustion nanoproducts is analyzed.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 3–14, November–December, 2005. 相似文献
76.
77.
Guiqiang Wang Ruifeng Lin Yuan Lin Xueping Li Xiaowen Zhou Xurui Xiao 《Electrochimica acta》2005,50(28):5546-5552
A novel Pt counter electrode for dye-sensitized solar cells (DSC) was prepared by thermal decomposition of H2PtCl6 on NiP-plated glass substrate. The charge-transfer kinetic properties of the platinized NiP-plated glass electrode (Pt/NiP electrode) for triiodide reduction were studied by electrochemical impedance spectroscopy. Pt/NiP electrode has the advantage over the platinized FTO conducting glass electrode (Pt/FTO electrode) in increasing the light reflectance and reducing the sheet resistance leading to improve the light harvest efficiency and the fill factor of the dye-sensitized solar cells effectively. The photon-to-current efficiency and the overall conversion efficiency of DSC using Pt/NiP counter electrode is increased by 20% and 33%, respectively, compared to that of using Pt/FTO counter electrode. Examination of the anodic dissolution and the long-term test on the variation of charge-transfer resistance indicates the good stability of the Pt/NiP electrode in the electrolyte containing iodide/triiodide. 相似文献
78.
79.
Momoji Kubo Tsuguo Kubota Changho Jung Minako Ando Satoshi Sakahara Kenji Yajima Kotaro Seki Rodion Belosludov Akira Endou Seiichi Takami Akira Miyamoto 《Catalysis Today》2004,89(4):479-493
Recently, we introduced a concept of combinatorial chemistry to computational chemistry and proposed a new method called “combinatorial computational chemistry”, which enables us to perform a theoretical high-throughput screening of catalysts. In the present paper, we reviewed our recent application of our combinatorial computational chemistry approach to the design of new catalysts for high-quality transportation fuels. By using our combinatorial computational chemistry techniques, we succeeded to predict new catalysts for methanol synthesis and Fischer–Tropsch synthesis. Moreover, we have succeeded in the development of chemical reaction dynamics simulator based on our original tight-binding quantum chemical molecular dynamics method. This program realizes more than 5000 times acceleration compared to the regular first-principles molecular dynamics method. Electronic- and atomic-level information on the catalytic reaction dynamics at reaction temperatures significantly contributes the catalyst design and development. Hence, we also summarized our recent applications of the above quantum chemical molecular dynamics method to the clarification of the methanol synthesis dynamics in this review. 相似文献
80.
A. A. Korzhavin I. G. Namyatov V. A. Bunev V. S. Babkin 《Combustion, Explosion, and Shock Waves》2003,39(6):635-643
The paper reports an experimental and theoretical study of the interaction of two diffusion flames propagating over the surface of two different liquid fuels applied to both sides of a thin metal substrate. It is shown that in this system, there may be formation of a unified complex — a doublesided flame which has the properties of a steadystate flame with a peculiar structures. Some velocity and structural dependences for doublesided flames are determined. A mathematical model for a doublesided flame is proposed that adequately describes experimental relations. A physical model for a doublesided flame with a pulsating flame of the heavier fuel is formulated. 相似文献