全文获取类型
收费全文 | 128693篇 |
免费 | 11474篇 |
国内免费 | 6286篇 |
专业分类
电工技术 | 8186篇 |
技术理论 | 7篇 |
综合类 | 9167篇 |
化学工业 | 20681篇 |
金属工艺 | 7727篇 |
机械仪表 | 8786篇 |
建筑科学 | 10792篇 |
矿业工程 | 4303篇 |
能源动力 | 3766篇 |
轻工业 | 9126篇 |
水利工程 | 2428篇 |
石油天然气 | 8425篇 |
武器工业 | 1155篇 |
无线电 | 13751篇 |
一般工业技术 | 14487篇 |
冶金工业 | 6048篇 |
原子能技术 | 1373篇 |
自动化技术 | 16245篇 |
出版年
2024年 | 473篇 |
2023年 | 2100篇 |
2022年 | 3724篇 |
2021年 | 5407篇 |
2020年 | 4213篇 |
2019年 | 3433篇 |
2018年 | 3698篇 |
2017年 | 4178篇 |
2016年 | 3839篇 |
2015年 | 5374篇 |
2014年 | 6553篇 |
2013年 | 7673篇 |
2012年 | 8420篇 |
2011年 | 8980篇 |
2010年 | 7895篇 |
2009年 | 7488篇 |
2008年 | 7549篇 |
2007年 | 7092篇 |
2006年 | 7319篇 |
2005年 | 6128篇 |
2004年 | 4200篇 |
2003年 | 3983篇 |
2002年 | 4102篇 |
2001年 | 3687篇 |
2000年 | 3126篇 |
1999年 | 3158篇 |
1998年 | 2369篇 |
1997年 | 1986篇 |
1996年 | 1919篇 |
1995年 | 1587篇 |
1994年 | 1268篇 |
1993年 | 802篇 |
1992年 | 712篇 |
1991年 | 489篇 |
1990年 | 376篇 |
1989年 | 324篇 |
1988年 | 244篇 |
1987年 | 153篇 |
1986年 | 122篇 |
1985年 | 68篇 |
1984年 | 47篇 |
1983年 | 41篇 |
1982年 | 45篇 |
1981年 | 34篇 |
1980年 | 47篇 |
1979年 | 20篇 |
1978年 | 1篇 |
1965年 | 1篇 |
1959年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
Wei Ren Fuchun Nan Dr. Shumu Li Prof. Sijin Yang Prof. Jiechao Ge Prof. Zhenwen Zhao 《ChemMedChem》2021,16(4):646-653
Negatively charged fluorescent carbon dots (CDs, Em=608 nm) were hydrothermally prepared from thiophene phenylpropionic acid polymers and then successfully loaded with the positively charged anticancer cargo coptisine, which suffers from poor bioavailability. The formed CD-coptisine complexes were thoroughly characterized by particle size, morphology, drug loading efficiency, drug release, cellular uptake and cellular toxicity in vitro and antitumor activities in vivo. In this nano-carrier system, red emissive CDs possess multiple advantages as follows: 1) high drug loading efficiency (>96 %); 2) sustained drug release; 3) enhanced drug efficacy towards cancer cells; 4) EPR effect; 5) drug release tracing with near-infrared imaging. These properties indicated that red emissive CDs prepared from polymers could be used as a novel drug delivery system with integrated therapeutic and imaging functions in cancer therapy, which are expected to have great potential in future clinical applications. 相似文献
992.
Ling Tan Kipkorir Peter Jing Ren Baoyang Du Xiaojie Hao Yufei Zhao Yu-Fei Song 《Frontiers of Chemical Science and Engineering》2021,15(1):99-108
The rational design of photocatalyst that can effectively reduce CO2 under visible light(l>400 nm),and simultaneously precise control of the products syngas(CO/H2)ratio is highly desirable for the Fischer-Tropsch reaction.In this work,we synthesized a series of CeO2-decorated layered double hydroxides(LDHs,Ce-x)samples for photocatalytic CO2 reduction.It was found that the selectivity and productivity of CO and H2 from photoreduction of CO2 in conjunction with Ru-complex as photosensitizer performed an obvious“volcano-like”trend,with the highest point at Ce-0.15 and the CO/H2 ratio can be widely tunable from 1/7.7 to 1/1.3.Furthermore,compared with LDH,Ce-0.15 also drove photocatalytic CO2 to syngas under 600 nm irradiation.It implied that an optimum amount of CeO2 modifying LDH promoted the photoreduction of CO2 to syngas.This report gives the way to fully utilize the rare earth elements and provides a promising route to enhance the photo-response ability and charge injection efficiency of LDH-based photocatalysts in the synthesis of syngas with a tunable ratio under visible light irradiation. 相似文献
993.
Zhihong Xu Tao Jiang Hao Zhang Yujun Zhao Xinbin Ma Shengping Wang 《Frontiers of Chemical Science and Engineering》2021,15(3):698
Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation. The effect of Na+ and MgO on the structure and CO2 adsorption performance of CaO sorbent pellets was elucidated. MgO-doped CaO sorbent pellets with the diameter range of 0.5-1.5 mm exhibited an excellent capacity for CO2 adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents. The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles. The presence of mesopores and macropores resulted in appreciable change of volume from CaO (16.7 cm3∙mol−1) to CaCO3 (36.9 cm3∙mol−1) over repeated operation cycles. Ca2Mg1 sorbent pellets exhibited favorable CO2 capture capacity (9.49 mmol∙g−1), average adsorption rate (0.32 mmol∙g−1∙min−1) and conversion rate of CaO (74.83%) after 30 cycles. 相似文献
994.
995.
短路电流中的周期分量和直流分量对系统短路容量都有贡献,而后者在工程应用中没有引起足够的重视.目前我国宁夏、上海、广州等电网普遍面临短路电流直流分量超标,系统保护装置难以可靠清除故障的状况,严重威胁电力系统的安全可靠性.基于此,本文提出使用超导故障限流器在限制短路电流幅值的同时,抑制短路电流直流分量的方法,缓解断路器的开断负担.目前超导限流器对短路电流直流分量的抑制效果及在高直流分量系统超导限流器的设计方法尚不清楚.因此,搭建了超导故障限流器模型,以330 kV系统为例,研究了不同直流分量时间常数下超导限流器阻值与直流分量的关系,提出了超导故障限流器失超阻值的优化设计方法.结果表明在不同的短路故障条件下,超导限流器对直流分量的抑制效果均非常明显,能有效提高系统的可靠性. 相似文献
996.
Bubble/Slurry bubble column reactors(BCR/SBCR) are intensively used as multiphase reactors for a wide range of application in the chemical, biochemical and petrochemical industries. Most of these applications involve complicate gas–liquid/gas–liquid–solid flow behavior and exothermic process, thus it is necessary to equip the BCR/SBCR with heat exchanger tubes to remove the heat and govern the performance of the reactor. Amounts of experimental and numerical studies have been carried out to describe the phenomena taking place in BCR/SBCRs with heat exchanger tubes. Unfortunately, little effort has been put on reviewing the experiments and simulations for examining the effect of internals on the performance and hydrodynamics of BCR/SBCR. The objective of this work is to give a state-of-the-art review of the literature on the effects of heat exchanger tubes with different types and configurations on flow behavior and heat/mass transfer, then provide adequate information and scientific basis for the design and the development of heat exchanger tubes in BCR/SBCR, ultimately provide reasonable suggestions for better comprehend the performance of different heat exchanger tubes on hydrodynamics. 相似文献
997.
Yang Li Defu Che Chenglong Yang Mingyu Yao Tingwen Zhao Kangli Fu Hanchen Zhao 《中国化学工程学报》2021,29(1):401-408
SO2 and NO emitted from coal-fired power plants have caused serious air pollution in China. In this study, a test system for NO oxidation using O3 is established. The basic characteristics of NO oxidation and products forms are studied. A separate test system for the combined removal of SO2 and NOx is also established, and the absorption characteristics of NOx are studied. The characteristics of NO oxidation and NOx absorption were verified in a 35 t·h-1 industrial boiler wet combined desulfurization and denitrification project. The operating economy of ozone oxidation wet denitrification technology is analyzed. The results show that O3 has a high rate and strong selectivity for NO oxidation. When O3 is insufficient, the primary oxidation product is NO2. When O3 is present in excess, NO2 continues to get oxidized to N2O5 or NO3. The removal efficiency of NO2 in alkaline absorption system is low (only about 15%). NOx removal efficiency can be improved by oxidizing NOx to N2O5 or NO3 by increasing ozone ratio. When the molar ratio of O3/NO is 1.77, the NOx removal efficiency reaches 90.3%, while the operating cost of removing NOx per kilogram is 6.06 USD (NO2). 相似文献
998.
In the chemical looping with oxygen uncoupling (CLOU) process,CuO is a promising material due to the high oxygen carrier capacity and exothermic reaction in fuel reactor but limited by the low melting point.The combustion rate of carbon is faster than the decoupling rate of oxygen carrier (OC).Hence,high tem-perature tolerance and rapid oxygen release rate of CuO modified by three different ores were investi-gated in this study.The kinetics analysis of oxygen decoupling with Cu-based oxygen carriers was also evaluated.Results showed that CuO modified by chrysolite had faster oxygen release rate than that of CuO.Limestone showed obvious positive effect on the oxidization process.The selected OCs could keep stable in at least 20 cycles,for about 1200 min.Shrinking core model (SCM) fitted well for the decoupling process in the temperature range of 1123-1223 K.Reduction rate kinetic information may aid in the development of chemical looping with oxygen uncoupling (CLOU) technologies during reactor design and process modeling.Ternary doped copper oxide with chrysolite and limestone could improve the reactivity of CuO in decoupling and coupling process and also improve the high temperature tolerance. 相似文献
999.
Xin Shen Rui Zhang Shuhao Wang Xiang Chen Chuan Zhao Elena Kuzmina Elena Karaseva Vladimir Kolosnitsyn Qiang Zhang 《中国化学工程学报》2021,37(9):137-143
Lithium (Li) metal anodes promise an ultrahigh theoretical energy density and low redox potential,thus being the critical energy material for next-generation batteries.Unfortunately,the formation of Li den-drites in Li metal anodes remarkably hinders the practical applications of Li metal anodes.Herein,the dynamic evolution of discrete Li dendrites and aggregated Li dendrites with increasing current densities is visualized by in-situ optical microscopy in conjunction with ex-situ scanning electron microscopy.As revealed by the phase field simulations,the formation of aggregated Li dendrites under high current den-sity is attributed to the locally concentrated electric field rather than the depletion of Li ions.More specif-ically,the locally concentrated electric field stems from the spatial inhomogeneity on the Li metal surface and will be further enhanced with increasing current densities.Adjusting the above two factors with the help of the constructed phase field model is able to regulate the electrodeposited morphology from aggregated Li dendrites to discrete Li dendrites,and ultimately columnar Li morphology.The methodol-ogy and mechanistic understanding established herein give a significant step toward the practical appli-cations of Li metal anodes. 相似文献
1000.