全文获取类型
收费全文 | 468802篇 |
免费 | 37423篇 |
国内免费 | 19416篇 |
专业分类
电工技术 | 27183篇 |
技术理论 | 62篇 |
综合类 | 30094篇 |
化学工业 | 75685篇 |
金属工艺 | 26617篇 |
机械仪表 | 30739篇 |
建筑科学 | 37202篇 |
矿业工程 | 15214篇 |
能源动力 | 13479篇 |
轻工业 | 28255篇 |
水利工程 | 8291篇 |
石油天然气 | 30206篇 |
武器工业 | 4018篇 |
无线电 | 53520篇 |
一般工业技术 | 54030篇 |
冶金工业 | 24267篇 |
原子能技术 | 4775篇 |
自动化技术 | 62004篇 |
出版年
2024年 | 746篇 |
2023年 | 6846篇 |
2022年 | 10961篇 |
2021年 | 17364篇 |
2020年 | 13719篇 |
2019年 | 11140篇 |
2018年 | 12821篇 |
2017年 | 14629篇 |
2016年 | 13136篇 |
2015年 | 17908篇 |
2014年 | 23033篇 |
2013年 | 27819篇 |
2012年 | 29964篇 |
2011年 | 33287篇 |
2010年 | 28647篇 |
2009年 | 27549篇 |
2008年 | 26946篇 |
2007年 | 25805篇 |
2006年 | 26568篇 |
2005年 | 23082篇 |
2004年 | 15102篇 |
2003年 | 13035篇 |
2002年 | 11708篇 |
2001年 | 10684篇 |
2000年 | 11029篇 |
1999年 | 12723篇 |
1998年 | 10686篇 |
1997年 | 8913篇 |
1996年 | 8324篇 |
1995年 | 7024篇 |
1994年 | 5811篇 |
1993年 | 4174篇 |
1992年 | 3279篇 |
1991年 | 2630篇 |
1990年 | 1982篇 |
1989年 | 1635篇 |
1988年 | 1327篇 |
1987年 | 845篇 |
1986年 | 674篇 |
1985年 | 442篇 |
1984年 | 289篇 |
1983年 | 246篇 |
1982年 | 268篇 |
1981年 | 174篇 |
1980年 | 174篇 |
1979年 | 102篇 |
1978年 | 55篇 |
1977年 | 58篇 |
1976年 | 84篇 |
1975年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
电视台信息技术系统运维服务管理体系的正常运行,不但可以有效控制播控系统的运行质量,而且能够为演播室的节目录制工作提供必要的技术支撑.基于此,概括总结电视台信息技术系统运维服务管理体系的设计理念和实践情况,论述电视台信息技术系统运维服务管理体系的发展对策. 相似文献
102.
教学行为分析作是教学质量分析的重要组成部分,也是教学引导与反馈机制的重要依据。文章阐述了人工智能(AI)的含义及发展历程,重点分析总结了教学行为分析方法及AI在教学行为分析上的应用。文章以东南大学电工电子在线实验为研究平台,探索分析了AI技术在实验教学行为分析上的可行性,梳理了基于专家系统的在线实验分析系统的设计思路,充分探讨了“智能”教育在实验教学中的深刻内涵。 相似文献
103.
王坤 《安徽电子信息职业技术学院学报》2021,20(3):24-26
介绍一种用于婴儿培养箱上的加湿模块,具有稳定控制湿度、持续动态补水、方便消毒维护、安全可靠等优点,采用电加热加湿方式,产生高温水蒸气,不易滋生细菌。水蒸气进入婴儿培养箱空气循环系统后,充分扩散,加湿效果更加均匀。 相似文献
104.
Peiying Wang Juanli Zhao Yun Fan Wei Zhang Yuanyuan Cui Liangmiao Zhang Bin Liu Hongqiang Nian Yiran Li 《Ceramics International》2021,47(11):15023-15029
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity. 相似文献
105.
Zhongchao Fu Xiaodong Li Mu Zhang Qi Zhu Ji-Guang Li Jiao He Xing'an Wang Xudong Sun 《Journal of the American Ceramic Society》2021,104(6):2689-2701
An easy albeit quite effective deionization suspension treatment was adopted to alleviate the detrimental effects related to the hydrolysis of Y2O3 in an aqueous medium. Fabrication of highly transparent Y2O3 ceramics with a fine grain size via air pre-sintering and post–hot isostatic pressing (HIP) treatment without using any sintering additive was achieved using the treated suspensions. The hydrolysis issue of Y2O3 powder in an aqueous medium was effectively alleviated by using deionization treatment, and a well-dispersed suspension with a low concentration of dissolved Y3+ species was obtained. The dispersed suspensions were consolidated by the centrifugal casting method, and the green bodies derived from the suspension of 35.0 vol% solid loading showed an improved homogeneity with a relative density of 52.1%. Fully dense Y2O3 transparent ceramic with high transparency was obtained by pre-sintering consolidated green compacts at a low temperature of 1400°C for 16 h in air followed by a post-HIP treatment at 1550°C for 2 h under 200 MPa pressure. The sample had a fine average grain size of 690 nm. The in-line transmittance of the sample reached 83.3% and 81.8% at 1100 nm and 800 nm, respectively, very close to the theoretical values of Y2O3. 相似文献
106.
Qianying Hoo Xiaohu Wang Feng Yuan Xuewei Cao Tiewa Cao Maolin Zhang 《Journal of the European Ceramic Society》2021,41(6):3816-3822
Jingdezhen is famous for its bluish white (Qingbai) porcelains of the Song Dynasty, and those decorated with iron spots are distinctive among them. Herein, iron spots on a bluish white porcelain were investigated using a series of microscopic and spectroscopic characterizations. We found the decreasing iron content from more than 8 wt% to about 2 wt% during the glaze color transition from rusty to brown and finally into green, which built a connection on the coloring mechanism of iron-rich crystallized glaze and celadon glaze. We identified the rare ε-Fe2O3, a promising magnetic material, in both the dark brown crystals and the triangular crystals in the rusty area, which is its first discovery among bluish white porcelains. Based on these findings, we discussed the coloring mechanism of iron-spot decoration along with the physical form of the iron oxide crystals, indicating the partially reducing atmosphere during firing process. 相似文献
107.
Han Chen Shunzo Shimai Jin Zhao Xiaojian Mao Jian Zhang Guohong Zhou Shiwei Wang 《Journal of the European Ceramic Society》2021,41(6):3838-3843
Alumina platelets were arranged horizontally in submicron alumina particles by shear force in the flow of slurries during casting. The obtained alumina green bodies with platelets were pressureless-sintered in vacuum, producing ceramics with thoroughly oriented grains and high transmittance. The effects of sintering parameters on the densification, microstructure evolution, and orientation degree of alumina ceramics were investigated and discussed. The results showed that the densification, grain size, orientation degree, and in-line transmittance were increased with increasing sintering temperature. The enhancement of orientation degree was mainly coherent with grain growth. The grain-oriented samples exhibited a much higher in-line transmittance (at 600 nm) of 61 % than that of the grain random sample (29 %). Moreover, the transmission remained a high level in the ultraviolet range (<300 nm). 相似文献
108.
Hengtao Wang Hui Chen Weicheng Xie Hanjian Lai Tingxing Zhao Yulin Zhu Lin Chen Chunxian Ke Nan Zheng Feng He 《Advanced functional materials》2021,31(26):2100877
The design of polymer acceptors plays an essential role in the performance of all-polymer solar cells. Recently, the strategy of polymerized small molecules has achieved great success, but most polymers are synthesized from the mixed monomers, which seriously affects batch-to-batch reproducibility. Here, a method to separate γ-Br-IC or δ-Br-IC in gram scale and apply the strategy of monomer configurational control in which two isomeric polymeric acceptors (PBTIC-γ-2F2T and PBTIC-δ-2F2T) are produced is reported. As a comparison, PBTIC-m-2F2T from the mixed monomers is also synthesized. The γ-position based polymer (PBTIC-γ-2F2T) shows good solubility and achieves the best power conversion efficiency of 14.34% with a high open-circuit voltage of 0.95 V when blended with PM6, which is among the highest values recorded to date, while the δ-position based isomer (PBTIC-δ-2F2T) is insoluble and cannot be processed after parallel polymerization. The mixed-isomers based polymer, PBTIC-m-2F2T, shows better processing capability but has a low efficiency of 3.26%. Further investigation shows that precise control of configuration helps to improve the regularity of the polymer chain and reduce the π–π stacking distance. These results demonstrate that the configurational control affords a promising strategy to achieve high-performance polymer acceptors. 相似文献
109.
Tianxing Chen Tengteng Yao Hui Peng Andrew K. Whittaker Yao Li Shenmin Zhu Zhaoyang Wang 《Advanced functional materials》2021,31(45):2106079
The convenience of injectable hydrogels that can provide high loading of diverse phototherapy agents and further long-time retention at the tumor site has attracted tremendous interest in simultaneous photothermal and photodynamic cancer therapies. However, to incorporate the phototherapy agents into hydrogels, complex modifications are generally unavoidable. Moreover, these phototherapy agents usually suffer from low efficiency and work at different irradiation wavelengths outside the near infrared windows. Hence, a method for the fabrication of an injectable hydrogel for simultaneous photothermal therapy and photodynamic therapy, through the Schiff-base reaction between amido modified carbon dots (NCDs) and aldehyde modified cellulose nanocrystals is proposed. The NCDs act as both phototherapy agents and crosslinkers to form hydrogels. Significantly, the NCDs demonstrate an extremely high photothermal conversion efficiency of 77.6% which is among the highest levels for photothermal agents and a high singlet quantum yield of 0.37 under a single 660 nm light-emitting diode irradiation. The hydrogels are examined through in vitro and in vivo animal experiments which show nontoxic and effectively tumor inhibition. Thus, the strategy of direct reaction of phototherapy agents and the matrix not only provides new strategies for injectable hydrogel fabrication but paves a new road for advanced tumor treatment. 相似文献
110.
Lingping Kong Jue Gong Qingyang Hu Francesco Capitani Anna Celeste Takanori Hattori Asami Sano-Furukawa Nana Li Wenge Yang Gang Liu Ho-kwang Mao 《Advanced functional materials》2021,31(9):2009131
The soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. Here, using the methylammonium lead iodide as a representative exploratory platform, it is observed that the pressure-driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By a comprehensive in situ neutron/synchrotron-based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD3ND3PbI3, which also shows much greater structural robustness with retainable PL after high peak-pressure compression–decompression cycle. With the first-principles calculations, an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics is proposed, where the less dynamic CD3ND3+ cations are vital to maintain the long-range crystalline order through steric and Coulombic interactions. These results also show that CD3ND3PbI3-based solar cell has comparable photovoltaic performance as CH3NH3PbI3-based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope-functionalized perovskite materials for better materials-by-design and more stable photovoltaic application. 相似文献