全文获取类型
收费全文 | 51605篇 |
免费 | 4680篇 |
国内免费 | 2499篇 |
专业分类
电工技术 | 2986篇 |
技术理论 | 4篇 |
综合类 | 3543篇 |
化学工业 | 8463篇 |
金属工艺 | 2744篇 |
机械仪表 | 3305篇 |
建筑科学 | 4344篇 |
矿业工程 | 1484篇 |
能源动力 | 1609篇 |
轻工业 | 2974篇 |
水利工程 | 1017篇 |
石油天然气 | 3620篇 |
武器工业 | 472篇 |
无线电 | 5992篇 |
一般工业技术 | 6151篇 |
冶金工业 | 2255篇 |
原子能技术 | 701篇 |
自动化技术 | 7120篇 |
出版年
2024年 | 225篇 |
2023年 | 766篇 |
2022年 | 1391篇 |
2021年 | 1959篇 |
2020年 | 1481篇 |
2019年 | 1311篇 |
2018年 | 1413篇 |
2017年 | 1653篇 |
2016年 | 1468篇 |
2015年 | 1874篇 |
2014年 | 2418篇 |
2013年 | 2903篇 |
2012年 | 3008篇 |
2011年 | 3364篇 |
2010年 | 2872篇 |
2009年 | 2763篇 |
2008年 | 2796篇 |
2007年 | 2656篇 |
2006年 | 2770篇 |
2005年 | 2382篇 |
2004年 | 1702篇 |
2003年 | 1902篇 |
2002年 | 2140篇 |
2001年 | 1879篇 |
2000年 | 1554篇 |
1999年 | 1621篇 |
1998年 | 1167篇 |
1997年 | 1007篇 |
1996年 | 978篇 |
1995年 | 766篇 |
1994年 | 660篇 |
1993年 | 502篇 |
1992年 | 333篇 |
1991年 | 262篇 |
1990年 | 192篇 |
1989年 | 168篇 |
1988年 | 168篇 |
1987年 | 100篇 |
1986年 | 59篇 |
1985年 | 41篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 22篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1976年 | 1篇 |
1971年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 5 毫秒
991.
Dong Seop Kim Shi Yul Kim BYung Tae Ahn Ho Bin Im 《Journal of Materials Science: Materials in Electronics》1994,5(1):17-21
Polycrystalline CdS/CdTe solar cells have been prepared by coating and sintering a CdS slurry and a (Cd+Te) slurry. CdS layers were first formed on borosilicate glass substrates at 600°C in nitrogen and then CdTe layers were formed on the sintered CdS layers at 625°C in nitrogen. The (Cd+Te) slurry contained (Cd+Te) powders mixed in a ball mill for 12–220 h instead of more expensive CdTe powders. The shape of cadmium particles changed from spherical to plate-like and the diameter of the plate-shaped particles became smaller as the ball-milling time increased. In addition, a compound CdTe started to form during a long milling time. The sintered CdTe layers were more compact as the diameter of plate-shaped cadmium particles decreased. However, cracks developed in the sintered CdTe layer when the diameter was small ( 2 m). The efficiency of sintered CdS/CdTe solar cells increased with decreasing particle diameter and then decreased with further decrease in particle diameter. The highest efficiency of 12.1% was achieved using a mixture of (Cd+Te) powders which had plate-shaped cadmium particles with a diameter of 5 m. The results suggest that high-efficiency sintered CdS/CdTe solar cells can be fabricated by using CdTe slurry from the mixture of (Cd+Te) powders with an inexpensive ball-milling process. 相似文献
992.
聚砜类原位复合材料加工流变性 总被引:3,自引:0,他引:3
合成了含4,4'-二羟基联苯和4,4'-二羟基二苯基甲烷结构的两种液晶共聚酯BP-LCP和BPM-LCP,将其与聚砜共混制备原位复合材料。探讨了共混物在Haake转矩流变仪中密炼时转矩的变化;通过毛细管挤出考察了液晶共聚酯分子结构、分子量及含量变化对原位复合材料流变性能的影响,由流动曲线获得这一类原位复合材料熔体大部分表现为假塑料性非牛顿型流体,但含低分子量BP-LCP20%和BPM-LCP30%的两种原位复合熔体均表现出特殊的流变性:较低剪切速率时为胀塑性流体,较高剪切速率时为假塑性流体。分析了这种现象与液晶共聚酯结构形态的关系。并讨论了增强组份和基体的相容性对原位复合材料流变性的影响。 相似文献
993.
压缩应力下(Tb,Dy)Fe2磁致伸缩的研究 总被引:5,自引:0,他引:5
本文利用自制的磁致伸缩测量仪和“jump”效应测量仪研究了在一定压强了多晶(Tb、Dy)Fe2棒的磁致伸缩,发现加压时,在一定工艺条件下制作的(Tb、Dy)Fe2棒会有磁致伸缩的变化。卸载后经过热处理,磁致伸缩值在不加压时也会维持一个高值。 相似文献
994.
995.
Shapiro DB Maestre MF McClain WM Hull PG Shi Y Quinby-Hunt MS Hearst JE Hunt AJ 《Applied optics》1994,33(24):5733-5744
The coupled-dipole approximation has been used to model polarized light-scattering data obtained from the sperm of the octopus Eledone cirrhosa. Mueller scattering-matrix elements (which describe how a sample alters the intensity and degree of polarization of scattered light) were measured as a function of angle. The sample was modeled as a helical fiber believed to correspond to a DNA protein complex. It was necessary to propose an inherent anisotropy in the polarizability of the fiber in order to fit the data. The direction of the principle axes of the polarizability were determined by comparing the model with experimental data. The results suggest that the 2-nm DNA fibers are perpendicular to the thick fiber that defines the helical geometry of the octopus sperm head. 相似文献
996.
Shi CX 《Applied optics》1994,33(30):7002-7008
The periodic mode coupling between the x- and y-polarization modes that is induced by a photoinduced birefringent fiber grating is analyzed through the use of the coupled-mode theory. A novel Fabry-Perot resonator composed of a photoinduced birefringent fiber grating is proposed and theoretically investigated. In the ideal case, the x- and y-polarization resonances of the resonator coincide with each other because of the polarization power exchange by the photoinduced birefringent grating, which results in the total resonator output's being polarization independent. However, if there are some external perturbations (e.g., temperature change or strain), the phase matching is detuned, which could destroy the coincidence between the two polarization resonances, which can further result in the total output resonance's having two peaks. The separation between these two resonant peaks depends on perturbations of the environment (temperature changes or strain). 相似文献
997.
Cyclic deformations of annealed pure polycrystalline -iron with and without further mutually immiscible silver-ion implantation (90 keV, 6×1016 ions cm–2) were studied in a plastic strain-controlled tension-compression fatigue test (triangular loading waveform, frequency 0.02–0.3 Hz, and plastic strain range 3×10–3–1.2×10–2). The obtained plastic strain-life (p-N
f) curves showed that the iron specimens could survive for a greater number of cycles before failure when implanted. Comparison of the cyclic stress-strain curves suggested that the implanted specimens had maintained a relatively more stable microstructural change than those unimplanted ones which had undergone a violent cyclic hardening during cyclic deformation. This is proposed to be a strong indication that the fatigue ductility has been improved and the cross slip of screw dislocations, which leads to the evolution of the persistent slip bands for fatigue damage, was hindered to some extent after ion implantation. 相似文献
998.
Z. X. Shi H. L. Ji X. Jin X. X. Yao H. C. Li X. S. Rong 《Journal of Superconductivity》1995,8(2):241-245
Magnetization measurements have been performed onc-axis oriented Y- and Gd-based superconductive films in a wide range of the temperaturesT (4.2–85 K) and magnetic fieldsH (0–8 T) withH c-axis. The influence of flux creep on both the temperature dependence of critical current densityJ
cm
and the scaling behavior of flux pinning forceF
p
has been discussed in detail. The experimental results show that Y and Gd films have different pinning mechanism. Flux pinning-force peaks in high fields are observed in Gd film at high temperatures and can be considered as evidence for collective pinning. 相似文献
999.
Huanran Zheng Shibin Wang Shoujie Liu Jiao Wu Jianping Guan Qian Li Yuchao Wang Yu Tao Shouyao Hu Yu Bai Jinxian Wang Xiang Xiong Yu Xiong Yongpeng Lei 《Advanced functional materials》2023,33(40):2300815
The rational design and construction of efficient and inexpensive bifunctional oxygen electrocatalysts are highly desirable for the development of rechargeable Zn–air batteries (ZABs). Although single-atom Fe sites anchored on N-doped carbon catalysts (Fe1/NC) ensure high oxygen reduction reaction activity, their unitary atomically dispersed active center faces difficult condition in catalyzing oxygen evolution reaction simultaneously. Herein, a composite catalyst containing heterointerface between Fe1/NC and selenides ((Fe,Co)Se2) is constructed. The obtained (Fe,Co)Se2@Fe1/NC exhibits extremely narrow potential gap of 0.616 V and remarkable stability in alkaline media, outperforming the benchmark catalysts (Pt/C+RuO2: 0.720 V). Experimental results and density functional theory calculations reveal that heterointerface between Fe1/NC and (Fe,Co)Se2 accelerates the electron transfer and provides more moderate adsorption sites, which endow (Fe,Co)Se2@Fe1/NC with extremely high bifunctional oxygen catalytic activity. This study not only provides a superior bifunctional catalyst for ZABs, but also enriches the application of single-atom catalysts in multifunctional energy storage and conversion devices. 相似文献
1000.
Fangchao Li Xuliang Zhang Junwei Shi Lujie Jin Jiawei Qiao Junjun Guo Hang Yin Youyong Li Jianyu Yuan Wanli Ma 《Advanced functional materials》2023,33(40):2302542
Organic–inorganic formamidinium lead triiodide (FAPbI3) hybrid perovskite quantum dot (QD) is of great interest to photovoltaic (PV) community due to its narrow band gap, higher ambient stability, and long carrier lifetime. However, the surface ligand management of FAPbI3 QD is still a key hurdle that impedes the design of high-efficiency solar cells. Herein, this study first develops a solution-mediated ligand exchange (SMLE) for preparing FAPbI3 QD film with enhanced electronic coupling. By dissolving optimal methylammonium iodide (MAI) into antisolvent to treat the FAPbI3 QD solution, the SMLE can not only effectively replace the long-chain ligands, but also passivate the A- and X-site vacancies. By combining experimental and theoretical results, this study demonstrates that the SMLE engineered FAPbI3 QD exhibits lower defect density, which is beneficial for fabricating high-quality QD arrays with desired morphology and carrier transport. Consequently, the SMLE FAPbI3 QD based solar cell outputs a champion efficiency of 15.10% together with improved long-term ambient storage stability, which is currently the highest reported value for hybrid perovskite QD solar cells. These results would provide new design principle of hybrid perovskite QDs toward high-performance optoelectronic application. 相似文献