全文获取类型
收费全文 | 412921篇 |
免费 | 14565篇 |
国内免费 | 6610篇 |
专业分类
电工技术 | 13112篇 |
技术理论 | 9篇 |
综合类 | 8887篇 |
化学工业 | 63384篇 |
金属工艺 | 24529篇 |
机械仪表 | 20073篇 |
建筑科学 | 14592篇 |
矿业工程 | 6363篇 |
能源动力 | 8703篇 |
轻工业 | 23022篇 |
水利工程 | 6644篇 |
石油天然气 | 16611篇 |
武器工业 | 1067篇 |
无线电 | 42830篇 |
一般工业技术 | 82927篇 |
冶金工业 | 47500篇 |
原子能技术 | 10849篇 |
自动化技术 | 42994篇 |
出版年
2022年 | 5740篇 |
2021年 | 7937篇 |
2020年 | 5935篇 |
2019年 | 5678篇 |
2018年 | 14721篇 |
2017年 | 15524篇 |
2016年 | 12364篇 |
2015年 | 7933篇 |
2014年 | 10629篇 |
2013年 | 16986篇 |
2012年 | 16702篇 |
2011年 | 23346篇 |
2010年 | 20380篇 |
2009年 | 19706篇 |
2008年 | 19804篇 |
2007年 | 20779篇 |
2006年 | 12546篇 |
2005年 | 13723篇 |
2004年 | 10688篇 |
2003年 | 10350篇 |
2002年 | 9398篇 |
2001年 | 8557篇 |
2000年 | 7731篇 |
1999年 | 7297篇 |
1998年 | 12576篇 |
1997年 | 9179篇 |
1996年 | 7287篇 |
1995年 | 5713篇 |
1994年 | 4926篇 |
1993年 | 4922篇 |
1992年 | 3999篇 |
1991年 | 3861篇 |
1990年 | 3728篇 |
1989年 | 3600篇 |
1988年 | 3497篇 |
1987年 | 3093篇 |
1986年 | 3072篇 |
1985年 | 3324篇 |
1984年 | 3172篇 |
1983年 | 2998篇 |
1982年 | 2758篇 |
1981年 | 2724篇 |
1980年 | 2773篇 |
1979年 | 2858篇 |
1978年 | 2893篇 |
1977年 | 2987篇 |
1976年 | 3399篇 |
1975年 | 2673篇 |
1974年 | 2557篇 |
1973年 | 2654篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Multicomponent Diamond-Like Semiconductors Based on the InBV–CdS System: Bulk and Surface Properties
Semiconductors - According to developed methods, in the fields of the mutual solubility of initial binary compounds (InP, InSb, and CdS), solid solutions of the InP–CdS and InSb–CdS... 相似文献
62.
In the present work, two types of shear thickening fluids have been synthesized by using neat and aminosilane functionalized silica nanoparticles and their viscosity curves have been obtained by the rheometer. Based on the values of peak viscosity of synthesized shear thickening fluids, the surface functionalized nanosilica based shear thickening fluid has been chosen as a best candidate due to the high viscosity for impregnation into the neat Kevlar of different layers viz. four (04) and eight (08) layers for velocity impact study. The experimental investigations reveal high energy absorption of shear thickening fluid impregnated Kevlar as compared to the neat Kevlar. The maximum energy absorption 62 J is achieved corresponding to the initial velocity 154 m∙s−1 for 08 layers shear thickening fluid impregnated Kevlar specimen. The data have also been analytically determined and validated with the experimental data. The experimental data have good agreement with the analytical data within the accuracy of around 15 to 20%. The present findings can have significant inferences towards the fabrication of shear thickening fluids using nanomaterials for numerous applications such as soft armors, dampers, nanofinishing and so forth. 相似文献
63.
Chemical and Petroleum Engineering - The processes of separation of impurities of particles of different sizes are analyzed under conditions of irregularity of structural and kinematic parameters... 相似文献
64.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs. 相似文献
65.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
66.
Golubev N. V. Ignat’eva E. S. Maurus A. A. Ziyatdinova M. Z. Lopatina E. V. Lorenzi R. Paleari A. Sigaev V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence... 相似文献
67.
安全仪表功能(SIF)回路是为了降低特定场景的安全风险而设置的,定级报告中SIF回路的功能描述是工艺设计的完整逻辑要求,包含关键动作及附件动作。安全完整性等级(SIL)验证属于概率学领域研究范畴,影响失效率的因素多且复杂。如果SIL验证无法通过,将造成大量的设计变更,浪费工程投资,影响工期。设计人员应关注SIL定级报告中关键动作的识别、要求平均失效概率以及SIF回路架构的约束。按照文中方法优化测量元件、逻辑控制器、执行元件及辅助元件的设计,可增加通过验证的概率。在没有预验证及安全要求规格书时,可以参考文中典型可通过SIL验证的SIF回路的经验架构进行优化设计,以减少工程变更。 相似文献
68.
In this communication, the structural, micro-structural, dielectric, electrical, magnetic, and leakage-current characteristics of a double perovskite (Y2CoMnO6) ceramic material have been reported. The material was synthesized via a high-temperature mixed-oxide route. The compound crystallizes in a monoclinic structure which is confirmed from preliminary X-ray structural study. The morphological study by using scanning electron micrograph reveals the almost homogeneous distribution of grains throughout the surface of the sample. The nature of frequency-dependence of dielectric constant has been described by the Maxwell-Wagner model. The occurrence of a dielectric anomaly in the temperature dependence of dielectric permittivity study demonstrates the ferroelectric-paraelectric phase transition in the material. From the Nyquist plots, we found the existence of both grain and grain boundary effects. The frequency dependence of conductivity was studied by the Jonscher’s Power law, and the conduction phenomenon obeys the large overlapping polaron tunneling model. By using the Arrhenius equation, the activation energy has been calculated which is nearly equal to the energy required for the hoping of the electron. Both impedance and conductivity analysis demonstrate that the sample exhibits negative temperature coefficient of resistance (NTCR) properties indicating the semiconducting type of material at high temperatures. The anti-ferromagnetic character of the material is observed from the nature of magnetic hysteresis loop. The leakage current analysis suggests that the conduction process in the material follows the space charge limited conduction phenomenon. Such material will be helpful for modern electronic devices and spintronic applications. 相似文献
69.
Popov N. N. Presnyakov D. V. Lar’kin V. F. 《Journal of Machinery Manufacture and Reliability》2020,49(3):232-236
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing... 相似文献
70.
Wei Shaowei Yu Guoxian Wang Jun Domeniconi Carlotta Zhang Xiangliang 《Machine Learning》2021,110(6):1505-1526
Machine Learning - Traditional clustering algorithms focus on a single clustering result; as such, they cannot explore potential diverse patterns of complex real world data. To deal with this... 相似文献