全文获取类型
收费全文 | 568568篇 |
免费 | 10102篇 |
国内免费 | 2967篇 |
专业分类
电工技术 | 11448篇 |
技术理论 | 3篇 |
综合类 | 4374篇 |
化学工业 | 81744篇 |
金属工艺 | 24984篇 |
机械仪表 | 21831篇 |
建筑科学 | 16922篇 |
矿业工程 | 2885篇 |
能源动力 | 13411篇 |
轻工业 | 48793篇 |
水利工程 | 5692篇 |
石油天然气 | 5087篇 |
武器工业 | 230篇 |
无线电 | 72065篇 |
一般工业技术 | 109391篇 |
冶金工业 | 82902篇 |
原子能技术 | 7113篇 |
自动化技术 | 72762篇 |
出版年
2021年 | 3943篇 |
2020年 | 2772篇 |
2019年 | 3210篇 |
2018年 | 24153篇 |
2017年 | 23987篇 |
2016年 | 17150篇 |
2015年 | 5475篇 |
2014年 | 7253篇 |
2013年 | 21030篇 |
2012年 | 16618篇 |
2011年 | 31369篇 |
2010年 | 26528篇 |
2009年 | 25083篇 |
2008年 | 26381篇 |
2007年 | 29221篇 |
2006年 | 14371篇 |
2005年 | 17608篇 |
2004年 | 14957篇 |
2003年 | 14309篇 |
2002年 | 12641篇 |
2001年 | 11895篇 |
2000年 | 11245篇 |
1999年 | 11562篇 |
1998年 | 24650篇 |
1997年 | 18107篇 |
1996年 | 14429篇 |
1995年 | 11397篇 |
1994年 | 10124篇 |
1993年 | 9628篇 |
1992年 | 7349篇 |
1991年 | 6849篇 |
1990年 | 6396篇 |
1989年 | 6073篇 |
1988年 | 5818篇 |
1987年 | 4840篇 |
1986年 | 4789篇 |
1985年 | 5920篇 |
1984年 | 5536篇 |
1983年 | 4773篇 |
1982年 | 4441篇 |
1981年 | 4398篇 |
1980年 | 4139篇 |
1979年 | 4029篇 |
1978年 | 3725篇 |
1977年 | 4501篇 |
1976年 | 6055篇 |
1975年 | 3084篇 |
1974年 | 2973篇 |
1973年 | 2851篇 |
1972年 | 2291篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The Interplay of Modulus,Strength, and Ductility in Adhesive Design Using Biomimetic Polymer Chemistry 下载免费PDF全文
High‐performance adhesives require mechanical properties tuned to demands of the surroundings. A mismatch in stiffness between substrate and adhesive leads to stress concentrations and fracture when the bonding is subjected to mechanical load. Balancing material strength versus ductility, as well as considering the relationship between adhesive modulus and substrate modulus, creates stronger joints. However, a detailed understanding of how these properties interplay is lacking. Here, a biomimetic terpolymer is altered systematically to identify regions of optimal bonding. Mechanical properties of these terpolymers are tailored by controlling the amount of a methyl methacrylate stiff monomer versus a similar monomer containing flexible poly(ethylene glycol) chains. Dopamine methacrylamide, the cross‐linking monomer, is a catechol moiety analogous to 3,4‐dihydroxyphenylalanine, a key component in the adhesive proteins of marine mussels. Bulk adhesion of this family of terpolymers is tested on metal and plastic substrates. Incorporating higher amounts of poly(ethylene glycol) into the terpolymer introduces flexibility and ductility. By taking a systematic approach to polymer design, the region in which material strength and ductility are balanced in relation to the substrate modulus is found, thereby yielding the most robust joints. 相似文献
82.
Qilin Liu Feng Ding 《International Journal of Adaptive Control and Signal Processing》2021,35(10):1970-1989
The identification of the Hammerstein–Wiener (H-W) systems based on the nonuniform input–output dataset remains a challenging problem. This article studies the identification problem of a periodically nonuniformly sampled-data H-W system. In addition, the product terms of the parameters in the H-W system are inevitable. In order to solve the problem, the key-term separation is applied and two algorithms are proposed. One is the key-term-based forgetting factor stochastic gradient (KT-FFSG) algorithm based on the gradient search. The other is the key-term-based hierarchical forgetting factor stochastic gradient (KT-HFFSG) algorithm. Compared with the KT-FFSG algorithm, the KT-HFFSG algorithm gives more accurate estimates. The simulation results indicate that the proposed algorithms are effective. 相似文献
83.
Carmen J. Pastor-Maldonado Juan M. Surez-Rivero Suleva Povea-Cabello Mnica lvarez-Crdoba Irene Villaln-García Manuel Munuera-Cabeza Alejandra Surez-Carrillo Marta Talavern-Rey Jos A. Snchez-Alczar 《International journal of molecular sciences》2020,21(22)
The aim of this review is to shed light over the most recent advances in Coenzyme Q10 (CoQ10) applications as well as to provide detailed information about the functions of this versatile molecule, which have proven to be of great interest in the medical field. Traditionally, CoQ10 clinical use was based on its antioxidant properties; however, a wide range of highly interesting alternative functions have recently been discovered. In this line, CoQ10 has shown pain-alleviating properties in fibromyalgia patients, a membrane-stabilizing function, immune system enhancing ability, or a fundamental role for insulin sensitivity, apart from potentially beneficial properties for familial hypercholesterolemia patients. In brief, it shows a remarkable amount of functions in addition to those yet to be discovered. Despite its multiple therapeutic applications, CoQ10 is not commonly prescribed as a drug because of its low oral bioavailability, which compromises its efficacy. Hence, several formulations have been developed to face such inconvenience. These were initially designed as lipid nanoparticles for CoQ10 encapsulation and distribution through biological membranes and eventually evolved towards chemical modifications of the molecule to decrease its hydrophobicity. Some of the most promising formulations will also be discussed in this review. 相似文献
84.
Hammons Joshua A. Tumey Scott J. Idell Yaakov Jeffries Jason R. 《JOM Journal of the Minerals, Metals and Materials Society》2020,72(1):176-186
JOM - Alpha-radiation damage in metals is a concern for long-term radioactive storage and systems that produce nuclear energy. Accurate prediction of irradiated material properties and failure... 相似文献
85.
86.
87.
88.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
89.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
90.