全文获取类型
收费全文 | 569559篇 |
免费 | 7118篇 |
国内免费 | 1825篇 |
专业分类
电工技术 | 11617篇 |
综合类 | 856篇 |
化学工业 | 80877篇 |
金属工艺 | 24742篇 |
机械仪表 | 19841篇 |
建筑科学 | 14030篇 |
矿业工程 | 1986篇 |
能源动力 | 14124篇 |
轻工业 | 49818篇 |
水利工程 | 5058篇 |
石油天然气 | 5948篇 |
武器工业 | 11篇 |
无线电 | 70727篇 |
一般工业技术 | 111327篇 |
冶金工业 | 104933篇 |
原子能技术 | 9347篇 |
自动化技术 | 53260篇 |
出版年
2021年 | 3501篇 |
2019年 | 3320篇 |
2018年 | 13011篇 |
2017年 | 13455篇 |
2016年 | 9761篇 |
2015年 | 4642篇 |
2014年 | 7068篇 |
2013年 | 23277篇 |
2012年 | 14149篇 |
2011年 | 24039篇 |
2010年 | 20362篇 |
2009年 | 21084篇 |
2008年 | 21656篇 |
2007年 | 23477篇 |
2006年 | 14322篇 |
2005年 | 16561篇 |
2004年 | 14587篇 |
2003年 | 13994篇 |
2002年 | 13046篇 |
2001年 | 12772篇 |
2000年 | 12049篇 |
1999年 | 12834篇 |
1998年 | 31738篇 |
1997年 | 22540篇 |
1996年 | 16905篇 |
1995年 | 13212篇 |
1994年 | 11960篇 |
1993年 | 11537篇 |
1992年 | 8448篇 |
1991年 | 8181篇 |
1990年 | 7737篇 |
1989年 | 7415篇 |
1988年 | 7295篇 |
1987年 | 6059篇 |
1986年 | 6184篇 |
1985年 | 7373篇 |
1984年 | 6619篇 |
1983年 | 6099篇 |
1982年 | 5539篇 |
1981年 | 5699篇 |
1980年 | 5300篇 |
1979年 | 5099篇 |
1978年 | 4880篇 |
1977年 | 6052篇 |
1976年 | 8295篇 |
1975年 | 4200篇 |
1974年 | 4058篇 |
1973年 | 4045篇 |
1972年 | 3364篇 |
1971年 | 2945篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Semiconductors - We found bulk n-GaAs layers grown by liquid phase epitaxy to be irregularly stressed. Deformation created by this stress causes a small but detectable quadrupole splitting of... 相似文献
82.
Bakhale Mugdha Hemalatha V. Dhanalakshmi Samiappan Kumar R. Siddharth Jain M. 《Wireless Personal Communications》2020,110(2):573-592
Wireless Personal Communications - A relatively new area of research and development is Swarm Robotics. It is a part of the swarm intelligence field. In the proposed paper, we shall use swarm... 相似文献
83.
Giorgio Benedek Joseph R. Manson Salvador Miret-Artés 《Advanced materials (Deerfield Beach, Fla.)》2020,32(25):2002072
Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision. 相似文献
84.
Madhu H. C. Edachery Vimal Lijesh K. P. Perugu Chandra Shekhar Kailas Satish V. 《Metallurgical and Materials Transactions A》2020,51(8):4086-4099
Metallurgical and Materials Transactions A - Hybrid nanocomposites have potential as wear-resistant materials. However, synthesizing these nanocomposites by conventional molten state methods result... 相似文献
85.
Anjan Biswas Sonmezoglu Abdullah Ekici Mehmet Alzahrani Abdullah Khamis Belic Milivoj R. 《Journal of Communications Technology and Electronics》2020,65(12):1384-1398
Journal of Communications Technology and Electronics - This paper implements mathematically rigorous extended trial function algorithm to address cubic–quartic optical solitons in... 相似文献
86.
E. M. Godzhaev R. A. Bairamov R. A. Abbasov 《Surface Engineering and Applied Electrochemistry》2015,51(6):552-556
The paper describes the results of a study on the temperature and frequency dependences of the dielectric permeability and dielectric loss tangent of composite materials composed of low density polyethylene filled with cadmium sulfide (LDPE/CdS) and indium(III) selenide (LDPE/In2Se3) in the temperature range of 300–450 K and a frequency range of 0–1014 Hz. It is revealed that a variation in the filler content and the effect of external factors can yield novel composite materials with desired dielectric characteristics. 相似文献
87.
88.
89.
Dr. Jiayao Y. Wang Dr. Jiaqi Q. Li Prof. Dr. Yumei M. Xiao Prof. Dr. Bin Fu Prof. Dr. Zhaohai H. Qin 《ChemMedChem》2020,15(5):404-410
Mitochondrial oxidative damage and dysfunction contribute to a wide range of human diseases. Considering the limitation of conventional antioxidants and that mitochondria are the main source of reactive oxygen species (ROS) which induce oxidative damage, mitochondria-targeted antioxidants which can selectively block mitochondrial oxidative damage and prevent various types of cell death have been widely developed. As a lipophilic cation, triphenylphosphonium (TPP) has been commonly used in designing mitochondria-targeted antioxidants. Conjugated with the TPP moiety, antioxidants can achieve more than 1000-fold higher mitochondrial concentration depending on cell membrane potentials and mitochondrial membrane potentials. Herein we discuss the deficiencies of conventional antioxidants and the advantages of mitochondrial targeting, and review various types of TPP-based mitochondria-targeted antioxidants. These provide theoretical and background support for the design of new anti-oxidant. 相似文献
90.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity. 相似文献