全文获取类型
收费全文 | 90762篇 |
免费 | 1137篇 |
国内免费 | 771篇 |
专业分类
电工技术 | 2029篇 |
综合类 | 148篇 |
化学工业 | 13515篇 |
金属工艺 | 4452篇 |
机械仪表 | 4014篇 |
建筑科学 | 1915篇 |
矿业工程 | 760篇 |
能源动力 | 1971篇 |
轻工业 | 6855篇 |
水利工程 | 1180篇 |
石油天然气 | 3008篇 |
武器工业 | 52篇 |
无线电 | 8933篇 |
一般工业技术 | 20304篇 |
冶金工业 | 14071篇 |
原子能技术 | 2962篇 |
自动化技术 | 6501篇 |
出版年
2022年 | 752篇 |
2021年 | 1308篇 |
2020年 | 1011篇 |
2019年 | 1218篇 |
2018年 | 2417篇 |
2017年 | 2483篇 |
2016年 | 2794篇 |
2015年 | 1573篇 |
2014年 | 2469篇 |
2013年 | 4719篇 |
2012年 | 3441篇 |
2011年 | 3768篇 |
2010年 | 3300篇 |
2009年 | 3699篇 |
2008年 | 3636篇 |
2007年 | 3498篇 |
2006年 | 2945篇 |
2005年 | 2361篇 |
2004年 | 2098篇 |
2003年 | 1917篇 |
2002年 | 1835篇 |
2001年 | 1808篇 |
2000年 | 2048篇 |
1999年 | 1872篇 |
1998年 | 3973篇 |
1997年 | 2885篇 |
1996年 | 1986篇 |
1995年 | 1552篇 |
1994年 | 1347篇 |
1993年 | 1364篇 |
1992年 | 1017篇 |
1991年 | 1066篇 |
1990年 | 1096篇 |
1989年 | 1059篇 |
1988年 | 952篇 |
1987年 | 881篇 |
1986年 | 886篇 |
1985年 | 950篇 |
1984年 | 784篇 |
1983年 | 773篇 |
1982年 | 681篇 |
1981年 | 696篇 |
1980年 | 677篇 |
1979年 | 659篇 |
1978年 | 642篇 |
1977年 | 782篇 |
1976年 | 953篇 |
1975年 | 590篇 |
1974年 | 561篇 |
1973年 | 547篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast... 相似文献
3.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a... 相似文献
4.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
5.
Boltar K. O. Burlakov I. D. Iakovleva N. I. Vlasov P. V. Lazarev P. S. 《Journal of Communications Technology and Electronics》2022,67(9):1175-1184
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of... 相似文献
6.
Gordenchuk A. D. Kudryashova O. S. 《Theoretical Foundations of Chemical Engineering》2019,53(4):591-595
Theoretical Foundations of Chemical Engineering - Calcium formate is widely used in construction, tanning, and textile manufacture and as an E238 biological additive in cosmetology and the food... 相似文献
7.
Glass and Ceramics - An analysis of the specific mechanisms of the influence of the state of the grain structure on the thermoelectric properties (electrical resistivity and total thermal... 相似文献
8.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
9.
Laís D. Silva Fernanda C. Puosso Viviane O. Soares Oscar Peitl Filho Simone do R.F. Sabino Francisco C. Serbena Murilo C. Crovace Edgar D. Zanotto 《Ceramics International》2021,47(13):18720-18731
Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K2O-26.9CaO-46.1SiO2-2.6P2O5 mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration. 相似文献
10.
Franois Ancien Fabrizio Pucci Marianne Rooman 《International journal of molecular sciences》2021,22(9)
Sphingomyelin phosphodiesterase (SMPD1) is a key enzyme in the sphingolipid metabolism. Genetic SMPD1 variants have been related to the Niemann-Pick lysosomal storage disorder, which has different degrees of phenotypic severity ranging from severe symptomatology involving the central nervous system (type A) to milder ones (type B). They have also been linked to neurodegenerative disorders such as Parkinson and Alzheimer. In this paper, we leveraged structural, evolutionary and stability information on SMPD1 to predict and analyze the impact of variants at the molecular level. We developed the SMPD1-ZooM algorithm, which is able to predict with good accuracy whether variants cause Niemann-Pick disease and its phenotypic severity; the predictor is freely available for download. We performed a large-scale analysis of all possible SMPD1 variants, which led us to identify protein regions that are either robust or fragile with respect to amino acid variations, and show the importance of aromatic-involving interactions in SMPD1 function and stability. Our study also revealed a good correlation between SMPD1-ZooM scores and in vitro loss of SMPD1 activity. The understanding of the molecular effects of SMPD1 variants is of crucial importance to improve genetic screening of SMPD1-related disorders and to develop personalized treatments that restore SMPD1 functionality. 相似文献