全文获取类型
收费全文 | 388465篇 |
免费 | 5700篇 |
国内免费 | 2186篇 |
专业分类
电工技术 | 7429篇 |
技术理论 | 5篇 |
综合类 | 3444篇 |
化学工业 | 56643篇 |
金属工艺 | 20253篇 |
机械仪表 | 15519篇 |
建筑科学 | 9424篇 |
矿业工程 | 2823篇 |
能源动力 | 7163篇 |
轻工业 | 29118篇 |
水利工程 | 4729篇 |
石油天然气 | 7442篇 |
武器工业 | 244篇 |
无线电 | 41243篇 |
一般工业技术 | 78050篇 |
冶金工业 | 54194篇 |
原子能技术 | 6773篇 |
自动化技术 | 51855篇 |
出版年
2021年 | 2357篇 |
2019年 | 2106篇 |
2018年 | 22712篇 |
2017年 | 22238篇 |
2016年 | 15985篇 |
2015年 | 3776篇 |
2014年 | 4843篇 |
2013年 | 11609篇 |
2012年 | 12402篇 |
2011年 | 24864篇 |
2010年 | 21512篇 |
2009年 | 19064篇 |
2008年 | 20452篇 |
2007年 | 23005篇 |
2006年 | 8650篇 |
2005年 | 11566篇 |
2004年 | 9249篇 |
2003年 | 8544篇 |
2002年 | 7014篇 |
2001年 | 6212篇 |
2000年 | 5852篇 |
1999年 | 5691篇 |
1998年 | 12673篇 |
1997年 | 9367篇 |
1996年 | 7071篇 |
1995年 | 5504篇 |
1994年 | 5106篇 |
1993年 | 4965篇 |
1992年 | 3944篇 |
1991年 | 3766篇 |
1990年 | 3821篇 |
1989年 | 3730篇 |
1988年 | 3500篇 |
1987年 | 2993篇 |
1986年 | 3029篇 |
1985年 | 3412篇 |
1984年 | 3315篇 |
1983年 | 3060篇 |
1982年 | 2688篇 |
1981年 | 2877篇 |
1980年 | 2633篇 |
1979年 | 2830篇 |
1978年 | 2731篇 |
1977年 | 2837篇 |
1976年 | 3695篇 |
1975年 | 2449篇 |
1974年 | 2288篇 |
1973年 | 2316篇 |
1972年 | 1977篇 |
1971年 | 1780篇 |
排序方式: 共有10000条查询结果,搜索用时 74 毫秒
31.
Russian Engineering Research - In practice, it is important to assess the nonuniformity of the crankshaft speed in internal combustion engines. In such assessments, the sensitivity of the chosen... 相似文献
32.
Semiconductors - The precision fabrication of microstructures and nanostructures by the focused-ion-beam method is significantly simplified by the simulation of sputtering of materials by... 相似文献
33.
Sánchez-Vásquez J. D. Portillo-Rodríguez B. Tovar-Martínez E. Reyes-Reyes M. López-Sandoval R. 《Journal of Materials Science: Materials in Electronics》2022,33(18):14910-14926
Journal of Materials Science: Materials in Electronics - Non-volatile organic memory devices were fabricated using polystyrene sulfonate (PSS)?+?nitrogen-doped multi-walled carbon... 相似文献
34.
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
35.
Zagidullin S. Kh. Dolganov V. L. Lozhkin I. G. 《Chemical and Petroleum Engineering》2022,57(9-10):765-769
Chemical and Petroleum Engineering - The hydrodynamics of oxidation towers used for bitumen production were studied using a model tower having transparent walls. Experiments were carried out in two... 相似文献
36.
37.
Shu-Hung Yang Yi-Nan Lin Cheng-Ying Yang Ming-Kuen Chen Victor R. L. Shen Yu-Wei Lin 《电子科技学刊:英文版》2022,20(2):209-223
An increasing number of social media and networking platforms have been widely used. People usually post the online comments to share their own opinions on the networking platforms with social media. Business companies are increasingly seeking effective ways to mine what people think and feel regarding their products and services. How to correctly understand the online customers’ reviews becomes an important issue. This study aims to propose a method with the aspect-oriented Petri nets (AOPN) to improve the examination correctness without changing any process and program. We collect those comments from the online reviews with Scrapy tools, perform sentiment analysis using SnowNLP, and examine the analysis results to improve the correctness. In this paper, we apply our method for a case of the online movie comments. The experimental results have shown that AOPN is helpful for the sentiment analysis and verifying its correctness. 相似文献
38.
Zienko S. I. Zhbanova V. L. 《Journal of Communications Technology and Electronics》2022,67(4):395-402
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a... 相似文献
39.
Kathleen T. Lauser Amy L. Rueter Michelle A. Calabrese 《American Institute of Chemical Engineers》2022,68(12):e17850
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations. 相似文献
40.
Weiyu Bi Panfeng Zhang Xiangrui Du Wei Lü Shitou Wang Tangying Yang Liping Ma Xiaochun Liu Haifeng Zhao Shaoran Ren 《Journal of surfactants and detergents》2022,25(3):387-398
Natural gas foam can be used for mobility control and channel blocking during natural gas injection for enhanced oil recovery, in which stable foams need to be used at high reservoir temperature, high pressure and high water salinity conditions in field applications. In this study, the performance of methane (CH4) foams stabilized by different types of surfactants was tested using a high pressure and high temperature foam meter for surfactant screening and selection, including anionic surfactant (sodium dodecyl sulfate), non-anionic surfactant (alkyl polyglycoside), zwitterionic surfactant (dodecyl dimethyl betaine) and cationic surfactant (dodecyl trimethyl ammonium chloride), and the results show that CH4-SDS foam has much better performance than that of the other three surfactants. The influences of gas types (CH4, N2, and CO2), surfactant concentration, temperature (up to 110°C), pressure (up to 12.0 MPa), and the presence of polymers as foam stabilizer on foam performance was also evaluated using SDS surfactant. The experimental results show that the stability of CH4 foam is better than that of CO2 foam, while N2 foam is the most stable, and CO2 foam has the largest foam volume, which can be attributed to the strong interactions between CO2 molecules with H2O. The foaming ability and foam stability increase with the increase of the SDS concentration up to 1.0 wt% (0.035 mol/L), but a further increase of the surfactant concentration has a negative effect. The high temperature can greatly reduce the stability of CH4-SDS foam, while the foaming ability and foam stability can be significantly enhanced at high pressure. The addition of a small amount of polyacrylamide as a foam stabilizer can significantly increase the viscosity of the bulk solution and improve the foam stability, and the higher the molecular weight of the polymer, the higher viscosity of the foam liquid film, the better foam performance. 相似文献