全文获取类型
收费全文 | 9336篇 |
免费 | 600篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 87篇 |
综合类 | 15篇 |
化学工业 | 2407篇 |
金属工艺 | 279篇 |
机械仪表 | 302篇 |
建筑科学 | 376篇 |
矿业工程 | 19篇 |
能源动力 | 313篇 |
轻工业 | 1288篇 |
水利工程 | 65篇 |
石油天然气 | 39篇 |
武器工业 | 2篇 |
无线电 | 679篇 |
一般工业技术 | 1638篇 |
冶金工业 | 877篇 |
原子能技术 | 89篇 |
自动化技术 | 1483篇 |
出版年
2024年 | 25篇 |
2023年 | 111篇 |
2022年 | 239篇 |
2021年 | 380篇 |
2020年 | 268篇 |
2019年 | 283篇 |
2018年 | 406篇 |
2017年 | 400篇 |
2016年 | 439篇 |
2015年 | 310篇 |
2014年 | 429篇 |
2013年 | 684篇 |
2012年 | 620篇 |
2011年 | 725篇 |
2010年 | 526篇 |
2009年 | 498篇 |
2008年 | 466篇 |
2007年 | 353篇 |
2006年 | 296篇 |
2005年 | 273篇 |
2004年 | 197篇 |
2003年 | 201篇 |
2002年 | 189篇 |
2001年 | 131篇 |
2000年 | 107篇 |
1999年 | 85篇 |
1998年 | 232篇 |
1997年 | 182篇 |
1996年 | 119篇 |
1995年 | 86篇 |
1994年 | 83篇 |
1993年 | 74篇 |
1992年 | 39篇 |
1991年 | 39篇 |
1990年 | 31篇 |
1989年 | 32篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 22篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 14篇 |
1977年 | 19篇 |
1976年 | 36篇 |
1971年 | 12篇 |
排序方式: 共有9958条查询结果,搜索用时 15 毫秒
21.
Interest has increased during recent years in using microcomputers for implementation of network reliability algorithms. There are indications that some implementations suffer severe restrictions imposed by such a computing environment, whereas some other results indicate otherwise. This brief note attempts to clarify the apparently contradictory conclusions that would be naturally drawn from recent papers that treat this subject. 相似文献
22.
Auguste Commeyras Hlne Collet Laurent Boiteau Jacques Taillades Odile Vandenabeele‐Trambouze Herv Cottet Jean‐Philippe Biron Raphaël Plasson Louis Mion Olivier Lagrille Herv Martin Franck Selsis Michel Dobrijevic 《Polymer International》2002,51(7):661-665
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry. 相似文献
23.
The ability of human gastrointestinal organisms to transform the trichothecenes 3-acetyldeoxynivalenol and nivalenol was investigated. Samples of human faeces were incubated under anaerobic conditions for 48 h with the toxins. They were then extracted and analysed for trichothecenes and metabolites. 3-Acetyldeoxynivalenol was metabolized to deoxynivalenol during the incubation period. In contrast to what has been reported for other species such as rats, mice and pigs, no de-epoxidated metabolites were detected in the faecal incubates. The toxicological significance of the difference in the intestinal ability to transform trichothecenes between species is unknown. 相似文献
24.
Coating of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO3 (SRO) metallic oxide electrodes on SrTiO3 (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed. 相似文献
25.
Ahmet Ekmekyapar Nizamettin Demirkran Asm Künkül 《Chemical Engineering Research and Design》2008,86(9):1011-1016
Ulexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kJ/mol. 相似文献
26.
Guimond Serge; Dambrun Micha?l; Michinov Nicolas; Duarte Sandra 《Canadian Metallurgical Quarterly》2003,84(4):697
Social dominance orientation (SDO) has been proposed as an important variable in the explanation of prejudice. We distinguish between three conceptualizations of SDO: SDO as a personality trait (personality model), SDO as a moderator of the effects of situational variables (Person X Situation model), and SDO as a mediator of the effect of social position on prejudice (group socialization model [GSM]). Four studies (N = 1,657) looking at the relations between social positions, SDO, and prejudice in a natural setting and in a laboratory setting provide strong support for the GSM. In contrast to previous correlational findings, there is evidence of a cause (dominant social position), an effect (prejudice increases), and a mediator (SDO). These results suggest new perspectives on the integration of individual and contextual determinants of prejudice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
28.
29.
Raphaëlle Savoire Jean‐Louis Lanoisellé Hélène Ducatel Eugène Vorobiev 《European Journal of Lipid Science and Technology》2008,110(8):725-734
Seven linseed varieties were harvested at seven times before complete maturity. Microscale oilseed expressions were subsequently carried out on it. A pressure of 10 MPa was applied for 1 h under uniaxial stress. The results were characterized in terms of oil, water and mucilage content, harvest date and oil yield. The piston displacement versus time (creep curves) was described by a four‐Kelvin‐Voigt elements viscoelastic model. Parameters were derived from the model, such as the mechanical properties of seeds (compressibility moduli), showing that the viscoelastic model fits well the experimental data (R² ≈ 0.999). The modeling parameters were combined with some biochemical data in order to predict the kinetics of oil extraction. 相似文献
30.
Paulussen-Hoogeboom Marja C.; Stams Geert Jan J. M.; Hermanns Jo M. A.; Peetsma Thea T. D. 《Canadian Metallurgical Quarterly》2007,43(2):438
This meta-analytic review (k = 62 studies; N = 7,613 mother-child dyads) shows that effect sizes for the association between child negative emotionality and parenting were generally small and were moderated by sample and measurement characteristics. The association between more child negative emotionality and less supportive parenting was relatively strong in lower socioeconomic status families, reversed in higher socioeconomic status families, and limited to studies with relatively high percentages of participants from ethnic minorities and studies using parent report to assess negative emotionality. Higher levels of child negative emotionality were associated with more restrictive control in samples with less than 75% 1st-born children, as well as in infants and preschoolers, and in studies using parent report or composite measures to assess both negative emotionality and restrictive parenting. Finally, more child negative emotionality was associated with less inductive control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献