全文获取类型
收费全文 | 379666篇 |
免费 | 4327篇 |
国内免费 | 763篇 |
专业分类
电工技术 | 7824篇 |
综合类 | 645篇 |
化学工业 | 55595篇 |
金属工艺 | 16313篇 |
机械仪表 | 14392篇 |
建筑科学 | 9188篇 |
矿业工程 | 1600篇 |
能源动力 | 9115篇 |
轻工业 | 32144篇 |
水利工程 | 3590篇 |
石油天然气 | 4942篇 |
武器工业 | 8篇 |
无线电 | 46392篇 |
一般工业技术 | 76762篇 |
冶金工业 | 62060篇 |
原子能技术 | 6464篇 |
自动化技术 | 37722篇 |
出版年
2021年 | 2276篇 |
2019年 | 2141篇 |
2018年 | 11643篇 |
2017年 | 12120篇 |
2016年 | 8047篇 |
2015年 | 3074篇 |
2014年 | 4525篇 |
2013年 | 14326篇 |
2012年 | 9892篇 |
2011年 | 18137篇 |
2010年 | 15651篇 |
2009年 | 15683篇 |
2008年 | 15876篇 |
2007年 | 17832篇 |
2006年 | 8573篇 |
2005年 | 11466篇 |
2004年 | 9666篇 |
2003年 | 9049篇 |
2002年 | 7948篇 |
2001年 | 7605篇 |
2000年 | 7337篇 |
1999年 | 7568篇 |
1998年 | 17662篇 |
1997年 | 12833篇 |
1996年 | 10109篇 |
1995年 | 7882篇 |
1994年 | 7228篇 |
1993年 | 6924篇 |
1992年 | 5299篇 |
1991年 | 5084篇 |
1990年 | 4933篇 |
1989年 | 4781篇 |
1988年 | 4679篇 |
1987年 | 3886篇 |
1986年 | 4007篇 |
1985年 | 4717篇 |
1984年 | 4275篇 |
1983年 | 4021篇 |
1982年 | 3601篇 |
1981年 | 3761篇 |
1980年 | 3456篇 |
1979年 | 3418篇 |
1978年 | 3225篇 |
1977年 | 3814篇 |
1976年 | 4847篇 |
1975年 | 2780篇 |
1974年 | 2660篇 |
1973年 | 2675篇 |
1972年 | 2215篇 |
1971年 | 1963篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
O. R. Dornyak 《Journal of Engineering Physics and Thermophysics》2003,76(3):648-654
A rheological equation of state for wood which allows for the running values of its porosity and humidity is considered. 相似文献
992.
S. O. Balanetskii B. Grushko K. Urban T. Ya. Velikanova 《Powder Metallurgy and Metal Ceramics》2004,43(9):480-483
Scanning and transmission electron microscopy have been combined with x-ray diffraction to examine the phase equilibria in the Al - Pd - Re system at 1000°C for compositions from 50 to 100 at.% Al, and the corresponding isothermal section has been constructed. The binary monoclinic Al3 Re phase has been observed for the first time. It is confirmed that there is a stable icosahedral phase in this system. The boundaries to its homogeneity region have been determined and the phase equilibria in which it participates. 相似文献
993.
994.
Wilcox Sara; Evenson Kelly R.; Aragaki Aaron; Wassertheil-Smoller Sylvia; Mouton Charles P.; Loevinger Barbara Lee 《Canadian Metallurgical Quarterly》2003,22(5):513
This study examined whether widowhood was associated with physical and mental health, health behaviors, and health outcomes using a cross-sectional (N=72,247) and prospective (N=55,724) design in women aged 50-79 years participating in the Women's Health Initiative observational study (85.4% White). At baseline, married women reported better physical and mental health and generally better health behaviors than widowed women. Whereas women who remained married over the 3-year period showed stability in mental health, recent widows experienced marked impairments and longer term widows showed stability or slight improvements. Both groups of widows reported more unintentional weight loss over the 3-year period. Changes in physical health and health behaviors were inconsistent, with generally small effect sizes. Findings underscore the resilience of older women and their capacity to reestablish connections, but point to the need for services that strengthen social support among women who have difficulty during this transition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes. 相似文献
996.
A. V. Solokhin S. L. Nazanskii V. S. Timofeev 《Theoretical Foundations of Chemical Engineering》2005,39(2):105-109
The evolution of the phase portrait for the dynamic system of open evaporation combined with a chemical reaction for a fixed liquid amount was studied as dependent on the rate constants of the reaction. A three-component azeotropic mixture whose vapor-liquid equilibrium diagram is characterized by two distillation regions was considered. The possibility of the open evaporation trajectory to transfer through the separatrix between the distillation regions was shown, as well as the possibility of implementing the principle of redistribution of the concentration fields due to chemical reactions occurring in reactive distillation columns.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 2, 2005, pp. 115–119.Original Russian Text Copyright © 2005 by Solokhin, Nazanskii, Timofeev. 相似文献
997.
998.
999.
The presence of long chain acyl:CoA synthetases in mammalian microsomes and mitochondria has been established previously by
Aas (Biochim. Biophys. Acta 231, 32–47 [1971]). The presence of a plasma membrane-associated enzyme was investigated in rat hepatocyte plasma membranes,
where an enzyme exhibiting high activity and with a preferred substrate of 18-carbon chain length was discovered. The results
are consistent with the presence of a single enzyme. The effect of the degree of unsaturation of the fatty acid substrates
was not as pronounced as that arising from the length of the carbon chain. The pattern of substrate preference of the enzyme
was ω3 polyenoic fatty acids >ω6 polyenoic acids >ω9 monoenoic acids > saturated acids. This may relate to the similar substrate
preference pattern exhibited by the fatty acyl desaturase enzymes. The role played by long chain acyl:CoA synthetase in hepatocyte
metabolism is uncertain, but it may relate to the incorporation of polyenoic fatty acids from the circulation into cell membranes
and the trapping of other fatty acids within the cell for further metabolism. 相似文献
1000.
Z. P. Shul'man B. M. Khusid I. L. Ryklina É. A. Zal'tsgendler O. R. Dornyak É. V. Ivashkevich Z. A. Shabunina 《Journal of Engineering Physics and Thermophysics》1987,53(5):1285-1291
Dynamic processes are studied in media with softly and hardly internal destroyable configurations. A method is examined for the measurement of properties of media with spatial separation of the chemical transformation stages and thermal hydrodynamic measurements.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 781–789, November, 1987. 相似文献