全文获取类型
收费全文 | 1899篇 |
免费 | 55篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 31篇 |
综合类 | 2篇 |
化学工业 | 748篇 |
金属工艺 | 66篇 |
机械仪表 | 54篇 |
建筑科学 | 56篇 |
矿业工程 | 12篇 |
能源动力 | 82篇 |
轻工业 | 113篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
武器工业 | 3篇 |
无线电 | 135篇 |
一般工业技术 | 247篇 |
冶金工业 | 45篇 |
原子能技术 | 7篇 |
自动化技术 | 355篇 |
出版年
2023年 | 9篇 |
2022年 | 75篇 |
2021年 | 106篇 |
2020年 | 25篇 |
2019年 | 35篇 |
2018年 | 49篇 |
2017年 | 47篇 |
2016年 | 73篇 |
2015年 | 51篇 |
2014年 | 65篇 |
2013年 | 138篇 |
2012年 | 99篇 |
2011年 | 97篇 |
2010年 | 110篇 |
2009年 | 78篇 |
2008年 | 92篇 |
2007年 | 70篇 |
2006年 | 54篇 |
2005年 | 58篇 |
2004年 | 52篇 |
2003年 | 50篇 |
2002年 | 44篇 |
2001年 | 34篇 |
2000年 | 21篇 |
1999年 | 26篇 |
1998年 | 17篇 |
1997年 | 22篇 |
1996年 | 29篇 |
1995年 | 16篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 10篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 23篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有1960条查询结果,搜索用时 10 毫秒
61.
The new 3-D photoelastic method was applied to the studies of residual stresses around spherical inclusion in polymeric matrices. Full stress tensor for several model samples was measured. The extent of significant stresses is not greater than three radii of an inclusion. It was found that the stress follows the 1/R3 rule at distances far from the inclusion, while in the narrow zone at the interface a plateau is observed. The level of stress ranges from few MPa up to the plastic yield of the polymeric matrix. The radial stress component is usually twice as large as the tangential stress component. Radial negative stress and tangential positive stresses are found in configuration with a hard inclusion, while radial positive stress and tangential negative stresses are in the systems with soft inclusion. The pressure in the matrix at points around inclusions calculated from the stress tensor is always near zero MPa, which indicates the action of purely deviatoric stresses in the matrix. 相似文献
62.
Andrzej Gawor Zdzislaw Gajewski Leszek Paczek Bozena Czarkowska-Paczek Anna Konopka Grzegorz Wryk Ewa Bulska 《International journal of molecular sciences》2022,23(8)
In many pharmaceuticals, a hydrogen atom or hydroxyl group is replaced by a fluorine to increase bioavailability and biostability. The fate of fluorine released from fluorine-containing drugs is not well investigated. The aim of this study was to examine possible fluorination of proteins in rat liver and brain after administration of the fluorinated drug cinacalcet. We assigned 18 Wistar rats to a control group (n = 6) and a group treated with cinacalcet (2 mg kg−1/body weight, 5 days/week), divided into 7 day (n = 6) and 21 day (n = 6) treatment subgroups. Fluorinated proteins were identified using a free proteomics approach; chromatographic separation and analysis by high-resolution mass spectrometry; peptide/protein identification using the Mascot search algorithm; manual verification of an experimentally generated MS/MS spectrum with the theoretical MS/MS spectrum of identified fluorinated peptides. Three fluorinated proteins (spectrin beta chain; carbamoyl-phosphate synthase [ammonia], mitochondrial; 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 1) were identified in the liver and four (spectrin beta chain, dihydropyrimidinase-related protein 4, prominin-2, dihydropyrimidinase-related protein 4) in the brain tissue after 21 days of cinacalcet treatment, but not in the control group. Introduction of fluorine into an organism by administration of fluorinated drugs results in tissue-specific fluorination of proteins. 相似文献
63.
This article presents a new lake district in Southern Poland created as a result of human activity in the Upper Silesian region. The area has been named the Upper Silesian Anthropogenic Lake District. The lake density of the Lake District as delineated by the authors (with an area of 6766 km2) is 2.74%. It includes 4773 water bodies of various origins – reservoirs retained by dams, flooded mineral workings, water bodies formed in subsidence basins and hollows, levee ponds, residual water bodies following river regulation and other water bodies. These are located in urban‐industrial, rural‐agricultural or quasi‐natural areas. The hydrochemical diversity of water bodies is conditioned by their origin, location in the catchment and function. Studies have shown the widespread occurrence of eutrophication processes in limnic waters within the Lake District. The diverse origin and hydrochemical properties of water bodies within the Upper Silesian Anthropogenic Lake District make it special among other anthropogenic lake districts. 相似文献
64.
Andrzej Piasecki 《Advanced Synthesis \u0026amp; Catalysis》1987,329(4):579-586
The direct condensation reaction of prop-2-enal or but-2-enal with mixture of n-aliphatic alcohol and ethylene glycol, in the presence of p-toluenesulphonic acid as catalyst, leads to a complex mixture of saturated, unsaturated, cyclic and linear acetals, moreover, 2-(2-alkoxy-alkyl)-1,3-dioxolanes are the main reaction products. The detailed investigations for n-butanol showed that unsaturated cyclic acetals: 2-vinyl-1,2-dioxolane 1a or 2-(1-propenyl)-1,3-dioxolane 1b , as well as unsaturated linear acetals: 1,1-dibutoxy-prop-2-en 2a or 1,1-dibutoxy-but-2-en 2b are intermediate reaction products. Additionally, it was found in final products presence of eight by-products: 5-butoxy- 4a or 5-butoxy-7-methyl-1,4-dioxepane 4b , 1,1,3-tributoxypropane 5a or 1,1,3-tributoxybutane 5b , 2-[2-(2-hydroxyethoxy)ethyl]- 6a or 2-[2-(2-hydroxyethoxy)propyl]-1,3-dioxolane 6b , 5-(2-hydroxyethoxy)-7-methyl-1,4-dioxepane 7b , 1,3-dibutoxy-1-(2-hydroxyethoxy)-propane 8a or 1,3-dibutoxy-1-(2-hydroxyethoxy)-butane 8b , 1,1-dibutoxy-3-(2-hydroxyethoxy)-propane 9a or 1,1-dibutoxy-3-(2-hydroxyethoxy)-butane 9b , 3-butoxy-1,1-bis-(2-hydroxyethoxy)-propane 10a or 3-butoxy-1,1-bis-(2-hydroxyethoxy)-butane 10b , and 1-butoxy-1,3-bis-(2-hydroxyethoxy)-propane 11a or 1-butoxy-1,3-bis-(2-hydroxyethoxy)-butane 11b , respectively. 相似文献
65.
Krystyna Bogdanowicz-Szwed Andrzej Policht 《Advanced Synthesis \u0026amp; Catalysis》1984,326(5):721-728
The reaction of enamines 1 derivatives of cyclohexanon- or cycloheptanon-2-carboxylic acid anilides with malononitrile gave in the first step 2-phenylcarbamoyl-cycloalkylideno-malononitriles 3 , which in turn were converted into 1-oxo-2-phenyl-3-amino-4-cyano-cycloalkenoisoquinolines 4 . Enamines containing an adjacent diphenylamidino group 6 reacted with malononitrile giving 1-phenylimino-2-phenyl-3-amino-4-cyano-cycloalkenoisoquinolines 7 . The alkaline hydrolysis of 7 yielded 1-phenylamino-3-oxo-4-cyano-cycloalkenoisoquinoline 8 . 相似文献
66.
A comprehensive meta‐analysis on dietary flavonoid and lignan intake and cancer risk: Level of evidence and limitations 下载免费PDF全文
67.
Agnieszka Drd Adrianna Sawiska-Brych Dominika Kubera Magdalena Kimsa-Dudek Joanna Magdalena Gola Jolanta Adamska Celina Kruszniewska-Rajs Arkadiusz Matwijczuk Dariusz Karcz Wojciech Dbrowski Andrzej Stepulak Mariusz Gago 《International journal of molecular sciences》2022,23(23)
4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol (C1) and 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl] benzene1,3-diol (NTBD) are representative derivatives of the thiadiazole group, with a high antimycotic potential and minimal toxicity against normal human fibroblast cells. The present study has proved its ability to synergize with the antifungal activity of AmB. The aim of this work was to evaluate the cytotoxic effects of C1 or NTBD, alone or in combination with AmB, on human renal proximal tubule epithelial cells (RPTECs) in vitro. Cell viability was assessed with the MTT assay. Flow cytometry and spectrofluorimetric techniques were used to assess the type of cell death and production of reactive oxygen species (ROS), respectively. The ELISA assay was performed to measure the caspase-2, -3, and -9 activity. ATR-FTIR spectroscopy was used to evaluate biomolecular changes in RPTECs induced by the tested formulas. The combinations of C1/NTBD and AmB did not exert a strong inhibitory effect on the viability/growth of kidney cells, as evidenced by the negligible changes in the apoptotic/necrotic rate and caspase activity, compared to the control cells. Both NTBD and C1 displayed stronger anti-oxidant activity when combined with AmB. The relatively low nephrotoxicity of the thiadiazole derivative combinations and the protective activity against AmB-induced oxidative stress may indicate their potential use in the therapy of fungal infections. 相似文献
68.
The p-chlorophenyl glycidyl ether was polymerized in the presence of Al(OiPr)3, ZnCl2, SnCl4, BuOK, KOH and by the Al(OiPr)3ZnCl2 1:1 initiator system. Analysis of the 13C n.m.r. spectra of the poly(p-chlorophenyl glycidyl ethers) obtained has made it possible to determine their tacticity and the content of the head-to-tail and head-to-head linkages in the polymer chain. 相似文献
69.
A Monte Carlo method was used for a computer simulation of radiation-induced solid state polymerization. The propagation of polymer chains was simulated by means of self-avoiding random walks on a tetrahedral lattice. The initiation and termination of the chains were modelled by pseudorandom processes. The influence of conditions of the in-source process on the post-polymerization kinetics and on the degree of polymerization of the polymers was studied. 相似文献
70.
Determination of the ash yield and the mineral matter content of brown coals by density measurements
Edward Chruściel Wit Jagusztyn Andrzej Kreft Andrzej Lenda Wojciech Przybylowicz Jan Woźniak 《Fuel》1983,62(3):389-390
A method of measuring the density of bed-moist brown coals based on their plastic properties is described and the feasibility of using the method for determination of the ash yield of the coal is evaluated. 相似文献