全文获取类型
收费全文 | 115706篇 |
免费 | 1725篇 |
国内免费 | 866篇 |
专业分类
电工技术 | 1943篇 |
综合类 | 676篇 |
化学工业 | 15523篇 |
金属工艺 | 4003篇 |
机械仪表 | 3484篇 |
建筑科学 | 2463篇 |
矿业工程 | 890篇 |
能源动力 | 2251篇 |
轻工业 | 8361篇 |
水利工程 | 1423篇 |
石油天然气 | 2351篇 |
武器工业 | 45篇 |
无线电 | 8958篇 |
一般工业技术 | 19671篇 |
冶金工业 | 32731篇 |
原子能技术 | 2802篇 |
自动化技术 | 10722篇 |
出版年
2022年 | 639篇 |
2021年 | 988篇 |
2020年 | 706篇 |
2019年 | 819篇 |
2018年 | 1992篇 |
2017年 | 2222篇 |
2016年 | 2796篇 |
2015年 | 1719篇 |
2014年 | 1966篇 |
2013年 | 3951篇 |
2012年 | 4418篇 |
2011年 | 5201篇 |
2010年 | 3010篇 |
2009年 | 3366篇 |
2008年 | 3207篇 |
2007年 | 3158篇 |
2006年 | 2736篇 |
2005年 | 5210篇 |
2004年 | 4362篇 |
2003年 | 3797篇 |
2002年 | 2536篇 |
2001年 | 2393篇 |
2000年 | 1937篇 |
1999年 | 2138篇 |
1998年 | 9439篇 |
1997年 | 6197篇 |
1996年 | 4297篇 |
1995年 | 2881篇 |
1994年 | 2313篇 |
1993年 | 2388篇 |
1992年 | 1228篇 |
1991年 | 1335篇 |
1990年 | 1349篇 |
1989年 | 1311篇 |
1988年 | 1218篇 |
1987年 | 1083篇 |
1986年 | 1068篇 |
1985年 | 1094篇 |
1984年 | 845篇 |
1983年 | 842篇 |
1982年 | 803篇 |
1981年 | 862篇 |
1980年 | 845篇 |
1979年 | 705篇 |
1978年 | 715篇 |
1977年 | 1369篇 |
1976年 | 2210篇 |
1975年 | 676篇 |
1974年 | 589篇 |
1973年 | 590篇 |
排序方式: 共有10000条查询结果,搜索用时 558 毫秒
61.
62.
Advanced technologies and modern high-production machines for underground mining of thick gently dipping coal demand strict adherence to technological discipline, reduction in operational loss and selection of optimized ventilation modes. The authors analyze ventilation schemes used in working areas in thick gently dipping seams in order to reveal influence exerted by the schemes, methods and parameters of ventilation on distribution of air loss in mined-out areas. 相似文献
63.
Technical Physics Letters - Using the method of DC magnetron sputtering, nonstructured amorphous metal coatings of Zr75Pd25 composition were obtained with an average deposition rate of 1.3 nm/s at... 相似文献
64.
65.
N. Bartsch M. Girard A. Wilde T. Bruhn O. Kappenstein B. Vieth C. Hutzler A. Luch 《乙烯基与添加剂工艺杂志》2019,25(Z2):E12-E27
The thermo‐oxidative stability of widely used polymer additives has been investigated. A comparative analytical approach with classic and innovative decomposition models for polymer additives was conducted and the results supported using quantum‐chemical calculations. Unique pyrolysis products of the analytes were compiled utilizing pyrolysis online coupled to gas chromatography followed by mass spectrometric detection (Pyr‐GC–MS). The pyrolysis was either performed under inert conditions or in an oxygen‐containing atmosphere. Squalane was applied as polymer‐mimicking liquid next to low density polyethylene (LDPE) and polyamide 6 (PA 6) as matrices for 10 selected additives. The additives included in this study range from antioxidants and plasticizers to processing aids. These were selected to address a range of application in consumer products and to cover different chemical classes. The toxicological relevance of additives and potential breakdown products was considered. Consequently, degradation of sterically hindered antioxidants, diarylamines, and a trimellitic acid derivative was investigated. The findings were used to predict the behavior of consumer products made of polymeric materials entailing additives. The level of Antioxidant 2246 [2‐tert‐butyl‐6‐[(3‐tert‐butyl‐2‐hydroxy‐5‐methylphenyl)methyl]‐4‐methylphenol] and one of its predicted decomposition products was determined in baby bottle nipples made of natural rubber [2‐tert‐butyl‐4‐methylphenol] utilizing the complementary technique of gas chromatography coupled to tandem mass spectrometry (GC–MS/MS). This study provides a comprehensive characterization of important polymer additives and enables the prioritization of degradation products for further risk assessment. J. VINYL ADDIT. TECHNOL., 25:E12–E27, 2019. © 2018 The Authors. Journal of Vinyl and Additive Technology published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers 相似文献
66.
67.
68.
From an experimental and theoretical investigation of the continuity of influent inorganic suspended solids (ISS) along the links connecting the primary settling tank (PST), fully aerobic or N removal activated sludge (AS) and anaerobic and aerobic sludge digestion unit operations, it was found that the influent wastewater (fixed) ISS concentration is conserved through primary sludge anaerobic digestion, activated sludge and aerobic digestion unit operations. However, the measured ISS flux at different stages through a series of wastewater treatment plant (WWTP) unit operations is not equal to the influent ISS flux, because the ordinary heterotrophic organisms (OHO) biomass contributes to the ISS flux by differing amounts depending on the active fraction of the VSS solids at that stage. 相似文献
69.
D. A. Mirzaev N. I. Vorob’ev O. K. Tokovi D. V. Shaburov E. A. Fominykh 《Russian Metallurgy (Metally)》2006,(1):38-41
The solutions to a differential equation for the problem of heating of a cylinder in a medium with a fixed temperature are used to obtain equations for estimating the change in the hydrogen concentration in forgings from data on the hydrogen concentration at the cylinder axis or on the average bulk hydrogen concentration. Similar equations are also obtained for forgings having square cross sections. The calculation demonstrates that, for the case of a twofold decrease in the hydrogen concentration in a forging, the calculated times of annealing of a cylindrical forging differ by three times. 相似文献
70.
Role stress has received a lot of research attention in psychological, sociological, and organizational studies over the last several decades. Based on a literature review of about 300 journal articles, this article examines prominent consequences of role stress. Specific focus is on researching differences in relationships between facets of role stress (i.e., role ambiguity, role conflict, and role overload) and frequently cited consequences using techniques of meta-analysis. Findings indicate that each role stress facet has a different relationship with the eight consequences studied. Role stress research can benefit from looking at each facet individually in addition to role stress generally. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献