全文获取类型
收费全文 | 1072篇 |
免费 | 48篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 259篇 |
金属工艺 | 30篇 |
机械仪表 | 33篇 |
建筑科学 | 42篇 |
矿业工程 | 10篇 |
能源动力 | 39篇 |
轻工业 | 88篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 55篇 |
一般工业技术 | 147篇 |
冶金工业 | 188篇 |
原子能技术 | 3篇 |
自动化技术 | 185篇 |
出版年
2023年 | 8篇 |
2022年 | 23篇 |
2021年 | 37篇 |
2020年 | 32篇 |
2019年 | 35篇 |
2018年 | 22篇 |
2017年 | 24篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 46篇 |
2013年 | 76篇 |
2012年 | 49篇 |
2011年 | 69篇 |
2010年 | 56篇 |
2009年 | 51篇 |
2008年 | 41篇 |
2007年 | 43篇 |
2006年 | 37篇 |
2005年 | 21篇 |
2004年 | 31篇 |
2003年 | 20篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 33篇 |
1997年 | 24篇 |
1996年 | 20篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 26篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1959年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有1120条查询结果,搜索用时 281 毫秒
1.
2.
3.
Results of a study on the modifying mechanical properties of loose optical‐fiber poly(butylene terephthalate) (PBT) tubes, produced during the standard industrial extrusion process, show that heat treatment make the structure of their material to change. The study comprised measurements of mechanical strengths properties of the tubes (tensile strength, compression strength, kinking) and determination of tube material structure [by differential thermal analysis (DTA), wide angle X‐ray scattering analysis (WAXD), and scanning electron microscopy (SEM)]. Results of the study allowed observation that the annealing at 70°C for 34 h of the tubes caused the crystalline α phase to increase in the tube material from ~28.5% to ~31.5% and the structure of the existing crystallites to become more perfect. This made the values of certain mechanical properties of the tubes to increase even by as much as 30%. The tubes following such thermal treatment could be used in cables exposed to heavy‐duty operation in arduous environments, where a larger margin from the standpoint of mechanical properties is required. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2130–2134, 2002 相似文献
4.
Further evidence was delivered that certain impurities, which could be contained in MgO samples, might be responsible for observed variability in MgO basicity and catalytic performance in oxidative coupling of methane. The surface basicity/base strength distribution of a series of MgO samples containing or not containing Ca and Na impurities was determined by a temperature-programmed desorption of CO2. It was revealed that samples containing Ca and Na impurities have much more medium, strong and very strong basic sites. The surface basicity of MgO samples containing added alkali or alkaline earth compounds or water was characterized by a test reaction of transformation of 2-butanol. It was confirmed that the introduction of these compounds to a pure MgO enhanced both its basicity and activity in oxidative coupling of methane. 相似文献
5.
6.
R Romeo V Thiers F Driss P Berthelot B Nalpas C Brechot 《Canadian Metallurgical Quarterly》1993,33(8):629-633
The pattern of hepatitis C virus (HCV) viremia in blood donors who are positive for antibody to HCV (anti-HCV) according to the level of transaminase activity is unclear. A polymerase chain reaction-based HCV RNA detection method was used to study two clearly defined groups of anti-HCV-positive blood donors with repeatedly normal (n = 27) and elevated (n = 17) alanine aminotransferase (ALT) levels. HCV RNA was detected in only 4 of 27 blood donors with normal ALT values and 15 of 17 with elevated ALT values. These results indicate that anti-HCV-positive blood donors with normal ALT levels constitute a heterogeneous group, as HCV viremia is detectable in only a small proportion of cases. Polymerase chain reaction should be useful in the surveillance of anti-HCV-positive blood donors with normal ALT levels, by identifying those who might benefit from further investigation and treatment. 相似文献
7.
Jan Langer Marian Klasztorny Salah El-Sayed El-Bagalaty' 《International journal for numerical methods in engineering》1992,33(5):889-905
The paper presents a family of methods with postintegration, for numerical integration of non-linear dynamic equations of motion of discrete systems. Both explicit and implicit algorithms of these methods are conditionally stable, but can give solutions of accuracy of a few orders higher than the known methods with preintegration, corresponding to them. A general analysis of stability and accuracy of single-step methods is carried out. The postintegration methods have been tested on a single-degree-of-freedom non-linear system. 相似文献
8.
Tobin David L.; Johnson Craig; Steinberg Stacey; Staats Marian; Dennis Amy Baker 《Canadian Metallurgical Quarterly》1991,100(1):14
Investigated a multifactorial approach to the assessment of bulimia nervosa by means of hierarchical factor analysis. 245 bulimia nervosa patients and 68 patients with either anorexia nervosa or eating disorders not otherwise specified were administered a self-report battery that was organized into 21 dimensions relevant to eating disorder patients. When dimensions from this battery were subjected to hierarchical factor analysis, support for bulimia nervosa as a unique diagnostic category was obtained. However, the emergence of 3 secondary factors and 6 primary factors suggests that bulimia nervosa can also be described more complexly. The emergence of a multifactorial model of bulimia nervosa that incorporates several existing unidimensional models suggests the potential for both divergent and complicated clinical presentation in bulimia nervosa patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Recent foodborne outbreaks have linked infection by enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 to the consumption of contaminated lettuce. Contamination via food handler error and on-the-farm contamination are thought to be responsible for several outbreaks. Though recent studies have examined the application of EHEC to store-bought lettuce, little is known about the attachment of EHEC to growing plants. We investigated the association of lettuce seedlings with EHEC O157:H7 strains implicated in lettuce or fruit outbreaks using hydroponic and soil model systems. EHEC strains that express the green fluorescent protein were observed by stereomicroscopy and confocal laser scanning microscopy to determine adherence patterns on growing lettuce seedlings. Bacteria adhered preferentially to plant roots in both model systems and to seed coats in the hydroponic system. Two of five nonpathogenic E. coli strains showed decreased adherence to seedling roots in the hydroponic system. EHEC was associated with plants in as few as 3 days in soil, and contamination levels were dose-dependent. EHEC levels associated with young plants inoculated with a low dose suggested that the bacteria had multiplied. These data suggest that preharvest crop contamination via contaminated irrigation water can occur through plant roots. 相似文献
10.
A genetic algorithm for the optimisation of assembly sequences 总被引:6,自引:0,他引:6
This paper describes a Genetic Algorithm (GA) designed to optimise the Assembly Sequence Planning Problem (ASPP), an extremely diverse, large scale and highly constrained combinatorial problem. The modelling of the ASPP problem, which has to be able to encode any industrial-size product with realistic constraints, and the GA have been designed to accommodate any type of assembly plan and component. A number of specific modelling issues necessary for understanding the manner in which the algorithm works and how it relates to real-life problems, are succinctly presented, as they have to be taken into account/adapted/solved prior to Solving and Optimising (S/O) the problem. The GA has a classical structure but modified genetic operators, to avoid the combinatorial explosion. It works only with feasible assembly sequences and has the ability to search the entire solution space of full-scale, unabridged problems of industrial size. A case study illustrates the application of the proposed GA for a 25-components product. 相似文献