全文获取类型
收费全文 | 1539篇 |
免费 | 77篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 287篇 |
金属工艺 | 12篇 |
机械仪表 | 33篇 |
建筑科学 | 19篇 |
矿业工程 | 2篇 |
能源动力 | 26篇 |
轻工业 | 125篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 204篇 |
一般工业技术 | 246篇 |
冶金工业 | 553篇 |
原子能技术 | 6篇 |
自动化技术 | 94篇 |
出版年
2023年 | 10篇 |
2022年 | 14篇 |
2021年 | 31篇 |
2020年 | 15篇 |
2019年 | 25篇 |
2018年 | 34篇 |
2017年 | 30篇 |
2016年 | 33篇 |
2015年 | 22篇 |
2014年 | 41篇 |
2013年 | 59篇 |
2012年 | 54篇 |
2011年 | 97篇 |
2010年 | 55篇 |
2009年 | 49篇 |
2008年 | 65篇 |
2007年 | 56篇 |
2006年 | 47篇 |
2005年 | 31篇 |
2004年 | 30篇 |
2003年 | 37篇 |
2002年 | 37篇 |
2001年 | 26篇 |
2000年 | 35篇 |
1999年 | 38篇 |
1998年 | 170篇 |
1997年 | 110篇 |
1996年 | 80篇 |
1995年 | 44篇 |
1994年 | 33篇 |
1993年 | 43篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1978年 | 2篇 |
1977年 | 27篇 |
1976年 | 41篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1624条查询结果,搜索用时 234 毫秒
1.
2.
IG Sumner A Vaughan R Eisenthal RW Pickersgill AJ Owen PW Goodenough 《Canadian Metallurgical Quarterly》1993,1164(3):243-251
Papaya proteinase omega (pp omega) has been purified from dried latex both by immunoaffinity and traditional methods. Kinetic analysis revealed that (1), the pp omega-catalysed hydrolysis of N-benzoyl-L-arginine p-nitroanilide (BApNA) has a lower specificity (kcat/Km) than the same reaction catalysed by papain; (2), the pp omega-catalysed hydrolysis of a tripeptide substrate having phenylalanine at the second position (S2-site) showed a more similar specificity to that catalysed by papain; (3), the significant difference between the two enzymes is that steady state kinetics with both L-BApNA and a tripeptide enables the identification in pp omega of other ionizations affecting binding. The active sites of papain and pp omega can therefore be distinguished by pH-dependence of kcat/Km. 相似文献
3.
4.
DI Timokhin AV Istomin TS Shushkova TG Voronel' IG Mikha?lov 《Canadian Metallurgical Quarterly》1997,(2):19-21
Based on generalization and analysis of instructions and guidelines for therapeutical and prophylactic diets of workers, ways of its optimization were proposed, by using bifide-containing acid dairy products as a preventive agent against possible occupational diseases caused by occupational factors. 相似文献
5.
Takuma Suzuki Hang-Ju Ko Agus Setiawan Jung-Jin Kim Koh Saitoh Masami Terauchi Takafumi Yao 《Materials Science in Semiconductor Processing》2003,6(5-6):519-521
We report the successful growth of Ga-polar GaN epilayers on O-polar ZnO templates pre-deposited on c-sapphire. Prior to GaN growth, NH3 is exposed onto the ZnO template. The polarity of the GaN layers is confirmed by etching of the surface and by conversion beam electron diffraction (CBED), while the O-polar ZnO is confirmed by CBED. It is suggested that the NH3 pre-exposure helps form a Zn3N2 layer, which possesses inversion symmetry and inverts the crystal from anion polar to cation polar. 相似文献
6.
A mica-based machinable glass-ceramic has been converted to a glass-ceramic containing cordiertie and body-centered cubic chondrodite through heat treatment at temperatures higher than that used for the crystallization of mica. The machinability is lost, microhardness increases, and the thermal expansion coefficient decreases with the change of the crystalline phase from mica to cordierite and chondrodite. 相似文献
7.
To evaluate an association between Helicobacter pylori (H. pylori) infection and chronic atrophic gastritis (CAG), an established precursor of gastric cancer, we performed a cross-sectional study using IgG antibody against H. pylori and pepsinogens of blood donors in four prefectures in Japan. Although a geographic correlation between the age-adjusted prevalence rates for H. pylori infection and those for CAG was not seen, the age-adjusted odds ratios (OR) of H. pylori infection for CAG were high in each area (around five for men and from four to 12.6 for women). The association between them weakened with advancing age; the ORs in the youngest age group (16-29 yrs) and in the oldest age group (50-64 yrs) were 12.5 and 2.8 for men, and 11.5 and 5.2 for women, respectively. These findings suggest that H. pylori infection is strongly associated with CAG, while there are some other factors interacting in the development of CAG. A prospective cohort study in which CAG and H. pylori infection are taken into account will be necessary to assess the risks of gastric cancer. 相似文献
8.
H Koh Y Hashimoto H Takagi K Hirota H Ishihara A Matsuki 《Canadian Metallurgical Quarterly》1993,42(2):217-224
The purpose of the study was to explore the relationship between the exposure of adolescents in the seventh and eighth grades to cigarette advertising and their being smokers. A survey questionnaire given to 602 adolescents assessed their exposure to cigarette advertising and provided measures of their smoking behavior, demographic characteristics, and some psychosocial variables. The results indicated that exposure to cigarette advertising and having friends who smoked were predictive of current smoking status. Adolescents with high exposure to cigarette advertising were significantly more likely to be smokers, according to several measures of smoking behavior, than were those with low exposure to cigarette advertising. The findings extend previous research identifying factors that may play a role in the initiation and maintenance of smoking among adolescents. 相似文献
9.
This paper presents stability results for discrete-time model-based predictive control system subject to an input amplitude constraint. It is shown that the input amplitude constrained control system may provide a stable control system in the sense of BIBO when the system to be controlled is of a class of the system poles which consist of multiple integrators and a stable polynomial. The solution of Diophantine equations and their properties are addressed. Simulation study is also carried out and it is shown that the output of the system may converge to the reference signal for certain degree of constraints. 相似文献
10.
This study has explored the potential energy surface on the chemical reaction of CH2OH with NO by using ab initio calculation. We have found the new reaction pathway producing N-hydroxy formamide, which can further decompose to generate isocyanic acid as a reducing agent of hydrocarbons selective catalytic reduction. 相似文献