全文获取类型
收费全文 | 6769篇 |
免费 | 768篇 |
国内免费 | 422篇 |
专业分类
电工技术 | 128篇 |
综合类 | 712篇 |
化学工业 | 1774篇 |
金属工艺 | 84篇 |
机械仪表 | 225篇 |
建筑科学 | 357篇 |
矿业工程 | 46篇 |
能源动力 | 72篇 |
轻工业 | 1484篇 |
水利工程 | 48篇 |
石油天然气 | 75篇 |
武器工业 | 18篇 |
无线电 | 373篇 |
一般工业技术 | 393篇 |
冶金工业 | 295篇 |
原子能技术 | 38篇 |
自动化技术 | 1837篇 |
出版年
2024年 | 31篇 |
2023年 | 139篇 |
2022年 | 540篇 |
2021年 | 453篇 |
2020年 | 238篇 |
2019年 | 183篇 |
2018年 | 181篇 |
2017年 | 218篇 |
2016年 | 230篇 |
2015年 | 280篇 |
2014年 | 408篇 |
2013年 | 445篇 |
2012年 | 460篇 |
2011年 | 469篇 |
2010年 | 395篇 |
2009年 | 383篇 |
2008年 | 436篇 |
2007年 | 433篇 |
2006年 | 369篇 |
2005年 | 287篇 |
2004年 | 245篇 |
2003年 | 222篇 |
2002年 | 142篇 |
2001年 | 121篇 |
2000年 | 95篇 |
1999年 | 84篇 |
1998年 | 63篇 |
1997年 | 65篇 |
1996年 | 54篇 |
1995年 | 62篇 |
1994年 | 37篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 27篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1964年 | 3篇 |
1963年 | 3篇 |
1961年 | 4篇 |
1957年 | 2篇 |
排序方式: 共有7959条查询结果,搜索用时 0 毫秒
1.
吴敬东 《湖南工业职业技术学院学报》2015,(2):137-140
高校是培养人才的摇篮,肩负着科教兴国、人才强国两大历史性战略任务。由于社会环境的复杂化,人际关系的交错性,新时代的大学生行为状况给高校学生管理工作带来了新的挑战。针对新时期大学生行为特点,我们通过加强党建工作、强化学风建设、做好班级自主管理和深化社会服务四个方面工作进行分析,提出了全面引导、约束、规范和优化大学生的行为的建议和对策,从而有效解决新形势下普通高校学生管理工作的实际困难。 相似文献
2.
3.
Ph. D. Candidate:Chen Xue-fengState Key Laboratory of Offshore Coastal Engineering Dalian University of Technology Dalian China e-mail: cxfeng @ student dlut. edu.cn 《水动力学研究与进展(B辑)》2003,15(6)
The reflection coefficient of perforated caissons and the total horizontal forces acting on them were experimentally and numerically analyzed and discussed when wave propagates normally. To consider the viscosity effect of fluid and nonlinear action of waves on structures, the VOF (Volume Of Fluid) method combined with the k-ε turbulence model was used to simulate the interaction between waves and structures. Governing equations were solved with the finite difference method. Through 2D experimental study in the wave flume, the empirical relationship between the reflection coefficient of perforated caissons and the main affecting factors were obtained from the experimental data using the least square method. Also the correlation between the ratio of the total horizontal force acting on perforated caisson and the force acting on solid caisson and the main affecting factors were regressed from the experimental data. 相似文献
4.
一类Feistel密码的线性分析 总被引:5,自引:0,他引:5
该文提出一种新的求取分组密码线性偏差上界的方法,特别适用于密钥线性作用的Feistel密码.该分析方法的思路是,首先对密码体制线性偏差进行严格的数学描述,分别给出密码线性偏差与轮函数F及S盒的线性偏差的数学关系;然后通过求取线性方程组最小重量解,确定密码线性偏差的上界. 相似文献
5.
6.
7.
Yu Zheng Haiyi Zhang Li Zhao Liujing Wei Xingyuan Ma Dongzhi Wei 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1409-1412
BACKGROUND: 2,3‐Butanediol (2,3‐BD) is a valuable chemical that can be biosynthesized from many kinds of substrates. For commercial biological production of 2,3‐BD, it is desirable to use cheap substrate without pretreatment, such as starch. However, there have been few reports on the production of 2,3‐BD directly from starch. RESULTS: In this work, gene malS coding for α‐amylase (EC 3.2.1.1) precursor was inserted into plasmid pUC18K, and secretory over‐expression of α‐amylase was achieved by engineered Klebsiella pneumoniae. The extracellular recombinant amylase accelerated the hydrolyzation of starch, and one‐step production of 2,3‐BD from starch was carried out by engineered K. pneumoniae. A 2,3‐BD concentration of 3.8 g L?1 and yield of 0.19 g 2,3‐BD g?1 starch were obtained after 24 h fermentation. CONCLUSION: The one‐step production of 2,3‐BD from starch was achieved by secretory over‐expression of amylase in K. pneumoniae. This would simplify the process and reduce the production cost considerably by enabling use of starch with minimal pretreatment. Copyright © 2008 Society of Chemical Industry 相似文献
8.
9.
Raphaëlle Savoire Jean‐Louis Lanoisellé Hélène Ducatel Eugène Vorobiev 《European Journal of Lipid Science and Technology》2008,110(8):725-734
Seven linseed varieties were harvested at seven times before complete maturity. Microscale oilseed expressions were subsequently carried out on it. A pressure of 10 MPa was applied for 1 h under uniaxial stress. The results were characterized in terms of oil, water and mucilage content, harvest date and oil yield. The piston displacement versus time (creep curves) was described by a four‐Kelvin‐Voigt elements viscoelastic model. Parameters were derived from the model, such as the mechanical properties of seeds (compressibility moduli), showing that the viscoelastic model fits well the experimental data (R² ≈ 0.999). The modeling parameters were combined with some biochemical data in order to predict the kinetics of oil extraction. 相似文献
10.