全文获取类型
收费全文 | 21139篇 |
免费 | 1600篇 |
国内免费 | 889篇 |
专业分类
电工技术 | 1090篇 |
综合类 | 1383篇 |
化学工业 | 3646篇 |
金属工艺 | 1442篇 |
机械仪表 | 1200篇 |
建筑科学 | 1560篇 |
矿业工程 | 775篇 |
能源动力 | 492篇 |
轻工业 | 1356篇 |
水利工程 | 367篇 |
石油天然气 | 1532篇 |
武器工业 | 201篇 |
无线电 | 2179篇 |
一般工业技术 | 2766篇 |
冶金工业 | 1156篇 |
原子能技术 | 204篇 |
自动化技术 | 2279篇 |
出版年
2024年 | 109篇 |
2023年 | 362篇 |
2022年 | 656篇 |
2021年 | 906篇 |
2020年 | 707篇 |
2019年 | 593篇 |
2018年 | 614篇 |
2017年 | 718篇 |
2016年 | 605篇 |
2015年 | 868篇 |
2014年 | 1077篇 |
2013年 | 1191篇 |
2012年 | 1281篇 |
2011年 | 1480篇 |
2010年 | 1252篇 |
2009年 | 1215篇 |
2008年 | 1103篇 |
2007年 | 1196篇 |
2006年 | 1156篇 |
2005年 | 986篇 |
2004年 | 619篇 |
2003年 | 552篇 |
2002年 | 554篇 |
2001年 | 474篇 |
2000年 | 479篇 |
1999年 | 544篇 |
1998年 | 415篇 |
1997年 | 379篇 |
1996年 | 324篇 |
1995年 | 296篇 |
1994年 | 251篇 |
1993年 | 172篇 |
1992年 | 132篇 |
1991年 | 85篇 |
1990年 | 63篇 |
1989年 | 50篇 |
1988年 | 56篇 |
1987年 | 32篇 |
1986年 | 22篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Wei Chen Yongqing Zeng Jingxiang Cui Qimei Chen Jinfang Du Lun Yang Yanxia Hu Yiping Song Yuan Qian 《European Food Research and Technology》2011,232(3):433-440
Antioxidant enzymes protect muscle tissues against oxidation from reactive oxygen species and increase the stability of the muscle. Phospholipid hydroperoxide glutathione peroxidase (GPx4) is an important antioxidant enzyme in muscle tissue. So the aim of this study was to identify the effects of mRNA expression level of GPx4 gene on meat quality properties in Longissimus dorsi of three pig breeds. Total 36 pigs (12 pigs for each breed) were used to measure the meat quality properties and to analyze the expression levels of GPx4 gene by quantitative real-time PCR. The results showed that meat quality, GPx4 activity, and GPx4 mRNA levels were affected by pig breeds. There were the lowest expressible moisture, drip loss, and cooking loss in Laiwu Pig among the three breeds, and also there were the highest GPx4 activity and the expression levels of GPx4 gene in Laiwu Pig compared with the other two pig breeds. Analysis of meat samples divergent for water-holding capacity identified highly negative associations between expressions levels of GPx4 gene and expressible moisture, drip loss and cooking loss. These results suggest that the higher mRNA expression level of GPx4 gene up-regulate the water-holding capacity and the activity of GPx4, and the expression of GPx4 gene plays an important role in physiological changes related to the meat quality properties and the mechanisms of the antioxidant ion of meat. 相似文献
82.
83.
S. Cui Z.W. Chen J.D. Robson 《International Journal of Machine Tools and Manufacture》2010,50(12):1023-1030
Torque (M) is a very important quantity in the friction stir welding (FSW) process but a satisfactory model relating M to the two major FSW parameters, rotation speed (ω) and forward speed (v), has not been well developed. In this work, a better model of the form, M=f(ω, v), was sought. Experimentally, FSW of an aluminium alloy was conducted over a wide range of ω and v values and M was measured. An exponential decay function has been found to fit all the M versus ω data well and is meaningful for any ω value. The effect of v on M can approximately be accounted for through linearly relating the model parameters to v. The model allows for a detailed evaluation of the sensitivity of M to changes in ω and v. The model decay and the pre-exponential parameters need to be adjusted to make predictions for different aluminium alloys in the low ω range. Both the model and experimental data demonstrate a diminishing alloy effect on material flow resistance as ω increases. Furthermore, models of tool power (PTool) and specific energy (Es) can be derived from the model for M and give predictions that are also meaningful over the entire range of ω values. Finally, the dependences of PTool and Es on ω and v and the relationship between Es and the processing zone temperature will be discussed. 相似文献
84.
Yuncheng Cui Lihui Liu Chunbo Liu Qingwei Wang Wenlian Li Guangbo Che Chunhui Xu Mei Liu 《Synthetic Metals》2010,160(5-6):373-375
We report highly efficient visible-blind ultraviolet photodetectors based on 1,3,5-tris(3-methylphenyl-phenylamino)-triphenyamine (m-MTDATA) as donor and bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum (BAlq) as acceptor. Strong photoluminescence quenching of m-MTDATA by BAlq is observed manifesting the efficient photoinduced charge transfer occurs between m-MTDATA and BAlq. The optimized device exhibits a photocurrent of 172 μA/cm2 at ?14 V under an illumination of 365 nm UV light irradiation with an intensity of 0.691 mW/cm2, corresponding to a responsivity of 248 mA/W. We attribute the high response to the efficient electron transfer from the donor to the acceptor, the feasible level alignment match and the high carrier mobility of photoresponsive materials. 相似文献
85.
86.
87.
88.
89.
为了满足某高速卫星通信地球站调制解调器对多相插值滤波器的实际应用设计需要,分析了多相插值滤波器的一般设计原理,给出了一种多相插值滤波器的设计方法。采用VHDL语言TOP—DOWN设计方法,用XILINX VIRTEX-xv600系列FPGA进行了实现,对FPGA设计进行了仿真与测试。给出了部分仿真、实际应用测试结果。证明了设计的多相插值滤波器的正确性与可行性。 相似文献
90.
崔建平 《国外电子测量技术》2010,29(8):13-14
2010年6月28日,罗德与施瓦茨公司总裁和CEO Michael Vohrer先生在德国慕尼黑总部宣布:基于顺应用户需求,完善产品线配置,拓展公司增长空间三方面的考虑,罗德与施瓦茨推出两个系列6款示波器产品,从而结束了其T&M产品线没有示波器的历史。 相似文献