全文获取类型
收费全文 | 6934篇 |
免费 | 775篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 111篇 |
综合类 | 6篇 |
化学工业 | 2032篇 |
金属工艺 | 225篇 |
机械仪表 | 429篇 |
建筑科学 | 65篇 |
矿业工程 | 2篇 |
能源动力 | 376篇 |
轻工业 | 702篇 |
水利工程 | 12篇 |
石油天然气 | 5篇 |
无线电 | 1176篇 |
一般工业技术 | 1689篇 |
冶金工业 | 250篇 |
原子能技术 | 104篇 |
自动化技术 | 537篇 |
出版年
2024年 | 10篇 |
2023年 | 86篇 |
2022年 | 157篇 |
2021年 | 233篇 |
2020年 | 174篇 |
2019年 | 267篇 |
2018年 | 274篇 |
2017年 | 291篇 |
2016年 | 378篇 |
2015年 | 294篇 |
2014年 | 432篇 |
2013年 | 500篇 |
2012年 | 538篇 |
2011年 | 624篇 |
2010年 | 466篇 |
2009年 | 435篇 |
2008年 | 356篇 |
2007年 | 300篇 |
2006年 | 259篇 |
2005年 | 202篇 |
2004年 | 193篇 |
2003年 | 183篇 |
2002年 | 173篇 |
2001年 | 147篇 |
2000年 | 144篇 |
1999年 | 124篇 |
1998年 | 106篇 |
1997年 | 68篇 |
1996年 | 52篇 |
1995年 | 45篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 24篇 |
1991年 | 19篇 |
1990年 | 17篇 |
1989年 | 27篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有7721条查询结果,搜索用时 15 毫秒
991.
Ha Hyunho Nam Seunghoon Jeong Soo-Hwan Hyun Seungmin 《Journal of Mechanical Science and Technology》2019,33(8):3865-3870
Journal of Mechanical Science and Technology - Sodium (Na) organic batteries have attracted great attention because of high abundance of Na, low-production cost, and structure diversity of organic... 相似文献
992.
Kwon Hyun Min Moon Seong Won Kim Tong Seop Kang Do Won Sohn Jeong Lak Lee Jungho 《Journal of Mechanical Science and Technology》2019,33(9):4535-4543
Journal of Mechanical Science and Technology - This study investigates the possibility of achieving 65 % efficiency in a gas turbine combined cycle. Several options to realize it were compared. A... 相似文献
993.
994.
995.
996.
Dea Seok Yoo Yeon Hee Choi Mi Ran Cha Byung Hoe Lee Sun-Ju Kim Gyu Hwan Yon Kyung Sik Hong Yu Seon Jang Hyun Sun Lee Young Sup Kim Shi Yong Ryu Jong Seong Kang 《Food chemistry》2011
An effective HPLC method to analyse platycosides from the balloon flower root was developed using ELSD. The optimum resolution of the platycosides was achieved on an ODS column with gradient elution of eluent A, 30 mM ammonium acetate buffer (pH 4.81): methanol: acetonitrile = 75:5:20 (v/v/v), and B, 69:5:26 (v/v/v). Amongst 18 platycosides, platycoside E showed the highest content, followed by polygalacin D2 and 3″-O-acetylplatyconic acid A. The sum of these three compounds was recommended for quality control of balloon flower root for medicinal purposes. The samples could be clustered into groups based on platycoside content. Group I, characterised by a high concentration of platycosides, was located near the west coast of Korea, whereas group II, characterised by a low concentration of platycosides, was located inland or in mountainous area. The method could be used to control the quality of balloon flower root. 相似文献
997.
In order to obtain basic data for the utilisation of Zanthoxylum piperitum leaf as a functional substance in the food industry, the antioxidative and neuronal cell protective effects of silica-gel open column chromatographic fractions, obtained from Z. piperitum leaf, were examined. ABTS and FRAP assays indicated that the ZP4 fraction (eluted with methanol/chloroform, 1:4, v/v) of Z. piperitum leaf was a more potent radical-scavenger and reducing agent than the other five fractions. The ZP4 fraction also presented protective effects against H2O2-induced neurotoxicity in a dose-dependent manner. Therefore, our study verified that the ZP4 fraction has strong antioxidative and neuronal protective effects which are correlated with its high level of phenolics, particularly quercitrin, afzelin, and hyperoside. These phenolics of Z. piperitum leaf can be utilised as effective and safe functional food substances, i.e., natural antioxidants, and may reduce the risk of neurodegenerative disorders. 相似文献
998.
The area and pressure distribution in elastic contacts between frictionless, nonadhesive surfaces is studied as a function of load and surface geometry using finite element calculations. Surfaces that follow self-affine scaling on all resolved scales are compared to surfaces with cutoffs at small and large length scales, and experimental surfaces that are not self-affine. In all cases the true area of contact is proportional to load and inversely proportional to elastic modulus and the mean slope of the surface. The constant of proportionality κ is nearly constant and lies between analytic predictions. Large wavelength cutoffs lead to a small increase in κ, a homogeneous distribution of contacts at large scales, and limit the size of the largest connected regions. Small wavelength cutoffs lead to local redistributions in pressure that decrease the probability of low and high local pressures. 相似文献
999.
Jung-Young Kim Sang-Hak Hyun Hong-Hee Yoo 《Journal of Mechanical Science and Technology》2002,16(7):896-901
This paper presents a nonlinear modeling method for dynamic analysis of flexible structures undergoing overall motions that
employs the mode approximation method. This method, different from the naive nonlinear method that approximates only Cartesian
deformation variables, approximates not only deformation variables but also strain variables. Geometric constraint relations
between the strain variables and the deformation variables are introduced and incorporated into the formulation. Two numerical
examples are solved and the reliability and the accuracy of the proposed formulation are examined through the numerical study. 相似文献
1000.
O. A. EI-Samni Hyun Sik Yoon Ho Hwan Chun 《Journal of Mechanical Science and Technology》2005,19(9):1801-1810
The effect of longitudinal thin rectangular riblets aligned with the flow direction on turbulent channel flow has been investigated
using direct numerical simulation. The thin riblets have been modeled using the immersed boundary method (IBM) where the velocities
at only one set of vertical nodes at the riblets positions are enforced to be zeros. Different spacings, ranging between 11
and 43 wall units, have been simulated aiming at getting the optimum spacing corresponding to the maximum drag reduction while
keeping the height/spacing ratio at 0.5. Reynolds number based on the friction velocityuτ and the channel half depth δ is set to 150. The flow is driven by adjusted pressure gradient so that the mass flow rate is
kept constant in all the simulations. This study shows similar trend of the drag ratio to that of the experiments at the different
spacings. Also, this research provides an optimum spacing of around 17 wall units leading to maximum drag reduction as experimental
data. Explanation of drag increasing/ decreasing mechanism is highlighted. 相似文献