全文获取类型
收费全文 | 1468篇 |
免费 | 53篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 228篇 |
金属工艺 | 26篇 |
机械仪表 | 40篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 190篇 |
轻工业 | 62篇 |
水利工程 | 9篇 |
石油天然气 | 9篇 |
无线电 | 196篇 |
一般工业技术 | 284篇 |
冶金工业 | 130篇 |
原子能技术 | 8篇 |
自动化技术 | 304篇 |
出版年
2023年 | 21篇 |
2022年 | 43篇 |
2021年 | 84篇 |
2020年 | 55篇 |
2019年 | 56篇 |
2018年 | 78篇 |
2017年 | 41篇 |
2016年 | 40篇 |
2015年 | 40篇 |
2014年 | 49篇 |
2013年 | 87篇 |
2012年 | 55篇 |
2011年 | 37篇 |
2010年 | 40篇 |
2009年 | 55篇 |
2008年 | 48篇 |
2007年 | 59篇 |
2006年 | 43篇 |
2005年 | 33篇 |
2004年 | 20篇 |
2003年 | 21篇 |
2002年 | 25篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 22篇 |
1998年 | 44篇 |
1997年 | 35篇 |
1996年 | 27篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 38篇 |
1984年 | 17篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1973年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有1524条查询结果,搜索用时 125 毫秒
1.
Wireless Personal Communications - Now-a-days the most common pretentious disease is the lung cancer, which has become more prevalent in the world that primarily infects the pulmonary nodules of... 相似文献
2.
Food Science and Biotechnology - The process of cellular senescence is rapidly emerging as a modulator of organismal aging and disease. Targeting the development and removal of senescent cells is... 相似文献
3.
4.
Kumari Asha Neeraj Kumar Biswas Sakshi Saxena Vibha Rani Satsangi Rohit Shrivastav Rama Kant Sahab Dass 《International Journal of Hydrogen Energy》2021,46(40):20858-20870
The present study attempts quantitative determination of changes in the morphological surface features viz. fractal dimension, lower and upper cut off length scale through Power Spectral Density analysis prior to and after irradiation of 100 KeV Ar+ ion beam at incidence angles of 0°, 40° and 60° on ZnO thin films. All the unirradiated and irradiated samples are subjected to photoelectrochemical characterization and a correlation between photoelectrochemical performance and morphological parameters is established. Sample irradiated at 40° angle at the fluence of 5 × 1016 ions/cm2 is found to possess maximum fractal dimension of 2.72, lower and upper cut off length scale of 3.16 nm and 63.00 nm respectively. This sample exhibits maximum photocurrent density of 3.19 mA/cm2 and applied bias photon-to-current efficiency of 1.12% at 1.23 V/RHE. Hydrogen gas collected for duration of 1 h for the same sample was ~4.83 mLcm?2. 相似文献
5.
Effects of DEM Source,Spatial Resolution and Drainage Area Threshold Values on Hydrological Modeling
Water Resources Management - Automated computation of hydrological and morphometric parameters of any watershed are not only depended on Digital Elevation Model (DEM) resolution but also affected... 相似文献
6.
7.
In this article, linear programming and fuzzy optimization models are developed for planning and management of available land-water-crop system of Mahanadi-Kathajodi delta in eastern India. The models are used to optimize the economic return, production and labour utilization, and to search the related cropping patterns and intensities with specified land, water, fertilizer and labour availability, and water use pattern constraints. Due to extreme backwardness of the study area, it has been decided to keep all the three objectives of the linear programming models at the same priority level to obtain the compromised solution in a fuzzy environment that incorporates the imprecision in fuzzy goals and fuzzy constraints. These non-structural models facilitate the conjunctive use of available surface water and groundwater resources. A comparative evaluation along with the benefit-cost ratios of the existing and proposed farming systems is also presented. 相似文献
8.
9.
10.
While seeds ofCucurbita maxima contain both Δ5- and Δ7-sterols, the former, which have been described earlier, now have been found to disappear during germination. This suggests
that a function exists for the Δ5-compounds only in the early part of the life cycle ofC. maxima, unlike most of the other higher plants studied. In contrast to the Δ5-sterols, the level of Δ7-sterols increased during germination as well as during seedling development and maturation. The period of transition between
germination and seedling development appeared to be of special importance in terms of sterol changes. This period represented
a surge of sterol biosynthesis with an ontogenetic shift in sterol composition from approximately equal amounts of 24α- and
24β-ethyl stereochemistry to a predominance of the former. The sterol composition of the mature plants included only about
5% of the 24β-ethylsterols. The configurational relationships were demonstrated by high resolution1H-NMR. The sterols of the mature plants were: 25(27)-dehydrochondrillasterol, 24β-ethyl-25(27)-dehydrolathosterol, avenasterol,
spinasterol, 22-dihydrospinasterol and 24ξ-methyllathosterol. Based on the changes which occurred in the relative amounts
of the Δ7-sterols, it did not appear that the Δ5-components were being converted to their Δ7-analogs.
A portion of this work was presented at the meeting of the American Oil Chemists' Society in May, 1985 in Philadelphia. 相似文献