全文获取类型
收费全文 | 32198篇 |
免费 | 3642篇 |
国内免费 | 1935篇 |
专业分类
电工技术 | 2251篇 |
技术理论 | 2篇 |
综合类 | 2497篇 |
化学工业 | 5154篇 |
金属工艺 | 1795篇 |
机械仪表 | 1906篇 |
建筑科学 | 2509篇 |
矿业工程 | 822篇 |
能源动力 | 918篇 |
轻工业 | 2612篇 |
水利工程 | 706篇 |
石油天然气 | 1527篇 |
武器工业 | 323篇 |
无线电 | 3972篇 |
一般工业技术 | 4400篇 |
冶金工业 | 1274篇 |
原子能技术 | 401篇 |
自动化技术 | 4706篇 |
出版年
2024年 | 228篇 |
2023年 | 688篇 |
2022年 | 1160篇 |
2021年 | 1458篇 |
2020年 | 1195篇 |
2019年 | 986篇 |
2018年 | 1081篇 |
2017年 | 1177篇 |
2016年 | 1055篇 |
2015年 | 1380篇 |
2014年 | 1674篇 |
2013年 | 2065篇 |
2012年 | 2125篇 |
2011年 | 2169篇 |
2010年 | 2025篇 |
2009年 | 1829篇 |
2008年 | 1716篇 |
2007年 | 1749篇 |
2006年 | 1718篇 |
2005年 | 1327篇 |
2004年 | 970篇 |
2003年 | 1035篇 |
2002年 | 1277篇 |
2001年 | 1087篇 |
2000年 | 754篇 |
1999年 | 741篇 |
1998年 | 551篇 |
1997年 | 488篇 |
1996年 | 423篇 |
1995年 | 335篇 |
1994年 | 272篇 |
1993年 | 224篇 |
1992年 | 202篇 |
1991年 | 135篇 |
1990年 | 106篇 |
1989年 | 80篇 |
1988年 | 62篇 |
1987年 | 43篇 |
1986年 | 45篇 |
1985年 | 20篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
BaTiO3 multilayer capacitors with a nominal capacitance of 3.5nF have been carefully measured using the thermally stimulated current (TSC) technique. When a 300V polarization voltage is applied at room temperature, a new TSC peak appeared in defective sample A after it has been immersed in water. No new peak was found in good-quality sample B after a similar treatment. The accelerated life test shows that sample A hasa much shorter life than sample B in terms of insulation resistance. 相似文献
172.
In this paper we present a Multi-Element generalized Polynomial Chaos (ME-gPC) method to deal with stochastic inputs with arbitrary probability measures. Based on the decomposition of the random space of the stochastic inputs, we construct numerically a set of orthogonal polynomials with respect to a conditional probability density function (PDF) in each element and subsequently implement generalized Polynomial Chaos (gPC) locally. Numerical examples show that ME-gPC exhibits both p- and h-convergence for arbitrary probability measures 相似文献
173.
本文通过对日本包装系统的考察和与中国包装现状的对比,阐述了“绿色”包装系统的基本理念和构建要素,总结出必须通过科技、法制等使包装产业形成一个系统化的“生态链”,使包装业真正造福于人类。 相似文献
174.
175.
Summary Cyclic tris(ethylene terephthalate) (CTET) was separated from oligomeric extract of poly(ethylene terephthalate) by the conventional solvent separation method. The structure of CTET was characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. It is shown that the double melting behavior of meltcrystallized CTET is attributed to the morphological change created by heat-treatment. The effect of the morphological change on the crystal structure of CTET was also examined. 相似文献
176.
177.
178.
179.
针对一起瓦斯流量计复线泄漏原因进行现场调查和原因分析,为了确保该系统长周期安全运行,提出相应的对策。 相似文献
180.
Outdoor log storage without protection can change the mechanical and chemical properties of wood due to infection by various fungi. To understand how outdoor log storage affects the wood and, subsequently, the strandboard quality, two piles of aspen logs were set up outside and stored for a period of four months (July to November). One of the piles was treated with a biological solution to prevent fungal growth. The other one was stored without treatment. Both piles contained non-debarked and partially debarked logs. Evaluation of sap stain development indicated that all logs had been colonized by staining fungi with average stain coverage of 9.37 to 57.18% and maximum stain penetration of 3.58 to 7.27 cm over the log cross section. The variation of fungal colonization depended on log treatment and bark condition. The most effective way to prevent stain growth was the combination of biological treatment and partial debarking. A series of strandboard was prepared from fresh and aged aspen logs. All boards made from stored logs were statistically comparable to or superior to the control boards made from fresh aspen logs. The boards made from treated/partially debarked and untreated/non-debarked logs were statistically comparable to each other except for wet MOR. In addition, these two board types were statistically stronger than other boards made from treated/non-debarked and untreated/partially debarked logs in terms of IB and water resistance. Some individual stained strands were observed on the finished board surface. Less staining was found in the boards prepared from biologically treated and partially debarked logs, compared with those made from other stored logs. 相似文献