全文获取类型
收费全文 | 12524篇 |
免费 | 1186篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 120篇 |
综合类 | 7篇 |
化学工业 | 2953篇 |
金属工艺 | 171篇 |
机械仪表 | 324篇 |
建筑科学 | 654篇 |
矿业工程 | 46篇 |
能源动力 | 301篇 |
轻工业 | 2386篇 |
水利工程 | 93篇 |
石油天然气 | 35篇 |
无线电 | 980篇 |
一般工业技术 | 2298篇 |
冶金工业 | 918篇 |
原子能技术 | 54篇 |
自动化技术 | 2383篇 |
出版年
2024年 | 21篇 |
2023年 | 172篇 |
2022年 | 132篇 |
2021年 | 419篇 |
2020年 | 338篇 |
2019年 | 368篇 |
2018年 | 474篇 |
2017年 | 470篇 |
2016年 | 616篇 |
2015年 | 528篇 |
2014年 | 690篇 |
2013年 | 1229篇 |
2012年 | 1059篇 |
2011年 | 879篇 |
2010年 | 645篇 |
2009年 | 637篇 |
2008年 | 688篇 |
2007年 | 598篇 |
2006年 | 540篇 |
2005年 | 370篇 |
2004年 | 345篇 |
2003年 | 283篇 |
2002年 | 303篇 |
2001年 | 163篇 |
2000年 | 165篇 |
1999年 | 131篇 |
1998年 | 171篇 |
1997年 | 139篇 |
1996年 | 126篇 |
1995年 | 104篇 |
1994年 | 96篇 |
1993年 | 89篇 |
1992年 | 64篇 |
1991年 | 56篇 |
1990年 | 41篇 |
1989年 | 44篇 |
1988年 | 30篇 |
1987年 | 29篇 |
1986年 | 34篇 |
1985年 | 42篇 |
1984年 | 51篇 |
1983年 | 28篇 |
1982年 | 31篇 |
1981年 | 27篇 |
1980年 | 31篇 |
1979年 | 36篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 16篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Astrid Labidi Marie-Christine Salon Alessandro Gandini Hervé Cheradame 《Polymer Bulletin》1985,14(3-4):271-278
Summary 2-Furyl vinyl ketone was polymerised using anionic, cationic and free-radical initiators. Yields and molecular weights varied with the type of activation. Whereas radical polymerisation gave a product possessing a regular vinylic structure, other kinds of units were detected in the polymers prepared with anionic and cationic catalysts. 相似文献
34.
We compare two link analysis ranking methods of web pages in a site. The first, called Site Rank, is an adaptation of PageRank to the granularity of a web site and the second, called Popularity Rank, is based on the frequencies of user clicks on the outlinks in a page that are captured by navigation sessions of users through
the web site. We ran experiments on artificially created web sites of different sizes and on two real data sets, employing
the relative entropy to compare the distributions of the two ranking methods. For the real data sets we also employ a nonparametric
measure, called Spearman's footrule, which we use to compare the top-ten web pages ranked by the two methods. Our main result
is that the distributions of the Popularity Rank and Site Rank are surprisingly close to each other, implying that the topology
of a web site is very instrumental in guiding users through the site. Thus, in practice, the Site Rank provides a reasonable
first order approximation of the aggregate behaviour of users within a web site given by the Popularity Rank. 相似文献
35.
Norris Fran H.; Murphy Arthur D.; Baker Charlene K.; Perilla Julia L.; Rodriguez Francisco Gutiérrez; Rodriguez José de Jesús Gutiérrez 《Canadian Metallurgical Quarterly》2003,112(4):646
Prevalence rates of trauma and posttraumatic stress disorder (PTSD) were estimated from a probability sample of 2,509 adults from 4 cities in Mexico. PTSD was assessed according to Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) criteria using the Composite International Diagnostic Interview (CIDI; WHO, 1997). Lifetime prevalence of exposure and PTSD were 76% and 11.2%, respectively. Risk for PTSD was highest in Oaxaca (the poorest city), persons of lower socioeconomic status, and women. Conditional risk for PTSD was highest following sexual violence, but nonsexual violence and traumatic bereavement had greater overall impact because of their frequency. Of lifetime cases, 62% became chronic; only 42% received medical or professional care. The research demonstrates the importance of expanding the epidemiologic research base on trauma to include developing countries around the world. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
A self‐consistent texture model is implemented in the finite‐element code ABAQUS/Explicit®. Hardening of the slip systems is described by evolution laws for dislocation densities, and the Bauschinger effect is included. With these ingredients the cold rolling of an IF‐steel is simulated and the evolution of texture and anisotropy is examined. The use of the dislocation based hardening law is found to have a significant effect on the evolution of the anisotropic yield surface, but only very little influence on the texture. Furthermore, the hardening model is used to investigate the evolution of dislocation densities in differently oriented grains during plane strain compression. It is found that the dislocation density varies greatly depending on orientation, an observation which can help to explain the orientation dependence of recrystallization. 相似文献
37.
Tom Mariano 《集成电路应用》2008,(11):25-25
在近期一次SEMI产业策略论坛发表的演讲中,Lam Research Corp.的总裁兼CEO Stephen Newberry认为,半导体产业已经进入了“无利的繁荣时代”。2003年以来,每比特/功能的价格已经比每比特/价格的成本下降得更快,使得整个产业的利润遭到侵蚀。这似乎成为了一个无法维继的市场,随着时间的推移必须进行自我修正才行。 相似文献
38.
Sebastián López Gustavo M. Callicó Félix Tobajas Valentín de Armas José F. López Roberto Sarmiento 《ETRI Journal》2008,30(6):862-864
This letter presents a novel approach for organizing computational resources into groups within H.264/AVC motion estimation architectures, leading to reductions of up to 75% in the equivalent gate count with respect to state‐of‐the‐art designs. 相似文献
39.
40.
Formaldehyde is used in ruminant feeding for different purposes including the protection of dietary proteins from ruminal degradation. The formaldehyde content of milk of goats fed various levels of formaldehyde-treated soybean oil-meal has been determined by using a sensitive HPLC method. Results showed a significant linear correlation between ingested formaldehyde and formaldehyde concentration in milk. About 0.02% of ingested formaldehyde was excreted in milk, as free formaldehyde. 相似文献