全文获取类型
收费全文 | 3467篇 |
免费 | 103篇 |
国内免费 | 87篇 |
专业分类
电工技术 | 34篇 |
综合类 | 123篇 |
化学工业 | 108篇 |
金属工艺 | 116篇 |
机械仪表 | 72篇 |
建筑科学 | 222篇 |
矿业工程 | 31篇 |
能源动力 | 15篇 |
轻工业 | 73篇 |
水利工程 | 32篇 |
石油天然气 | 40篇 |
武器工业 | 24篇 |
无线电 | 101篇 |
一般工业技术 | 243篇 |
冶金工业 | 2319篇 |
原子能技术 | 27篇 |
自动化技术 | 77篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 45篇 |
2021年 | 47篇 |
2020年 | 37篇 |
2019年 | 37篇 |
2018年 | 36篇 |
2017年 | 35篇 |
2016年 | 23篇 |
2015年 | 43篇 |
2014年 | 43篇 |
2013年 | 72篇 |
2012年 | 77篇 |
2011年 | 75篇 |
2010年 | 72篇 |
2009年 | 76篇 |
2008年 | 64篇 |
2007年 | 85篇 |
2006年 | 101篇 |
2005年 | 68篇 |
2004年 | 52篇 |
2003年 | 50篇 |
2002年 | 45篇 |
2001年 | 29篇 |
2000年 | 28篇 |
1999年 | 97篇 |
1998年 | 679篇 |
1997年 | 424篇 |
1996年 | 265篇 |
1995年 | 158篇 |
1994年 | 134篇 |
1993年 | 179篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 32篇 |
1989年 | 42篇 |
1988年 | 22篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1978年 | 6篇 |
1977年 | 59篇 |
1976年 | 135篇 |
1975年 | 6篇 |
1955年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有3657条查询结果,搜索用时 15 毫秒
41.
分别采用常规黑白金相、彩色金相、微差干涉衬度试验方法对长纤维增强、短纤维增强、颗粒增强金属基复合材料显微组织进行了研究,结果表明:三种试验方法虽各有其自己的优缺点,但微差干涉衬度试验方法具有一定的优越性. 相似文献
42.
利用表面机械加工法在具有回火索氏体组织的38CrSi合金钢表面制备了纳米结构层,利用X射线衍射和透射电镜等分析技术,对距表面不同深度处渗碳体相的微观结构特征及物相组成进行研究,分析38CrSi合金钢表面纳米化过程中渗碳体相的细化过程.结果表明,铁素体基体细化过程中,渗碳体颗粒在切变力作用下形成细小颗粒的同时还发生了溶解.在应变量和应变速度较高的最表面,渗碳体颗粒溶解较严重,分析表明高密度位错产生的高界面能、应力集中以及能量波动是使得渗碳体颗粒发生切变和溶解主要原因. 相似文献
43.
During the past several years, giant magneto-impedance effect (GMI) in amorphous wires has generated growing interest in the science community because of theirapplications in sensors. The giant magneto-impedance effect in Co71.8Fe4.9Nb0.8Si7.5B15 amorphous glass-covered wires (AGCW) consists of strong changes in the high frequency impedance with a small DC magnetic field. When f =1 MHz, there is no GMI effect due to the fact that the magnetic penetration depth is higher than their radius. As the frequency increases, the GMI effect becomes important in both the glass-covered wire and the wire afterglass removal. Field dependence of the impedance has a similar behaviour to the AGCW ones, when a tensile stress is applied to the wire without glass cover. 相似文献
44.
45.
46.
LIU Yanping CHEN Zhaoyang BA Weizhen FAN Yanwei GUO Qi YU Xuefeng CHANG Aiming LU Wu DU Yanzhao 《核技术(英文版)》2008,19(2):113-116
Alkaline earth sulfides (MgS, CaS and BaS) crystal doped with rare-earth ions is an optically stimulated luminescence dosimeter with very high sensitivity, short time constant of the optically stimulated luminescence (OSL)separated perfectly from the stimulation. In this paper, an OSL dosimeter is described. It has linear dose response from 0.01 to 1000 Gy. The equipment, relatively simple and small in size is promising for applications in space exploration and for high dose irradiation and dangerous irradiation conditions. 相似文献
48.
Effects of growth hormone, insulin-like growth factor-I, and cortisol on periparturient antibody response profiles of dairy cattle 总被引:2,自引:0,他引:2
The objectives of this study were to determine hormone and antibody response profiles from the prepartum period to peak lactation, and evaluate potential immunomodulatory effects of the classic endocrine hormones, growth hormone (GH), insulin-like growth factor-I (IGF-I) and cortisol. Specifically, 33 Holstein cows were immunized with ovalbumin (OVA) and Escherichia coli J5 at weeks -8 and -3 prior to parturition. At parturition (week 0), cows received an additional immunization of OVA. Blood was collected at weeks -8, -3, 0, 3 and 6 relative to parturition and various samples were used to determine plasma hormone concentration, serum immunoglobulin (Ig), and specific antibody response to OVA and E. coli. Colostrum and milk samples were also collected post-parturition to monitor local immunoglobulin and antibody responses. Results indicated that not all periparturient cows exhibited depressed immune response, and that antibody response to OVA could be used to partition cows into 3 groups recognizing animals with sustained measurable antibody response before and after parturition (Group 1), animals which responded poorly to immunization at parturition (Group 2), and animals which did not respond to immunizations at week -3 or parturition (Group 3). Cows with the highest antibody response to OVA (Group 1) also tended (P < or = 0.10) to have the highest response to E. coli J5 at parturition and had the lowest incidence of disease, particularly mastitis. Antibody response to OVA measured in milk tended to be higher in Group 1 cows, particularly at week 0 (P < or = 0.06) compared to cows of Group 3. IGF-I was higher (P < or = 0.05) in cows of Group 1 than Group 3 at peak lactation (week 6). 相似文献
49.
50.