全文获取类型
收费全文 | 89374篇 |
免费 | 9385篇 |
国内免费 | 5550篇 |
专业分类
电工技术 | 6680篇 |
技术理论 | 7篇 |
综合类 | 5912篇 |
化学工业 | 16850篇 |
金属工艺 | 12933篇 |
机械仪表 | 4522篇 |
建筑科学 | 7703篇 |
矿业工程 | 3780篇 |
能源动力 | 2022篇 |
轻工业 | 7536篇 |
水利工程 | 2132篇 |
石油天然气 | 4954篇 |
武器工业 | 937篇 |
无线电 | 7382篇 |
一般工业技术 | 10196篇 |
冶金工业 | 6248篇 |
原子能技术 | 961篇 |
自动化技术 | 3554篇 |
出版年
2024年 | 401篇 |
2023年 | 1402篇 |
2022年 | 2514篇 |
2021年 | 3085篇 |
2020年 | 3192篇 |
2019年 | 2779篇 |
2018年 | 2704篇 |
2017年 | 3282篇 |
2016年 | 3421篇 |
2015年 | 3516篇 |
2014年 | 5384篇 |
2013年 | 4948篇 |
2012年 | 6566篇 |
2011年 | 6830篇 |
2010年 | 4959篇 |
2009年 | 5092篇 |
2008年 | 4492篇 |
2007年 | 5842篇 |
2006年 | 5425篇 |
2005年 | 4584篇 |
2004年 | 3890篇 |
2003年 | 3438篇 |
2002年 | 3025篇 |
2001年 | 2663篇 |
2000年 | 2235篇 |
1999年 | 1841篇 |
1998年 | 1357篇 |
1997年 | 1025篇 |
1996年 | 948篇 |
1995年 | 751篇 |
1994年 | 603篇 |
1993年 | 444篇 |
1992年 | 385篇 |
1991年 | 273篇 |
1990年 | 212篇 |
1989年 | 178篇 |
1988年 | 127篇 |
1987年 | 90篇 |
1986年 | 69篇 |
1985年 | 75篇 |
1984年 | 51篇 |
1983年 | 27篇 |
1982年 | 30篇 |
1981年 | 27篇 |
1980年 | 31篇 |
1964年 | 10篇 |
1963年 | 6篇 |
1959年 | 14篇 |
1956年 | 6篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
151.
The wettability of the lithium surface by liquid alkali metals Na, K and Rb is investigated for the first time by the sessile drop method in an all-soldered instrument under conditions of a high vacuum. The presence of the temperature threshold of wetting is found in Li–Na and Li–K systems at temperatures of 325°C and 160°C, respectively. A conclusion is drawn that an abrupt decrease in wetting angles in the investigated systems is associated with a marked decrease in the interfacial tension at lithium-lithium, lithium-potassium, and lithium--rubidium interfaces owing to the beginning of a noticeable mutual solubility of the components at relatively high temperatures. 相似文献
152.
高分子量丙烯酰胺-DAC共聚物的研制 总被引:7,自引:0,他引:7
采用复合引发体系 ,以丙烯酰胺 (AM)和阳离子单体丙烯酰氧乙基三甲基氯化铵(DAC)为共聚体 ,进行水溶液绝热聚合 ,研制了一种DAC单体含量为 4 0 %~ 5 0 %、相对分子质量大于 1× 10 7的阳离子型聚丙烯酰胺。 相似文献
153.
叙述了重钢公司几个高碳铬铁电炉使用全印度粉矿在冶炼过程中炉衬的损坏情况及其原因,提出了炉衬维护中应注意的几个方面。 相似文献
154.
G. H. Palmir 《Journal of the Institute of Brewing》1987,93(4):332-333
The aleurone cells of barley, wheat, rice, rye, oats and triticale contained, comparatively, higher percentages of phosphorus than the aleurone cells of sorghum, maize or millet. The aleurone tissues of barley, wheat and rice had more phosphate than corresponding tissues of sorghum and maize. Phosphate was not detected in the aleurone tissue of maize but was found in trace amounts in the aleurone tissue of sorghum. 相似文献
155.
156.
《功能材料信息》2007,(5)
A dream or interesting problem is to obtain more information based on one measurement,for example to obtain all the thermodynamic functions based on specific heat only. We call it“holographic“study.After more than 10 year‘s efforts,we suggest one possibility(or only one)is to solve an inverse problem(specific heat-phonon spectrum inversion,SPI).In this talk we will review recent development of studies of a class of inverse problems,including Dai‘s exact solution and Chen‘s formula and their unification.T... 相似文献
157.
This study tested a partial version of R. W. Lent, S. D. Brown, and G. Hackett's (1994) social-cognitive career theory model. Among 204 high school girls who attended science, math, and engineering (SME) career conferences, the authors used a 4-year longitudinal design to predict the choice of an SME college major and SME self-efficacy and outcome expectations in college. In addition, among students who had declared SME majors, variables assessed in high school and college were used to predict aspirations to become leaders in SME fields. The results generally provided empirical validation of the model. Regression analyses revealed that college SME outcome expectations were associated with plans to become a leader in an SME field. Implications for research and interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
158.
159.
采用喷射成形技术制备了Al1 0 Zn2 .9Mg1 .7Cu高强高韧铝合金沉积坯件 ,研究了喷射成形制备过程中各工艺参数对沉积坯件的成形性、显微组织、致密度的影响 ,确定了适当的工艺参数 ,研究了沉积坯件的热挤压及热处理工艺 ,对材料的组织进行了分析并对不同状态的材料性能进行了比较。研究结果表明 :当喷射成形工艺参数合理时 ,沉积坯件具有良好的成形性与致密度 ,在随后的热挤压过程中 ,通过较低的挤压比即可使材料达到全致密 ;通过对合金进行适当的热处理 ,材料的极限抗拉强度达到 810MPa ,同时延伸率保持在 8%~ 11% ,该材料是一种理想的轻质高强结构材料。 相似文献
160.
Boundary objects are a critical, but understudied, theoretical construct in CSCW. Through a field study of aircraft technical
support, we examined the role of boundary objects in the practical achievement of safety by service engineers. Their resolution
of repair requests was preserved in the organization’s memory via three compound boundary objects. These crystallizations
did not manifest a static interpretation, but instead were continually reinterpreted in light of meta-negotiations. This suggests
design implications for organizational memory systems which can more fluidly represent the meta-negotiations surrounding boundary
objects. 相似文献