全文获取类型
收费全文 | 45709篇 |
免费 | 5635篇 |
国内免费 | 3498篇 |
专业分类
电工技术 | 4587篇 |
技术理论 | 1篇 |
综合类 | 5237篇 |
化学工业 | 4141篇 |
金属工艺 | 1408篇 |
机械仪表 | 2523篇 |
建筑科学 | 3996篇 |
矿业工程 | 1244篇 |
能源动力 | 1285篇 |
轻工业 | 2377篇 |
水利工程 | 1244篇 |
石油天然气 | 2026篇 |
武器工业 | 705篇 |
无线电 | 5586篇 |
一般工业技术 | 4619篇 |
冶金工业 | 1772篇 |
原子能技术 | 707篇 |
自动化技术 | 11384篇 |
出版年
2024年 | 218篇 |
2023年 | 579篇 |
2022年 | 1135篇 |
2021年 | 1295篇 |
2020年 | 1641篇 |
2019年 | 1521篇 |
2018年 | 1343篇 |
2017年 | 1764篇 |
2016年 | 1954篇 |
2015年 | 2040篇 |
2014年 | 2809篇 |
2013年 | 3220篇 |
2012年 | 3219篇 |
2011年 | 3384篇 |
2010年 | 2510篇 |
2009年 | 2692篇 |
2008年 | 2595篇 |
2007年 | 3063篇 |
2006年 | 2817篇 |
2005年 | 2341篇 |
2004年 | 1898篇 |
2003年 | 1805篇 |
2002年 | 1563篇 |
2001年 | 1319篇 |
2000年 | 1152篇 |
1999年 | 880篇 |
1998年 | 706篇 |
1997年 | 624篇 |
1996年 | 487篇 |
1995年 | 414篇 |
1994年 | 345篇 |
1993年 | 273篇 |
1992年 | 193篇 |
1991年 | 186篇 |
1990年 | 135篇 |
1989年 | 105篇 |
1988年 | 87篇 |
1987年 | 77篇 |
1986年 | 51篇 |
1985年 | 62篇 |
1984年 | 47篇 |
1983年 | 35篇 |
1982年 | 33篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1964年 | 12篇 |
1959年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
阐述了一个全新的聚丙烯腈高聚物溶解理论,取代了以往人们思维中的高聚物大分子必须经过先溶胀再溶解的漫长的静态溶解过程。对于年产50kt/a腈纶装置可减少一次性投资约1500万元,减少运转费用360万元/a,在现有腈纶大装置上实施,经济效益十分可观。 相似文献
92.
塔巴庙区块气藏属于低压、低渗气藏,储集层物性差异大、含气级别高,但含气非均质性强,录井解释评价困难。针对这一问题,开展了综合判断储集层物性和含气性方面的研究,分别探讨了钻时与全烃、钻井液性能与全烃、钻井液粘度与全烃、气测显示与测井参数和烃组分与气显示之间的关系,分析了其相关性及其在塔巴庙区块气层解释评价中的意义及作用。通过相关性研究,不但摸索出定性解释评价气层的方法,同时为今后深入研究录井相关参数关系,探索其内在规律,为实现准确解释评价储集层奠定了基础。 相似文献
93.
Review of book: Stephen Mitchell. Can Love Last? The Fate of Romance Over Time. New York: Norton, 2002, 223 pp. Reviewed by Timothy J. Zeddies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
Yu. F. Smirnov 《Measurement Techniques》2007,50(3):293-297
Metrological characteristics of active hydrogen frequency standards are investigated on the basis of internal and external
comparisons. The stability of random changes and drift of hydrogen frequency standards and also the potential capabilities
of time scale preservation with effective consideration of systematic changes in their frequency are demonstrated.
__________
Translated from Izmeritel’naya Tekhnika, No. 3. pp. 42–45, March, 2007. 相似文献
95.
通过理论分析和实验研究液晶分子附着能和液晶盒间隙对响应时间(τ0)的影响。用液晶盒有效间隙法和表面动力学方程法两种方法推出分析公式,由这两种方法推出的结果是一致的。实验数据与简化方程τ0-dx基本拟合(其中d是液晶盒的间隙,x是指数)。在两种极端的(极大或极小)附着能极限下,指数x分别接近2和1。这个结论有助于优化液晶显示器件的应用。 相似文献
96.
97.
Amorphous SiNx:H films were prepared by the rf glow-discharge decomposition of ammonia/silane gas mixture with varying nitrogen content. The steady-state photoconductivity and its dependence on light intensity have been investigated in a-SiNx:H as a function of temperature between 100 and 420 K. The electron drift mobility of a set of SiNx:H samples has been determined from their steady-state photoconductivity and response time measurements. The results suggest that electron drift mobility of the samples was nearly unchanged for a low nitrogen content. Two samples containing lowest nitrogen showed higher photoconductivity than that of unalloyed sample within a temperature range including the room temperature. 相似文献
98.
Alpass Fiona; Flett Ross; Humphries Steve; Massey Claire; Morriss Stuart; Long Nigel 《Canadian Metallurgical Quarterly》2004,11(3):270
Previous studies have identified a number of different farm stressors and have reported gender and age differences in levels of stress. This study aimed to determine stress experienced by New Zealand dairy farmers, particularly in relation to adoption of new technology and its relationship to age and gender. Measures of farm stress and adoption of technology were completed by 985 dairy farmers. The highest levels of stress were reported for time pressures, machinery breakdown, weather, and government policies. Stress related to new technologies occurred rarely. Women reported more stress and higher levels of stress for understanding new technologies. There was also an increase in severity of stress with age related to new technologies. Overall, stress levels were moderate and may reflect favorable economic conditions. The findings suggest a need to tailor stress interventions to meet specific needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
Do experiences make people happier than material possessions? In two surveys, respondents from various demographic groups indicated that experiential purchases-those made with the primary intention of acquiring a life experience--made them happier than material purchases. In a follow-up laboratory experiment, participants experienced more positive feelings after pondering an experiential purchase than after pondering a material purchase. In another experiment, participants were more likely to anticipate that experiences would make them happier than material possessions after adopting a temporally distant, versus a temporally proximate, perspective. The discussion focuses on evidence that experiences make people happier because they are more open to positive reinterpretations, are a more meaningful part of one's identity, and contribute more to successful social relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
100.
Dynamic neural networks with different time-scales include the aspects of fast and slow phenomenons. Some applications require
that the equilibrium points of the designed networks are stable. In this paper, the passivity-based approach is used to derive
stability conditions for dynamic neural networks with different time-scales. Several stability properties, such as passivity,
asymptotic stability, input-to-state stability and bounded input bounded output stability, are guaranteed in certain senses.
A numerical example is also given to demonstrate the effectiveness of the theoretical results. 相似文献