全文获取类型
收费全文 | 13929篇 |
免费 | 298篇 |
国内免费 | 668篇 |
专业分类
系统科学 | 619篇 |
丛书文集 | 508篇 |
教育与普及 | 528篇 |
理论与方法论 | 176篇 |
现状及发展 | 56篇 |
综合类 | 13008篇 |
出版年
2024年 | 74篇 |
2023年 | 294篇 |
2022年 | 236篇 |
2021年 | 315篇 |
2020年 | 314篇 |
2019年 | 307篇 |
2018年 | 190篇 |
2017年 | 254篇 |
2016年 | 317篇 |
2015年 | 474篇 |
2014年 | 774篇 |
2013年 | 664篇 |
2012年 | 772篇 |
2011年 | 870篇 |
2010年 | 810篇 |
2009年 | 965篇 |
2008年 | 962篇 |
2007年 | 930篇 |
2006年 | 653篇 |
2005年 | 590篇 |
2004年 | 504篇 |
2003年 | 595篇 |
2002年 | 448篇 |
2001年 | 416篇 |
2000年 | 324篇 |
1999年 | 277篇 |
1998年 | 242篇 |
1997年 | 200篇 |
1996年 | 174篇 |
1995年 | 174篇 |
1994年 | 138篇 |
1993年 | 123篇 |
1992年 | 97篇 |
1991年 | 90篇 |
1990年 | 102篇 |
1989年 | 99篇 |
1988年 | 60篇 |
1987年 | 44篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1983年 | 4篇 |
1981年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
951.
对于有着悠久历史的国际法原则———国家豁免,不同时期不同国家会有着完全不同的立场。本文将立足国家豁免问题在发达国家的发展经验,结合发展中国家的现实,从中国的立场出发,去探讨中国应该采取怎样的国家豁免策略,以一种既有原则又不失灵活的谨慎方式解决所遇到的复杂问题。 相似文献
952.
953.
954.
Pt—Rh合金电极上氢的吸附过程的研究 总被引:1,自引:1,他引:0
贾梦秋 《北京化工大学学报(自然科学版)》1996,23(2):86-89,98
采用快速阴极动电位扫描方法对Pt-Rh合金电极上氢的吸附过程进行了研究。随着合金当中Rh含量的增加,氢的强键吸附峰值逐渐减少,在W(Rh)=50%-60%合金 已表现为象肩膀一样的平台,而到百分之百的Rh时完全消失。 相似文献
955.
956.
JIANGYanxia CHENWei LIAOHonggang JINLanying SUNShigang 《科学通报(英文版)》2004,49(15):1581-1585
Dispersed Pd nanoparticles (Pdn) have been synthesized by reducing H2PdCI4 with ethanol, and stabilized using poly(vinylpyrrolidone) (PVP). The Pdn is applied to the glassy carbon substrate to form a thin film, and then the potential cyclic scanning at 50 mV.s^-1 from -0.25 to 1.25 V was carried out for about 30 min to form the aggregations of Pdn (Pdn^ag). FTIR spectroscopy of both transmission and reflection modes was employed to study CO adsorption on Pdn and Pdn^ag in both solidlliquid and solidlgas interfaces. It has been revealed that CO adsorption on Pdn film yields two IRbands near 1964 and 1906 cm-1, which are assigned to IR absorption of CO bonded on asymmetric and symmetric bridge sites, respectively. In contrast to the IR properties of CO adsorbed on Pdn, only species of CO bonded on asymmetric bridge sites was determined on Pdn^ag, and the direction of the IR band near 1963 cm^-1 is completely inverted. The full width at half-maximum (FWHM) of the COB^as band near 1964 cm^-1 is measured to be 14 cm^-1 on Pdn film, while it is 24 cm^-1 on Pdn^ag film. The results of the present study demonstrated that the inverting of the IR band direction is a general phenomenon that is closely related to the interaction between nanoparticles in aggregation of Pdn. 相似文献
957.
西藏位于中国的西南边疆,是中国的西南大门。由于西藏战略地位的重要性,近代以来成为令人瞩目的地方,也成为中外学关注的重要区域之一。尤其是,所谓的“西藏问题”开始于近代,一些侵略分子竭力策动“西藏独立”,一些国际“知名人士”格外注意西藏近代社会的发展和变化。因而,西藏近代史 相似文献
958.
Science Letters:Synergetic effects for p-nitrophenol abatement using a combined activated carbon adsorption-electrooxidation process 总被引:1,自引:0,他引:1
A novel fluidized electrochemical reactor that integrated advanced electrochemical oxidation with activated carbon (AC) fluidization in a single cell was developed to model pollutant p-nitrophenol (PNP) abatement. AC fluidization could enhance COD removal by 22%-30%. In such a combined process, synergetic effects on PNP and COD removal was found, with their removal rate being enhanced by 137.8% and 97.8%, respectively. AC could be electrochemically regenerated and reused, indicating the combined process would be promising for treatment of biorefractory organic pollutants. 相似文献
959.
EAG and behavioral responses of Helicoverpa armigera males to volatiles from poplar leaves and their combinations with sex pheromone 总被引:2,自引:0,他引:2
Electroantennogram (EAG) evaluation of selected compounds from wilted leaves of black poplar, Populus nigra, showed that phenyl acetaldehyde, methyl salicylate, (E)-2-hexenal elicited strong responses from male antennae of Helicoverpa armigera. When mixed with sex pheromone (Ph), some volatiles, e.g. phenyl acetaldehyde, benzyl alcohol, phenylethanol, methylsalicylate, linalool, benzaldehyde, (Z)-3-hexenol, (Z)-3-hexenylacetate, (Z)-6-nonenol, cineole, (E)-2-hexenal, and geraniol elicited stronger responses from male antennae than Ph alone. Wind tunnel bioassay demonstrated that various volatiles could either enhance or inhibit the effect of synthetic sex pheromone. (E)-2-hexenal, (Z)-3-hexenol and linalool in combination with Ph could not induce any male to land on source at all, whereas phenyl acetaldehyde, benzaldehyde, (Z)-6-nonenol and salicylaldehyde combined with Ph enhanced male response rates by 58.63%, 50.33%, 51.85% and 127.78%, respectively, compared to Ph alone. These results suggested that some volatiles shouldmodify sex pheromone caused behavior and that some of them could possibly be used as a tool for disrupting mating or for enhancing the effect of synthetic sex pheromone in the field. 相似文献
960.
转轨经济中消费者行为变异分析 总被引:1,自引:0,他引:1
转轨经济中我国消费者消费行为发生了重大变异。探究消费者行为变异,了解现阶段我国居民消费行为特征及变化规律,对于制定有效的消费启动和引导政策、预测消费者需求变化趋势、优化消费结构及产业结构、制定产业政策和经济发展战略具有重要意义。 相似文献