全文获取类型
收费全文 | 3402篇 |
免费 | 187篇 |
国内免费 | 596篇 |
专业分类
化学 | 3721篇 |
晶体学 | 16篇 |
力学 | 61篇 |
综合类 | 16篇 |
数学 | 26篇 |
物理学 | 345篇 |
出版年
2024年 | 2篇 |
2023年 | 24篇 |
2022年 | 39篇 |
2021年 | 61篇 |
2020年 | 83篇 |
2019年 | 73篇 |
2018年 | 74篇 |
2017年 | 130篇 |
2016年 | 136篇 |
2015年 | 117篇 |
2014年 | 127篇 |
2013年 | 341篇 |
2012年 | 170篇 |
2011年 | 199篇 |
2010年 | 170篇 |
2009年 | 207篇 |
2008年 | 206篇 |
2007年 | 233篇 |
2006年 | 183篇 |
2005年 | 230篇 |
2004年 | 211篇 |
2003年 | 135篇 |
2002年 | 131篇 |
2001年 | 98篇 |
2000年 | 106篇 |
1999年 | 89篇 |
1998年 | 81篇 |
1997年 | 78篇 |
1996年 | 57篇 |
1995年 | 78篇 |
1994年 | 67篇 |
1993年 | 44篇 |
1992年 | 55篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有4185条查询结果,搜索用时 525 毫秒
111.
The morphology and the crystallization behavior of blends of linear low density polyethylene (LLDPE) with an experimental sample of a semiflexible liquid crystalline polymer (SBH 112 by Eniricerche, Italy) have been studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and scanning electron microscopy (SEM). The blends possess a two-phase morphology, due to immiscibility of the two components. SEM observations show that dispersion of the minor SBH phase is favored at low (相似文献
112.
A facile and environment friendly approach was developed to graft vinyl acetate (VAc) onto plastic articles in an aqueous solution using tert‐butyl alcohol (TBA) as a compatiblizer and benzoyl peroxide (BPO) as an initiator. In a novel setup, excessive monomer suspended in a water phase, VAc could be conveniently grafted on the model substrate of low‐density polyethylene (LDPE) film and the graft percentage (GP) could be developed up to 7.3%. Reaction temperature could increase GP significantly, while adding monomer over a critical volume did not influence GP. By adding some paradioxybenzene, i.e. 0.06–0.08% in VAc phase, homopolymer PVAc could be avoided practically, while graft polymerization proceeded favorably in aqueous solutions. It was proved by attenuated total reflection‐infrared (ATR‐IR) spectroscopy that grafted VAc was located mainly at the surface of the LDPE film and hydrophilic nature of both grafted and alcoholyzed films were improved via contact angle measurements. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
113.
The photon flux of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation of a hydrogen plasma with and without a MgF2window was recorded by fluorescence measurements of sodium salicylate layers. After the compensation of the MgF2absorption by increasing the input power into the plasma source, a comparison between afterglow hydrogen plasma and VUV treatments was made. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) were treated either with VUV radiation or with remote hydrogen plasma and mass loss and CH absorption loss were measured by a quartz crystal microbalance and by infrared reflection absorption spectroscopy, respectively. In the case of PE the effects of both treatments were found to be very similar white for PP slight differences were observed. For the actual set of experimental conditions, the radiation component is largely responsible for the efficiency of the plasma treatment. VUV and remote hydrogen plasma treatments of PS showed only a negligible loss of mass and CH absorption. 相似文献
114.
聚乙二醇蓄热调温性能及其在功能纺织品上的应用 总被引:12,自引:1,他引:12
对聚乙二醇(PEG)的自身交联及其与纤维素纤雏之间的交联反应进行了研究,探讨了交联前后PEG热活性的变化,并对PEG在焙烘交联时的受热稳定性以及分子量对热活性的影响进行了讨论。研究表明,PEG发生交联反应后,热性能参教产生偏移,热活性降低;热活性与分子量有直接关系;过高的焙烘温度将导致PEG氧化降解,热活性下降。在适宜的工艺条件下,纺织品经PEG后整理可获得热活性。 相似文献
115.
本文发展了一种高分子量聚合物熔融体的应力诱导结晶结构形态模型,它是由微晶聚集体(以下简称微区)-高分子链组网和缠结网的网络结构组成。基于上述模型,把二种网中的单个链组作为独立的统计单元和形变单元,计算了二种网中单个链组的末端距分布函数,进一步计算了二种网和总网的形变自由能。在此基础上,讨论了诱导结晶结晶机理和自增强聚合物网络自由能的依赖性,并着重地研究了超拉伸高聚物的起始熔点拉伸比间的关系。用超高分子量聚乙烯膜和超取向高密度聚乙烯纤维的起始熔点和拉伸比的实验数据进行处理,得到理论予期的近似直线关系,初步验证了聚合物网应力诱导结晶理论。 相似文献
116.
117.
Graziano Bonetti Patrick Pibarot Alain Chaintreau Jean Paul Marion 《Journal of separation science》1992,15(5):305-306
The use of diethylene glycol monoethyl ether as a flavor solvent is restricted. Since existing methods of quantitation are tedious or require sophisticated multi-dimensional GC instrumentation, a simple method has been developed using low cost GC-MS. Monitoring of ions 31 and 45 enables quantitation of DEGEE in essential oils at levels down to 1 μg/g with accuracy equal to or better than 15%. 相似文献
118.
The thermal conductivities of several nanofluids (dispersions of alumina nanoparticles in ethylene glycol) were measured at temperatures ranging from 298 to 411 K using a liquid metal transient hot wire apparatus. Our measurements span the widest range of temperatures that have been investigated to date for any nanofluid. A maximum in the thermal conductivity versus temperature behavior was observed at all mass fractions of nanoparticles, closely following the behavior of the base fluid (ethylene glycol). Our results confirm that additional temperature contributions inherent in Brownian motion models are not necessary to describe the temperature dependence of the thermal conductivity of nanofluids. Our results also show that the effect of mass or volume fraction of nanoparticles on the thermal conductivity of nanofluids can be correlated using the Hamilton and Crosser or Yu and Choi models with one adjustable parameter (the shape factor in the Hamilton and Crosser model, or the ordered liquid layer thickness in the Yu and Choi model). 相似文献
119.
本文中用紫外光敏化的方法对低密度聚乙烯进行了交联,并利用ESCA和ATR-IR等手段研究了交联后材抖的光稳定性及其改进办法。 相似文献
120.