全文获取类型
收费全文 | 224篇 |
免费 | 12篇 |
国内免费 | 30篇 |
专业分类
化学 | 169篇 |
晶体学 | 2篇 |
力学 | 8篇 |
综合类 | 1篇 |
数学 | 37篇 |
物理学 | 49篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 16篇 |
2012年 | 19篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 13篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有266条查询结果,搜索用时 15 毫秒
91.
Let m be a positive integer, 0 < α < mn, $\overrightarrow b $ = (b 1, …, b m ) ε BMO m . We give sufficient conditions on weights for the commutators of multilinear fractional integral operators ${\rm I}_a^{\overrightarrow b }$ to satisfy a weighted endpoint inequality which extends the result in D. Cruz-Uribe, A. Fiorenza: Weighted endpoint estimates for commutators of fractional integrals, Czech. Math. J. 57 (2007), 153–160. We also give a weighted strong type inequality which improves the result in X. Chen, Q. Xue: Weighted estimates for a class of multilinear fractional type operators, J. Math. Anal. Appl., 362, (2010), 355–373. 相似文献
92.
93.
94.
95.
合成了不同类型聚醚聚氨酯/环氧树脂(PU/EP)互穿网络聚合物(IPN),通过改变PU中聚乙二醇分子量、3OH/2OH及NCO/OH比值等,研究IPN组份间分子混合程度,采用电镜、动态力学分析及应力应变等测试方法表征。结果表明:聚乙二醇分子量降低及3OH/2OH、NCO/OH比的提高,可使相容性提高,材料力学性能增强。 相似文献
96.
97.
98.
Carbon black (CB)-filled immisicible thermoplastic/thermosetting polymer blends consisting of polypropylene (PP) and Novolac resin were reported in this paper. The PP/Novolac/CB blends with varied compositions and different processing sequences were prepared by melt-mixing method. The CB distribution, conductive mechanism and the relationship between morphology and electrical properties of the PP/Novolac/CB blends were investigated. Scanning electron microscopy (SEM), optical microscopy and extraction experiment results showed that in PP/Novolac blends CB particles preferentially localized in the Novolac phase, indicating CB has a good affinity with Novolac resin. The incorporation of CB changed the spherical particles of the dispersed Novolac phase into elongated structure. With increasing Novolac content, the elongation deformation of Novolac phase became more obvious and eventually the blends developed into co-continuous structure, which form double percolation and decrease the percolation threshold. When CB was initially blended with PP and followed by the addition of Novolac resin, the partial migration of CB from PP to the Novolac phase was possibly occurred. The addition of Novolac to PP evidently increases the storage modulus G′, loss modulus G″ and complex viscosity η∗. The addition of CB to PP/Novolac blends further increase η∗, and it increases with increasing CB loading, which was related to the change of composite morphology. 相似文献
99.
Membrane extraction with sorbent interface, combined with a portable gas chromatograph system (MESI-Portable GC) for continuous on-line monitoring of biogenic volatile organic compounds (BVOCs) emissions (from leaves of Eucalytus dunnii in a greenhouse), is presented herein. A sampling chamber was designed to facilitate the extraction and identification of the BVOCs emitted by the Eucalytus dunnii leaves. Preliminary experiments, including; enrichment times, microtrap temperatures, stripping gas flow rates, and desorption temperatures were investigated to optimize experimental parameters. The main components of BVOCs released by the Eucalytus dunnii leaves were identified by comparing the retention times of peaks with those of authentic standard solutions. They were then confirmed with solid phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS). BVOC emission profiles of [small alpha]-pinene, eucalyptol, and [gamma]-terpinene emitted by intact and damaged Eucalytus dunnii leaves were obtained. The findings suggest that the MESI-Portable GC system is a simple and useful tool for field monitoring changes in plant emissions as a function of time. 相似文献
100.
Limei Dai Ying Ma Enbo Wang Ying Lu Xinxin Xu Xiuli Bai 《Transition Metal Chemistry》2006,31(3):340-346
Two new neutral Keggin-polyoxometalate derivatives: [{Co(2,2′-bipy)2(H2O)}2]–[PMoVI7MoV5O40(VIVO)2] (1) and [{Ni(phen)2(H2O)}2](H3O) [PMoVI10MoV2O40] · 4H2O (2) have been synthesized under hydrothermal conditions and characterized by i.r., t.g. analysis, x.p.s. spectra and single-crystal
X-ray diffraction. In the case of (1), the polyoxoanion cluster [PMo12O40]8− is capped by two vanadium atoms via four bridging oxo groups on two opposite {Mo4O4} pits of the Keggin polyoxoanion. Two {Co (2,2′-bipy)2(H2O)} fragments are supported on the two vanadium atoms through two terminal oxygen atoms from two vanadium atoms. In (2), two {Ni(phen)2(H2O)}2+ moieties are linked to the molybdophosphate cluster [PMo12O40] core to form a neutral bimetallic cluster. Furthermore, through the linkages of π – π stacking interactions and hydrogen bond contacts, extended three-dimensional supramolecular networks in the solid of (1) and (2) were formed. 相似文献