全文获取类型
收费全文 | 3408篇 |
免费 | 415篇 |
国内免费 | 441篇 |
专业分类
化学 | 2848篇 |
晶体学 | 71篇 |
力学 | 114篇 |
综合类 | 30篇 |
数学 | 317篇 |
物理学 | 884篇 |
出版年
2024年 | 3篇 |
2023年 | 56篇 |
2022年 | 149篇 |
2021年 | 156篇 |
2020年 | 149篇 |
2019年 | 168篇 |
2018年 | 139篇 |
2017年 | 141篇 |
2016年 | 207篇 |
2015年 | 205篇 |
2014年 | 226篇 |
2013年 | 294篇 |
2012年 | 337篇 |
2011年 | 362篇 |
2010年 | 245篇 |
2009年 | 267篇 |
2008年 | 255篇 |
2007年 | 213篇 |
2006年 | 139篇 |
2005年 | 138篇 |
2004年 | 110篇 |
2003年 | 71篇 |
2002年 | 56篇 |
2001年 | 25篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 10篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1935年 | 1篇 |
排序方式: 共有4264条查询结果,搜索用时 724 毫秒
951.
Acta Mathematicae Applicatae Sinica, English Series - Supersaturated designs are common choice for screening experiments. This paper studies the properties of supersaturated designs. We give new... 相似文献
952.
A simple and selective chemosensor, A, was developed for recognizing Cu2+. The emission spectra of receptor A showed a fluorescence quenching response upon addition of Cu2+ with a low detection limit of 4.51 nM, significantly less than the WHO recommended guideline for drinking water. In addition, the formed A?Cu2+ complex was examined for secondary sensing of anions. The A?Cu2+ complex showed selectivity for CN– via a recovering emission profile of A. 相似文献
953.
Omar Kammoun Nouha Loulou Walid Rekik Houcine Na?li Tahar Mhiri Thierry Bataille 《Journal of chemical crystallography》2012,42(2):103-110
Abstract
The new hybrid material, cobalt selenate templated by 1,4-diazabicyclo[2.2.2]octane (abbreviated dabco), has been synthesised by the slow evaporation method at room temperature. Its crystal structure was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P21/c) with the following unit-cell parameters: a = 12.9169(2) ?, b = 11.9101(2) ?, c = 12.4951(2) ?, β = 108.484(1)°, V = 1823.10(5) ?3 and Z = 4. The supramolecular structure of (C6H14N2)[Co(H2O)6](SeO4)2 consists of isolated [Co(H2O)]2+ and (C6H14N2)2+ cations and (SeO4)2− anions linked together by three dimensional hydrogen-bond network. The infrared spectroscopy confirmed the presence of these different entities. The thermal behaviour of the precursor, studied by thermodiffractometry and thermogravimetric analyses, indicates that its decomposition proceeds through three stages giving rise to the cobalt oxide. 相似文献954.
Hai-Jiang Chen Yan-Juan Jiang Yong-Qiang Zhang Qi-Wei Jing Na Liu Yan Wang Wan-Nian Zhang Chun-Quan Sheng 《中国化学快报》2017,28(4):913-918
In order to discover new generation of triazole antifungal agents,a series of novel antifungal triazoles were designed and synthesized by structural simplification of our previously identified triazole-piperdine-heterocycle lead compounds.Several target compounds showed good antifungal activity with a broad spectrum.In particular,compound 7l was highly active against Candida albicans and Candida glabrata.Moreover,compound 7l showed potent in vivo antifungal efficacy in the Caenorhabditis elegans-C.albicans infection model. 相似文献
955.
Cyclic oxalates were efficiently prepared by the reaction of diols with ethyl oxalyl chloride in the presence of triethylamine. They were stable under acidic conditions but cleaved to diols under basic conditions. 相似文献
956.
Le Thi Kim Van Tran Manh Hung Soo Hyun Kim Jin Cheol Kim MinKyun Na Hyun Ju Jung Seung Jun Kwack Kee Tae Kweon Jae Sue Choi Hyeong Kyu Lee KiHwan Bae Byung‐Sun Min 《Helvetica chimica acta》2010,93(9):1803-1807
A new stereoisomer of a tetrahydrofuranoid lignan, acerifuranoid A ( 1 ), and two new oleanane‐type triterpenoids, aceriphyllic acids J and K ( 2 and 3 ), were isolated from the roots of Aceriphyllum rossii. Their structures were elucidated on the basis of spectroscopic analyses and chemical evidence. These isolated compounds exhibited weak cytotoxic activity against various cancer cell lines with IC50>150 μM . 相似文献
957.
958.
959.
Haining Na Xiwang Liu Hua Sun Yunhui Zhao Ci Zhao Xiaoyan Yuan 《Journal of Polymer Science.Polymer Physics》2010,48(3):372-380
Dispersed solutions of poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) in the mixed solvent of N,N‐dimethylformamide (DMF)/tetrahydrofuran (THF) were used to electrospin in order to discuss the relationship between the properties of the polymer dispersions and the morphology of the obtained ultrafine fibers. With the changes of the mass ratio of PVDF/PC, the relative molecular mass of PVDF, and the volume ratio of DMF/THF, the morphology and the microstructure of the prepared PVDF/PC ultrafine fibers altered in accord with the viscosity, surface tension, and conductivity of the PVDF/PC dispersions. When the PVDF/PC mass ratio varied from 9/1 to 5/5, the ability of the polymer chain entanglement in PVDF/PC dispersion decreased as to the lower relative molecular mass of PC and higher chain rigidity, which lead to the formation of the beaded fibers together with the distinct core/shell structure. Similar phenomenon was also found when the lower molecular mass of PVDF was used instead of a higher one. Though the change of DMF/THF volume ratio did not specifically contribute to the properties of PVDF/PC dispersions, the accelerated evaporation and solubility of the mixed solvent by the THF amount increasing was feasible to generate the uniform fibrous morphology and the distinct core/shell structure. © 2009 Wiley Periodicals, Inc.J Polym Sci Part B: Polym Phys 48: 372–380, 2010 相似文献
960.