全文获取类型
收费全文 | 3533篇 |
免费 | 190篇 |
国内免费 | 19篇 |
专业分类
化学 | 2660篇 |
晶体学 | 36篇 |
力学 | 51篇 |
数学 | 274篇 |
物理学 | 721篇 |
出版年
2023年 | 14篇 |
2022年 | 68篇 |
2021年 | 82篇 |
2020年 | 66篇 |
2019年 | 73篇 |
2018年 | 50篇 |
2017年 | 49篇 |
2016年 | 143篇 |
2015年 | 107篇 |
2014年 | 155篇 |
2013年 | 224篇 |
2012年 | 286篇 |
2011年 | 304篇 |
2010年 | 180篇 |
2009年 | 167篇 |
2008年 | 224篇 |
2007年 | 219篇 |
2006年 | 180篇 |
2005年 | 168篇 |
2004年 | 187篇 |
2003年 | 126篇 |
2002年 | 142篇 |
2001年 | 62篇 |
2000年 | 81篇 |
1999年 | 40篇 |
1998年 | 23篇 |
1997年 | 17篇 |
1996年 | 28篇 |
1995年 | 27篇 |
1994年 | 18篇 |
1993年 | 21篇 |
1992年 | 38篇 |
1991年 | 21篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 11篇 |
1973年 | 4篇 |
排序方式: 共有3742条查询结果,搜索用时 15 毫秒
91.
Selective Growth and Structural Analysis of Regular MnO Nanooctapods Bearing Multiple High‐Index Surface Facets 下载免费PDF全文
Although numerous morphologies of MnO nanostructures have been reported, an exact structural analysis and mechanistic study has been lacking. In the present study, the formation of regular MnO octapods was demonstrated in a simple procedure, comprising the thermal decomposition of manganese oleate. Because of their structural uniformity, an ideal three‐dimensional model was successfully constructed. The eight arms protruded from the cubic center with tip angles of 38° and surface facets of {311} and {533} with rounded edges. The concentrations of oleate and chloride ions were the determining factors for the octapod formation. Selective coordination of the oleate ions to the {100} faces led to edge growth along the <111> direction, which was then limited by the chloride ions bound to the high‐index surface facets. These structural and mechanistic analyses should be helpful for understanding the complex nanostructures and for tuning their structure‐related properties. 相似文献
92.
Chang-Ho Kang Sang-Hyun Han YuJin Shin Soo Ji Oh Jae-Seong So 《Applied biochemistry and biotechnology》2014,172(6):2907-2915
Contamination by Cd is a significant environmental problem. Therefore, we examined Cd removal from an environmental perspective. Ureolysis-driven calcium carbonate precipitation has been proposed for use in geotechnical engineering for soil remediation applications. In this study, 55 calcite-forming bacterial strains were newly isolated from various environments. Biomineralization of Cd by calcite-forming bacteria was investigated in laboratory-scale experiments. A simple method was developed to determine the effectiveness of microbially induced calcite precipitation (MICP). Using this method, we determined the effectiveness of biomineralization for retarding the flow of crystal violet through a 25-mL column. When the selected bacteria were analyzed using an inductively coupled plasma optical emission spectrometer, high removal rates (99.95 %) of Cd were observed following incubation for 48 h. Samples of solids that formed in the reaction vessels were examined using a scanning electron microscope. The CdCO3 compounds primarily showed a spherical shape. The results of this study demonstrate that MICP-based sequestration of soluble heavy metals via coprecipitation with calcite may be useful for toxic heavy metal bioremediation. 相似文献
93.
As stimulated Brillouin scattering (SBS) materials, solids have many advantages such as compactness, innoxiousness, and ease of handling. The SBS threshold and reflectivity of K8 glass, a solid material, are investigated. A SBS phase control experiment using K8 glass to achieve coherent beam combination is performed with a self-phase-control technique below the optical damage threshold. The experimental results show that the short-term phase has been stabilized well with λ/33.8 fluctuation during 256 shots (25.6 s), and that the long-term phase change with non-convective K8 glass is much slower than that with convective HT-70 liquid. 相似文献
94.
95.
96.
Elin Julianti Hana Oh Hyi-Seung Lee Dong-Chan Oh Ki-Bong Oh Jongheon Shin 《Tetrahedron letters》2012,53(23):2885-2886
Acremolin (1), a novel modified base, was isolated from the culture broth of the marine fungus Acremonium strictum. Based on combined spectroscopic analyses, the structure of this compound was that of a methyl guanine base containing an isoprene unit. In addition, the presence of a 1H-azirine moiety is unprecedented among natural products. This compound exhibited weak cytotoxicity against an A549 cell line. 相似文献
97.
98.
99.
Fujiko Iwasaki Seui Kakuma Satoshi Yoshida Shin Murata Masanori Yasui 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):515-516
Abstract The deformation electron-density distributions of 6a-thia-1,3,4,6-tetraazapentalene derivatives (I, II) and bis(phenylthio)dibenzothiophene (III) were investigated by the X-ray diffraction method. For I and II, a structure around the hypervalent S-N bonds is a trigonal bipyramid with equatorial sp2 hybrid of S-C bond and lone-pair electrons and apical polarized S-N bonds. In 111 lone-pair electron densities are observed perpendicular to the thiophene ring and the C-S-C sulfide planes. 相似文献
100.
Abstract A new Monte Carlo sampling scheme, namely High Directional Monte Carlo procedure, is used to obtain the global energy minimum conformations of polypeptides such as enkephalin and melittin. The resultant structures of enkephalin and melittin agree well with previous results of theoretical and experimental studies. Particularly, it is shown that some important parts in the conformation, such as the hinge region that principally determines the tertiary structure of proteins, are correctly described by the new method. The resultant structures are compared with those of other works and their stereoscopic views are shown. 相似文献