全文获取类型
收费全文 | 1241篇 |
免费 | 44篇 |
国内免费 | 3篇 |
专业分类
化学 | 880篇 |
晶体学 | 5篇 |
力学 | 53篇 |
数学 | 55篇 |
物理学 | 295篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 1篇 |
2021年 | 38篇 |
2020年 | 32篇 |
2019年 | 30篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 35篇 |
2015年 | 37篇 |
2014年 | 56篇 |
2013年 | 96篇 |
2012年 | 94篇 |
2011年 | 105篇 |
2010年 | 67篇 |
2009年 | 59篇 |
2008年 | 81篇 |
2007年 | 83篇 |
2006年 | 74篇 |
2005年 | 67篇 |
2004年 | 57篇 |
2003年 | 42篇 |
2002年 | 39篇 |
2001年 | 33篇 |
2000年 | 23篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1288条查询结果,搜索用时 15 毫秒
71.
Myeong Hyeon Park In Sook Kim Mi-Sook Dong Hye Hyun Yoo 《Analytical and bioanalytical chemistry》2014,406(14):3443-3449
Aromatase (CYP 19A1) is a key steroidogenic enzyme that catalyzes the conversion of androgen to estrogen. In this study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for aromatase inhibitor screening was developed and validated. The substrate androstenedione was incubated with human CYP 19A1 supersomes in the presence of NADPH for 30 min, and estrone formation was determined by LC-MS/MS analysis. Cortisone was used as internal standard. The incubation mixture was extracted using a liquid-liquid extraction method with ethyl acetate. Chromatographic separation was achieved using a C18 column (3.0?×?50 mm, 2.7 μm) with a mobile phase consisting of 0.1 % formic acid/acetonitrile adopting gradient elution at a flow rate of 0.4 mL/min. The mass spectrometer was operated in positive electrospray ionization mode. The precursor-product ion pairs used for multiple reaction monitoring were m/z 287→97 (androstenedione), m/z 271?→?159 (estrone), and m/z 361?→?163 (IS, cortisone). The developed method met the required criteria for the validation of bioanalytical methods. The validated method was successfully applied to evaluate aromatase inhibitory activity of plants extracts of Simaroubaceae. Figure
Determination of estrone formation by LC-MS/MS analysis for aromatase inhibitor screening 相似文献
72.
Yeon-Ah Lee Hye-In Ji Sang-Hoon Lee Seung-Jae Hong Hyung-In Yang Myung Chul Yoo Kyoung Soo Kim 《Experimental & molecular medicine》2014,46(1):e72
This study was performed to evaluate the contribution of adiponectin to the production of interleukin (IL)-6, IL-8, vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-1 and MMP-13 in human endothelial cells and osteoblasts in arthritic joints. Cultured human umbilical vascular endothelial cells (HUVECs) and osteoblasts were stimulated with adiponectin (1 or 10 μg ml−1) or IL-1β (0.1 ng ml−1) in the presence or absence of hypoxia for 24 h. The protein expression patterns were examined by analyzing culture supernatants using the enzyme-linked immunosorbent assay (ELISA). Adiponectin significantly stimulated the production of VEGF, MMP-1 and MMP-13 in osteoblasts but not in endothelial cells, whereas it significantly stimulated the production of IL-6 and IL-8 in both endothelial cells and osteoblasts. The increase in VEGF production induced by adiponectin was significantly greater than that induced by IL-1β. The production of IL-6 and IL-8 in adiponectin-stimulated endothelial cells was approximately 10-fold higher than that in IL-1β-stimulated endothelial cells; in osteoblasts, adiponectin-induced IL-6 and IL-8 secretion was approximately twofold higher than that induced by IL-1β. In addition, IL-8 production in endothelial cells was approximately sevenfold higher than in osteoblasts. However, IL-6 levels were similar between the two cell types, suggesting that adiponectin may be involved in the production of IL-8 in endothelial cells, which may have an important role in neutrophil recruitment to arthritic joints. Furthermore, the increases in protein expression induced by adiponectin were differentially regulated by hypoxia. In conclusion, adiponectin has a more important role than does IL-1β in the production of mediators that drive synovitis and joint destruction in endothelial cells and osteoblasts at physiological concentrations. 相似文献
73.
Cover Picture: Development of Double‐Perovskite Compounds as Cathode Materials for Low‐Temperature Solid Oxide Fuel Cells (Angew. Chem. Int. Ed. 48/2014) 下载免费PDF全文
74.
Frontispiece: In Vivo Residue‐Specific Dopa‐Incorporated Engineered Mussel Bioglue with Enhanced Adhesion and Water Resistance 下载免费PDF全文
75.
76.
H. Shin E. Yoon K.-S. Hong W. Lee Y.-H. Yoo 《Applied Physics A: Materials Science & Processing》2005,81(4):715-719
The shifts of emission energy from InAs quantum dots (QDs) in the GaAs matrix due to change in the QD stacking period have been numerically analyzed by investigating the strain modified shifts of band edges. Narrower stacking results in a blueshift of emission energy from direct band gap transition provided the QD spacing is wide enough to avoid electronic coupling. Through a comparison with existing experimental results in the literature, processing methods and variables that have benefits in achieving a blueshift have been inferred. A blueshift through decreased QD spacing has been proposed as a token of the integrity of a processed QD nanostructure . PACS 68.65.+g; 78.66.Fd 相似文献
77.
Y.M. Park Y.J. Park K.M. Kim J.I. Lee K.H. Yoo 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):647-653
We have investigated the optical properties of InAs self-assembled quantum dots (SAQDs) with the Si-doped GaAs barrier layer. Two types of samples are fabricated according to the position of the Si-doped GaAs layer. For type A samples the Si-doped GaAs layer is grown below the QDs, whereas for type B samples the Si-doped GaAs layer is grown above the QDs. For both types of samples the excited-state emissions caused by state filling are observed in photoluminescence (PL) spectra at high excitation power densities. The bandgap renormalization of QDs can be found from the shift of the PL peak energy. Particularly, for type A samples the Si atoms act as nucleation centers during the growth of InAs QDs on the Si-doped GaAs layer and affect the density and the size of the QDs. The Si-doped GaAs layer in type A samples has more effects on the properties of QDs, such as state filling and bandgap renormalization than those of type B samples. 相似文献
78.
The energy level alignment between C60 and Al has been investigated by using ultraviolet photoelectron spectroscopy. To obtain the interfacial electronic structure between C60 and Al, C60 was deposited on a clean Al substrate in a stepwise manner. The valence-band spectra were measured immediately after each step of C60 deposition without breaking the vacuum. The measured onset of the highest occupied molecular orbital energy level was located at 1.59 eV from the Fermi level of Al. The vacuum level was shifted 0.68 eV toward lower binding energy with additional C60 layers. The observed vacuum level shift means that the interface dipole exists at the interface between C60 and Al. The barrier height of electron injection from Al to C60 is 0.11 eV, which is smaller value than that of hole injection. 相似文献
79.
Yong-Goo Yoo Seong-Cho Yu P.D. Kim B.A. Belyaev A.M. Mahlaev D.L. Khalyapin 《Journal of magnetism and magnetic materials》2006
The exchange coupling strength of NiFe/Cu/IrMn trilayer films was examined with both a new magneto optical Kerr effect (MOKE) method developed for the exchange coupling field determination and ferromagnetic resonance (FMR) measurements. We found that the value for exchange coupling field obtained by the MOKE technique coincided with FMR result with high accuracy. Other peculiarities of FMR measurements due to interlayer exchange coupling such as angular dependence of resonance field on Cu spacer thickness are also shown in the article. 相似文献
80.
Yong-Goo Yoo Seong-Gi Min Ho-Jun Ryu Nam-Seok Park Seong-Cho Yu 《Journal of magnetism and magnetic materials》2006
Exchange biased IrMn/NiFe/IrMn thin films were studied as a function of NiFe thickness. In plane angular dependence of a resonance field distribution which is measured by FMR was analyzed as a combined effect of an unidirectional anisotropy and an uniaxial anisotropy. The unidirectional anisotropic field and the uniaxial anisotropic field were linearly varied with NiFe thickness while the films with a thicker NiFe layer do not follow the linear variation. Resonance field and linewidth variations were also analysed with NiFe thickness. 相似文献