全文获取类型
收费全文 | 420篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学 | 341篇 |
晶体学 | 8篇 |
力学 | 5篇 |
数学 | 23篇 |
物理学 | 67篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 14篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 11篇 |
2009年 | 22篇 |
2008年 | 27篇 |
2007年 | 25篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1976年 | 4篇 |
1972年 | 2篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
51.
52.
Makito Yokoe Keigo Aoi Masahiko Okada 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2312-2321
Novel copolycarbonates containing 1,4:3,6‐dianhydro‐D ‐glucitol or 1,4:3,6‐dianhydro‐D ‐mannitol units, with various methylene chain lengths, were synthesized by bulk and solution polycondensations, of several combinations of carbonate‐modified sugar derivatives and aliphatic diols. Bulk polycondensations of 1,4:3,6‐dianhydro‐2,5‐bis‐O‐(phenoxycarbonyl)‐D ‐glucitol or 1,4:3,6‐dianhydro‐2,5‐bis‐O‐(phenoxycarbonyl)‐D ‐mannitol with four α,ω‐alkanediols having methylene chain lengths of 4, 6, 8, and 10, respectively, at 180 °C afforded the corresponding copolycarbonates with number‐average molecular weight (Mn) values up to 19.2 × 103. 13C NMR analysis disclosed that these polymers had scrambled structures in which the sugar carbonate and aliphatic carbonate moieties were nearly randomly distributed along a polymer chain. However, solution polycondensations between 1,4:3,6‐dianhydro‐2,5‐bis‐O‐(p‐nitrophenoxycarbonyl)‐D ‐glucitol or 1,4:3,6‐dianhydro‐2,5‐bis‐O‐(p‐nitrophenoxycarbonyl)‐D ‐mannitol, and the α,ω‐alkanediols in sulfolane or dimethyl sulfoxide at 60 °C gave well‐defined copolycarbonates having regular structures consisting of alternating sugar carbonate and aliphatic carbonate moieties with Mn values up to 33.8 × 103. Differential scanning calorimetry demonstrated that all the copolycarbonates were amorphous with glass‐transition temperatures ranging from 1 to 65 °C, which decreased with increasing lengths of the methylene chain of the aliphatic diols. Additionally, all the copolycarbonates were stable up to 310–330 °C as estimated by thermogravimetric analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2312–2321, 2003 相似文献
53.
Kouichi Tsuji Tetsuya Emoto Yosuke Nishida Eiichiro Tamaki Yoshikuni Kikutani Akihide Hibara Takehiko Kitamori 《Analytical sciences》2005,21(7):799-803
Grazing-exit x-ray fluorescence (GE-XRF) and micro x-ray fluorescence (micro-XRF) methods were applied to chemical microchips as a detection method. Since an energy-dispersive x-ray detector was used, the simultaneous detection of multiple elements was possible. An analyzing region was especially designed on the microchip so that a sample solution could be dried and concentrated in a suitable area corresponding to the size of the primary x-ray beam. Finally, it was confirmed that both analytical methods could be combined well for use with a microchip. In GE-XRF, the background intensity in the XRF spectrum was reduced at grazing-exit angles. In addition, a good relationship between the x-ray fluorescence intensities and the concentrations of standard solutions that were introduced into the microchip was obtained. This indicates that the GE-XRF method is feasible for trace elemental analysis in chemical microchip systems. In micro-XRF, an attempt was made to concentrate and dry the analyte within a small analyzing region. The preliminary results indicated that the micro-XRF method could be applied for the analysis of microchips. 相似文献
54.
Thermoelectric powers of Fe, Ni and Co dissolved in liquid Sn are measured and discussed in relation to resistivity and susceptibility by reference to the concept of virtual bound state. 相似文献
55.
56.
57.
The phase diagram and the heat of transition of AgI-AgBr system have been determined by using the differential scanning calorimetry (DSC) with the help of X-ray diffraction patterns. It has been verified that the miscibility gap between β-AgI-type solid solution and AgBr-type one depends on the thermal history of the sample. From the thermodynamic point of view, it is likely that the variation of transition temperature with composition suggests the change of correlation among silver ions in superionic conducting phase. 相似文献
58.
The resistivity isotherm of liquid IVb(Sn,Pb)-Te alloys has a remarkable maximum and temperature coefficient of resistivity has large negative value around the equiatomic composition, suggesting that a kind of compound formation exists at this composition. The excess resistivities are interpreted in terms of resonance scattering by the compound of MTe(M=Sn, Pb) with a finite life time. 相似文献
59.
60.
Hisayuki Matsui Masayoshi Tamaki Shoichi Nasu Toshimasa Kurasawa 《Journal of Physics and Chemistry of Solids》1980,41(4):351-355
Electrical resistivities of arc-melted uranium carbides, UC, UC2, U2C3 and UC + UC2, were measured over the temperature range between 4 and 1900 K. The monocarbide, dicarbide and the mixture of carbides showed metallic character in their resistivity dependence on temperature above 30 K, while below this the resistivities were constant. U2C3 showed a knee in the resistivity curve at 54.0 K corresponding to a magnetic transition. Above 1100 K, the resistivity of U2C3 did not vary with temperature. The resistivity of the mixture (UC + UC2 with U2C3 precipitates) showed an arrest between 800 and 950 K. 相似文献