全文获取类型
收费全文 | 1655篇 |
免费 | 53篇 |
国内免费 | 10篇 |
专业分类
化学 | 1302篇 |
晶体学 | 21篇 |
力学 | 12篇 |
数学 | 82篇 |
物理学 | 301篇 |
出版年
2021年 | 10篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 25篇 |
2014年 | 36篇 |
2013年 | 77篇 |
2012年 | 83篇 |
2011年 | 96篇 |
2010年 | 36篇 |
2009年 | 52篇 |
2008年 | 113篇 |
2007年 | 102篇 |
2006年 | 88篇 |
2005年 | 103篇 |
2004年 | 84篇 |
2003年 | 88篇 |
2002年 | 79篇 |
2001年 | 47篇 |
2000年 | 26篇 |
1999年 | 20篇 |
1998年 | 21篇 |
1997年 | 13篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 21篇 |
1979年 | 28篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1975年 | 16篇 |
1974年 | 7篇 |
1973年 | 13篇 |
1971年 | 8篇 |
排序方式: 共有1718条查询结果,搜索用时 62 毫秒
1.
Watanabe Sou Senzaki Tatsuya Shibata Atsuhiro Nomura Kazunori Takeuchi Masayuki Nakatani Kiyoharu Matsuura Haruaki Horiuchi Yusuke Arai Tsuyoshi 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1273-1277
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate... 相似文献
2.
Behavior of fine crystalline particles of W5Si3 on a beta-Si3N4 substrate at high temperatures was observed by an in situ heating experiment in a transmission electron microscope. Some of the fine particles of W5Si3 moved in a to-and-fro manner. 相似文献
3.
Akira Yanagisawa Prof. Dr. Takahiro Suzuki Takanori Koide Shogo Okitsu Takayoshi Arai Prof. Dr. 《化学:亚洲杂志》2008,3(10):1793-1800
A Barbier‐type regioselective propargylation of aldehydes and ketones with (3‐bromobut‐1‐ynyl)trimethylsilane has been achieved using reactive barium as a low‐valent metal in THF. Especially in the case of ketones, the corresponding homopropargylic alcohols form almost exclusively. In the reaction of α,β‐unsaturated carbonyl compounds, only 1,2‐adducts have been observed. This method is also applicable to propargylation of imines, and the corresponding homopropargylic amines are obtained regiospecifically in good yields with diastereomeric ratios of up to 87:13. 相似文献
4.
Oscillation is found in many biological systems, and among them the enzymatic oscillatory reaction has been well studied using an enzyme solution. We show in this study for the first time that oscillation occurs when catalase is immobilized to controlled pore glass (CPG). The oscillatory wave mode changes with the distance among the CPG, electrode, or dialysis membrane. The lower substrate concentration results in oscillation with a longer period. This tendency agrees with a previous study using an enzyme solution. Furthermore, we show that the oscillation occurs when no dialysis membrane is used. These results show the wider applicability of the system to analysis or novel device fabrication. 相似文献
5.
Ryohei Tsuda Sayaka Kaino Hisashi Kokubo Shin-Ichiro Imabayashi Masayoshi Watanabe 《Colloids and surfaces. B, Biointerfaces》2007,56(1-2):255-Optics
Redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide) (PT-EGEn-b-EOm) are reversibly changed by core-shell micelle formation. In the temperature range higher than the critical micellization temperature (cmt), the anodic potential of PT group positively shifts and concomitantly its anodic current decrease, or levels off compared to those of the reference polymer PT-EOm without the thermo-responsive EGEn segment. The former alteration is caused by incorporation of hydrophobic PT groups into a core of the micelle and the latter by the decrease in the diffusion coefficient of PT groups due to formation of the core-shell micelles. The cmt value and the temperature-dependent alteration in the redox properties strongly depend on the polymer structure, especially the length of thermo-responsive EGEn segment. The electrochemically determined hydrodynamic radii of the polymer aggregates seem to be overestimated, compared to the values reported for the aggregates of other thermo-responsive polymers with similar molecular weights, implying the presence of electrochemically inactive PT groups in the copolymers having longer thermo-responsive segments. 相似文献
6.
7.
Md. Nur Alam Per B. Zetterlund Masayoshi Okubo 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4995-5004
Bimolecular termination in nitroxide‐mediated radical polymerization in miniemulsion has been investigated through the heating of a polystyrene–2,2,6,6‐tetramethylpiperidinyl‐1‐oxy macroinitiator and its 4‐hydroxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy analogue in an aqueous toluene dispersion with sodium dodecyl benzenesulfonate as a surfactant at 125 °C. The level of bimolecular termination by combination, evaluated from the high‐molecular‐weight shoulder, was higher in miniemulsion than in solution and increased with decreasing particle size. Quantitative analysis revealed that these results cannot be rationalized solely by nitroxide partitioning to the aqueous phase. The results are explained by an interface effect, by which nitroxide is adsorbed or located at the aqueous–organic interface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4995–5004, 2007 相似文献
8.
9.
Masayoshi Senba 《Hyperfine Interactions》1994,87(1):959-964
A study has been made of highly nitrogenated pure iron and iron-aluminum alloy powder containing 2 wt.% Al (Fe-2Al) using Mössbauer spectroscopy and X-ray diffraction. The samples were prepared by high-temperature, high-pressure diffusion of nitrogen. They were prepared in a hot-isostatic-pressure (HIP) furnace at 1000 °C at nitrogen pressures up to 200 MPa. The alloy powders contained up to 8 at.% nitrogen as determined by vacuum fusion analysis. XRD analysis indicates that for the pure iron powders, the lattice spacing remained independent of nitrogen concentration, but that for the Fe-2Al powders, it decreased with increasing nitrogen concentration. Mössbauer analysis showed that for the pure iron powders, most of the nitrogen was associated with the formation of the iron nitride Fe4N. For the alloy powders containing less than 5 at.% nitrogen, all of the nitrogen was contained interstitially. The presence of nitrogen completely eliminated the conduction-electron spin-density oscillations observed in many ferromagnetic alloys. 相似文献
10.
O-Glycosylations using thiomethyl glycosides as donors were compared under both frozen and unfrozen conditions. In the presence of MeOTf as a promoter, enormous rate acceleration was observed when the glycosylation was conducted in p-xylene below its freezing point. 相似文献