全文获取类型
收费全文 | 3765篇 |
免费 | 70篇 |
国内免费 | 11篇 |
专业分类
化学 | 2606篇 |
晶体学 | 45篇 |
力学 | 65篇 |
数学 | 171篇 |
物理学 | 959篇 |
出版年
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 48篇 |
2019年 | 49篇 |
2018年 | 41篇 |
2017年 | 25篇 |
2016年 | 50篇 |
2015年 | 56篇 |
2014年 | 72篇 |
2013年 | 157篇 |
2012年 | 146篇 |
2011年 | 188篇 |
2010年 | 129篇 |
2009年 | 123篇 |
2008年 | 193篇 |
2007年 | 216篇 |
2006年 | 201篇 |
2005年 | 149篇 |
2004年 | 127篇 |
2003年 | 142篇 |
2002年 | 138篇 |
2001年 | 113篇 |
2000年 | 134篇 |
1999年 | 79篇 |
1998年 | 58篇 |
1997年 | 53篇 |
1996年 | 43篇 |
1995年 | 52篇 |
1994年 | 43篇 |
1993年 | 58篇 |
1992年 | 50篇 |
1991年 | 49篇 |
1990年 | 38篇 |
1989年 | 51篇 |
1988年 | 49篇 |
1987年 | 43篇 |
1986年 | 36篇 |
1985年 | 54篇 |
1984年 | 55篇 |
1983年 | 50篇 |
1982年 | 49篇 |
1981年 | 32篇 |
1980年 | 33篇 |
1979年 | 48篇 |
1978年 | 43篇 |
1977年 | 47篇 |
1976年 | 16篇 |
1975年 | 26篇 |
1974年 | 30篇 |
1967年 | 16篇 |
排序方式: 共有3846条查询结果,搜索用时 15 毫秒
951.
Takumi Inaba Takahiro Morimoto Toshiya Okazaki 《Surface and interface analysis : SIA》2022,54(5):501-509
A simulation method for correlating the resistivity and resistance of sparse carbon nanotube (CNT) networks via atomic force microscopy images was proposed. For the demonstration, resistance values simulated by this method were compared with values obtained by directory measuring the resistance of sparse CNT networks. Results were also compared with those obtained by a thin-film approximation in which CNT networks are approximated as thin rectangles. Simulated resistance values were closer to the experimental values of the same samples than those estimated on the basis of the thin-film approximation. The use of atomic force microscopy (AFM) images enabled the implementation of inhomogeneity to numerical models, as well as one-to-one comparison between real samples and numerical models. 相似文献
952.
Takanobu Sanji Asahi Motoshige Hideaki Komiyama Junko Kakinuma Rie Ushikubo Satoru Watanabe Tomokazu Iyoda 《Chemical science》2015,6(1):492-496
A transition-metal-free controlled polymerization for the attainment of poly(p-aryleneethynylene)s is developed. The polymerization of 1-pentafluorophenyl-4-[(trimethylsilyl)ethynyl]benzene with a catalytic amount of fluoride anions proceeds in a chain-growth-like manner to afford polymers with controlled molecular weights and low polydispersity indexes. The mechanism involves a pentacoordinated fluorosilicate as a key intermediate. The anionic “living” nature of this process is applied to block copolymerization and also surface-terminated polymerization. 相似文献
953.
Kenichi Murata Kazuki Kajiya Megumi Nukaga Yosuke Suga Toshiyuki Watanabe Nobuhumi Nakamura Hiroyuki Ohno 《Electroanalysis》2010,22(2):185-190
A simple method for constructing gold nanoparticle‐modified electrodes with three‐dimensional nanostructures is demonstrated. The electrodes were prepared by casting citrate‐reduced AuNPs onto polycrystalline gold electrodes. The resultant electrodes had a large surface area‐to‐volume ratio, adequate for high protein loading and conferring high stability. The gold nanoparticle electrodes were covered with a self‐assembled monolayer of 11‐mercaptoundecanoic acid for electrostatic immobilization of cytochrome c (cyt c). At the electrode, direct, reversible electron transfer from cyt c was observed with remarkable stability. Moreover, an extremely high surface coverage of electrochemically active cyt c, 167 fully packed monolayers, was obtained through use of the electrode. 相似文献
954.
D. Q. Thuyet K. Yamazaki T. K. Phong H. Watanabe D. T. T. Nhung K. Takagi 《Journal of Analytical Chemistry》2010,65(8):843-847
A method for the determination of imidacloprid in paddy water and soil was developed using liquid chromatography electrospray
ionization-tandem mass spectrometry (LC/ESI-MS/MS). Separation of imidacloprid was carried out on a Shimadzu C18 column (150 mm × 4.6 mm, 4.6 μm) with an acetonitrile-water
(50: 50, v/v) mobile phase containing 0.1% of acetic acid. The flow rate was 0.3 mL/min in isocratic mode. The product ion
at 209 m/z was selected for quantification in multiple-reaction monitoring scan mode. Imidacloprid residues in soil were extracted by
a solid-liquid extraction method with acetonitrile. Water samples were filtered and directly injected for analysis without
extraction. Detection limits of 0.5 μg/kg and 0.3 μg/L were achieved for soil and water samples, respectively. The method
had recoveries of 90 ± 2% (n = 4) for soil samples and 100 ± 2% (n = 4) for water samples. A linear relationship was observed throughout the investigated range of concentrations (1–200 μg/L),
with the correlation coefficients ranging from 0.999 to 1.000. 相似文献
955.
Synthesis, characterization, and catalytic reactivity of a highly basic macrotricyclic aminopyridine
Uchida N Taketoshi A Kuwabara J Yamamoto T Inoue Y Watanabe Y Kanbara T 《Organic letters》2010,12(22):5242-5245
The synthesis methods, physicochemical and structural characteristics, and catalytic reactivity of new macrocyclic proton chelators, N,N',N'-tris(p-tolyl)azacalix[3](2,6)(4-pyrrolidinopyridine) and N,N',N'-tris(p-tolyl)azacalix[3](2,6)(4-piperidinopyridine), are studied. The introduction of pyrrolidino and piperidino groups into the pyridine unit enables the enhancement of the synergistic proton affinity of the cavity of the macrotricycle giving a high basicity (pK(BH+) = 28.1 and 27.1 in CD(3)CN), resulting in a catalytic activity for the Michael addition of nitromethane with α,β-unsaturated carbonyl compounds. 相似文献
956.
Shigeru Kiryu Yusuke Inoue Kohki Yoshikawa Morio Shimada Makoto Watanabe Kuni Ohtomo 《Magnetic resonance imaging》2010
In magnetic resonance (MR) imaging of small animals, the gastrointestinal contents may give rise to intense signals on T1-weighted images. The aim of this study was to determine the optimal dietary preparation to reduce gastrointestinal signals in mice and to evaluate the usefulness of this approach. Images of the mouse trunk were obtained using a T1-weighted, three-dimensional fast low-angle shot sequence under various dietary conditions and were compared with respect to the gastrointestinal signals and image quality. The dietary preparation studied included giving alternative diets for 24 h, intestinal cleansing, and 6-h fasting. Mice with and without dietary preparation underwent MR lymphography using gadofluorine 8, and the visualization of abdominal lymph nodes was compared. In the absence of dietary preparation, hyperintense areas were conspicuous in the gastrointestinal system, whereas on the images taken from mice fed potato or sweet potato for 24 h before imaging, gastrointestinal hyperintensity was less prominent. This preparation also reduced artifactual signals and resulted in higher-quality images of the kidneys. Intestinal cleansing, which consisted of 24-h fasting and laxative intake, did not reduce the gastrointestinal signals and caused signal changes that were indicative of fatty liver development. Some of the abdominal lymph nodes of the mice that did not receive dietary preparation were visualized on MR lymphography source images but not on maximum intensity projection (MIP) images. In contrast, on the MIP images of mice fed potato, all the lymph nodes delineated on the source images were successfully visualized. In conclusion, feeding mice potato or sweet potato for 24 h before MR imaging reduces the gastrointestinal signals and image degradation due to artifacts. Appropriate dietary preparations facilitate the display of target structures on MIP images and are expected to enhance the capabilities of small animal MR imaging. 相似文献
957.
K. Kikunaga T. Yamamoto Y. Tanaka N. Kikuchi K. Tokiwa T. Watanabe N. Terada 《Physica C: Superconductivity and its Applications》2010,470(21):1916-1919
(Cu, C)–Ba–O thin films have been deposited at low growth temperature of 450–570 °C by pulsed laser deposition method. A control of CO2 gas pressure and the growth temperature, usage of BaCuyOx pellet target resulted in an expansion of twice c-axis length of BaCuO2 structure (2c phase) and a significant rise of conductivity. Measurements of in-situ XPS suggest that the 2c phase should be (Cu, C)Ba2CuOx [(Cu, C)-1201]. The maximum temperature of onset of the superconducting transition and zero resistance state obtained so far were 60 and 47 K, respectively. 相似文献
958.
959.
960.
S. Yamashita T. Kasai T. Fujii T. Watanabe A. Matsuda 《Physica C: Superconductivity and its Applications》2010
We realized highly underdoped Bi-2212 crystals by using a Bi substitution into a Sr site (x), together with the excess oxygen (δ) control. The samples with x = 0–0.3 were grown by a traveling solvent floating zone method. For each x, δ was varied using the precision annealing method [1]. Under several assumptions, the effective Bi valence was evaluated to be +2.2, which is much lower than the formal valence +3. This indicates that the Bi substitution accompanies additional uptake in excess oxygen. The x dependent δ-doping level p relation and the observed shrink in the c-axis length are consistent with this assumption. Based on the decomposition phase diagram obtained in this study, Tc of 22 K was realized by careful annealing treatments. The samples showed a superconducting volume fraction of over 50%. 相似文献