全文获取类型
收费全文 | 872篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
化学 | 627篇 |
晶体学 | 22篇 |
力学 | 16篇 |
数学 | 67篇 |
物理学 | 152篇 |
出版年
2019年 | 4篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 51篇 |
2012年 | 36篇 |
2011年 | 39篇 |
2010年 | 31篇 |
2009年 | 27篇 |
2008年 | 65篇 |
2007年 | 45篇 |
2006年 | 42篇 |
2005年 | 46篇 |
2004年 | 49篇 |
2003年 | 45篇 |
2002年 | 36篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1971年 | 3篇 |
1969年 | 4篇 |
1968年 | 7篇 |
1966年 | 6篇 |
1964年 | 4篇 |
1962年 | 3篇 |
1954年 | 3篇 |
排序方式: 共有884条查询结果,搜索用时 31 毫秒
131.
Visualization of Heterogeneous Oxygen Storage Behavior in Platinum‐Supported Cerium‐Zirconium Oxide Three‐Way Catalyst Particles by Hard X‐ray Spectro‐Ptychography 下载免费PDF全文
Makoto Hirose Dr. Nozomu Ishiguro Kei Shimomura Dr. Nicolas Burdet Dr. Hirosuke Matsui Prof. Dr. Mizuki Tada Prof. Dr. Yukio Takahashi 《Angewandte Chemie (International ed. in English)》2018,57(6):1474-1479
The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce2Zr2Ox (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce2Zr2Ox particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts. 相似文献
132.
We propose a new search algorithm to solve the equation for a fixed value of . By parametrizing min, this algorithm obtains and (if they exist) by solving a quadratic equation derived from divisors of . By using several efficient number-theoretic sieves, the new algorithm is much faster on average than previous straightforward algorithms. We performed a computer search for 51 values of below 1000 (except ) for which no solution has previously been found. We found eight new integer solutions for and in the range of .
133.
Structural inhomogeneities of μc-Si:H in the range 20≈500 A are observed for the first time by small angle X-ray scattering. Inhomogeneous distributions of bonded hydrogen in the amorphous tissue are suggested to be a possible origin of the SAXS yield. Such inhomogeneities can be reduced when the average grain size and volume fraction of microcrystallites are simultaneously increased. 相似文献
134.
This paper studies the geometric decay property of the joint queue-length distribution {p(n
1,n
2)} of a two-node Markovian queueing system in the steady state. For arbitrarily given positive integers c
1,c
2,d
1 and d
2, an upper bound
of the decay rate is derived in the sense
It is shown that the upper bound coincides with the exact decay rate in most systems for which the exact decay rate is known.
Moreover, as a function of c
1 and c
2,
takes one of eight types, and the types explain some curious properties reported in Fujimoto and Takahashi (J. Oper. Res.
Soc. Jpn. 39:525–540 [1996]).
相似文献
135.
The vibrational sum frequency generation (SFG) spectra of the air-liquid interface of H2SO4-H2O solutions over a wide range of concentrations are measured in the SO stretching region (1000-1300 cm(-1)). The analogy of the concentration dependence of Raman and SFG is indicative of a nearly identical behavior of the first acid dissociation at the air-liquid interface as in the bulk. 相似文献
136.
Jeon Y Sung J Kim D Seo C Cheong H Ouchi Y Ozawa R Hamaguchi HO 《The journal of physical chemistry. B》2008,112(3):923-928
Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration. 相似文献
137.
138.
Ito H Saito T Oshima N Kitamura N Ishizaka S Hinatsu Y Wakeshima M Kato M Tsuge K Sawamura M 《Journal of the American Chemical Society》2008,130(31):10044-10045
Reversible mechanochromic luminescence of [(C6F5Au)2(mu-1,4-diisocyanobenzene)] is reported. Grinding of the complex induced a photoluminescent color change, which was restored by exposure to a solvent. This cycle was repeated 20 times with no color degradation in the emissions. Their optical properties, X-ray crystallographic analysis, IR, and XRD measurements strongly suggested that the change in the molecular arrangement is responsible for this mechanochromic property. Intermolecular aurophilic bondings presumably play a key role in the altered emission. 相似文献
139.
Taki M Desaki M Ojida A Iyoshi S Hirayama T Hamachi I Yamamoto Y 《Journal of the American Chemical Society》2008,130(38):12564-12565
We described here a coumarin-based dual-excitation ratiometric probe for cadmium, CadMQ. This fluorescence sensor has high quantum yields of 0.59 and 0.70 in the metal-free and Cd2+-bound forms, respectively, and has a dissociation constant of 0.16 nM for Cd2+. CadMQ is cell permeable and locates within the acidic compartments of the cells. We further show that CadMQ is a useful tool to ratiometrically probe the change in the intracellular Cd2+ levels with the use of two excited wavelengths. 相似文献
140.
Lee JE Hitotsuyanagi Y Fukaya H Kondo K Takeya K 《Chemical & pharmaceutical bulletin》2008,56(5):730-733
Two new bicyclic hexapeptides, RA-XXIII and RA-XXIV, were isolated from the roots of Rubia cordifolia L. (Rubiaceae). Their structures were determined by the analysis of their 2D NMR spectra, chemical methods, and X-ray crystallography. The IC50 values of RA-XXIII and RA-XXIV against P-388 leukemia cells were 0.16 and 0.48 microg/ml, respectively. 相似文献