全文获取类型
收费全文 | 800篇 |
免费 | 42篇 |
国内免费 | 4篇 |
专业分类
化学 | 678篇 |
晶体学 | 6篇 |
力学 | 12篇 |
数学 | 21篇 |
物理学 | 129篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 28篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 49篇 |
2012年 | 71篇 |
2011年 | 71篇 |
2010年 | 27篇 |
2009年 | 52篇 |
2008年 | 50篇 |
2007年 | 54篇 |
2006年 | 45篇 |
2005年 | 65篇 |
2004年 | 49篇 |
2003年 | 34篇 |
2002年 | 35篇 |
2001年 | 5篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有846条查询结果,搜索用时 15 毫秒
91.
Yamaoka Y Taniguchi Y Yasuzuka S Yamamura Y Saito K 《The Journal of chemical physics》2011,135(4):044705
Quasi-binary (QB) picture of thermotropics, which regards a neat thermotropic liquid crystal as a binary system consisting of (semi)rigid core and molten alkyl chain, was assessed experimentally for the most famous (and representative) thermotropic mesogenic series nCB. By adding n-heptane as solvent, the smectic A phase was induced in 7CB-n-heptane system. Small angle x-ray diffraction showed that the QB picture holds not only in the phase behavior but also in the structure. It is suggested that the melting of 8CB and 9CB to isotropic liquid via smectic and nematic liquid crystals can be understood as a thermotropic-lyotropic crossover. 相似文献
92.
Miyauchi M Li Y Yanai S Yotsugi K 《Chemical communications (Cambridge, England)》2011,47(30):8596-8598
A tungsten trioxide (WO(3)) coated aluminium (Al) substrate exhibits a reversible color change without light irradiation or an electric power supply. The sample turns blue upon exposure to an aqueous acid solution, but exposure to oxygen restores the original light yellow color. This color change is due to the galvanic redox reaction between WO(3) and Al. 相似文献
93.
Ikeda A Kiguchi K Shigematsu T Nobusawa K Kikuchi J Akiyama M 《Chemical communications (Cambridge, England)》2011,47(44):12095-12097
We confirmed that most C(60) fullerene units are located in the hydrophobic core of the lipid bilayer membrane in water-soluble lipid membrane incorporated C(60) (LMIC(60)) complexes using differential scanning calorimetry (DSC) and (13)C NMR spectra in the presence of radical labels. 相似文献
94.
Kidera M Seto Y Takahashi K Enomoto S Kishi S Makita M Nagamatsu T Tanaka T Toda M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(3):1215-1219
We developed a detection technology for vapor forms of chemical warfare agents (CWAs) with an element analysis system using an electron cyclotron resonance ion source. After the vapor sample was introduced directly into the ion source, the molecular material was decomposed into elements using electron cyclotron resonance plasma and ionized. The following CWAs and stimulants were examined: diisopropyl fluorophosphonate (DFP), 2-chloroethylethylsulfide (2CEES), cyanogen chloride (CNCl), and hydrogen cyanide (HCN). The type of chemical warfare agents, specifically, whether it was a nerve agent, blister agent, blood agent, or choking agent, could be determined by measuring the quantities of the monatomic ions or CN(+) using mass spectrometry. It was possible to detect gaseous CWAs that could not be detected by a conventional mass spectrometer. The distribution of electron temperature in the plasma could be closely controlled by adjusting the input power of the microwaves used to generate the electron cyclotron resonance plasma, and the target compounds could be detected as molecular ions or fragment ions, enabling identification of the target agents. 相似文献
95.
96.
We demonstrate the utility of hierarchical micro/nano structures of electrically conductive carbon composites as anodes for microbial fuel cells (MFCs). To construct the hierarchical structures, carbon nanotubes (CNTs) were directly grown on micro-porous graphite felts at high densities. Using the CNT-modified felts as anodes, power outputs from MFCs were increased ~7 fold compared to those with bare graphite-felt anodes. We also show that this power improvement is sustainable even in MFCs operated with naturally occurring microbial communities. These results suggest the wide utility of the hierarchical micro/nano structures of conductive carbon composites for bio-electrochemical processes. 相似文献
97.
Etou J Ino D Furukawa D Watanabe K Nakai IF Matsumoto Y 《Physical chemistry chemical physics : PCCP》2011,13(13):5817-5823
We have investigated the mechanism of enhanced absorption intensities of vibrational bands of adsorbates on copper meshes with subwavelength holes by measuring and simulating temporal profiles of infrared pulses transmitted through the meshes. As reported previously [Williams et al., J. Phys. Chem. B, 2003, 107, 11871], the absorption intensities of CH stretching bands of alkanethiolate adsorbed on the mesh increase substantially with decreasing hole size. The enhancements of absorption intensities are associated with temporal delays of infrared pulses transmitted through the mesh. Finite difference time domain calculations reproduce the observed pulse delays as a function of hole size. These facts indicate that the delays of transmitted pulses are not caused by coupling of infrared radiation to surface plasmon polaritons propagating on the front and rear surfaces of the mesh, but they are caused by the reduction in group velocity owing to coupling to waveguide modes of mesh holes. Consequently, the strong enhancements of the absorption intensities are attributed to adsorbates inside the holes rather than to those on the mesh surfaces that have been proposed previously. 相似文献
98.
Imamura K Iwasaki S Maeda T Hashimoto K Ohtani B Kominami H 《Physical chemistry chemical physics : PCCP》2011,13(11):5114-5119
Photocatalytic reduction of nitrobenzenes to corresponding aminobenzenes in aqueous suspensions of titanium(IV) oxide (TiO(2)) containing hole scavengers under various conditions was examined. In photocatalytic reduction of m-nitrobenzenesulfonic acid (m-NBS) in the presence of formic acid (FA) under deaerated conditions, m-aminobenzenesulfonic acid (m-ABS) was produced almost quantitatively in acidic suspensions and high efficiency (>99%) in FA utilization as a hole scavenger was achieved. No re-oxidation of m-ABS occurred in acidic conditions both in the presence and absence of FA. The high yield of m-ABS was explained by strong ability of FA as a hole scavenger and possible repulsion of the reduced functional group (ammonium group, -NH(3)(+)) from the protonated, i.e., positively charged TiO(2) surface in acidic suspensions avoiding re-oxidation of m-ABS. Using TiO(2) samples of various physical properties, which had been synthesized by a solvothermal method and post-calcination at various temperatures, effects of physical properties of the TiO(2) samples on m-ABS yield were also investigated. A linear correlation between the amount of m-NBS adsorbed and the m-ABS yield was observed, suggesting that ability of TiO(2) for m-NBS adsorption is one of the key factors for effective photocatalytic reduction of m-NBS to m-ABS. This photocatalytic system can be applied for reduction of aminonitrobenzenes to corresponding diaminobenzenes (DAB) in the presence of oxalic acid as a hole scavenger. High yields of m-ABS and DAB were achieved even when the reactions were performed in the presence of oxygen. 相似文献
99.
Thallada Bhaskar Kazuya Murai Toshiki Matsui Mihai Adrian Brebu Md. Azhar Uddin Akinori Muto Yusaku Sakata Katsuhide Murata 《Journal of Analytical and Applied Pyrolysis》2003,70(2):369-381
The thermal degradation of acrylonitrile-butadiene-styrene copolymer (ABS-Br; 10 g) containing brominated flame retardant (Br: 9.59 wt.%) was carried out at 450 °C using a semi batch operation using two different temperature programs. The heating rate was found to affect the quality of the degradation oil and yield of products (liquid, gas and residue). Data on the effect of the temperature program on the accumulation of liquid products was presented. It was found that the majority of the bromine was concentrated in the carbon residue and while majority of the nitrogen accumulates in the liquid products irrespective of degradation mode. The use of a one step constant heating rate process (I) produced a higher liquid yield (39%), than a two step process (29%). Differences were also noted in the Br and N contained in the liquids produced by the two processes. 相似文献
100.
Kazuya Uenishi Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4422-4430
A novel 5‐membered cyclic dithiocarbonate (DTC) having a siloxane moiety, 5‐(3‐trimethoxysilylpropyloxymethyl)‐1,3‐oxathiolane‐2‐thione, was synthesized from the corresponding epoxide precursor by its cycloaddition with carbon disulfide. The siloxane group underwent condensation reaction by the treatment with water and a basic or acidic catalyst, to afford the corresponding oligomer having siloxane main chain and DTC pendant. The resulting oligomer was liquid and soluble in organic solvents such as THF and chloroform. Treatment of the oligomer with amines resulted in selective ring‐opening reaction of the DTC group, generating a thiol group, which underwent oxidative coupling reaction to make the oligomer successfully cured. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4422–4430, 2005 相似文献