全文获取类型
收费全文 | 598篇 |
免费 | 26篇 |
国内免费 | 6篇 |
专业分类
化学 | 437篇 |
晶体学 | 4篇 |
力学 | 7篇 |
数学 | 33篇 |
物理学 | 149篇 |
出版年
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 40篇 |
2012年 | 31篇 |
2011年 | 23篇 |
2010年 | 17篇 |
2009年 | 13篇 |
2008年 | 58篇 |
2007年 | 44篇 |
2006年 | 27篇 |
2005年 | 27篇 |
2004年 | 12篇 |
2003年 | 18篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 15篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1967年 | 4篇 |
排序方式: 共有630条查询结果,搜索用时 46 毫秒
1.
A method for the determination of 5 triazine herbicides and 12 degradation products in environmental water samples using liquid chromatography-electrospray ionization mass spectrometry (LC/ESI/MS) has been developed. The pesticides in water were extracted with two types of solid phase: a styrene-divinylbenzene copolymer and a graphitized carbon black. Desorption solvents for the extracted compounds were acetone for the styrene-divinylbenzene copolymer and methanol for the graphitized carbon black. Overall recoveries from ground water and river water ranged from 73% to 111%. The limits of detection (LODs) were 0.2 to 28 ng l(-1). This method was applied to several ground water samples. 相似文献
2.
A. Noda S. Nakamura Y. Iwashita S. Sakabe M. Hashida T. Shirai S. Shimizu H. Tongu H. Ito H. Souda A. Yamazaki M. Tanabe H. Daido M. Mori M. Kado A. Sagisaka K. Ogura M. Nishiuchi S. Orimo Y. Hayashi A. Yogo S. Bulanov T. Esirkepov A. Nagashima T. Kimura T. Tajima T. Takeuchi K. Matsukado A. Fukumi Z. Li 《Laser Physics》2006,16(4):647-653
In order to widely spread out particle beams utilized in cancer therapy, laser-produced ions are developed as the injection beam for an ion synchrotron dedicated for cancer therapy. Such a laser ion source is expected to contribute largely to the realization of compactness of the size and low cost of the cancer therapy accelerator. The energy spectrum of the laser-produced ions, however, has no peak, but their intensities decrease exponentially according to the increase of the energy. For the purpose of modifying such a situation, we have proposed a scheme to rotate the beam in the longitudinal phase space with the use of the RF electric field, which is phase-adjusted with the pulse laser. We aim for a reduction of the energy spread of ± 5% selected by an energy analyzer and slits to ±1% by such phase rotation. For this purpose, a quarter wavelength resonator with two gaps with the same resonant frequency as the source laser has already been fabricated, together with its RF power source. The above phase rotation system and its recent experimental realization are presented. 相似文献
3.
In the recycling of poly(vinyl chloride) (PVC), it is required to discriminate every plasticizer for quality control. For this purpose, the near-infrared spectra were measured for 41 kinds of PVC samples with different plasticizers (DINP, DOP, DOA, TOTM and Polyester) and different plasticizer contents (0-49%). A neural-network analysis was applied to the near-infrared spectra pretreated by second-derivative processing. They were discriminated from one another. The neural-network analysis also allowed us to propose a calibration model which predicts the contents of plasticizers in PVC. The correlation coefficient (R) and the root-mean-square error of prediction (RMSEP) for the DINP calibration model were found to be 0.999 and 0.41 wt%, respectively. In comparison, a partial least-squares regression analysis was carried out. The R and RMSEP of the DINP calibration model were calculated to be 0.993 and 1.27 wt%, respectively. It is found that a near-infrared spectra measurement combined with a neural-network analysis is useful for plastic recycling. 相似文献
4.
We have developed a sensitive method for the measurement of rhodanese activity in human serum which is based on the colorimetric method for the determination of thiocyanate produced from methanethiosulfonate and cyanide as substrates. Thiocyanate gives a red complex with ferric ion in an acidic condition. The present method is about 70-fold more sensitive than the conventional method using cyanide and thiosulfate as substrates and correlates well (r = 0.997) with the conventional method in bovine liver rhodanese. Within-run precision of the method is 0.91% for 420 units/l serum and the calibration curve is linear up to 1850 units/l. The normal value for human serum, determined by the present method on 31 healthy persons, was 20.9 +/- 20.0 units/l (mean +/- 2S.D.). Rhodanese activity was clearly elevated in some serum samples which were observed at abnormal values in some biochemical diagnostic tests and showed significant positive correlations with guanase activity (r = 0.728, p less than 0.01) and glutamic-oxalacetic transaminase activity (r = 0.625, p less than 0.01). 相似文献
5.
Infrared and Raman spectra of 1,2-dibromoethane CH2BrCH2Br and CD2BrCD2Br were observed in the liquid state, and the fundamental frequencies were determined by comparison with those of related molecules. Infrared absorption intensities of fundament bands were measured in the liquid state, and the intensity data were interpreted on the basis of the valence-optical theory. From the converged value of a population ratio, the energy difference between the trans and gauche isomers was determined, which was in good agreement with the value obtained from the temperature effect of the IR spectrum. 相似文献
6.
The effect of CO2 adsorption on the catalytic activity of alkaline earth metal oxides in the title reaction reveals that the number of active (basic) sites follows the order MgO>CaO>SrO>BaO, and the order of base strength is MgO
CO2 , () : MgO>CaO>SrO>BaO, : MgO相似文献
7.
Isotropie Raman spectra of the symmetric C—H stretching bands of several organic molecules are measured in the neat liquid and in solvents including water. The linewidths are interpreted on the basis of the vibrational dephasing model, and intermolecular interactions between the solutes and solvents are discussed. 相似文献
8.
Kazutoshi Tanabe 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(1-2):267-273
Raman spectra of several organic molecules which form hydrate clathrates have been measured in aqueous solution, and the hydration structure around those molecules has been investigated from the analysis of Raman linewidth data. 相似文献
9.
Seiji Tsuzuki Kazumasa Honda Tadafumi Uchimaru Masuhiro Mikami Kazutoshi Tanabe 《Journal of the American Chemical Society》2002,124(1):104-112
A model chemistry for the evaluation of intermolecular interaction between aromatic molecules (AIMI Model) has been developed. The CCSD(T) interaction energy at the basis set limit has been estimated from the MP2 interaction energy near the basis set limit and the CCSD(T) correction term obtained by using a medium size basis set. The calculated interaction energies of the parallel, T-shaped,and slipped-parallel benzene dimers are -1.48, -2.46, and -2.48 kcal/mol, respectively. The substantial attractive interaction in benzene dimer, even where the molecules are well separated, shows that the major source of attraction is not short-range interactions such as charge-transfer but long-range interactions such as electrostatic and dispersion. The inclusion of electron correlation increases attraction significantly. The dispersion interaction is found to be the major source of attraction in the benzene dimer. The orientation dependence of the dimer interaction is mainly controlled by long-range interactions. Although electrostatic interaction is considerably weaker than dispersion interaction, it is highly orientation dependent. Dispersion and electrostatic interactions are both important for the directionality of the benzene dimer interaction. 相似文献
10.