全文获取类型
收费全文 | 379篇 |
免费 | 10篇 |
专业分类
化学 | 288篇 |
晶体学 | 4篇 |
力学 | 3篇 |
数学 | 9篇 |
物理学 | 85篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 24篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 13篇 |
2005年 | 10篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1974年 | 2篇 |
1970年 | 3篇 |
1968年 | 3篇 |
1961年 | 1篇 |
排序方式: 共有389条查询结果,搜索用时 15 毫秒
81.
Masanao Ozawa 《Physics letters. A》2004,320(5-6):367-374
Universally valid uncertainty relations are proven in a model independent formulation for inherent and unavoidable extra noises in arbitrary joint measurements on single systems, from which Heisenberg's original uncertainty relation is proven valid for any joint measurements with statistically independent noises. 相似文献
82.
83.
Y. Maeda N. Tsutsumi Y. Takashima 《Journal of Radioanalytical and Nuclear Chemistry》1985,93(5):253-261
Gamma-ray irradiations for various spin crossover iron/III/ complexes were performed in order to examine the spin transition mechanism. The difference of the spin transition mechanisms was reflected in the differences of the fractions that the electronic state of iron atoms changed to low-spin at low temperature and the results were explained by using a phenomenological model. 相似文献
84.
In this paper, domain optimization problems for both linear and nonlinear elastic structures are studied. The first variation and the second variation of the objective function are calculated in terms of the solution, of the first variation of the solution for the primal elastic system, and of the adjoint variables introduced. The adjoint variables obey a (fictitious) linear elastic system in contrast with the nonlinear adjoint systems introduced by Dems and Mróz, and by Dems and Haftka. From these results, the first-order and the second-order necessary conditions that an optimal domain should satisfy are immediately derived.Portions of this paper were presented at the 5th IFAC Symposium on Control of Distributed Parameter Systems, Perpignan, France, 1989. The authors would like to express their sincere thanks to the referees for their critical readings. 相似文献
85.
Y Yoshida H Takashima Y Kawasaki S Yasuda T Tamai N Hosokawa T Miyamoto S Matuno K Sakamoto S Nakase 《Radioisotopes》1988,37(9):525-528
The clinical significance of serum SCC antigen level was evaluated by the monoclonal antibody method (SCC.RIABEAD Dinabot Co. Ltd). Patients with squamous cell carcinoma showed a high positive SCC antigen level and positive rate elevated with the advance of the clinical stage. The serum SCC antigen level was decreased by treatment, and it increased again before obvious clinical recurrence was recognized. The results suggest that measurement of serum SCC antigen level is useful as a follow up of cancer treatment. 相似文献
86.
An alternative synthetic route to 1,4,5-trisubstituted imidazoles from α-imino ketone, which can be prepared from imidoyl chlorides and aromatic aldehydes via N-heterocycle carbene-catalyzed aroylation was developed. This methodology consists of simple transformations, allowing a rapid access to imidazole derivatives with various aryl substituents at the desired positions. 相似文献
87.
Optical absorption coefficient spectra of thin silicon films were precisely investigated using a simple reflectance system with total reflectance mirrors placed on the rear side of samples in order to cancel an interference effect in a range between 1.1 eV and 3 eV. The absorption coefficient decreased according to crystallization as the laser energy increased and it got similar to that of single crystalline silicon in the range of 1.7 eV 3 eV. However, the absorption coefficient was higher than 102 cm–1 in the photon energy lower than 1.3 eV. This probably results from band tail states caused by defect states localized at grain boundaries in the crystallized films. 2.5%-phosphorus doped laser crystallized silicon films had a high optical absorption coefficient ( > 104 cm–1) in the low photon energy range (1.1 eV 1.7 eV) caused by free carriers produced from the dopant atoms activated in the silicon films. The experimental results gave the carrier density of 1.3 × 1021 cm3 and the carrier mobility of 20 cm2/Vs. 相似文献
88.
The sorption of the chromium(III)-diphenylcarbazone complex (Cr-DPC) with XAD-2 has been investigated, for use in the separation of Cr(VI) from Cr(III) species in natural waters. Cr-DPC is formed from the reaction of Cr(VI) with diphenylcarbazide, but Cr(III) species give no reaction in aqueous solution. The addition of sodium chloride or sodium beta-naphthalenesulphonate markedly enhances the sorption. The Cr-DPC sorbed on XAD-2 can be almost completely eluted with organic solvents, especially methanol, but about 5% of it is irreversibly sorbed and cannot be eluted. The excess of diphenylcarbazide and some of the organic matter in natural waters are also sorbed on XAD-2 but most of this can also be eluted with methanol. Organic matter which interferes with measurement of the absorbance of Cr-DPC can almost all be removed by extraction with chloroform. By use of these techniques, Cr(VI) in sea-water has been determined by the standard-addition method. Although about 50 litres of sea-water are necessary for the analysis, organic and colloidal Cr(III) species do not interfere. 相似文献
89.
K. Sakamoto Y. Hamajima S. Yamaguchi T. Takashima K. Itoh 《Journal of Radioanalytical and Nuclear Chemistry》1980,60(2):411-422
Samples of an andesite (Asama-yama, Japan) and a basalt (Kilauea, Hawaii) were finely fractioned by density and the U distributions
among the separates were determined by homogenized fission track method. Groundmass was found to be enriched with U; one half
of the andesite U and almost all of the basalt U are accounted for by the groundmass U. Cerium and other REE are correlated
with U. In the andesite separates Na is accompanied by these elements, but Fe and Co are rather anticorrelated. Uranium concentrations
in the bulk samples and some of the separates were then compared with those determined by133Xe extracted by heating at 1600°C. Fissiogenic133Xe seems to become labile in groundmass, especially of the andesite, during reactor irradiations for 5 h or more. Stepwise
heating experiments suggested that133Xe in U-rich groundmass tends to escape at low temperatures and the remaining133Xe is mostly retained in highly refractory sites in phenocryst rather poor in U. 相似文献
90.
Kinetic study of the annealing of fission tracks in a Fe2O3KPO3 glass containing 100 ppm of uranium
The kinetics of the annealing of fission tracks in an artificial glass were studied using an optical microscope. The annealing experiments were performed in an electric furnace at 160–230°C for 15–160 min. The measurement of the fission tracks through an optical microscope was carried out after etching the annealed tracks with 10 N NaOH aqueous solution at 40°C. All reactions were found to be of first order within the annealing temperatures. An activation energy of 0.66 eV for the annealing reaction was obtained from the Arrhenius plot of the rate constants determined at 160, 190, 210, and 230°C. 相似文献