全文获取类型
收费全文 | 673篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
化学 | 487篇 |
晶体学 | 10篇 |
力学 | 13篇 |
数学 | 19篇 |
物理学 | 162篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 21篇 |
2012年 | 28篇 |
2011年 | 41篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 40篇 |
2007年 | 37篇 |
2006年 | 36篇 |
2005年 | 30篇 |
2004年 | 38篇 |
2003年 | 33篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 16篇 |
1973年 | 6篇 |
1968年 | 2篇 |
1964年 | 3篇 |
排序方式: 共有691条查询结果,搜索用时 156 毫秒
61.
Teruyuki Hakoda Muhammed Alamgir Zaman Chowdhury Akihiko Shimada Koichi Hirota 《Plasma Chemistry and Plasma Processing》2009,29(6):549-557
The decomposition of dimethyl sulfide (DMS) at initial concentrations of 4.5–18.0 ppmv in air was studied under electron-beam
(EB) irradiation. Doses to decompose 90% of input DMS were 2.5 kGy for 4.5 ppmv, 3.4 kGy for 10.6 ppmv, and 3.9 kGy for 18.0 ppmv.
HCOOH, (CH3)2SO, and trace CH3OH and (CH3)2SO2 were produced as irradiation products in addition to CO2 and CO. Application of an O3 decomposition catalyst to an irradiated sample gas led to an enhancement in the oxidation of DMS and its products into CO2 and the decomposition of O3. For 10.6 ppmv DMS/air, the mineralization ratio increased from 41% via only EB irradiation to 100% via the combination treatment
at 6.3 kGy. The yield of CO2 to COx increased from 5.3 to 87.6% by combination with catalytic oxidation. This combination treatment enables the irradiation energy
used to deodorize gas streams containing DMS to be reduced. 相似文献
62.
63.
A flow system to monitor the reactions in solutions was constructed, which connected a fluorometer and a luminometer in series. Using a stream through it, the correlation of fluorescence and luminescence was measured. The system was tested with actin. The fluorescence emission gave the signal of polymerization of labeled actin and the luminescence gave that of ATP hydrolysis by actin. The observations showed the correlation between ATP hydrolysis and polymerization. Applications of other proteins to this system will give insights into the characteristics of proteins. 相似文献
64.
Yasutaka Shimada Kazumasa Usuda Hirokazu Okabe Tsuguru Suzuki Kazutsugu Matsumoto 《Tetrahedron: Asymmetry》2009,20(24):2802-2808
The deracemization of 1,2-diol monotosylate derivatives is achieved by the sequential combination of enzymatic hydrolysis and Mitsunobu inversion using a polymer-bound triphenylphosphine. After the lipase-catalysed hydrolysis of the racemic 2-acetoxyhexyl tosylate, the subsequent Mitsunobu reaction without separation causes an inversion of the resulting (R)-alcohol to give the (S)-enantiomer of the acetate as a single product. In particular, the reaction using the polymer-bound triphenylphosphine also proceeds smoothly, and the product is easily separated by filtration from the polymer-bound reagent and its by-products. This deracemization process is applicable to the preparation of several optically active 1,2-diol monotosylates. 相似文献
65.
S. Hirano S. Shimada M. Kuwabara 《Applied Physics A: Materials Science & Processing》2005,80(4):783-786
We demonstrate a method for fabricating a two-dimensional hexagonal array of nanoscale barium titanate ceramic pillars. A precursor array was prepared by introducing a sol solution into an electron-beam resist mold with air holes and subsequently dry etching the unnecessary gel layer formed on the mold. A ceramic array, consisting of barium titanate ceramic pillars with a radius of 85 nm, a lattice constant of 450 nm, and a height of 500 nm, was fabricated by sintering the precursor array at 1073 K. The reflection spectra for the ceramic array in the visible range revealed the underlying photonic band gaps, which were in good agreement with results calculated using a plane-wave method. PACS 77.84.-s; 42.70.-a; 42.70.Qs 相似文献
66.
N-Benzyl-D-glucamine dithiocarbamate (BGD), N-p-hydroxymethylbenzyl-D-glucamine dithiocarbamate (HBGD), and N-p-carboxybenzyl-D-glucamine dithiocarbamate (CBGD) were compared for their relative efficacies in the distribution and excretion of cadmium in mice exposed to cadmium. Mice were injected intraperitoneally with 109CdCl2 (1 mg of Cd/kg and 2 microCi of 109Cd/one animal). Three days later, they were injected with chelating agents (400 mumol/kg) every other day for 2 weeks. After injections of BGD and HBGD, cadmium was excreted mainly in the feces through the bile, and the fecal excretion of cadmium by HBGD was significantly higher than that by BGD or CBGD. These chelating agents increased the urinary excretion of cadmium to a small extent. The hepatic cadmium content was decreased only after HBGD injection. Also, the injection of HBGD caused a much greater decrease in renal cadmium content than did BGD or CBGD. These chelating agents did not result in the redistribution of cadmium to the brain, testes, or heart. The growth of mice was only slightly retarded by injections of these chelating agents. The results of this study indicate that the injection of HBGD to mice pretreated with cadmium can remove cadmium from the body, mainly through fecal excretion, without redistribution of cadmium to other tissues such as the brain, testes, and heart, more effectively than BGD or CBGD. 相似文献
67.
Phosphotransacetylase (PTA) is immobilized on AF-Tresyl TOYOPEARL 650 gel and used on-line in a stainless-steel column (10 × 4 mm i.d.). CoA-SH liberated enzymatically from acetyl-CoA is reacted with Ellman's reagent [5,5′-dithiobis(2-nitrobenzoic acid)] in the carrier stream. The calibration graph for acetyl-CoA is linear from 4 × 10?6 to 4 × 10?4 M and the detection limits is 8 × 10?7 M. The immobilized enzyme can be employed for over 4 months without any significant decrease in activity. The enzyme retains its activity in methanol even though the initial rate of reaction is decreased. 相似文献
68.
Naoyuki Shimada 《Tetrahedron letters》2010,51(50):6572-6575
A catalytic asymmetric synthesis of descurainin has been achieved by incorporating an enantioselective 1,3-dipolar cycloaddition, a stereoselective alkene hydrogenation, an oxidation with Fremy’s salt and a regioselective demethylation with NbCl5 as the key step. The 1,3-dipolar cycloaddition of a carbonyl ylide derived from tert-butyl 2-diazo-5-formyl-3-oxopetanoate with 4-hydroxy-3-methoxyphenylacetylene in the presence of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(R)-tert-leucinate], Rh2(R-TCPTTL)4, provided an 8-oxabicyclo[3.2.1]octane skeleton in 95% ee. 相似文献
69.
Mizoshita N Yamanaka K Shimada T Tani T Inagaki S 《Chemical communications (Cambridge, England)》2010,46(48):9235-9237
Polycondensation of 9-mesityl-10-methylacridinium-bridged organosilane in the presence of a nonionic surfactant yielded a mesostructured organosilica solid with a functional framework that exhibited long-lived photoinduced charge separation. 相似文献
70.
Asako Shimada Tomoko Haraga Akiko Hoshi Yutaka Kameo Mikio Nakashima Kuniaki Takahashi 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(3):765-770
In order to analyze actinide elements in radioactive metal waste, the dissolution and chemical separation conditions were optimized. The surfaces of a type 304 stainless steel plate and of pipe waste sampled from the prototype advanced thermal reactor (Fugen) were dissolved in mixed acid solution (HNO3:HCl:H2O = 1:1:4). The resulting solution was evaporated to dryness and dissolved with 2 mol/dm3 of HNO3 to prepare sample solutions. In order to analyze trivalent actinide elements in the sample solution containing a large amount of Fe(III) (>0.1 g) using TRU resin, the effect of Fe(III) concentration on the recovery of Am(III) and reduction effect of Fe(III) to Fe(II) with ascorbic acid were studied. On the basis of results of this study, chemical separation scheme was constructed and Pu and Am in the sample solutions were separated. Thorium and U in the sample solutions were separated with UTEVA resin. High recoveries for all experimented elements were obtained from the analysis of spiked sample solutions, the effectiveness of the method was confirmed. 相似文献