全文获取类型
收费全文 | 573篇 |
免费 | 45篇 |
国内免费 | 17篇 |
学科分类
数理化 | 635篇 |
出版年
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 10篇 |
2013年 | 29篇 |
2012年 | 33篇 |
2011年 | 38篇 |
2010年 | 20篇 |
2009年 | 23篇 |
2008年 | 24篇 |
2007年 | 22篇 |
2006年 | 21篇 |
2005年 | 31篇 |
2004年 | 32篇 |
2003年 | 28篇 |
2002年 | 28篇 |
2001年 | 13篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1989年 | 3篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1967年 | 4篇 |
1965年 | 3篇 |
1964年 | 4篇 |
1961年 | 4篇 |
1940年 | 2篇 |
1934年 | 3篇 |
1924年 | 3篇 |
排序方式: 共有635条查询结果,搜索用时 0 毫秒
1.
2.
E. Liénard G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière F. Mauger A. Méry O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《Hyperfine Interactions》2006,172(1-3):29-33
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller
decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The
6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to
deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this
experiment. Up to 105 coincidences were recorded during a second run in 2006. 相似文献
3.
Hoang The Ban Kei Nishii Yasuo Tsunogae Takeshi Shiono 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2765-2773
This article reports a synthetic method for a norbornene–ethylene–styrene (N‐E‐S) terpolymer, which has not been well investigated so far, via incorporation of styrene (S) into vinyl‐type norbornene–ethylene (N‐E) copolymers catalyzed by a substituted ansa‐fluorenylamidodimethyltitanium [Me2Si(3,6‐tBu2Flu)(tBuN)]TiMe2 catalyst ( I ) activated with a [Ph3C][B(C6F5)4]/Al(iBu)3 cocatalyst at room temperature in toluene. The resulting terpolymerization product contained the targeted N‐E‐S terpolymer and the contaminated homopolymers, which were then able to be completely removed by solvent fractionation techniques. While homopolystyrene was easily extracted by fractionation with methylethylketone as a soluble part, homopolyethylene and a trace amount of homopolynorbornene could be perfectly separated by fractionation with chloroform as insoluble parts. The detail characterizations of a chloroform‐soluble polymer with gel permeation chromatography, nuclear magnetic resonance, and differential scanning calorimetry analyses proved that it contained a true N‐E‐S terpolymer with long N‐E sequences incorporated with isolated or short styrene sequences. The homogeneity of the morphology together with a single glass transition temperature that proportionally decreased with the increase of the styrene contents indicated that the N‐E‐S terpolymer obtained in this work is a random polymer with an amorphous structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2765–2773, 2007 相似文献
4.
Curran猜想的解答 总被引:2,自引:0,他引:2
本文确定了能作为有限群自同构群的P-群的最佳下最,彻底解决了Curran在1989年提出的关于此最佳下界的三个猜想。 相似文献
5.
6.
Hiroyuki Asanuma Sumie Gotoh Takeshi Ban Makoto Komiyama 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(3):259-264
Poly(2-vinyl-4,6-diamino-1,3,5-triazine) efficiently binds nucleic acid bases and nucleosides in water by using complementary hydrogen bonding. The binding activity decreases in the order: U, T > A C, G. The corresponding monomer shows virtually no activity, indicating a predominant role of polymer effect for the molecular recognition in water. 相似文献
7.
T. Suzuki M. Aida Y. Ban Y. Fujii M. Hara T. Mitsugashira 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):581-583
The separation of trivalent actinides and lanthanides was studied by using newly developed tertiary pyridine-type anion-exchange resin embedded in silica beads. Chromatographic elution experiments were carried out by using a packed column of the new resin and methanol-hydrochloric acid solution as an effluent. We confirmed that the actinides were eluted well from the elution bands of lanthanides. Actinides and lanthanides were eluted according to the reverse order of their atomic number. 相似文献
8.
M. Ban M. Kyoto A. Uedono T. Kawano S. Tanigawa 《Journal of Radioanalytical and Nuclear Chemistry》1996,210(2):479-484
The glass transition and relaxation processes in polystyrene resins with the number average molecular weight ranging from 7.0·102 to 9.8·104 were studied with the positron annihilation technique. The pick-off annihilation lifetime of ortho-positronium (3) and its intensity (I
3) were measured in the temperature range from 20 to 430 K. The glass transition temperature (T
g) was determined as an onset temperature coefficient of 3.T
g shows the molecular weight dependence in these samples. BelowT
g, local motions were detected by measurements ofI
3. The local motions could be observed above 100 K in this experiment.I
3 show the minimum at around 250 K and it does not show molecular weight dependence. 相似文献
9.
Aqueous Titanate Sols from Ti Alkoxide-α-Hydroxycarboxylic Acid System and Preparation of Titania Films from the Sols 总被引:1,自引:0,他引:1
Ohya Tomokazu Ito Masamichi Yamada Keiko Ban Takayuki Ohya Yutaka Takahashi Yasutaka 《Journal of Sol-Gel Science and Technology》2004,30(2):71-81
Aqueous titanate sols were prepared by reactions of titanium tetraisopropoxide (TIP) with -hydroxycarboxylic acids in water. IR and Raman spectra, and elemental analyses of the precipitates obtained from the sols revealed that the carboxylates were chelated to titanium but the Ti species were polymerized to form a cluster that had a colloidal nature. Spin-coating of titania (TiO2) thin films from these sols was also examined. Interestingly, it was found that (004) preferentially oriented anatase films with refractive index of 2.54 were obtained from TIP-lactic acid-NH3 (1:1:1, molar ratio) aqueous sol. This crystallographic orientation was characteristic of the TIP-lactic acid-NH3 (1:1:1) system, and was not affected by the kinds of substrates used and the heating rate of the film. TEM observation indicated that small anatase grains had already formed at 200°C. Therefore, the crystallographic orientation might depend strongly on the structure of the chemical species of the precursor solutions. 相似文献
10.
Reaction mechanisms of the amide hydrolysis from the protonated, neutral, and deprotonated forms of N-(o-carboxybenzoyl)-l-amino acid have been investigated by use of the B3LYP density functional method. Our calculations reveal that in the amide hydrolysis the reaction barrier is significantly lower in solution than that in the gas phase, in contrast with the mechanism for imide formation in which the solvent has little influence on the reaction barrier. In the model reactions, the water molecules function both as a catalyst and as a reactant. The reaction mechanism starting from the neutral form of N-(o-carboxybenzoyl)-l-amino acid, which corresponds to pH 0-3, is concluded to be the most favored, and a concerted mechanism is more favorable than a stepwise mechanism. This conclusion is in agreement with experimental observations that the optimal pH range for amide hydrolysis of N-(o-carboxybenzoyl)-l-leucine is pH 0-3 where N-(o-carboxybenzoyl)-l-leucine is predominantly in its neutral form. We suggest that besides the acid-catalyzed mechanism the addition-elimination mechanism is likely to be an alternative choice for cleaving an amide bond. For the reaction mechanism initiated by protonation at the amidic oxygen (hydrogen ion concentration H(0) < -1), the reaction of the model compound with two water molecules lowers the transition barrier significantly compared with that involving a single water molecule. 相似文献