全文获取类型
收费全文 | 171篇 |
免费 | 5篇 |
专业分类
化学 | 95篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 30篇 |
物理学 | 46篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2019年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 7篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1972年 | 4篇 |
1970年 | 4篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 4篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1957年 | 2篇 |
1956年 | 1篇 |
1930年 | 1篇 |
1924年 | 2篇 |
1919年 | 1篇 |
排序方式: 共有176条查询结果,搜索用时 15 毫秒
61.
N. Nishida S. Okuma H. Miyatake S. Shiratake Y. Hidaka T. Murakami Y. Ueda K. Kosuge S. Kambe H. Yasuoka H. Takagi S. Uchida K. Nishiyama K. Nagamine Y. Kuno T. Yamazaki 《Hyperfine Interactions》1991,65(1-4):1027-1034
The negative muon spin rotation method (μ− SR) has been applied to studies of electronic states at oxygen sites of oxide superconductors YBa2Cu3O7, Nd2−x
Ce
x
CuO4−δ (x=0.15, oxygen reduced), LiTi2O4 and related oxide-insulators La2CuO4−δ, CuO, Cu2O. The paramagnetic shifts of μ− trapped at oxygen nuclei in these polycrystalline powder samples have been measured at 300 K. All the measured shifts are
positive. In copper-oxides the paramagnetic shifts are of the order 10−3, while in LiTi2O4 is very small (8.4±3.34×10−5). In YBa2Cu3O7, a fast μ− spin relaxation timeT
2
* (∼ 200 ns) has been observed; the reason for this is unknown and further studies are now in progress. 相似文献
62.
A. S. Levchenko A. N. Khotjantsev A. P. Ivashkin M. Abe M. A. Aliev V. V. Anisimovsky M. Aoki I. Arai Y. Asano T. Baker M. Blecher P. Depommier M. Hasinoff K. Horie H. C. Huang Y. Igarashi T. Ikeda J. Imazato M. M. Khabibullin Yu. G. Kudenko Y. Kuno L. S. Lee G. Y. Lim J. A. Macdonald D. R. Marlow C. R. Mindas O. V. Mineev C. Rangacharyulu S. Shimizu Y. -M. Shin A. Suzuki A. Watanabe N. V. Yershov T. Yokoi 《Physics of Atomic Nuclei》2002,65(12):2232-2237
The form factors of the decay K + → π 0 e + ν e (K e3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 105 K e3 events. The following values of the parameters were obtained: λ +=0.0278±0.0017 (stat.)±0.0015 (syst.), |f S/f +(0)|=0.0040±0.0160 (stat.)±0.0067 (syst.), and |f T/f +(0)|=0.019±0.080 (stat.)±0.038 (syst.). Both scalar f S and tensor f T form factors are consistent with the Standard Model predictions of zero values. 相似文献
63.
Summary The adsorption of polyoxyethylated nonylphenol on calcium carbonate and on carbon black in cyclohexane was studied and compared with that in water. The adsorption of this nonionic surfactant in cyclohexane on calcium carbonate showed a monolayer adsorption isotherm and that on carbon black showed a multilayer adsorption isotherm. The adsorption cross sectional area,A, of the surfactant molecule increased with the number of the ethylene oxide units,n, in both cases, and expressed by the equationsA=49.1n
0.34 for the former case andA=270.n
0.29 for the later case.When either one of the adsorbent or the solvent is polar and the other is nonpolar, the adsorbed molecules form simple oriented monolayer. When both of the adsorbent and the solvent are polar or nonpolar, however, the adsorption takes place in a complicated form and is delicately affected by the impurity and the balance of the polarity of the surfactant molecule.
Zusammenfassung Die Adsorption von Polyoxyäthylen-nonylphenol an Calciumcarbonat und Ruß in Zyklohexan wurde untersucht und das Adsorptionsverhalten mit den Ergebnissen von wäßrigen Lösungen verglichen, die im letzten Bericht mitgeteilt sind. Die Adsorption dieser nichtionischen oberflächenaktiven Substanz in Zyklohexan an Calciumcarbonat zeigte eine monomolekulare und an Ruß eine höhermolekulare Adsorptionsisotherme. In beiden Fällen nahm der Adsorptionsquerschnitt,A, des oberflächenaktiven Moleküls mit der Anzahl der Äthylenoxid-Einheiten,n, zu, und es galten folgende Werte:A=49.1 n0.29 im ersten Fall undA=270.n 0.34 im letzten Fall.Die adsorbierten Moleküle bilden eine einfach orientierte monomolekulare Schicht, wenn von den beiden Komponenten Adsorbens oder Lösungsmittel eines polar und das andere unpolar ist. Wenn jedoch beide polar oder nichtpolar sind, verläuft die Adsorption komplizierter und wird von den Verunreinigungen und der Bilanz der Polarität empfindlich beeinflußt.相似文献
64.
65.
The aim of this work is to propose a biomonitoring method for the simultaneous determination of Cd and Pb in whole blood by simultaneous electrothermal atomic absorption spectrometry for assessment of environmental levels. A volume of 200 microL of whole blood was diluted in 500 microL of 0.2% (wv(-1)) Triton) X-100+2.0% (vv(-1)) HNO3. Trichloroacetic acid was added for protein precipitation and the supernatant analyzed. A mixture of 250 microg W+200 microg Rh as permanent and 2.0% (wv(-1)) NH4H2PO4 as co-injected modifiers were used. Characteristic masses and limits of detections (n=20, 3s) for Cd and Pb were 1.26 and 33 pg and 0.026 microg L(-1) and 0.65 microg L(-1), respectively. Repeatability ranged from 1.8 to 6.8% for Cd and 1.2 to 1.7% for Pb. The trueness of method was checked by the analysis of three Reference Materials: Lyphocheck Whole Blood Metals Control level 1 and Seronorm Trace Elements in Whole Blood levels 1 and 2. The found concentrations presented no statistical differences at the 95% confidence level. Blood samples from 40 volunteers without occupational exposure were analyzed and the concentrations ranged from 0.13 to 0.71 microg L(-1) (0.32+/-0.19 microg L(-1)) for Cd and 9.3 to 56.7 microg L(-1) (25.1+/-10.8 microgL(-1)) for Pb. 相似文献
66.
Goebl JA Black RW Puthussery J Giblin J Kosel TH Kuno M 《Journal of the American Chemical Society》2008,130(44):14822-14833
We demonstrate the solution-phase synthesis of CdS/CdSe, CdSe/CdS, and CdSe/ZnTe core/shell nanowires (NWs). On the basis of bulk band offsets, type-I and type-II heterostructures are made, contributing to the further development of low-dimensional heteroassemblies using solution-phase chemistry. Core/shell wires are prepared by slowly introducing shell precursors into a solution of premade core NWs dispersed in a noncoordinating solvent at moderate temperatures (215-250 degrees C). Resulting heterostructures are characterized through low- and high-resolution transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray analysis. From these experiments, initial shell growth appears to occur through either Stranski-Krastanov or Volmer-Weber island growth. However, beyond a critical shell thickness, nucleation of randomly oriented nanocrystals results in a polycrystalline coat. In cases where overcoating has been achieved, corresponding elemental analyses show spatially varying compositions along the NW radial direction in agreement with expected element ratios. Electronic interactions between the core and shell were subsequently probed through optical studies involving UV-vis extinction spectroscopy, photoluminescence experiments, and transient differential absorption spectroscopy. In particular, transient differential absorption studies reveal unexpected shell-induced changes in core NW Auger kinetics at high carrier densities. Previously seen three-carrier Auger kinetics in CdS (bimolecular in CdSe) NWs were suppressed by the presence of a CdSe (CdS) shell. These observations suggest the ability to influence NW optical/electrical properties by coating them with a surrounding shell, a method which could be important for future NW optical studies as well as for NW-based applications. 相似文献
67.
Hexabromocalix[4]arene derivatives (3a and 3b) possessing pairs of dibromomethylene and bromomethylene groups located at distal or proximal positions of the calix scaffold were prepared via photochemical bromination of tetramethoxycalix[4]arene. The dibromomethylene groups undergo hydrolysis to afford calix[4]arenes possessing pairs of carbonyl groups and bromomethylene groups located at distal or proximal bridges (4a and 4b, respectively). The bromomethylene groups of 4 undergo reactions with nucleophiles under S(N)1 conditions to afford a wide array of derivatives possessing two different chemical modifications at the bridges. 相似文献
68.
Glycans exist in nature in various forms of glycoconjugates, i.e., glycoproteins, glycolipids, and glycosaminoglycans, either in soluble or membrane-bound forms. One of their prominent properties distinguished from nucleic acids and proteins is "heterogeneity" largely attributed to their inherent features of biosynthesis. In general, various methods based on the physicochemical principles have been taken for their separation and structural determination although all of them require prior liberation of glycans and appropriate labeling. On the other hand, a series of carbohydrate-binding proteins, or "lectins," have extensively been used in a more direct manner for cell typing, histochemical staining, and glycoprotein fractionation. Although most procedures conventionally used are useful, unfortunately they lack "throughput" comparable to a performance required for current omics studies. Recently, a novel technique called lectin microarray has attracted increasing attention from not only glycoscientists but also researchers in other fields, because it is straightforward and also informative. The method is innovating in that it enables direct approach to glycoconjugates such as glycoproteins and even cells without liberation of glycans from the core substrate, and therefore can be effectively applied for the sake of differential profiling in various fields. Concept, strategy, and technical advancement of lectin microarray are described. Also, as an introduction to glycomics, the authors explain the motivation to challenge this theme. 相似文献
69.
The simplicial algorithm is a kind of branch-and-bound method for computing a globally optimal solution of a convex maximization
problem. Its convergence under the ω-subdivision strategy was an open question for some decades until Locatelli and Raber proved it (J Optim Theory Appl 107:69–79,
2000). In this paper, we modify their linear programming relaxation and give a different and simpler proof of the convergence.
We also develop a new convergent subdivision strategy, and report numerical results of comparing it with existing strategies. 相似文献
70.
A. Kuno K. Sampei M. Matsuo C. Yonezawa H. Matsue H. Sawahata 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(3):587-590
Neutron induced prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the
sediments collected from the Yasaka River estuary in Oita Prefecture, Japan. The vertical distribution of 33 elements in the
sediments has been determined and compared with that in more polluted estuarine sediments. While the S content increased with
increasing depth because of a sulphide accumulation under reducing condition, the increase in sulphide-forming elements such
as Ag, Cd, Co and Zn was not observed in the deeper section of the Yasaka River estuarine sediments. 相似文献