全文获取类型
收费全文 | 189篇 |
免费 | 4篇 |
专业分类
化学 | 159篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 32篇 |
出版年
2023年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 11篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 9篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有193条查询结果,搜索用时 15 毫秒
21.
Kazuma Gotoh Takahiro Ueda Taro Eguchi Michihisa Miyahara Hiroyuki Ishida 《Journal of Physics and Chemistry of Solids》2008,69(1):147-152
The existence of micropores and the change of surface structure in pitch-based hard-carbon in xenon atmosphere were demonstrated using 129Xe NMR. For high-pressure (4.0 MPa) 129Xe NMR measurements, the hard-carbon samples in Xe gas showed three peaks at 27, 34 and 210 ppm. The last was attributed to the xenon in micropores (<1 nm) in hard-carbon particles. The NMR spectrum of a sample evacuated at 773 K and exposed to 0.1 MPa Xe gas at 773 K for 24 h showed two peaks at 29 and 128 ppm, which were attributed, respectively, to the xenon atoms adsorbed in the large pores (probably mesopores) and micropores of hard-carbon. With increasing annealing time in Xe gas at 773 K, both peaks shifted and merged into one peak at 50 ppm. The diffusion of adsorbed xenon atoms is very slow, probably because the transfer of molecules or atoms among micropores in hard-carbon does not occur readily. Many micropores are isolated from the outer surface. For that reason, xenon atoms are thought to be adsorbed only by micropores near the surface, which are easily accessible from the surrounding space. 相似文献
22.
The mean superficial density of fine particles, such as polystyrene latex particles or ion exchange resin particles, dispersed on a thin supporting film was measured by means of the thickness gauge which used the absorption curves of alpha-rays. The measured absorption curves coincided with the ones calculated from the particle diameter, density, number of particles per unit area and equivalent film thickness to an absorption gas of 1 mmHg. On the other hand, when the particle diameter exceeded a certain limit, the measured mean superficial density which was derived from the pressure displacement of absorption curve considerably differed from the true mean superficial density. This limit can be calculated from the shape of absorption curve, which depends on the alpha-ray spectrum emitted from the source. In the case of the 241Am source used in this study, the limit was about 450 microgram/cm2 for polystyrene latex particles. The mean superficial density of a sample can easily be obtained by measuring the pressure displacement of absorption curve when the maximum thickness difference is below the limit. However, when the maximum thickness difference exceeds the limit, it is necessary to estimate the whole shape of absorption curves. 相似文献
23.
An improved rapid method is described for the detection of restriction endonucleases in enteropathogenic bacteria including Salmonella and Escherichia coli. With the improved method, at least six restriction endonucleases with different specificity were found in 415 strains tested. Five of them were shown to be isoschizomers of known restriction endonucleases, while one seemed to be novel. Among the isoschizomers, SthI endonuclease (isoschizomer of KpnI) in Salmonella thompson appears to be useful; unlike KpnI, SthI generates DNA fragments with a 5′-protruding end. 相似文献
24.
Keikichi Miyahara 《Microchemical Journal》1974,19(4):423-428
A new simple nitrometer has been developed for use in the ultramicrodetermination of nitrogen by the sealed-tube method. The nitrometer consists of a water-filled receiving chamber in which the capillary containing collected nitrogen is placed, and a vertical graduated measuring tube. Nitrogen in the capillary is displaced into the measuring tube by water injected through a hypodermic syringe introduced through a rubber sealing cap at the end of the receiving chamber. 相似文献
25.
26.
It is necessary to develop HTS conductors with a large current capacity and low AC loss characteristics for practical use of HTS power devices. For large capacity power applications, HTS tapes such as Bi-2223 tapes and YBCO coated conductors are assembled. So, it is important to evaluate the characteristics of current distributions in such assembled HTS tapes. However, an adequate measurement method has not been established. In this study, we have tried the development of an indirect measurement method to evaluate the current distributions in stacked HTS tapes. In this method, the current distributions are indirectly found from the results of the field distributions measured by a pickup coil located around the surface of the sample tapes. To confirm the accuracy and the sensitivity of this method, current distributions in a test conductor made of copper tapes are measured. Numerical and measured current distributions are compared. Using this method, the current distributions in stacked Bi-2223 tapes are measured at room temperature and 77 K. On the basis of the obtained results, the characteristics of the AC current distributions in the HTS tapes are discussed. 相似文献
27.
Two steroidal compounds BR-1 (I) and ?2 (II) which had been obtained from the rhizomes of Baker, were isolated also from those of Roth. They were identified, respectively, by X-ray analysis and chemical correlation as 1β,2β,3β,4β,5β,7α-hydroxy-spirost-25(27)-en-6-one and its corresponding 6β-hydroxy compound. 相似文献
28.
Summary A multiple analysis method for the Dumas nitrogen determination has been described. The furnace is provided with eight combustion tubes arranged in a circle around the axis of the furnace. An improved nozzle-type nitrometer, without ground joints, has been designed. The multiple determinations are simultaneously carried out as in usual method, permitting thirty two analyses in a 7-hour working day. The standard deviation-error of estimate from 88 analyses in routine work is ±0.12% N.
Zusammenfassung Ein Verfahren zur gleichzeitigen Durchführung mehrerer Stickstoffbestimmungen nachDumas wurde beschrieben. Der Verbrennungsofen kann acht Verbrennungsrohre in gleichmäßiger Entfernung von seiner Längsachse aufnehmen. Ein verbessertes Düsenazotometer ohne Schliffverbindungen wurde konstruiert. Die Analysen werden gleichzeitig in der üblichen Art durchgeführt, so daß im 7stündigen Arbeitstag 32 Bestimmungen möglich sind. Die mittlere Abweichung von 88 Analysen im Routinebetrieb betrug ± 0,12% N.
Résumé On a décrit une méthode d'analyse multiple pour le dosage de l'azote selonDumas. Le four est muni de huit tubes á combustion disposés suivant un cercle autour de l'axe du four. On a construit un nitromètre perfectionné de type à étranglement, sans joints rodés. On effectue simultanément les dosages multiples comme dans la méthode habituelle, ce qui permet de réaliser trente deux analyses en une journée de travail de 7 heures. L'écart type calculé à partir de 88 analyses dans un travail en série est de ±0,12% N.相似文献
29.
Hasegawa JY Fujimoto K Swerts B Miyahara T Nakatsuji H 《Journal of computational chemistry》2007,28(15):2443-2452
Excited states of fluorescent proteins were studied using symmetry-adapted cluster-configuration interaction (SAC-CI) method. Protein-environmental effect on the excitation and fluorescence energies was investigated. In green fluorescent protein (GFP), the overall protein-environmental effect on the first excitation energy is not significant. However, glutamine (Glu) 94 and arginine (Arg96) have the red-shift contribution as reported in a previous study (Laino et al., Chem Phys 2004, 298, 17). The excited states of GFP active site (GFP-W22-Ser205-Glu222-Ser65) were also calculated. Such large-scale SAC-CI calculations were performed with an improved code containing a new algorithm for the perturbation selection. The SAC-CI results indicate that a charge-transfer state locates at 4.19 eV, which could be related to the channel of the photochemistry as indicated in a previous experimental study. We also studied the excitation and fluorescence energies of blue fluorescent protein, cyan fluorescent protein, and Y66F. The SAC-CI results are very close to the experimental ones. The protonation state of blue fluorescent protein was determined. Conformation of cyan fluorescent protein indicated by the present calculation agrees to the experimentally observed structure. 相似文献
30.
Y. Miyahara T. Fujii S. Watanabe A. Tonoli S. Carabelli H. Yamada H. Bleuler 《Applied Surface Science》1999,140(3-4):428-431
Noncontact atomic force microscopy with frequency modulation detection is a promising technique for surface observation with true atomic resolution. The piezoelectric material itself can be an actuator and sensor of the oscillating probe simultaneously, without the need for additional electro-mechanical transducers or other measurement systems. A vertical resolution of 0.01 nm rms has been achieved using a microfabricated cantilever with lead zirconate titanate thin film in noncontact mode frequency modulation detection. The cantilever also has a sharpened pyramidal stylus with a radius of about 10 nm for noncontact atomic force microscopy. 相似文献