全文获取类型
收费全文 | 744篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
化学 | 559篇 |
晶体学 | 5篇 |
力学 | 4篇 |
数学 | 56篇 |
物理学 | 145篇 |
出版年
2022年 | 12篇 |
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 23篇 |
2013年 | 41篇 |
2012年 | 32篇 |
2011年 | 28篇 |
2010年 | 14篇 |
2009年 | 17篇 |
2008年 | 28篇 |
2007年 | 39篇 |
2006年 | 23篇 |
2005年 | 39篇 |
2004年 | 26篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 16篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 19篇 |
1984年 | 23篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1970年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有769条查询结果,搜索用时 15 毫秒
81.
In this paper we are concerned with solutions, in particular with univalent solutions, of the Loewner differential equation
associated with non-normalized subordination chains on the Euclidean unit ball B
n
in
\mathbbCn{\mathbb{C}^n}. The main result is a generalization to higher dimensions of a well known result due to Becker. Various particular cases
of this result have been recently obtained for subordination chains with normalization Df(0,t)=etIn{Df(0,t)=e^tI_n} or Df(0, t) = e
tA
, t ≥ 0, where
A ? L(\mathbbCn,\mathbbCn){A\in L(\mathbb{C}^n,\mathbb{C}^n)}. We also determine the form of the standard solutions to the Loewner differential equation associated with generalized spirallike
mappings. In the last section we obtain the form of the solution in the presence of coefficient bounds. 相似文献
82.
The difficulty in ion-chromatographic determination of nitrite in aqueous solutions containing a high concentration of chloride arises mainly from incomplete resolution of the peaks for these anions on the separation column whose efficiency is not high. A photometric measurement of iodine formed by a reaction of nitrite with iodide has been found to make it possible to determine, chromatographically, trace amounts of nitrite without any interference from chloride; chloride does not oxidize iodide to produce iodine. The proposed method was based on the separation of nitrite from matrix anions on a silica-based anion-exchange column with a 1.5·10−3 M phthalate eluent (pH 5.0), followed by photometric measurement of the iodine (as triiodide) formed via a post-column reaction of the separated nitrite with iodide. The optimal conditions for the post-column reaction were established by varying the concentrations of iodide, copper(II) and nitric acid in a post-column-reaction solution and the length of a reaction tube. A calibration graph for nitrite, plotted as peak heights versus concentrations, was linear up to 1.50·10−5 M (690 ppb). The detection limit, defined at S/N=3, was 1.00·10−7 M (4.60 ppb) nitrite. The presence of chloride ions up to 0.01 M did not give any interference to the determination of nitrite. This method was successfully applied to the determination of nitrite in lake water, river water, sewage works water and snow samples without any pretreatment. 相似文献
83.
Mutsuhisa Furukawa Yukinori Hamada Ken Kojio 《Journal of Polymer Science.Polymer Physics》2003,41(20):2355-2364
Functionally graded polyurethane elastomers (FGPUEs) were prepared with two molds fixed at different temperatures (30 and 150 °C). The effects of the molar ratio of the curing agent (60/40, 75/25, or 97/3 1,4‐butane diol/1,1,1‐trimethylol propane) and the molecular weight of the polymer glycol (number‐average molecular weight = 2000 or 3000) on the molecular aggregation state and mechanical properties of the FGPUEs were investigated with differential scanning calorimetry, polarized optical microscopy, dynamic viscoelastic measurements, and tensile tests. The aggregation state of the FGPUEs was changed continuously from the one side (lower temperature side) to the other side (higher temperature side); for example, the glass‐transition temperature gradually increased in this direction. Also, the number of spherulites formed in the FGPUEs increased in the same manner. In the mechanical tests, the tensile strength and elongation at break of the lower temperature side were higher than those of the higher temperature side. This was correlated with the strong phase separation of the lower temperature side. The poly(oxytetramethylene glycol)‐based FGPUE with a chain extender of 75 wt % showed the largest degree of the temperature gradient. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2355–2363, 2003 相似文献
84.
This paper describes a control system of stockers for radioactive source in storage room at laboratory for tracer experiment. The system is composed of a personal computer, a locker controller, three card readers, a monitor TV, and a video tape recorder (VTR). The personal computer controls other equipment with a registered user's number. When a user inserts an identification card into the card reader, the computer memorizes assigned gate number, the user's number and the time; it processes those data and prints out a document. The locker controller releases the electric key of user's locker which is designated by the computer. The VTR records the person entering into the storage room to identity if he uses his card. This system proved to effectively prevent intrusion into the storage room of an unregistered person or to use carelessly other user's source; in addition it can record precisely the stock of radioactive source. 相似文献
85.
The adsorption and decomposition of NO on a K-deposited Pd(1 1 1) surface were investigated using X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and temperature-programmed desorption. For the K-deposited Pd(1 1 1) surface, two different NO adsorption sites were observed in addition to the Pd site. On the clean Pd(1 1 1) surface, the adsorption of NO was purely molecular and reversible, but on the K-deposited surface, the adsorbed NO decomposed at two different temperatures, 530 and 610 K. These results indicate that the NO adsorption and decomposition sites were newly created by the deposition of K onto the Pd(1 1 1) surface. 相似文献
86.
Dr. M. Tanaka Prof. Dr. M. Hamada Prof. Dr. Y. Iwata 《Archive of Applied Mechanics (Ingenieur Archiv)》1982,52(1-2):95-104
Summary This paper presents a boundary element formulation for elastostatic problems. The formulation is expressed in terms of the matrix notation, so that it is easily applicable to an available system of matrix structural analysis. A computer program developed is used to calculate the stress intensity factor K
I for some example problems in plane elasticity. Comparison is made between the boundary element calculations and other solutions, whereby the effectiveness of the boundary element method is demonstrated.
Berechnung eines zweidimensionalen Spannungsintensitätsfaktors mit der Methode der Bandelemente
Übersicht Dieser Aufsatz bietet eine Formulierung elastostatischer Probleme durch die Methode der Randelemente an. Die Formulierung benutzt eine Darstellung in Matrizenbezeichnung, so daß sie auf ein verfügbares System für Matrizenstrukturberechnung einfach anwendbar ist. Ein ausgebautes Computerprogramm wird auf die Berechnung des Spannungsintensitätsfaktors K i für einige Beispiele in der ebenen Elastizität angewendet. Die mittels der Randelemente erhaltenen Ergebnisse werden mit anderen Lösungen verglichen. Dadurch zeigt sich die Wirksamkeit der Methode der Randelemente.相似文献
87.
Tetrabenzoperipentacene: Stable Five‐Electron Donating Ability and a Discrete Triple‐Layered β‐Graphite Form in the Solid State 下载免费PDF全文
Akinobu Matsumoto Dr. Mitsuharu Suzuki Dr. Daiki Kuzuhara Dr. Hironobu Hayashi Prof. Dr. Naoki Aratani Prof. Dr. Hiroko Yamada 《Angewandte Chemie (International ed. in English)》2015,54(28):8175-8178
An oxidative ring‐closure reaction of a tetranaphthylpyrene derivative led to the synthesis of a 56 all‐carbon conjugated tetrabenzoperipentacene. In the single‐crystal X‐ray structure, three molecules make a triple‐layered cluster by π‐stacking, wherein each layer rotates by 120°, and is thus considered a petit β‐graphite. As for the optical properties, the Stokes shift is extremely small (10 cm?1), thus indicating its remarkably rigid framework. The tetrabenzoperipentacene exhibits reversible five‐electron oxidation waves in cyclic voltammetry, and is regarded as a counterpart to the fullerene C60 in terms of stable multicharge‐storage nanocarbon materials. 相似文献
88.
89.
90.
Sakamoto K Takashima Y Hamada N Ichida H Yamaguchi H Yamamoto H Harada A 《Organic letters》2011,13(4):672-675
An energy transfer process was investigated using cyclodextrin-oligothiophene rotaxanes (2T-[2]rotaxane). The excited energy of 2T-[2]rotaxane is transferred to the sexithiophene derivative which is included in the cavity of β-CD stoppers of 2T-[2]rotaxane. 相似文献