全文获取类型
收费全文 | 1682篇 |
免费 | 62篇 |
国内免费 | 6篇 |
专业分类
化学 | 1414篇 |
晶体学 | 24篇 |
力学 | 14篇 |
数学 | 68篇 |
物理学 | 230篇 |
出版年
2022年 | 13篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 36篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 43篇 |
2015年 | 32篇 |
2014年 | 55篇 |
2013年 | 68篇 |
2012年 | 100篇 |
2011年 | 113篇 |
2010年 | 74篇 |
2009年 | 50篇 |
2008年 | 115篇 |
2007年 | 108篇 |
2006年 | 112篇 |
2005年 | 126篇 |
2004年 | 113篇 |
2003年 | 94篇 |
2002年 | 71篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 28篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 22篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 3篇 |
排序方式: 共有1750条查询结果,搜索用时 15 毫秒
61.
Masayuki Oba 《Journal of polymer science. Part A, Polymer chemistry》1996,34(4):651-658
The effect of new additives on the thermal conversion of a range of polyamic acids to polyimides at temperatures lower than 100°C was investigated using infrared spectroscopy. Additives such as m-hydroxybenzoic acid, p-hydroxyphenylacetic acid, and p-hydroxybenzenesulfonic acid were found to be highly effective as curing catalysts or accelerators. The degree of imidization of polyamic acids in the presence of additives increased with an increase in the reaction temperature, and complete imidization was achieved at 140–200°C. The reaction was characterized by a rapid rate that slowed with time. © 1996 John Wiley & Sons, Inc. 相似文献
62.
Mohamad Kamarol Mohd Jamil Shinya Ohtsuka Masayuki Hikita Hitoshi Saitoh Masayuki Sakaki 《Journal of Electrostatics》2011,69(6):611-617
This paper presents the decomposition by-products of trifluro-iodo-methane and their relative proportions in the gas phase under the occurrence of partial discharge. The experiment was performed in the presence of water vapor from 250 to 400 ppm under a non-uniform electric field configuration. The experimental results reveal that the by-products of C2F6, C2F4, C2F5I with the amount of 1300, 200, and 55 (CH3I) ppm, respectively, were produced for a cumulative charge of 161 mC. Other by-products, such as C3F8, CHF3, C3F6 CH3I were obtained at less than 30 ppm C2F6 was the dominant gas by-product of trifluro-iodo-methane suffering partial discharge. 相似文献
63.
The acceptable range of speech level as a function of background noise level was investigated on the basis of word intelligibility scores and listening difficulty ratings. In the present study, the acceptable range is defined as the range that maximizes word intelligibility scores and simultaneously does not cause a significant increase in listening difficulty ratings from the minimum ratings. Listening tests with young adult and elderly listeners demonstrated the following. (1) The acceptable range of speech level for elderly listeners overlapped that for young listeners. (2) The lower limit of the acceptable speech level for both young and elderly listeners was 65 dB (A-weighted) for noise levels of 40 and 45 dB (A-weighted), a level with a speech-to-noise ratio of +15 dB for noise levels of 50 and 55 dB, and a level with a speech-to-noise ratio of +10 dB for noise levels from 60 to 70 dB. (3) The upper limit of the acceptable speech level for both young and elderly listeners was 80 dB for noise levels from 40 to 55 dB and 85 dB or above for noise levels from 55 to 70 dB. 相似文献
64.
Teruyuki Nakajima Masayuki Tanaka 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,29(6):521-537
Transfer of solar radiation in the combined atmosphere and ocean system is evaluated by the matrix operator method. Derivation of the reflection and transmission matrices required for applying the matrix method is discussed introducing the shadowing effect of light by the ocean waves. Spectral and total radiation fields just above and below the ocean surface, as well as the top of the atmosphere, are numerically calculated using several optical models of the atmosphere, ocean, and wind roughened ocean surface. Dependencies of radiance and flux reflectivity on the wind velocity and optical property of the ocean body are discussed in detail. 相似文献
65.
Yoshiaki Tsunawaki Nobuhisa Ohigashi Kunioki Mima Shin-ichiro Kurama Kazuo Imasaki Masayuki Fujita Chiyoe Yamanaka Sadao Nakai 《International Journal of Infrared and Millimeter Waves》1995,16(1):317-325
A three dimensional simulation software system developed to estimate a free electron laser (FEL) gain has been applied to FEL using a standard plane polarized wiggler and an alternately shifted magnet wiggler. It is seen for the latter wiggler that a large filling factor could be selected and each maximum gain corresponding to each orbit of electron beam concentrates at a certain frequency region of FEL radiation. It is, therefore, implied that a proper shift between the adjacent magnets in the wiggler produces the improvement of the FEL gain. 相似文献
66.
Tuong Lan Nguyen Masayuki Dokiya Shaorong Wang Hiroaki Tagawa Takuya Hashimoto 《Solid State Ionics》2000,130(3-4):229-241
The electrical property of (La1−xSrx)1−z(Al1−yMgy)O3−δ (LSAM; x≤0.3, y≤0.15 and z≤0.1) was measured using the DC four-probe method as a function of temperature (500–1000°C) and oxygen partial pressure (1–10−22 atm). Among LSAMs, (La0.9Sr0.1)AlO3−δ showed the highest ionic conductivity, σi=1.3×10−2 S cm−1 at 900°C. A simultaneous substitution at A and B sites or A site deficiency is expected to create larger oxygen vacancy and higher ionic conductivity. However, it showed a negative effect. The effect of the vacancy increase did not effect monotonously the ionic conductivity. It was found that the concentration of oxygen vacancy, [VO], influences not only the oxide ion conductivity, σi, but also the mobility, μv, of [VO]. These properties exhibit a maximum at around [VO]=0.05. With the increase in [VO], the activation energy, Ea, of the ionic conduction dropped from 1.8 to ca. 1.0 eV at [VO]=0.05 and became almost constant at [VO]>0.05. The dependency of the pre-exponential term, μ0v, and Ea on [VO] was analyzed and their effect on μv and σi was discussed with respect to crystal structure and defect association. It was estimated that the crystal structure mainly governs these properties. The effect of defect association could not be ignored but is considered to be a complicated correlation. 相似文献
67.
Masayuki Kumon 《Annals of the Institute of Statistical Mathematics》1992,44(2):239-260
The present paper treats the identification of parametric nonminimum phase transfer function. We propose a method of identification based on the inner outer factorization of stable transfer function. It consists of identifying the outer and inner parts of a transfer function separately. The outer part is identified by the use of the second-order spectral estimate from the observed linear process, while the inner part is identified by the use of a higher-order cumulant spectral estimate from the observed process. Respective parameter estimators are determined in the light of asymptotic efficiency. In order to estimate the order of the inner part of a transfer function, a criterion is proposed. It is introduced based on the same principle as in the case of Akaike's AIC. 相似文献
68.
Masayuki Ito 《Physica D: Nonlinear Phenomena》1984,14(1):1-28
This paper is concerned with the competitive-diffusive systems , with homogeneous Dirichlet boundary conditions. From a global bifurcation view point, the dependency of steady-states on the parameters ai, bi, ci and di (i = 1, 2) is investigated. In particular, bifurcation of coexist ence solutions amd their stabilities are our main interests. 相似文献
69.
Morimoto M Sato H Kobayashi M 《The Journal of the Acoustical Society of America》2004,116(3):1607-1613
Listening difficulty ratings, using words with high word familiarity, are proposed as a new subjective measure for the evaluation of speech transmission in public spaces to provide realistic and objective results. Two listening tests were performed to examine their validity, compared with intelligibility scores. The tests included a reverberant signal and noise as detrimental sounds. The subject was asked to repeat each word and simultaneously to rate the listening difficulty into one of four categories: (1) not difficult, (2) a little difficult, (3) fairly difficult, and (4) extremely difficult. After the tests, the four categories were reclassified into, not difficult [response (1)] and some level of difficulty, (the other 3 responses). Listening difficulty is defined as the percentage of the total number of responses indicating some level of difficulty [i.e. not (1)]. The results of two listening tests demonstrated that listening difficulty ratings can evaluate speech transmission performance more accurately and sensitively than intelligibility scores for sound fields with higher speech transmission performance. 相似文献
70.
Kumagai Yuta Kimura Atsushi Taguchi Mitsumasa Watanabe Masayuki 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(1):341-348
Journal of Radioanalytical and Nuclear Chemistry - This study aims to demonstrate that zeolite has the potential to increase the efficiency of radiolysis treatment of aqueous organic pollutants by... 相似文献