全文获取类型
收费全文 | 196篇 |
免费 | 6篇 |
国内免费 | 3篇 |
专业分类
化学 | 140篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 22篇 |
物理学 | 39篇 |
出版年
2023年 | 2篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 13篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有205条查询结果,搜索用时 15 毫秒
121.
Shunji Nomura Sueo Kawabata Hiromichi Kawai Yutaka Yamaguchi Akio Fukushima Hirokazu Takahara 《Journal of Polymer Science.Polymer Physics》1969,7(2):325-355
The mechanical anisotropy of regenerated cellulose films is investigated, first, on the basis of the theory of infinitesimal elasticity. Fairly good agreement of calculated with observed results is obtained on the basis of orthogonal anisotropy with respect to the machine direction and the transverse and thickness directions of the films. The shear modulus G23 along the film plane and the Poisson ratio v32 are 1.5 times; 102 kg/mm2 and about 0.4, respectively, in the standard dry state. Second, the mechanical anisotropy in three different dry states is analyzed in terms of the degree of biaxial orientation of two kinds of structural units, cellulose II crystallites and noncrystalline chain segments, and their mechanical anisotropy. The calculation for averaging the mechanical anisotropies of these structural units on the basis of the homogeneous strain hypothesis gives results much higher than the experimental data, whereas the calculation on the basis on the homogeneous stress hypothesis gives results rather lower than experiment. As a modification of the two extreme calculations, a different averaging gives considerably better agreement between the calculated and observed results. The mechanical anisotropy in the wet state is further analyzed primarily in terms of the degree of biaxial orientation of noncrystalline chains by a modification of Krigbaum treatment, based on application of the kinetic theory of entropy elasticity for semicrystalline polymers, to anisotropic systems. The calculation gives results, however, much lower than those obtained experimentally, unless the ratio of the end-to-end distance of the noncrystalline chain to its fully stretched length is taken as unusually large. This may be due to underestimation of the contribution of the crystalline phase to terms of the same type as appear in the Krigbaum treatment. 相似文献
122.
Shunji Nomura Nobiru Nakamura Hiromichi Kawai 《Journal of Polymer Science.Polymer Physics》1971,9(3):407-420
The orientation distribution function for noncrystalline structural units in polymer systems cannot be determined completely from any experimental source; only the second and/or fourth moments of the distribution function, i.e., the second and/or fourth orders of the generalized orientation factors Flmj, can be evaluated. It is there-fore necessary to estimate the distribution function from F2mj and F4mj. In this paper, a graphical representation of the state of orientation is first discussed in terms of plots of F40j against F20j for several types of distribution functions for uniaxial orientation. These are three types of extreme concentration of the distribution at particular polar angles θ0 given by θ0 = 0, 0<θ0<π/2, and θ0 = π/2; five types of rather realistic distributions having single maxima at θj = 0, θ0, π/2 and double maxima at θj = 0, π/2, and a single minimum at θj = θ0; and four types of more realistic distributions including Kratky's floating rod model in an affine matrix. Second, estimation of the distribution function for uniaxial orientation from F40j and F20j is discussed quantitatively in terms of the mean-square error by three approximation methods: (a) expansion of the distribution function in finite series of spherical harmonics through the fourth order, (b) approximation of the distribution function as a composite of two components, random orientation and a particular orientation distribution given by Na (cos2θj)a, Na being a constant, and (c) approximation of the distribution function by Na (cos2θj)a alone. It is concluded that when the orientation distribution is sharp, estimation by the second method of approximation gives a smaller error than the first. 相似文献
123.
Shunji Kojima C. Richard Desper Roger S. Porter 《Journal of Polymer Science.Polymer Physics》1978,16(10):1721-1728
Solid-state extrusion of high-density polyethylene (HDPE) has received considerable attention. It has been shown that extrudate may have high values of optical clarity, tensile modulus (~70 GPa = 7 × 1011 dyn/cm2), and c-axis orientation. The effects of extrusion conditions on the properties of the resultant fibers have, however, not yet been clarified. A systematic study has thus been made here to evaluate extrusion pressure, temperature, and extrusion (draw) ratio, and the molecular weight of extruded HDPE. The effects of extrusion ratio on the degree of crystallinity, melting behavior, crystal orientation, and dimensional change along the extrusion direction are reported. 相似文献
124.
The tensile properties have been evaluated for high-density solid-state polyethylene extruded to different extrusion (draw) ratios. The results are compared with measured and theoretical values on this and other polymers. An extrusion (draw) ratio and a deformation gradient are defined and discussed. The content of extended tie molecules in extruded high-density polyethylene was calculated from a model and modulus data. 相似文献
125.
Ken-Ichi Fujita Hideyuki Niwa Shunji Nomura Hiromichi Kawai 《Journal of Polymer Science.Polymer Physics》1983,21(9):1713-1743
The dynamic tensile deformation mechanism of spherulitic high-density polyethylene was investigated by dynamic x-ray diffraction at various temperatures and frequencies in order to assign the α and β mechanical dispersions explicity. The uniaxial orientation distribution function q(ζj,0) of the jth crystal plane and its dynamic response Δq′j(ζj,0) in phase with dynamic strain were observed for the (110), (200), (210) and (020) crystal planes. Then the orientation distribution function w(ζ,0,η) of crystallites (crystal grains) and its dynamic response Δw′(ζ,0,η), also in phase with the dynamic strain, were determined by a mathematical transformation procedure proposed by Roe and Krigbaum on the basis of the Legendre addition theorem. The temperature and frequency dependences of w′(ζ,0,η) were analyzed in terms of the model parameters for dynamic spherulite deformation combining affine orientation of crystal lamellae with several types of preferential reorientation of the crystal grains within the orienting lamellae. The following assignments are made: (i) The α mechanical dispersion must be assigned to the dynamic orientation dispersion of crystal grains within the crystal lamellae, involving two types of preferential rotations of the grains about their own crystal b and a axes. The rotation about the b axis is associated with lamellar detwisting, mostly in the equatorial zone of uniaxially deformed spherulites; the rotation about the a axis is associated with intralamellar shearing, mostly in the polar zone of the spherulites. Thus both rotations are intralamellar grain-boundary phenomena. (ii) The β mechanical dispersion must be assigned to the dynamic orientation dispersion of the crystal lamellae behaving as rigid bodies. It is not accompanied by reorientation of the crystal grains, but is associated with orientation dispersion of noncrystalline material between the lamellae. Thus it is an interlamellar grain-boundary phenomena. 相似文献
126.
127.
Kanungo R Chiba M Iwasa N Nishimura S Ozawa A Samanta C Suda T Suzuki T Yamaguchi T Zheng T Tanihata I 《Physical review letters》2002,88(14):142502
The longitudinal momentum (P(axially)) distributions of one- and two-neutron removal fragments ((21,22)O) of 23O from the reaction with a C target at 72 A MeV have been measured for the first time using a new direct time-of-flight method with nearly full acceptance for the breakup fragments. The unexpectedly narrow width of 21O ( 115 +/- 34 MeV/c in FWHM) is consistent with two neutrons occupying the 2s(1/2) orbital in 23O. This indicates modification of core (22O) structure for neutron halo-like sd shell nuclei near the drip line. This also suggests the lowering of the s orbital providing a justification for the N = 16 magic number. 相似文献
128.
Shunji Nomura Hiromichi Kawai Itzuro Kimura Mitzuyasu Kagiyama 《Journal of Polymer Science.Polymer Physics》1967,5(3):479-491
The relationship between the optical anisotropy of high polymeric materials in bulk and the orientation of structural units within the materials was described in general by using several types of mean values of the orientation distribution function of three Eulerian angles, i.e., the orientation factors, under some assumptions about the symmetry of the function being applicable for the most of the industrial products. A newly defined biaxial orientation factor, Fθηi = 〈sin2 θj cos 2ηj〉, where θj and ηj are the polar and azimuthal angles of the jth axis within the structural unit with respect to the bulk axes, may relate the biaxial orientation of the structural units to the dichroic orientation factors, which are measurable optical anisotropic indices of the bulk materials. Some applications of the results to the birefringence and infrared and dye dichroism are also discussed. 相似文献
129.
Yamada M Suzuki T Kanaori K Tajima K Sakamoto S Kodaki T Makino K 《Organic letters》2003,5(18):3173-3176
[reaction: see text] A gas mixture of NO and O(2) was bubbled into 2'-deoxyguanosine solution at neutral pH and 37 degrees C. A novel nitrated nucleoside was generated in the reaction mixture in addition to 8-nitroguanine, 8-nitroxanthine, 2'-deoxyxanthosine, xanthine, and guanine. The novel nucleoside was identified as N(2)-nitro-2'-deoxyguanosine by spectrometric data. 相似文献
130.
Yoshimitsu nagao Takemsa inoue Eiichi fujita Shunji Terada Motoo shiro 《Tetrahedron》1984,40(8):1215-1223
The highly selective asymmetric induction into prochiral meso compounds has been developed by utilizing a functional heterocycle, 4(R methoxycarbonyl-l,3-thiazolidine-2-thione. 相似文献