全文获取类型
收费全文 | 1370篇 |
免费 | 48篇 |
国内免费 | 10篇 |
专业分类
化学 | 1121篇 |
晶体学 | 7篇 |
力学 | 11篇 |
数学 | 45篇 |
物理学 | 244篇 |
出版年
2023年 | 9篇 |
2022年 | 14篇 |
2021年 | 20篇 |
2020年 | 39篇 |
2019年 | 39篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 24篇 |
2015年 | 34篇 |
2014年 | 37篇 |
2013年 | 53篇 |
2012年 | 72篇 |
2011年 | 86篇 |
2010年 | 38篇 |
2009年 | 41篇 |
2008年 | 82篇 |
2007年 | 68篇 |
2006年 | 63篇 |
2005年 | 67篇 |
2004年 | 53篇 |
2003年 | 41篇 |
2002年 | 45篇 |
2001年 | 23篇 |
2000年 | 28篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 22篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1967年 | 8篇 |
排序方式: 共有1428条查询结果,搜索用时 15 毫秒
941.
942.
Isao Masada Takumi Okihara Shozo Murakami Masayoshi Ohara Akiyoshi Kawaguchi Ken-Ichi Katayama 《Journal of Polymer Science.Polymer Physics》1993,31(7):843-852
Isotactic polypropylene (iPP) was crystallized from solution on a uniaxially-oriented iPP film. Small-angle x-ray scattering patterns obtained from the sample showed two perpendicularly crossed lameliae 9.3 nm thick that overgrew flat-on and edge-on on the substrate. In the through wide-angel x-ray diffraction pattern (taken with incident x-rays normal to the iPP film surface), strong hkO reflections were arranged in an hkO net pattern indicating that the a-axis of the monoclinic α unit cell was oriented parallel to the chain direction of the substrate. From this, it was concluded that the flat-on lamellae grew with the a-axis parallel to the chain axis of the substrate and with the b-axis parallel to its surface. In the edge wide-angle x-ray diffraction pattern (X-rays incident on the edge of the film), arced, strong 110 and 220 reflections from overgrown crystals were observed on the equator of the fiber pattern of the substrate. This indicated that the edge-on lamellae epitaxially grew with the c-axis aligned parallel to the chain axis of the substrate. The homoepitaxy explains the correlated growth mode between the orthogonally crossed lamellae: they grew epitaxially, the a-axis of one lamella coinciding with the c-axis of the other and the {010} planes in contact. © 1993 John Wiley & Sons, Inc. 相似文献
943.
Kenichi Yaoita Kazuhiko Tsuji Yoshinori Katayama Motoharu Imai Jian-Qiang Chen Takumi Kikegawa Osamu Shimomura 《Journal of Non》1992,150(1-3):25-28
The structure factor, S(Q), of liquid bismuth near the melting temperature at pressures up to 7.3 GPa has been measured by an energy-dispersive X-ray diffraction method, using synchrotron radiation and a cubic-type high-pressure apparatus. The structure of liquid bismuth at atmospheric pressure shows similarity to high-pressure solid phases rather than to the atmospheric-pressure phase. With increasing pressure below 7 GPa, S(Q) changes continuously, becoming simpler in form and with the first peak becoming higher. In addition, the structure factor obtained at 7.3 GPa is totally different from those at lower pressures. It has extremely sharp peaks located at regular intervals in Q. It is concluded that liquid bismuth changes its structure drastically between 6 and 7 GPa. A model for the structure of liquid bismuth above this structural change is proposed. 相似文献
944.
Takumi Noda 《The Ramanujan Journal》2007,14(3):405-410
We give a sufficient condition of bounded growth for the non-holomorphic Eisenstein series on SL
2(ℤ). The C
∞-automorphic forms of bounded growth are introduced by Sturm (Duke Math. J. 48(2), 327–350, 1981) in the study of automorphic L-functions. We also give a Laplace-Mellin transform of the Fourier coefficients of the Eisenstein series. The transformation
constructs a projection of the Eisenstein series to the space of holomorphic cusp forms.
相似文献
945.
Aiko Miyamura Ideta Gouhei Tanaka Takumi Takeuchi Kazuyuki Aihara 《Journal of Nonlinear Science》2008,18(6):593-614
For several decades, androgen suppression has been the principal modality for treatment of advanced prostate cancer. Although
the androgen deprivation is initially effective, most patients experience a relapse within several years due to the proliferation
of so-called androgen-independent tumor cells. Bruchovsky et al. suggested in animal models that intermittent androgen suppression
(IAS) can prolong the time to relapse when compared with continuous androgen suppression (CAS). Therefore, IAS has been expected
to enhance clinical efficacy in conjunction with reduction in adverse effects and improvement in quality of life of patients
during off-treatment periods. This paper presents a mathematical model that describes the growth of a prostate tumor under
IAS therapy based on monitoring of the serum prostate-specific antigen (PSA). By treating the cancer tumor as a mixed assembly
of androgen-dependent and androgen-independent cells, we investigate the difference between CAS and IAS with respect to factors
affecting an androgen-independent relapse. Numerical and bifurcation analyses show how the tumor growth and the relapse time
are influenced by the net growth rate of the androgen-independent cells, a protocol of the IAS therapy, and the mutation rate
from androgen-dependent cells to androgen-independent ones.
相似文献
相似文献
946.
The critical power of the input pulse in which spontaneous Raman scattering is not seriously disturbed by stimulated Raman scattering in a fiber optic temperature sensor has been investigated experimentally and theoretically. The critical power determines the critical distance, which is nearly equal to the distance where optical time-domain reflectometry (OTDR) signal of the stimulated Raman scattering becomes maximum. From this fact, a new method to determine the critical input power with the OTDR system has been proposed, which may be applicable to most distributed fiber optic temperature sensors. It has been determined that the critical power of the input pulse is 4 watts for an infinitely long silica fiber.Presented at the International Commission of Optics Topical Meeting, Kyoto, 1994. 相似文献
947.
High-pressure synthesis is a powerful method for the preparation of novel materials with high elastic moduli and hardness. Additionally, such materials may exhibit interesting thermal, optoelectronic, semiconducting, magnetic, or superconducting properties. We report on the new high-pressure, high-temperature synthesis of platinum carbide. The experiments were performed in a laser-heated diamond anvil cell and data were collected using the synchrotron X-ray diffraction method at pressures >75 GPa at high-temperatures. The new platinum carbide has a rock-salt type structure, with space group Fm3m and cubic symmetry. It was confirmed to remain stable to at least 120 GPa. This structure is the same as that of other metal carbides reported in previous studies. After decompression, the new high-pressure phase was recoverable at ambient pressure. The Birch-Murnaghan equation of state for this new phase was determined from the experimental unit cell parameters, with K0=301 (±15) GPa, and K′0=5.2 (±0.4). 相似文献
948.
Hitoshi Hayakawa Seiko Nan'ya Tetsuo Yamamoto Etur Maekawa Yoshio Ueno 《Journal of heterocyclic chemistry》1986,23(6):1737-1740
The 1- and 4-substituted-5H-benzo[a]phenoxazin-5-ones (substitutents: nitro, amino and acetylamino) were prepared by the condensation of o-aminophenol with 5-substituted-2,3-dichloro-1,4-naphthoquinones. The resulting compounds were subjected to reduction, acetylation and dehalogenation. 相似文献
949.
950.
A method for stabilization in development of thermoplastic film is proposed. The method is applied to an electron beam recording system and its usefulness is confirmed experimentally. By using this method, the characteristic curve of a thermoplastic film is correctly measured and a one dimensional, first-order differentiation filter of the phase hologram type is made of the film. 相似文献