全文获取类型
收费全文 | 2824篇 |
免费 | 58篇 |
国内免费 | 14篇 |
专业分类
化学 | 2071篇 |
晶体学 | 41篇 |
力学 | 42篇 |
数学 | 164篇 |
物理学 | 578篇 |
出版年
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 19篇 |
2020年 | 15篇 |
2019年 | 35篇 |
2017年 | 19篇 |
2016年 | 37篇 |
2015年 | 32篇 |
2014年 | 55篇 |
2013年 | 172篇 |
2012年 | 112篇 |
2011年 | 127篇 |
2010年 | 70篇 |
2009年 | 94篇 |
2008年 | 154篇 |
2007年 | 146篇 |
2006年 | 151篇 |
2005年 | 141篇 |
2004年 | 126篇 |
2003年 | 124篇 |
2002年 | 123篇 |
2001年 | 51篇 |
2000年 | 76篇 |
1999年 | 51篇 |
1998年 | 38篇 |
1997年 | 33篇 |
1996年 | 37篇 |
1995年 | 21篇 |
1994年 | 42篇 |
1993年 | 25篇 |
1992年 | 50篇 |
1991年 | 29篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 31篇 |
1987年 | 36篇 |
1986年 | 26篇 |
1985年 | 56篇 |
1984年 | 43篇 |
1983年 | 27篇 |
1982年 | 44篇 |
1981年 | 49篇 |
1980年 | 32篇 |
1979年 | 46篇 |
1978年 | 33篇 |
1977年 | 24篇 |
1976年 | 27篇 |
1975年 | 22篇 |
1974年 | 20篇 |
1973年 | 37篇 |
排序方式: 共有2896条查询结果,搜索用时 46 毫秒
1.
2.
3.
Hisatoyo Morinaga Natsumi Ogawa Mayu Sakamoto Hiroshi Morikawa 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2466-2473
The thiol‐ene reaction between trans‐limonene oxide (trans‐LO) and ethane‐1,2‐dithiol in the presence of triethylborane affords a bio‐based bis‐functional epoxide (bis‐trans‐LO). The crosslinking reaction of bis‐trans‐LO with branched polyethyleneimine (BPEI; Mn = 600; BPEI600) at a feed ratio of bis‐trans‐LO/BPEI600 = 57/43 (wt/wt) yields the corresponding network polymer with Td10 (10% thermal decomposition temperature) of 304.7 °C in 98% yield. In contrast, negligible amounts of network polymer are obtained by the reaction of bis‐LO (bis‐functional epoxide derived from cis and trans‐LO) and BPEI600 regardless of the feed ratio. The mechanical strengths as measured by direct tensile tests of the network polymers derived from bis‐trans‐LO and BPEI600,1800 (Mn = 600 and 1800) were approximately 16 and 11 times higher than that of bis‐LO and BPEI1800, respectively. The tensile shear strengths of the metal‐to‐metal adhesive bonds induced by bis‐trans‐LO and BPEI600,1800 were 9.5 and 14.1 MPa, respectively. DMA revealed that the storage modulus of the network polymer derived from bis‐trans‐LO and BPEI1800 in the rubber region was higher than that of the material prepared from bis‐LO and BPEI1800, indicating higher crosslink density of the bis‐trans‐LO/BPEI1800 system. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2466–2473 相似文献
4.
In this study we examined the unsteady and chaotic characteristics of the natural convection field in vertical slots at large
Prandtl number. In the computation, temperature dependence of viscosity was partially taken into consideration. As a result
we discovered that the spatial region where a significant temperature fluctuation is detected corresponds to the spatial region
where the secondary cells exist. The largest Lyapunov exponents calculated from the temperature on the center line have a
local maximum at the lower region of the enclosure when the viscosity change was considered. These characteristics agree well
with the experimental ones that have been observed by authors (Ishida, Kure and Kimoto 2001). 相似文献
5.
S. Sabchevski T. Idehara I. Ogawa M. Glyavin K. Ohashi 《International Journal of Infrared and Millimeter Waves》2002,23(5):675-692
A computer code for simulation of beam-field interaction in a resonant cavity of a gyrotron has been developed. It is based on a self-consistent, time-independent, single-mode physical model. The code has been applied to the analysis of the electrodynamical system of a novel high-harmonic gyrotron with axis-encircling beam and a permanent magnet. In this paper both the physical model and numerical techniques used are outlined. Some results of the numerical experiments are presented and discussed. 相似文献
6.
Er-Si-O crystalline compounds, which exhibit superlattice structures and sharp and strong Er-related 1.54 μm photoluminescence (PL) spectra at room temperature have been formed by self-assembling growth mechanism. Oxidation of the starting materials which have Si and Er at an atomic ratio of 2:1 are prepared and then oxidation and succeeding high-temperature annealing in Ar above 1250 °C cause a self-assembled superlattice-structured Er-Si-O crystalline compounds. The control of the ratio of Si and Er, as well as the following oxidation and annealing processes, is found to be sensitive to the crystalline properties, PL spectra and electrical properties. In this study, Er-Si-O crystalline thin films are formed on Si substrates by sol-gel and MOMBE methods, and their crystalline properties such as crystalline orientation and concentration ratio of Er, Si and O are investigated. Crystalline Er-Si-O films of high orientation are successfully grown on Si(1 0 0) and its inclined surface. The PL and excitation spectra, fluorescence decay and the electrical properties are found to be strongly related to the crystalline properties. Excess O causes a broader 1.54 μm PL spectra, slower fluorescence decay, lower carrier-mediated excitation and higher resistivity. A precise control of O is found to be necessary to grow superlattice-structured Er-Si-O compounds, which are semiconducting and are excitable via carrier-mediated excitation mechanism. 相似文献
7.
Takeshi Murashige Hideo Fujikake Hiroto Sato Hiroshi Kikuchi Taiichiro Kurita Fumio Sato 《Optical Review》2004,11(6):349-352
We have confirmed light diffraction of aligned polymer fibers obtained by a phase separation of an anisotropic-phase solution of liquid crystal and polymer. He—Ne laser light passing through the polymer fibers was scattered in the axis vertical to the fibers, and had two peaks of light intensity symmetrical to the center of the transmitting laser spot. The two peaks were found to be caused by light diffraction due to the periodic polymer-fiber dispersion because the peaks corresponded to values calculated by intervals between the fibers. The periodical fiber networks are considered to be formed by anisotropic spinodal decomposition. This effect can be used to measure the dispersion order of the polymer fibers. © 2004 The Optical Society of Japan 相似文献
8.
Yoshio Moriya Shinichi Nakata Hirotaka Morimoto Nobuaki Ogawa 《Analytical sciences》2004,20(11):1533-1536
Analysis by reflection spectrometry was performed to clarify the interfacial adsorption of protonated lipophilic tetraphenylporphyrin derivatives in a dodecane-aqueous sulfuric acid system, and to confirm the utility of partial reflection spectroscopy. Interfacial adsorption was not observed for porphyrins substituted at the 2,6 positions of meso-phenyl groups, suggesting that the substituents prevent porphyrins from forming aggregates by steric hindrance. Polymorphous J-aggregates of acid dications were produced by tetra-p-tolylporphyrin with a saturated interfacial molecular density of 1.0 x 10(-10) mol cm(-2), which could yield 48 degrees as a mean tilting angle of the pyrrole ring plane from the interface normal. Partial-reflection spectrometry can provide sensitive detection and molecular orientation analysis of interfacial adsorbates. 相似文献
9.
T. Ishii M. Asai A. Makishima I. Hossain P. Kleinheinz M. Ogawa M. Matsuda S. Ichikawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):15-19
Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T
1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the
doubly magic 68Ni and its neighbor 69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
10.
I. Ogawa Y. Miyake T. Idehara S. Sabchevski 《International Journal of Infrared and Millimeter Waves》2002,23(1):1-19
A novel focusing mirror based on the shifting of the beam phase according to the Gaussian beam optics enabled us to realize a focusing elements with different focal lengths in different directions and to convert the gyrotron output into a Gaussian-like beam. In this paper, we compare the quality of beams produced by the new system (which includes novel mirrors) and a conventional system consisting of a quasi-optical antenna, an ellipsoidal mirror and two parabolic cylinder mirrors. 相似文献