全文获取类型
收费全文 | 1295篇 |
免费 | 41篇 |
国内免费 | 6篇 |
专业分类
化学 | 1068篇 |
晶体学 | 14篇 |
力学 | 18篇 |
数学 | 56篇 |
物理学 | 186篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 14篇 |
2020年 | 23篇 |
2019年 | 16篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 27篇 |
2013年 | 53篇 |
2012年 | 72篇 |
2011年 | 95篇 |
2010年 | 45篇 |
2009年 | 51篇 |
2008年 | 70篇 |
2007年 | 71篇 |
2006年 | 79篇 |
2005年 | 89篇 |
2004年 | 68篇 |
2003年 | 76篇 |
2002年 | 59篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 11篇 |
1998年 | 22篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有1342条查询结果,搜索用时 203 毫秒
1.
Hiroto Kudo Nobuhito Ito Keiji Nakajima Masami Ochiai Tadatomi Nishikubo 《Journal of polymer science. Part A, Polymer chemistry》2007,45(19):4421-4429
The polyaddition of fluorine‐containing bis(epoxide)s and fluorine‐containing triazine di(aryl ether)s were examined to give the corresponding fluorine‐containing poly(cyanurate)s. It was observed that the synthesized fluoropolymers had good thermal stabilities and good film‐forming properties. The glass transition temperatures (Tg's) and refractive‐indices (nD's) of synthesized polymers were determined by differential scanning calorimetry and ellipsometry, respectively, and it was found that the values of Tg's and nD's were supported by their fluorine containing ratios and skeletons. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4421–4429, 2007 相似文献
2.
3.
4.
Kenji Hara Keiji Iwahashi Satoru Takakusagi Kohei Uosaki Masaya Sawamura 《Surface science》2007,601(22):5127-5132
Functionalization of self-assembled monolayer (SAM) of alkanethiolate with metal containing unit is one of the versatile methods to obtain functional surfaces such as heterogeneous catalysts. However, organic molecules that strongly bind to transition metals at SAM terminal are limited. Recently N-heterocyclic carbenes (NHCs) such as cyclic diaminocarbenes have emerged as strongly σ-donating ligands forming a robust bond with broad spectrum of transition metals. In the present study, for the purpose of establishment of a new robust basement for heterogeneous metal catalysts, a SAM of the alkanethiolate terminated with NHC-rhodium(I) complex moiety was prepared by utilizing a newly designed disulfide molecule bearing NHC-metal complex terminals. X-ray photoelectron spectroscopy (XPS) analysis and angle resolved XPS measurement revealed successful formation of the Rh-complex-terminated SAM on a gold substrate. Infrared reflection absorption spectroscopy (IRRAS) analysis suggested that the linker methylene chains connecting the rhodium complex moiety and the gold surface are in a loosely packed structure. This unique chemical species, NHC, would be a promising candidate as a basement for the construction of functional surface. 相似文献
5.
We have proposed a mechanism of nonideality, i.e., the temperature dependence of the ideality factor, in nearly ideal Au/n-Si Schottky barriers. Because of the nature of metal-induced gap states, positively ionized defects close to the interface are considered to cause local lowering of the Schottky barrier height (SBH) due to downward bending of the energy band. These positively charged defects become neutralized in equilibrium with the Fermi level due to the band bending, when they are very close to the interface. However, because the SBH lowering disappears by the neutralization of donor, the energy level of donor with a usual energy level scheme rises above the Fermi level after the neutralization. This contradiction to the equilibrium neutralization is resolved by Si self-interstitial with a large negative-U property, which is generated by the fabrication process. The energy level of the donor estimated from the SBH lowering is in good agreement with that of theoretical calculation of Si self-interstitial. Thus, the defect is concluded to be the Si self-interstitial, which is distributed to more than 10 Å depth from the interface. 相似文献
6.
7.
The motion of a moored floating body under the action of wave forces, which is influenced by fluid forces, shape of the floating body and mooring forces, should be analysed as a complex coupled motion system. Especially under severe storm conditions or resonant motion of the floating body it is necessary to consider finite amplitude motions of the waves, the floating body and the mooring lines as well as non-linear interactions of these finite amplitude motions. The problem of a floating body has been studied on the basis of linear wave theory by many researchers. However, the finite amplitude motion under a correlated motion system has rarely been taken into account. This paper presents a numerical method for calculating the finite amplitude motion when a floating body is moored by non-linear mooring lines such as chains and cables under severe storm conditions. 相似文献
8.
Masato Shinoda 《Probability Theory and Related Fields》2003,125(3):447-456
A percolation problem on Sierpinski carpet lattices is considered. It is obtained that the critical probability of oriented percolation is equal to 1. In contrast it was already shown that the critical probability p
c
of percolation is strictly less than 1 in Kumagai [9]. This result shows a difference between fractal-like lattice and ℤ
d
lattice.
Received: 15 May 2002 / Revised version: 11 October 2002 / Published online: 21 February 2003
Mathematics Subject Classification (2000): Primary: 60K35, 82B43; Secondary: 82B26 相似文献
9.
According to the concept of the recognized visual space of illumination (RVSI) the lightness of an object surface is perceived in relation to its conceptualized size. To prove this proposition the lightness of gray test patches was judged when they were located at various positions inside an illuminated space composed of two rooms in the depth direction from a subject. No retinal image arrangement was changed in the test patch and its immediate surroundings, but the front room had walls, floors and furniture lower in lightness by the amount of N1.5 than the back room to make the RVSI of the former smaller despite the illuminance in the entire space being the same. The results showed that the apparent lightness of the patches was perceived higher by amount of about 13 in L units for the N4 test patch and about 20 for N6 when the patches were located in the front room, in accordance with the prediction. It was stressed that the experiment of lightness judgment should be conducted in a three dimensional space rather than two dimensional plane as done by several investigators. 相似文献
10.
Nahomi Sakaguchi Keiji Yamada Shuji Matsuo Taku Matsuo Hisanobu Wakita 《Research on Chemical Intermediates》2006,32(2):171-182
Surface modification of TiO2 powders with lanthanide salts (EuCl3 or YbCl3) enhanced photocatalytic decomposition of ATP. In comparison with the unmodified catalyst, a 3-fold increase in the ATP decay
rate was observed with TiO2 powders as prepared in 5 mM EuCl3 (or YbCl3) solution. The reason was ascribed to enrichment of ATP to TiO2 powder with the lanthanide ions. Evidence was obtained by adsorption experiments where ATP concentration was monitored after
dispersing TiO2 powders into the solution. The ATP molecules adsorbed faster to TiO2 powder and strongly stabilized there in the presence of Yb3+ than otherwise. 相似文献