全文获取类型
收费全文 | 3548篇 |
免费 | 79篇 |
国内免费 | 15篇 |
专业分类
化学 | 2706篇 |
晶体学 | 46篇 |
力学 | 44篇 |
数学 | 209篇 |
物理学 | 637篇 |
出版年
2022年 | 32篇 |
2021年 | 23篇 |
2020年 | 43篇 |
2019年 | 49篇 |
2018年 | 30篇 |
2017年 | 20篇 |
2016年 | 51篇 |
2015年 | 42篇 |
2014年 | 58篇 |
2013年 | 135篇 |
2012年 | 134篇 |
2011年 | 182篇 |
2010年 | 83篇 |
2009年 | 103篇 |
2008年 | 181篇 |
2007年 | 192篇 |
2006年 | 200篇 |
2005年 | 175篇 |
2004年 | 155篇 |
2003年 | 121篇 |
2002年 | 109篇 |
2001年 | 94篇 |
2000年 | 72篇 |
1999年 | 62篇 |
1998年 | 48篇 |
1997年 | 55篇 |
1996年 | 57篇 |
1995年 | 52篇 |
1994年 | 42篇 |
1993年 | 52篇 |
1992年 | 56篇 |
1991年 | 43篇 |
1990年 | 43篇 |
1989年 | 52篇 |
1988年 | 47篇 |
1987年 | 44篇 |
1986年 | 32篇 |
1985年 | 81篇 |
1984年 | 54篇 |
1983年 | 36篇 |
1982年 | 53篇 |
1981年 | 46篇 |
1980年 | 54篇 |
1979年 | 48篇 |
1978年 | 42篇 |
1977年 | 34篇 |
1976年 | 29篇 |
1975年 | 31篇 |
1974年 | 35篇 |
1973年 | 32篇 |
排序方式: 共有3642条查询结果,搜索用时 0 毫秒
1.
Surface texturing has been recognized as an effective means to improve the tribological performances of sliding surfaces. Usually, generation additional hydrodynamic pressure to increase the load carrying capacity is regarded as the most significant effect of surface texture. In the case of silicon carbide sliding against identical material in water, the experimental results indicate that surface texture is also helpful to improve the running-in progress to smooth the contact surfaces, showing another reason to result in low friction. Based on the consideration of enhancing the generation of hydrodynamic pressure and improving running-in progress, a surface texture pattern, which was combined with large (circle, 350 μm in diameter) and small (rectangular, 40 μm in length) dimples, was designed to maximize the texture effect on the load carrying capacity of SiC surfaces sliding in water. The friction coefficient of such textured surface was evaluated and compared with that of untextured and those only with large or small dimples only. The friction reduction mechanisms of the patterns with different dimples in size are discussed. 相似文献
2.
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
3.
Katsunari Inoue Kazuaki Kato Norimitsu Tohnai Mikiji Miyata 《Journal of polymer science. Part A, Polymer chemistry》2004,42(18):4648-4655
We studied simulations by computer graphics to estimate the steric mechanism of the asymmetric polymerization of prochiral diene monomers in channels of inclusion compounds of steroidal bile acids, such as deoxycholic acid (DCA) and cholic acid. We applied a hierarchization method to interpret the crystal structures of bile acids, clarifying that the chiral host molecules associated to form characteristic 21-helical assemblies with uneven surfaces. A detailed analysis of the uneven channels in a close-packing state indicated that there were many possible arrangements of the monomers in the channels. The plausible arrangements in the channel could explain a previous study, which showed that the polymerization in the DCA channel yielded chiral polymers with a predominant configuration from prochiral diene monomers, such as 2-methyl-trans-1,3-pentadiene. On the basis of such simulation studies of the arrangements of guest monomers in the channel, we examined a plausible steric mechanism for asymmetric inclusion polymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4648–4655, 2004 相似文献
4.
Seiichi Nishizawa Tomoyuki Kamaishi Tomoyuki Yokobori Ryo Kato Ying-Yu Cui Takeshi Shioya Norio Teramae 《Analytical sciences》2004,20(11):1559-1565
Facilitated SO4(2-) transfers by hydrogen bond-forming ionophores are investigated across the nitrobenzene (NB)-water interface by using polarography with a dropping electrolyte electrode. Bis-thiourea 1, alpha,alpha'-bis(N'-p-nitrophenylthioureylene)-m-xylene, is found to significantly facilitate the transfer of the highly hydrophilic SO4(2-) whereas its counterpart, N-(p-nitrophenyl)-N'-propylthiourea (ionophore 2), cannot. In contrast to the predominant formation of a 1:1 complex with SO4(2-) in the bulk NB phase, the SO4(2-) transfer assisted by 1 is indeed based on the formation of a 1:2 complex between SO4(2-) and ionophore, even under the condition of [SO4(2-)]aq > [1]org. Such an exclusive formation of the 1:2 (SO4(2-) to ionophore) complex at the NB-water interface is not observed with structurally similar bis-thiourea 3, alpha,alpha'-bis(N'-phenylthioureylene)-m-xylene, where p-nitrophenyl moietes of bis-thiourea 1 are simply replaced by phenyl groups. The facilitated transfer of SO4(2-) with bis-thiourea 1 is further compared to that of HPO4(2-) and H2PO4- across the NB-water interface, which was previously shown to be assisted by 1 through the formation of the 1:1 and 2:1 (anion to ionophore) complexes, respectively. On the basis of these examinations, unique binding behaviors of hydrogen bond-forming ionophores at the NB-water interface are discussed, with a view towards development of ionophore-based anion-selective chemical sensors. 相似文献
5.
We will discuss the Gorenstein property of the singularity which is blown down from the minimal section of a ruled surface in terms of the extension class. In the case that the base field has positive characteristic, we find a new example (3.4) of Gorenstein singularity in connection with Theorem B. 相似文献
6.
Tadao Nozawa Fumio MorimotoRikio Harazono Norimoto Nouchi 《Journal of magnetism and magnetic materials》2006
Evaporative deposition at oblique incidence is shown to enhance the magnetic anisotropy of an Fe20Ni80 magnetic film and induce magnetic anisotropy in an overlying, strongly isotropic Fe70Co30 film. This deposition method for the formation of an underlayer of several lattice parameters in thickness and semi-hard overlayer of a few thousands Angstroms in thickness achieves a significant change in the magnetization process and strong suppression of the coercive forces of Fe70Co30 in the hard magnetization direction. Soft magnetization of the Fe70Co30 overlayer is not achieved when one of the layers is deposited at oblique incidence. It is anticipated that shape magnetic anisotropy is responsible in part for the magnetic anisotropy induced in both in Fe20Ni80 under- and Fe70Co30 overlayer by oblique incidence evaporation. 相似文献
7.
8.
9.
10.
Fumio Hiai 《Linear and Multilinear Algebra》1994,36(4):239-249
The equality cases in several matrix norm (trace) inequalities are characterized. Norm inequalities of Golden-Thompson type and of its complement type are treated as well as a logarithmic trace inequality and norm inequalities for matrix exponentials. 相似文献