全文获取类型
收费全文 | 309篇 |
免费 | 6篇 |
专业分类
化学 | 211篇 |
晶体学 | 8篇 |
力学 | 3篇 |
数学 | 15篇 |
物理学 | 78篇 |
出版年
2022年 | 5篇 |
2021年 | 2篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 30篇 |
2012年 | 16篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 15篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 22篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有315条查询结果,搜索用时 31 毫秒
101.
102.
103.
Shuji Ebisu Yuji Iijima Taku Iwasa Shoichi Nagata 《Journal of Physics and Chemistry of Solids》2004,65(6):1113-1120
Magnetic susceptibility and electrical resistivity of α-Gd2S3 with an orthorhombic structure (space group: Pnma) have been measured for powder and single-crystal samples. While the magnetic susceptibility of powder sample exhibits a broad peak having a maximum at 4.2 K, the susceptibility for a single crystal with an applied magnetic field along the b-axis demonstrates a sharp drop below 10 K. Nevertheless, the susceptibility with the field perpendicular to the b-axis keeps increasing with decreasing temperature even below 10 K. The electrical resistivity ρ for the powder sample of 4.2×103 Ω cm around room temperature increases with decreasing temperature and shows a slight discontinuity at about 65 K. In both regions above and below 65 K, is proportional to T−1/4 with respective coefficients, which is associated with Mott variable-range hopping conductivity. The resistivity of a single crystal along the b-axis is considerably smaller than the value for the powder sample as 0.35 Ω cm at room temperature, and its temperature dependence is fairly weak. While cooling, the resistivity first decreases down to 240 K and then keeps the value independent of the temperature down to 140 K, and subsequently rises gently below 140 K. 相似文献
104.
We present the first observation of stochastic resonance (SR) in the human brain's visual processing area. The novel experimental protocol is to stimulate the right eye with a subthreshold periodic optical signal and the left eye with a noisy one. The stimuli bypass sensory organs and are mixed in the visual cortex. With many noise sources present in the brain, higher brain functions, e.g., perception and cognition, may exploit SR. 相似文献
105.
N. Fujima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):185-188
The non-collinearity of magnetic moments of pentagonal bipyramid Cr7, Mn7 and Fe7 clusters is discussed. The magnetic moments are calculated by the discrete variational non-collinear spin-density functional
method. For the Cr7 cluster, a coplanar magnetic arrangement appears at the large interatomic distance. With decreasing the interatomic distance,
the coplanar arrangement changes to the parallel arrangement with a small absolute magnetic moment. For the Mn7 cluster, the magnetic arrangement changes from coplanar to antiparallel with decreasing the interatomic distance. Also for
the Fe7 cluster, some coplanar magnetic moments appear at the interatomic distance of 2.23 ?. In these coplanar magnetic arrangements,
the magnetic moment at the basal site of the pentagon rotates with a step of 144 degrees for the Cr7 clusters and 72 degrees for the Mn7 and Fe7 clusters.
Received 30 November 2000 相似文献
106.
Single crystals of a sulphospinel CuIr2S4 have been grown from bismuth solution by a slow cooling method for the first time. The grown crystals have a maximum edge of about 1 mm in size and a mirror-like shining surface. Optimum growth conditions are fairly strict. The specific weight of starting materials for the crystal growth is found to be 0.30 g of CuIr2S4 and 10.0 g of Bi in order to obtain good quality crystals. The starting and finishing temperatures for the slow cooling step in the temperature control are 1000 and 500°C. The pertinent cooling rate is 2°C/h. Since the volume of bismuth itself expands in the transition from liquid phase to solid phase, a simple method of separation of the grown crystals from the liquid solution will be proposed for avoiding the mechanical damages to the grown crystals. The single crystals have the normal-spinel structure of the lattice constant a=9.849 Å at room temperature. A step-like anomaly in the susceptibility of the single crystals, corresponding to the metal–insulator transition in the resistivity, occurs much sharply than in the powder specimen. 相似文献
107.
Abstract Time-of-flight method of neutron diffraction is applied for materials under high pressure and low temperature. Extra-scattering from the pressure cell is reduced by geometrical design and by shielding with boron-plastics. Temperature is controled by adjusting the supply of liquid nitrogen: Successive transformations with pressure are observed in heavy ice. 相似文献
108.
A non-contact measuring technique of ultrasonic waves velocity is proposed, in which Rayleigh waves are detected by a laser
Doppler velocimeter and the velocity is measured precisely by means of a sing-around unit and a digital oscilloscope. With
the proposed technique, the acoustoelastic coefficient of Rayleigh waves in mild steel SS41 is obtained, which is in good
agreement with that obtained by the contact method. Furthermore the non-contact technique is applied to evaluate the residual
stress in a butt-welded steel plate, the result is reasonable. 相似文献
109.
In situ observation of the optical texture, and X-ray patterns of the pressure-induced mesophase seen for 4′-n-hexadecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-16) was performed under hydrostatic pressures up to 100MPa using a polarizing optical microscope equipped with a high pressure hot stage and a wide angle X-ray diffractometer equipped with a high pressure vessel respectively. It was found that the pressure-induced mesophase (hereafter refered to as ‘X’) appeared at pressures above 60 MPa, and exhibits a birefringent broken-fan or a sand-like texture that remain unaltered in the SmC phase. The POM-transmitted light intensity curve measured on heating clearly showed the Cr4 → Cr1 → SmC → ‘X’ → SmA → I transition sequence at 80 MPa. The optical texture and the POM-transmitted light intensity measured during a pressure cycle at 185°C showed a reversible change between the cubic and ‘X’ phases. The WAXD pattern of the ‘X’ phase showed a spot-like pattern, suggesting no layered structure for this phase, and also revealed a substantial decrease in the d-spacing of the low angle reflection at 80 and 100 MPa, compared with the d-spacings of the (0 0 1) reflection of the SmC phase and also the (2 1 1) reflection of the cubic phase. It is concluded from these data that the ‘X’ phase is a birefringent hexagonal columnar phase. 相似文献
110.
Radiation-Induced Addition Reaction of Ethyl Mercaptan and Carbon Tetrachloride to 1,2-Polybutadiene
γ-Ray-induced addition reactions of syndiotactic 1,2-polybuta-diene film with various compounds were carried out at room temperature. The weight of the film markedly increased when ethyl mercaptan was used. In the reaction with ethyl mercaptan, only addition took place without crosslinking. The addition of ethyl mercaptan to the vinyl group of syndiotactic 1,2-poly-butadiene followed anti-Markownikoff rule, and gave a 1:1 addition product. The rate of addition increased as the crys-tallinity of syndiotactic 1,2-polybutadiene used became lower. A similar relation between the crystallinity and the rate of addition was also observed in the γ-ray-induced addition of carbon tetrachloride to syndiotactic 1,2-polybutadiene, but at the same time gelation was pronounced. When liquid 1,2-polybutadiene was used instead of syndiotactic-1,2-polybutadiene, gelation which made the polymer insoluble in carbon tetrachloride did not take place, although a crosslinking reaction was noted. The appearance of the product in this case changed from a viscous liquid to a white powder as the reaction proceeded. The addition of carbon tetrachloride to the vinyl group of liquid 1,2-polybutadiene was also of the anti-Markownikoff type. This addition was accompanied by unexpectedly large vinyl consumption. The total decrease in vinyl group was found to be much larger than the decrease in vinyl group which was brought about by the addition of carbon tetrachloride. This discrepancy was attributed to cyclization and crosslinking reactions which were ascribed to the vinyl group bound by the main chain. 相似文献