全文获取类型
收费全文 | 9174篇 |
免费 | 639篇 |
国内免费 | 429篇 |
专业分类
化学 | 5752篇 |
晶体学 | 95篇 |
力学 | 388篇 |
综合类 | 29篇 |
数学 | 1379篇 |
物理学 | 2599篇 |
出版年
2023年 | 117篇 |
2022年 | 247篇 |
2021年 | 270篇 |
2020年 | 291篇 |
2019年 | 260篇 |
2018年 | 236篇 |
2017年 | 218篇 |
2016年 | 321篇 |
2015年 | 314篇 |
2014年 | 345篇 |
2013年 | 629篇 |
2012年 | 605篇 |
2011年 | 664篇 |
2010年 | 401篇 |
2009年 | 392篇 |
2008年 | 485篇 |
2007年 | 423篇 |
2006年 | 402篇 |
2005年 | 357篇 |
2004年 | 252篇 |
2003年 | 250篇 |
2002年 | 217篇 |
2001年 | 203篇 |
2000年 | 186篇 |
1999年 | 145篇 |
1998年 | 93篇 |
1997年 | 91篇 |
1996年 | 114篇 |
1995年 | 87篇 |
1994年 | 125篇 |
1993年 | 94篇 |
1992年 | 101篇 |
1991年 | 95篇 |
1990年 | 82篇 |
1989年 | 59篇 |
1988年 | 61篇 |
1987年 | 54篇 |
1986年 | 54篇 |
1985年 | 73篇 |
1984年 | 74篇 |
1983年 | 42篇 |
1982年 | 70篇 |
1981年 | 58篇 |
1980年 | 61篇 |
1979年 | 56篇 |
1978年 | 59篇 |
1977年 | 53篇 |
1976年 | 46篇 |
1975年 | 39篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
Badro J Fiquet G Struzhkin VV Somayazulu M Mao HK Shen G Le Bihan T 《Physical review letters》2002,89(20):205504
We present a new method to separate the crystallographic and electronic phase transitions in hematite using x-ray emission spectroscopy and x-ray diffraction. Our observations, based on the behavior of a metastable high-pressure phase in the stability domain of the low-pressure phase, show that the electronic transition is preempted by the crystallographic transition. The former occurs only afterwards in the high-pressure phase, possibly as a result of a Mott transition. The idea that the electronic transition drives the transition in hematite is therefore invalidated. Such methods should help elucidate the mechanics and the driving forces behind a number of first-order high-pressure phase transitions. 相似文献
82.
The α preformation factor and penetration probability
have been analyzed for even--even nuclei of Po, Rn, Ra using
experimental released energies and α decay half-lives in the
frame of the double folding model. It is shown that N=126 is a neutron
magic number from α preformation and shell effects play
an important role in α preformation. The closer the
nucleon number is to the magic number, the more difficult α
formation in the parent nucleus is. The preformation factor can
supply information on the nuclear structure and the penetration
probability mainly determines α decay half-life. 相似文献
83.
Abstract A synchrotron X-ray diffraction study on hexagonal graphite-like boron nitride (h-BN) was performed under high pressures and temperatures. From the measured P-V-Trelation for h-BN (with a three-dimensional ordering parameter P3 = 0.9) in the temperature range from 298 to 1273 K and up to 6.7 GPa, the thermoelastic parameters are derived by fitting a modified high temperature Birch-Murnaghan equation of state. The results are: bulk modulus B0[GPa] = 27.6-0.0081(T[K]-298) and its pressure derivative B1 = 10.5 + 0.0016(T [K] - 298). These values are for samples with P3 = 0.9 and are quite different for samples with different values of the order parameter. This parameter is shown to have a leading role in the determination of the thermoelastic properties of h-BN, which explains and reconciles the differences between previous results. 相似文献
84.
85.
LiCaBO3 was synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Dy3+, Tb3+, Tm3+ and Ce3+, on thermoluminescence (TL) of LiCaBO3 phosphor was discussed. We studied the TL properties and some dosimetric characteristics of Ce3+-activated LiCaBO3 phosphor in detail. The effect of the concentration of Ce3+ on TL was investigated, the result of which showed that the optimum Ce3+ concentration was 1 mol%. The TL kinetic parameters of LiCaBO3:0.01Ce3+ were studied by computer glow curve deconvolution (CGCD) method. The three-dimensional (3D) TL emission spectra were also studied, peaking at 431 and 474 nm due to the characteristic transition of Ce3+. We also studied the linearity, annealing condition, reproducibility, fading and different heating rate of the LiCaBO3:0.01Ce3+ phosphor. 相似文献
86.
We have analyzed the constant loss contribution to the ac conductivity in the frequency range 10 Hz-1 MHz and temperatures down to 8 K, for two Li ionic conductors, one crystalline (Li(0.18)La(0.61)TiO(3)) and the other glassy (61SiO(2);35Li(2)O.3Al(2)O3.P(2)O(5)). As temperature is increased a crossover is observed from a nearly constant loss to a fractional power law frequency dependence of the ac conductivity. At any fixed frequency omega, this crossover occurs at a temperature T such that omega approximately nu(0)exp(-E(m)/k(B)T), where nu(0) is the attempt frequency and E(m) is identified with the barrier for Li+ ions to leave their wells. 相似文献
87.
Critical-point phase separation in laser ablation of conductors 总被引:1,自引:0,他引:1
Vidal F Johnston TW Laville S Barthélemy O Chaker M Le Drogoff B Margot J Sabsabi M 《Physical review letters》2001,86(12):2573-2576
Laser ablation due to an ultrashort laser pulse on a massive aluminum target was investigated by means of a one-dimensional fluid code. Clear separation between the ablated matter and the unablated target is seen to occur through spinodal decomposition involving thermodynamic instabilities near the critical point of aluminum. The code also shows that the end of the ablation process is preceded by the ejection of droplets, which form about 15% of the total ejected mass. 相似文献
88.
在线单模光纤偏振控制器研究 总被引:3,自引:6,他引:3
利用Poincare球理论首次全面分析了在线全光纤偏振控制器。结果发现该偏振器可以有八种不同路径,实现任意偏振态之间的转化,最后通过实验验证了其工作性能。 相似文献
89.
90.
Applying Kontsevich's iterated integral for tangles, we get an isotopy invariant of tangles. We give a method to compute the integral of a tangle combinatorially from modified integrals of some simple tangles. We localize the integral by moving the end points of the tangle to an extreme configuration, and modify the integral so that it is convergent. By using a similar technique, we generalize Kontsevich's invariant to a framed tangle. 相似文献