全文获取类型
收费全文 | 1050篇 |
免费 | 12篇 |
专业分类
化学 | 770篇 |
晶体学 | 10篇 |
力学 | 7篇 |
数学 | 127篇 |
物理学 | 148篇 |
出版年
2021年 | 7篇 |
2019年 | 6篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 49篇 |
2012年 | 36篇 |
2011年 | 32篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 59篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 61篇 |
2004年 | 38篇 |
2003年 | 48篇 |
2002年 | 64篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 19篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 14篇 |
1993年 | 5篇 |
1992年 | 17篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 19篇 |
1984年 | 30篇 |
1983年 | 11篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1968年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有1062条查询结果,搜索用时 15 毫秒
991.
We report on the spectroscopy of the 5s(2) 1S0(F=9/2)-->5s5p 3P0(F=9/2) clock transition of 87Sr atoms (natural linewidth of 1 mHz) trapped in a one-dimensional optical lattice. Recoilless transitions with a linewidth of 0.7 kHz as well as the vibrational structure of the lattice potential were observed. By investigating the wavelength dependence of the carrier linewidth, we determined the magic wavelength, where the light shift in the clock transition vanishes, to be 813.5+/-0.9 nm. 相似文献
992.
An ultrastable optical clock based on neutral atoms trapped in an optical lattice is proposed. Complete control over the light shift is achieved by employing the 5s(2) 1S0-->5s5p 3P0 transition of 87Sr atoms as a "clock transition." Calculations of ac multipole polarizabilities and dipole hyperpolarizabilities for the clock transition indicate that the contribution of the higher-order light shifts can be reduced to less than 1 mHz, allowing for a projected accuracy of better than 10(-17). 相似文献
993.
Kazutaka Seo Mitsuru Hasegawa Masao Morita Hideto Yoshimura 《Physica C: Superconductivity and its Applications》1998,310(1-4):358-366
We have suggested that non-uniform currents occur due to certain design parameters, for example a combination of cabling pitches, in a previous study. In the present study, we evaluate the occurrences of non-uniform current distributions in terms of design parameters, i.e., the combination of cabling pitches, winding methods (solenoidal and pancake winding) and cross-sectional shape of the cable by numerical analyses. Finally, some basic design concepts to solve this problem are proposed. 相似文献
994.
995.
Masao Tanaka 《Annals of the Institute of Statistical Mathematics》1961,13(1):201-215
Summary The length of the confidence interval which is constructed by one stage sampling is a random variable, whereas we can construct
a confidence interval of given length and of given confidence coefficient by a sequential sampling. Of cource, the sample
size required by this method is a random variable. This type of problem has already been discussed in several papers when
the population is normal (see references [2], [3], [4]). In this paper we shall discuss this subject in the binomial and Poisson
cases. 相似文献
996.
Takahiro Watanabe Hideyuki Nonoyama Masao Mori 《International Journal of Game Theory》1994,23(3):237-260
We formulate a model of a parimutuel system which considers a horse race with two horses. In our model, the raceholder offers a rate of his total betting revenue in the first stage. In the second stage each bettor simultaneously decides whether he bets one unit of money on one horse or he withdraws, according to his win predictions for each horse. We assume that all bettor's predictions are different and are common knowledge. We define some types of equilibria in the second stage game and give necessary and sufficient conditions for their existence. One equilibrium is a selected as a solution for the second stage game. We also define a solution for the whole game by using this result. Finally, we analyze the relation between the solution and variance for the bettor predictions.We thank to Prof. Okada, A. and Ikebe, Y. for helpful discussions. Special thanks are due to an anonymous referee for very grateful comments. 相似文献
997.
Upon irradiation a homologous series of certain phthalimides (-) possessing a terminal sulfide function in their N-poly-ether side chain undergo regioselective remote photocyclization affording seven to fifteen-membered crown ether analogs (-) in moderate yields. 相似文献
998.
Nobukimi Ohashi Masao Kakimoto Shuji Saito Eizi Hirota 《Journal of Molecular Spectroscopy》1980,84(1):204-224
The vibronic transition (16 370 to 16 425 cm?1) of the DSO radical in studied by Doppler-limited dye laser excitation spectroscopy. DSO is produced in a flow system by reacting the products of a microwave discharge in O2 with D2S. About 637 observed lines are assigned to 987 transitions of the 19 subbands: K′a ← K″a = 6 ← 5, 5 ← 4, 4 ← 3, 3 ← 2, 2 ← 1, 1 ← 0, 0 ← 1, 1 ← 2, 2 ← 3, 3 ← 4, 0 ← 0, 1 ← 1, 2 ← 2, 3 ← 3, 4 ← 4, 3 ← 1, 2 ← 0, 0 ← 2, and 1 ← 3. They are analyzed to determine rotational constants, centrifugal distortion constants, and spin-rotation constants for both the ground and the excited electronic states. The band origin obtained is 16 413.874 (2.5σ = 0.002) cm?1. The rotational constants determined are combined with the previous result on HSO (M. Kakimoto et al., J. Mol. Spectrosc.80, 334–350 (1980)) to calculate the structural parameters for this radical in both the states: , , and ∠HSO = 106.6(5)° for the state, and , , and ∠HSO = 95.7(21)° for the state, where values in parentheses denote 2.5σ. 相似文献
999.
We studied the image deformation due to the surface inclination of objects in photon scanning tunneling microscopes (PSTM). A novel collection mode PSTM with two light sources is proposed to reduce the deformation and experimental results show that the PSTM system is effective. 相似文献
1000.
Stereo-controlled synthesis of (±)-thienamycin intermediates which have the correct relative configurations at three chiral centers is reported. 相似文献