全文获取类型
收费全文 | 1029篇 |
免费 | 13篇 |
专业分类
化学 | 751篇 |
晶体学 | 10篇 |
力学 | 7篇 |
数学 | 127篇 |
物理学 | 147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 | 5篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 28篇 |
1983年 | 9篇 |
1982年 | 28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1042条查询结果,搜索用时 276 毫秒
961.
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
962.
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
963.
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
964.
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
965.
Stereo-controlled synthesis of (±)-thienamycin intermediates which have the correct relative configurations at three chiral centers is reported. 相似文献
966.
Grignard reagents react with acid chlorides in tetrahydrofuran at low temperature to produce ketones in excellent yields. The results reported here strongly indicate the importance of the solvent in Grignard reagent chemistry. 相似文献
967.
The potential dependence of surface-enhanced resonance Roman spectra of meso-tetrakis (4-sulfonatophenyl) porphine (TSPP) in 0.05 M H2SO4 reveals two electrochemical processes at a silver electrode surface. One which begins around ?0.3 V is interpreted as dissociation of aggregated TSPP to monomers. The other which occurs near ?0.4 V is ascribed to a partial Ag incorporation of TSPP molecules. 相似文献
968.
By utilizing the difference in escape length of the Auger electrons with different energies, a calculation of the in-depth distribution of atomic concentration at the surface is presented on the basis of Palmberg's physical mechanism. Experimental results on clean surfaces of Cu-Ni alloys over the entire composition region with Auger spectroscopy were performed to make the in-depth profile of surface composition caused by annealing. The alloy composition of the first atomic layer at the surface was plotted against the bulk composition, showing significant enric enrichment of Cu atoms in that layer. The results indicated that the segregation takes place in about four atomic layers at the surface. 相似文献
969.
Ukon Nagai Masao Kawai Takashi Yamada Shigeru Kuwata Hiroshi Watanabe 《Tetrahedron letters》1981,22(7):653-654
Aromatic β-amino acids were converted to the Dnp derivatives, and aliphatic ones to Dnp-pMA derivatives. The sign of the Cotton effect near 400 nm reflected the configuration at the β-position without exception. Thus, the relation seems to afford a new reliable method for determining the absolute configuration of β-amino acids. 相似文献
970.