全文获取类型
收费全文 | 828篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
化学 | 599篇 |
晶体学 | 12篇 |
力学 | 10篇 |
数学 | 59篇 |
物理学 | 160篇 |
出版年
2021年 | 5篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 8篇 |
2013年 | 44篇 |
2012年 | 39篇 |
2011年 | 32篇 |
2010年 | 14篇 |
2009年 | 23篇 |
2008年 | 44篇 |
2007年 | 32篇 |
2006年 | 46篇 |
2005年 | 43篇 |
2004年 | 27篇 |
2003年 | 37篇 |
2002年 | 26篇 |
2001年 | 6篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 22篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1985年 | 19篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1969年 | 5篇 |
1968年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有840条查询结果,搜索用时 0 毫秒
51.
K. Kamimura 《Letters in Mathematical Physics》1980,4(2):115-122
The relativistic string model is reformulated in terms of differential geometry. Some independent geometrical quantities are regarded as dynamical variables instead of the coordinates. In a particular gauge the fundamental equations can be linearized and solved. The solution here found is equivalent to that of light like gauge as a classical system. 相似文献
52.
53.
Elastic and inelastic scattering of 7Li by 58Ni at Elab = 14.2 and 20.3 MeV is investigated theoretically, special emphasis being laid on polarization phenomena. A parameter-independent study shows second-rank tensor interactions to be the main origin of tensor analyzing powers for both elastic and inelastic scattering. Coupled-channel (CC) calculations using cluster-folding interactions which include the tensor terms are found to be successful in reproducing the data for cross sections and vector and tensor analyzing powers, when projectile excitation effects are sufficiently taken into account. Scattering of 6Li by 58Ni at Elab = 20.0 MeV is also investigated by the CC calculation, where successes similar to the 7Li case are obtained in understanding experimental data. 相似文献
54.
Shinji Fushiya Yoshikazu Sato Shigeo Nozoe Kyosuke Nomoto Tsunematsu Takemoto Sei-ichi Takagi 《Tetrahedron letters》1980,21(32):3071-3072
A new amino acid derivative possessing an iron chelating activity was isolated from root washings of water cultured under iron deficient conditions. The structure of this compound, avenic acid A has been determined as 2(S),3′(S),3″(S)-N-[3-(3-hydroxy-3-carboxypropylamino)-3-carboxypropyl]-homoserine (1) on the basis of chemical and spectroscopic evidence. 相似文献
55.
A new synthetic approach to quinazolines bearing a carboxy group is described. Reaction of 5-carbonyl substituted 1,3,6-tri-methyluracils (I) with dimethyl acetylenedicarboxylate or electron-deficient olefines affords quinazoline derivatives (III-VI) pyrimidine(Z)-dienols (II) formed by base-catalyzed isomerization. 相似文献
56.
Katsuyuki Ogura Hiroshi Sobue Shigeo Nakamura 《Journal of Polymer Science.Polymer Physics》1973,11(10):2079-2088
The glass transition in styrene-based ionomers was investigated by means of infrared spectroscopy and differential scanning calorimetry (DSC). Transition temperatures were determined from the temperature dependence of the peak absorbances of the 1700 and 1745 cm?1 bands. These transition temperatures agreed with glass transition temperatures (Tg) determined by DSC. With increasing degree of ionization, Tg and the enthalpy ΔH of the residual intermolecular hydrogen bonding increased. The values of Tg obtained were analyzed by the theory of Fox and Loshaek for the effect of crosslinks. It is concluded that sodium ions probably from ionic domains and act as crosslinks to reinforce the residual hydrogen bonding and may increase Tg. The absorbance at 1560 cm?1 (νCOO?) did not change at Tg. This suggests that the glass transition observed here is not due to the onset of the mobility in ionic domains, as has been proposed for ethylene-based ionomers on the basis of dielectric measurements. 相似文献
57.
Excitation migration between 5D0 states of Eu3+ ions in Ca(PO3)2 glass is studied by using the technique of the selective excitation of the inhomogeneously broadened 5D0 levels. In time-resolved emission spectra for 5D0→7F1 transition after the pulse excitation due to 7F0→5D0 transition by the use of a tunable dye laser at 77°K, a subpeak is observed to appear and to grow in intensity with increasing delay time, besides the main peak excited directly by the excitation light. The observed facts are explained by considering the phonon-assisted energy transfer between 5D0 states involving an acoustic phonon. From the analysis of the results, the probability of the excitation migration due to the phonon-assisted process is estimated to be ≌ 10 A ms-1. From the theoretical consideration, the rate of the linewidth change and the probability of the excitation migration due to the resonant transfer process are obtained. These results indicate that the phonon-assisted process is more dominant than the resonant process for the excitation migration in the system studied. 相似文献
58.
Shigeo Shionoya Hiroshi Saito Eiichi Hanamura Okikazu Akimoto 《Solid State Communications》1973,12(3):223-226
Luminescence lines due to excitonic molecules are observed in CdS and CdSe. The line shape is analyzed by taking account of the broadening due to elastic collision. It is pointed out that the anisotropy of the effective hole masses makes the molecular binding energies much larger than evaluated by using the geometrical means of the hole masses. 相似文献
59.
H Kamimura H Sasaki S Kawamura M Shimizu H Matsumoto Y Kobayashi 《Journal of chromatography. A》1983,275(1):81-87
A gas chromatographic method for the quantitative determination of the alpha, beta-adrenoceptor blocker YM-09538 in urine is described. YM-09538 was extracted from alkalinized urine with ethyl acetate and converted to its cyclic methylboronate derivative. Analysis by gas chromatography using a nitrogen-sensitive detector allowed quantitation of the drug over a concentration range of 0.2-5.0 micrograms/ml. Urinary excretion of YM-09538 was determined in humans after oral administration of 50 mg. 相似文献
60.
Mori S Endo M Furukawa S Sunaoka M Nonaka H Ishii T Ikehira H 《Magnetic resonance imaging》2005,23(5):691-694
We developed a high radiation sensitive polymer gel by modifying the amounts of the gel components and the temperature for the gel preparation. We evaluated its relaxation time linearity against dose and compared the measured dose distribution with the calculated one. For the relaxation time-dose linearity, irradiations were carried out with a linear accelerator using 6 MV photons and doses ranging from 0-5.0 Gy. The relationship between dose and R(2) value (reciprocal of T(2) relaxation time) was measured and it had good linearity over a wide range (0.3-5 Gy). The measured dose distributions were in good agreement with calculated ones. Since the present gel has higher sensitivity and it is synthesized more easily at lower cost than conventional polymer gels, we expect to see improved three-dimensional (3D) dosimetry using it. 相似文献