全文获取类型
收费全文 | 650篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
化学 | 463篇 |
晶体学 | 4篇 |
力学 | 9篇 |
数学 | 29篇 |
物理学 | 179篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 23篇 |
2013年 | 23篇 |
2012年 | 32篇 |
2011年 | 30篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 28篇 |
2007年 | 25篇 |
2006年 | 21篇 |
2005年 | 27篇 |
2004年 | 31篇 |
2003年 | 19篇 |
2002年 | 22篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1997年 | 17篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 22篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 14篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1973年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有684条查询结果,搜索用时 15 毫秒
91.
Shigeru Nishiyama Yoshikazu Shizuri Daizo Imai Shosuke Yamamura Yukimasa Terada Masatake Niwa Kazuaki Kawai Hideyuki Furukawa 《Tetrahedron letters》1985,26(27):3243-3246
Isocitreoviridinol has been newly isolated from the mycelium of B. (IFO 6050) together with citreoviridinol, and their stereostructures have also been elucidated by means of chemical method: the 2,6-dioxabicyclo[3.2.1]octanes have been made, one of which is regarded as a promising synthetic intermediate of citreoviridinol. In addition, isocitreoviridinol diacetate has been derived from citreoviridin in 3 steps. 相似文献
92.
Yoshitaka Ishii Koichi Hirao Takehiko Terao Tsutomu Terauchi Makoto Oba Kozaburo Nishiyama Masatsune Kainosho 《Solid state nuclear magnetic resonance》1998,11(3-4):169-175
A solid state NMR method is presented for determination of a backbone dihedral angle φ in peptides, being based on the previously reported method, relayed anisotropy correlation (RACO) NMR [Y. Ishii et al., Chem. Phys. Lett. 256 (1996) 133]. In the present method, the
and the
dipolar tensors in the
system are two-dimensionally (2D) correlated via polarization transfer from
to
under magic angle spinning (MAS). This method was applied to N-acetyl
,
-valine, and the H–C–N–H dihedral angle was determined to be 154.0±1.4° or 206.0±1.4°, the former agreeing with the X-ray value of 154±5°. 相似文献
93.
94.
Tomihiro Nishiyama Masataka Kushiyama Etsuo Ikemoto Fukiko Yamada 《Journal of heterocyclic chemistry》1984,21(1):37-39
Two isomeric 4-methyl-6-phenyl-5,6,7,8-tetrahydro-4H-1,3,2,6-dioxathiazocine 2-oxides were prepared, and their pmr and cmr spectra were examined. From the aromatic solvent shielding values and the magnitudes of the γ shifts, the title compounds are found to exist in the trans and cis forms in solution. 相似文献
95.
N. Bräuer B. Focke B. Lehmann K. Nishiyama D. Riegel 《Zeitschrift für Physik A Hadrons and Nuclei》1971,244(4):375-382
The γ-ray angular correlation of the 9/2+, 37 μs state in81Br and of the 181 keV, 120 μs state in78Br was disturbed by nuclear magnetic resonance. Theg-factors were determined to be ¦g¦=1.297±0.015 for the 37 μs level in81Br and ¦g¦=1.025±0.003 for the 120 μs state in78Br. 相似文献
96.
Y. Kuno J. Imazato K. Nishiyama K. Nagamine T. Yamazaki K. Matsuta S. Ise Y. Nojiri T. Minamisono 《Hyperfine Interactions》1988,39(3):253-267
NMR measurements on12B nuclei implanted in a thin sheet of highly oriented pyrolytic graphite (Grafoil) have been made to study the magnitude of
the polarization of12B and its electric quadrupole coupling. The magnitude of the residual polarization of12B held in carbon material is of crucial importance to the experiment measuring the average polarization of12B produced in the muon capture by12C. It was found that the polarization of12B can be maintained at 101.0±2.2% in Grafoil under a magnetic field of 3 kG. The electric quadrupole coupling was determined
to bee
2
qQ/h=+1207.3±8.2 kHz. From the magnitude and the sign of the electric field gradienteq, the location of12B was found to be a substitutional site in the carbon lattice. The anomalous B-C bond involving thesp
2
hybrid orbitals with partially filledp
z
electrons is also discussed. 相似文献
97.
98.
T. Matsumoto H. Harano J. Nishiyama H. Matsue A. Masuda A. Uritani K. Kudo 《Radiation measurements》2010,45(10):1124-1126
We have developed a thermal neutron calibration method using a reactor produced neutron beam in JRR-3M of the Japan Atomic Energy Agency. Neutron-induced prompt gamma ray analysis has usually been performed in this beam line. Neutron energy distributions with negligible contributions from epithermal neutrons were measured by a time-of-flight method with a chopper made of 6LiF powder. The thermal neutron flux was determined by a gold foil activation method. We found that the thermal neutron beam in JRR-3M was well suited for calibration, neutron detector development or neutron dosimetry. 相似文献
99.
Yuji Utsunomiya Takashi Kajiwara Takashi Nishiyama Kunihito Nagayama Shiro Kubota 《Applied Physics A: Materials Science & Processing》2010,99(3):641-649
We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the
refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that
laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is
focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present
study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media
with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film
was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon
on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the
splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000
m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid
jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy,
and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led
to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal
behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history. 相似文献
100.
We present a model which aims at describing the morphology of colonies of Proteus mirabilis and Bacillus subtilis. Our model is based on a cellular automaton which is obtained by the adequate discretisation of a diffusion-like equation, describing the migration of the bacteria, to which we have added rules simulating the consolidation process. Our basic assumption, following the findings of the group of Chuo University, is that the migration and consolidation processes are controlled by the local density of the bacteria. We show that it is possible within our model to reproduce the morphological diagrams of both bacteria species. Moreover, we model some detailed experiments done by the Chuo University group, obtaining a fine agreement. 相似文献