全文获取类型
收费全文 | 934篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
化学 | 800篇 |
晶体学 | 9篇 |
力学 | 15篇 |
数学 | 35篇 |
物理学 | 120篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 5篇 |
2020年 | 19篇 |
2019年 | 25篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 22篇 |
2015年 | 26篇 |
2014年 | 23篇 |
2013年 | 44篇 |
2012年 | 59篇 |
2011年 | 53篇 |
2010年 | 30篇 |
2009年 | 26篇 |
2008年 | 65篇 |
2007年 | 56篇 |
2006年 | 65篇 |
2005年 | 66篇 |
2004年 | 59篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1974年 | 6篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1968年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有979条查询结果,搜索用时 46 毫秒
91.
Periodic arrays of submicron Si and Ni dots were fabricated by only irradiating a linearly polarized Nd:YAG pulsed laser beam
to Si and Ni thin films deposited on silicon dioxide (SiO2) film. The interference between an incident beam and a scattered surface wave leads to the spatial periodicity of beam energy
density distribution on the surface of the irradiated samples. A thin film was melted using a laser beam, and the molten film
was split and condensed owing to its surface tensile according to the periodic energy density distribution. Then, the fine
lines (line and space structure) were formed periodically. After the formation of fine lines, the sample was rotated by 90°,
and the laser beam was irradiated. The periodic energy density distribution was generated on the fine lines, and the lines
were split and condensed. Eventually, the periodically aligned submicron dots were fabricated on the SiO2 film.
PACS 79.20.Ds; 42.62.-b; 81.40.-z 相似文献
92.
93.
94.
95.
Prolongation of life span of stroke-prone spontaneously hypertensive rats (SHRSP) ingesting persimmon tannin 总被引:1,自引:0,他引:1
S Uchida H Ohta M Niwa A Mori G Nonaka I Nishioka M Ozaki 《Chemical & pharmaceutical bulletin》1990,38(4):1049-1052
The effects of persimmon tannin on pathophysiological changes in stroke-prone spontaneously hypertensive rats (SHRSP) were investigated. When the persimmon tannin was chronically ingested by SHRSP, the life span was significantly prolonged, yet the effect on blood pressure was slight. The incidences of brain hemorrhage and infarction were also significantly decreased by this treatment. To elucidate the mechanisms involved in these events, the effects of condensed tannins, including persimmon tannin, on free radicals and lipid peroxidation were examined in vitro. Using electron spin resonance analysis, we found that these tannins have a potent, concentration-dependent scavenging action toward active oxygen free radicals. These tannins strongly inhibited lipid peroxidation in rat brain homogenates, in a concentration-dependent manner. Persimmon tannin inhibited lipid peroxidation similarly to (-)-epigallocatechin. Persimmon tannin was 20 times more effective than alpha-tocopherol in terms of the 50%-inhibitory concentration. The radical scavenging action and inhibition of lipid peroxidation by persimmon tannin may explain, in part, the prolongation of the life span of the SHRSP ingesting persimmon tannin. 相似文献
96.
Eisuke Ohtomi Takanori Takiue Makoto Aratono Hiroki Matsubara 《Colloid and polymer science》2010,288(12-13):1333-1339
We have performed ellipsometry and surface tensiometry at tetradecyltrimethylammonium bromide (TTAB) aqueous solution surface coexisting with tetradecane lens as a function of the molality of TTAB and the temperature under atmospheric pressure. From the theoretical analysis of the coefficient of ellipticity, it was clarified that the liquid monolayer comprising the surfactant and alkane is formed at higher surfactant concentrations by the wetting transition of tetradecane lens on the aqueous solution, and the solid monolayer is formed by lowering temperature (freezing transition). The results of the surface tension measurement support the occurrence of wetting transition and the freezing transition. A phase diagram of the wetting film was constructed by ellipsometry and surface tensiometry, of which the mixed solid monolayer had never been reported before. From the thermodynamic analysis of the phase diagram, it is also demonstrated that the TTAB surface density decreases accompanied with the freezing transition, which agrees with surface densities of TTAB calculated from surface tension vs. concentration curves. 相似文献
97.
Kenshu Fujiwara Yuta Hirose Hidetoshi Kawai Takanori Suzuki 《Tetrahedron letters》2010,51(32):4263-4546
Armatol F, isolated from the red alga Chondria armata as a polyether triterpene, has a solitary oxepane (A-ring) and a fused tricyclic ether moiety (BCD-ring). The A-ring features a rare cis-relationship between the hydroxy group at the quaternary carbon C6 and the carbon chain at C7. As part of our program toward the total synthesis of armatol F, a new stereoselective method for the construction of the C6 and C7 stereocenters has been developed based on chirality-transferring Ireland-Claisen rearrangement. The A-ring skeleton has also been synthesized from the rearrangement product by a process including ring-closing olefin metathesis. 相似文献
98.
99.
Kaori Kobayashi Takanori Matsui Shozo Tsunekawa 《Journal of Molecular Spectroscopy》2011,269(2):242-247
The trans-ethyl methyl ether molecule has three low-lying torsional modes, that is, two inequivalent methyl internal rotations and an asymmetric skeletal torsion. The internal rotations of the CCH3 and OCH3 methyl rotors and the skeletal torsion correspond to the vibrational modes, ν28, ν29 and ν30 respectively. In this study, the microwave absorption spectrum in the ν28 = 1 CCH3 torsional state was analyzed for the first time. Nine hundred fifty seven lines up to J = 48 and K = 4 were assigned, and the rotational, centrifugal distortion and internal rotational tunneling parameters were determined with the use of a tunneling matrix formalism. By combining the present results on the ν28 = 1 torsional state with those for the ν30 = 1 skeletal torsional state and the ν29 = 1 OCH3 torsional state, torsional couplings are estimated in order to understand quantitatively the inverted A/E sequence patterns observed for those three excited torsional states. 相似文献
100.
Yasuko Ishizuka Hiroshi Nakanishi Takanori Shiraishi Yasuo Kogure Shoichi Kobayashi 《Journal of carbohydrate chemistry》2013,32(4):583-592
ABSTRACT 1H NMR spectra of some oligosaccharide substituted cyclodextrins composed of only α-D-glucose units are analysed. Chemical shifts of protons of each glucosyl group of the chain were determined by experiments with the HOHAHA pulse technique. In spite of the similar kinds of protons, dispersion of chemical shifts is observed. The most dispersed proton is the anomeric proton, and the largest change in the chemical shifts is 0.5 ppm. 相似文献