全文获取类型
收费全文 | 780篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 596篇 |
晶体学 | 15篇 |
力学 | 8篇 |
数学 | 18篇 |
物理学 | 161篇 |
出版年
2021年 | 3篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 34篇 |
2011年 | 44篇 |
2010年 | 26篇 |
2009年 | 24篇 |
2008年 | 51篇 |
2007年 | 77篇 |
2006年 | 39篇 |
2005年 | 41篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 30篇 |
2001年 | 36篇 |
2000年 | 29篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1966年 | 3篇 |
1965年 | 4篇 |
排序方式: 共有798条查询结果,搜索用时 15 毫秒
731.
Shusaku Akiba 《Applied Surface Science》2007,253(10):4512-4514
Nanoscale surface modification of silicate glasses was examined by applying nanoimprint technique using a nanostriped NiO thin film mold. The mold had the pattern composed of regularly arranged straight nanogrooves, which was formed by high-temperature annealing of the Li-doped NiO epitaxial thin film deposited on the atomically stepped sapphire (α-Al2O3 single crystal) substrate. The glass imprint was proceeded through the simple steps of heating (∼600 °C), pressing (∼1 kPa) and then cooling in air. The nanoimprinted glass surface transferred reversely from the mold exhibited the multi nanowire array having an interval of ∼80 nm, wire width of ∼70 nm, and wire height of ∼20 nm. 相似文献
732.
H Matsuda T Morikawa I Toguchida K Ninomiya M Yoshikawa 《Chemical & pharmaceutical bulletin》2001,49(12):1558-1566
A new eudesmane-type sesquiterpene, zedoarofuran, and six new guaiane- or seco-guaiane-type sesquiterpenes, 4-epicurcumenol, neocurcumenol, gajutsulactones A and B, and zedoarolides A and B, were isolated from aqueous acetone extract of Zedoariae Rhizoma together with 36 known sesquiterpenes and two diarylheptanoids. Their stereostructures were elucidated on the basis of chemical and physicochemical evidence. The effects of isolated components on nitric oxide production in lipopolysaccharide-activated mouse peritoneal macrophages were examined and 16 sesquiterpenes including gajutsulactones A and B, and bis(4-hydroxycinnamoyl)methane were found to show inhibitory activity. 相似文献
733.
We experimentally investigate the spatial and temporal properties of a nonlinear optical system composed of an optically addressed spatial light modulator and a two-dimensional optical feedback. The system property is examined using fringes with only one spatial wave vector. The fringes are spontaneously generated using a spatial frequency filter in the optical feedback. We also experimentally investigate the properties of the spatial light modulator in the system using ordinary interference fringes in order to compare with the system property. We demonstrate that the spatial frequency response of the nonlinear optical system is identical to that of the spatial light modulator. We also demonstrate the distinctive temporal behavior of diffraction lights from the fringes generated in the system. 相似文献
734.
735.
Following the elucidation of eupteleasaponins I, II, III, IV, V, and V acetate, eupteleasaponins VI, VI acetate, VII, VIII, IX, X, XI, and XII were isolated from the fresh leaves of Euptelea polyandra Sieb. et Zucc. The structures of eupteleasaponins VI-XII were determined on the basis of chemical and physicochemical evidence. 相似文献
736.
Halogen-substituent effect on the spectroscopic properties of 2-phenyl-6-dimethylaminobenzothiazoles
Rena Misawa Chihiro Matsuhashi Minoru Yamaji Toshiki Mutai Isao Yoshikawa Hirohiko Houjou Keiichi Noguchi Shojiro Maki Takashi Hirano 《Tetrahedron letters》2019,60(26):1702-1705
6-Dimethylamino-2-phenylbenzothiazole (1-H) is a push-pull benzothiazole fluorophore mimicking the firefly oxyluciferin structure. We newly prepared 7-chloro and 7-bromo derivatives of 1-H and its 4-acetyl derivative (2-H), and their spectroscopic and photophysical properties were investigated. The halogenated derivatives showed the blue-shifted electronic absorption maxima and fluorescence emission maxima compared to 1-H and 2-H, resulted from the deformations of the NMe2 groups and the electron withdrawing properties of the halogen groups. In addition, the halogen substitutions accelerate intersystem crossing by heavy atom effect, resulting in a decrease in fluorescence quantum yields. Interestingly, however, the halogenated derivatives of 2-H still showed moderate fluorescence quantum yields. The halogenation effect is one of the guides to design push-pull benzothiazole fluorophores for tuning fluorescence properties. 相似文献
737.
Takeshi Yoshikawa Nana Komoto Yoshifumi Nishimura Hiromi Nakai 《Journal of computational chemistry》2019,40(31):2778-2786
The present study implemented the divide-and-conquer time-dependent density-functional tight-binding (DC-TDDFTB) code on a graphical processing unit (GPU). The DC method, which is a linear-scaling scheme, divides a total system into several fragments. By separately solving local equations in individual fragments, the DC method could reduce slow central processing unit (CPU)-GPU memory access, as well as computational cost, and avoid shortfalls of GPU memory. Numerical applications confirmed that the present code on GPU significantly accelerated the TDDFTB calculations, while maintaining accuracy. Furthermore, the DC-TDDFTB simulation of 2-acetylindan-1,3-dione displays excited-state intramolecular proton transfer and provides reasonable absorption and fluorescence energies with the corresponding experimental values. © 2019 Wiley Periodicals, Inc. 相似文献
738.
Ultrafine poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene) (MEH-PPV)/polyvinylpyrrolidone (PVP) blend fibers with the average diameters ranging from 625 nm to 1.46 µm were prepared by electrospinning of polymer blend solutions in the mixed solvent of chlorobenzene and methanol. The average diameter of fibers was found to decrease with initial increase in the applied electrical potential and composition of MEH-PPV, reach a minimum value at an intermediate value, and increase with further increase in the applied electrical potential and composition of MEH-PPV, while it was found to decrease with increasing collection distance. PVP was easily removed from MEH-PPV/PVP fibers by the Soxhlet extraction, and after the removal of PVP at high composition of MEH-PPV, pure MEH-PPV fibers were obtained as a ribbon-like structure aligned with wrinkled surface in fiber direction. The increase in MEH-PPV composition and the removal of PVP from as-spun MEH-PPV/PVP fibers resulted in a significant blue-shift in UV-Vis absorption peak and red-shift in PL peak. 相似文献
739.
Chiaki Yoshikawa Atsushi Goto Norio Ishizuka Kazuki Nakanishi Akio Kishida Yoshinobu Tsujii Takeshi Fukuda 《Macromolecular Symposia》2007,248(1):189-198
The adsorption of proteins on poly(2-hydroxyethyl methacrylate) (PHEMA) brushes was systematically investigated from the viewpoint of the size-exclusion effect of the concentrated brushes. By use of surface-initiated atom transfer radical polymerization, well-defined, concentrated PHEMA brushes were successfully grafted on the inner surface of the silica monolithic column with meso pores of ca. 80 nm as well as a silicon wafer and a quartz crystal microbalance (QCM) chip. By eluting low-polydispersity pullulans with different molecular weight through the modified monolithic column, the concentrated PHEMA brush was characterized and demonstrated to sharply exclude solute molecules with the critical molecular size (size-exclusion limit) comparable to the distance between the nearest-neighboring graft points d. The elution behaviors of proteins with different sizes were studied with this PHEMA-grafted column: the protein sufficiently larger than the critical size was perfectly excluded from the brush layer and separated only in the size-exclusion mode by the meso pores without affinity interaction with the brush surface. Then, the irreversible adsorption of proteins on PHEMA brushes was investigated using QCM by varying graft densities (σ = 0.007, 0.06, and 0.7 chains/nm2) and protein sizes (effective diameter = 2–13 nm). A good correlation between the protein size and the graft density was observed: proteins larger than d caused no significant irreversible adsorption on the PHEMA brushes. Thus, we experimentally substantiated the postulated size-exclusion effect of the concentrated brushes and confirmed that this effect plays an important role for suppressing protein adsorption. 相似文献
740.
A. Novoselov A. Yoshikawa N. Solovieva M. Nikl 《Crystal Research and Technology》2007,42(12):1320-1323
Using the micro‐pulling‐down method, (Ce,Sr)‐doped PrAlO3 square‐shaped single crystals (4×4×12 mm) were grown. Structural parameters studied by X‐ray powder diffraction were consistent with R3m space group. Compositional homogeneity was checked with electron probe micro‐analysis and found quite uniform. Absorption spectra and luminescence characteristics under UV and X‐ray excitations were measured at room temperature with no Ce‐related emission appeared. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献