全文获取类型
收费全文 | 598篇 |
免费 | 24篇 |
国内免费 | 4篇 |
专业分类
化学 | 458篇 |
晶体学 | 8篇 |
力学 | 12篇 |
数学 | 12篇 |
物理学 | 136篇 |
出版年
2023年 | 4篇 |
2021年 | 11篇 |
2020年 | 4篇 |
2019年 | 15篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 10篇 |
2014年 | 22篇 |
2013年 | 26篇 |
2012年 | 31篇 |
2011年 | 23篇 |
2010年 | 19篇 |
2009年 | 24篇 |
2008年 | 29篇 |
2007年 | 26篇 |
2006年 | 24篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 17篇 |
2000年 | 18篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有626条查询结果,搜索用时 140 毫秒
101.
Koji Nagata Tadao Nakamura Han Geurdes Josep Batle Soliman Abdalla Ahmed Farouk 《International Journal of Theoretical Physics》2018,57(6):1605-1611
We present a new method of more speedily calculating a multiplication by using the generalized Bernstein-Vazirani algorithm and many parallel quantum systems. Given the set of real values \(\{a_{1},a_{2},a_{3},\ldots ,a_{N}\}\) and a function \(g:\textbf {R}\rightarrow \{0,1\}\), we shall determine the following values \(\{g(a_{1}),g(a_{2}),g(a_{3}),\ldots , g(a_{N})\}\) simultaneously. The speed of determining the values is shown to outperform the classical case by a factor of \(N\). Next, we consider it as a number in binary representation; M1 = (g(a1),g(a2),g(a3),…,g(a N )). By using \(M\) parallel quantum systems, we have \(M\) numbers in binary representation, simultaneously. The speed of obtaining the \(M\) numbers is shown to outperform the classical case by a factor of \(M\). Finally, we calculate the product; \( M_{1}\times M_{2}\times \cdots \times M_{M}. \) The speed of obtaining the product is shown to outperform the classical case by a factor of N × M. 相似文献
102.
Shingo Kato Kakuya Kitagawa Yeonyee E. Yoon Hiroshi Nakajima Motonori Nagata Shinichi Takase Shiro Nakamori Masaaki Ito Hajime Sakuma 《Magnetic resonance imaging》2014
Purpose
The purposes of this study were to evaluate the reproducibility for measuring the cold pressor test (CPT)-induced myocardial blood flow (MBF) alteration using phase-contrast (PC) cine MRI, and to determine if this approach could detect altered MBF response to CPT in smokers.Materials and methods
After obtaining informed consent, ten healthy male non-smokers (mean age: 28 ± 5 years) and ten age-matched male smokers (smoking duration ≥ 5 years, mean age: 28 ± 3 years) were examined in this institutional review board approved study. Breath-hold PC cine MR images of the coronary sinus were obtained with a 3 T MR imager with 32 channel coils at rest and during a CPT performed after immersing one foot in ice water. MBF was calculated as coronary sinus flow divided by the left ventricular (LV) mass which was given as a total LV myocardial volume measured on cine MRI multiplied by the specific gravity (1.05 g/mL).Results
In non-smokers, MBF was 0.86 ± 0.25 mL/min/g at rest, with a significant increase to 1.20 ± 0.36 mL/min/g seen during CPT (percentage change of MBF (?MBF (%)); 39.2% ± 14.4%, p < 0.001). Inter-study reproducibility for ?MBF (%) measurements by different MR technologist was good, as indicated by the intraclass correlation coefficient of 0.93 and reproducibility coefficient of 10.5%. There was no significant difference between smokers and non-smokers for resting MBF (0.85 ± 0.32 mL/min/g, p = 0.91). However, ?MBF (%) in smokers was significantly reduced (-4.0 ± 32.2% vs. 39.2 ± 14.4%, p = 0.011).Conclusion
PC cine MRI can be used to reproducibly quantify MBF response to CPT and to detect impaired flow response in smokers. This MR approach may be useful for monitoring the sequential change of coronary blood flow in various potentially pathologic conditions and for investigating its relationship with cardiovascular risk. 相似文献103.
104.
105.
Fuchs A Steinbrecher T Mommer MS Nagata Y Elstner M Lennartz C 《Physical chemistry chemical physics : PCCP》2012,14(12):4259-4270
In order to determine the molecular origin of the difference in electron and hole mobilities of amorphous thin films of Alq(3) (meridional Alq(3) (tris(8-hydroxyquinoline) aluminium)) we performed multiscale simulations covering quantum mechanics, molecular mechanics and lattice models. The study includes realistic disordered morphologies, polarized site energies to describe diagonal disorder, quantum chemically calculated transfer integrals for the off-diagonal disorder, inner sphere reorganization energies and an approximative scheme for outer sphere reorganization energies. Intermolecular transfer rates were calculated via Marcus-theory and mobilities were simulated via kinetic Monte Carlo simulations and by a Master Equation approach. The difference in electron and hole mobility originates from the different localization of charge density in the radical anion (more delocalized) compared to the radical cation (more confined). This results in higher diagonal disorder for holes and less favourable overlap properties for the hole transfer integrals leading to an overall higher electron mobility. 相似文献
106.
The fragment molecular orbital (FMO) method makes possible nearly linear scaling calculations of large molecular systems, such as water clusters, proteins and DNA. In particular, FMO has been widely used in biochemical applications involving protein-ligand binding and drug design. The method has been efficiently parallelized suitable for petascale computing. Many commonly used wave functions and solvent models have been interfaced with FMO. We review the historical background of FMO, and summarize its method development and applications. 相似文献
107.
Nonoyama T Kinoshita T Higuchi M Nagata K Tanaka M Sato K Kato K 《Journal of the American Chemical Society》2012,134(21):8841-8847
Hydroxyapatite is mineralized along the long axis of collagen fiber during osteogenesis. Mimicking such biomineralization has great potential to control inorganic structures and is fast becoming an important next-generation inorganic synthesis method. Inorganic matter synthesized by biomineralization can have beautiful and functional structures that cannot be created artificially. In this study, we applied biomineralization to the synthesis of the only photocatalyst in practical use today, titanium dioxide (TiO(2)). The photocatalytic activity of TiO(2) mainly relates to three properties: morphology, crystal phase, and light-use efficiency. To optimize TiO(2) morphology, we used a simple sequential peptide as an organic template. TiO(2) mineralized by a β-sheet peptide nanofiber template forms fiber-like shapes that are not observed for mineralization by peptides in the shape of random coils. To optimize TiO(2) crystal phase, we mineralized TiO(2) with the template at 400 °C to transform it into the rutile phase and at 700 °C to transform it into a mixed phase of anatase and rutile. To optimize light-use efficiency, we introduced nitrogen atoms of the peptide into the TiO(2) structure as doped elemental material during sintering. Thus, this biomineralization method enables control of inorganic morphology, crystal phase, and light-use efficiency in a single process. 相似文献
108.
Shigeki Ohsugi Yoshio Kitaoka Masaki Azuma Yoshie Fujishiro Mikio Takano Takashi Nagata Hirokazu Fujino Jun Akimitsu 《Hyperfine Interactions》2001,133(1-4):157-162
Cu nuclear magnetic resonance (NMR) spectra of impurities (Zn, Ni, and La)-doped spin-1/2 Heisenberg ladder compounds SrCu2O3 (Sr123) are broadened with Curie-like temperature (T) dependence. The spectra have been successfully fit by using a quasi-one-dimensional (Q1D) staggered polarization (SP) model. Such a SP has also revealed in Cu NMR measurements of Sr14–x
Ca
x
Cu24O41 (Cax) with hole-doped ladders. The origin of possible 3D antiferromagnetic (AF) long-range ordering in (Zn and Ni)-doped Sr123 and Cax around x=12 at low T is considered to be similar. Once unpaired spins S
0's are induced and 3D interlayer interaction occurs, the localized spins couple in the whole system. 相似文献
109.
Yoshiyuki Yokogawa Kaori Nishizawa Fukue Nagata Tetsuya Kameyama 《Journal of Sol-Gel Science and Technology》2001,21(1-2):105-113
Calcium phosphate coating over phosphorylated derivatives of chitin/chitosan material was produced by a process based on phosphorylation, Ca(OH)2 treatment and SBF (simulated body fluid solution) immersion. Chitin/chitosan phosphorylated using urea and H3PO4 and then soaked in saturated Ca(OH)2 solution at ambient temperature, which lead to the formation of thin coatings formed by partial hydrolysis of the PO4 functionalities, were found to stimulate the growth of a calcium phosphate coating on their surfaces after soaking in 1.5 × SBF solution for as little as one day. The Ca(OH)2 treatment facilitates the formation of a calcium phosphate precursor over the phosphorylated chitin/chitosan, which in turn encourages the growth of a calcium deficient apatite coating over the surface upon immersion in SBF solution. The bio-compatibility of calcium phosphate compound—chitin/chitosan composite materials was evaluated by cell culture test using L-929 cells. The initial anchoring ratio and the adhesive strength of L-929 cells for composites was higher than that for the polystyrene disk (LUX, control). The results of in-vitro evaluation suggested that the calcium phosphate—chitin/chitosan composite materials were suitable for cell carrier materials. 相似文献
110.
Isanu Nagata Kazuhiro Tamura Kaoru Tada Fumihiro Nishikawa 《Journal of solution chemistry》2000,29(9):815-835
An association model is presented to describe vapor–liquid equilibria,liquid–liquid equilibria, and excess enthalpies of binary and ternary liquid solutionscontaining alcohols, aniline, and/or acetonitrile using the concepts of linearself-association of associated components and of solvation between unlike molecules.Calculated results also show that the model works well in representing thethermodynamic properties for alcohol + aniline, alcohol + acetonitrile, andalcohol + alcohol mixtures. 相似文献