全文获取类型
收费全文 | 698篇 |
免费 | 43篇 |
国内免费 | 3篇 |
专业分类
化学 | 527篇 |
晶体学 | 15篇 |
力学 | 3篇 |
数学 | 43篇 |
物理学 | 156篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 18篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 22篇 |
2013年 | 44篇 |
2012年 | 62篇 |
2011年 | 70篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 35篇 |
2005年 | 32篇 |
2004年 | 37篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 8篇 |
1972年 | 7篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有744条查询结果,搜索用时 31 毫秒
651.
Sakurai S Nishino H Futaba DN Yasuda S Yamada T Maigne A Matsuo Y Nakamura E Yumura M Hata K 《Journal of the American Chemical Society》2012,134(4):2148-2153
Here we show that essentially any Fe compounds spanning Fe salts, nanoparticles, and buckyferrocene could serve as catalysts for single-walled carbon nanotube (SWNT) forest growth when supported on AlO(x) and annealed in hydrogen. This observation was explained by subsurface diffusion of Fe atoms into the AlO(x) support induced by hydrogen annealing where most of the deposited Fe left the surface and the remaining Fe atoms reconfigured into small nanoparticles suitable for SWNT growth. Interestingly, the average diameters of the SWNTs grown from all iron compounds studied were nearly identical (2.8-3.1 nm). We interpret that the offsetting effects of Ostwald ripening and subsurface diffusion resulted in the ability to grow SWNT forests with similar average diameters regardless of the initial Fe catalyst. 相似文献
652.
Wang P Minegishi T Ma G Takanabe K Satou Y Maekawa S Kobori Y Kubota J Domen K 《Journal of the American Chemical Society》2012,134(5):2469-2472
Direct photoelectrochemical conversion of toluene (TL) to methylcyclohexane (MC) with water has been examined as an organic hydride conversion using light irradiation. The production of MC from TL was observed on Pt/CdS/Cu(2)ZnSnS(4)/Mo photoelectrodes with anion-type ionomer membrane assemblies. A cathodic photocurrent was observed below 0.7 V vs RHE (V(RHE)) in 0.1 M Na(2)SO(4)/NaOH (pH 9.5) aqueous solution, and an apparent photocurrent density of 0.5 mA cm(-2) was obtained at 0 V(RHE) under the irradiation of a 300 W Xe lamp with a 420 nm cutoff filter. The yield of MC was measured by gas chromatography, and an 88% faradaic efficiency was estimated. This study suggests the possibility of direct energy conversion from solar energy to MC as an energy carrier of organic hydrides. 相似文献
653.
Taweewat Krajangsang Shunsuke KasashimaAswin Hongsingthong Porponth SichanugristMakoto Konagai 《Current Applied Physics》2012,12(2):515-520
Preparation of p-type hydrogenated microcrystalline silicon oxide thin films (p-μc-Si1−xOx:H) by 13.56 MHz RF-PECVD method for use as a p-layer of hetero-junction μc-Si:H solar cells is presented. We investigated effects of wide-gap p-μc-Si1−xOx:H layer on the performance of hetero-junction μc-Si:H solar cells under various light intensity. We observed that a wide-gap p-μc-Si1−xOx:H was effective in improving the open-circuit voltage (Voc) of the solar cells. We also confirmed that the Voc logarithmically increased with increasing light intensity, and the enhancement of Voc became larger with increasing band gap of p-layer. These results indicate that wide-gap p-μc-Si1−xOx:H is a promising material for use as window layer in hetero-junction μc-Si:H solar cells. 相似文献
654.
Akiko Takeda Shunsuke Taguchi Tsutomu Tanaka 《Computational Optimization and Applications》2010,47(1):1-31
Three measures of robustness (absolute robustness, deviation robustness and relative robustness), whose choice depends on
the goals of the decision maker, have been proposed for uncertain optimization problems. Absolute robustness has been thoroughly
studied, whereas the others have been studied to less of a degree. 相似文献
655.
A simulator to aid in the design of nonlinear image processing filters is developed. This simulator assists the filter design by determining parameters manually by trial-and-error. The method is also useful for improving the results of the learning optimization methods. An example of the application of the technique to improve a resultant filter by a learning method of a mathematical morphological filter is shown. 相似文献
656.
An efficient algorithm based on the simulated annealing for the learning optimization of morphological filters is proposed. The learning stage is divided into two consecutive parts; the initial-learning stage finds and fixes the most important parts of the structuring elements, and the precise-learning stage determines details of the rest. This method significantly reduces the number of trials for the modification of structuring elements. The proposed algorithm is applied to the learning optimization of the bipolar morphological operation, whose optimization problem has not yet been investigated. It is shown experimentally that the algorithm optimizes the operator as efficiently as the conventional one and reduces the amount of calculation. 相似文献
657.
A simple and highly sensitive method has been developed for determining ortho-phenylphenol (OPP) in lemon rind by high-performance liquid chromatography with electrochemical detection using a microbore column (microHPLC-ECD). Based on the voltammetric behavior of OPP, microHPLC-ECD was established using a CAPCELL PAK C-18 UG 120 microbore ODS column, 17 mM acetic acid-sodium acetate buffer (pH 4.0)/acetonitrile (60/40, v/v) as a mobile phase and an applied potential at +0.9 V vs. Ag/AgCl. The current peak height was found to be linearly related to the amount of OPP injected from 3.4 pg to 1.7 ng (r > 0.999). The detection limit (S/N = 3) was 3.4 pg (20 fmol), which was 100 times greater in terms of sensitivity when compared to conventional HPLC with UV detection. Standard OPP at 0.425 ng was detected with a relative standard deviation (RSD) of 1.9% (n = 10). The OPP contents in several lemon samples were determined by the present method. The recoveries of OPP from lemon rind exceeded 98% with an RSD (n = 5) of less than 3.01%. 相似文献
658.
T Kakuda M Ono K Yamashita H Ito M Yagura Y Sawai F Morishige S Kotani O Sawada T Morishige T Fugii M Miyahata B Ushio 《Radioisotopes》1979,28(9):551-557
Using 99mTc-labeled macroaggregated albumin (99mTc-MAA), we made an examination of the cerebral blood flow distribution with various kinds of cerebrovascular diseases in 151 cases. The particle size of MAA used in this study ranged from 10 to 100 micron. Scan was performed after injection of 3 mCi of 99mTc-MAA into common carotid artery. No side effects were observed except for one case with headache. Distribution of 99mTc-MAA was found to be homogeneous in normal cerebral hemisphere but not in the lesion. Most lesion was shown as nonradioactive area. Meningioma with hypervascularity was represented as hot area. By this method cerebral infarct could be easily represented not only in main artery but also in such a very small artery as hardly detected by CAG. This method is therefore useful for detecting cerebral infarct, sequela of cerebral apoplexy, head injury and others. The dose of 99mTc-MAA used in this method is much lower compared with those of common brain scan, its excretion is speedy, and therefore internal radiation exposure is diminished. 相似文献
659.
The shear force between a glass probe and a mica surface has been investigated as a function of the relative humidity, H, and the lateral spring constant of the probe, K. It was found that the interaction length Do decreases with increasing H and exhibits a sharp drop around H=40%. With increase in K from 5 to 40 N/m, Do gradually increases, although this feature was absent when a probe with a softer tip-end was used. The latter result indicates that the shear force in an atmospheric condition is not a remote force but results from some contact between the tip and the surface. Our results that Do is independent of the oscillating amplitude and that the resonance curve of the probe is almost symmetric except in close vicinity to the surface are not in accord with the force model proposed recently, i.e., the knocking mechanism. It is proposed that the probe can vibrate even if the probe touches the surface, and that the resonance frequency increases steeply as the contact tightens. Theoretical estimation of the contribution of noncontact forces is also described.This paper was originally presented at the seventh Meeting on Near Field Optics, which was held on July 1, 1998 at Nagoya University, Nagoya, organized by Research Group on Near Field Optics, the Optical Society of Japan, an affiliate of the Japan Society of Applied Physics. 相似文献
660.
Vladimir F. Petrov Meili Duan Hiroaki Okamoto Jin Mu Yo Shimizu Shunsuke Takenaka 《Liquid crystals》2013,40(3):387-410
The effect on the physico-chemical properties of achiral liquid crystals of introducing halogen atoms into their terminal and linking groups is discussed and rationalized in terms of existing theories; a comparison is made with the corresponding hydrogenated and other well-known groups. 相似文献