全文获取类型
收费全文 | 265篇 |
免费 | 11篇 |
国内免费 | 6篇 |
专业分类
化学 | 169篇 |
晶体学 | 1篇 |
力学 | 12篇 |
数学 | 46篇 |
物理学 | 54篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 23篇 |
2012年 | 24篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有282条查询结果,搜索用时 31 毫秒
121.
离子色谱-脉冲安培检测器分析饮料中单糖和二糖 总被引:3,自引:0,他引:3
建立了等度离子色谱-脉冲安培检测分析饮料中葡萄糖、果糖、蔗糖和乳糖的方法。采用CarboPacPA10分离柱对分离条件进行了优化,确定柱温为30℃、淋洗液为52mmol.L-1的NaOH溶液,在0.10—20.0mg.L-1范围内葡萄糖、果糖、蔗糖、乳糖呈良好线性,回收率分别为93.3%—112.5%、102.2%—111.6%、96.8%—99.6%、88.0%—102.6%,检出限分别为0.8、4.0、5.0、10.0mg.kg-1,精密度分别为0.18%—1.21%、0.53%—3.76%、0.65%—2.54%、1.65%—5.11%。检测了饮料中的单糖和二糖,效果良好。 相似文献
122.
Wook Jae Yoo Dong Hyun Cho Kyoung Won Jang Sang Hun Shin Jeong Ki Seo Soon-Cheol Chung Bongsoo Lee Byung Gi Park Joo Hyun Moon Young-Ho Cho Sin Kim 《Optical Review》2009,16(3):387-391
In this study, we have fabricated non-contact temperature sensor using an infrared optical fiber for measuring temperature
distributions during radiofrequency ablation. We have measured an infrared radiation, which is transferred by a silver halide
optical fiber from the multi-points on the water around inserted electrode, using a thermopile sensor and the output voltages
of a thermopile sensor are compared with those of the thermocouple recorder. Also, the relationship between the temperatures
and the output voltages of a thermopile sensor at the measuring points is determined to obtain the temperature distribution.
The measurable temperature range of a fiber-optic non-contact temperature sensor is from 37 to 80 °C. 相似文献
123.
1.IntroductionInthispaper,westudytheFredholmintegro-differentialequationbythewaveletmethod.Theapplicationsoftheequationinimagerestorationcouldbefoundin[101.ForthehistoryofnumericalmethodsfortheFredholmintegro-differentialequations,wereferto[4].FOllow... 相似文献
124.
<正>Mechanics plays a crucial role in a diversity of biological processes at different length(from molecules,cells,tissues,organs to organisms)and time scales.As a rapidly growing field across the interfaces of mechanics,biology,and medical engineering,mechanobiology aims to identify the mechanical and biological responses of cells and tissues of 相似文献
125.
Yee Sin Ang J. C. Cao Chao Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(2):1-7
We explain how specific dynamical properties give rise to the limit distribution of sums of deterministic variables at the transition to chaos via the period-doubling route. We study the sums of successive positions generated by an ensemble of initial conditions uniformly distributed in the entire phase space of a unimodal map as represented by the logistic map. We find that these sums acquire their salient, multiscale, features from the repellor preimage structure that dominates the dynamics toward the attractors along the period-doubling cascade. And we explain how these properties transmit from the sums to their distribution. Specifically, we show how the stationary distribution of sums of positions at the Feigebaum point is built up from those associated with the supercycle attractors forming a hierarchical structure with multifractal and discrete scale invariance properties. 相似文献
126.
We have examined the electroweak radiative corrections in the LEP precision data in view of the new measurements of MW and mt as well as the recent progress in the higher order radiative corrections. From the minimal L2-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program), we predict that MW=80.29(4)(2)rGeV where the first error is due to the uncertainty in the fitted mt for a fixed mH and the second error comes from the mH in the range 60rGeV, which is to be compared with the current world average MW=80.23(18)rGeV. The current world average value of MW and the 1994 LEP data definitely favor nonvanishing electroweak radiative corrections and are consistent with a heavy mt as measured by the recent CDF report but with a heavy Higgs scalar of about 400rGeV within the context of the minimal standard model. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling !s(MZ) and !(MZ) are also studied carefully. In addition we discuss how the future precision measurements of MW can provide a decisive test for the standard model with radiative corrections and give a profound implication for the measurement of t-quark and Higgs masses. 相似文献
127.
D. S. Kim M. K. Kang T. J. Kim S. W. Lee J. K. Kang N. J. Kim A. S. Kim H. R. Cho M. K. Park Y. K. Sin 《Optical and Quantum Electronics》1995,27(5):459-464
Data are presented on InGaAsP/InP planar buried heterostructure (PBH) distributed feedback (DFB) lasers operating at 1.3 m. A four-step MOVPE process and holographic lithography are employed to fabricate these lasers. The CW laser threshold and the slope efficiency from these lasers are 9 mA and 0.23 mW mA-1 per facet at room temperature. Single-longitudinal-mode operation with side-mode suppression of more than 35 dB is obtained at 5 mW. 相似文献
128.
The acrylamide sol-gel processes becomes a fast, cheap, reproducible and easy to scale-up chemical way for obtaining nanopowders of BaZrO3, which can be used for crucible sintering or many electronic applications. This synthesis method allows performing 100 g of high purity nanosized particles, in one run, with simple laboratory equipment and using low cost raw materials. Temperature synthesis and atmosphere conditions are studied for obtaining best powders. They are sintered at 1450°C to full density, then at much lower temperature than previously reported, making possible the crucible fabrication of BaZrO3 for many laboratories. 相似文献
129.
A new type of one-dimensional cyanide-bridged Cu(II)--Mo(V) bimetallic assembly, [Cu(cyclam)](3)[Mo(CN)(8)](2)x5H(2)O (cyclam = 1,4,8,11-tetraazacyclotetradecane), was prepared by self-assembling Mo(CN)(8)(3)(-) and Cu(cyclam)(2+) ions in a 2:3 stoichiometric ratio. The overall molecular view is delineated as a novel rope-ladder chain structure. It displays a dominant ferromagnetic behavior within a pentanuclear Cu(3)Mo(2) unit (J(p) = 3.88 cm(-)(1)). Interunit ferromagnetic interactions (J(c) = -0.03 cm(-)(1)) through a longer magnetic pathway of Cu--Mo and weak antiferromagnetic couplings (zJ' = -0.46 cm(-)(1)) resulting from interchain interactions are obtained. 相似文献
130.
Structural and magnetic properties were studied on La1−xMnO3±δ nanocrystalline powders exhibiting different La/Mn ratios. These compounds were prepared using a gel combustion method based on a cation solution soaking by acrylamide polymerization. Structural properties were studied both by transmission electron microscopy and X-ray diffraction (XRD). Complete chemical composition analyses were performed by induced coupled plasma spectroscopy and by iodometric titration. Proportions of parasitic phases in samples, as La2O3 or Mn3O4, and actual compositions of La1−xMnO3±δ phases were then determined from refinements of XRD data and sample chemical compositions. As a result, perovskite structure is not any more stable for La/Mn<0.9 as it decomposes into a mixing of La0.9MnO3 and of Mn3O4 phases, in agreement with results on thermodynamic equilibrium in the La-Mn-O phase diagram. For La/Mn>0.9, a high oxygen excess is observed and leads to consider the creation of vacancies on both lanthanum and manganese sites, whose concentrations are evaluated. Magnetic properties agree well with the proposed structures and sample compositions since for La/Mn<0.9, for which a La0.9MnO3 phase is always found, the Curie temperature remains constant and equal to 295 K (the highest temperature never observed before in such series of compositions), while for La/Mn>0.9, there is a formation of Mn vacancies giving rise to a lowering of Curie temperature resulting of a frustration of ferromagnetic interactions. 相似文献