全文获取类型
收费全文 | 636篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
化学 | 447篇 |
晶体学 | 5篇 |
力学 | 13篇 |
数学 | 68篇 |
物理学 | 123篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 12篇 |
2017年 | 21篇 |
2016年 | 24篇 |
2015年 | 20篇 |
2014年 | 21篇 |
2013年 | 42篇 |
2012年 | 28篇 |
2011年 | 51篇 |
2010年 | 35篇 |
2009年 | 22篇 |
2008年 | 39篇 |
2007年 | 32篇 |
2006年 | 26篇 |
2005年 | 40篇 |
2004年 | 29篇 |
2003年 | 25篇 |
2002年 | 12篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1972年 | 2篇 |
1968年 | 4篇 |
1967年 | 2篇 |
1928年 | 2篇 |
1927年 | 3篇 |
1920年 | 3篇 |
1893年 | 2篇 |
1883年 | 2篇 |
排序方式: 共有656条查询结果,搜索用时 140 毫秒
61.
Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Cremaldi LM Darling C Denisenko K Devmal S Fernandez A Fox GF Gagnon P Gobel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B Magnin J Massafferri A MayTal-Beck S Meadows B de Mello Neto JR Mihalcea D Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》2001,86(5):770-774
From a sample of 1172 +/- 61 D(+)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)-->pi(-)pi(+)pi(+))/gamma(D(+)-->K-pi(+)pi(+)) = 0.0311 +/- 0.0018(+0.0016)(-0.0026). Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478(+24)(-23) +/- 17 MeV/c(2) and width 324(+42)(-40) +/- 21 MeV/c(2) accounts for approximately half of all decays. 相似文献
62.
T.P. Iglesias Joo Carlos R. Reis L. Faria-Busto 《The Journal of chemical thermodynamics》2008,40(9):1475-1476
In a previous work, an ideal fluid mixture is assumed to be a homogeneous linear and isotropic system that verifies the following conditions: (I) no interaction between molecules, (II) point-like molecules and (III) under fixed temperature and pressure conditions the number of molecules per unit volume is the same for both the individual components and the mixture. It was shown that for such ideal mixture the permittivity is the sum of the individual permittivities weighted with the mole fractions of the components.In this work it is shown that independently of the latter assumption the permittivity of the system can be expressed as the sum of the individual permittivities weighted with the volume fractions of the components. 相似文献
63.
Starting from Smoluchowski's hypothesis, a simple algorithm is developed in order to obtain the apparent rate constant at large values of time, t, with some physical and chemical processes, as in the case of diffusion controlled reactions. Some practical examples are illustrated, assuming nonuniform distribution function, space-dependent diffusion coefficient or short-range interaction leading to an asymptotic analytical expression of the form α + β/√t, where α and β are constants function of the system of interest. 相似文献
64.
We establish the asymptotic normality of the squared L
2-norm of the approximation error of a linear wavelet estimator of the density of a distribution. The calculations are based on the smallness of correlations between the coefficients of the high-frequency part of the multiresolution expansion of the estimator.Supported by the FCT Foundation (Portugal) in the framework of the project Probability and Statistics (2000–2002), Centro de Matematica, Universidade da Beira Interior.__________Translated from Lietuvos Matematikos Rinkinys, Vol. 45, No. 2, pp. 184–207, April–June, 2005. 相似文献
65.
C.V.S. Ieggli D. Bohrer S. Noremberg P.C. do Nascimento L.M. de Carvalho S.L. Vieira R.N. Reis 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
An oil-in-water formulation has been optimized to determine trace levels of selenium in whole hen eggs by graphite furnace atomic absorption spectrometry. This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures. Graphite furnace atomic absorption spectrometric (GF AAS) measurement was carried out using standard addition calibration and Pd as a modifier. The precision, expressed as relative standard deviation, was better than 5% and the limit of detection was 1 µg L− 1. The validation of the method was performed against a standard reference material Whole Egg Powder (RM 8415), and the measured Se corresponded to 95.2% of the certified value. The method was used for the determination of the Se level in eggs from hens treated with Se dietary supplements. Inorganic and organic Se sources were added to hen feed. The Se content of eggs was higher when hens were fed with organic Se compared to the other treatments. The proposed method, including sample emulsification for subsequent Se determination by GF AAS has proved to be sensitive, reproducible, simple and economical. 相似文献
66.
M. A. von Reis 《Fresenius' Journal of Analytical Chemistry》1890,29(1):188-192
Ohne Zusammenfassung 相似文献
67.
M. C. Freitas M. A. Reis A. P. Marques H. Th. Wolterbeek 《Journal of Radioanalytical and Nuclear Chemistry》2000,244(1):109-113
Transplants of the lichen Parmelia sulcata Taylor were suspended in nylon bags within a rectangle of 15 km wide and 25 km long on a grid 2.5 km×2.5 km, centered in a power station. In all of the 47 places two sets of four transplants each were hanged, one facing the wind and the other opposing the wind. Care was taken (1) in covering the two sets with a polyethylene roof to prevent leaching of elements in the lichen, (2) in building a hanging system that could rotate according to the wind direction, and (3) in orienting one set towards the wind and the other set opposite the wind. During a one-year period, one transplant of each set was taken for analysis after a 3 month exposure. Some results of the second campaign (after a 6 month exposure) obtained by INAA are shown and compared with the first campaign (after a 3 month exposure). Elemental contents are mapped and discussed. 相似文献
68.
Christos Apostolidis Dr. Bernd Schimmelpfennig Dr. Nicola Magnani Dr. Patric Lindqvist‐Reis Dr. Olaf Walter Dr. Richard Sykora Dr. Alfred Morgenstern Dr. Eric Colineau Dr. Roberto Caciuffo Prof. Dr. Reinhardt Klenze Dr. Richard G. Haire Dr. Jean Rebizant Dr. Frank Bruchertseifer Dr. Thomas Fanghänel Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(36):6229-6229
69.
Rafael Germano Santana Derisvaldo Rosa Paiva Roberto da Silva Gomes Adriana Karla C. A. Reis 《Magnetic resonance in chemistry : MRC》2013,51(5):316-319
The complete assignment of the 1H and 13C NMR spectra of various 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamide‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamides with p‐methoxy, o‐chloro and m‐chloro substituents is reported. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
70.
Irinéia R. do Nascimento Raildo M. de Jesus Walter N.L. dos Santos Anderson Santos Souza Pedro Sanches dos Reis 《Microchemical Journal》2010,96(1):37-41
In this work, the mineral composition of fresh bovine milk obtained from the milk-producing areas of the Brazilian State of Sergipe was examined. A dry-ashed digestion method and the ICP OES technique were used for the quantification of mineral elements (e.g., Ca, Mg, K, Na, P, Sr and Zn) in 27 samples of milk collected from properties located in milk-producing areas around Nossa Senhora da Glória. The following ranges of values (% m/v) were obtained: 0.063 to 0.117 for Ca; 0.060 to 0.114 for P; 0.024 to 0.064 for Na; and 0.087 to 0.164 for K. The ranges of values (mg L− 1) for the other mineral elements were also found: 0.68 to 1.89 for Sr; 2.46 to 5.73 for Zn; and 54.2 to 109.9 for Mg. Additionally, the exploratory evaluation of the 27 milk samples was performed using principal component analysis (PCA) involving seven variables dealing with the effect of different management systems (conventional and organic) on milk composition. The results show that there are indeed differences between the mineral composition of milk from properties that use organic practices and those that use conventional management practices. 相似文献