全文获取类型
收费全文 | 1949篇 |
免费 | 54篇 |
国内免费 | 10篇 |
专业分类
化学 | 1344篇 |
晶体学 | 24篇 |
力学 | 76篇 |
数学 | 141篇 |
物理学 | 428篇 |
出版年
2023年 | 21篇 |
2022年 | 31篇 |
2021年 | 43篇 |
2020年 | 38篇 |
2019年 | 65篇 |
2018年 | 37篇 |
2017年 | 35篇 |
2016年 | 68篇 |
2015年 | 34篇 |
2014年 | 51篇 |
2013年 | 152篇 |
2012年 | 91篇 |
2011年 | 157篇 |
2010年 | 85篇 |
2009年 | 58篇 |
2008年 | 80篇 |
2007年 | 75篇 |
2006年 | 73篇 |
2005年 | 56篇 |
2004年 | 63篇 |
2003年 | 47篇 |
2002年 | 52篇 |
2001年 | 29篇 |
2000年 | 27篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 13篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 19篇 |
1977年 | 11篇 |
1975年 | 11篇 |
1966年 | 25篇 |
1965年 | 18篇 |
1964年 | 14篇 |
1963年 | 16篇 |
1962年 | 43篇 |
1961年 | 11篇 |
1960年 | 12篇 |
排序方式: 共有2013条查询结果,搜索用时 20 毫秒
1.
Summary Thermodynamic effective fixed charge densities of mercuric phosphate and carbonate parchment supported membranes were evaluated by a number of methods particularly those ofTeorell-Meyer-Sievers, Altug andHair andKobatake et al. The value of the permselectivity was obtained for the two membranes based onKobatake et al. procedure. Membrane transport number was calculated using a modified Nernst relation and compared with the values determined by the TMS method. The theoretical predictions for membrane potential usingKobatake et al. equation are borne out quite satisfactorily by our experimental results for both membrane.
With 8 figures and 3 tables 相似文献
Zusammenfassung Es wurden die Dichte der fixierten Ladungen von Quecksilberphosphat und Quecksilberkarbonat-Niederschlagsmembranen nach den Methoden vonTorell-Meyer-Sievers, Altug undHair undKobatake bestimmt. Weiterhin wurden Durchlässigkeit und Transportzahlen ermittelt und mit Werten der TMS-Methode verglichen. Theoretische Voraussagen über das Membranpotential nach den Gleichungen vonKobatake stimmen mit den experimentellen Ergebnissen überein.
With 8 figures and 3 tables 相似文献
2.
M. Prakash Y. R. Waghmare I. Mehrotra 《Zeitschrift für Physik A Hadrons and Nuclei》1976,278(2):155-164
Low-lying spectra of6Li,18F,18O,42Sc,42Ca,58Ni and92Zr are studied with Sussex matrix elements (SME) and their central, spin-orbit and tensor components. It is observed that major contribution to level energies comes from the central part, while the tensor part provides the finer details of spectra, particularly forT=0 levels. The spin-orbit part does not make any appreciable contribution to level energies. A phenomenological renormalization of the SME is carried out to improve the agreement with the experimental results. It turns out that some of the low-lyingT=0 levels can be satisfactorily described if the SME in the3S1 relative state are made (1+α) times their bare interaction value, whereα is a constant to be determined from a comparison with experimental level energies. Similarly, forT=1 levels, better agreement with the experimental results is obtained if aδ-function-plus-quadrupole interaction is added to the SME. 相似文献
3.
Nagarajan Shobana Pandurangan Prakash Antony V. Samrot P. J. Jane Cypriyana Purohit Kajal Mahendran Sathiyasree Subramanian Saigeetha T. Stalin Dhas D. Alex Anand Gokul Shankar Sabesan Bala Sundaram Muthuvenkatachalam Basanta Kumar Mohanty Sridevi Visvanathan 《Molecules (Basel, Switzerland)》2022,27(12)
Plant gums are bio-organic substances that are derived from the barks of trees. They are biodegradable and non-adverse complex polysaccharides that have been gaining usage in recent years due to a number of advantages they contribute to various applications. In this study, gum was collected from Moringa oleifera and Azadirachta indica trees, then dried and powdered. Characterizations of gum polysaccharides were performed using TLC, GC-MS, NMR, etc., and sugar molecules such as glucose and xylose were found to be present. Effects of the gums on Abelmoschus esculentus growth were observed through root growth, shoot growth, and biomass content. The exposure of the seeds to the plant gums led to bio stimulation in the growth of the plants. Poor quality soil was exposed to the gum polysaccharide, where the polysaccharide was found to improve soil quality, which was observed through soil analysis and SEM analysis of soil porosity and structure. Furthermore, the plant gums were also found to have bio-pesticidal activity against mealybugs, which showed certain interstitial damage evident through histopathological analysis. 相似文献
4.
A two-step short and efficient strategy for the synthesis of substituted piperidones and piperidines in high diastereoselectivity (only trans-configuration), by employing cascade type reaction using BF3·Et2O or by carrying out one pot deprotection of tBoc group followed by intramolecular aza-Michael addition of α,β-unsaturated beta keto esters has been developed. Using a similar strategy a short access to hydroxy pipecolic acid is also described. Very simple and rapid experimental procedures involving mild conditions and only one or two chromatographic purifications are the main features of the process. 相似文献
5.
6.
7.
Thermal expansion measurements have been carried out on Fe substituted superconducting compounds Y1Ba2(Cu1−x
Fe
x
)3O
y
(0<x<4%) using a high resolution dilatometer employing the three terminal capacitance technique. The experimental set up is sensitive
enough to detect changes in α of less than 10−8K−1. Results show that the jump Δα in the coefficient of linear thermal expansion at the superconducting transition temperature,T
c, increases almost linearly with Fe concentration. The normal state thermal expansion coefficient α first decreases, attains
a minimum value aroundx=1% and then increases for higher Fe concentrations. The oxygen content per unit formula is almost constant up tox=1% and then increases rapidly withx. It has also been observed that the anomalous behaviour of α around 260 K observed by Meingastet al [22] for Fe concentrationx=5% is due to inadequate annealing of the sample. 相似文献
8.
9.
B.G. Prakash 《Journal of sound and vibration》1980,70(2):303-305
10.
The vacuum ultraviolet (VUV) absorption spectrum of difluoromethane (CH2F2) was studied using synchrotron radiation from the storage ring Indus-1, Indore, India. Spectra were recorded in the spectral region 1050–1500 Å (~8.3–11.8 eV) at a resolution of 1.5 Å. Three absorption band systems were observed in this region. Overall features observed are in good agreement with previously published work. Some discrepancies in assignments of the observed vibronic bands carried out by previous workers have been resolved. The observed bands have been classified in terms of Rydberg series. 相似文献