全文获取类型
收费全文 | 29909篇 |
免费 | 111篇 |
国内免费 | 278篇 |
专业分类
化学 | 11160篇 |
晶体学 | 266篇 |
力学 | 1415篇 |
综合类 | 12篇 |
数学 | 9141篇 |
物理学 | 8304篇 |
出版年
2022年 | 40篇 |
2021年 | 57篇 |
2020年 | 37篇 |
2019年 | 34篇 |
2018年 | 1204篇 |
2017年 | 1456篇 |
2016年 | 738篇 |
2015年 | 584篇 |
2014年 | 492篇 |
2013年 | 696篇 |
2012年 | 3169篇 |
2011年 | 2377篇 |
2010年 | 1852篇 |
2009年 | 1574篇 |
2008年 | 632篇 |
2007年 | 670篇 |
2006年 | 678篇 |
2005年 | 4500篇 |
2004年 | 3968篇 |
2003年 | 2344篇 |
2002年 | 523篇 |
2001年 | 301篇 |
2000年 | 104篇 |
1999年 | 180篇 |
1998年 | 122篇 |
1997年 | 77篇 |
1996年 | 61篇 |
1995年 | 52篇 |
1994年 | 50篇 |
1992年 | 175篇 |
1991年 | 160篇 |
1990年 | 138篇 |
1989年 | 113篇 |
1988年 | 106篇 |
1987年 | 61篇 |
1986年 | 50篇 |
1985年 | 45篇 |
1984年 | 36篇 |
1982年 | 33篇 |
1978年 | 34篇 |
1976年 | 84篇 |
1975年 | 44篇 |
1974年 | 42篇 |
1973年 | 50篇 |
1972年 | 41篇 |
1970年 | 40篇 |
1969年 | 40篇 |
1968年 | 35篇 |
1967年 | 32篇 |
1966年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
P. Ko?cik A. Okopińska 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(3):93
We study systems of a few charged bosons contained within a strongly anisotropic harmonic
trap. A detailed examination of the ground-state correlation properties of two-, three-,
and four-particle systems is carried out within the framework of the single-mode
approximation of the transverse components. The linear correlation entropy of the quasi-1D
systems is discussed in dependence on the confinement anisotropy and compared with a
strictly 1D limit. Only at weak interaction the correlation properties depend strongly on
the anisotropy parameter. 相似文献
902.
903.
904.
We give an elementary proof of a majorization inequality concerning Wright-convex functions. 相似文献
905.
Carbohydrates are used in nature as molecular recognition tools. Understanding their conformational behavior upon aggregation helps in rationalizing the way in which cells and bacteria use sugars to communicate. Here, the simplest α-hydroxy carbonyl compound, glycolaldehyde, was used as a model system. It was shown to form compact polar C2-symmetric dimers with intermolecular O–H⋅⋅⋅O=C bonds, while sacrificing the corresponding intramolecular hydrogen bonds. Supersonic jet infrared (IR) and Raman spectra combined with high-level quantum chemical calculations provide a consistent picture for the preference over more typical hydrogen bond insertion and addition patterns. Experimental evidence for at least one metastable dimer is presented. A rotational spectroscopy investigation of these dimers is encouraged, also in view of astrophysical searches. The binding motif competition of aldehydic sugars might play a role in chirality recognition phenomena of more complex derivatives in the gas phase. 相似文献
906.
This review reports on the latest developments in the field of magnetic nanocomposites, with a special focus on the potentials introduced by the incorporation of magnetic nanoparticles into polymer and supramolecular matrices. The general notions and the state of the art of nanocomposite materials are summarized and the results reported in the literature over the last decade on magnetically responsive films, capsules and gels are reviewed. The most promising concepts that have inspired the design of magneto-responsive nanocomposites are illustrated through remarkable examples where the integration of magnetic nanoparticles into organic architectures has successfully taken to the development of responsive multifunctional materials. 相似文献
907.
This paper presents a special use of the linear poroelasticity theory to describe tidally induced groundwater oscillations. Two models of oscillation inducing mechanism make use of this theory to predict groundwater level fluctuations. The numerical solutions of both models are presented and compared with well water level measurement obtained in Police Basin, north-east Bohemia. 相似文献
908.
Tomomi Ishikawa LuChang Jin Huey-Wen Lin Andreas Sch?fer Yi-Bo Yang Jian-Hui Zhang Yong Zhao 《中国科学:物理学 力学 天文学(英文版)》2019,(9)
正Recent years have witnessed rapid progress in calculating parton distribution functions (PDFs), rather than just their moments, from lattice QCD [1-9]. The most remarkable aspect of such calculations is that one can connect appropriately chosen Euclidean correlation functions calculable on the lattice to PDFs through a perturbative matching relation. This can be understood in the framework of the large-momentum 相似文献
909.
Elisa Musella Dr. Isacco Gualandi Dr. Erika Scavetta Dr. Massimo Gazzano Arianna Rivalta Dr. Elisabetta Venuti Dr. Meganne Christian Dr. Vittorio Morandi Prof. Dr. Domenica Tonelli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(71):16301-16310
Layered double hydroxides (LDHs) have been widely studied for their plethora of fascinating features and applications. The potentiostatic electrodeposition of LDHs has been extensively applied in the literature as a fast and direct method to substitute classical chemical routes. However, the electrochemical approach does not usually allow for a fine control of the MII/MIII ratio in the synthesized material. By employing a recently proposed potentiodynamic method, LDH films of controlled composition are herein prepared with good reproducibility, using different ratios of the trivalent (Fe or Al) to bivalent (Co) cations in the electrolytic solution. All the obtained materials are shown to be effective oxygen evolution reaction (OER) catalysts, and are thoroughly characterized by a multi-technique approach, including FE-SEM, XRD, Raman, AES and a wide range of electrochemical procedures. 相似文献
910.
Pier G. Desideri Luciano Lepri Roberto Udisti Leonardo Checchini Massimo Del Bubba Renato Cini 《International journal of environmental analytical chemistry》2013,93(3-4):331-351
Abstract Organic compounds extractable with n-hexane were identified and quantitatively determined in pack, surface and deep snow samples taken at different depths and collected at several altitudes above sea level from Antarctica during the 1993/94 Italian expedition. The comparison between the composition of organic compounds in snow and the ones in pack and sea-water samples pointed out that the three matrices substantially contain the same biogenic and anthropogenic organic compounds. The contribution of marine aerosol to organic content in the snow is confirmed by the enrichment ratios calculated for the more representative classes of identified compounds (n-alkanes, phthalates and low molecular weight alkylbenzenes). The changes in the composition of organic compounds in snow as the altitude increases seem to depend on the dimensional spectrum of the aerosol. Thus, smallest particles, richest in surfactant material, reach the highest altitudes. 相似文献