全文获取类型
收费全文 | 24191篇 |
免费 | 3027篇 |
国内免费 | 2087篇 |
专业分类
化学 | 14573篇 |
晶体学 | 427篇 |
力学 | 1648篇 |
综合类 | 131篇 |
数学 | 2583篇 |
物理学 | 9943篇 |
出版年
2024年 | 42篇 |
2023年 | 380篇 |
2022年 | 557篇 |
2021年 | 685篇 |
2020年 | 812篇 |
2019年 | 846篇 |
2018年 | 763篇 |
2017年 | 696篇 |
2016年 | 973篇 |
2015年 | 976篇 |
2014年 | 1183篇 |
2013年 | 1599篇 |
2012年 | 2039篇 |
2011年 | 2104篇 |
2010年 | 1500篇 |
2009年 | 1577篇 |
2008年 | 1649篇 |
2007年 | 1408篇 |
2006年 | 1365篇 |
2005年 | 1078篇 |
2004年 | 878篇 |
2003年 | 673篇 |
2002年 | 592篇 |
2001年 | 745篇 |
2000年 | 600篇 |
1999年 | 490篇 |
1998年 | 371篇 |
1997年 | 349篇 |
1996年 | 321篇 |
1995年 | 279篇 |
1994年 | 231篇 |
1993年 | 200篇 |
1992年 | 187篇 |
1991年 | 181篇 |
1990年 | 144篇 |
1989年 | 110篇 |
1988年 | 95篇 |
1987年 | 68篇 |
1986年 | 62篇 |
1985年 | 70篇 |
1984年 | 51篇 |
1983年 | 41篇 |
1982年 | 37篇 |
1981年 | 39篇 |
1980年 | 31篇 |
1979年 | 28篇 |
1978年 | 28篇 |
1977年 | 23篇 |
1975年 | 24篇 |
1974年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
P. C. Morais A. C. Oliveira V. K. Garg M. L. Silva E. F. C. Alcântara F. Q. Soares D. Rabelo 《Hyperfine Interactions》2007,177(1-3):51-56
We have used time-differential perturbed angular correlation (PAC) spectroscopy with 181Ta-probes to study the electric field gradient at Zr-sites in synthetic zircon and hafnon between room temperature and 1,200°C. PAC spectra are similar to those obtained from naturally occurring zircons. In particular, a change in slope of the quadrupole coupling vs. temperature is observed in the synthetic zircon at the same temperature as seen in natural zircons from the Mud Tank carbonatite (Australia). The synthetic hafnon data also shows this feature but at somewhat higher temperature. Low-temperature PAC spectra of both synthetic zircon and hafnon have a clearly reduced anisotropy. We believe that the cause for this is a electronic defect, possibly created during the β-decay of the probe parent nucleus. 相似文献
73.
JIAO Peng ZHANG Qi-han XU Jia-xi+{**} Key Laboratory of Bioorganic Chemistry Molecular Engineering of Ministry of Education College of Chemistry Molecular Engineering Peking University Beijing China 《高等学校化学研究》2006,(6)
IntroductionN,N′-Bis [1-( hydroxymethyl) alkyl] dicarboxa-mides are important intermediates for the syntheses ofbis-oxazolines, which are a class of the most importantand widely used ligands in catalytic asymmetric reac-tions[1,2]. On determining the str… 相似文献
74.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
75.
The purpose of this work is to investigate the weakened Ambrosetti–Prodi type multiplicity results for weak doubly periodic solutions of damped beam equations. By using the topological degree theory, the author obtains a result which is similar to the result for damped wave equations in the literature. 相似文献
76.
Q.-Y. Shao A.-D. Li J.-B. Cheng H.-Q. Ling D. Wu Z.-G. Liu N.-B. Ming C. Wang H.-W. Zhou B.-Y. Nguyen 《Applied Physics A: Materials Science & Processing》2005,81(6):1181-1185
LaAlO3 (LAO) gate dielectric films were deposited on Si substrates by low-pressure metalorganic chemical vapor deposition. The interfacial structure and composition distribution were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectroscopy (SIMS), and Auger-electron spectroscopy (AES). HRTEM confirms that there exists an interfacial layer between LAO and Si in most samples. AES, SIMS, and XPS analyses indicate that the interfacial layer is compositionally graded La–Al silicate and the Al element is severely deficient close to the Si surface. Electrical properties of LAO films were evaluated. No evident difference in electrical properties between samples with and without native SiO2 layers was observed. The electrical properties are discussed in terms of LAO growth mechanisms, in relation to the interfacial structure. PACS 73.40.Qv; 81.15.Gh; 77.55.+f; 68.35.-p 相似文献
77.
We present a semimonolithic frequency-doubler from 1080 to 540 nm with 80% doubling efficiency and up to 849-mW output power of green light. 相似文献
78.
79.
80.