全文获取类型
收费全文 | 90552篇 |
免费 | 16359篇 |
国内免费 | 9188篇 |
专业分类
化学 | 61581篇 |
晶体学 | 915篇 |
力学 | 5747篇 |
综合类 | 512篇 |
数学 | 10088篇 |
物理学 | 37256篇 |
出版年
2024年 | 344篇 |
2023年 | 2043篇 |
2022年 | 3294篇 |
2021年 | 3559篇 |
2020年 | 3927篇 |
2019年 | 3510篇 |
2018年 | 3216篇 |
2017年 | 2866篇 |
2016年 | 4582篇 |
2015年 | 4362篇 |
2014年 | 5320篇 |
2013年 | 6764篇 |
2012年 | 8209篇 |
2011年 | 8397篇 |
2010年 | 5546篇 |
2009年 | 5379篇 |
2008年 | 5779篇 |
2007年 | 5063篇 |
2006年 | 4760篇 |
2005年 | 3818篇 |
2004年 | 2940篇 |
2003年 | 2294篇 |
2002年 | 2107篇 |
2001年 | 1815篇 |
2000年 | 1604篇 |
1999年 | 1839篇 |
1998年 | 1591篇 |
1997年 | 1576篇 |
1996年 | 1563篇 |
1995年 | 1322篇 |
1994年 | 1150篇 |
1993年 | 996篇 |
1992年 | 858篇 |
1991年 | 783篇 |
1990年 | 643篇 |
1989年 | 501篇 |
1988年 | 370篇 |
1987年 | 308篇 |
1986年 | 323篇 |
1985年 | 261篇 |
1984年 | 151篇 |
1983年 | 117篇 |
1982年 | 100篇 |
1981年 | 57篇 |
1980年 | 42篇 |
1979年 | 15篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1957年 | 31篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In this paper we formulate a theorem on the persistence of elliptic lower-dimensional invariant tori for nearly integrable analytic Hamiltonian systems under the first Melnikov condition and Rüssmann’s non-degeneracy condition, and give the measure estimates of parameters for the non-resonance conditions under Rüssmann’s non-degeneracy condition, which is essential for the proof of our result. 相似文献
102.
The 57Fe Mössbauer effect study at 5.0 K and in an external magnetic field of 9.0 T on a high-quality stable decagonal quasicrystal Al65Co15Cu19.9Fe0.1 is presented. It is shown that the iron atoms are located in two distinct classes of sites. The values of the principal component of the electric field gradient tensor and the asymmetry parameter at these sites are, respectively, ?1.90(10)?×?1021 V/m2, 0.97(15) and ?3.95(12)?×?1021 V/m2, 0.00(17). 相似文献
103.
Stadia are popular models of chaotic billiards introduced by Bunimovich in 1974. They are analogous to dispersing billiards
due to Sinai, but their fundamental technical characteristics are quite different. Recently many new results were obtained
for various chaotic billiards, including sharp bounds on correlations and probabilistic limit theorems, and these results
require new, more powerful technical apparatus. We present that apparatus here, in the context of stadia, and prove “regularity”
properties.
相似文献
104.
A mistake concerning the ultra LI-ideal of a lattice implication algebra is pointed out, and some new sufficient and necessary conditions for an LI-ideal to be an ultra LI-ideal are given. Moreover, the notion of an LI-ideal is extended to MTL-algebras, the notions of a (prime, ultra, obstinate, Boolean) LI-ideal and an ILI-ideal of an MTL-algebra are introduced, some important examples are given, and the following notions are proved to be equivalent in MTL-algebra: (1) prime proper LI-ideal and Boolean LI-ideal, (2) prime proper LI-ideal and ILI-ideal, (3) proper obstinate LI-ideal, (4) ultra LI-ideal.
This work was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. Y605389) and K. C. Wong
Magna Fund in Ningbo University. 相似文献
105.
In this article,the Hausdorff dimension and exact Hausdorff measure function of any random sub-self-similar set are obtained under some reasonable conditions.Several examples are given at the end. 相似文献
106.
900 MHz 1H NMR (nuclear magnetic resonance) spectroscopy was used to analyze metabolites in allantoic fluid of the chicken embryo in
the 9th incubation day without any chemical or physical sample separation. The result showed that superhigh spectral dispersion
and sensitivity at 900 MHz are useful in directly analyzing a complex mixture, particularly in resolving the overlapped NMR
resonances. In this study, we had assigned 61 metabolites and 26 chemical fragments in the allantoic fluid. The relative concentrations
of the major metabolites were also measured. Among the assigned metabolites, some were detected by NMR in chicken embryo allantoic
fluids for the first time. The biological functions of these compounds were briefly discussed.
Authors' address: Maili Liu, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute
of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China 相似文献
107.
Hua Zhang Nabil A. Amro Robert Elghanian Joseph Fragala 《Applied Surface Science》2006,253(4):1960-1963
A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications. 相似文献
108.
Nanometer scale Al/AlN multilayers have been prepared by dc magnetron sputtering technique with a columnar target. A set of Al/AlN multilayers with the Al layer thickness of 2.9 nm and the AlN layer thickness variation from 1.13 to 6.81 nm were determined. Low angle X-ray diffraction (LAXRD) was used to analyze the layered structure of multilayers. The phase structure of the coatings was investigated with grazing angle XRD (GAXRD). Mechanical properties of these multilayers were thoroughly studied using a nanoindentation and ball-on-disk micro-tribometer. It was found that the multilayer hardness and reduced modulus showed no strong dependence on the AlN layer thickness. Al2.9 nm/AlN1.13 nm multilayer had more excellent tribological properties than single layers and other proportion multilayers with a lowest friction coefficient of 0.15. And the tribological properties of all the multilayers are superior to the AlN single layer. 相似文献
109.
110.