全文获取类型
收费全文 | 353358篇 |
免费 | 3128篇 |
国内免费 | 1157篇 |
专业分类
化学 | 183709篇 |
晶体学 | 5913篇 |
力学 | 16014篇 |
综合类 | 4篇 |
数学 | 37958篇 |
物理学 | 114045篇 |
出版年
2020年 | 2771篇 |
2019年 | 3065篇 |
2018年 | 4030篇 |
2017年 | 4001篇 |
2016年 | 5990篇 |
2015年 | 3665篇 |
2014年 | 5913篇 |
2013年 | 15056篇 |
2012年 | 11455篇 |
2011年 | 14120篇 |
2010年 | 10065篇 |
2009年 | 10040篇 |
2008年 | 13274篇 |
2007年 | 13051篇 |
2006年 | 12541篇 |
2005年 | 11436篇 |
2004年 | 10471篇 |
2003年 | 9411篇 |
2002年 | 9274篇 |
2001年 | 11584篇 |
2000年 | 8640篇 |
1999年 | 6732篇 |
1998年 | 5250篇 |
1997年 | 5270篇 |
1996年 | 4988篇 |
1995年 | 4574篇 |
1994年 | 4529篇 |
1993年 | 4444篇 |
1992年 | 5031篇 |
1991年 | 5229篇 |
1990年 | 4876篇 |
1989年 | 4819篇 |
1988年 | 4807篇 |
1987年 | 4710篇 |
1986年 | 4413篇 |
1985年 | 5816篇 |
1984年 | 6011篇 |
1983年 | 4806篇 |
1982年 | 4973篇 |
1981年 | 4785篇 |
1980年 | 4669篇 |
1979年 | 5023篇 |
1978年 | 5211篇 |
1977年 | 5082篇 |
1976年 | 5126篇 |
1975年 | 4705篇 |
1974年 | 4698篇 |
1973年 | 4790篇 |
1972年 | 3281篇 |
1971年 | 2701篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
V. Bradnova M. M. Chernyavsky L. Just S. P. Kharlamov A. D. Kovalenko M. Haiduc K. A. Kotel’nikov V. A. Krasnov V. G. Larionova F. G. Lepekhin A. I. Malakhov G. I. Orlova N. G. Peresadko N. G. Polukhina P. A. Rukoyatkin V. V. Rusakova N. A. Salmanova B. B. Simonov S. Vokal P. I. Zarubin 《Physics of Atomic Nuclei》2003,66(9):1646-1650
A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the 10B nucleus at low energy-momentum transfers as the first step of the research. 相似文献
112.
113.
Effect of nickel coating on electrochemical performance of graphite anodes for lithium ion batteries
Among the different materials often studied and proposed as negative electrodes for lithium-ion batteries, graphite anodes
are the most used in commercial batteries. For this study, synthetic graphite was tested. During the first discharge 0.2 Li
ions were consumed for the formation of the SEI film and the capacity reaches about 387 mAh/g. But at the end of the first
charge only 72% of the initial charge was recovered (the reversible capacity is about 279 mAh/g). In order to improve this
performance we have deposited metallic nickel on graphite with the intention to obtain a homogeneous thin layer able to modify
the nature of the SEI film, to allow the diffusion of lithium ions through the protective layer, and also to increase the
performance of graphite electrodes. The results show a decrease of the irreversible capacity loss (16% instead of 28% for
pure graphite electrodes) as well as better cycleability for a nickel-deposited graphite electrode with only 11% weight ratio
of nickel. On the other hand, an increase of the nickel content decreases this performance. 相似文献
114.
Fundamentals of the direct measurement of sound intensity and practical applications 总被引:1,自引:0,他引:1
Sound intensity is a measure of the magnitude and direction of the flow of sound energy. Developments in sound intensity measurement capabilities in the last quarter century have occurred because of several reasons. The main ones include the derivation of the cross-spectral formulation for sound intensity and developments in digital signal processing. This paper begins with a brief historical introduction of sound intensity measurements. Then elementary theory for sound intensity is presented. A section on sound intensity measurements is then included. The next section of the paper discusses sources of measurement error; the major sources of error are described in some detail. The paper continues with a discussion of the main applications of sound intensity measurements: sound power determination, noise source identification, and transmission loss measurements. The paper concludes with a discussion of ISO and ANSI intensity related standards and relevant references. 相似文献
115.
116.
R. Pizzoferrato L. Lagonigro T. Ziller A. Di Carlo R. Paolesse F. Mandoj A. Ricci C. Lo Sterzo 《Chemical physics》2004,300(1-3):217-225
We study the infrared emission at 1.54 μm of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host π-conjugate polymers of type poly(arylene–ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 μm φIR=4×10−4 is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acac with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Förster model for polymeric donors. The experimental values of the critical radius R0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. 相似文献
117.
For ϕ a δ-subharmonic function, sharp results are obtained that connectA(r, ϕ), B(r, ϕ) andT(r, ϕ), whereA(r, ϕ)=inf|z|=r
ϕ(z),B(r, ϕ)=sup|z|=r
ϕ(z), andT(r, ϕ) is the Nevanlinna characteristics. 相似文献
118.
119.
I. P. Kayumov 《Mathematical Notes》2005,78(3-4):498-502
In this paper, we prove Brennan's conjecture for conformal mappings f of the disk {z : | z| < 1} assuming that the Taylor coefficients of the function log(zf′(z)/f(z)) at zero are nonnegative. We also obtain inequalities for the integral means over the circle |z| = r of the squared modulus of the function zf′(z)/f(z). 相似文献
120.
C. Czeranowsky V. M. Baev G. Huber P. A. Khandokhin Ya. I. Khanin I. V. Koryukin E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):723-728
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser. 相似文献