全文获取类型
收费全文 | 19390篇 |
免费 | 611篇 |
国内免费 | 55篇 |
专业分类
化学 | 12315篇 |
晶体学 | 356篇 |
力学 | 675篇 |
综合类 | 1篇 |
数学 | 1785篇 |
物理学 | 4924篇 |
出版年
2024年 | 74篇 |
2023年 | 192篇 |
2022年 | 492篇 |
2021年 | 497篇 |
2020年 | 526篇 |
2019年 | 599篇 |
2018年 | 547篇 |
2017年 | 530篇 |
2016年 | 777篇 |
2015年 | 558篇 |
2014年 | 874篇 |
2013年 | 1581篇 |
2012年 | 1339篇 |
2011年 | 1388篇 |
2010年 | 927篇 |
2009年 | 730篇 |
2008年 | 924篇 |
2007年 | 926篇 |
2006年 | 729篇 |
2005年 | 653篇 |
2004年 | 505篇 |
2003年 | 404篇 |
2002年 | 338篇 |
2001年 | 217篇 |
2000年 | 183篇 |
1999年 | 153篇 |
1998年 | 120篇 |
1997年 | 130篇 |
1996年 | 146篇 |
1995年 | 120篇 |
1994年 | 122篇 |
1993年 | 159篇 |
1992年 | 161篇 |
1991年 | 121篇 |
1990年 | 125篇 |
1989年 | 120篇 |
1988年 | 107篇 |
1987年 | 93篇 |
1985年 | 134篇 |
1984年 | 156篇 |
1983年 | 107篇 |
1982年 | 110篇 |
1981年 | 106篇 |
1980年 | 114篇 |
1979年 | 128篇 |
1978年 | 113篇 |
1977年 | 112篇 |
1976年 | 94篇 |
1975年 | 78篇 |
1973年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Two binary mixtures of polar liquid crystal materials were previously reported to exhibit three incommensurate smectic A phases predicted for such materials on the basis of phenomenological theory. Results of our recent high-resolution X-ray scattering experiments show that no incommensurate phases exist in the two systems. Wide coexistence regions are found at first order transitions between various frustrated smectic phases of these mixtures. These regions were previously identified as the incommensurate smectic A phases. The phase diagrams of the two systems determined with high-resolution X-ray technique are shown to be in excellent agreement with Baroisa-Prost-Lubensky theory. 相似文献
52.
Gamma ray bursts (GRBs) have been proposed as one possible class of sources of the ultrahigh energy cosmic ray (UHECR) events
observed up to energies ≳ 1020 eV. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up
to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability
of the prompt TeV γ-rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole. 相似文献
53.
54.
We have calculated total and differential cross-sections for 1s →ns (n = 2, 3, 4) electron impact excitation of hydrogen and hydrogenic ions at various energies in Coulomb-projected Born approximation.
Distortion due to static interactions, target polarization and exchange effects has been incorporated in the initial channel.
The present calculations have been compared with other theoretical and experimental results. 相似文献
55.
56.
Homopolymerization of methyl methacrylate (MMA) was carried out in the presence of triphenylstibonium 1,2,3,4-tetraphenyl-cyclopentadienylide
as an initiator in dioxane at 65°C±0·l°C. The system follows non-ideal radical kinetics (R
p
∝ [M]1·4 [I]0·44
@#@) due to primary radical termination as well as degradative chain-transfer reaction. The overall activation energy and average
value ofk
2
p
/k
t
were 64 kJmol−1 and 0.173 × 10−3 1 mol−1 s−1 respectively 相似文献
57.
In survival or reliability studies, the mean residual life or life expectancy is an important characteristic of the model. Whereas the failure rate can be expressed quite simply in terms of the mean residual life and its derivative, the inverse problem—namely that of expressing the mean residual life in terms of the failure rate—typically involves an integral of a complicated expression. In this paper, we obtain simple expressions for the mean residual life in terms of the failure rate for certain classes of distributions which subsume many of the standard cases. Several results in the literature can be obtained using our approach. Additionally, we develop an expansion for the mean residual life in terms of Gaussian probability functions for a broad class of ultimately increasing failure rate distributions. Some examples are provided to illustrate the procedure. 相似文献
58.
Alick KT Law Deepak Gupta Shawn Levy Douglas C Wallace Robert J McKeon Charles R Buck 《BMC neuroscience》2004,5(1):1
Background
The adenine nucleotide translocator 1 (Ant1) is an inner mitochondrial membrane protein involved with energy mobilization during oxidative phosphorylation. We recently showed that rodent Ant1 is upregulated by transforming growth factor-beta (TGF-β) in reactive astrocytes following CNS injury. In the present study, we describe the molecular mechanisms by which TGF-β1 regulates Ant1 gene expression in cultured primary rodent astrocytes. 相似文献59.
The existing model for multivariate skew normal data does not cohere with the joint distribution of a random sample from a
univariate skew normal distribution. This incoherence causes awkward interpretation for data analysis in practice, especially
in the development of the sampling distribution theory. In this paper, we propose a refined model that is coherent with the
joint distribution of the univariate skew normal random sample, for multivariate skew normal data. The proposed model extends
and strengthens the multivariate skew model described in Azzalini (1985,Scandinavian Journal of Statistics,12, 171–178). We present a stochastic representation for the newly proposed model, and discuss a bivariate setting, which confirms
that the newly proposed model is more plausible than the one given by Azzalini and Dalla Valle (1996,Biometrika,83, 715–726). 相似文献
60.
Raj Gandhi Kamales Kar S. Uma Sankar Abhijit Bandyopadhyay Rahul Basu Pijushpani Bhattacharjee Biswajoy Brahmachari Debrupa Chakraborti M. Chaudhury J. Chaudhury Sandhya Choubey E. J. Chun Atri Desmukhya Anindya Datta Gautam Dutta Sukanta Dutta Anjan Giri Sourendu Gupta Srubabati Goswami Namit Mahajan H. S. Mani A. Mukherjee Biswarup Mukhopadhyaya S. N. Nayak M. Randhawa Subhendu Rakshit Asim K. Ray Amitava Raychaudhuri D. P. Roy Probir Roy Suryadeep Roy Shiv Sethi G. Sigl Arunansu Sil N. Nimai Singh Mark Vagins Urjit Yagnik 《Pramana》2003,60(2):405-409
This is the report of neutrino and astroparticle physics working group at WHEPP-7. Discussions and work on CP violation in
long baseline neutrino experiments, ultra high energy neutrinos, supernova neutrinos and water Cerenkov detectors are discussed. 相似文献