全文获取类型
收费全文 | 2553篇 |
免费 | 118篇 |
国内免费 | 14篇 |
专业分类
化学 | 1401篇 |
晶体学 | 53篇 |
力学 | 96篇 |
综合类 | 3篇 |
数学 | 514篇 |
物理学 | 618篇 |
出版年
2023年 | 19篇 |
2022年 | 37篇 |
2021年 | 44篇 |
2020年 | 65篇 |
2019年 | 91篇 |
2018年 | 108篇 |
2017年 | 90篇 |
2016年 | 118篇 |
2015年 | 79篇 |
2014年 | 117篇 |
2013年 | 279篇 |
2012年 | 158篇 |
2011年 | 158篇 |
2010年 | 167篇 |
2009年 | 129篇 |
2008年 | 177篇 |
2007年 | 141篇 |
2006年 | 99篇 |
2005年 | 76篇 |
2004年 | 78篇 |
2003年 | 89篇 |
2002年 | 55篇 |
2001年 | 52篇 |
2000年 | 43篇 |
1999年 | 18篇 |
1998年 | 21篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 2篇 |
1970年 | 4篇 |
排序方式: 共有2685条查询结果,搜索用时 31 毫秒
181.
182.
Determination of radioactive pollution from an open landfill 总被引:1,自引:0,他引:1
O. Baykara H. Hasar E. Öbek M. Doğru 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(1):95-99
Summary This paper presents a case study of radioactive pollution of groundwater caused by leachate from an open landfill. Alpha- and beta-radioactivity analysis of the leachate from different points in the region and associated fountain water from a village down stream were carried out during four seasons. The alpha- and beta-radioactivity concentrations were under the detection limit in all samples and ranged between 0.07 and 2.17 Bq/l, respectively. The beta-radioactivity concentration from 129I, 137Cs and 90Sr individual radioisotopes were determined and their annual effective dose was calculated. 相似文献
183.
The on-axis scintillation index for a circular dark hollow beam (DHB) propagating in a weak turbulent atmosphere is formulated,
and the scintillation properties of a DHB are investigated in detail. The scintillation index for a DHB reduces to the scintillation
index for a Gaussian beam, an annular beam and a flat-topped beam under certain conditions. It is found that the scintillation
index of a DHB is closely related to the beam parameters and can be lower than that of a Gaussian beam, an annular beam and
a flat-topped beam in a weak turbulent atmosphere at smaller waist sizes and longer propagation lengths.
PACS 42.25.Bs; 42.68.Ay 相似文献
184.
Beam search (BS) is used as a heuristic to solve various combinatorial optimization problems, ranging from scheduling to assembly line balancing. In this paper, we develop a backtracking and an exchange-of-information (EOI) procedure to enhance the traditional beam search method. The backtracking enables us to return to previous solution states in the search process with the expectation of obtaining better solutions. The EOI is used to transfer information accumulated in a beam to other beams to yield improved solutions. 相似文献
185.
Cenap Özel Erol Yılmaz Hünkar Kayhan Aliekber Aktağ 《International Journal of Theoretical Physics》2008,47(12):3101-3107
In this paper, the entanglement properties of a system of two atoms inside an optical cavity in a stochastic interaction with
field are studied by the Jaynes-Cummings Model. The phase telegraph noise is considered as a noise term and an exact solution
to the model is obtained. The solution reveals the resulting decoherence effects of the noise on the entanglement properties
of the system. It shows that under the noise the individual atoms do not entangle with the cavity field. However, a strong
atom-atom entanglement is observed in a stationary state. It is seen that a relatively strong noise is cooperative in the
construction of the steady state atom-atom entanglement. 相似文献
186.
We consider supplier diversification in an EOQ type inventory setting with multiple suppliers and binomial yields. We characterize the optimal policy for the model and show that, in this case, it does not pay to diversify, in contrast to previous results in the random yield literature. 相似文献
187.
We prove a weak upper bound on the coarsening rate of the discrete‐in‐space version of an ill‐posed, nonlinear diffusion equation. The continuum version of the equation violates parabolicity and lacks a complete well‐posedness theory. In particular, numerical simulations indicate very sensitive dependence on initial data. Nevertheless, models based on its discrete‐in‐space version, which we study, are widely used in a number of applications, including population dynamics (chemotactic movement of bacteria), granular flow (formation of shear bands), and computer vision (image denoising and segmentation). Our bounds have implications for all three applications. © 2008 Wiley Periodicals, Inc. 相似文献
188.
Orhan
elli Salih Erzeneo
lu Bekir Gürbulak 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,90(3-4):399-407
Measurements have been made to determine the mass attenuation coefficients of undoped n-type InSe, and Gd, Ho, Er doped n-InSe single crystals using a Si(Li) detector in the energy region 15.746–40.930 keV X-ray energies with energy dispersive X-ray fluorescence systems. InSe, InSe:Gd, InSe:Ho and InSe:Er single crystals were grown by using the stockbarger method. The measured values are graphically compared with the theoretical ones obtained using WinXcom. 相似文献
189.
Avcı Davut Altürk Sümeyye Sönmez Fatih Tamer Ömer Başoğlu Adil Atalay Yusuf Zengin Kurt Belma Dege Necmi 《Molecular diversity》2021,25(1):171-189
Molecular Diversity - The World Health Organization (WHO) report shows that diabetes mellitus (DM) will be one of the ten deadly diseases in the near future. The best way to prevent DM is to... 相似文献
190.
Şengül Dilem Doğan 《Tetrahedron》2017,73(16):2217-2224
A copper-mediated NS bond-forming reaction via NH/SH activation is described. This reaction occurs under mild conditions with high efficiency, step economy, and tolerates a wide variety of functional groups, providing an efficient means of accessing biologically important 1,2,4-benzothiadiazin-3(4H)-ones. 相似文献