全文获取类型
收费全文 | 1911篇 |
免费 | 68篇 |
国内免费 | 18篇 |
专业分类
化学 | 1420篇 |
晶体学 | 4篇 |
力学 | 17篇 |
数学 | 318篇 |
物理学 | 238篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 26篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 29篇 |
2017年 | 23篇 |
2016年 | 42篇 |
2015年 | 43篇 |
2014年 | 46篇 |
2013年 | 102篇 |
2012年 | 141篇 |
2011年 | 187篇 |
2010年 | 78篇 |
2009年 | 60篇 |
2008年 | 146篇 |
2007年 | 123篇 |
2006年 | 139篇 |
2005年 | 124篇 |
2004年 | 114篇 |
2003年 | 103篇 |
2002年 | 92篇 |
2001年 | 16篇 |
2000年 | 23篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 22篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1971年 | 2篇 |
排序方式: 共有1997条查询结果,搜索用时 203 毫秒
101.
In this paper we study the problem of Hermite interpolation on scattered data using ridge functions, and give a wide class of ridge functions that may be used in practice to interpolate Hermite data. 相似文献
102.
Comparison of phantom materials for use in quality assurance of microbeam radiation therapy
下载免费PDF全文
![点击此处可从《Journal of synchrotron radiation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Matthew Cameron Iwan Cornelius Dean Cutajar Jeremy Davis Anatoly Rosenfeld Michael Lerch Susanna Guatelli 《Journal of synchrotron radiation》2017,24(4):866-876
Microbeam radiation therapy (MRT) is a promising radiotherapy modality that uses arrays of spatially fractionated micrometre‐sized beams of synchrotron radiation to irradiate tumours. Routine dosimetry quality assurance (QA) prior to treatment is necessary to identify any changes in beam condition from the treatment plan, and is undertaken using solid homogeneous phantoms. Solid phantoms are designed for, and routinely used in, megavoltage X‐ray beam radiation therapy. These solid phantoms are not necessarily designed to be water‐equivalent at low X‐ray energies, and therefore may not be suitable for MRT QA. This work quantitatively determines the most appropriate solid phantom to use in dosimetric MRT QA. Simulated dose profiles of various phantom materials were compared with those calculated in water under the same conditions. The phantoms under consideration were RMI457 Solid Water (Gammex‐RMI, Middleton, WI, USA), Plastic Water (CIRS, Norfolk, VA, USA), Plastic Water DT (CIRS, Norfolk, VA, USA), PAGAT (CIRS, Norfolk, VA, USA), RW3 Solid Phantom (PTW Freiburg, Freiburg, Germany), PMMA, Virtual Water (Med‐Cal, Verona, WI, USA) and Perspex. RMI457 Solid Water and Virtual Water were found to be the best approximations for water in MRT dosimetry (within ±3% deviation in peak and 6% in valley). RW3 and Plastic Water DT approximate the relative dose distribution in water (within ±3% deviation in the peak and 5% in the valley). PAGAT, PMMA, Perspex and Plastic Water are not recommended to be used as phantoms for MRT QA, due to dosimetric discrepancies greater than 5%. 相似文献
103.
Application-specific optimization of disordered nanoporous carbons remains a formidable challenge due to the difficulty in
accurately characterizing their microstructures with current empirical methods. Using molecular simulation techniques, we
investigated the adsorptive and diffusive behavior of argon in three models of disordered nanoporous carbons. We found that
the structural and morphological differences between these models gave rise to distinct phenomenological properties. The adsorptive
behavior of argon in both the low and high pressure regimes was enhanced dramatically in the models with more crystalline
microstructures. As for dynamic properties, we found that the adsorbent’s structure and energetic topology significantly alters
the rates of diffusion as well as the characteristics of the underlying diffusion mechanisms. 相似文献
104.
105.
Synthetic studies toward eletefine, a novel stephaoxocane alkaloid, were undertaken in an attempt to provide a general methodology to aid in the synthesis of other novel stephaoxocanes. An efficient construction of the AB ring system with increased functionality is described which presents a flexible approach to synthesizing the C and D rings of eletefine. 相似文献
106.
107.
108.
Jeremy Bernstein 《Physics in Perspective (PIP)》2010,12(1):36-50
I discuss the origin of the idea of making a fusion (hydrogen) bomb and the physics involved in it, and then turn to the design
proposed for one by the unlikely collaborators John von Neumann and Klaus Fuchs in a patent application they filed at Los
Alamos in May 1946, which Fuchs passed on to the Russians in March 1948, and which with substantial modifications was tested
on the island of Eberiru on the Eniwetok atoll in the South Pacific on May 8, 1951. This test showed that the fusion of deuterium
and tritium nuclei could be ignited, but that the ignition would not propagate because the heat produced was rapidly radiated
away. Meanwhile, Stanislaw Ulam and C.J. Everett had shown that Edward Teller’s Classical Super could not work, and at the
end of December 1950, Ulam had conceived the idea of super compression, using the energy of a fission bomb to compress the
fusion fuel to such a high density that it would be opaque to the radiation produced. Once Teller understood this, he invented
a greatly improved, new method of compression using radiation, which then became the heart of the Ulam–Teller bomb design,
which was tested, also in the South Pacific, on November 1, 1952. The Russians have freely acknowledged that Fuchs gave them
the fission bomb, but they have insisted that no one gave them the fusion bomb, which grew out of design involving a fission
bomb surrounded by alternating layers of fusion and fission fuels, and which they tested on November 22, 1955. Part of the
irony of this story is that neither the American nor the Russian hydrogen-bomb programs made any use of the brilliant design
that von Neumann and Fuchs had conceived as early as 1946, which could have changed the entire course of development of both
programs. 相似文献
109.
110.
In this paper we study continuous representations of locally -analytic groups in locally convex -vector spaces, where is a finite extension of and is a spherically complete nonarchimedean extension field of . The class of such representations includes both the smooth representations of Langlands theory and the finite dimensional algebraic representations of , along with interesting new objects such as the action of on global sections of equivariant vector bundles on -adic symmetric spaces. We introduce a restricted category of such representations that we call ``strongly admissible' and we show that, when is compact, our category is anti-equivalent to a subcategory of the category of modules over the locally analytic distribution algebra of . As an application we prove the topological irreducibility of generic members of the -adic principal series for . Our hope is that our definition of strongly admissible representation may be used as a foundation for a general theory of continuous -valued representations of locally -analytic groups.