全文获取类型
收费全文 | 1558篇 |
免费 | 79篇 |
国内免费 | 8篇 |
专业分类
化学 | 1259篇 |
晶体学 | 5篇 |
力学 | 9篇 |
数学 | 141篇 |
物理学 | 231篇 |
出版年
2023年 | 28篇 |
2022年 | 16篇 |
2021年 | 49篇 |
2020年 | 62篇 |
2019年 | 59篇 |
2018年 | 44篇 |
2017年 | 25篇 |
2016年 | 55篇 |
2015年 | 34篇 |
2014年 | 54篇 |
2013年 | 69篇 |
2012年 | 148篇 |
2011年 | 170篇 |
2010年 | 62篇 |
2009年 | 43篇 |
2008年 | 102篇 |
2007年 | 108篇 |
2006年 | 95篇 |
2005年 | 95篇 |
2004年 | 75篇 |
2003年 | 53篇 |
2002年 | 45篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1896年 | 1篇 |
排序方式: 共有1645条查询结果,搜索用时 312 毫秒
101.
102.
103.
104.
105.
A Genetic Algorithm (GA) is an evolutionary computation technique inspired by the principle of biological evolution via natural
selection. It employs the fundamental components of evolution, such as selection, mating, and mutation, which continue from
generation to generation, creating better solutions as time progresses. Although it is mostly used as an optimization tool,
GA enjoys a wide spectrum of applications in diverse fields such as engineering, medicine, and ecology, among others. In this
study, we propose three different population size reduction methods for a typical GA optimization, aiming to increase efficiency.
Additionally, we compare the accuracy and precision of these methods using Monte Carlo simulations. 相似文献
106.
107.
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
108.
This paper concerns the generation of support vector machine classifiers for solving the pattern recognition problem in machine
learning. A method is proposed based on interior-point methods for convex quadratic programming. This interior-point method
uses a linear preconditioned conjugate gradient method with a novel preconditioner to compute each iteration from the previous.
An implementation is developed by adapting the object-oriented package OOQP to the problem structure. Numerical results are
provided, and computational experience is discussed. 相似文献
109.
Van Veldhuizen JJ Garber SB Kingsbury JS Hoveyda AH 《Journal of the American Chemical Society》2002,124(18):4954-4955
The synthesis and structure of a new chiral bidentate imidazolinylidene ligand and a derived chiral Ru-based carbene are disclosed. The Ru complex is stereogenic at the metal center; it can be prepared in >98% diastereoselectivity and purified by silica gel chromatography with undistilled solvents. The air-stable Ru complex efficiently catalyzes ring-closing and ring-opening metathesis and is recyclable. The chiral complex is highly effective (0.5-10 mol % loading) in promoting enantioselective ring-opening/cross metathesis reactions (up to >98% ee). These enantioselective transformations can be effected in air, with unpurified solvent and with substrates that would only polymerize with Mo-based catalysts. 相似文献
110.
The axial resolution of optical coherence tomography images is primarily dependent on the bandwidth of the illumination source. Continuum generation is one way to generate the single-mode, high-bandwidth light needed for point illumination. We present an inexpensive and easy-to-implement augmentation to a Ti:sapphire laser that widens the bandwidth from 20 to over 200 nm with commerically available ultrahigh-numerical-aperture fiber. This technique can provide a readily available broad-bandwidth source for researchers and a practical enhancement to a fiber-optic optical coherence tomography system. 相似文献