全文获取类型
收费全文 | 9429篇 |
免费 | 168篇 |
国内免费 | 55篇 |
专业分类
化学 | 5944篇 |
晶体学 | 82篇 |
力学 | 268篇 |
数学 | 1580篇 |
物理学 | 1778篇 |
出版年
2021年 | 52篇 |
2020年 | 90篇 |
2019年 | 85篇 |
2018年 | 52篇 |
2017年 | 55篇 |
2016年 | 128篇 |
2015年 | 124篇 |
2014年 | 145篇 |
2013年 | 406篇 |
2012年 | 386篇 |
2011年 | 522篇 |
2010年 | 239篇 |
2009年 | 203篇 |
2008年 | 435篇 |
2007年 | 482篇 |
2006年 | 487篇 |
2005年 | 471篇 |
2004年 | 352篇 |
2003年 | 339篇 |
2002年 | 338篇 |
2001年 | 182篇 |
2000年 | 154篇 |
1999年 | 126篇 |
1998年 | 106篇 |
1997年 | 111篇 |
1996年 | 175篇 |
1995年 | 146篇 |
1994年 | 152篇 |
1993年 | 162篇 |
1992年 | 144篇 |
1991年 | 120篇 |
1990年 | 116篇 |
1989年 | 125篇 |
1988年 | 99篇 |
1987年 | 113篇 |
1986年 | 100篇 |
1985年 | 171篇 |
1984年 | 161篇 |
1983年 | 85篇 |
1982年 | 139篇 |
1981年 | 123篇 |
1980年 | 115篇 |
1979年 | 124篇 |
1978年 | 120篇 |
1977年 | 104篇 |
1976年 | 110篇 |
1975年 | 118篇 |
1974年 | 118篇 |
1973年 | 131篇 |
1972年 | 55篇 |
排序方式: 共有9652条查询结果,搜索用时 15 毫秒
1.
2.
Michael K. Kinyon Kenneth Kunen J. D. Phillips 《Proceedings of the American Mathematical Society》2002,130(3):619-624
An A-loop is a loop in which every inner mapping is an automorphism. A problem which had been open since 1956 is settled by showing that every diassociative A-loop is Moufang.
3.
H E Cline W E Lorensen R J Herfkens G A Johnson G H Glover 《Magnetic resonance imaging》1989,7(1):45-54
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting. 相似文献
4.
J. R. Lindle W. W. Bewley I. Vurgaftman J. R. Meyer J. L. Johnson M. L. Thomas W. E. Tennant 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):558
A self-referencing, optical modulation technique was used to measure the negative luminescence efficiencies of an array of mid-wave infrared HgCdTe photodiodes with cutoff wavelength 4.6 μm as a function of sample temperature. The internal efficiency at a wavelength of 4 μm was 93% at 295 K, and nearly independent of temperature in the 240–300 K range. This corresponds to an apparent temperature reduction >50 K at room temperature and >30 K at 240 K. Moreover, the reverse-bias saturation current density was only 0.13 A/cm2. The measured transmission and emission spectra were simulated using empirical HgCdTe absorption formulas from the literature. 相似文献
5.
Rachel L. McSwain Alison R. Markowitz Kenneth R. Shull 《Journal of Polymer Science.Polymer Physics》2004,42(20):3809-3821
To develop a greater understanding of interfacial interactions between a semicrystalline polymer and a glassy polymer, adhesion tests were performed on very thin layers of poly(ethylene oxide) (PEO) sandwiched between two layers of poly(tetramethyl bisphenol A polycarbonate) (TMPC). The tests were designed to provide intimate contact between the surfaces while they were heated above the melting point of the PEO and cooled back to room temperature. A contact mechanics approach, based on the Johnson, Kendall, and Roberts theory, was used to determine values of the energy release rate describing the energetic driving force for crack propagation within the interfacial region. The ability to measure crack propagation at large values of the energy release rate was limited by rupture of the silicone elastomer that was used to provide a sufficiently compliant matrix for the adhesion experiment. By cycling the tensile stress at relatively low loading levels, we were able to measure fatigue crack propagation at values of the energy release rate that did not result in failure of the elastomer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3809–3821, 2004 相似文献
6.
Kenneth Weber Vilmar Trevisan Luiz Felipe Martins 《Journal of Algorithms in Cognition, Informatics and Logic》2005,54(2):152-167
This paper describes the first algorithm to compute the greatest common divisor (GCD) of two n-bit integers using a modular representation for intermediate values U, V and also for the result. It is based on a reduction step, similar to one used in the accelerated algorithm [T. Jebelean, A generalization of the binary GCD algorithm, in: ISSAC '93: International Symposium on Symbolic and Algebraic Computation, Kiev, Ukraine, 1993, pp. 111–116; K. Weber, The accelerated integer GCD algorithm, ACM Trans. Math. Softw. 21 (1995) 111–122] when U and V are close to the same size, that replaces U by (U−bV)/p, where p is one of the prime moduli and b is the unique integer in the interval (−p/2,p/2) such that . When the algorithm is executed on a bit common CRCW PRAM with O(nlognlogloglogn) processors, it takes O(n) time in the worst case. A heuristic model of the average case yields O(n/logn) time on the same number of processors. 相似文献
7.
8.
The hyperfine constants for muonium in elemental and binary inorganic solids suggest formation of three different families
of defect centre, with distinct electronic structures. The overall range of values, spanning nearly five orders of magnitude,
and their correlation with host properties such as band gap and electron affinity, reveal a deep-to-shallow instability which
has profound implications for the electrical properties of hydrogen impurity in electronic materials, both semiconducting
and dielectric. 相似文献
9.
B. M. Azizur Rahman A. K. M. Saiful Kabir Muttukrishnan Rajarajan Kenneth T. V. Grattan 《Optical and Quantum Electronics》2005,37(1-3):171-183
Modal solutions of planar photonic crystal waveguides with rectangular air-holes are presented by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, power confinements, modal hybridness, beat lengths and group velocity dispersions are shown for the fundamental and higher order modes of the quasi-TE and TM polarizations. 相似文献
10.