全文获取类型
收费全文 | 6055篇 |
免费 | 347篇 |
国内免费 | 52篇 |
专业分类
化学 | 4571篇 |
晶体学 | 44篇 |
力学 | 112篇 |
数学 | 627篇 |
物理学 | 1100篇 |
出版年
2023年 | 24篇 |
2022年 | 66篇 |
2021年 | 116篇 |
2020年 | 94篇 |
2019年 | 110篇 |
2018年 | 96篇 |
2017年 | 90篇 |
2016年 | 199篇 |
2015年 | 185篇 |
2014年 | 218篇 |
2013年 | 373篇 |
2012年 | 428篇 |
2011年 | 503篇 |
2010年 | 306篇 |
2009年 | 238篇 |
2008年 | 402篇 |
2007年 | 351篇 |
2006年 | 359篇 |
2005年 | 304篇 |
2004年 | 284篇 |
2003年 | 241篇 |
2002年 | 213篇 |
2001年 | 108篇 |
2000年 | 101篇 |
1999年 | 73篇 |
1998年 | 53篇 |
1997年 | 51篇 |
1996年 | 62篇 |
1995年 | 52篇 |
1994年 | 49篇 |
1993年 | 32篇 |
1992年 | 32篇 |
1991年 | 26篇 |
1990年 | 38篇 |
1989年 | 36篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 42篇 |
1984年 | 29篇 |
1983年 | 22篇 |
1982年 | 26篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 24篇 |
1976年 | 22篇 |
1975年 | 18篇 |
1973年 | 27篇 |
排序方式: 共有6454条查询结果,搜索用时 15 毫秒
891.
Young L Arms DA Dufresne EM Dunford RW Ederer DL Höhr C Kanter EP Krässig B Landahl EC Peterson ER Rudati J Santra R Southworth SH 《Physical review letters》2006,97(8):083601
We have developed a synchrotron-based, time-resolved x-ray microprobe to investigate optical strong-field processes at intermediate intensities (10(14) - 10(15) W/cm2). This quantum-state specific probe has enabled the direct observation of orbital alignment in the residual ion produced by strong-field ionization of krypton atoms via resonant, polarized x-ray absorption. We found strong alignment to persist for a period long compared to the spin-orbit coupling time scale (6.2 fs). The observed degree of alignment can be explained by models that incorporate spin-orbit coupling. The methodology is applicable to a wide range of problems. 相似文献
892.
893.
We provide explicit constructions of particularly convenient dual pairs of Gabor frames. We prove that arbitrary polynomials
restricted to sufficiently large intervals will generate Gabor frames, at least for small modulation parameters. Unfortunately,
no similar function can generate a dual Gabor frame, but we prove that almost any such frame has a dual generated by a B-spline.
Finally, for frames generated by any compactly supported function φ whose integer-translates form a partition of unity, e.g., a B-spline, we construct a class of dual frame generators, formed
by linear combinations of translates of φ. This allows us to chose a dual generator with special properties, for example, the one with shortest support, or a symmetric
one in case the frame itself is generated by a symmetric function. One of these dual generators has the property of being
constant on the support of the frame generator. 相似文献
894.
Jing-wen Li Zhi-wen Wang Jaeun Lee Moo Young Sohn Zhong-fu Zhang En-qiang Zhu 《应用数学学报(英文版)》2010,26(3):525-528
In this paper we get some relations between α(G), α'(G), β(G), β'(G) and αT(G), βT(G). And all bounds in these relations are best possible, where α(G), α'(G),/3(G), β(G), αT(G) and βT(G) are the covering number, edge-covering number, independent number, edge-independent number (or matching number), total covering number and total independent number, respectively. 相似文献
895.
Zhimin Xie Young‐Jin Yum Chul‐Kyoung Lee 《Journal of Macromolecular Science: Physics》2013,52(3):561-567
It has been known that the carbon black (CB) network is responsible for the electrical and mechanical behaviors of filled rubber. Due to the complexity involved in the filled rubber in relation to the conductive mechanism of the CB network, there has been little work concerned with simulation of the electrical behavior at large strains. Based upon an infinite circuit model, the electrical resistivity of CB filled rubber under elongation is simulated. For CB (N330) filled natural rubber with volume fraction of 27.5%, the simulated electrical resistivity increases with elongation at small stains, corresponding to the breakup of the agglomerates. The reduction in resistivity at larger strains corresponds to the decrease of the junction width, which results in a decrease of the contact resistance. Good agreement is found between the simulations and the experimental data available in the literature. The simulated results confirm the effects of the breakdown of the CB network and the alignment of CB aggregates under strain on the electrical resistivity. 相似文献
896.
Han Mo Jeong Ah Young Jo Mi Yeon Choi Man Jae Han Jae Young Jho 《Journal of Macromolecular Science: Physics》2013,52(5):789-799
The characteristics and performance of an ionic polymer–metal composite (IPMC), prepared with an anion‐exchange acrylic copolymer, was examined. The acrylic copolymer was synthesized by the radical copolymerization of fluoroalkyl methacrylate and 2‐(dimethyl amino)ethyl methacrylate(AMA). Effects of the AMA repeating unit's content in the copolymer and effects of the anion type present on the actuation of the IPMC were observed. The optimal content of 19.4 wt% AMA in the IPMC copolymer yielded the best actuation. The actuation also improved according to the type of anion present in the composite, in the following order: Br???4 ?. 相似文献
897.
Purpose
The purpose of the study was to validate the diagnostic performance of high-resolution isovolumetric magnetic resonance arthrography (MRA) for intrinsic ligament and triangular fibrocartilage complex (TFCC) tears of the wrist as compared to conventional MR imaging (MRI).Materials and methods
Forty-eight patients with traumatic TFCC tears at arthroscopy were enrolled. All patients had underwent proton-density- and T2-weighted MRI before arthrography and three-dimensional T1 high-resolution isovolumetric examination (3D-THRIVE) MRA on a 3-T MR. We assessed the presence of scapholunate interosseous ligament (SLIL)/lunotriquetral interosseous ligament (LTIL) or TFCC tears using the arthroscopy as a gold standard.Results
Arthroscopy revealed 37 TFCC central tears, 15 TFCC peripheral tears, 20 SLIL tears and 13 LTIL tears. Sensitivities of MRI and MRA were 70.3% and 94.6% for detection of TFCC central tears, 60.0% and 93.3% for detection of TFCC peripheral tears, 65.0% and 85.0% for SLIL tears, and 61.5% and 84.6% for LTIL tears. The specificity of the MRI was 100% for the detection of ligaments and TFCC tears. The specificities of the MRA for detection of TFCC central tears, TFCC peripheral tears, SLIL tears and LTIL tears were 100%, 97%, 96.4% and 100%, respectively.Conclusion
Isovolumetric 3D-THRIVE wrist MRA provided better results for depiction of intrinsic ligament and TFCC tears than wrist MRI. 相似文献898.
Jin Wang Eric Landahl Timothy Graber Reinhart Pahl Reinhart Pahl Linda Young 《Synchrotron Radiation News》2013,26(4):24-31
Scientific research in the time domain using the pulsed structure of the X-ray beams from a third-generation synchrotron source, such as the Advanced Photon Source (APS), has become a major interest among synchrotron users. The traditional material science, chemistry, and biology communities are getting an early glimpse of the potential impact of fast time-resolved X-ray studies. The scientific disciplines that have benefited from these studies include atomic and molecular physics, biology, chemical science, condensed matter physics, engineering science, environmental science, material science, and nuclear science. Technically, the turn-key-type femtosecond (fs) optical lasers with high peak power, used as pumps in many X-ray pump-probe experiments, have only recently become available. 相似文献
899.
900.
H. Andrew Michener David C. Dettman James M. Ekman Young C. Choi 《The Journal of mathematical sociology》2013,37(4):307-330
This article reports a test of theories of payoff allocation in n‐person game‐theoretic systems. An experimental study was conducted to test the relative predictive accuracy of three solution concepts (imputation set, stable set, core) in the context of 4‐person, 2‐strategy non‐sidepayment games. Predictions from each of the three solution concepts were computed on the basis of both α‐effectiveness (von Neumann‐Morgenstern) and β‐effectiveness (Aumann), making a total of six predictive theories under test. Two important results emerged. First, the data show that the g‐imputation set was more accurate than the a‐imputation set, the β‐stable set was more accurate than the α‐stable set, and the (3‐core was more accurate than the α‐core; in other words, for each of the solutions tested, the prediction from any solution concept based on (β‐effectiveness was more accurate than the prediction from the same solution based on a‐effectiveness. Second, the β‐core was the most accurate of the six theories tested. Results are interpreted as showing that β‐effectiveness is superior to a‐effectiveness as a basis for payoff predictions in cooperative non‐sidepayment games. 相似文献