全文获取类型
收费全文 | 562篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 299篇 |
晶体学 | 7篇 |
力学 | 15篇 |
数学 | 32篇 |
物理学 | 212篇 |
出版年
2019年 | 3篇 |
2018年 | 4篇 |
2014年 | 5篇 |
2013年 | 24篇 |
2012年 | 11篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 3篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 28篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1937年 | 3篇 |
排序方式: 共有565条查询结果,搜索用时 0 毫秒
1.
S. Moss de Oliveira P. M. C. de Oliveira F. C. de Sá Barreto 《Journal of statistical physics》1995,78(5-6):1619-1627
Using the finite-size scaling renormalization group, we obtain the two-dimensional flow diagram of the Blume-Capel model forS=1 andS=3/2. In the first case our results are similar to those of mean-field theory, which predicts the existence of first- and second-order transitions with a tricritical point. In the second case, however, our results are different. While we obtain in theS=1 case a phase diagram presenting a multicritical point, the mean-field approach predicts only a second-order transition and a critical endpoint. 相似文献
2.
Gabor Schmera Adi Bulsara David Pierson Frank Moss Enrico Di Cera 《Journal of statistical physics》1993,71(5-6):1179-1190
We consider the class of experiments which can be characterized by a Fokker-PIanck dynamics corresponding to the overdamped motion of a state point in a suitable stochastic potential. We assume that the general form of the potential is known (or can be guessed with reasonable accuracy), but that its parameters are to be determined experimentally by measurements made with a noisy instrument. This possible method for determining the potential parameters, which exploits the system's own internal stochastic motion in order to explore rapidly its available parameter space, is substantially more efficient than traditional methods involving time averages of single point measurements, and yet does not appear to have been previously considered. The method could be important when, for example, the experiment must be completed in a limited time owing either to the expense of the experimental materials or to the temporary stationarity of the preparation, situations which are commonly encountered in experimental biochemistry and biology. 相似文献
3.
Mary Beth Walsh Connie M. Moss Benny G. Johnson Dale A. Holder Jeffry D. Madura 《The Chemical Educator》2002,7(6):379-383
The need for improved interactive tutoring capabilities in educational software for chemistry problem solving is an important one clearly articulated by teachers and students. To deliver the next generation of individualized interactive capabilities users demand, it is necessary to go beyond the conventional computer-assisted instruction methodology. The focus of this paper is the assessment with first-semester general chemistry students of a recently developed artificial intelligence (AI) tutor for balancing chemical equations. This is the first such assessment of an AI-based learning tool in chemistry. Students in CHEM 121 in the Fall 2001 semester at Duquesne University (N = 273) participated in the study. Students were divided into a test group that used the AI tutor as part of their study activities and a control group that did not use the tutor. It was found that the tutor improved the performance of the test group students to a statistically significant degree, helping the weakest students the most. This study establishes the feasibility of an AI-based approach to creating advanced new tutoring software for chemistry problem solving. Access to a Web-based demonstration of the equation-balancing tutor may be obtained by emailing the corresponding author. 相似文献
4.
5.
RECOVERY OF Escherichia coli K-12 FROM NEAR-ULTRAVIOLET RADIATION-INDUCED MEMBRANE DAMAGE 总被引:2,自引:0,他引:2
Abstract A wild-type Escherichia coli K-12 strain was irradiated with broad-band near-ultraviolet radiation (from Black-Light Blue fluorescent lamps) and after holding at 37°C for various times in a complex recovery medium, was assessed for viability on either complex medium (YENB) or minimal medium containing a high inorganic salt content. A near-ultraviolet radiation fluence was used which reduced the surviving fraction to approximately 10% when assessing for viability on the complex medium plates. A near-ultraviolet radiation induced sensitivity to inorganic salt was observed which was largely recoverable by holding treated cells in a complex recovery medium. The majority of the recovery process occurred in the initial 2 h post-irradiation holding period. No inhibition of the recovery process was produced by adding chloramphenicol (40 μg/m l ) or penicillin G (11 units/m l ) to the recovery medium, indicating that neither protein synthesis nor cell wall synthesis, respectively, were required for recovery. However, by adding bacitracin, an antibiotic which acts in part by inhibiting membrane synthesis, to the recovery medium, an effect on recovery from salt sensitivity was observed. At the concentrations of bacitracin used (0.6 and 0.2 units/m l ), little or no effect was observed on unirradiated cells, but both concentrations decreased the amount of recovery of irradiated cells. These results demonstrate that recovery from near-ultraviolet radiation-induced salt sensitivity occurs, it is independent of cell growth and the effect of bacitracin suggests that membrane synthesis may be required for recovery. 相似文献
6.
Simon A. Butler Gillian W. Harris David S. Moss Beatrice A. Gorinsky Margaret J. Adams Sheila Gover 《Journal of chemical crystallography》1994,24(1):1-3
We report the estimation of random errors in the refinement of the rigid body displacements of the -helices of the enzyme 6-phosphogluconate dehydrogenase. Least-squares refinement of the TLS parameters of the helices has been carried out using X-ray reflection data of 2.1 Å resolution, resulting in anR-factor of 19.5%. Standard deviations were estimated from the normal matrix. The results show that the translational mean-square displacements of nearly all the helices are significant at this resolution. However the libration parameters are only significant when the helices have at least four turns. Screw-rotation tensor values cannot be determined at this resolution. 相似文献
7.
Harmon BA Laird CE Fishman GJ Parnell TA Camp DC Frederick CE Hurley DL Lindstrom DJ Moss CE Reedy RC Reeves JH Smith AR Winn WG Benton EV 《Radiation measurements》1996,26(6):863-880
We present an overview of the Long Duration Exposure Facility (LDEF) induced activation measurements. The LDEF, which was gravity-gradient stabilized, was exposed to the low Earth orbit (LEO) radiation environment over a 5.8 year period. Retrieved activation samples and structural components from the spacecraft were analyzed with low and ultra-low background HPGe gamma spectrometry at several national facilities. This allowed a very sensitive measurement of long-lived radionuclides produced by proton- and neutron-induced reactions in the time-dependent, non-isotropic LEO environment. A summary of major findings from this study is given that consists of directionally dependent activation, depth profiles, thermal neutron activation, and surface beryllium-7 deposition from the upper atmosphere. We also describe a database of these measurements that has been prepared for use in testing radiation environmental models and spacecraft design. 相似文献
8.
9.
Ash WW Band HR Blume HT Camporesi T Chadwick GB Coombes RW Delfino MC Fernandez E Ford WT Gettner MW Goderre GP Groom DE Heltsley BK Hurst RB Johnson JR Lau KH Lavine TL Leedy RE Lippi I Maruyama T Messner RL Moromisato JH Moss LJ Muller F Nelson HN Peruzzi I Piccolo M Prepost R Qi N Read AL Ritson DM Rosenberg LJ Shambroom WD Sleeman JC Smith JG Venuti JP von Goeler E Verdini P Wald HB Weinstein R Wiser DE Zdarko RW 《Physical review letters》1985,55(20):2118-2121
10.
Fernandez E Ford WT Qi N Read AL Smith JG Camporesi T De Sangro R Marini A Peruzzi I Piccolo M Ronga F Blume HT Hurst RB Venuti JP Wald HB Weinstein R Band HR Gettner MW Goderre GP Meyer OA Moromisato JH Shambroom WD Sleeman JC von Goeler E Ash WW Chadwick GB Clearwater SH Coombes RW Kaye HS Lau KH Leedy RE Lynch HL Messner RL Moss LJ Muller F Nelson HN Ritson DM Rosenberg LJ Wiser DE Zdarko RW Groom DE Lee H Delfino MC Heltsley BK Johnson JR Lavine TL Maruyama T Prepost R 《Physical review letters》1985,54(15):1620-1623