全文获取类型
收费全文 | 648篇 |
免费 | 68篇 |
国内免费 | 84篇 |
专业分类
化学 | 82篇 |
力学 | 125篇 |
综合类 | 6篇 |
数学 | 194篇 |
物理学 | 393篇 |
出版年
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 23篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 17篇 |
2015年 | 24篇 |
2014年 | 28篇 |
2013年 | 27篇 |
2012年 | 33篇 |
2011年 | 33篇 |
2010年 | 39篇 |
2009年 | 52篇 |
2008年 | 55篇 |
2007年 | 50篇 |
2006年 | 47篇 |
2005年 | 55篇 |
2004年 | 40篇 |
2003年 | 43篇 |
2002年 | 27篇 |
2001年 | 27篇 |
2000年 | 23篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 5篇 |
1996年 | 13篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有800条查询结果,搜索用时 296 毫秒
121.
In this study, we research a higher dimensional flat Friedmann-Robertson-Walker(FRW) universe in Barber's second theory when strange quark matter(SQM) and normal matter(NM) are attached to the string cloud and domain walls. We obtain zero string tension density for this model. We obtain dust quark matter solutions. This result agrees with Kiran and Reddy, Krori et al, Sahoo and Mishra and Reddy. In our solutions the quark matter transforms to other particles over time. We also obtain two different solutions for domain walls with quark and normal matters by using a deceleration parameter. Also, the features of the obtained solutions are discussed and some physical and kinematical quantities are generalized and discussed. Our results are consistent with Yilmaz, Adcox et al and Back et al in four and five dimensions. 相似文献
122.
We prove a case of the conjecture of Douglas, Reinbacher and Yau about the existence of stable vector bundles with prescribed Chern classes on a Calabi–Yau threefold. For this purpose we prove the existence of certain stable vector bundle extensions over elliptically fibered Calabi–Yau threefolds. 相似文献
123.
基于三维旋量Gross-Pitaevskii(GP)方程研究在含时周期性外磁场作用下玻色-爱因斯坦凝聚体的动力学行为.结果显示,在含时周期外磁场的作用下,铁磁态自旋为1的玻色-爱因斯坦凝聚体将发生拓扑形变.当磁场的两个零点进入凝聚体后,自旋向上态的密度布居图在z轴上分别形成向上和向下的凸起.随着磁场的两个零点在凝聚体内逐渐重合,向上和向下的凸起被拉长,最终自旋向上态在z轴上呈线状分布,这与理论分析预测得到的孤立狄拉克弦相对应.最后,通过计算凝聚体的超流涡度给出磁单极的表征图.结果显示,凝聚体在磁场的两个零点处形成正、负磁单极对,分别对应着自旋向上态在z轴上向上和向下的凸起.随着磁场的两个零点重合,正、负磁单极对中的两条狄拉克弦逐渐靠近,之后大约经5 ms,它们完全相连,最终形成孤立的狄拉克弦. 相似文献
124.
125.
126.
Supersymmetric heterotic string models, built from a Calabi-Yau threefold X endowed with a stable vector bundle V, usually start from a phenomenologically motivated choice of a bundle Vv in the visible sector, the spectral cover construction on an elliptically fibered X being a prominent example. The ensuing anomaly mismatch between c2(Vv) and c2(X), or rather the corresponding differential forms, is often ‘solved’, on the cohomological level, by including a fivebrane. This leads to the question whether the difference can be alternatively realized by a further stable bundle. The ‘DRY’-conjecture of Douglas, Reinbacher and Yau in math.AG/0604597 gives a sufficient condition on cohomology classes on X to be realized as the Chern classes of a stable sheaf. In 1010.1644 [hep-th], we showed that infinitely many classes on X exist for which the conjecture is true. In this note, we give the sufficient condition for the mentioned fivebrane classes to be realized by a further stable bundle in the hidden sector. Using a result obtained in 1011.6246 [hep-th], we show that corresponding bundles exist, thereby confirming this version of the DRY-Conjecture. 相似文献
127.
《Physics and Chemistry of Liquids》2012,50(2):157-165
In the Thomas–Fermi (TF) regime, S. Stringari [Phys. Rev. Lett., 77, 2360 (1996)] established the hydrodynamic normal modes of an interacting dilute Bose-condensed fluid confined in an isotropic harmonic trap. Here, we extend this treatment beyond the TF condensate using the work of B. Hu, G. Huang and Y. Ma [Phys. Rev. A, 69, 063608 (2004)] as a starting point. Both numerical results for low-lying eigenfrequencies, for various angular momentum quantum numbers???and n?=?0, and also samples of corresponding eigenfunctions, are presented. Finally, eigenfrequencies are also given for some collective excitations in an axially symmetrical trap. 相似文献
128.
《Journal of Coordination Chemistry》2012,65(24):2731-2738
Three kinds of trinuclear metal string complexes, [Ni3(dpa)4(L1)2]?·?H2O?·?C2H5OH (L1?=?(E)-3-(2-hydroxyl-phenyl)-acrylic acid) (1), [Ni3(dpa)4(L2)2]?·?2C2H5OC2H5 (L2?=?(E)-3-(3-hydroxyl-phenyl)-acrylic acid) (2) and [Ni3(dpa)4(L3)2]?·?3CH2Cl2?·?1.5CH3OH (L3?=?(E)-3-(4-hydroxyl-phenyl)-acrylic acid) (3). (dpa??=?bis(2-pyridyl)amido), have been synthesized. The structures of 1 and 2 have been analyzed by the X-ray single-crystal diffraction showing hydrogen-bonded networks. 相似文献
129.
通过对拱顶储罐罐壁承受轴向载荷、初始几何缺陷及轴压失稳状况研究,指
出在固定顶罐设计、建造和运行各阶段都应进行罐壁轴压稳定性校核. 根据圆柱薄壳稳定性
理论和轴压失稳临界应力数值分析计算结果,提出固定顶罐罐壁轴压稳定性校核方法和数学
模型,并运用回归分析方法建立罐壁轴压失稳临界应力计算公式. 对几种常用规格的拱顶罐
有初始挠度缺陷罐壁轴压稳定性分析表明:随储罐容积和罐壁初始挠度增大,罐壁轴压稳定
性呈减弱趋势. 相似文献
130.
Anirudh Pradhan 《理论物理通讯》2009,51(2):367-374
Some cylindrically symmetric inhomogeneous viscous fluid string cosmological models with magnetic field and cosmological term A varying with time are investigated. To get the deterministic solution, it has been assumed that the expansion (θ) in the model is proportional to the eigen value σ^11 of the shear tensor σ^ij. The value of cosmological constant for the model is found to be small and positive, which is supported by the results from recent supernovae Ia observations. The effect of bulk viscosity is to produce a change in perfect fluid and hence exhibits essential influence on the character of the solution. The physical and geometric properties of the models are also discussed in presence and absence of magnetic field. 相似文献