全文获取类型
收费全文 | 547篇 |
免费 | 178篇 |
国内免费 | 45篇 |
专业分类
化学 | 179篇 |
晶体学 | 19篇 |
力学 | 20篇 |
综合类 | 3篇 |
数学 | 15篇 |
物理学 | 534篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 21篇 |
2019年 | 14篇 |
2018年 | 25篇 |
2017年 | 24篇 |
2016年 | 33篇 |
2015年 | 26篇 |
2014年 | 28篇 |
2013年 | 67篇 |
2012年 | 33篇 |
2011年 | 38篇 |
2010年 | 25篇 |
2009年 | 40篇 |
2008年 | 26篇 |
2007年 | 33篇 |
2006年 | 33篇 |
2005年 | 33篇 |
2004年 | 37篇 |
2003年 | 32篇 |
2002年 | 18篇 |
2001年 | 28篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有770条查询结果,搜索用时 109 毫秒
761.
762.
763.
764.
WU Yueliang 《中国科学A辑(英文版)》2000,43(9):988-995
The gauge model withSO(3)
F
. flavor symmetry and three Higgs triplets is studied. We show how the intriguing nearly degenerate neutrino mass and bi-maximal
mixing scenario comes out naturally after spontaneous breaking of the symmetry. The hierarchy between the neutrino mass-squared
differences, which is needed for reconciling both solar and atmospheric neutrino data, naturally results from an approximate
permutation symmetry. The model can also lead to interesting phenornena on lepton-flavor violations via theSO(3)
F
gauge interactions. 相似文献
765.
铁电换弹材料常在极化下工作,其性能受材料的微结构直接影响。铁电材料在自极化过程中自变形和自极化方向的不唯一性,以及多晶材料中存在各种不同方向晶界的不可避免性,使得其自极化稳定构形具有极其复杂的结构。根据铁电铁材料单晶特征,提出在自极化过程中该材料能量密度是变形梯度和电位移向量的非凸函数。并且从能量角度出发,导出角电铁弹材料的自极化稳定构形所应满足的必要条件;得出在自然条件下(即无外力和无外加电场作 相似文献
766.
M. N. Starodubtseva S. N. Cherenkevich G. N. Semenkova 《Journal of Applied Spectroscopy》1999,66(3):473-476
An investigation is made of the chemiluminescence (luminol-dependent and spontaneous) of aqueous solutions of NaNO2 and H2O2 in the pH range of 4.0–9.0. In the presence of luminol at pH>7 the initiator of luminescence is H2O2. At pH<7 the luminescence revealed seems to be initiated by peroxynitric acid (HOONO) produced by the interaction of NaNO2 with H2O2 in weakly acid and acid solutions. Cysteine added to the solution prior to introducing H2O2 completely suppresses luminescence development in the pH range investigated. Moreover, cysteine quenches the luminescence
already developed. Mannite and ethanol do not exert a substantial influence on the development of the luminescence. The solution
of NaNO2 and H2O2 is also characterized by spontaneous chemiluminescence, the intensity of which is one-two orders of magnitude lower than
that of the luminol-dependent chemiluminescence. The intensity of the spontaneous chemiluminescence of the solutions of NaNO2 and H2O attains its maximum in the pH region of 6.5 to 7.0. It is assumed that the revealed spontaneous luminescence of the solutions
of NaNO2 and H2O2 is also attributable to formation of peroxynitrit acid in an activated state (HOONO*).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 436–440, May–June, 1999. 相似文献
767.
The dynamics of formation of optical radiation in spectral lines in a longitudinal nanosecond helium discharge under conditions
of wave breakdown is investigated. A discharge tube with a diameter of 0.4 cm and a length of 50 cm was placed in a metallic
shield 1 cm in diameter. The gas pressure was varied within 1–60 torr for an amplitude of the voltage pulses of up to 50 kV.
Asymmetry of spontaneous radiation recorded from different ends of the discharge tube is detected. This is shown to be a consequence
of nonuniform distribution of the functions of the primary brightness of the flux and the absorption coefficient along the
tube length.
Dagestan State University, 43a, M. Gadzhiev Str., Makhachkala, 367025, Russia. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 66, No. 3, pp. 415–420, May–June, 1999. 相似文献
768.
With the variational-cumulant expansion (VCE) method, the critical temperature and spontaneous magnetization of the spatially anisotropic XY model are calculated up to the fourth order. The variational parameter is determined by the complete variational method and the results are compared with both the Monte Carlo results and the self-consistent harmonic approximation (SCHA) results. It is shown that the VCE method can give a better result than the SCHA method when the coupling between adjacent layers is small. 相似文献
769.
利用x射线衍射及磁测量手段研究了Ho2AlFe16-xMnx系列化合物的结构.结果表明,该系列化合物具有Th2Ni17型结构;随着x的增加,化合物的单胞体积呈现非线性的变化,结合磁测量结果分析认为,在化合物的磁相变点附近存在较大的正的本征磁致伸缩.在160—285K温度范围内对Ho2AlFe14Mn2化合物进行的变温x射线衍射研究表明,该化合物在其居里点附近(220—270K)具有负热膨胀性质,其平均热膨胀系数为-14×10-4/K.
关键词:
Ho2AlFe16-xMnx化合物
负热膨胀
本征磁致伸缩 相似文献
770.
Yoichiro Nambu and the Concept of Apparent Vacuum: A Stepping Stone to Spontaneous Symmetry Breaking
Rocco Gaudenzi 《Annalen der Physik》2023,535(2):2200584
The processes of discovery and concept formation are as mysterious as they are intriguing. In this article, they give a sketch of Yoichiro Nambu's long path toward the concept of spontaneous symmetry breaking focusing on the pivotal role played by his notion of “apparent vacuum”. This is instrumental to draw the original analogical correspondence between the vacuum of quantum field theory and solid matter, which, transforming over time in its use and purpose, enables Nambu to arrive at the concept of spontaneous symmetry breaking. From this historical episode they draw a methodological lesson and emphasise the broad cultural influences that conditioned the conceptual development. 相似文献