全文获取类型
收费全文 | 1218篇 |
免费 | 45篇 |
国内免费 | 4篇 |
专业分类
化学 | 831篇 |
晶体学 | 51篇 |
力学 | 21篇 |
数学 | 72篇 |
物理学 | 292篇 |
出版年
2023年 | 13篇 |
2022年 | 31篇 |
2021年 | 34篇 |
2020年 | 31篇 |
2019年 | 40篇 |
2018年 | 40篇 |
2017年 | 21篇 |
2016年 | 43篇 |
2015年 | 27篇 |
2014年 | 42篇 |
2013年 | 80篇 |
2012年 | 78篇 |
2011年 | 71篇 |
2010年 | 55篇 |
2009年 | 53篇 |
2008年 | 68篇 |
2007年 | 54篇 |
2006年 | 38篇 |
2005年 | 34篇 |
2004年 | 32篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 29篇 |
2000年 | 46篇 |
1999年 | 57篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有1267条查询结果,搜索用时 15 毫秒
991.
In the present work, the new exact solutions of the Boiti-Leon-Pempinelli system have been found. The system has extensive physical background. The exact solutions of the Boiti-Leon-Pempinelli system are investigated using similarity transformation method via Lie group theory. Lie symmetry generators are used for constructing similarity variables for the given system of partial differential equations, which lead to the new system of partial differentiaJ equations with one variable less at each step and eventually to a system of ordinary differential equations (ODEs). Finally, these ODEs are solved exactly. The exact solutions are obtained under some parametric restrictions. The elastic behavior of the soliton solutions is shown graphically by taking some appropriate choices of the arbitrary functions involved in the solutions. 相似文献
992.
S. Renganayaki E. Subramanian S. Shanmuga Sundara Raj Hoong‐Kun Fun 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):349-350
The aromatic ring of the cinnamic moiety in N‐benzyl‐2′‐iodocinnamanilide, C22H18INO, (I), and N‐benzyl‐2′‐iodo‐4′‐methyl‐2‐phenylcinnamanilide, C29H24INO, (II), makes a dihedral angle with the iodophenyl ring of 72.1 (2) and 81.0 (2)° in (I) and (II), respectively. In (I), molecules exist as discrete components, while in (II), they form infinite chains along the b axis, through I?O non‐bonded interactions. 相似文献
993.
Zuoxiang Wang Yurong Zhang Ibrahim Abdul Razak S. Shanmuga Sundara Raj Hoong‐Kun Fun Fengsheng Li Hongchang Song 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):161-162
In the title complex of [Ni(C3H4N2)6](C8H7O3)2, the Ni atom is in an octahedral environment formed by the tertiary N atom of the imidazole moieties. The methoxybenzoate moieties act as a bridge connecting two hexakis(imidazole)nickel(II) molecules through N—H?O hydrogen bonds. 相似文献
994.
Ibrahim Abdul Razak S. Shanmuga Sundara Raj Hoong‐Kun Fun Bohari M. Yamin Norhayati Hashim 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):664-665
In the title compound, [Fe(C5H5)2]2[SbCl4]2[SbCl3], the cyclopentadienyl rings in both cations are parallel, with a nearly eclipsed conformation. The Sb3+ ions are coordinated by six Cl? ions to form octahedral arrangements, of which two are slightly distorted. These octahedra form infinite chains along the c axis through Cl—Sb—Cl bridges. 相似文献
995.
Kum Sang Low Suresh Muniandy Pance Naumov S. Shanmuga Sundara Raj Hoong‐Kun Fun Ibrahim Abdul Razak Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):e113-e114
Bis(N,N‐dimethylthiocarbamoylthio)acetic acid, [(CH3)2NC(=S)S]2CHC(=O)OH or C8H14N2O2S4, exists as a centrosymmetric hydrogen‐bonded dimer [O?O 2.661 (3) Å]. 相似文献
996.
Ramis Rao Subramanian Shanmuga S. Anandan Kuan Hiang Kwek Kum Sang Low S. Shanmuga Sundara Raj Hoong‐Kun Fun Ibrahim Abdul Razak John V. Hanna Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):e292-e294
The monoclinic cell of dicyclohexylammonium 2,4‐dichlorophenoxyacetate contains four C12H24N+·C5H8Cl2O3? ion pairs. The ammonium N atom is hydrogen bonded to the oxygen ends of two carboxyl groups to form a 12‐membered O—C—O?HNH?O—C—O?HNH ring. In (2,4‐dichlorophenoxylacetato)bis(triphenylphosphine)silver(I), [Ag(C8H5Cl2O3)(C18H15P)2], the carboxyl CO2 unit chelates to the Ag atom in an anisobidentate manner [Ag—O = 2.436 (2) and 2.517 (2) Å]; the Ag atom shows distorted tetrahedral geometry. 相似文献
997.
S. Shanmuga Sundara Raj Ibrahim Abdul Razak Hoong‐Kun Fun Pu‐Su Zhao Fangfang Jian Xujie Yang Lude Lu Xin Wang 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):e130-e131
In the crystal of the title complex, [Co(C9H6NO)3]·C2H5OH, the central Co atom has a distorted octahedral coordination comprised of three N atoms and three O atoms from the three 8‐quinolinolato ligands. The three Co—O bond distances are in the range 1.887 (2)–1.910 (2) Å, while the three Co—N bond distances range from 1.919 (2) to 1.934 (2) Å. The solvent ethanol molecule forms an intermolecular O—H?O hydrogen bonding with a quinolinolato ligand. 相似文献
998.
S. Shanmuga Sundara Raj Hoong‐Kun Fun Pu‐Su Zhao Fang‐Fang Jian Lu‐De Lu Xu‐Jie Yang Xin Wang 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):742-743
The crystal structure of the title compound, [Zn‐(C7H5O2)2(C5H6N2)2], is built of monomeric [Zn(2‐apy)2(OBz)2] molecules (apy is aminopyridine and OBz is benzoate). The Zn atom lies on a twofold symmetry axis and adopts a slightly distorted tetrahedral coordination. The Zn?O distances to the non‐coordinated O atoms are long at 2.872 (3) Å. Each non‐ligating carbonyl O atom of the benzoate anion accepts one intramolecular and one intermolecular hydrogen bond from the amino group. The molecules form a chain along the c axis through intermolecular N—H?O hydrogen bonds between the amino and carboxyl groups. 相似文献
999.
Seik Weng Ng S. Shanmuga Sundara Raj Hoong‐Kun Fun Ibrahim Abdul Razak James M. Hook 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):966-968
catena‐Poly[dicyclohexylammonium [tributyltin‐μ‐(4‐oxo‐4H‐pyran‐2,6‐dicarboxylato‐O2:O6)]], (C12H24N)[Sn(C7H2O6)(C4H9)3], consists of 4‐oxo‐4H‐pyran‐2,6‐dicarboxylato groups that axially link adjacent tributyltin units into a linear polyanionic chain. The ammonium counter‐ions surround the chain, and each cation forms a pair of hydrogen bonds to the double‐bond carbonyl O atoms of the same dianionic group. The chain propagates in a zigzag manner along the c axis of the monoclinic cell. In catena‐poly[methyl(phenyl)ammonium [tributyltin‐μ‐(pyridine‐2,6‐dicarboxylato‐O2:O6)]], (C7H10N)[Sn(C7H3NO4)(C4H9)3], the pyridine‐2,6‐dicarboxylato groups also link the tributyltin groups into a chain, but the hydrogen‐bonded chain propagates linearly on the ac face of the monoclinic cell. 相似文献
1000.
S. Thinagar D. Velmurugan S. Shanmuga Sundara Raj Hoong‐Kun Fun S. C. Gupta H. Merazig S. Bouacida 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o181-o183
The title compound 3,3′‐[o‐phenylenebis(methyleneoxy)]bis(6‐chloroflavone), C38H24Cl2O6, (I), crystallizes in the monoclinic space group C2/c, with the molecules lying across twofold rotation axes so that there is half a molecule in the asymmetric unit, while the other title compound, 3,3′‐propylenedioxybis[6‐chloro‐2‐(2‐furyl)‐4H‐1‐benzopyran‐4‐one], C29H18Cl2O8, (II), crystallizes in monoclinic space group P21/n with one molecule in the asymmetric unit. In both compounds, the benzopyran moiety is nearly planar, with dihedral angles between the two fused rings of 1.43 (8)° in (I), and 2.54 (7) and 3.00 (6)° with respect to the benzopyran moieties in the two halves of (II). The furan rings are twisted by 8.3 (1) and 8.4 (1)° in the two halves of (II). In both compounds, the molecular structure is stabilized by intramolecular C—H⃛O hydrogen bonds, while the crystal packing is stabilized by C—H⃛Cl and C—H⃛O intermolecular hydrogen bonds in (I) and (II), respectively. 相似文献