全文获取类型
收费全文 | 620篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
化学 | 526篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 5篇 |
物理学 | 113篇 |
出版年
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 45篇 |
2011年 | 30篇 |
2010年 | 22篇 |
2009年 | 21篇 |
2008年 | 31篇 |
2007年 | 24篇 |
2006年 | 38篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 16篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1968年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有650条查询结果,搜索用时 15 毫秒
81.
The ground and low-lying excited states of CoCN have been studied by ab initio multireference single and double excitation configuration interaction (MR-SDCI) calculations with Davidson's correction Q and Cowan-Griffin's relativistic corrections. The electronic ground state of CoCN is (3)Phi(i) and the equilibrium geometry is linear with bond lengths of r(e)(Co-C)=1.8540 A and r(e)(C-N)=1.1677 A, substantially different from the experimentally derived values of r(0)(Co-C)=1.8827(7) A and r(0)(C-N)=1.1313(10) A. The first excited state is (3)Delta(i), separated from the ground state by 727 cm(-1). Larger dynamical electron correlation energy for the low-spin (3)Phi state than for the high-spin (5)Phi state makes the (3)Phi state to be the ground state, which is discussed in terms of the differences in natural orbitals. A new spin-orbit interaction scheme between the X (3)Phi(i) and 1 (3)Delta(i) states is proposed. 相似文献
82.
Toru Takagishi Sadatsugu Okuda Nobuhiko Kuroki Hiroshi Kozuka 《Journal of polymer science. Part A, Polymer chemistry》1985,23(8):2109-2116
Measurements have been made of the binding of divalent metal ions, Cu2+, Ni2+, Co2+, and Zn2+ ions, by polyethylenimine (PEI) and its acetyl or alkyl derivatives by the equilibriumdialysis technique. These metal ions, in particular the Cu2+ ion, exhibited tremendously remarkable binding affinity toward PEI. The extent of complexation of the polymer with the metal ions was decreased markedly by acetylation or alkylation of the polymer. PEI with no primary amine showed an appreciable decrease in its affinity for the metal ion. These results indicate the participation of the primary amine of the polymer in the formation of the complex. A cooperative binding isotherm was observed in PEI–metal ion complex formation, suggesting swelling or conformational change of the polymer induced by this coordination process. Binding of the Cu2+ ion by PEI was found to be essentially independent of temperature over the range 5–35°C. 相似文献
83.
The characteristics and applicability of the absorption spectroscopy system using the coherent transition radiation light source have been investigated. The configurations of the system are relatively simple. The operational conditions of an electron linear accelerator have been evaluated. The stability of the light intensity has been within ±2–3% in a wavenumber range of 4–13 cm−1. The light intensity has been found to be more than six orders of magnitude higher than that for the lowest limit for detection. 相似文献
84.
85.
Fusakazu Matsushima Tomohisa Yonezu Takahiro Okabe Kazuko Tomaru Yoshiki Moriwaki 《Journal of Molecular Spectroscopy》2006,235(2):261-264
Frequencies of pure rotational transitions of OH− ion were measured in the 1-5 THz region with a high-precision tunable far-infrared spectrometer. The measured frequencies were analyzed together with the data of infrared measurements to refine rotational parameters. 相似文献
86.
87.
88.
Summary When a d.c. and a h.f. field are perpendicularly superposed in a electrical discharge (p 10–10–4 mm Hg), three types of discharge can exist, classified from the standpoint of d.c. conduction: (1) d.c. glow type, d.c.-dominant discharge with additional ionization by h.f. field; (2) space chargelimited type, the same as the conduction in the floating double probe in a plasma produced by h.f. field; (3) an intermediate stage between the first and second types, herein referred to as transition type. According to our analysis of the transition type at low pressure, the value of in high electric fields can be deduced from the measurement. 相似文献
89.
Cyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, (Me(3)TACD)H (= Me(3)[12]aneN(4)), reacted with [K{N(SiHMe(2))(2)}] in benzene-d(6) to give [K{(Me(3)TACD)SiMe(2)N(SiHMe(2))}] (1) under hydrogen evolution. Single-crystal X-ray diffraction of 1 shows a dinuclear structure in the solid state, featuring a bridging μ-amido and a weak β-agostic Si-H bond. 1,7-Dimethyl-1,4,7,10-tetraazacyclododecane (Me(2)TACD)H(2) (= Me(2)[12]aneN(4)) and (Me(3)TACD)H were reacted with [Sc{N(SiHMe(2))(2)}(3)(thf)] in benzene-d(6) to give [{(Me(2)TACD)SiMe(2)N(SiHMe(2))}Sc{N(SiHMe(2))(2)}] (2) and [(Me(3)TACD)Sc{N(SiHMe(2))(2)}(2)SiMe(2)] (3), respectively. Both compounds are monomeric in solution and X-ray diffraction studies showed the scandium metal centers to be six-coordinate. The scandium alkyl complex [Sc(Me(3)TACD)(CH(2)SiMe(3))(2)] (4) was obtained by reacting (Me(3)TACD)H with [Sc(CH(2)SiMe(3))(3)(thf)] in benzene-d(6). The scandium amide complexes 2 and 3 catalyzed the ring-opening polymerization (ROP) of meso-lactide to give syndiotactic polylactides. 相似文献
90.
Neil C. Concibido Tetsuji Okuda Wataru Nishijima Mitsumasa Okada 《Reaction Kinetics and Catalysis Letters》2006,89(2):369-376
Summary The hydrodechlorination of tetrachloroethylene in methanol (MeOH) over palladium catalysts on activated carbon (Pd/C) at 20°C
and atmospheric pressure was rendered safer by using ethanol (EtOH), isopropanol (IPA) or water-alcohol mixtures as solvents.
Adding water to MeOH was better than using EtOH or IPA since it resulted in a faster reaction and better stability of Pd/C,
which could also be completely reactivated. 相似文献