全文获取类型
收费全文 | 2082篇 |
免费 | 303篇 |
国内免费 | 153篇 |
专业分类
化学 | 1108篇 |
晶体学 | 6篇 |
力学 | 40篇 |
综合类 | 14篇 |
数学 | 53篇 |
物理学 | 1317篇 |
出版年
2023年 | 16篇 |
2022年 | 38篇 |
2021年 | 46篇 |
2020年 | 59篇 |
2019年 | 45篇 |
2018年 | 53篇 |
2017年 | 50篇 |
2016年 | 63篇 |
2015年 | 61篇 |
2014年 | 83篇 |
2013年 | 109篇 |
2012年 | 82篇 |
2011年 | 79篇 |
2010年 | 67篇 |
2009年 | 88篇 |
2008年 | 119篇 |
2007年 | 198篇 |
2006年 | 123篇 |
2005年 | 74篇 |
2004年 | 65篇 |
2003年 | 79篇 |
2002年 | 108篇 |
2001年 | 100篇 |
2000年 | 82篇 |
1999年 | 89篇 |
1998年 | 76篇 |
1997年 | 42篇 |
1996年 | 32篇 |
1995年 | 36篇 |
1994年 | 29篇 |
1993年 | 27篇 |
1992年 | 34篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1976年 | 16篇 |
1975年 | 24篇 |
1974年 | 8篇 |
1973年 | 11篇 |
排序方式: 共有2538条查询结果,搜索用时 46 毫秒
21.
耦合双原子Jaynes-Cummings模型的腔场谱H 总被引:14,自引:8,他引:6
研究了处于激发态的两原子与高Q腔场相互作用单光子过程的腔场谱,给出了初始光场为光子数态、相干态、压缩真空态时的腔场谱数值计算结果,分析了原子间偶极-偶极相互作用强度gα对腔场谱结构的影响.发现真空场Rabi峰,当gα较弱时为4峰,gα较强时为3峰结构;弱场数态(n>0)时为5峰,强场时为3峰结构.相干态和压缩真空态时,谱结构与光子数分布有关,一般为复杂的多峰结构.结果表明,gα对峰位峰高都有影响,破坏了谱结构的对称性,但这种影响只在真空场和弱场时才较明显. 相似文献
22.
23.
Cynthia Kolb Whitney 《Foundations of Physics》2007,37(4-5):788-812
This paper revisits the historical sequence in which some of the major developments of 20th-century physics occurred, and
explores how theories could have turned out differently, if the sequence of developments had been different. It shows how
a delay in founding special relativity theory until after (1) at least one puzzling problem in electromagnetic theory could
be acknowledged, and (2) sat least some of the experimental observations pertinent to the development of quantum mechanics
had become well known, could have resulted in a larger theory that covers both domains in a manner quite different from that
of any of the theories we use today. The revised theory dispenses with a separate postulate introducing Planck’s constant
h, identifying instead a physical mechanism that implies the constant. Some important aspects of quantum chemistry then follow.
Editor, Galilean Electrodynamics, Proceedings of the Natural Philosophy Alliance; Visiting Industry Professor, Tufts University,
retired 相似文献
24.
The constants of binding dye molecules with the micelles of sodium dodecyl sulfate are determined using quenching of delayed fluorescence of acridine dyes by sodium iodide in aqueous–micellar solutions. Kinetic equations have been composed that describe the processes of deactivation of the excited states of dyes. By solving these equations at the concentration of the quencher sodium iodide corresponding to the minimum lifetime of triplet states and at the concentration of micelles corresponding to the least value of the delayed fluorescence quenching rate constants, we obtained the constants of binding dyes with micelles equal to 1.3·107, 2.9·107, and 3.1·107 M–1 for trypaflavine, acridine orange, and acridine yellow, respectively. We calculated the rate constants of quenching of the triplet states of the molecules of dyes by iodide ions (I
–) that decreased in transition from trypaflavine to acridine orange and acridine yellow. 相似文献
25.
R. B. King 《Russian Chemical Bulletin》1993,42(11):1772-1781
Reactions of disodium tetracarbonylferrate, Na2Fe(CO)4, with sterically hindered dialkylaminodichlorophosphines, R2NPCl2 (R2N=diisopropylamino, dicyclohexylamino, and 2,2, 6, 6-tetramethylpiperidino) in diethyl ether lead to the air-stable phosphorus-bridging carbonyl derivatives (R2NP)2COFe2(CO)6 as the major products. The phosphorus-bridging carbonyl group in (i-Pr2NP)2COFe2(CO)6 has been found to undergo the following types of reactions: 1)Reduction, 2)Acylation, 3)Extrusion of the carbonyl group. The mechanisms of the reactions have been considered.This work was presented at the Workshop «The Modern Problems of Heteroorganic Chemistry» held on the ship «Nikolai Bauman» during the period May 8–13, 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1858–1867, November, 1993. 相似文献
26.
Summary Complete Active-Space Self-Consistent-Field (CAS-SCF) calculations for cubic N8 are presented. We studied the N8↔4N2 reaction inD
4h
symmetry and found its energy release and activation barrier with three different atomic basis sets. The energy release for
this reaction is predicted to be around 526 kcal/mol, while the energy barrier to dissociation is estimated about 159 kcal/mol.
These results are in substantial agreement with previousab initio estimates.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
27.
合成了杂多化合物K8[P2W(18)Mo2Co2(H_2O)2O(68)]·MoO6·15H2O,依据XRD、IR、UV-Vis及XPS确定了其晶体结构和配位原子价态,考察了该化合物催化H2O2分解的动力学行为。 相似文献
28.
29.
Ab initio calculations of the orbital and the ground state energies of some open- and closed-shell atoms over Slater type orbitals with quantum numbers integer and Slater type orbitals with quantum numbers noninteger have been performed. In order to increase the efficiency of these calculations the atomic two-electron integrals were expressed in terms of incomplete beta function. Results were observed to be in good agreement with the literature. 相似文献
30.
One novel complex [Co(p-MBA)2(2,2'-bipy)(H2O)]·(H2O) has been synthesized by the reaction of p-methylbenzoic acid with 2,2'-bipyridine in the solvent mixture of water and methanol. It crystallizes in triclinic, space group P-1 with a=0.70479(14), b=1.1211(2), c=1.6718(3) nm, α=103.806(3), β=90.795(3), γ=104.207(3)°, V=1.2399(4) nm3, Mr=512.41, Dc=1.373 g/cm3, Z=2, F(000)=532, μ=0.733 mm-1, R=0.0432 and wR=0.0957. The crystal structural analysis shows that the cobalt atom is coordinated with three oxygen atoms from two p-methylbenzoic acids and one water molecule and two nitrogen atoms from one 2,2'-bipyridine,forming a distorted square-pyramidal coordination geometry. The cyclic voltammetry behavior of the complex is also reported. 相似文献