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991.
992.
Factor, cluster and self-organizing map analyses were performed for the stability constants of complexes of 24 metal ions and hydrogen with 3960 ligands (15606 values of log K1). Five factors reproduce 89% of data variability. Both direct clusterization and clusterization on the basis of factor analysis established the existence of six different classes of similar cations. The similarity series for metal ions and relative similarity of several ions are discussed and the Kohonen two-dimensional map, which visually represents the similarity, is presented. 相似文献
993.
E. Fanelli G. Poeti G. Albertini O. Francescangeli G. Torquati P. Mariani 《Il Nuovo Cimento D》1990,12(1):69-78
Summary Since few years, we have been studying the synthesis and the physical properties of homologous series with the following general
structure: CH3-(CH2)
m
-CO-C6H4-N=N-C6H4-O-CO-(CH2)
n
-CH3, withn ranging from zero to sixteen. In this work we report the results of the diffractometric study of the liquid crystalline series
4-butanoyl-4′-n-alkanoyloxy azobenzenes (m=2) and 4-pentanoyl-4′-n-alkanoyloxy azobenzenes (m=3): in particular all the ordered smectic phases of them=3 series have been identified and some structural parameters are discussed. Considering the smecticA phase, we have determined the layer thickness as a function ofn for both them=2 andm=3 series: the results have been compared with those of the homologous series withm=0 andm=1. In particular an appreciable decrease of the thickness increment due to a CH2 group and a corresponding increase of the thickness of aromatic sublayer were observed: these results are interpreted by
means of a proposed model.
Riassunto Da alcuni anni si stanno studiando la sintesi e le proprietà fisiche di alcune serie omologhe aventi la seguente struttura generale: CH3-(CH2) m -CO-C6H4-N=N-C6H4-O-CO-(CH2) n -CH3, conn variabile da zero a sedici. In questo lavoro vengono descritti i risultati di uno studio diffrattometrico della serie liquido cristallina dei 4-butanoil-4′-n-alkanoilossi azobenzeni (m=2) e dei 4-pentanoil-4′-n-alkanoilossi azobenzeni (m=3): in particolare le fasi smettiche ordinate della seriem=3 sono state identificate e ne vengono discussi i parametri strutturali. Per quanto riguarda la fase smetticaA, abbiamo misurato lo spessore degli strati in funzione din sia nella seriem=2 chem=3: i risultati ottenuti sono stati confrontati con quelli delle serie omologhe conm=0 em=1. In particolare sono state osservate un'apprezzabile diminuzione dell'incremento dello spessore dovuto al gruppo CH2 ed un corrispondente aumento dello spessore del substrato aromatico: il modello che viene proposto permette di interpretare tali fenomeni.
Резюме В течение нескольких лет мы исследовали синтез и физические свойства гомологических рядов со следующей структурой: CH3-(CH2) m -CO-C6H4-N=N-C6H4-O-CO-(CH2) n -CH3, гдеn находится в области от 0 до 16. В этой работе мы приводим результаты дифрактометрических исследований жидких кристаллических соединений сm=2 сm=3, в частности, индентифицируются все упорядоченные смектические фазы дляm=3 и обсуждаются некоторые структурные параметры. Рассчитывая смектическуюА фазу, мы определяем зависимость толщины слоя от для рядов сm=2 и сm=3. Полученные результаты сравниваются с результатами для гомологических рядов сm=0 и сm=1. В частности, наблюдается заметное уменьшение приращения толщины, обусловленное группой CH2, и соответствующее увеличение толщины ароматического подслоя. Полученные результаты интерпретиружтся с помощью предложенной модели.相似文献
994.
G. Barbero L.R. Evangelista N.V Madhusudana 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):327-331
We analyse the influence of adsorbed ions and the resulting surface electric field and its gradient on the anchoring properties
of nematics with ionic conductivity. We take into account two physical mechanisms for the coupling of the nematic director
with the surface electric field: (i) the dielectric anisotropy and (ii) the coupling of the quadrupolar component of the flexoelectric
coefficient with the field gradient. It is shown that for sufficiently large fields near saturated coverage of the adsorbed
ions, there can be a spontaneous curvature distortion in the cell even when the anchoring energy is infinitely strong. We
also discuss the director distortion when the anchoring energy of the surface is finite.
Received: 29 September 1997 / Received in final from: 10 November 1997 / Accepted: 18 November 1997 相似文献
995.
N. Ozawa 《Surface science》2006,600(18):3550-3554
We investigate the quantum mechanical behavior of adsorbed hydrogen (H, D, T) on Cu(1 0 0) and (1 1 0) surfaces. We construct potential energy surfaces (PESs) for the motion of the hydrogen H atom on Cu(1 0 0) and (1 1 0) surfaces within the framework of density functional theory. The potential energy takes a minimum value on the hollow site of Cu(1 0 0) and on the short bridge site of Cu(1 1 0). Moreover, we calculate the quantum states of hydrogen atom motion on these calculated PESs. The ground state wave function of the hydrogen atom motion is strongly localized around the hollow site on the Cu(1 0 0) surface. On the other hand, the ground state wave function of the hydrogen atom motion on Cu(1 1 0) is distributed from the short bridge site to two neighboring pseudo-threefold sites. We finally show isotope effects on the quantum states of the motion of hydrogen on both surfaces. 相似文献
996.
本文介绍了X射线荧光光谱透射强度比测定中等可变厚度金属镀层的组分方法。采用镀层元素强度和基片透射强度之比对镀层元素镀布分量制作工作曲线。 相似文献
997.
金属Zn液态结构变化的研究 总被引:2,自引:0,他引:2
利用TB模型给出的原子间相互作用势详细计算了不同温度下Zn的双体分布函数g(r),结果发现随着温度的不断降低,液态金属Zn的g(r)第一峰变得高而尖,第二峰由弱变强,说明了液态金属Zn的有序度随温度降低而不断增强;利用键对分析技术统计了液态金属Zn在不同温度下的键取向序参数、键对数。键取向序参数及键对数随温度的变化,进一步证明了低温液态的有序度高于高温液态,从而充分说明液态金属在不同温度下有不同的结构形式,而不像人们想象得那样杂乱无章。 相似文献
998.
以1.06μm激光为基频光,测量了金、铜、铂、银膜的反射二次谐波随基频光偏振角的变化,在b=-1的条件下拟合求得了这几种样品面谐波电流的唯象参数“a”值。 相似文献
999.
The photodissociation spectroscopy of weakly bonded bimolecular complexes can give important insight into fundamental molecular interactions and dynamics. We have applied these techniques to a study of metal ion‐ethylene interactions in the Mg+(3s)‐C2H4 and Al+(3s2)‐C2H4 π‐bonded complexes. Experimental work is supported by ab‐initio electronic structure calculations. These experiments allow us to explore and compare the chemical binding, electronic structure, and nonadiabatic dissociation dynamics of these complexes. 相似文献
1000.
The synthesis and structures of five new compounds are reported. [Mg(6‐Oq)2(phen)2] ( 1 ), [Na(phen)3][(6‐HOq)(6‐Oq)] ( 2 ), 1/∞[Cu(3‐Opy)(3‐HOpy)2(PPh3)]∞ ( 3 ), 1/∞[Cu2{μ‐(6‐Oq)}(PPh3)2]∞ ( 4 ) and [Cu2(pht)2(μ‐dppm)2] ( 5 ) (6‐HOq = 6‐hydroxyquinoline; phen = 1,10‐phenanthroline, 3‐HOpy = 3‐hydroxypyridine; Hpht = phthalimide; dppm = bis‐(diphenylphosphino)methane) were prepared by deprotonation of N‐heterocyclic aromatic compounds with metal alkoxides. 1 – 5 represent useful starting materials for investigating the supramolecular cordination chemistry of organic anhydrides. 相似文献