全文获取类型
收费全文 | 47120篇 |
免费 | 1530篇 |
国内免费 | 146篇 |
专业分类
化学 | 25165篇 |
晶体学 | 225篇 |
力学 | 1156篇 |
综合类 | 6篇 |
数学 | 7547篇 |
物理学 | 14697篇 |
出版年
2023年 | 288篇 |
2021年 | 364篇 |
2020年 | 561篇 |
2019年 | 429篇 |
2018年 | 571篇 |
2017年 | 550篇 |
2016年 | 1179篇 |
2015年 | 911篇 |
2014年 | 1034篇 |
2013年 | 2142篇 |
2012年 | 2019篇 |
2011年 | 2202篇 |
2010年 | 1462篇 |
2009年 | 1216篇 |
2008年 | 2051篇 |
2007年 | 1970篇 |
2006年 | 1853篇 |
2005年 | 1707篇 |
2004年 | 1462篇 |
2003年 | 1225篇 |
2002年 | 1058篇 |
2001年 | 1012篇 |
2000年 | 819篇 |
1999年 | 614篇 |
1998年 | 521篇 |
1997年 | 517篇 |
1996年 | 635篇 |
1995年 | 598篇 |
1994年 | 618篇 |
1993年 | 641篇 |
1992年 | 711篇 |
1991年 | 491篇 |
1990年 | 483篇 |
1989年 | 438篇 |
1988年 | 424篇 |
1987年 | 437篇 |
1986年 | 401篇 |
1985年 | 599篇 |
1984年 | 581篇 |
1983年 | 481篇 |
1982年 | 537篇 |
1981年 | 519篇 |
1980年 | 495篇 |
1979年 | 494篇 |
1978年 | 496篇 |
1977年 | 480篇 |
1976年 | 444篇 |
1975年 | 446篇 |
1974年 | 423篇 |
1973年 | 379篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
61.
62.
W. von Oertzen 《Acta Physica Hungarica A》2003,18(2-4):157-170
Nuclear clustering in N = Z nuclei has been studied for many decades. Of particular relevance are states close to the decay thresholds, as described by the Ikeda diagram. Recent interest has focused on loosely bound systems as observed with exotic nuclei. Extreme deformations are simultaneously observed. In the deformed shell model these are referred to as super- and hyper-deformation. Another feature related to clustering is the development of octupole deformations. A possible approach to describe these states is to use explicitly molecular concepts, with neutrons in covalent binding orbits. Examples for molecular structure in beryllium isotopes and in other neutron-rich light nuclei (carbon and neon) are now well established. The predicted chain states in the carbon isotopes are the first example of structures with an axis ratio of 3:1. A threshold diagram for molecular configurations in nuclei with clusters and covalent neutrons can be established. 相似文献
63.
Keller Teichmann Hans Pfeiffer W. Langenbeck A. Reid Heinrich Menzel Th. Höpner W. Mühlsteph M. Ulmann Geib R. E. Liesegang 《Colloid and polymer science》1939,87(1):100-104
Ohne Zusammenfassung 相似文献
64.
65.
66.
67.
A Raney-Ag catalyst was prepared by leaching out aluminium from a Raney Ag-Al alloy with NaOH solution. The kinetics of leaching
has been investigated in a stirred-batch-reactor at various temperatures by using alloy particles of different sizes. The
kinetic model best fitting the experimental results has been determined.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
68.
Kerstin Paech Adrian Dumitru Jürgen Schaffner-Bielich Stefan Schramm Horst Stöcker Gebhard Zeeb Detlef Zschiesche 《Acta Physica Hungarica A》2004,21(2-4):151-156
The measured particle ratios in central heavy-ion collisions are investigated within a chemical and thermal equilibrium chiral SU(3) σ?ω approach. Contrary to the commonly adopted non-interacting gas calculations, the chiral SU(3) model predicts modified effective hadron masses and effective chemical potentials in the medium and a transition to a chirally restored phase at high temperatures or chemical potentials. the influence of three different types of phase transitions is investigated. We show that the deduced freeze-out values considerably depend on the underlying model while the quality of the fit is approximately the same. 相似文献
69.
Starch belongs to the polyglucan group. This type of polysaccharide shows a broad β-relaxation process in dielectric spectra at low temperatures, which has its molecular origin in orientational motions of sugar rings via glucosidic linkages. This chain dynamic was investigated for α(1,4)-linked starch oligomers with well-defined chain lengths of 2, 3, 4, 6, and 7 anhydroglucose units (AGUs) and for α(1,4)-polyglucans with average degrees of polymerization of 5, 10, 56, 70, and so forth (up to 3000; calculated from the mean molecular weight). The activation energy (Ea) of the segmental chain motion was lowest for dimeric maltose (Ea = 49.4 ± 1.3 kJ/mol), and this was followed by passage through a maximum at a degree of polymerization of 6 (Ea = 60.8 ± 1.8 kJ/mol). Subsequently, Ea leveled off at a value of about 52 ± 1.5 kJ/mol for chains containing more than 100 repeating units. The results were compared with the values of cellulose-like oligomers and polymers bearing a β(1,4)-linkage. Interestingly, the shape of the Ea dependency on the chain length of the molecules was qualitatively the same for both systems, whereas quantitatively the starch-like substances generally showed higher Ea values. Additionally, and for comparison, three cyclodextrins were measured by dielectric relaxation spectroscopy. The ringlike molecules, with 6, 7, and 8 α(1,4)-linked AGUs, showed moderately different types of dielectric spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 188–197, 2004 相似文献
70.
The electrochemical reduction of 1-([(4-halophenyl)imino]methyl)-2-naphthols on graphite electrodes was studied using cyclic voltammetry, chronoamperometry, constant-potential coulometry and preparative constant-potential electrolysis techniques. The data revealed that the reduction on graphite was irreversible and followed an EC mechanism. The diffusion coefficients and the number of electrons transferred were determined using the chronoamperometric Cottrell slope and the ultramicro disc Pt-electrode steady-state current. The number of electrons was also determined by bulk electrolysis. The compounds were subjected to constant-potential preparative electrolysis and the electrolysis products were purified and identified by spectroscopic methods. Based on these findings, a mechanism for the electro-reduction process is proposed. 相似文献