全文获取类型
收费全文 | 37294篇 |
免费 | 1110篇 |
国内免费 | 5篇 |
专业分类
化学 | 20867篇 |
晶体学 | 169篇 |
力学 | 771篇 |
综合类 | 1篇 |
数学 | 6110篇 |
物理学 | 10491篇 |
出版年
2023年 | 201篇 |
2021年 | 284篇 |
2020年 | 475篇 |
2019年 | 314篇 |
2018年 | 432篇 |
2017年 | 413篇 |
2016年 | 962篇 |
2015年 | 828篇 |
2014年 | 919篇 |
2013年 | 2040篇 |
2012年 | 1556篇 |
2011年 | 1900篇 |
2010年 | 966篇 |
2009年 | 804篇 |
2008年 | 1822篇 |
2007年 | 1792篇 |
2006年 | 1577篇 |
2005年 | 1383篇 |
2004年 | 1097篇 |
2003年 | 943篇 |
2002年 | 898篇 |
2001年 | 747篇 |
2000年 | 669篇 |
1999年 | 446篇 |
1998年 | 401篇 |
1997年 | 400篇 |
1996年 | 504篇 |
1995年 | 450篇 |
1994年 | 470篇 |
1993年 | 552篇 |
1992年 | 450篇 |
1991年 | 343篇 |
1990年 | 382篇 |
1989年 | 310篇 |
1988年 | 323篇 |
1987年 | 325篇 |
1986年 | 295篇 |
1985年 | 467篇 |
1984年 | 453篇 |
1983年 | 421篇 |
1982年 | 432篇 |
1981年 | 438篇 |
1980年 | 400篇 |
1979年 | 364篇 |
1978年 | 404篇 |
1977年 | 386篇 |
1976年 | 333篇 |
1975年 | 319篇 |
1974年 | 305篇 |
1973年 | 314篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
A. Botvina I. N. Mishustin M. Blann M. G. Mustafa G. Peilert H. Stöcker W. Greiner 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(3):297-303
Comparative analysis of three typical models of nuclear disintegration, the statistical multifragmentation model (SMM), the quantum statistical model (QSM) and a generalized evaporation model (GEM), is carried out. The thermodynamical properties of a decaying system as well as observable characteristics in heavy ion collisions predicted by the different models are discussed. It is shown that these models yield quite similar results for low charge yields at higher excitation energies (E/A>6 MeV per nucleon) and it is suggested that the coincidence measurements of the intermediate mass fragment multiplicity and the neutron and proton multiplicity (or alternatively, the total bound charge) may be very useful for deducing the decay mechanism. The GEM is shown to differ from the other models in predicting a high Z residue peak. 相似文献
993.
D. Seweryniak B. Cederwall J. Nyberg C. Fahlander A. Johnson A. Kerek J. Kownacki L. -O. Norlin E. Adamides A. Atac J. Blomqvist H. Grawe E. Ideguchi R. Julin S. Juutinen W. Karczmarczyk S. Mitarai M. Piiparinen R. Schubart G. Sletten S. Törmänen A. Virtanen 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(2):243-244
Neutron deficient nuclei close to 100Snhave been investigated in-beam by γ-ray spectroscopic methods using the NORDBALL detector array. A beam of 270 MeV 58Niwas used to bombard a target of 54Fe.Reaction channel separation was achieved with a 4π charged particle multidetector setup together with a 1π neutron detector wall placed in the forward direction. Excited states of 102Inwere identified for the first time. The level scheme constructed from γ-γ-particle-coincidence and γ-γ-angular correlation analysis is presented. The structure of 102 In is discussed and compared to neighboring nuclei in the framework of the nuclear shell-model. 相似文献
994.
V. Hamacher J. Wrachtrap B. von Maltzan M. Plato K. Möbius 《Applied magnetic resonance》1993,4(3):297-319
The triplet states of several substituted porphyrins (Tetraphenylporphyrin (H2TPP), Zinc-Tetramethylporphyrin (ZnTMP), Octaethylporphyrin (H2OEP) and the Dication of H2TPP (H4TPP2+)) and two covalently linked dimers with H2TPP-subunits in disordered solid solution were studied by EPR and ENDOR at liquid helium temperature. The measurement yields theA zz component of the hyperfine tensors of all α-protons in the reference frame of the zero field splitting tensor. Dipolar and isotropic contributions toA zz are discussed and spin densities derived. The spin densities are compared with results of all-valence-electrons self-consistent field molecular orbital calculations (RHF-INDO/S). One of the dimers shows indications of triplet energy transfer between the porphyrin subunits. The order of magnitude of the transfer rate is estimated to be 5 · 105 s?1. 相似文献
995.
Attempts were made to grow CeO2 and ThO2 single crystals doped with transition metal ions. Only Fe3+ and Mn2+ could be detected by the EPR technique. The EPR spectrum of Fe3+ in CeO2 exhibits the well-known fine structure in cubic fields. The parameters areg=2.0044(1) anda=15.6(1)·10?4 cm?1. The hyperfine constantA for57Fe in hexahedral coordination was found to be 8.9(1)·10?4 cm?1. The EPR spectrum of Mn2+ in CeO2 reveals two cubic Mn2+ centers. The parameters for center 1 areg=1.9999(1) andA=86.9(1)·10?4 cm?1 and for center 2g=1.9984(1) andA=87.0(1)·10?4 cm?1. Heating the Mn doped CeO2 samples in hydrogen, the Mn2+ centers transform from cubic into trigonal centers with approximate values ofg=1.9988(2),A=84.5(6)·10?4 cm?1 andD=203(1)·10?4 cm?1. The two observed Mn2+ centers in ThO2 exhibita priori axial symmetry with approximate values ofg=2.0006(2),A=88.9(4)·10?4 cm?1 andD=33(3)·10?4 cm?1. 相似文献
996.
997.
Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron‐based K‐edge XANES spectroscopy 下载免费PDF全文
Jörg Prietzel Gertraud Harrington Werner Häusler Katja Heister Florian Werner Wantana Klysubun 《Journal of synchrotron radiation》2016,23(2):532-544
Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K‐edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free‐ and cation‐bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K‐edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated soil organic matter (SOM), but far less efficiently by hematite, Ca‐saturated montmorillonite and Ca‐saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K‐edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated SOM differ from each other. They also are different from the spectra of amorphous FePO4, amorphous or crystalline AlPO4, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P‐retaining soil minerals in addition to spectra of free or cation‐bound IHP, AlPO4, FePO4 and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K‐edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented. 相似文献
998.
P. Köster M. Galimberti A. Giulietti D Giulietti L. A. Gizzi L. Labate S. Laville E. Suárez García 《Applied physics. B, Lasers and optics》2005,80(7):897-903
We consider the application of the differential absorption imaging technique in the soft X-ray region. The surface-density maps of test samples containing bromine, resulting from the application of the differential absorption imaging technique, are presented. Images of the samples were obtained in an X-ray monochromatic projection imaging scheme based on a spherically bent crystal using line emission close to the $L_2$ edge of bromine from a microplasma produced by focusing a nanosecond laser on the surface of an aluminum target. 相似文献
999.
Exchange splitting and dynamics of image-potential states in front of a 3 monolayer iron film on Cu(100) have been studied with time-, energy-, and spin-resolved bichromatic two-photon photoemission. For the first image-potential state n=1 we observe an exchange splitting of 56 +/- 10 meV and spin-dependent lifetimes of 16 +/- 2 fs for majority-spin and of 11 +/- 2 fs for minority-spin electrons, respectively. The time-resolved studies of both the population and the linewidth of image-potential states manifest that at the magnetic surface not only inelastic but also quasielastic scattering processes are spin dependent. 相似文献
1000.
We study the pattern formation in a lattice of locally coupled phase oscillators with quenched disorder. In the synchronized regime quasiregular concentric waves can arise which are induced by the disorder of the system. Maximal regularity is found at the edge of the synchronization regime. The emergence of the concentric waves is related to the symmetry breaking of the interaction function. An explanation of the numerically observed phenomena is given in a one-dimensional chain of coupled phase oscillators. Scaling properties, describing the target patterns are obtained. 相似文献