全文获取类型
收费全文 | 6607篇 |
免费 | 158篇 |
国内免费 | 18篇 |
专业分类
化学 | 3998篇 |
晶体学 | 84篇 |
力学 | 151篇 |
数学 | 749篇 |
物理学 | 1801篇 |
出版年
2021年 | 56篇 |
2020年 | 71篇 |
2019年 | 61篇 |
2018年 | 55篇 |
2016年 | 131篇 |
2015年 | 114篇 |
2014年 | 117篇 |
2013年 | 261篇 |
2012年 | 253篇 |
2011年 | 241篇 |
2010年 | 143篇 |
2009年 | 158篇 |
2008年 | 218篇 |
2007年 | 219篇 |
2006年 | 218篇 |
2005年 | 214篇 |
2004年 | 164篇 |
2003年 | 167篇 |
2002年 | 163篇 |
2001年 | 149篇 |
2000年 | 143篇 |
1999年 | 99篇 |
1998年 | 93篇 |
1997年 | 101篇 |
1996年 | 114篇 |
1995年 | 106篇 |
1994年 | 85篇 |
1993年 | 103篇 |
1992年 | 89篇 |
1991年 | 83篇 |
1990年 | 60篇 |
1989年 | 82篇 |
1988年 | 86篇 |
1987年 | 80篇 |
1986年 | 71篇 |
1985年 | 120篇 |
1984年 | 100篇 |
1983年 | 80篇 |
1982年 | 95篇 |
1981年 | 98篇 |
1980年 | 57篇 |
1979年 | 81篇 |
1978年 | 76篇 |
1977年 | 82篇 |
1976年 | 73篇 |
1975年 | 79篇 |
1973年 | 73篇 |
1968年 | 89篇 |
1967年 | 99篇 |
1966年 | 98篇 |
排序方式: 共有6783条查询结果,搜索用时 31 毫秒
151.
Armbruster P Agarwal YK Brüchle W Brügger M Dufour JP Gaggeler H Hessberger FP Hofmann S Lemmertz P Münzenberg G Poppensieker K Reisdorf W Schadel M Schmidt K Schneider JH Schneider WF Sümmerer K Vermeulen D Wirth aG Ghiorso A Gregorich KE Lee D Leino M Moody KJ Seaborg GT Welch RB Wilmarth P Yashita S Frink C Greulich N Herrmann G Hickmann U Hildebrand N Kratz JV Trautman N Fowler MM Hoffman DC Daniels WR von Gunten HR Dornhöfer H 《Physical review letters》1985,54(5):406-409
152.
153.
G. Münzenberg S. Hofmann H. Folger F. P. Heßberger J. Keller K. Poppensieker B. Quint W. Reisdorf K. H. Schmidt H. J. Schött P. Armbruster M. E. Leino R. Hingmann 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(2):227-235
In irradiations of207Pb and208Pb, respectively, with54Cr theα-decay of the isotopes259106,260106, and261106 could be observed for the first time. For260106 a spontaneous fission branch of (50 ?20 +30 )% was observed. The isotopes were identified by genetic relationships of α-decay after separation in-flight with the velocity filter SHIP and implantation into a position-sensitive silicon surface-barrier detector. The measured partial fission halflife of the doubly even isotope260106 of (7.2 ?2.7 +4.8 )ms exceeds the predicted values by at least a factor of 40. This result could be explained by the high shell corrections of the ground state mass, derived from the measured α-decay energies. The experimental results show evidence for an island of purely shell stabilized nuclei in the region of deformed isotopes beyond the actinides. 相似文献
154.
A. Bähring E. Meyer I. V. Hertel H. Schmidt 《Zeitschrift für Physik A Hadrons and Nuclei》1985,320(1):141-149
Pronounced polarization effects have been observed in inelastic collisions of laser state-prepared Na*(3p,M L) with Na+ leading to Na*(3d) for the energy rangeE CM=20–45 eV. Using linearly polarized light the dependence of the inelastic process on the alignment of the electronic charge cloud of the Na*(3p) prior to the collision has been measured. In studies with left and right hand circularly polarized light the angular momentum transferred in the collision process has been determined. The results are compared with similar data for the 3p→3s deexitation process studied previously [6]. The density matrix of the Na*(3p) state has been evaluated with respect to the collisional excitation to Na*(3d). Semiclassical calculations based on the coupled channel impact parameter approximation using pseudopotentials [7] and nonadiabatic rotational coupling elements for the Na 2 * system [12] have been performed. The agreement with the experimental results is good, in particular for the higher collision energies. 相似文献
155.
Edward E. Flagg Donald L. Schmidt 《Journal of polymer science. Part A, Polymer chemistry》1970,8(1):1-14
Poly[tris(diorganophosphinato)alanes], [Al(OPRR′O)3]n, were synthesized in which the organic moieties (R,R′) contained from one to eighteen carbon atoms. Polymeric properties depended upon the organic moieties; polymers were fusible, tractable, and flexible when the organic moieties contained six or more carbon atoms. Soluble polymers were prepared by using mixtures of symmetrical and unsymmetrical phosphinates. One polymer, poly{bis[n-butyl(benzyl)phosphinato]di-n-octylphosphinatoalane}, exhibited a degree of polymerization greater than 1000 and an exceptionally high intrinsic viscosity of 37 dl/g. The properties of the different polymers are discussed, and feasible structures are proposed. 相似文献
156.
Preparation of Ceramic Powders. II. Mg2TiO4, MgTiO3, and MgTi2O5 Formed by Hydrolysis of 2-Ethoxyethylates Solutions of 2-ethoxyethylates of magnesium and titanium in 2-ethoxyethanol submitted to hydrolysis, evaporation and heating of the residue up to 450°C allow to prepare Mg2TiO4, MgTiO3, and MgTi2O5 in an amorphous state with smaller than 1% of volatile components. Highly dispersed powders showing an increased sintering activity are obtained as a result of recrystallization. Mg2TiO4 is formed as inverse spinel phase in a metastable state. 相似文献
157.
158.
Stasch A Ferbinteanu M Prust J Zheng W Cimpoesu F Roesky HW Magull J Schmidt HG Noltemeyer M 《Journal of the American Chemical Society》2002,124(19):5441-5448
The reaction of the acetylene RC triple bond CH (R = Ph, CH(2)SiMe(3)) with an excess of AlH(3).NMe(3) in boiling toluene leads to the carbaalane [(AlH)(6)(AlNMe(3))(2)(CCH(2)R)(6)] (R = Ph 1, CH(2)SiMe(3) 2) in good yield. Treatment of 2 with BCl(3) under varying conditions gives the chlorinated products [(AlCl)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] 3 and [(AlCl)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(2)Cl)(6)] 4, respectively. The latter clearly demonstrates that the cluster can be stepwise functionalized within the inner and outer sphere. The X-ray single-crystal structures of 1, 2, and 4 have been determined. All compounds have in common that the central core consists of a cluster having eight aluminum and six carbon atoms. The bonding properties in this cluster are described as a new manifestation of three-dimensional surface aromaticity. Each Al(4)C fragment of the cube is formed by four bonds with three electron pairs, thus leading to a strong delocalization of the electrons. A phenomenological modeling using a three-dimensional Hückel scheme with fitted parameters to reproduce the energies from ab initio calculations revealed that the orbital scheme localized at one Al(4)C fragment possesses an orbital sextet with a large HOMO-LUMO gap. This is in line with the criteria of aromaticity. The idea of aromaticity was sustained also by qualitative valence bond reasons enumerating the different resonance structures by means of graph theoretical methods. 相似文献
159.
Findings on the formation and features of nanosized particles based on palladium complexes, which are active in hydrogenation catalysis, are summarized. Depending on the nature of a reducing agent, nanosized particles formed by the reduction of palladium(II) phosphine complexes are either metallic nuclei stabilized by organophosphorus ligands or associates of polynuclear phosphido or phosphinideno palladium complexes whose surface contains immobilized Pd(0) clusters. The ensembles of the Pd(0) atoms are active in hydrogenation. 相似文献
160.
Hans-Werner Schmidt 《Monatshefte für Chemie / Chemical Monthly》1987,118(2):217-228
The synthesis of several new derivatives of 2-amino-4-hydroxybenzonitrile2 and their herbicidal screening data are described. Thus, halogenation and furtherSandmeyer-Reaction of2 leads to the 2,3,5-trihalogenated derivatives5 a–e. Reaction of ethyl chloroformate with the amino group of2 gives6 a, acylation7 a, b and8. The 3,5-dihalogenated compounds10 a–e are obtained from6 a and7 a, b by bromination or iodation. The hydroxyl group of6 a, 7 a, b and10 a, c, e reacts with N,N-disubstituted carbamyl chlorides to give6 c, d, 9 a, b, 11, 12 and13 a, b. 相似文献