全文获取类型
收费全文 | 17017篇 |
免费 | 771篇 |
国内免费 | 149篇 |
专业分类
化学 | 11151篇 |
晶体学 | 52篇 |
力学 | 376篇 |
综合类 | 1篇 |
数学 | 3229篇 |
物理学 | 3128篇 |
出版年
2023年 | 172篇 |
2022年 | 311篇 |
2021年 | 397篇 |
2020年 | 524篇 |
2019年 | 565篇 |
2018年 | 424篇 |
2017年 | 333篇 |
2016年 | 709篇 |
2015年 | 648篇 |
2014年 | 633篇 |
2013年 | 1000篇 |
2012年 | 1195篇 |
2011年 | 1403篇 |
2010年 | 751篇 |
2009年 | 618篇 |
2008年 | 987篇 |
2007年 | 897篇 |
2006年 | 883篇 |
2005年 | 817篇 |
2004年 | 629篇 |
2003年 | 503篇 |
2002年 | 469篇 |
2001年 | 247篇 |
2000年 | 182篇 |
1999年 | 188篇 |
1998年 | 168篇 |
1997年 | 167篇 |
1996年 | 174篇 |
1995年 | 153篇 |
1994年 | 121篇 |
1993年 | 103篇 |
1992年 | 90篇 |
1991年 | 84篇 |
1990年 | 67篇 |
1989年 | 46篇 |
1988年 | 47篇 |
1987年 | 47篇 |
1986年 | 51篇 |
1985年 | 73篇 |
1984年 | 62篇 |
1983年 | 37篇 |
1982年 | 62篇 |
1981年 | 51篇 |
1980年 | 45篇 |
1979年 | 41篇 |
1978年 | 49篇 |
1977年 | 49篇 |
1976年 | 53篇 |
1974年 | 39篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Attila R. Imre W. Alexander Van Hook Bong Ho Chang Young Chan Bae 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1529-1539
Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N
1=5) to pentacontane (N
1=50)) with an oligostyrene (1241amu, N
2=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains. 相似文献
82.
Gareth R. Lewis Alexander J. Blake 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):m398-m400
The title complex, [NiCl(C12H16N3O2)2(H2O)]NO3·2CH4O·H2O, was obtained from a methanolic solution of Ni(NO3)2·6H2O, 2‐pyridyl nitronyl nitroxide (2‐NITpy) and (NEt4)2[CoCl4]. The equatorial coordination sites of the octahedral NiII centre are occupied by two chelating radical ligands, with the axial positions occupied by the Cl? and water ligands. The H2O—Ni—Cl axis of the complex lies along a crystallographic twofold axis, so that only half the cation is present in the asymmetric unit. The Ni—Cl bond length [2.3614 (17) Å] is significantly shorter than distances typical of octahedral NiII centres [2.441 (5) Å]. However, with only one nitrate anion per formula unit, the oxidation state of the metal must be assigned as NiII. The 2‐NITpy ligands bend away from the equatorial plane, forming a hydrophobic region around the Cl atoms. Conversely, the ligated water molecule forms moderately strong hydrogen bonds with the disordered methanol solvent molecules, which in turn form interactions with the water of crystallization and the disordered nitrate anion. These interactions combine to give hydrophilic regions throughout the crystal structure. 相似文献
83.
In this paper, we shall prove several non-existence results for divisible difference sets, using three approaches:
- character sum arguments similar to the work of Turyn [25] for ordinary difference sets,
- involution arguments and
- multipliers in conjunction with results on ordinary difference sets.
84.
Let a selfadjoint operator-valued functionL() be given on the interval [a,b] such thatL(a)0,L(b)0,L()0 (ab), andL() has a certain smoothness (for instance, it satisfies Hölder's condition). It turns out that the spectral theory of the operator-valued functionL() can be reduced to the spectral theory of one operatorZ, the spectrum of which lies on (a, b) and which is similar to a selfadjoint operator. In particular, the factorization takes place:L()=M()(I–Z), where the operator-valued functionM() is invertible on [a, b]. Earlier similar results were known only for analytic operator-valued functions. The authors had to use new methods for the proof of the described theorem. The key moment is the decomposition ofL
–1() into the sume of its principal and regular parts. 相似文献
85.
Schumm BA Koetke DS Adolphsen CE Alexander JP Averill D Barish BC Barklow T Barnett BA Blockus D Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan JM Drell PS Drewer DC Durrett D Elia R Feldman GJ Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Hanson G Harr R Harral B Harris FA Hayes K Hearty C Heusch CA Hildreth MD Himel T Hinshaw DA 《Physical review D: Particles and fields》1992,46(1):453-456
86.
Fulton R Jensen T Johnson DR Kagan H Kass R Morrow F Whitmore J Wilson P Bortoletto D Chen W Dominick J McIlwain RL Miller DH Ng CR Schaffner SF Shibata EI Shipsey IP Yao W Battle M Sparks K Thorndike EH Wang C Alam MS Kim IJ Li WC Romero V Sun CR Wang P Zoeller MM Goldberg M Haupt T Horwitz N Jain V Mestayer MD Moneti GC Rozen Y Rubin P Sharma V Skwarnicki T Thulasidas M Zhu G Csorna SE Letson T Alexander J Artuso M Bebek C Berkelman K Browder T Cassel DG Cheu E Coffman DM Crawford G DeWire JW 《Physical review D: Particles and fields》1991,43(3):651-663
87.
Kubota Y Nelson JK Perticone D Poling R Schrenk S Crawford G Fulton R Jensen T Johnson DR Kagan H Kass R Malchow R Morrow F Whitmore J Wilson P Bortoletto D Brown D Dominick J McIlwain RL Miller DH Modesitt M Ng CR Schaffner SF Shibata EI Shipsey IP Battle M Kroha H Sparks K Thorndike EH Wang C Alam MS Kim IJ Li WC Nemati B Romero V Sun CR Wang P Zoeller MM Goldberg M Haupt T Horwitz N Jain V Mestayer MD Moneti GC Rozen Y Rubin P Skwarnicki T Stone S Thusalidas M Yao W Zhu G Barnes AV Bartelt J 《Physical review D: Particles and fields》1991,44(3):593-600
88.
89.
Alexander Pott 《Combinatorica》1992,12(1):89-93
In this paper we develop a new method to obtain identities in a group algebraGF(p)G if an abelian difference set of ordern0 (modp) exists inG. We give an explicit formula ifp
2 orp
3 is the exactp-power dividingn. This generalizes the approach of Wilbrink, Arasu and the author. The proof presented here uses some knowledge about field extensions of thep-adic numbers. 相似文献
90.
On abelian difference set codes 总被引:1,自引:0,他引:1
Alexander Pott 《Designs, Codes and Cryptography》1992,2(3):263-271
In this paper we determine the ranks of the incidence matrices that belong to the following types of difference sets: Twin prime power difference sets, biquadratic residues and biquadratic residues with 0. We also prove a conjecture of Assmus and Key on the code generated by the hyperovals of PG(2, q). 相似文献