全文获取类型
收费全文 | 2197篇 |
免费 | 43篇 |
国内免费 | 8篇 |
专业分类
化学 | 1200篇 |
晶体学 | 4篇 |
力学 | 70篇 |
数学 | 274篇 |
物理学 | 700篇 |
出版年
2021年 | 12篇 |
2019年 | 16篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 31篇 |
2015年 | 23篇 |
2014年 | 34篇 |
2013年 | 88篇 |
2012年 | 84篇 |
2011年 | 108篇 |
2010年 | 71篇 |
2009年 | 49篇 |
2008年 | 132篇 |
2007年 | 128篇 |
2006年 | 99篇 |
2005年 | 93篇 |
2004年 | 89篇 |
2003年 | 63篇 |
2002年 | 75篇 |
2001年 | 53篇 |
2000年 | 59篇 |
1999年 | 25篇 |
1998年 | 25篇 |
1997年 | 24篇 |
1996年 | 55篇 |
1995年 | 64篇 |
1994年 | 50篇 |
1993年 | 51篇 |
1992年 | 45篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 25篇 |
1987年 | 30篇 |
1986年 | 17篇 |
1985年 | 21篇 |
1984年 | 24篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 32篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 24篇 |
1977年 | 23篇 |
1976年 | 29篇 |
1975年 | 25篇 |
1974年 | 17篇 |
1973年 | 21篇 |
1971年 | 14篇 |
1970年 | 12篇 |
排序方式: 共有2248条查询结果,搜索用时 31 毫秒
41.
M. J. Adams 《Optics & Laser Technology》1972,4(6):273-280
A new family of semiconductor injection lasers with high efficiencies and low threshold currents has recently shown promise for use in a wide range of applications. The heterostructure lasers are described here and the reasons for their improved performance are discussed. 相似文献
42.
For all oddv 3 the complete graph onvK
v
vertices can be decomposed intov – 2 edge disjoint cycles whose lengths are 3, 3, 4, 5,...,v – 1. Also, for all oddv 7,K
v
can be decomposed intov – 3 edge disjoint cycles whose lengths are 3, 4,...,v – 4,v – 2,v – 1,v.
Research supported by Australian Research Council grant A49130102 相似文献
43.
Adams MR Aïd S Anthony PL Averill DA Baker MD Baller BR Banerjee A Bhatti AA Bratzler U Braun HM Breidung H Busza W Carroll TJ Clark HL Conrad JM Davisson R Derado I Dhawan SK Dietrich FS Dougherty W Dreyer T Eckardt V Ecker U Erdmann M Faller F Fang GY Figiel J Finlay RW Gebauer HJ Geesaman DF Griffioen KA Guo RS Haas J Halliwell C Hantke D Hicks KH Hughes VW Jackson HE Jancso G Jansen DM Jin Z Kaufman S Kennedy RD Kinney ER Kirk T Kobrak HG Kotwal AV Kunori S Lancaster S Lord JJ Lubatti HJ 《Physical review letters》1995,74(9):1525-1529
44.
45.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM Casey D Castilla-Valdez H 《Physical review letters》1995,75(6):1023-1027
46.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Bloom P Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM Casey D Castilla-Valdez H 《Physical review letters》1995,75(8):1456-1461
47.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM Casey D Castilla-Valdez H 《Physical review letters》1995,75(4):618-623
48.
M. Adams P. Mascher A. H. Kitai 《Applied Physics A: Materials Science & Processing》1995,61(2):217-220
Positron lifetime and optical absorption techniques were employed to track the microstructural evolution of polycrystalline ZnS grown by Chemical Vapor Deposition (CVD). As grown material and material treated with Hot Isostatic Pressure (HIP) was sintered at temperatures ranging from 400 to 1000°C for 2–18 h. A 290 ps defect lifetime could be resolved in all samples, while an additional longer lifetime (=430 ps) was found only in samples annealed at low temperatures. This component gradually disappeared during annealing at 800°C. Associated with the disappearance of the long-lived component, the apparent bulk lifetime of the material changed from 235 to 215 ps. A 215±2 ps bulk parameter was also found for HIP-treated material annealed at temperatures greater than 400°C and hence is taken to represent the delocalized state of the positrons in ZnS. Optical absorption measurements showed that annealing at 800°C also caused the absorption profiles of the CVD and HIP samples to converge. The rate of the bulk lifetime transition correlates with the absorption changes. The observed sharpening of the absorption profile is attributed to a decrease in scattering from grain boundaries and voids, and a decrease in absorption from point defects. The 430 ps lifetime is believed to be due to trapping at voids and grain boundaries, while the 290 ps lifetime likely is due to a monovacancy stabilized as a small complex.Paper presented at the 132nd WE-Heraeus-Seminr on Positron Studies of Semiconductor Defects, Halle, Germany, 29 August to 2 September 1994 相似文献
49.
Simon A. Butler Gillian W. Harris David S. Moss Beatrice A. Gorinsky Margaret J. Adams Sheila Gover 《Journal of chemical crystallography》1994,24(1):1-3
We report the estimation of random errors in the refinement of the rigid body displacements of the -helices of the enzyme 6-phosphogluconate dehydrogenase. Least-squares refinement of the TLS parameters of the helices has been carried out using X-ray reflection data of 2.1 Å resolution, resulting in anR-factor of 19.5%. Standard deviations were estimated from the normal matrix. The results show that the translational mean-square displacements of nearly all the helices are significant at this resolution. However the libration parameters are only significant when the helices have at least four turns. Screw-rotation tensor values cannot be determined at this resolution. 相似文献
50.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alvarez G Alves GA Amos N Anderson EW Antipov Y Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Behnke T Bendich J Beri SB Bezzubov V Bhat PC Bhatnagar V Biswas N Blazey G Blessing S Boehnlein A Borcherding F Borders J Bozko N Brandt A Brock R Bross A Buchholz D Burtovoi V Butler JM Callot OH Castilla-Valdez H Chakraborty D Chekulaev S Chen J Chen L Chen W 《Physical review letters》1994,72(14):2138-2142