全文获取类型
收费全文 | 822篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 613篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 38篇 |
物理学 | 173篇 |
出版年
2022年 | 9篇 |
2021年 | 10篇 |
2016年 | 15篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 28篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 10篇 |
2008年 | 30篇 |
2007年 | 35篇 |
2006年 | 32篇 |
2005年 | 24篇 |
2004年 | 34篇 |
2003年 | 24篇 |
2002年 | 37篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 11篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 9篇 |
1987年 | 15篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 20篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1972年 | 8篇 |
1971年 | 9篇 |
1970年 | 6篇 |
1968年 | 7篇 |
1961年 | 6篇 |
排序方式: 共有833条查询结果,搜索用时 15 毫秒
41.
The Perthioborates RbBS3, TIBS3, and Tl3B3S10 . RbBS3 (P21/c, a=7.082(2) Å, b=11.863(4) Å, c=5.794(2) Å, β=106.54(2)°) was prepared as colourless, plate-shaped crystals by reaction of stoichiometric amounts of rubidium sulfide, boron, and sulfur at 600°C and subsequent annealing. TlBS3 (P21/c, a=6.874(3) Å, b=11.739(3) Å, c=5.775(2) Å, β=113.08(2)°) which is isotypic with RbBS3 was synthesized from a sample of the composition Tl2S · 2 B2S3. The glassy product which was obtained after 7 h at 850°C was annealed in a two zone furnace for 400 h at 400→350°C. Yellow crystals of TlBS3 formed at the warmer side of the furnace. Tl3B3S10 (P1 , a=6.828(2) Å, b=7.713(2) Å, c=13.769(5) Å, α=104.32(2)°, β=94.03(3)°, γ=94.69(2)°) was prepared as yellow plates from stoichiometric amounts of thallium sulfide, boron, and sulfur at 850°C and subsequent annealing. All compounds contain tetrahedrally coordinated boron. The crystal structures consist of polymeric anion chains. In the case of RbBS3 and TlBS3 nonplanar five-membered B2S3 rings are spirocyclically connected via the boron atoms. To obtain the anionic structure of Tl3B3S10 every third B2S3 ring of the polymeric chains of MBS3 is to be substituted by a six-membered B(S2)2B ring. 相似文献
42.
Synthesis and Crystal Structure of a Novel Hexagonal Modification of Al2S3 with Five-coordinated Aluminum A new hexagonal high temperature modification of Al2S3 could be prepared by chemical vapour transport with iodine (860 → 750°C) or by annealing of α -Al2S3 at 550°C. According to the single crystal X-ray structure determination the novel form of Al2S3 crystallizes in space group P 61 (No. 169) with a = 6.491(1), c = 17.169(4) Å, V = 626.5 Å3, Z = 6; R = 0.0253. In this modification one half of the aluminum atoms are tetrahedrally coordinated [d(Al? S): 2.226–2.267 Å], whereas the other half are in trigonal bipyramidal coordination of five S atoms with bond lengths of 2.272–2.315 Å (equatorial) and 2.495–2.521 Å (axial). Aluminum in AlS5 coordination is observed for the first time in this compound. The crystal structure is isotypic to In2Se3 and AlInS3. In addition, results of a refinement of the α -Al2S3 crystal structure are reported which were obtained on crystals prepared also by chemical vapour transport with iodine. 相似文献
43.
44.
45.
Chelate complexes of SCHIFF bases of salicylaldehyde with bivalent nickel and copper often show an association of molecules in the crystal lattice. With SCHIFF bases of one-sided substituted, ethylene and propylene diamines the IR-spectrum shows only the coordination number four for Ni and Cu. Prom the IR absorption of the secondary amine group of diethylenetriamine, dipropylentriamine, and triethylenetetramine, a definite shifting of the NH frequency in the copper salts is observed. With the nickel salts the shifting is not so strong and sometimes indefinite. Therefore the occupation of a fifth coordination site at the two metal atoms is proved definitely in the case of the copper compounds, whereas for the nickel compounds investigated this seems to be only probable in most cases. 相似文献
46.
47.
Na2B2Se7, K2B2S7, and K2B2Se7: Three Perchalcogenoborates with a Novel Polymeric Anion Network Na2B2Se7 (I 2/a; a = 11.863(4) Å, b = 6.703(2) Å, c = 13.811(6) Å, β = 109.41(2)°; Z = 4), K2B2S7 (I 2/a; a = 11.660(2) Å, β = 6.827(1) Å, c = 12.992(3) Å, β = 106.78(3)°; Z = 4), and K2B2Se7 (I 2/a; a = 12.092(4) Å, b = 7.054(2) Å, c = 13.991(5) Å, β = 107.79(3)°; Z = 4) were prepared by reaction of stoichiometric amounts of sodium selenide (potassium sulfide) with boron and sulfur or of potassium selenide and boron diselenide, respectively, at 600°C with subsequent annealing. The crystal structures consist of polymeric anion chains of composition ([B2S7]2?)n or ([B2Se7]2?)n formed by spirocyclically connected five-membered B2S3 (B2Se3) rings and six-membered B2S4 (B2Se4) rings. The nine-coordinate alkaline metal cations are situated in between. 相似文献
48.
49.
50.