全文获取类型
收费全文 | 301篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
化学 | 233篇 |
晶体学 | 1篇 |
力学 | 18篇 |
数学 | 11篇 |
物理学 | 42篇 |
出版年
2021年 | 2篇 |
2016年 | 3篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 2篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 12篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1963年 | 2篇 |
1961年 | 1篇 |
1924年 | 2篇 |
排序方式: 共有305条查询结果,搜索用时 15 毫秒
171.
A series of one-dimensional arrays of lanthanide-transition metal complexes has been prepared and characterized. These complexes, [(DMF)(10)Ln(2)[Ni(CN)(4)](3)](infinity), crystallize as linear single-strand arrays (structural type A) (Ln = Sm, 1a; Eu, 2a) or double-strand arrays (structural type B) (Ln = Sm, 1b; Eu, 2b) depending upon the conditions chosen, and they are interconvertible. The single-strand type A structure can be converted to the double-strand type B structure. When the 1b and 2b type B crystals are completely dissolved in DMF, their infrared spectra are identical to the infrared spectra of 1a and 2a type A crystals dissolved in DMF. These solutions produce type A crystals initially. It is believed that formation of the type A structure is kinetically favored while the type B structure is thermodynamically favored for lanthanide-nickel complexes 1 and 2. On the other hand the complex [(DMF)(10)Y(2)[Pd(CN)(4)](3)](infinity), 3, appears to crystallize only as the double-strand array (type B). The complexes [(DMF)(12)Ce(2)[Ni(CN)(4)](3)](infinity), 4, and [(DMF)(12)Ce(2)[Pd(CN)(4)](3)](infinity), 5, crystallize as a new type of single-strand array (structural type C). This structural type is a zigzag chain array. Crystal data for 1a: triclinic space group P1, a = 10.442(5) A, b = 10.923(2) A, c = 15.168(3) A, alpha = 74.02(2) degrees, beta = 83.81(3) degrees, gamma = 82.91(4) degrees, Z = 2. Crystal data for 1b: triclinic space group P1, a = 9.129(2) A, b = 11.286(6) A, c = 16.276(7) A, alpha = 81.40(4) degrees, beta = 77.41(3) degrees, gamma = 83.02(3) degrees, Z = 2. Crystal data for 2a: triclinic space group P1, a = 10.467(1) A, b = 10.923(1) A, c = 15.123(1) A, alpha = 74.24(1) degrees, beta = 83.61(1) degrees, gamma = 83.13(1) degrees, Z = 2. Crystal data for 2b: triclinic space group P1, a = 9.128(1) A, b = 11.271(1) A, c = 16.227(6) A, alpha = 81.36(2) degrees, beta = 77.43(2) degrees, gamma = 82.99(1) degrees, Z = 2. Crystal data for 3: triclinic space group P1, a = 9.251(3) A, b = 11.193(4) A, c = 16.388(4) A, alpha = 81.46(2) degrees, beta = 77.18(2) degrees, gamma = 83.24(3) degrees, Z = 2. Crystal data for 4: triclinic space group P1, a = 11.279(1) A, b = 12.504(1) A, c = 13.887(1) A, alpha = 98.68(1) degrees, beta = 108.85(1) degrees, gamma = 101.75(1) degrees, Z = 2. Crystal data for 5: triclinic space group P1, a = 11.388(3) A, b = 12.614(5) A, c = 13.965(4) A, alpha = 97.67(3) degrees, beta = 109.01(2) degrees, gamma = 101.93(2) degrees, Z = 2. 相似文献
172.
173.
Fikret Kirkbir Hideaki Murata Douglas Meyers S. Ray Chaudhuri Arnab Sarkar 《Journal of Sol-Gel Science and Technology》1996,6(3):203-217
This review article summarizes the development of drying and sintering techniques for the production of sol-gel derived, large silica glass components. Gels may be synthesized using particulate or metal alkoxide precursors, or both in combination. Rapid fracture-free drying has been achieved easily with particulate gels because of their large pore size (100–6000 Å). Alkoxide gels, which generally have small pores (<200 Å), were initially difficult to dry without cracking. However, recent studies have shown that large alkoxide gel monoliths can also be dried in reasonably short times (<10 days). During subsequent heat treatment, alkoxide gels tend to have high shrinkage rates, which may cause trapping of hydroxyl ions or organic groups remaining on the gel surface. Although the removal of these species is easier for particulate gels, their large pore size necessitates heating above 1400°C to achieve full consolidation. Sintering at such temperatures was observed to deteriorate glass quality, through crystallization, warping, and/or sagging. Extensive optimization of the entire process has shown that on a laboratory scale, high-optical-quality glass can be produced from both alkoxide and particulate gels. It remains to be seen whether sol-gel process will be feasible for the manufacture of high-quality glass products on a commercial scale. 相似文献
174.
Kim G Sousa A Meyers D Shope M Libera M 《Journal of the American Chemical Society》2006,128(20):6570-6571
Using valence electron energy loss spectroscopy (EELS) in the cryo-scanning transmission electron microscopy (STEM), we found that the polymer-polymer interface in two-phase nanocolloids of polydimethyl siloxane (PDMS) and copolymer (methyl acrylate (MA)-methyl methacrylate (MMA)-vinyl acetate (VA)) preserved in water was diffuse despite the fact that equilibrium thermodynamics indicates it should only be on the order of a few nanometers. The diffuse interface is a result of the kinetic trapping of the copolymer within the PDMS phase, and this finding suggests new nonequilibrium pathways to control interfaces during the synthesis of multicomponent polymeric nanostructures. 相似文献
175.
176.
177.
Rephosgenation of N-carboxyanhydrides of γ-benzyl and y-methyl L-glutamates, vs multiple recrystallizations, is a very efficient method for obtaining highly purified N-carboxyanhydrides, from which very high MW (0.98-1.5 × 106 Daltons) polymers can be derived. 相似文献
178.
Cal Y. Meyers Duy H. Hua 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):197-198
Abstract p-Hydroxyphenyl α-halo sulfones are unusual in several respects. For example, p-hydroxyphenyl α-chloroisopropyl sulfone has no α′-H, however, when heated with one equivalent of base it undergoes a 1,7-elimination reaction via a pathway usually associated with the 1,3-elimination step of Ramberg-Bäcklund reactions. 相似文献
179.
180.