全文获取类型
收费全文 | 647篇 |
免费 | 6篇 |
专业分类
化学 | 560篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 20篇 |
物理学 | 69篇 |
出版年
2020年 | 10篇 |
2019年 | 7篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2014年 | 5篇 |
2013年 | 13篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 8篇 |
2008年 | 23篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 18篇 |
1999年 | 20篇 |
1998年 | 8篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 24篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1968年 | 4篇 |
1966年 | 5篇 |
1965年 | 8篇 |
1964年 | 64篇 |
1963年 | 53篇 |
1962年 | 13篇 |
排序方式: 共有653条查询结果,搜索用时 15 毫秒
1.
2.
3.
Summary A new buffer system for the separation of cations with capillary electrophoresis using indirect UV-detection is described. p-Aminopyridine can be used in the wide pH-range between 3 and 10. High-speed separations of positively charged non-UV absorbing ions are possible. Separation of ions with similar mobilities can be achieved by the addition of complexation reagents. The separation of potassium and ammonium is possible either with the addition of crown ether or at high pH-values. Transition metals can be separated by adding 2-hydroxybutyric acid to the buffer.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday 相似文献
4.
New Spiro Compounds from Cyclophosphazenes and Cyclodi[phosphadiazanes] Chlorocyclophosphazenes (Cl2P = N)3 and (Cl2p = N)4 react with dihydrazidophosphoric acid derivatives in THF in the presence of triethylamine to give the spirocyclic compounds Cl4N3P3(NHN(CH3))2P(S)OC6H5, Cl6N4P4(NHNH)2P(S)OC6H5. Constitutions have been confirmed by MS, NMR, IR and elemental analysis. 相似文献
5.
Heinz Engelhardt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1994,106(1):136-136
6.
7.
8.
Hägele Gerhard Boenigk Winfried Engelhardt Michael 《Analytical and bioanalytical chemistry》1985,320(7):676-677
Analytical and Bioanalytical Chemistry - 相似文献
9.
Clemens C. Freyhardt Michael Wiebcke Jürgen Felsche Günter Engelhardt 《Journal of inclusion phenomena and macrocyclic chemistry》1994,18(2):161-175
Single-crystal X-ray structure analyses of N(nPr)4[B5O6(OH)4][B(OH)3]2,1, and N(nBu)4 [B5O6(OH)4][B(OH)3]2,2, reveal that these materials are novel clathrates, the isotypic host structures of which are three-dimensional assemblies of hydrogen-bonded [B5O6(OH)4]– ionsand B(OH)3 molecules. The assembly of only the pentaborate anions is a distorted (i.e., along [102] elongated) fourconnected diamond-related network. The N(nPr)
4
+
and N(nBu)
4
+
ions are trapped within the complex three-dimensional channel systems of the host frameworks. Both1 and2 crystallize monoclinically with space groupP21/c andZ=4. The cell constants are:1:a=13.592(5),b=12.082(2),c=17.355(6) Å, =106.60(2)° (298K);2:a=13.874(3),b=12.585(1),c=17.588(4) Å, =107.04(1)° (238 K). The results obtained by both11B and13C MAS NMR spectroscopy are discussed. Thermogravimetric studies under a flowing inert-gas atmosphere suggest that water, stemming from polycondensation of the hydrous borate species, is released from the clathrates at ca. 443 K (1) and 398 K (2) before the decomposition of the organic cations starts at ca. 603 K (1) and 603 K (2).Author for correspondence.
Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82172 (82 pages). 相似文献
10.
On the Anion Constitutions of Aqueous Tetra-n-propylammonium and Tetraethylammonnium Silicate Solutions The constitution of the silicate anions present in 0.1 M to 3 M tetrapropylammonium-(TPA-) and tetraethylammonium-(TEA-)silicate solutions with molar TPA/Si ratios of 3, 1 and 0.6 and TEA/Si ratios of 3 and 1 is investigated by means of trimethylsilylation. Up to 16 different oligomeric silicate anions are detected and estimated quantitively. Type and quantitative dis-tribution of the silicate anions are very similar in diluted 0.1 M TEA- and TPA-silicate solutions. Concentrated TEA-silicate solutions contain preferably Si6O156? anions whereas concentrated TPA-silicate solutions are characterized by a broad distribution of different oligomeric silicate anions. The anion distribution of TPA- and TEA -silicate solutions is compared with the results of tetramethyl- and tetrabutylammonium silicate solutions studied previously. 相似文献