全文获取类型
收费全文 | 2314篇 |
免费 | 37篇 |
国内免费 | 16篇 |
专业分类
化学 | 1376篇 |
晶体学 | 15篇 |
力学 | 39篇 |
数学 | 484篇 |
物理学 | 453篇 |
出版年
2022年 | 20篇 |
2021年 | 23篇 |
2020年 | 27篇 |
2019年 | 18篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 40篇 |
2015年 | 31篇 |
2014年 | 39篇 |
2013年 | 104篇 |
2012年 | 82篇 |
2011年 | 90篇 |
2010年 | 55篇 |
2009年 | 46篇 |
2008年 | 86篇 |
2007年 | 91篇 |
2006年 | 99篇 |
2005年 | 93篇 |
2004年 | 94篇 |
2003年 | 72篇 |
2002年 | 56篇 |
2001年 | 33篇 |
2000年 | 26篇 |
1998年 | 19篇 |
1997年 | 20篇 |
1996年 | 42篇 |
1995年 | 32篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 30篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1987年 | 18篇 |
1986年 | 22篇 |
1985年 | 30篇 |
1984年 | 33篇 |
1983年 | 17篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 42篇 |
1979年 | 37篇 |
1978年 | 32篇 |
1977年 | 42篇 |
1976年 | 47篇 |
1975年 | 42篇 |
1974年 | 35篇 |
1973年 | 26篇 |
1972年 | 18篇 |
1971年 | 21篇 |
排序方式: 共有2367条查询结果,搜索用时 15 毫秒
971.
Arthur Friediger J. H. Vestergaard Stig Veibel 《Monatshefte für Chemie / Chemical Monthly》1967,98(4):1234-1244
Zusammenfassung Durch Reaktion zwischenp-Carboxybenzoldiazoniumionen und Verbindungen mit aktiven Methylengruppen werdenp-Carboxyphenylhydrazone gebildet, die die Ermittlung des Äquivalentgewichtes der Verbindung mit aktiver Meth yengruppe durch alkalimetrische Titration ermöglichen.Um die Tendenz zum Weiterreagieren unter Bildung von Formazan-Derivaten zu beschränken, wird die Kupplung bei pH<6 durchgeführt.Mit 2 AbbildungenHerrn Professor Dr.F. Wessely, im Gedenken an unsere erste Begegnung (Haupttagung des Vereins Österreichischer Chemiker, Linz 1949), zum 70. Geburtstag freundschaftlichst gewidmet. 相似文献
972.
973.
974.
John D. Donaldson Susan M. Grimes Arthur F. Lec. Holding Michelle Hornby 《Polyhedron》1985,4(7):1293-1295
The thermal decomposition of triphenyltin hydroxide in the temperature range 25–400°C has been studied. The decomposition products formed at each stage have been isolated and characterised. A decomposition scheme involving a reductive-elimination reaction is proposed. The proportions of this reaction and the accompanying reaction are dependent on the mode of heating. 相似文献
975.
Research supported in part by the NSF under Grant No. MCS-830123 相似文献
976.
We study the relationships between weakened forms of the Kinna-Wagner Selection Principle (KW), the Axiom of Choice (AC), and the Axiom of Multiple Choice (MC). 相似文献
977.
Patrick Chaltin Filip Borgions Jef Rozenski Arthur VanAerschot Piet Herdewijn 《Helvetica chimica acta》2003,86(3):533-547
In our search for new dsDNA‐binding ligands, combinatorial chemistry was first applied to select unnatural oligopeptides with moderate affinity for dsDNA. To enhance the binding affinity of a heptapeptide lead structure, Ac‐Arg‐Ual‐Sar‐Chi‐Chi‐Tal‐Arg‐NH2 (Kd=4.9?10?4 M ), the compound was conjugated to different heteropolyaromatic moieties by means of a variety of linker arms. Glycine, β‐alanine, glycyl‐glycine, glycyl‐β‐alanine, γ‐aminobutyric acid, and 6‐aminocaproic acid were used as spacers, representing different lengths and/or flexibilities. The intercalators coupled to the oligopeptide were acridine, fluorenone, anthracene, anthraquinone, and 3,8‐diamino‐5‐methyl‐6‐phenylphenantridinium (methidium). The binding capacities of these new hybrid molecules to dsDNA have been investigated by gel retardation and footprinting assays. The results show that, by conjugating the unnatural oligopeptide to intercalators, the affinity for dsDNA could be enhanced more than 100‐fold. For methidium‐β‐alanyl‐glycyl‐Arg‐Ual‐Sar‐Chi‐Chi‐Tal‐Arg‐NH2 (Kd of 2.1?10?6 M ), the interaction with dsDNA was dominated by the intercalator in such a way that the sequence specificity of the heptapeptide was changed. The interaction with dsDNA of hybrid molecules of other intercalators was mainly governed by the oligopeptide, since the sequence selectivity of the heptapeptide was conserved. In general, the linker arm glycine (shortest spacer) and glycine‐β‐alanine were preferred over β‐alanine, glycyl‐glycine and the more‐flexible spacers γ‐aminobutyric acid and 6‐aminocaproic acid. This way new hybrid molecules endowed with dsDNA affinities of ca. 10?6 M and displaying different sequence selectivities have been developed. Therefore, combinations of such unnatural peptides with intercalators can be used to broaden the knowledge about the sequence‐selective recognition of dsDNA. 相似文献
978.
Arthur Maki Wolfgang Quapp Stefan Klee Georg Ch. Mellau Sieghard Albert 《Journal of Molecular Spectroscopy》1996,180(2):323-336
We have measured the Fourier transform spectrum (FTS) of two isotopomers of hydrogen cyanide (H12C14N and H12C15N) from 500 to 10 000 cm−1. The infrared data have been combined with earlier published microwave and submillimeter-wave measurements. From this analysis new vibration–rotation energy levels and constants are given, based on the observation of a number of new vibrational levels, especially for H12C15N. The Coriolis interaction involving Δv3= −1, Δv2= 3, and Δl= ±1 has been observed for a great many levels and in some cases the assignments of laser transitions allowed by this interaction are more clearly shown. New vibration–rotation constants are given that allow one to predict the transition wavenumbers for most of the transitions below 10 000 cm−1with accuracies of about 0.5 cm−1or better. Values are given for the power series expansion of thel-type resonance constants and for the centrifugal distortion constants, as well as the usual vibrational and rotational constants. 相似文献
979.
Please forward books for review to the book review editor: Magdolna Hargittai, Structural Chemistry Research Group of the Hungarian Academy of Sciences, Eötvös University, H-1431 Budapest, Pf. 117, Hungary 相似文献
980.
Werschulz Arthur G. 《Journal of Complexity》1994,10(4)
Previous work on the ε-complexity of elliptic boundary-value problems Lu = f assumed that the class F of problem elements f was the unit ball of a Sobolev space. In a recent paper, we considered the case of a model two-point boundary-value problem, with F being a class of analytic functions. In this paper, we ask what happens if F is a class of piecewise analytic functions. We find that the complexity depends strongly on how much a priori information we have about the breakpoints. If the location of the breakpoints is known, then the ε-complexity is proportional to ln (ε−1), and there is a finite element p-method (in the sense of Babu
ka) whose cost is optimal to within a constant factor. If we know neither the location nor the number of breakpoints, then the problem is unsolvable for ε < √2. If we know only that there are b ≥ 2 breakpoints, but we de not know their location, then the ε-complexity is proportional to bε−1, and a finite element h-method is nearly optimal. In short, knowing the location of the breakpoints is as good as knowing that the problem elements are analytic, whereas only knowing the number of breakpoints is no better than knowing that the problem elements have a bounded derivative in the L2 sense. 相似文献