全文获取类型
收费全文 | 4380篇 |
免费 | 72篇 |
国内免费 | 10篇 |
专业分类
化学 | 3115篇 |
晶体学 | 20篇 |
力学 | 68篇 |
数学 | 932篇 |
物理学 | 327篇 |
出版年
2019年 | 34篇 |
2016年 | 71篇 |
2015年 | 51篇 |
2014年 | 34篇 |
2013年 | 113篇 |
2012年 | 89篇 |
2011年 | 140篇 |
2010年 | 102篇 |
2009年 | 114篇 |
2008年 | 140篇 |
2007年 | 139篇 |
2006年 | 146篇 |
2005年 | 130篇 |
2004年 | 104篇 |
2003年 | 101篇 |
2002年 | 103篇 |
2001年 | 54篇 |
2000年 | 73篇 |
1999年 | 61篇 |
1998年 | 59篇 |
1997年 | 56篇 |
1996年 | 71篇 |
1995年 | 79篇 |
1994年 | 59篇 |
1993年 | 68篇 |
1992年 | 95篇 |
1991年 | 95篇 |
1990年 | 79篇 |
1989年 | 72篇 |
1988年 | 60篇 |
1987年 | 65篇 |
1986年 | 68篇 |
1985年 | 84篇 |
1984年 | 90篇 |
1983年 | 84篇 |
1982年 | 81篇 |
1981年 | 107篇 |
1980年 | 61篇 |
1979年 | 80篇 |
1978年 | 74篇 |
1977年 | 92篇 |
1976年 | 65篇 |
1975年 | 79篇 |
1974年 | 85篇 |
1973年 | 64篇 |
1972年 | 55篇 |
1971年 | 48篇 |
1970年 | 37篇 |
1967年 | 31篇 |
1962年 | 29篇 |
排序方式: 共有4462条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Stefan Peterli Dieter Hubmann Urs Squin Helmut Mett Peter Traxler 《Helvetica chimica acta》1994,77(1):59-69
β-Nitrostyrene derivatives of adenosine 5′-glutarates are potent and selective bisubstrate-type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′-esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC50 = 0.7–12 μM ), most of the modified compounds inhibited the EGF-R PTK only marginally or were inactive (IC50 ≥ 100 μM ). The only exceptions were the free acids 19 and 20 with IC50 values of ca. 5 μM . It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers. 相似文献
5.
Helmut Schmidhammer Eva Scherb-Bukowiecki Thomas A. Mayer Peter Schnholzer 《Helvetica chimica acta》1994,77(6):1590-1594
The synthesis of benzazepine analogues of the opium alkaloid noscapine ( 1 ) is described. The benzazepines 2 and 3 were prepared starting from nornarceine ethyl ester ( 4 ; readily available from 1 ) in several steps. X-Ray analysis of compound 2 revealed that it is not a diastereosisomer mixture but a racemate of the threo-form and thus has the same configuration as 1 . 相似文献
6.
7.
8.
Simply generated families of trees are described by the equation T(z) = ϕ(T(z)) for their generating function. If a tree has n nodes, we say that it is increasing if each node has a label ∈ { 1,…,n}, no label occurs twice, and whenever we proceed from the root to a leaf, the labels are increasing. This leads to the concept of simple families of increasing trees. Three such families are especially important: recursive trees, heap ordered trees, and binary increasing trees. They belong to the subclass of very simple families of increasing trees, which can be characterized in 3 different ways. This paper contains results about these families as well as about polynomial families (the function ϕ(u) is just a polynomial). The random variable of interest is the level of the node (labelled) j, in random trees of size n ≥ j. For very simple families, this is independent of n, and the limiting distribution is Gaussian. For polynomial families, we can prove this as well for j,n → ∞ such that n − j is fixed. Additional results are also given. These results follow from the study of certain trivariate generating functions and Hwang's quasi power theorem. They unify and extend earlier results by Devroye, Mahmoud, and others. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2007 相似文献
9.
10.
This paper presents an analytic approach to the construction cost of fringe-balanced binary search trees. In [7], Mahmoud used a bottom-up approach and an urn model of Pólya. The present method is top-down and uses differential equations and Hwang's quasi-power theorem to derive the asymptotic normality of the number of rotations needed to construct such afringe balanced search tree. We also obtain the exact expectation and variance with this method. Although Pólya's urn model is no longer needed, we also present an elegant analysis of it based on an operator calculus as in [4].This research was supported by the Austrian Research Society (FWF) under the project number P12599-MAT. 相似文献