首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   870篇
  免费   7篇
  国内免费   2篇
化学   632篇
晶体学   6篇
力学   10篇
数学   115篇
物理学   116篇
  2016年   9篇
  2015年   7篇
  2014年   9篇
  2013年   31篇
  2012年   21篇
  2011年   39篇
  2010年   14篇
  2009年   17篇
  2008年   28篇
  2007年   28篇
  2006年   33篇
  2005年   22篇
  2004年   27篇
  2003年   19篇
  2002年   25篇
  2001年   7篇
  2000年   11篇
  1999年   9篇
  1987年   9篇
  1980年   10篇
  1978年   10篇
  1971年   8篇
  1966年   6篇
  1944年   9篇
  1943年   7篇
  1928年   6篇
  1916年   7篇
  1915年   8篇
  1911年   8篇
  1910年   12篇
  1909年   11篇
  1908年   7篇
  1907年   8篇
  1904年   6篇
  1901年   8篇
  1900年   12篇
  1899年   6篇
  1898年   11篇
  1897年   6篇
  1895年   7篇
  1894年   6篇
  1893年   6篇
  1892年   11篇
  1891年   12篇
  1890年   9篇
  1889年   7篇
  1888年   6篇
  1882年   10篇
  1870年   8篇
  1866年   7篇
排序方式: 共有879条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Summary In a separable metric space, if two Borel probability measures (laws) are nearby in a suitable metric, then there exist random variables with those laws which are nearby in probability. Specifically, by a well-known theorem of Strassen, the Prohorov distance between two laws is the infimum of Ky Fan distances of random variables with those laws. The present paper considers possible extensions of Strassen's theorem to two random elements one of which may be (compact) set-valued and/or non-measurable. There are positive results in finite-dimensional spaces, but with factors depending on the dimension. Examples show that such factors cannot entirely be avoided, so that the extension of Strassen's theorem to the present situation fails in infinite dimensions.This research was partially supported by a Guggenheim Fellowship, by National Science Foundation grant DMS 8505550 at MSRI-Berkeley, and other NSF grants  相似文献   
5.
This paper presents results on symmetries of the spectrum of singularities for random cascades found in the statistical theory of turbulence. It is shown that empirical dimension curves possess a natural symmetry whose presence restricts the class of allowable probability distributions of the cascade generator in a simple manner. In particular, necessary and sufficient conditions on the probability distribution of the generator are obtained for symmetry of the singularity spectrum within a large class of cascade models.  相似文献   
6.
7.
Functionalised hydroxylamine derivatives of (S)-prolinol prepared by a Cope elimination have been found to undergo oxidation to the nitrone either in the presence of air or a catalytic quantity of TPAP. These undergo intramolecular cycloaddition to give tricyclic isoxazolidines with high diastereoselectivity.  相似文献   
8.
We show that under suitable conditions $$\begin{gathered} E_x f\left\{ {a + \int_0^t \beta \left[ {b + \int_0^s {\alpha \left( {X_r } \right)dr, c + s, X_s } } \right]ds, b + \int_0^t {\alpha \left( {X_s } \right)ds, c + t, X_t } } \right\} \hfill \\ = e^{tG} f\left[ {a, b, c, x} \right] \hfill \\ \end{gathered} $$ whereX t is a Brownian motion andG is the generator of a (C 0) contraction semigroupe tG.  相似文献   
9.
Model identification has traditionally been ignored in forecasting via exponential smoothing. The usual practice is to apply the same model to every time-series in a collection. This paper develops a procedure for model identification in large forecasting applications based on an examination of variances of differences of the time-series. The order of differencing yielding minimum variance suggests an appropriate model for the series. Empirical results show that this procedure selects models that give reasonable ex ante forecast accuracy.  相似文献   
10.
The synthesis of 2-methyl-5H-dibenz[b,f]azepine-5-carboxamide (2-methylcarbamazepine, 2-MCBZ, 8), a promising internal standard for chromatographic assays of the antiepileptic agent carbamazepine (CBZ, 1), is described. N-(p-Tolyl)anthranilic acid (2) was utilized as a starting material for the synthesis of a key compound, 2,9-dimethylacridine (4), which was converted in two steps to 2-methyl-9-hydroxymethylacridan (6). The acridan 6, in the presence of poly-phosphoric acid, was ring-expanded to form 2-methyl-5H-dibenz[b,f]azepine (7), this latter compound being converted by conventional reactions to its 5-carbamyl derivative, 2-MCBZ (8).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号