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   121篇
  免费   2篇
  国内免费   1篇
化学   66篇
晶体学   1篇
力学   2篇
数学   43篇
物理学   12篇
  2023年   1篇
  2022年   5篇
  2021年   3篇
  2020年   8篇
  2019年   4篇
  2018年   6篇
  2017年   5篇
  2016年   3篇
  2015年   5篇
  2014年   9篇
  2013年   12篇
  2012年   7篇
  2011年   9篇
  2010年   5篇
  2009年   7篇
  2008年   6篇
  2007年   2篇
  2006年   4篇
  2005年   6篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  2001年   1篇
  1999年   1篇
  1997年   1篇
  1996年   1篇
  1993年   1篇
  1990年   1篇
  1927年   3篇
  1926年   2篇
排序方式: 共有124条查询结果,搜索用时 15 毫秒
81.
Graphite oxide/Al13 composites were prepared using graphite oxide and commercial solution of Chlorhydrol®. Although surfactant was used to disperse of graphene-like layers, they were restacked together upon addition of Al13 Keggin polycations. The crust of inorganic phase was deposited on the outer surface of GO platelets. The resulting materials were used as adsorbents of ammonia in dry or wet conditions either in an as received form or prehumidified for 2 h before the breakthrough test. It was shown that water in the system decreases the amount adsorbed, likely as a result of the competition with ammonia for adsorption centers. The highest and strongest adsorption was found in the dry conditions where interlayer space was partially available and the acidic centers of an inorganic phase played an enhancing role in the retention of ammonia.  相似文献   
82.
The paper contains theorems on the uniqueness and existence of a generalized solution to the Fourier problem (the problem without initial conditions) for a class of strongly nonlinear parabolic equations, without any restrictions on the behavior of the data and of the solution ast → ∞. A priori estimates of the solution are obtained as well. Bibliography: 8 titles. Dedicated to Olga Arsenievna Oleinik Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 19, pp. 000-000, 0000.  相似文献   
83.
Mesoporous carbons with highly dispersed copper, cobalt, and iron were obtained from an organic polymer within amorphous silica powder, alumina, and zeolite 13X. The materials were characterized using the adsorption of nitrogen, potentiometric titration, and elemental analysis. The small metal content (less than 1%) and its chelation in the precursor polymers ensure a high dispersion of metallic centers. The materials obtained are mainly mesoporous but differ significantly in their porosity and surface chemistry, which is linked to the effect of template constraints and chemistry and the kind of metal and is related to the differences in the carbonization mechanism. On the carbon obtained, the adsorption of dibenzothiophene (DBT) from hexane was carried out. The high capacities (up to 130 mg S/g) obtained were linked to the high volume of mesopores and specific interactions of DBT with surface acidic groups and strong interactions of metals with dibenzothiophene via S-M sigma bonds or, in the case of copper, via interaction of metals with disturbed pi electrons of aromatic rings of DBT.  相似文献   
84.
Polycrystalline Sm4Ni11In20 was obtained by arc-melting of metal ingots. A subsequent high temperature treatment was used for single crystal growth. The Sm4Ni11In20 crystal structure (U4Ni11Ga20 type; C2/m, a = 22.5457(3) Å, b = 4.34929(5) Å, c = 16.5479(2) Å, β = 124.592(2)°, R1 = 0.0358, wR2 = 0.0934) was determined by single crystal synchrotron radiation X-ray diffraction from 2014 independent reflections with I > 2σ(I). Sm4Ni11In20 extends the R 4Ni11In20 (R = Y, Gd, Tb, Dy, Ho) series of phases. The R 4Ni11In20 and RNi3In6 (LaNi3In6 type; R = La, Ce, Pr, Nd, Eu) series have similar compositions. Their structures share similar fragments; in particular the rare earth atom coordination polyhedra are pentagonal prisms with additional atoms.   相似文献   
85.
Base-catalyzed cycloaddition reactions of heterocyclic azides with activated nitriles were studied. Convenient, efficient, and high-yield synthetic method for thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines preparation from available starting reagents without complicated protocols was elaborated. Such an approach allows creation of broad combinatorial libraries for drug discovery.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]  相似文献   

86.
Formulas are given for the Lebesgue measure and the Hausdorff–Besicovitch dimension of the minimal closed set Sξ supporting the distribution of the random variable ξ = 2k τk, where τk are independent random variables taking the values 0, 1, 2 with probabilities p 0k , p 1k , p 2k , respectively. A classification of the distributions of the r.v. ξ via the metric‐topological properties of Sξ is given. Necessary and sufficient conditions for superfractality and anomalous fractality of Sξ are found. It is also proven that for any real number a 0 [0, 1] there exists a distribution of the r.v. ξ such that the Hausdorff–Besicovitch dimension of Sξ is equal to a 0. The results are applied to the study of the metric‐topological properties of the convolutions of random variables with independent binary digits, i.e., random variables ξi = , where ηk are independent random variables taking the values 0 and 1. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
87.
We investigate the well-posedness of a problem for a system of functional differential equations of different types without initial conditions. Each equation consists of two parts one of which has the same structure as a parabolic equation or an ordinary differential equation with parameters, while the other contains functionals defined on a space of functions continuous in space variables.  相似文献   
88.
It has been shown that reactions 5‐substituted 2‐nitrothiophenes with arylacetonitriles in the presence of potassium hydroxide in methanol lead to the formation of the new [2‐(hydroxyimino)‐5‐R‐3(2H)‐thienylidene](aryl)acetonitriles. Under proposed reaction conditions, the formation of thieno[2,3‐c]isoxazole was not the case. J. Heterocyclic Chem., (2011).  相似文献   
89.
In this paper, we investigate the loss process in a finite-buffer queue with batch arrivals and total rejection discipline. In such a model, if the buffer has insufficient capacity to accept all the customers included in an arriving batch, the whole batch is blocked and lost. This scheme is especially useful in performance evaluation of buffering processes in IP (internet protocol) networks. The main result of this paper is a closed-form formula for the joint distribution of the length of the first lost series of batches and the time of the first loss. Moreover, the limiting distribution (as the buffer size grows to infinity) is shown.  相似文献   
90.
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