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   173篇
  免费   6篇
化学   90篇
晶体学   1篇
力学   6篇
数学   16篇
物理学   66篇
  2022年   8篇
  2021年   8篇
  2020年   3篇
  2019年   2篇
  2018年   1篇
  2016年   6篇
  2015年   5篇
  2014年   11篇
  2013年   13篇
  2012年   6篇
  2011年   18篇
  2010年   11篇
  2009年   8篇
  2008年   11篇
  2007年   8篇
  2006年   10篇
  2005年   6篇
  2004年   8篇
  2003年   2篇
  2002年   2篇
  2001年   4篇
  2000年   3篇
  1998年   1篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1988年   1篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1978年   1篇
  1976年   1篇
  1972年   2篇
  1970年   1篇
  1968年   1篇
  1966年   1篇
  1932年   1篇
排序方式: 共有179条查询结果,搜索用时 31 毫秒
141.
The present study describes the characterization of energy and structure of HBr(2+) in its low-lying electronic states, achieved through an extension of a new empirical method [Chem. Phys. Lett. 379, 139 (2003)] recently introduced to evaluate the interatomic interaction in the HX(2+) (X=F,Cl,Br,I) molecular dications. The method is based on identification of the main components of the interaction and their evaluation through some simple correlation formulas. Potential energy curves, given in a simple, natural, and analytical form, made possible the calculations of some important properties, such as double-photoionization energy thresholds, vibrational spacing, average lifetime, and Franck-Condon factors. The predictions, compared with data available in the literature, are of great interest for the analysis and interpretation of some new experimental results.  相似文献   
142.
143.
Vitamins are a chemically heterogeneous group of compounds known as essential for the normal functioning of the organic metabolism. Their decrease in humans can lead to several diseases and not being produced by the body, they need to be obtained from dietary sources or supplements. For these reasons, their determination in food, pharmaceutical and clinical samples is crucial. This article reviews key advances in electrochemical measurements of vitamins over the past decade. Particular attention is given to papers proving applicability to real samples analysis. The technical features of the proposed sensors are presented and discussed along with their analytical performances. Future trends and challenges are also addressed.  相似文献   
144.
The Wigner function was introduced as a generalization of the concept of distribution function for quantum statistics. The aim of this work is pushing further the formal analogy between quantum and classical approaches. The Wigner function is defined as an ensemble average, i.e., in terms of a mixture of pure states. From the point of view of basic physics, it would be very appealing to be able to define a Wigner function also for pure states and the associated expectation values for quantum observables, in strict analogy with the definition of mean value of a physical quantity in classical mechanics; then correct results for any quantum system should be recovered as appropriate superpositions of such “pure-state” quantities. We will show that this is actually possible, at the cost of dealing with generalized functions in place of proper functions.  相似文献   
145.
Photodynamic therapy (PDT) is a light-based cancer therapy approach that has shown promising results in treating various malignancies. Growing evidence indicates that cancer stem cells (CSCs) are implicated in tumor recurrence, metastasis, and cancer therapy resistance in colorectal cancer (CRC); thus, targeting these cells can ameliorate the prognosis of affected patients. Based on our bioinformatics results, SOX2 overexpression is significantly associated with inferior disease-specific survival and worsened the progression-free interval of CRC patients. Our results demonstrate that zinc phthalocyanine (ZnPc)-PDT with 12 J/cm2 or 24 J/cm2 irradiation can substantially decrease tumor migration via downregulating MMP9 and ROCK1 and inhibit the clonogenicity of SW480 cells via downregulating CD44 and SOX2. Despite inhibiting clonogenicity, ZnPc-PDT with 12 J/cm2 irradiation fails to downregulate CD44 expression in SW480 cells. Our results indicate that ZnPc-PDT with 12 J/cm2 or 24 J/cm2 irradiation can substantially reduce the cell viability of SW480 cells and stimulate autophagy in the tumoral cells. Moreover, our results show that ZnPc-PDT with 12 J/cm2 or 24 J/cm2 irradiation can substantially arrest the cell cycle at the sub-G1 level, stimulate the intrinsic apoptosis pathway via upregulating caspase-3 and caspase-9 and downregulating Bcl-2. Indeed, our bioinformatics results show considerable interactions between the studied CSC-related genes with the studied migration- and apoptosis-related genes. Collectively, the current study highlights the potential role of ZnPc-PDT in inhibiting stemness and CRC development, which can ameliorate the prognosis of CRC patients.  相似文献   
146.
Taking into account the uncertainty of measurement when assessing compliance of a given sample with compositional specifications or statutory limits is an open question. Rigorous assessment should be performed within the signal domain, and by considering both α and β errors. Working within the concentration domain through a calibration function, which is affected by additional experimental uncertainties, involves a different degree of uncertainty and can sometimes lead to unreliable verdicts. The matter is discussed, and illustrated with the aid of some worked examples, each using multiple simulated data sets, obtained by adding an arbitrarily chosen Gaussian noise to representative response/concentration functional relationships. Received: 12 October 2000 Accepted: 12 July 2001  相似文献   
147.
Eeltink  D.  Armaroli  A.  Luneau  C.  Branger  H.  Brunetti  M.  Kasparian  J. 《Nonlinear dynamics》2020,102(4):2385-2398
Nonlinear Dynamics - We theoretically and experimentally examine the effect of forcing and damping on systems that can be described by the nonlinear Schrödinger equation (NLSE), by making use...  相似文献   
148.
We present a perturbative construction of interacting quantum field theories on smooth globally hyperbolic (curved) space-times. We develop a purely local version of the Stückelberg–Bogoliubov–Epstein–Glaser method of renormalization by using techniques from microlocal analysis. Relying on recent results of Radzikowski, K?hler and the authors about a formulation of a local spectrum condition in terms of wave front sets of correlation functions of quantum fields on curved space-times, we construct time-ordered operator-valued products of Wick polynomials of free fields. They serve as building blocks for a local (perturbative) definition of interacting fields. Renormalization in this framework amounts to extensions of expectation values of time-ordered products to all points of space-time. The extensions are classified according to a microlocal generalization of Steinmann scaling degree corresponding to the degree of divergence in other renormalization schemes. As a result, we prove that the usual perturbative classification of interacting quantum field theories holds also on curved space-times. Finite renormalizations are deferred to a subsequent paper. As byproducts, we describe a perturbative construction of local algebras of observables, present a new definition of Wick polynomials as operator-valued distributions on a natural domain, and we find a general method for the extension of distributions which were defined on the complement of some surface. Received: 31 March 1999 / Accepted: 10 June 1999  相似文献   
149.
Brunetti  Matteo  Favata  Antonino  Paolone  Achille  Vidoli  Stefano 《Meccanica》2020,55(4):883-890
Meccanica - We propose a mixed variational principle for deducing the generalized Marguerre–von Kármán equations, governing the relatively large deflections of thin elastic shallow...  相似文献   
150.
Rising global populations and enhanced standards of living in so-called developing countries have led to an increased demand of food, in particular meat, worldwide. While increasing the production of broiler meat could be a potential solution to this problem, broiler meat is plagued by health concerns, such as the development of antimicrobial resistance and lower meat quality. For this reason, the supplementation of poultry feed with vitamins and antioxidant compounds, such as polyphenols, has become an attractive prospect for research in this sector. Such supplements could be obtained by extraction of agricultural byproducts (in particular, grape pomaces and artichoke leaves and bracts), thus contributing to reductions in the total amount of waste biomass produced by the agricultural industry. In this review, the effects of poultry feed supplementation with bioactive extracts from grape pomace (skins and/or seeds), as well as extracts from artichoke leaves and bracts, were explored. Moreover, the various methods that have been employed to obtain extracts from these and other agricultural byproducts were listed and described, with a particular focus on novel, eco-friendly extraction methods (using, for example, innovative and biocompatible solvents like Deep Eutectic Solvents (DESs)) that could reduce the costs and energy consumption of these procedures, with similar or higher yields compared to standard methods.  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