全文获取类型
收费全文 | 2476篇 |
免费 | 106篇 |
国内免费 | 19篇 |
专业分类
化学 | 1783篇 |
晶体学 | 18篇 |
力学 | 20篇 |
数学 | 366篇 |
物理学 | 414篇 |
出版年
2023年 | 14篇 |
2022年 | 28篇 |
2021年 | 49篇 |
2020年 | 57篇 |
2019年 | 68篇 |
2018年 | 53篇 |
2017年 | 54篇 |
2016年 | 107篇 |
2015年 | 87篇 |
2014年 | 109篇 |
2013年 | 177篇 |
2012年 | 175篇 |
2011年 | 220篇 |
2010年 | 128篇 |
2009年 | 113篇 |
2008年 | 165篇 |
2007年 | 145篇 |
2006年 | 137篇 |
2005年 | 95篇 |
2004年 | 94篇 |
2003年 | 63篇 |
2002年 | 64篇 |
2001年 | 28篇 |
2000年 | 22篇 |
1999年 | 21篇 |
1998年 | 26篇 |
1997年 | 19篇 |
1996年 | 25篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 20篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1977年 | 6篇 |
1975年 | 8篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1966年 | 6篇 |
1958年 | 6篇 |
1955年 | 9篇 |
排序方式: 共有2601条查询结果,搜索用时 15 毫秒
161.
Petr Munster Tomas Horvath Josef Vojtech Ondrej Havlis Martin Slapak Pavel Skoda 《Fiber and Integrated Optics》2017,36(3):144-156
Currently, individual optical fibers are mostly used for each non-data application, which is very inefficient and uneconomical. Sharing a single fiber for multiple applications is a promising solution. However, in the case of a non-data application, the situation is much more complicated compared to data because of special application´s requirements. In laboratory setup, we performed a measurement with a standard G.652D optical fiber for analyzing possible interaction of stable frequency/accurate time transmission, 1.25/10Gbps data transmission (typical bitrates for access point-to-point networks), and high-power sensor signal for different channel spacing and different pulse duration of sensor signal. 相似文献
162.
163.
164.
In abstract algebraic logic, the general study of propositional non-classical logics has been traditionally based on the abstraction
of the Lindenbaum-Tarski process. In this process one considers the Leibniz relation of indiscernible formulae. Such approach
has resulted in a classification of logics partly based on generalizations of equivalence connectives: the Leibniz hierarchy. This paper performs an analogous abstract study of non-classical logics based on the kind of generalized implication connectives
they possess. It yields a new classification of logics expanding Leibniz hierarchy: the hierarchy of implicational logics. In this framework the notion of implicational semilinear logic can be naturally introduced as a property of the implication, namely a logic L is an implicational semilinear logic iff it
has an implication such that L is complete w.r.t. the matrices where the implication induces a linear order, a property which
is typically satisfied by well-known systems of fuzzy logic. The hierarchy of implicational logics is then restricted to the
semilinear case obtaining a classification of implicational semilinear logics that encompasses almost all the known examples
of fuzzy logics and suggests new directions for research in the field. 相似文献
165.
We examine factorizations of complete graphs K2n into caterpillars of diameter 5. First we present a construction generalizing some previously known methods. Then we use the new method along with some previous partial results to give a complete characterization of caterpillars of diameter 5, which factorize the complete graph K2n. 相似文献
166.
167.
An information system Xemic applicable in analytical chemistry is described and its use in capillary electrophoresis for searching suitable separation conditions is demonstrated. This system is capable to provide suitable separation conditions even for analytes for which no electrophoretic experiments have been published so far. The system works with a database of components of anionic character the analyses of which have been performed, published in reviewed scientific journals, and included into a database created by an expert. Moreover, the system learned to search also in abstracts or complete scientific articles to find articles dealing with the determination of a substance in a given sample matrix. When no experiments have been published so far for a defined substance in a specific matrix, Xemic shows the separation conditions for determination of the substance regardless of the matrix. When no response can be found for the analyte of interest at all, the system Xemic works like an expert in the field and searches chemically similar substances and offers a series of substances the physicochemical properties of which are close to the followed analyte with respect to the behavior in the electric field, and shows working conditions for their analysis. Thus, the analyst puts only the order in the form of a given analyte in a given matrix and obtains a recommendation of a separation system that should enable to perform a successful separation. The system is not rigid and enables the operator to change the importance of individual attributes used in similarity search so as to obtain a broader or narrower group of similar components. With a certain probability the analyte of interest can be successfully analyzed under separation conditions that suited for the analysis of the most similar substances in the given matrix. 相似文献
168.
Lipase-catalysed (trans)esterification reactions in homogenous perfluorocarbon-hydrocarbon solvents enabled direct enantiomeric partitioning (up to 95% ee) of the products by liquid-liquid separation. 相似文献
169.
We present an analytic solution for the nondegenerate quantum control problem, i.e., the transfer of a deliberate amount of population, 0%-100%, between arbitrary initial Psi(t)> and final Psi'(t)> states, which can be expanded in terms of nondegenerate energy eigenstates k>. The solution constitutes a robust two-photon multicomponent adiabatic passage, via an intermediate eigenstate 0>, which relies on three types of "null states." 相似文献
170.
V. Petržílka 《Czechoslovak Journal of Physics》1996,46(11):1085-1091
The purpose of this study is to estimate, for planned experiments at the H-1NF heliac, nonlinear variations of the stationary radial electric field, and poloidal and toroidal plasma rotation, that result from ponderomotive forces exerted by large amplitude RF waves in the H-1NF. Similarly as in the previous studies of nonlinear transport effects induced by RF waves, the nonlinear ponderomotive force effects on the radial electric field, toroidal and poloidal plasma rotation become important for dissipated powers of the order of 1 MWm–3 for RF waves with frequency of about 10 MHz. At these high RF powers, the nonlinear ponderomotive force effects might therefore result in important changes in plasma confinement and RF wave coupling in H-1NF.This work has been partially supported by the Australian National University, by the DIST Department of the Australian Government, by the Czech Grant Agency grants No. 202/96/1355 and 1350, and by the Queen Elisabeth II grant administered by G.G. Borg. The author is grateful to G.G. Borg and R.L. Dewar for many stimulating discussions. 相似文献