全文获取类型
收费全文 | 2520篇 |
免费 | 20篇 |
国内免费 | 32篇 |
专业分类
化学 | 65篇 |
力学 | 40篇 |
综合类 | 22篇 |
数学 | 2276篇 |
物理学 | 169篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 28篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 27篇 |
2016年 | 37篇 |
2015年 | 29篇 |
2014年 | 100篇 |
2013年 | 148篇 |
2012年 | 132篇 |
2011年 | 162篇 |
2010年 | 105篇 |
2009年 | 199篇 |
2008年 | 136篇 |
2007年 | 182篇 |
2006年 | 147篇 |
2005年 | 100篇 |
2004年 | 77篇 |
2003年 | 67篇 |
2002年 | 74篇 |
2001年 | 110篇 |
2000年 | 79篇 |
1999年 | 64篇 |
1998年 | 67篇 |
1997年 | 55篇 |
1996年 | 52篇 |
1995年 | 39篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 49篇 |
1984年 | 48篇 |
1983年 | 19篇 |
1982年 | 38篇 |
1981年 | 32篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1978年 | 3篇 |
排序方式: 共有2572条查询结果,搜索用时 15 毫秒
1.
《Discrete Mathematics》2022,345(11):112983
We determine the 22 isomorphism classes of 4-GDDs with group type and compare their automorphism groups. We also observe for the first time an example of a three dimensional Pasch triangle in a GDD. 相似文献
2.
Group isomorphism and homomorphism are topics central to abstract algebra, yet research on instructors’ views of these concepts is limited. Based on interviews from two instructors as well as classroom video from eight class periods, this paper examines the language used to discuss isomorphism and homomorphism. Language used by instructors in interviews and classroom settings are identified and classified into four main categories: formal definition, mapping, sameness, and combinations of sameness and mapping language. How the two instructors drew on language classified into those four categories in the interview and instruction settings are examined for isomorphism and homomorphism. Similarities and differences between the interview and instruction contexts reveal the wide variety of ways of understanding isomorphism and homomorphism as well as a research need to examine mathematicians’ content knowledge in more than one context. 相似文献
3.
计算区间二型模糊集的质心(也称降型)是区间二型模糊逻辑系统中的一个重要模块。Karnik-Mendel(KM)迭代算法通常被认为是计算区间二型模糊集质心的标准算法。尽管如此,KM算法涉及复杂的计算过程,不利于实时应用。在各种改进类算法中,非迭代的Nie-Tan(NT)算法可节省计算消耗。此外,连续版本NT(CNT,continuous version of NT)算法被证明是计算质心的准确算法。本文比较了离散版本NT算法中求和运算和连续版本NT算法中求积分运算,通过四个计算机仿真例子证实了当适度增加区间二型模糊集主变量采样个数时,NT算法的计算结果可以精确地逼近CNT算法。 相似文献
4.
5.
In this paper we investigated the stability of fractional order fuzzy cellular neural networks with leakage delay and time varying delays. Based on Lyapunov theory and applying bounded techniques of fractional calculation, sufficient criterion are established to guarantee the stability. Hybrid feedback control is applied to derive the proposed results. Finally, numerical examples with simulation results are given to illustrate the effectiveness of the proposed method. 相似文献
6.
In this paper we present a new approach, based on the Nearest Interval Approximation Operator, for dealing with a multiobjective programming problem with fuzzy-valued objective functions. 相似文献
7.
The Analytic Hierarchy Process (AHP) is a measurement methodology based on pair-wise comparisons that relies on judgment to derive priority scales. During its implementation, one constructs hierarchies, then makes judgments or performs measurements on pairs of elements with respect to a criterion to derive preference scales, which are then synthesized throughout the structure to select the preferred alternative.One of the areas where the AHP finds application is in the subjective phases of risk assessment (RA), where it is used to structure and prioritize diverse risk factors, including the judgments of experts. Since fuzzy logic (FL) has been shown to be an effective tool for accommodating human experts and their communication of linguistic variables, there has been research aimed at modeling the fuzziness in the AHP (FAHP), and recently the focus of some of that modeling has been with respect to RA.The literature discusses more than one FAHP model, which raises the question as to which are the prominent models and what are their characteristics. In response to this question, we examine three of the most influential FAHP models. The article proceeds as follows. It begins with a brief overview of the AHP and its limitations when confronted with a fuzzy environment. This is followed by a discussion of FL modifications of the AHP. A RA-based likelihood score example is used throughout. The article ends with a commentary on the findings. 相似文献
8.
This paper extends the framework for the valuation of life insurance policies and annuities by Andrés-Sánchez and González-Vila (2012, 2014) in two ways. First we allow various uncertain magnitudes to be estimated by means of fuzzy numbers. This applies not only to interest rates but also to the amounts to be paid out by the insurance company. Second, the use of symmetrical triangular fuzzy numbers allows us to obtain expressions for the pricing of life contingencies and their variability that are closely linked to standard financial and actuarial mathematics. Moreover, they are relatively straightforward to compute and understand from a standard actuarial point of view. 相似文献
9.
Existing risk capital allocation methods, such as the Euler rule, work under the explicit assumption that portfolios are formed as linear combinations of random loss/profit variables, with the firm being able to choose the portfolio weights. This assumption is unrealistic in an insurance context, where arbitrary scaling of risks is generally not possible. Here, we model risks as being partially generated by Lévy processes, capturing the non-linear aggregation of risk. The model leads to non-homogeneous fuzzy games, for which the Euler rule is not applicable. For such games, we seek capital allocations that are in the core, that is, do not provide incentives for splitting portfolios. We show that the Euler rule of an auxiliary linearised fuzzy game (non-uniquely) satisfies the core property and, thus, provides a plausible and easily implemented capital allocation. In contrast, the Aumann–Shapley allocation does not generally belong to the core. For the non-homogeneous fuzzy games studied, Tasche’s (1999) criterion of suitability for performance measurement is adapted and it is shown that the proposed allocation method gives appropriate signals for improving the portfolio underwriting profit. 相似文献
10.