全文获取类型
收费全文 | 2630篇 |
免费 | 125篇 |
国内免费 | 217篇 |
专业分类
化学 | 213篇 |
晶体学 | 1篇 |
力学 | 79篇 |
综合类 | 38篇 |
数学 | 2434篇 |
物理学 | 207篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 33篇 |
2021年 | 35篇 |
2020年 | 38篇 |
2019年 | 52篇 |
2018年 | 59篇 |
2017年 | 54篇 |
2016年 | 66篇 |
2015年 | 49篇 |
2014年 | 108篇 |
2013年 | 172篇 |
2012年 | 93篇 |
2011年 | 113篇 |
2010年 | 103篇 |
2009年 | 158篇 |
2008年 | 199篇 |
2007年 | 152篇 |
2006年 | 146篇 |
2005年 | 140篇 |
2004年 | 103篇 |
2003年 | 115篇 |
2002年 | 94篇 |
2001年 | 97篇 |
2000年 | 93篇 |
1999年 | 95篇 |
1998年 | 83篇 |
1997年 | 68篇 |
1996年 | 64篇 |
1995年 | 35篇 |
1994年 | 31篇 |
1993年 | 31篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 4篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 22篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1936年 | 1篇 |
排序方式: 共有2972条查询结果,搜索用时 31 毫秒
81.
Difference systems of sets (DSS) are combinatorial configurations that arise in connection with code synchronization. This paper proposes a new method to construct DSSs, which uses known DSSs to partition some of the cosets of Zv relative to subgroup of order k, where v = km is a composite number. As applications, we obtain some new optimal DSSs. 相似文献
82.
Behnam Vahdani S. Meysam Mousavi R. Tavakkoli-Moghaddam H. Hashemi 《Applied Mathematical Modelling》2013
The purpose of this paper is to design a new extension of the ELECTRE, known as the elimination and choice translating reality method, for multi-criteria group decision-making problems based on intuitionistic fuzzy sets. This method is widely utilized when a set of alternatives should be identified and evaluated with respect to a set of conflicting criteria by reflecting decision makers’ (DMs’) preferences. However, handling the exact data and numerical measure is difficult to be precisely focused because the DMs’ judgments are often vague in real-life decision problems and applications. A more realistic and practical approach can be to use linguistic variables expressed in intuitionistic fuzzy numbers instead of numerical data to model DMs’ judgments and to describe the inputs in the ELECTRE method. The proposed intuitionsitic fuzzy ELECTRE utilizes the truth-membership function and non-truth-membership function to indicate the degrees of satisfiability and non-satisfiability of each alternative with respect to each criterion and the relative importance of each criterion, respectively. Then, a new discordance intuitionistic index is introduced, which is extended from the concept of the fuzzy distance measure. Outranking relations are defined by pairwise comparisons and a decision graph is depicted to determine which alternative is preferable, incomparable or indifferent in the intuitionistic fuzzy environment. Finally, a comprehensive sensitivity analysis is employed to further study regarding the impact of threshold values on the final evaluation, and a comparative analysis is demonstrated with an application example in flexible manufacturing systems between the proposed ELECTRE method and the existing intuitionistic fuzzy technique for order preference by similarity to ideal solution (IF-TOPSIS) method. 相似文献
83.
S. K. Kim K. T. Atanassov A. G. Shannon 《International Journal of Mathematical Education in Science & Technology》2013,44(2):173-179
The purpose of this paper is to explain the basic theory of generalized nets (GNs) and their applications in the context of the differential diagnosis of neurological diseases. We define formally the concepts of a GN and transitions of a GN and also outline some remarks on their theory. The work here constructs an example which aims to trace the process of diagnosing different signs and symptoms in neurology. This will enable the interested reader to see the scope of nets in general as tools for the modelling, simulation, optimization and control of real processes. 相似文献
84.
罗伟 《数学的实践与认识》2014,(18)
针对Vague集评价过程中信息容易遗失的问题,提出采用Vague综合评价的思想进行计算.通过定义Vague基本运算法则,以及建立加权综合评价函数构建了新的评价方法.方法体现了Vague集理论描述不确定性问题的优点,反映了项目经理评价的一般特点.最后,通过案例计算,得到了公平公正的评价结果,并验证了计算结果的可靠性. 相似文献
85.
《International Journal of Approximate Reasoning》2014,55(7):1606-1608
This note replies to comments made on our contribution to the Low Quality Data debate. 相似文献
86.
87.
Influence theory is a foundational theory of physics that is not based on traditional empirically defined concepts, such as positions in space and time, mass, energy, or momentum. Instead, the aim is to derive these concepts, and their empirically determined relationships, from a more primitive model. It is postulated that there exist things, which are call particles, that influence one another in a discrete and directed fashion resulting in a partially ordered set of influence events. The problem of consistent quantification of the influence events is considered. Observers are modeled as particle chains (observer chains) as if an observer were able to track a particle and quantify the influence events that the particle experiences. From these quantified influence events, consistent quantification of the universe of events based on the observer chains is studied. Herein, the kinematics and dynamics of particles from the perspective of influence theory are both reviewed and further developed. 相似文献
88.
ABSTRACT In this paper, we present a systematic roadmap for developing a robust and parallel multi-material reactive hydrodynamic solver that integrates historically stable algorithms with new and current modern methods to solve explosive system design problems. The Ghost Fluid Method and Riemann solvers were used to enforce appropriate interface boundary conditions. Improved performance in terms of computational work and convergence properties was achieved by modifying a local node sorting strategy that decouples ghost nodes, allowing us to set material boundary conditions via an explicit procedure, removing the need to solve a coupled system of equations numerically. The locality and explicit nature of the node sorting concept allows for greater levels of parallelism and lower computational cost when populating ghost nodes. Non-linear numerical issues endemic to the use of real Equations of State in hydro-codes were resolved by using more thermodynamically consistent forms allowing us to accurately resolve large density gradients associated with high energy detonation problems at material interfaces. Pre-computed volume tables were implemented adding to the robustness of the solver base. 相似文献
89.
AbstractWe study the inverse problem of parameter identification in noncoercive variational problems that commonly appear in applied models. We examine the differentiability of the set-valued parameter-to-solution map using the first-order and the second-order contingent derivatives. We explore the inverse problem using the output least-squares and the modified output least-squares objectives. By regularizing the noncoercive variational problem, we obtain a single-valued regularized parameter-to-solution map and investigate its smoothness and boundedness. We also consider optimization problems using the output least-squares and the modified output least-squares objectives for the regularized variational problem. We give a complete convergence analysis showing that for the output least-squares and the modified output least-squares, the regularized minimization problems approximate the original optimization problems suitably. We also provide the first-order and the second-order adjoint method for the computation of the first-order and the second-order derivatives of the output least-squares objective. We provide discrete formulas for the gradient and the Hessian calculation and present numerical results. 相似文献
90.
Iran Sheikhshoaie Helen Stoeckli-Evans Alireza Akbari S. Ali Yasrebi S. Yousef Ebrahimipour 《Arabian Journal of Chemistry》2012,5(2):173-178
The crystal and molecular structure of methanol {E-N′-(2-hydroxybenzlidene)benzohydrazido}dioxidomolybdenum (VI) was determined by single crystal X-ray diffraction. B3LYP/DZP basis set theoretical calculations nicely reproduce the X-ray experimental geometry. The obtained results are discussed in connection with the electronic and structural properties of the compound. 相似文献