全文获取类型
收费全文 | 164625篇 |
免费 | 14785篇 |
国内免费 | 10165篇 |
专业分类
化学 | 51478篇 |
晶体学 | 2230篇 |
力学 | 11064篇 |
综合类 | 1698篇 |
数学 | 59624篇 |
物理学 | 63481篇 |
出版年
2023年 | 1042篇 |
2022年 | 1138篇 |
2021年 | 2630篇 |
2020年 | 2901篇 |
2019年 | 3181篇 |
2018年 | 2845篇 |
2017年 | 2917篇 |
2016年 | 3281篇 |
2015年 | 2920篇 |
2014年 | 5068篇 |
2013年 | 9120篇 |
2012年 | 5367篇 |
2011年 | 6832篇 |
2010年 | 6880篇 |
2009年 | 12213篇 |
2008年 | 13461篇 |
2007年 | 11938篇 |
2006年 | 10311篇 |
2005年 | 7695篇 |
2004年 | 7187篇 |
2003年 | 7254篇 |
2002年 | 7367篇 |
2001年 | 5824篇 |
2000年 | 5463篇 |
1999年 | 4964篇 |
1998年 | 4299篇 |
1997年 | 3342篇 |
1996年 | 3055篇 |
1995年 | 3318篇 |
1994年 | 3163篇 |
1993年 | 2566篇 |
1992年 | 2051篇 |
1991年 | 1547篇 |
1990年 | 1226篇 |
1989年 | 1087篇 |
1988年 | 1053篇 |
1987年 | 798篇 |
1986年 | 609篇 |
1985年 | 1517篇 |
1984年 | 1098篇 |
1983年 | 730篇 |
1982年 | 1088篇 |
1981年 | 1230篇 |
1980年 | 1096篇 |
1979年 | 959篇 |
1978年 | 858篇 |
1977年 | 731篇 |
1976年 | 699篇 |
1974年 | 407篇 |
1973年 | 547篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
A general framework for describing photofission observables of actinides at an average excitation energy below 30 MeV 下载免费PDF全文
Guan-Lin Wang Hao-Yang Lan Xiao-Ming Shi Zhi-Chao Zhu Wen Luo 《中国物理C(英文版)》2022,46(8):084102-084102-14
A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications, such as short-lived isotope production, nuclear waste disposal, and nuclear safeguards. However, the available experimental data for photofission observables are limited, and the existing models and programs have mainly been developed for neutron-induced fission processes. In this study, a general framework is proposed for characterizing the photofission observables of actinides, including the mass yield distributions (MYD) and isobaric charge distributions (ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons (np) and prompt γ rays (γp). The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as input. These models are then validated individually against experimental data at an average excitation energy below 30 MeV, which shows the reliability and robustness of the general framework. Finally, we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including 232Th, 235, 238U and 240Pu. It is found that the 238U(γ, f) reaction is more suitable for producing neutron-rich nuclei compared to the 232Th(γ, f) reaction. In addition, the average multiplicity number of both np and γp increases with the average excitation energy. 相似文献
5.
Liquid-liquid-solid systems are becoming increasingly common in everyday life with many possible applications. Here, we focus on a special case of such liquid-liquid-solid systems, namely, capillary suspensions. These capillary suspensions originate from particles that form a network based on capillary forces and are typically composed of solids in a bulk liquid with an added secondary liquid. The structure of particle networks based on capillary bridges possesses unique properties compared with networks formed via other attractive interactions where these differences are inherently related to the properties of the capillary bridges, such as bridge breaking and coalescence between adjacent bridges. Thus, to tailor the mechanical properties of capillary suspensions to specific requirements, it is important to understand the influences on different length scales ranging from the dynamics of the bridges with varying external stimuli to the often heterogeneous network structure. 相似文献
6.
Here we propose and analyze a mathematical model that aims to describe the marble sulphation process occurring in a given material. The model accounts for rugosity as well as for damaging effects. This model is characterized by some technical difficulties that seem hard to overcome from a theoretical viewpoint. Therefore, we introduce some physically reasonable modifications in order to establish the existence of a suitable notion of solution on a given time interval. Numerical simulations are presented and discussed, also in view of further research. 相似文献
7.
8.
Based on the primal mixed variational formulation, a stabilized nonconforming mixed finite element method is proposed for the linear elasticity on rectangular and cubic meshes. Two kinds of penalty terms are introduced in the stabilized mixed formulation, which are the jump penalty term for the displacement and the divergence penalty term for the stress. We use the classical nonconforming rectangular and cubic elements for the displacement and the discontinuous piecewise polynomial space for the stress, where the discrete space for stress are carefully chosen to guarantee the well-posedness of discrete formulation. The stabilized mixed method is locking-free. The optimal convergence order is derived in the $L^2$-norm for stress and in the broken $H^1$-norm and $L^2$-norm for displacement. A numerical test is carried out to verify the optimal convergence of the stabilized method. 相似文献
9.
《Operations Research Letters》2022,50(6):699-706
A classical sampling strategy for load balancing policies is power-of-two, where any server pair is sampled with equal probability. This does not cover practical settings with assignment constraints which force non-uniform sampling. While intuition suggests that non-uniform sampling adversely impacts performance, this was only supported through simulations, and rigorous statements have remained elusive. Building on product-form distributions for redundancy systems, we prove the stochastic dominance of uniform sampling for a four-server system as well as arbitrary-size systems in light traffic. 相似文献
10.