全文获取类型
收费全文 | 86558篇 |
免费 | 7075篇 |
国内免费 | 5323篇 |
专业分类
化学 | 24511篇 |
晶体学 | 1859篇 |
力学 | 4168篇 |
综合类 | 388篇 |
数学 | 23548篇 |
物理学 | 44482篇 |
出版年
2022年 | 235篇 |
2021年 | 396篇 |
2020年 | 819篇 |
2019年 | 1127篇 |
2018年 | 1092篇 |
2017年 | 807篇 |
2016年 | 667篇 |
2015年 | 599篇 |
2014年 | 1394篇 |
2013年 | 2402篇 |
2012年 | 1430篇 |
2011年 | 2141篇 |
2010年 | 2704篇 |
2009年 | 7301篇 |
2008年 | 8424篇 |
2007年 | 6818篇 |
2006年 | 6207篇 |
2005年 | 4310篇 |
2004年 | 4070篇 |
2003年 | 4250篇 |
2002年 | 4934篇 |
2001年 | 3853篇 |
2000年 | 3637篇 |
1999年 | 3459篇 |
1998年 | 2843篇 |
1997年 | 2036篇 |
1996年 | 1830篇 |
1995年 | 2291篇 |
1994年 | 2215篇 |
1993年 | 1662篇 |
1992年 | 1164篇 |
1991年 | 877篇 |
1990年 | 717篇 |
1989年 | 633篇 |
1988年 | 603篇 |
1987年 | 423篇 |
1986年 | 233篇 |
1985年 | 984篇 |
1984年 | 666篇 |
1983年 | 527篇 |
1982年 | 686篇 |
1981年 | 832篇 |
1980年 | 757篇 |
1979年 | 602篇 |
1978年 | 611篇 |
1977年 | 555篇 |
1976年 | 560篇 |
1975年 | 321篇 |
1974年 | 361篇 |
1973年 | 474篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
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
4.
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
5.
In this work, we present and analyze a mathematical model for tumor growth incorporating ECM erosion, interstitial flow, and the effect of vascular flow and nutrient transport. The model is of phase-field or diffused-interface type in which multiple phases of cell species and other constituents are separated by smooth evolving interfaces. The model involves a mesoscale version of Darcy’s law to capture the flow mechanism in the tissue matrix. Modeling flow and transport processes in the vasculature supplying the healthy and cancerous tissue, one-dimensional (1D) equations are considered. Since the models governing the transport and flow processes are defined together with cell species models on a three-dimensional (3D) domain, we obtain a 3D–1D coupled model. 相似文献
6.
7.
8.
9.
10.
Phan Quoc Khanh 《Numerical Functional Analysis & Optimization》2018,39(1):100-125
We propose a definition of a generalized type of Knaster–Kuratowski–Mazurkiewicz (KKM) mappings, called a weak T-KKM mapping, and a corresponding weak KKM property. A new extension of the Fan–Glicksberg fixed-point theorem is established. Sufficient conditions for the existence of a continuous selection, a fixed point of a composition, and a coincidence point are also provided. Then, we use the obtained results to study the existence of solutions to various optimization-related problems. Discussions and detailed examples are included as well to compare our results with existing ones and to explain their advantages in many situations. 相似文献