全文获取类型
收费全文 | 79541篇 |
免费 | 6588篇 |
国内免费 | 5088篇 |
专业分类
化学 | 24053篇 |
晶体学 | 1840篇 |
力学 | 3566篇 |
综合类 | 345篇 |
数学 | 17720篇 |
物理学 | 43693篇 |
出版年
2022年 | 170篇 |
2021年 | 323篇 |
2020年 | 631篇 |
2019年 | 938篇 |
2018年 | 900篇 |
2017年 | 598篇 |
2016年 | 452篇 |
2015年 | 433篇 |
2014年 | 1082篇 |
2013年 | 1719篇 |
2012年 | 1180篇 |
2011年 | 1738篇 |
2010年 | 2330篇 |
2009年 | 6853篇 |
2008年 | 7892篇 |
2007年 | 6378篇 |
2006年 | 5815篇 |
2005年 | 3963篇 |
2004年 | 3813篇 |
2003年 | 4007篇 |
2002年 | 4748篇 |
2001年 | 3696篇 |
2000年 | 3517篇 |
1999年 | 3334篇 |
1998年 | 2751篇 |
1997年 | 1917篇 |
1996年 | 1733篇 |
1995年 | 2224篇 |
1994年 | 2158篇 |
1993年 | 1608篇 |
1992年 | 1115篇 |
1991年 | 836篇 |
1990年 | 682篇 |
1989年 | 612篇 |
1988年 | 574篇 |
1987年 | 408篇 |
1986年 | 194篇 |
1985年 | 948篇 |
1984年 | 616篇 |
1983年 | 489篇 |
1982年 | 643篇 |
1981年 | 793篇 |
1980年 | 722篇 |
1979年 | 560篇 |
1978年 | 581篇 |
1977年 | 538篇 |
1976年 | 540篇 |
1975年 | 317篇 |
1974年 | 354篇 |
1973年 | 463篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Discrete Mathematics》2022,345(9):112949
In this paper, we describe a result on self-conjugate -core partitions with the fixed number of corners. We also define shifted corners of a distinct partition and find formulas for the number of -core partitions and the number of -core shifted Young diagrams with the fixed number of shifted corners. 相似文献
2.
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
3.
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.
6.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(9):991-996
The three binary Tb/Er‐rich transition metal compounds Tb3Pd2 (triterbium dipalladium), Er3Pd2 (trierbium dipalladium) and Er6Co5–x (hexaerbium pentacobalt) crystallize in the space groups Pbam (Pearson symbol oP20), P4/mbm (tP10) and P63/m (hP22), respectively. Single crystals of Tb3Pd2 and Er6Co5–x suitable for X‐ray structure analysis were obtained using rare‐earth halides as a flux. Tb3Pd2 adopts its own structure type, which can be described as a superstructural derivative of the U3Si2 type, which is the type adopted by Er3Pd2. Compound Er6Co5–x belongs to the Ce6Co2–xSi3 family. All three compounds feature fused tricapped {TR6} (R = rare‐earth metal and T = transition metal) trigonal prismatic heterometallic clusters. R3Pd2 is reported to crystallize in the U3Si2 type; however, our more detailed structure analysis reveals that deviations occur with heavier R elements. Similarly, Er6Co5–x was assumed to be stoichiometric Er4Co3 = Er6Co4.5. Our studies reveal that it has a single defective transition‐metal site leading to the composition Er6Co4.72(2). LMTO (linear muffin‐tin orbital)‐based electronic structure calculations suggest the strong domination of heteroatomic bonding in all three structures. 相似文献
7.
In this paper, estimates for a trilinear operator associated with the Hartree type nonlinearity are proved. Moreover, as application of these estimates, it is proved that after a linear transformation, the Cauchy problem for the Hartree-type equation becomes locally well posed in the Bessel potential and homogeneous Besov spaces under certain regularity assumptions on the initial data. This notion of well-posedness and the functional framework to solve the equation were firstly proposed by Y. Zhou. 相似文献
8.
9.
10.