全文获取类型
| 收费全文 | 1147篇 |
| 免费 | 65篇 |
| 国内免费 | 23篇 |
专业分类
| 化学 | 36篇 |
| 晶体学 | 5篇 |
| 力学 | 19篇 |
| 综合类 | 8篇 |
| 数学 | 607篇 |
| 物理学 | 560篇 |
出版年
| 2025年 | 2篇 |
| 2024年 | 11篇 |
| 2023年 | 14篇 |
| 2022年 | 21篇 |
| 2021年 | 27篇 |
| 2020年 | 46篇 |
| 2019年 | 40篇 |
| 2018年 | 29篇 |
| 2017年 | 32篇 |
| 2016年 | 28篇 |
| 2015年 | 31篇 |
| 2014年 | 70篇 |
| 2013年 | 111篇 |
| 2012年 | 45篇 |
| 2011年 | 62篇 |
| 2010年 | 32篇 |
| 2009年 | 57篇 |
| 2008年 | 67篇 |
| 2007年 | 60篇 |
| 2006年 | 54篇 |
| 2005年 | 71篇 |
| 2004年 | 65篇 |
| 2003年 | 54篇 |
| 2002年 | 30篇 |
| 2001年 | 23篇 |
| 2000年 | 36篇 |
| 1999年 | 15篇 |
| 1998年 | 20篇 |
| 1997年 | 5篇 |
| 1996年 | 6篇 |
| 1995年 | 12篇 |
| 1994年 | 4篇 |
| 1993年 | 6篇 |
| 1992年 | 8篇 |
| 1991年 | 4篇 |
| 1990年 | 3篇 |
| 1989年 | 10篇 |
| 1988年 | 8篇 |
| 1987年 | 1篇 |
| 1986年 | 3篇 |
| 1985年 | 3篇 |
| 1984年 | 2篇 |
| 1983年 | 1篇 |
| 1982年 | 1篇 |
| 1978年 | 1篇 |
| 1977年 | 2篇 |
| 1975年 | 1篇 |
| 1970年 | 1篇 |
排序方式： 共有1235条查询结果，搜索用时 15 毫秒
971.
972.
ZHANG Honglin;YANG Zhitao;WANG Yusa;ZHAO Zijian;MA Jia;HOU Dongjie;YANG Xiongtao;ZHU Yuxuan;YAN Yanji;CHEN Yong;WANG Shijie 《光子学报》2023,52(5):233-243
One of the crucial components of an X-ray focusing lens's performance test is effective area calibration. The focusing lens will be calibrated on the ground before being launched into space. The X-ray source can't achieve the ideal condition of an incident on the mirror in parallel due to the distance restriction of the ground experimental device, so its calibration results will be different from those in orbit. In order to understand and correct the discrepancy between the effective area of the Wolter-Ⅰ X-ray focusing lens in ground calibration and in-orbit calibration, the effective area of the X-ray telescope carried by the Einstein probe was simulated and analyzed under two calibration conditions. The ground calibration experiment of effective area was carried out in the 100-meter X-ray calibration device of the Institute of High Energy Physics, Chinese Academy of Sciences.First, prior to designing the light source, the calibration model is created, then the incident conditions of on-orbit and ground light sources are taken into consideration. The program makes use of X-ray sources with energies of 1.49 keV, 4.5 keV, and 8.5 keV. Second, the light source used for the on-orbit calibration can be thought of as a parallel light source while the light source used for the ground calibration can be considered a point source. The effective area of the focusing lens under the two calibrations is determined using the two incident light sources to mimic the ground calibration and the on-orbit calibration, respectively. The deviation percentage of their effective areas is determined using the simulation data. To determine the connection between the effective area and the off-axis angle, the off-axis analysis of the focusing lens's effective area is performed within 1°, and the change diagram of the off-axis effective area is drawn. Lastly, the ground calibration experiment is run in the Institute of High Energy's 100-meter calibration device. The effective area of the focusing lens is determined using the photon count on the monitor before and after the addition of the focusing lens in the experiment, which employs continuous spectrum X-rays. The useful area is corrected based on the simulation-derived deviation ratio. In a similar manner, the off-axis experiment is conducted within 1, and the change diagram of the experiment's off-axis effective area is made.The findings indicate that when the X-ray energy is 1.49 keV, 4.5 keV, and 8.5 keV correspondingly, the effective area of ground calibration is 2.7%, 3.0%, and 4.0%, bigger than that of on-orbit calibration. The difference between them increases with increasing X-ray energy. This phenomenon is compatible with the energy-dependent decrease in X-ray reflectivity. In the simulation and experiment, the off-axis angle affects the focusing mirror's effective area, which falls by 20% when the off-axis angle approaches 10'. The research presented in this paper demonstrates that the effective area of ground calibration is always greater than the effective area of on-orbit calibration and that the effective area of on-orbit calibration of the focusing lens can be predicted using ground calibration data combined with simulation. The off-axis effective area of the focusing lens also demonstrates a clear relationship with the off-axis angle. This study's methodology can offer data references for the Wolter-Ⅰ focusing mirror-equipped X-ray astronomy satellite's effective area calibration. 相似文献
973.
974.
We analyze the existence and stability of two kinds of self-trapped spatially localized gap modes,gap solitons and truncated nonlinear Bloch waves,in one-and two-dimensional optical or matter-wave media with self-focusing nonlinearity,supported by a combination of linear and nonlinear periodic lattice potentials.The former is found to be stable once placed inside a single well of the nonlinear lattice,it is unstable otherwise.Contrary to the case with constant self-focusing nonlinearity,where the latter solution is always unstable,here,we demonstrate that it nevertheless can be stabilized by the nonlinear lattice since the model under consideration combines the unique properties of both the linear and nonlinear lattices.The practical possibilities for experimental realization of the predicted solutions are also discussed. 相似文献
975.
Xiao-Bing Zhang 《理论物理通讯》2020,72(11):115302-73
In this paper, we study the influences of magnetic fields on the coexistence of diquark and chiral condensates in an extended Nambu–Jona–Lasinio model with QCD axial anomaly, as it relates to color-flavor-locked quark matter. Due to the coupling of rotated-charged quarks to magnetic fields, diquark condensates become split, and the coexistence region is thus superseded in favor of a specific diquark Bose–Einstein condensation (BEC), denoted as the BECI phase. For strong magnetic fields, we find that the BECI transition is pushed to larger quark chemical potentials. The effect of magnetic catalysis tends to disrupt the BEC–BCS (Bardeen–Cooper–Schrieffer) crossover predicted in previous works. For intermediate fields, the effect of inverse magnetic catalysis is observed, and the axial-anomaly-induced phase structure is essentially unchanged. 相似文献
976.
主要研究双扭曲积Hermitian流形的各种曲率,给出了紧致非平凡的双扭曲积Hermitian流形具有常全纯截面曲率的充要条件,得到了一种构造满足第一或第二爱因斯坦条件的Hermitian流形的有效方法. 相似文献
977.
We use the wide-used Einstein Toolkit to solve the Einstein constraints and then simulate the expansion of primordial black hole lattices (PBHLs) with different value of $f_{mathrm{PBH}}$ and $m_{mathrm{PBH}}$. We find that $f_{mathrm{PBH}}$ plays an important role during the evolution of PBHLs. Since the motion of primordial black holes (PBHs) caused by the expansion of PBHLs occurs at speeds close to that of light, we expect the emission of gravitational waves (GWs) during the expansion of PBHLs. We use both analytical estimates and numerical simulations to cross check the production of GWs in expanding PBHLs. 相似文献
978.
成品油配送多车舱车辆指派及路径优化问题研究 总被引：3，自引：0，他引：3
针对成品油配送中多车型、多车舱的车辆优化调度难题,综合考虑多车型车辆指派、多车舱车辆装载及路径安排等决策,以派车成本与油耗成本之和的总成本最小为目标,建立了多车型多车舱的车辆优化调度模型。为降低模型求解的复杂性,本文提出一种基于C-W节约算法的“需求拆分→合并装载”的车辆装载策略,并综合利用Relocate和Exchange算子进行并行邻域搜索改进,获得优化的成品油配送方案。最后,通过算例验证了本文提出的模型与算法用于求解大规模成品油配送问题的有效性。并通过数据实验揭示了以下规律:1)多车舱车辆相对于单车舱车辆在运营成本上具有优越性;2)大型车辆适合远距离配送,小型车辆适合近距离配送;3)多车型车辆混合配送相对于单车型车辆配送在运营成本上具有优越性。这些规律可为成品油配送公司的车辆配置提供决策参考。 相似文献
979.
张量广义逆是张量理论研究的重要内容之一.在近年张量广义逆研究的基础上,该文给出在爱因斯坦积下张量core逆的性质、张量偏序和张量方程A*X = B在条件X∈R(A)下的最小二乘解等. 相似文献
980.
微腔激子极化激元是激子和微腔光子形成的叠加态,是一种兼具光与物质双重属性的准粒子,在基础物理研究和未来光子芯片应用方面具有重要的价值。从1992年首次实验观测到微腔极化激元至今已有整整30年。文章回顾这30年来微腔激子极化激元领域的发展历史与重要成果,并对未来的研究方向做了展望。将重点介绍微腔激子极化激元的概念、形成过程及其玻色—爱因斯坦凝聚的原理,简述以此为基础的极化激元光流体、物态调控及量子效应。 相似文献