全文获取类型
收费全文 | 1087篇 |
免费 | 213篇 |
国内免费 | 102篇 |
专业分类
化学 | 820篇 |
晶体学 | 13篇 |
力学 | 29篇 |
数学 | 66篇 |
物理学 | 474篇 |
出版年
2024年 | 3篇 |
2023年 | 31篇 |
2022年 | 34篇 |
2021年 | 43篇 |
2020年 | 63篇 |
2019年 | 57篇 |
2018年 | 41篇 |
2017年 | 39篇 |
2016年 | 55篇 |
2015年 | 68篇 |
2014年 | 67篇 |
2013年 | 81篇 |
2012年 | 104篇 |
2011年 | 99篇 |
2010年 | 74篇 |
2009年 | 55篇 |
2008年 | 70篇 |
2007年 | 64篇 |
2006年 | 51篇 |
2005年 | 38篇 |
2004年 | 31篇 |
2003年 | 28篇 |
2002年 | 23篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1402条查询结果,搜索用时 15 毫秒
991.
Xuebin Zhu Yuping Sun Xuan Luo Hechang Lei Bosen Wang Wenhai Song Zhaorong Yang Jianming Dai Dongqi Shi Shixue Dou 《Journal of magnetism and magnetic materials》2010,322(2):242-246
Critical behavior of Ti-doped La0.7Ca0.3MnO3 ceramics are studied using magnetization methods. The results show that the paramagnetic–ferromagnetic transition is first order for the undoped sample, then for low-doping samples the mean-field model is suitable, and finally a 3D Heisenberg model is satisfied for higher doping samples. These findings demonstrate that the critical behavior of the magnetic transition for manganites is sensitive to Mn-site doping. 相似文献
992.
CeO2 buffer layers were deposited on YSZ single-crystal substrates using an RF-sputtering method. The development of crystalline textures of sputtered CeO2 films at different sputtering pressure and their effects on YBCO films, deposited by Metal Organic Deposition (MOD), were investigated. Both CeO2 and subsequent YBCO films grew well epitaxially. The relative XRD peak intensities of CeO2 (2 0 0) to substrate YSZ (2 0 0) increased with deposition pressure in the range of 3–5 mTorr and were inversely proportional to the θ–2θ scan FWHM values of CeO2 (2 0 0). Also, the reaction layers of BaCeO3 were thicker in the samples with lower CeO2 (2 0 0) intensities and poor out-of-plane alignment when CeO2 were deposited at the lower pressure of 3.3 mTorr. It is noted, however, that the superconducting layer grew well epitaxially on these BaCeO3 layers, possibly due to the epitaxial relation between CeO2 and YBCO. The superconducting critical currents of MOD-YBCO films showed an increasing tendency as both the Δ2θ (CeO2) and BaCeO3 peak intensities decreased. 相似文献
993.
994.
<正>We review the dark decay of the electronic holographic phase grating before thermal fixing,and deduce the general analytic expression of the lifetime of thermal-fixed ionic holograms in the photorefractive crystal,by means of analogizing.Because the ions are optically inactive,the lifetime of thermal-fixed ionic holograms is only closely relate to the ionic decay rate which is determined by the conductivity of ionic species at a given temperature.We theoretically analyze and numerically simulate the influences on the lifetime of ionic grating from the crucial factors in the experiment and application.The results reveal that low temperature,low ion-concentration,and large grating spacing are advantages for extending the life of the thermal-fixed volume holographic phase grating in photorefractive crystal. 相似文献
995.
996.
In this paper, binary optical elements (BOE’s) are designed for generating Bessel beams at mm- and sub mm- wavelengths. The
design tool is to combine a genetic algorithm (GA) for global optimization with a two-dimension finite-difference time-domain
(2-D FDTD) method for rigorous electromagnetic computation. The design process for converting a normally incident Gaussian
beam into a Bessel beam is described in detail. Numerical results demonstrate that the designed BOE’s can not only successfully
produce arbitrary order Bessel beams, but also have higher diffraction efficiencies when compared with amplitude holograms. 相似文献
997.
用紫外光电子能谱(UPS)研究了酞菁铜分子在Ag(110)单晶表面上的吸附,随着酞菁铜分子覆盖度增加,衬底Ag的3d电子信号逐渐减弱,在此能带区域出现两个新的谱峰,这两个与吸附有机分子轨道有关的谱峰的束缚能分别为4.45 和6.36 eV.随着覆盖度的增加,在结合能为1.51和9.20 eV处又出现了两个谱峰,它们同样来自吸附有机分子的轨道.随着覆盖度的继续增加,上述四个谱峰的强度逐渐增加,其能量位置均发生了明显的偏移.根据角分辨光电子能谱的实验结果,酞菁铜分子的分子平面基本与衬底表面平行.密度泛函理论计
关键词:
酞菁铜
紫外光电子谱
吸附电子态
密度泛函理论 相似文献
998.
Wei-Tao Dou Fugui Xu Chen-Xi Xu Jie Gao Hong-Bo Ru Xiangfeng Luan Jiacheng Zhang Ling Zhu Adam C. Sedgwick Guo-Rong Chen Yi Zang Tony D. James He Tian Jia Li Yiyong Mai Xiao-Peng He 《Chemical science》2021,12(33):11089
Triple negative breast cancer (TNBC) is one of the most malignant subtypes of breast cancer. Here, we report the construction of graphene nanoribbon (GNR)-based supramolecular ensembles with dual-receptor (mannose and αvβ3 integrin receptors) targeting function, denoted as GNR-Man/PRGD, for targeted photothermal treatment (PTT) of TNBC. The GNR-Man/PRGD ensembles were constructed through the solution-based self-assembly of mannose-grafted GNRs (GNR-Man) with a pyrene-tagged αvβ3 integrin ligand (PRGD). Enhanced PTT efficacies were achieved both in vitro and in vivo compared to that of the non-targeting equivalents. Tumor-bearing live mice were administered (tail vein) with GNR-Man/PRGD and then each mice group was subjected to PTT. Remarkably, GNR-Man/PRGD induced complete ablation of the solid tumors, and no tumor regrowth was observed over a period of 15 days. This study demonstrates a new and promising platform for the development of photothermal nanomaterials for targeted tumor therapy.Dual receptor-targeting supramolecular glycomaterials are constructed based on graphene nanoribbons for the targeted photothermal therapy of triple-negative breast cancer in vivo. 相似文献
999.
风湿性关节炎动物模型中血啉甲醚荧光强度的同步检测研究 总被引:2,自引:1,他引:1
光动力疗法的疗效依赖于治疗过程中靶组织中光敏剂的含量或浓度 ,而药物在组织中的分布特性是受动物机体调控的 ,因此 ,同一个体不同组织对光敏剂吸收的时间特性需要同时进行检测才能排除个体之间的差异。建立了一套空间三通道激光诱导荧光同步检测装置 ,并用该装置研究了活体大耳白兔风湿性关节炎模型滑膜、软骨和皮肤对血啉甲醚吸收的时间特性。研究结果表明 ,炎性滑膜组织对血啉甲醚的吸收量远大于软骨和皮肤 ,这一差别在静脉给药即刻就很明显 ,在静脉给药后 2 0min内 ,滑膜中的光敏剂药物含量约为软骨和皮肤中的 6倍。因此 ,对于借助血啉甲醚 ,用光动力疗法治疗风湿性关节炎并采用体外照射治疗方案时 ,从注药即刻开始 ,前 2 0min左右进行光照治疗可能是较好的选择。 相似文献
1000.
Luminescence characteristics of Yb3+, La3+ codoped yttrium oxide nanopowders were investigated. The grain size and the crystallinity of (Yb0.05Y0.90La0.05)2O3 nanopowders increase with the increase of calcination temperature. The average grain size of the nanopowders calcined at 1100 °C is 66 nm and its cooperative up-conversion luminescence centered at 498 nm was detected due to nanometer size effect and perfect crystallinity. However, the cooperative up-conversion luminescence of (Yb0.05Y0.90La0.05)2O3 transparent ceramics was not detected. 相似文献