首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   100023篇
  免费   4230篇
  国内免费   2971篇
化学   39822篇
晶体学   1031篇
力学   8035篇
综合类   251篇
数学   34374篇
物理学   23711篇
  2023年   494篇
  2022年   497篇
  2021年   677篇
  2020年   982篇
  2019年   889篇
  2018年   10980篇
  2017年   10786篇
  2016年   7013篇
  2015年   1821篇
  2014年   1523篇
  2013年   1925篇
  2012年   5789篇
  2011年   12422篇
  2010年   6980篇
  2009年   7328篇
  2008年   8039篇
  2007年   10064篇
  2006年   1574篇
  2005年   2389篇
  2004年   2388篇
  2003年   2662篇
  2002年   1584篇
  2001年   751篇
  2000年   783篇
  1999年   710篇
  1998年   659篇
  1997年   550篇
  1996年   604篇
  1995年   498篇
  1994年   432篇
  1993年   415篇
  1992年   319篇
  1991年   292篇
  1990年   281篇
  1989年   215篇
  1988年   178篇
  1987年   139篇
  1986年   153篇
  1985年   111篇
  1984年   80篇
  1983年   76篇
  1982年   78篇
  1981年   60篇
  1980年   54篇
  1979年   48篇
  1914年   45篇
  1913年   40篇
  1912年   40篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Nanoparticle Research - Polycrystalline metallic copper nanoparticle samples with the average particle sizes ranging from 53 to 80 nm were controllably prepared by the wet...  相似文献   
2.
Atopic dermatitis is characterized by leukocyte migration into the skin dermis and typically driven by excessive chemokine production at the site of inflammation. Conventional topical formulations such as gels, creams, and ointments are insufficient for this treatment because of low penetration of drug molecules into the targeted skin tissues. Herein, using a simple, green, sustainable strategy, we have developed novel primary zein nanoparticles embedded in curcumin (Cur) and coated with silk sericin (ZHSCs) for the topical delivery of Cur to penetrate into the dermis and exercise anti-dermatitis effects on the lesion with minimal side-effects. Transdermal delivery experiments and porcine skin fluorescence imaging indicated that ZHSCs facilitate the penetration of Cur across the epidermis layer of skin to reach deep-seated sites. Notably, ZHSCs = 1:0.25 (zein-to-silk sericin mass ratios of 1:0.25) markedly elevated the skin permeability and cumulative turnover of Cur transferred, which were provided a greater than a 3.8-fold increase relative to free Cur. The special nanoparticles of ZHS = 1:0.25 possessed the deepest localization depth and experience a transition of the particle structure and core-shell separation after penetrating into the dermis of skin. In a cell model of dermatitis induced by tumor necrosis factor α/interferon γ co-stimulation, compared with free Cur, Cur-loaded ZHS nanoparticles down-regulated the generation of inflammatory cytokines and chemokines in keratinocytes through suppression of the nuclear translocation of NF-κBp65 and hence exerted an anti-dermatitis effect. This strategy may provide new avenues and direction for the demanding issues of valid topical delivery systems.  相似文献   
3.
陈华俊  朱鹏杰  陈咏雷  侯宝成 《中国物理 B》2022,31(2):27802-027802
We investigate theoretically Rabi-like splitting and Fano resonance in absorption spectra of quantum dots(QDs)based on a hybrid QD-semiconducting nanowire/superconductor(SNW/SC)device mediated by Majorana fermions(MFs).Under the condition of pump on-resonance and off-resonance,the absorption spectrum experiences the conversion from Fano resonance to Rabi-like splitting in different parametric regimes.In addition,the Fano resonances are accompanied by the rapid normal phase dispersion,which will indicate the coherent optical propagation.The results indicate that the group velocity index is tunable with controlling the interaction between the QD and MFs,which can reach the conversion between the fast-and slow-light.Fano resonance will be another method to detect MFs and our research may indicate prospective applications in quantum information processing based on the hybrid QD-SNW/SC devices.  相似文献   
4.
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.
Liu  Qingrong  Li  Hanfeng  Zhu  Fei  Zhang  Xianfu 《Nonlinear dynamics》2021,103(3):2659-2669
Nonlinear Dynamics - This paper proposes an output feedback control strategy to achieve the global regulation of a class of large-scale feedforward nonlinear systems with discrete and distributed...  相似文献   
6.
7.
Zhu  Jie-Xiang 《Potential Analysis》2021,55(1):167-188
Potential Analysis - We establish some exact asymptotic results for a matching problem with respect to a family of beta distributions. Let X1,…,Xn be independent random variables with common...  相似文献   
8.
International Journal of Theoretical Physics - In this paper, we investigate Einstein-Podolsky-Rosen steering, Bell non-locality, first-order coherence and concurrence in the spin- $\frac {1}{2}$...  相似文献   
9.
Ding  Wei  Han  YongSheng  Zhu  YuePing 《Potential Analysis》2021,55(3):419-441
Potential Analysis - The purpose of this paper is to provide necessary and sufficient conditions of the boundedness for singular integrals on the local Hardy space and its dual. Particularly the...  相似文献   
10.
Zhu  Min  Li  Jun-ping  Liu  De-zhi 《应用数学学报(英文版)》2021,37(3):617-627
Acta Mathematicae Applicatae Sinica, English Series - So far there have been few results presented on the exponential stability for time-changed stochastic differential equations. The main aim of...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号