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   16771篇
  免费   728篇
  国内免费   86篇
化学   9930篇
晶体学   229篇
力学   464篇
综合类   1篇
数学   1116篇
物理学   3498篇
无线电   2347篇
  2024年   63篇
  2023年   235篇
  2022年   522篇
  2021年   619篇
  2020年   668篇
  2019年   668篇
  2018年   632篇
  2017年   555篇
  2016年   799篇
  2015年   521篇
  2014年   854篇
  2013年   1412篇
  2012年   1165篇
  2011年   1203篇
  2010年   810篇
  2009年   641篇
  2008年   771篇
  2007年   770篇
  2006年   620篇
  2005年   541篇
  2004年   414篇
  2003年   355篇
  2002年   277篇
  2001年   190篇
  2000年   162篇
  1999年   125篇
  1998年   93篇
  1997年   125篇
  1996年   130篇
  1995年   92篇
  1994年   88篇
  1993年   117篇
  1992年   113篇
  1991年   89篇
  1990年   87篇
  1989年   79篇
  1988年   59篇
  1987年   56篇
  1986年   51篇
  1985年   77篇
  1984年   71篇
  1983年   57篇
  1982年   50篇
  1981年   50篇
  1980年   54篇
  1979年   64篇
  1978年   57篇
  1977年   59篇
  1976年   46篇
  1975年   36篇
排序方式: 共有10000条查询结果,搜索用时 462 毫秒
21.
A facile synthetic strategy towards conformationally stable chiral chromophores based on dimeric porphyrinoids has been established. A peculiar class of face-to-face intramolecularly interlocked corrole dimers were formed by the oxidative C−C coupling linked at the inner carbon sites upon simple treatment of copper(II) ions. Their intrinsic electronic structures were modulated by the peripheral corrole ring annulations, which lead to distinct optical properties and redox profiles. The stereogenic carbon centers implemented in the confused corrole skeleton provided a rationale for designing novel chiral materials.  相似文献   
22.
Wireless Personal Communications - Data security is currently become a serious concern in wireless communication system for both the users and providers. Without a secure medium, the data...  相似文献   
23.
Journal of Thermal Analysis and Calorimetry - In the case of flow boiling, the prediction of vapour fraction in the horizontal microchannel is a severe issue using the numerical technique....  相似文献   
24.
Wireless Networks - A novel approach is proposed to detect protocol misbehavior using state-of-the-art machine learning frameworks and entropy. Nodes in Vehicular Ad Hoc Networks (VANETs) use...  相似文献   
25.
Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,...  相似文献   
26.
In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor.  相似文献   
27.
Semiconductors - In the present paper, analytical modeling of surface potential and drain current for hetero-dielectric double gate tunnel FET (HDG-TFET) has been done. The two dimensional (2D)...  相似文献   
28.
Molecular Diversity - The antifungals that are in current clinical practice have a high occurrence of a side effect and multidrug resistance (MDR). Researchers across the globe are trying to...  相似文献   
29.
30.
Plant derived flavonoids have not been well explored in tissue engineering applications due to difficulties in efficient formulations with biomaterials for controlled presentation. Here, the authors report that surface coating of epigallocatechin gallate (EGCG) on polymeric substrates including poly (L‐lactic acid) (PLLA) nanofibers can be performed via oxidative polymerization of EGCG in the presence of cations, enabling regulation of biological functions of multiple cell types implicated in bone regeneration. EGCG coating on the PLLA nanofiber promotes osteogenic differentiation of adipose‐derived stem cells (ADSCs) and is potent to suppress adipogenesis of ADSCs while significantly reduces osteoclastic maturation of murine macrophages. Moreover, EGCG coating serves as a protective layer for ADSCs against oxidative stress caused by hydrogen peroxide. Finally, the in vivo implantation of EGCG‐coated nanofibers into a mouse calvarial defect model significantly promotes the bone regeneration (61.52 ± 28.10%) as compared to defect (17.48 ± 11.07%). Collectively, the results suggest that EGCG coating is a simple bioinspired surface modification of polymeric biomaterials and importantly can thus serve as a promising interface for tuning activities of multiple cell types associated with bone fracture healing.  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