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   17404篇
  免费   743篇
  国内免费   90篇
化学   10349篇
晶体学   234篇
力学   480篇
综合类   1篇
数学   1162篇
物理学   3587篇
无线电   2424篇
  2024年   87篇
  2023年   246篇
  2022年   600篇
  2021年   635篇
  2020年   677篇
  2019年   680篇
  2018年   651篇
  2017年   568篇
  2016年   818篇
  2015年   529篇
  2014年   877篇
  2013年   1456篇
  2012年   1214篇
  2011年   1225篇
  2010年   837篇
  2009年   668篇
  2008年   819篇
  2007年   805篇
  2006年   654篇
  2005年   575篇
  2004年   436篇
  2003年   366篇
  2002年   286篇
  2001年   195篇
  2000年   171篇
  1999年   128篇
  1998年   98篇
  1997年   129篇
  1996年   132篇
  1995年   95篇
  1994年   90篇
  1993年   118篇
  1992年   117篇
  1991年   89篇
  1990年   88篇
  1989年   80篇
  1988年   59篇
  1987年   56篇
  1986年   51篇
  1985年   80篇
  1984年   78篇
  1983年   57篇
  1982年   52篇
  1981年   53篇
  1980年   55篇
  1979年   65篇
  1978年   58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 0 毫秒
21.
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   
22.
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   
23.
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   
24.
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   
25.
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   
26.
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   
27.
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   
28.
29.
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   
30.

Alendronate sodium is widely used in the treatment of osteoporosis and Paget’s disease. The HPLC method development for alendronate sodium, in particular, is challenging owing to the absence of chromophoric group and its high polarity. In the present study, a short and simple isocratic method was developed involving hydrophilic interaction liquid chromatography, coupled with a charged aerosol detector. The developed method was validated according to the ICH Q2(R1) guideline and was successfully applied for the analysis of a marketed formulation containing the drug.

  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