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   2891篇
  免费   196篇
  国内免费   44篇
化学   2006篇
晶体学   35篇
力学   124篇
综合类   4篇
数学   373篇
物理学   589篇
  2024年   17篇
  2023年   60篇
  2022年   92篇
  2021年   248篇
  2020年   181篇
  2019年   176篇
  2018年   152篇
  2017年   125篇
  2016年   195篇
  2015年   134篇
  2014年   147篇
  2013年   250篇
  2012年   210篇
  2011年   243篇
  2010年   139篇
  2009年   127篇
  2008年   135篇
  2007年   110篇
  2006年   85篇
  2005年   66篇
  2004年   39篇
  2003年   37篇
  2002年   33篇
  2001年   12篇
  2000年   11篇
  1999年   8篇
  1998年   8篇
  1997年   4篇
  1996年   10篇
  1995年   10篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1991年   3篇
  1989年   6篇
  1988年   7篇
  1987年   5篇
  1986年   4篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1979年   2篇
  1976年   3篇
  1973年   2篇
  1971年   1篇
  1970年   1篇
  1968年   1篇
  1964年   1篇
排序方式: 共有3131条查询结果,搜索用时 2 毫秒
1.
Russian Journal of Applied Chemistry - Owing to high stability, metal oxide-based ceramic thin films are of great interest for photocatalytic oxidation of water. Therefore, the current research is...  相似文献   
2.
Journal of Solid State Electrochemistry - Protonic ceramic fuel cells have become extremely interesting due to their high power output at the intermediate temperature range...  相似文献   
3.
The ever‐increasing resistance of plant microbes towards fungicides and bactericides has been causing serious threat to plant production in recent years. For the development of an effective antifungal agent, we introduce a novel hydrothermal protocol for synthesis of chitosan iron oxide nanoparticles (CH‐Fe2O3 NPs) using acetate buffer of low pH 5.0 for intermolecular interaction of Fe2O3 NPs and CH. The composite structure and elemental elucidation were carried out by using X‐ray power diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray (EDX), Transmission Electron Microscopy (TEM), Fourier Transformed Infrared Spectroscopy (FTIR) and Ultraviolet Visible Absorption Spectroscopy (UV–vis spectroscopy). Additionally, antifungal activity was evaluated both In vitro and In vivo against Rhizopus oryzae which is causing fruit rot disease of strawberry. We compared different concentrations (0.25%, 0.50%, 075% and 1%) of CH‐Fe2O3 NPs and 50% synthetic fungicide (Matalyxal Mancozab) to figure out suitable concentration for application in the field. XRD analysis showed a high crystalline nature of the NPs with average size of 52 nanometer (nm). SEM images revealed spherical shape with size range of 50–70 nm, whereas, TEM also revealed spherical shape, size ranging from 0 nm to 80 nm. EDX and FTIR results revealed presence of CH on surface of Fe2O3 NPs. The band gap measurement showed peak 317–318 nm for bare Fe2O3 NPs and CH‐Fe2O3 NPs respectively. Antifungal activity in both In vitro and In vivo significantly increased with increase in concentration. The overall results revealed high synergetic antifungal potential of organometallic CH‐Fe2O3 NPs against Rhizopus oryzae and suggest the use of CH‐Fe2O3 NPs against other Phyto‐pathological diseases due to biodegradable nature.  相似文献   
4.
Various types of data become available at different stages of a reservoir’s life. The production data are integrated into the flow simulation models through a process referred to as history matching. The history-matching process is iterative, and it usually involves a large number of simulation runs. Hence, this process requires significant computational time. In most history-matching methods, the initial geological assumptions in the reservoir model are destroyed or significantly altered in the process. Furthermore, they do not account for the information obtained during the previous trials, and lack learning from the previous failures. In this paper, we introduce a new methodology that maintains the geological realism. The candidate realizations are selected through a learning-based history-matching (LHM) algorithm by which all the previously successful patterns are preserved and used to assist the construction of the next realizations. The various pieces of matching regions are assembled together to make a pool of the successful candidates. Such regions are then utilized for making an auxiliary dataset in a multiscale framework by which the next model is generated. To prevent from trapping in local minima, ideas from the genetic algorithm is adapted. The LHM algorithm can be applied to both categorical and continuous distributions. The LHM provides a conditional map by which the new production data are immediately incorporated into the existing reservoir models. We apply the LHM algorithm to various 2D and 3D examples with very complex binary and continuous properties. The algorithm is shown to produce history-matched models with significantly smaller CPU times.  相似文献   
5.
In this paper we study the Cauchy problem of the incompressible fractional Navier-Stokes equations in critical variable exponent Fourier-Besov-Morrey space F Ns(·)p(·),h(·),q(R3)with s(·)=4-2α-3/p(·).We prove global well-posedness result with small initial data belonging to FN4-2α-3/p(·)p(·),h(·)q(R3).The result of this paper extends some recent work.  相似文献   
6.
7.
Nonlinear Dynamics - In this paper, we propose and numerically study a nonlinear, asymmetric, passive metamaterial that achieves giant non-reciprocity with (i) broadband frequency operation and...  相似文献   
8.
9.
10.
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