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   82619篇
  免费   14414篇
  国内免费   9426篇
化学   57911篇
晶体学   912篇
力学   5458篇
综合类   522篇
数学   9763篇
物理学   31893篇
  2024年   85篇
  2023年   1654篇
  2022年   1865篇
  2021年   2700篇
  2020年   3406篇
  2019年   3240篇
  2018年   2832篇
  2017年   2694篇
  2016年   3993篇
  2015年   3889篇
  2014年   4595篇
  2013年   6034篇
  2012年   7598篇
  2011年   7777篇
  2010年   5279篇
  2009年   5146篇
  2008年   5553篇
  2007年   4987篇
  2006年   4616篇
  2005年   3815篇
  2004年   3065篇
  2003年   2457篇
  2002年   2390篇
  2001年   2047篇
  2000年   1651篇
  1999年   1768篇
  1998年   1468篇
  1997年   1366篇
  1996年   1360篇
  1995年   1132篇
  1994年   997篇
  1993年   838篇
  1992年   714篇
  1991年   621篇
  1990年   537篇
  1989年   418篇
  1988年   355篇
  1987年   286篇
  1986年   264篇
  1985年   219篇
  1984年   149篇
  1983年   106篇
  1982年   80篇
  1981年   70篇
  1980年   67篇
  1979年   35篇
  1978年   30篇
  1977年   40篇
  1976年   30篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.

In this paper, we study a category of restricted modules for the Ovsienko-Roger algebra, which is an extension of the Virasoro algebra of its tensor density module of degree one. We construct and characterize simple modules in this category and give natural free field realizations of certain restricted modules using the Weyl vertex algebra.

  相似文献   
42.
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly.  相似文献   
43.
Transition metal Fe, Co, Ni and Cu doped strontium titanate-rich SrTiO3@TiO2 (STO@T) materials were prepared by hydrothermal method. The prepared doped materials exhibit better photocatalytic CO2 reduction to CH4 ability under visible light conditions. Among them, Fe-doped and undoped SrTiO3@TiO2 under visible light conditions CO2 reduction products only CO, while M-STO@T (M=Co, Ni, Cu) samples converted CO2 to CH4. The average methane yield of Ni-doped STO@T samples are as high as 73.85 μmol g−1 h−1. The production of methane is mainly due to the increase in the response of the doped samples to visible light. And the increase in the separation rate of photogenerated electrons and holes and the efficiency of electron transport caused by the generation of impurity levels. The impurity level caused by Ti3+ plays an important role in the production of methane by CO2 visible light reduction. Ni doping effectively improves the photocatalytic performance of STO@T and CO2 reduction mechanism were explained.  相似文献   
44.
Guo  Lan  Guan  Yali  Liu  Peng  Gao  Linghuan  Wang  Zhifu  Huang  Shengli  Peng  Liang  Zhao  Zhiyu 《Cellulose (London, England)》2022,29(3):1315-1330
Cellulose - Extracellular vesicles are membrane-packed entities that are involved in various physiological and pathological processes. Recently, the role of exosomes and microvesicles in...  相似文献   
45.
分子张力作为空间设计的重要组成部分正成为调控有机半导体的重要手段。由于分子内产生的拉伸张力、扭曲/弯曲张力以及空间张力而导致p轨道排布重组和构型构象结构发生变化,最近各种几何与拓扑结构的高张力有机半导体材料相继被报道,这使得高张力有机半导体材料成为有机电子领域研究的焦点。为了进一步梳理分子张力在有机半导体材料中扮演的角色与价值,该综述从分子张力的类型、实验与理论量化以及可视化出发,总结了高张力共轭芳烃的分子设计策略、与其光电性能分子张力之间的关系,以及这类新兴材料在光电领域的应用。最后,对高张力共轭芳烃的研究前景进行了展望,阐述了该类材料所面临的机遇与挑战。  相似文献   
46.
Great efforts have been conducted to develop high temperature proton exchange membrane fuel cell (HT-PEMFC) due to its features of enhanced electrocatalyst reactivity, simplified hydrothermal management system and high CO tolerance of catalysts, and remarkable progress has been achieved. However, the easy leaching of phosphoric acid (PA) from the membranes during operation limits its commercial scale-up in complicated environments. This concept here mainly focuses on the recent developments for mitigation of PA loss in PEMs. The probable mechanisms of PA loss are proposed. The approaches to improve PA retention for example via introduction of phosphonic acid by covalent bond, using ion-pairs interaction and siphoning effect, and blending with inorganic nanoparticles are described in detail. Among these strategies, the siphoning effect from the intrinsic microporous PEMs is the most efficient and enables the cell to operate flexibly within a broad temperature range. Therefore, this concept may provide new ideas for the scientists to retain PA, to improve the cell performance and expand the potential applications of PA doped PEMs at elevated humidity and wide temperature range.  相似文献   
47.
Journal of Radioanalytical and Nuclear Chemistry - The preparation of C30 concrete for a cavernous waste repository under construction in China and its Cs(I) adsorption performance were...  相似文献   
48.
In this paper, we study the well-posedness and the asymptotic stability of a one-dimensional thermoelastic microbeam system, where the heat conduction is given by Gurtin-Pipkin thermal law. We first establish the well-posedness of the system by using the semigroup arguments and Lumer-Phillips theorem. We then obtain an explicit and general formula for the energy decay rates through perturbed energy method and some properties of the convex functions.  相似文献   
49.
Journal of Applied Mechanics and Technical Physics - A self-equilibrated stress field for an incompressible sphere is constructed based on a non-Euclidean continuum model. The...  相似文献   
50.
Liu  Jingze  Fei  Qingguo  Wu  Shaoqing  Tang  Zhenhuan  Zhang  Dahai 《Nonlinear dynamics》2021,106(3):1869-1890
Nonlinear Dynamics - Rolling bearing and squeeze film damper will introduce structural nonlinearity into the dynamic model of aeroengine. Rubbing will occur due to the clearance reduction design 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