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   30543篇
  免费   5524篇
  国内免费   4556篇
化学   22488篇
晶体学   421篇
力学   1723篇
综合类   319篇
数学   4005篇
物理学   11667篇
  2024年   78篇
  2023年   633篇
  2022年   743篇
  2021年   1100篇
  2020年   1372篇
  2019年   1290篇
  2018年   1119篇
  2017年   1127篇
  2016年   1578篇
  2015年   1546篇
  2014年   1860篇
  2013年   2419篇
  2012年   2787篇
  2011年   2873篇
  2010年   2134篇
  2009年   1971篇
  2008年   2196篇
  2007年   1919篇
  2006年   1750篇
  2005年   1492篇
  2004年   1169篇
  2003年   971篇
  2002年   1022篇
  2001年   840篇
  2000年   657篇
  1999年   615篇
  1998年   500篇
  1997年   430篇
  1996年   428篇
  1995年   379篇
  1994年   302篇
  1993年   217篇
  1992年   213篇
  1991年   200篇
  1990年   159篇
  1989年   126篇
  1988年   71篇
  1987年   66篇
  1986年   88篇
  1985年   59篇
  1984年   34篇
  1983年   32篇
  1982年   18篇
  1981年   13篇
  1980年   5篇
  1979年   4篇
  1975年   4篇
  1974年   2篇
  1959年   2篇
  1957年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Journal of Radioanalytical and Nuclear Chemistry - This study presents a time-efficient method of analysing 210Pb, 210Bi, and 210Po in natural waters. The optimum pH (1.00), temperature...  相似文献   
3.
A graphic sequence π =(d1, d2,..., dn) is said to be forcibly k-edge-connected if every realization of π is k-edge-connected. In this paper, we obtain a new sufficient degree condition for π to be forcibly k-edgeconnected. We also show that this new sufficient degree condition implies a strongest monotone degree condition for π to be forcibly 2-edge-connected and a conjecture about a strongest monotone degree condition for π to be forcibly 3-edge-connected due to...  相似文献   
4.
Sun  Yekai  Yuan  Jie  Vizzaccaro  Alessandra  Salles  Loïc 《Nonlinear dynamics》2021,104(4):3077-3107
Nonlinear Dynamics - The nonlinear modes of a non-conservative nonlinear system are sometimes referred to as damped nonlinear normal modes (dNNMs). Because of the non-conservative...  相似文献   
5.
Gao  Zhigen  Guo  Jianhua  Ma  Yanyuan 《中国科学 数学(英文版)》2021,64(8):1905-1916
Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood...  相似文献   
6.
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA.  相似文献   
7.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
8.
9.
10.
Hierarchically porous metal–organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.  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