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   77922篇
  免费   11786篇
  国内免费   8111篇
化学   52845篇
晶体学   777篇
力学   5218篇
综合类   641篇
数学   9911篇
物理学   28427篇
  2024年   69篇
  2023年   1485篇
  2022年   1577篇
  2021年   2258篇
  2020年   2842篇
  2019年   2745篇
  2018年   2465篇
  2017年   2204篇
  2016年   3330篇
  2015年   3437篇
  2014年   4117篇
  2013年   5481篇
  2012年   6697篇
  2011年   7072篇
  2010年   4842篇
  2009年   4815篇
  2008年   5073篇
  2007年   4561篇
  2006年   4270篇
  2005年   3614篇
  2004年   2880篇
  2003年   2190篇
  2002年   1926篇
  2001年   1755篇
  2000年   1609篇
  1999年   1711篇
  1998年   1452篇
  1997年   1268篇
  1996年   1346篇
  1995年   1204篇
  1994年   1092篇
  1993年   952篇
  1992年   829篇
  1991年   741篇
  1990年   607篇
  1989年   537篇
  1988年   400篇
  1987年   380篇
  1986年   325篇
  1985年   319篇
  1984年   218篇
  1983年   194篇
  1982年   158篇
  1981年   121篇
  1980年   84篇
  1978年   58篇
  1977年   53篇
  1975年   57篇
  1974年   53篇
  1973年   57篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Niu  Mu-Qing  Chen  Li-Qun 《Nonlinear dynamics》2021,103(3):2227-2240
Nonlinear Dynamics - Nonlinear vibration isolation provides with an effective way for vibration reduction with broad band and high efficiency. This investigation focuses on the dynamic effects of a...  相似文献   
72.
International Journal of Theoretical Physics - In this work, we give an analytical derivation of the reduced density matrix between two qubits in a cavity field, which is described by the quantum...  相似文献   
73.
Chen  Hao  Jones  Nathan  Serban  Vlad 《The Ramanujan Journal》2022,59(2):379-436
The Ramanujan Journal - Inspired by the work of Lang–Trotter on the densities of primes with fixed Frobenius traces for elliptic curves defined over $${\mathbb {Q}}$$ and by the subsequent...  相似文献   
74.
Chen  Liang  Zhu  Junyuan  Zhao  Xinyuan 《中国科学 数学(英文版)》2022,65(11):2397-2422
Science China Mathematics - In this paper, we accomplish the unified convergence analysis of a second-order method of multipliers (i.e., a second-order augmented Lagrangian method) for solving the...  相似文献   
75.
Inspired by the intriguing structures and remarkable activities of sesquiterpenoid dimers,12 new sesquiterpenoid dimers,artematrovirenolides A—D(1—4)and artematrolides S—Z(8—12),were isolated from the EtOAc fraction of Artemisia atrovirens through a bioactivity-guided approach.Their structures were elucidated by comprehensive spectroscopic data and absolute configuration was assigned based on single crystal X-ray diffraction data and ECD calculations.Structurally,all compounds are presumably formed via[4+2]cycloaddition involving three connecting model.Compounds 1—4 are four novel hetero-dimeric[4+2]Diels-Alder adducts dimerized from a rotundane-type unit and a guaiane-type monomer,and compounds 5—12 are eight new homo-dimeric[4+2]adducts derived from two guaianolide moieties.A putative biosynthetic pathway for compounds 1—4 was also proposed.Compounds 4,6,7,and 10 demonstrated moderate cytotoxicity against HepG2,SMMC-7721,and Huh7 cell lines with IC50 values ranging from 9.3 to 62.3μmol/L.Interestingly,compounds 5 and 11 manifested cytotoxicity with IC50 values of 13.6 and 12.8(HepG2),18.5 and 13.1(SMMC-7721),and 16.5 and 19.4μmol/L(Huh7),respectively,which were equivalent to the positive control,sorafenib.This investigation suggests that compounds 5 and 11 might be considered as potent antihepatoma candidates and deserve further structural modification and mechanism study.  相似文献   
76.
77.
Jia  Yonghao  Chen  Xiulong 《Nonlinear dynamics》2022,108(3):2161-2191
Nonlinear Dynamics - Contact and friction phenomena in clearance joint adversely affect mechanical performance and may even result in chaos within the mechanism. Analysis of nonlinear...  相似文献   
78.
Chen  Haiyang  Gao  Fangzheng 《Nonlinear dynamics》2022,108(2):1319-1338
Nonlinear Dynamics - Based on a mixed control strategy, this study addresses the finite-time stabilization with extended dissipativity for Markov jump systems (MJSs) with unreliable...  相似文献   
79.
We report theoretical studies of electron impact triple differential cross sections of two bio-molecules,pyrimidine and tetrahydrofurfuryl alcohol,in the coplanar asymmetric kinematic conditions with the impact energy of 250 eV and ejected electron energy of 20 eV at three scattering angles of-5°,-10°,and-15°.Present multi-center distorted-wave method well describes the experimental data,which was obtained by performing(e,2e)experiment.The calculations show that the secondary electron produced by the primary impact electron is strongly influenced by the molecular ionic multi-center potential,which must be considered when the low energy electron interacts with DNA analogues.  相似文献   
80.
Hu  Yinlong  Hua  Tianyang  Chen  Michael Z. Q.  Shi  Shang  Sun  Yonghui 《Nonlinear dynamics》2021,105(1):99-112
Nonlinear Dynamics - In this paper, the instability of semi-active control systems caused by the utilization of semi-active inerters is analyzed. The purpose of this study is to demonstrate the...  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