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   10113篇
  免费   1912篇
  国内免费   1604篇
化学   7981篇
晶体学   141篇
力学   640篇
综合类   107篇
数学   1365篇
物理学   3395篇
  2024年   17篇
  2023年   159篇
  2022年   206篇
  2021年   320篇
  2020年   375篇
  2019年   440篇
  2018年   359篇
  2017年   314篇
  2016年   521篇
  2015年   596篇
  2014年   608篇
  2013年   764篇
  2012年   900篇
  2011年   905篇
  2010年   724篇
  2009年   692篇
  2008年   724篇
  2007年   594篇
  2006年   532篇
  2005年   488篇
  2004年   444篇
  2003年   407篇
  2002年   517篇
  2001年   429篇
  2000年   266篇
  1999年   230篇
  1998年   194篇
  1997年   139篇
  1996年   120篇
  1995年   119篇
  1994年   90篇
  1993年   70篇
  1992年   61篇
  1991年   59篇
  1990年   38篇
  1989年   31篇
  1988年   24篇
  1987年   29篇
  1986年   27篇
  1985年   11篇
  1984年   16篇
  1983年   12篇
  1982年   4篇
  1981年   12篇
  1980年   7篇
  1979年   7篇
  1978年   4篇
  1976年   3篇
  1974年   5篇
  1971年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We investigate Co/Nb multilayers to explore the spontaneous π-phase shift between the superconducting (SC) layers, which is attributed for causing the non-monotonic change of the SC transition temperature (Tc) with the ferromagnetic (FM) layer thickness (tFM) in several FM/SC multilayered systems. The issue of interfacial roughness is also explored by growing Co/Nb multilayers at various sputtering pressures. Transport measurements show a non-monotonic dependence of Tc on tFM, and this dependence is insensitive to the structural variation present in the samples, as measured by X-ray scattering.  相似文献   
82.
In this paper, we study the positive steady states of a prey-predator model with diffusion throughout and a non-monotone conversion rate under the homogeneous Dirichlet boundary condition. We obtain some results of the existence and non-existence of positive steady states. The stability and uniqueness of positive steady states are also discussed.  相似文献   
83.
This paper reviews our recent experimental and simulation results regarding the electromagnetic wave transmission through three configurations of sandwiching structures of metamaterials: a metallic mesh sandwiched between two identical layers composed of split rings, metallic fractals, and fractal slits, respectively. We observed the enhanced transmission of the waves through these three types of sandwiching composites with respect to the opaque metallic mesh. The locations of the transmission peaks in the spectrum are associated closely with the band characteristics of the sandwiching layer by appearing either on the left- or the right-hand side of its band. PACS 41.20.Jb; 42.70.Qs; 78.20.-e; 42.25.Bs; 47.53.+n  相似文献   
84.
ChemoselectiveCatalyticHydrogenationofα,β┐UnsaturatedKetonesandα,β┐UnsaturatedCarboxylicEstersZHANGJing-wen*,ZHAOJian-zhang,Z...  相似文献   
85.
The modified quantum nonlinear Schrodinger equation of ultra-short pulse propagating in fiber is derived using dispersion relation and the Hamiltonian of the transmission system. The derived equation is solved with linearization approximation, and modulation instability is analyzed. The equation is also solved with Hartree approximation. The results indicate that pulse power, loss and self-steeping effect change the critical frequency, the maximum gain and the gain spectrum range, but the third order dispersion has no effect on modulation instability. The expectation value of optical field is average of a set of modified classical solitons, and higher order terms change the amplitude, pulse position and phase of soliton.  相似文献   
86.
EucalyPtusgl0bulusLabill.(Myrtaceae)isakindofmedicinalplantwidelydistributedintheYunnanpr0vinceofChina.ItSleaves,rootSandffoitShavebeenusedastraditionalremediesforthetreatmentofinfluenza,dysentery,enteritis,rheumatalgiaandbleeding.BesidesvolatileterpenoidconstituentSintheessential0iloftheleavesandfruits,theoccurrenceofanumber0fphloroglucinol-sesquiterpene-or-m0n0terpene-c0upledcomPoundsnamedmacrocarpals'andeugl0bals'intheleavesandbudshasbeenrepofted.Inordertostudythechendcalandbioactivecon…  相似文献   
87.
Differentkindsofopenchaincrownethershavebeensynthesizedasthemodelcompoundsofionophoresandtheirinteractionswithsodium,potassiumandrareearthionshavealsobeenstudiedl'z.PanshowedCe(III)yieldedalf1complexwithl,8-bis(8'-quinolyloxy)-3,6-dioxaandtheCe(IIl)ioncoordinatedbothtoetheroxygenandquinolinenitrogenatoms3.TUmInleridentifiedtwolanthanidenitratecomplexeshavingastoichiometryof3:2(3RE:2L)'.InordertostUdythefunctionsofbothquinolineandbenzenering,introducedintothepolyetherchain,a1inearpolyether…  相似文献   
88.
陈荣  温彩霞 《光子学报》1998,27(1):56-59
分别采用功率密度为1.7W/cm2、照射剂量为2000J/cm2的Ar+激光与LD激光辐照高耐药性的志贺氏福氏痢疾杆菌,波长较短的Ar+激光(488nm)所引起细菌的致死率与药敏实变率明显高于波长较长的LD激光(808nm),即波长较短的Ar+激光的辐照导致细菌耐药性显著降低.  相似文献   
89.
In this paper, a natural R + n+1 extension of singular integrals, i.e.,T κ:fK t *t with K a standard C-Z kernel and ϕ usual one, is investigated. One of the main results is: Let (dμ, udx) ∈C1 and u-Mw, w∈A, then Tk is of type (Lp(udx), Lp(dμ)). As a related topic, a maximal operator is proved to be of type , where , provided (dμ, udx) ∈C1 and u∈ A. Supported by National Science Foundation of China  相似文献   
90.
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