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   351564篇
  免费   5894篇
  国内免费   1104篇
化学   195263篇
晶体学   4620篇
力学   14268篇
综合类   7篇
数学   42815篇
物理学   101589篇
  2021年   2133篇
  2020年   2529篇
  2019年   2503篇
  2018年   2816篇
  2017年   2574篇
  2016年   5123篇
  2015年   4382篇
  2014年   5537篇
  2013年   16309篇
  2012年   13444篇
  2011年   16157篇
  2010年   9963篇
  2009年   9580篇
  2008年   14688篇
  2007年   14863篇
  2006年   14248篇
  2005年   13169篇
  2004年   11714篇
  2003年   10197篇
  2002年   9849篇
  2001年   10639篇
  2000年   8185篇
  1999年   6458篇
  1998年   5160篇
  1997年   4979篇
  1996年   5124篇
  1995年   4585篇
  1994年   4383篇
  1993年   4218篇
  1992年   4726篇
  1991年   4526篇
  1990年   4233篇
  1989年   4062篇
  1988年   4298篇
  1987年   3977篇
  1986年   3818篇
  1985年   5571篇
  1984年   5639篇
  1983年   4548篇
  1982年   4976篇
  1981年   5007篇
  1980年   4741篇
  1979年   4842篇
  1978年   4853篇
  1977年   4786篇
  1976年   4791篇
  1975年   4674篇
  1974年   4540篇
  1973年   4692篇
  1972年   2654篇
排序方式: 共有10000条查询结果,搜索用时 29 毫秒
71.
Methodology and Computing in Applied Probability - The problem of optimally controlling one-dimensional diffusion processes until they enter a given stopping set is extended to include Markov...  相似文献   
72.
73.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
74.
Xu  H. J.  Zhang  Q. G.  Debenest  G. 《Transport in Porous Media》2021,140(3):625-627
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...  相似文献   
75.
Optical and Quantum Electronics - In the past few decades, the academic research and industrial synergy is dramatically accelerating to conceptualize high data rate services. The congestion in the...  相似文献   
76.
It is known that under resonance conditions, a group of strongly interacting bosonic atoms, trapped in a double-well potential, mimics a single particle, performing Rabi oscillations between the wells. By implication, all atoms need to tunnel at roughly the same time, even though the Bose–Hubbard Hamiltonian accounts only for one-atom-at-a-time transfers. The mechanism of this collective behavior is analyzed, the Rabi frequencies in the process are evaluated, and the limitation of this simple picture is discussed. In particular, it is shown that the small rapid oscillations superimposed on the slow Rabi cycle result from splitting the transferred cluster at the sudden onset of tunnelling, and disappear if tunnelling is turned on gradually.  相似文献   
77.
Partially fluorinated poly(arylene ether sulfone) multiblock copolymers bearing perfluorosulfonic functions (ps‐PES‐FPES), with ionic exchange capacity (IEC) ranging between 0.9 and 1.5 meq H+/g, are synthesized by regioselective bromination of partially fluorinated poly(arylene ether sulfone) multiblock copolymers (PES‐FPES), followed by Ullman coupling reaction with lithium 1,1,2,2‐tetrafluoro‐2‐(1,1,2,2‐tetrafluoro‐2‐iodoethoxy)ethanesulfonate. The PES‐FPES are prepared by aromatic nucleophilic substitution reaction by an original approach, that is, “one pot two reactions synthesis.” The chemical structures of polymers are analyzed by 1H and 19F NMR spectroscopy. The resulted ionomers present two distinct glass transitions and α relaxations revealing phase separation between the hydrophilic and the hydrophobic domains. The phase separation is observed at much lower block lengths of ps‐PES‐FPES as compared with the literature. AFM and SANS observations supported the phase separation, the hydrophilic domains are well dispersed but the connectivity to each other depends on the ps‐PES block lengths. The thermomechanical behavior, the water up‐take, and the conductivity of the ps‐PES‐FPES membranes are compared with those of Nafion 117® and randomly functionalized polysulfone (ps‐PES). Conductivities close or higher to those of Nafion 117® are obtained. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1941–1956  相似文献   
78.
79.
80.
Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min.  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