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   158460篇
  免费   15262篇
  国内免费   9658篇
化学   81241篇
晶体学   1656篇
力学   11651篇
综合类   465篇
数学   40521篇
物理学   47846篇
  2024年   319篇
  2023年   1828篇
  2022年   3189篇
  2021年   3318篇
  2020年   3654篇
  2019年   3457篇
  2018年   12718篇
  2017年   12408篇
  2016年   9808篇
  2015年   4958篇
  2014年   5242篇
  2013年   6662篇
  2012年   11434篇
  2011年   17874篇
  2010年   10723篇
  2009年   10775篇
  2008年   11811篇
  2007年   13254篇
  2006年   4597篇
  2005年   4868篇
  2004年   4270篇
  2003年   4087篇
  2002年   2955篇
  2001年   1897篇
  2000年   1805篇
  1999年   1845篇
  1998年   1592篇
  1997年   1502篇
  1996年   1579篇
  1995年   1219篇
  1994年   1061篇
  1993年   914篇
  1992年   764篇
  1991年   684篇
  1990年   575篇
  1989年   472篇
  1988年   409篇
  1987年   345篇
  1986年   329篇
  1985年   267篇
  1984年   188篇
  1983年   141篇
  1982年   124篇
  1981年   107篇
  1980年   111篇
  1979年   78篇
  1978年   65篇
  1977年   59篇
  1976年   47篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Hyper-parallel quantum information processing is a promising and beneficial research field. Herein, a method to implement a hyper-parallel controlled-phase-flip (hyper-CPF) gate for frequency-, spatial-, and time-bin-encoded qubits by coupling flying photons to trapped nitrogen vacancy (NV) defect centers is presented. The scheme, which differs from their conventional parallel counterparts, is specifically advantageous in decreasing against the dissipate noise, increasing the quantum channel capacity, and reducing the quantum resource overhead. The gate qubits with frequency, spatial, and time-bin degrees of freedom (DOF) are immune to quantum decoherence in optical fibers, whereas the polarization photons are easily disturbed by the ambient noise.  相似文献   
113.
114.
115.
Germanium dioxide (GeO2) aqueous solutions are facilely prepared and the corresponding anode buffer layers (ABLs) with solution process are demonstrated. Atomic force microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements show that solution-processed GeO2 behaves superior film morphology and enhanced work function. Using GeO2 as ABL of organic light-emitting diodes (OLEDs), the visible device with tris(8-hydroxy-quinolinato)aluminium as emitter gives maximum luminous efficiency of 6.5 cd/A and power efficiency of 3.5 lm/W, the ultraviolet device with 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter exhibits short-wavelength emission with peak of 376 nm, full-width at half-maximum of 42 nm, maximum radiance of 3.36 mW/cm2 and external quantum efficiency of 1.5%. The performances are almost comparable to the counterparts with poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as ABL. The current, impedance, phase and capacitance as a function of voltage characteristics elucidate that the GeO2 ABL formed from appropriate concentration of GeO2 aqueous solution favors hole injection enhancement and accordingly promoting device performance.  相似文献   
116.
117.
Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
118.
阐明了引入溶剂渗透因子的必要性,较详细地介绍了两种渗透因子及它们间的关系。  相似文献   
119.
120.
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis.  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