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   269377篇
  免费   2453篇
  国内免费   630篇
化学   143484篇
晶体学   4038篇
力学   11947篇
综合类   9篇
数学   29881篇
物理学   83101篇
  2019年   2328篇
  2018年   3133篇
  2017年   3126篇
  2016年   4536篇
  2015年   2715篇
  2014年   4348篇
  2013年   10759篇
  2012年   8184篇
  2011年   10020篇
  2010年   7163篇
  2009年   6933篇
  2008年   9402篇
  2007年   9627篇
  2006年   9006篇
  2005年   8182篇
  2004年   7496篇
  2003年   6804篇
  2002年   6735篇
  2001年   7379篇
  2000年   5691篇
  1999年   4398篇
  1998年   3895篇
  1997年   3868篇
  1996年   3604篇
  1995年   3363篇
  1994年   3524篇
  1993年   3215篇
  1992年   3702篇
  1991年   3691篇
  1990年   3624篇
  1989年   3486篇
  1988年   3600篇
  1987年   3502篇
  1986年   3315篇
  1985年   4400篇
  1984年   4661篇
  1983年   3893篇
  1982年   4022篇
  1981年   3960篇
  1980年   3941篇
  1979年   3898篇
  1978年   4220篇
  1977年   4130篇
  1976年   4201篇
  1975年   3827篇
  1974年   3890篇
  1973年   4035篇
  1972年   2838篇
  1971年   2368篇
  1970年   2182篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
81.
Sukhorukova  O. S.  Tarasenko  A. S.  Tarasenko  S. V.  Shavrov  V. G. 《JETP Letters》2020,112(7):420-427
JETP Letters - At the resonant passage of a plane elastic shear wave through an acoustically continuous heterostructure consisting of magnetic and nonmagnetic layers in a symmetric nonmagnetic...  相似文献   
82.
Optics and Spectroscopy - The transmission of intrinsic, antimony-doped, and gallium-doped Ge single crystals in the THz spectral range have been experimentally investigated. It is shown that the...  相似文献   
83.
Droplet evaporation characterization, although of great significance, is still challenging. The recently developed phase rainbow refractometry (PRR) is proposed as an approach to measuring the droplet temperature, size as well as evaporation rate simultaneously, and is applied to a single flowing n-heptane droplet produced by a droplet-on-demand generator. The changes of droplet temperature and evaporation rate after a transient spark heating are reflected in the time-resolved PRR image. Results show that droplet evaporation rate increases with temperature, from ?1.28×10?8 m2/s at atmospheric 293 K to a range of (?1.5, ?8)×10?8 m2/s when heated to (294, 315) K, agreeing well with the Maxwell and Stefan–Fuchs model predictions. Uncertainty analysis suggests that the main source is the indeterminate gradient inside droplet, resulting in an underestimation of droplet temperature and evaporation rate. With the demonstration on simultaneous measurements of droplet refractive index as well as droplet transient and local evaporation rate in this work, PRR is a promising tool to investigate single droplet evaporation in real engine conditions.  相似文献   
84.
85.
86.
87.
88.
89.
In the present work we describe a two‐dimensional liquid chromatographic system (2D‐LC) with detection by mass spectrometry (MS) for the simultaneous separation of endogenous metabolites of clinical interest and excreted xenobiotics deriving from exposure to toxic compounds. The 2D‐LC system involves two orthogonal chromatographic modes, hydrophilic interaction liquid chromatography (HILIC) to separate polar endogenous metabolites and reversed‐phase (RP) chromatography to separate excreted xenobiotics of low and intermediate polarity. Additionally, the present proposal has the novelty of incorporating an on‐line sample treatment based on the use of restricted access materials (RAMs), which permits the direct injection of urine samples into the system. The work is focused on the instrumental coupling, studying all possible options and attempting to circumvent the problems of solvent incompatibility between the RAM device and the two chromatographic columns, HILIC and RP. The instrumental configuration developed, RAM‐HILIC‐RPLC‐MS/MS, allows the simultaneous assessment of urinary metabolites of clinical interest and excreted compounds derived from exposure to toxic agents with minimal sample manipulation. Thus, it may be of interest in areas such as occupational and environmental toxicology in order to explore the possible relationship between the two types of compounds. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
90.
Technical Physics - The influence of SiO2 impurity (with a concentration varying from 0 to 10 mol %) on the stability of tetragonal ZrO2 (t-ZrO2) and on a set of micro- and macromechanical...  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