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   9444篇
  免费   1830篇
  国内免费   1317篇
化学   7089篇
晶体学   135篇
力学   466篇
综合类   99篇
数学   958篇
物理学   3844篇
  2024年   41篇
  2023年   205篇
  2022年   366篇
  2021年   400篇
  2020年   449篇
  2019年   493篇
  2018年   398篇
  2017年   366篇
  2016年   536篇
  2015年   534篇
  2014年   619篇
  2013年   780篇
  2012年   930篇
  2011年   885篇
  2010年   670篇
  2009年   569篇
  2008年   641篇
  2007年   603篇
  2006年   483篇
  2005年   396篇
  2004年   278篇
  2003年   241篇
  2002年   279篇
  2001年   276篇
  2000年   166篇
  1999年   192篇
  1998年   126篇
  1997年   84篇
  1996年   81篇
  1995年   58篇
  1994年   65篇
  1993年   60篇
  1992年   54篇
  1991年   54篇
  1990年   49篇
  1989年   34篇
  1988年   25篇
  1987年   23篇
  1986年   13篇
  1985年   12篇
  1984年   8篇
  1983年   13篇
  1982年   8篇
  1981年   4篇
  1980年   7篇
  1979年   3篇
  1978年   4篇
  1976年   2篇
  1959年   2篇
  1936年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
A piezoelectric nucleic acid sensor was constructed ofr detection of tumor necrosis factor gene.Two methods were employed for immobilization of nucleic acid probe on gold electrode of piezoelectric crystal.The results show that polyethyleneimine adbesion and glutaraldehyde cross-linking method has higher sensitivity,stability and selectivity than protein A method.The solid-phase nucleic acid hybridization of oligo unclecotides and tumor necrosis factor target gene sequence were monitorde using this sensor.Tumor necrosis factor gene sequence(580bp) was detected by this nucleic acid sensor for the first time.  相似文献   
72.
Upon the electrochemical oxidation of tris(2,2′-bipyridyl) ruthenium(II) [Ru(bpy)2+3] and hydroxyl carboxylic acids, for instance, citric acid, tartaric acid, malic acid, and -gluconic acid, bright electrochemiluminescences (ECLs) were observed. Different luminescent reactions were presented depending on the applied potential. The light emission was mainly caused by the reaction between alkoxide radical ion and Ru(bpy)3+3below the potential +1.80 V (vs Ag/AgCl). The luminescence intensity obviously increased because of the more complex reaction process. The luminescence wavelength of 608 nm, which could be found either at higher potential than +1.80 V or in the potential range from +1.30 to +1.80 V, confirmed that ECL was caused by Ru(bpy)2+3*. The factors which affect the determination and HPLC separation of the four acids were also investigated.  相似文献   
73.
利用邻苯三酚自氧化法监测了磷酸盐缓冲体系中水杨酸(SA)对超氧化物歧化酶(SOD)活力的影响。通过荧光光谱法研究了水杨酸与超氧化物歧化酶的相互作用机制,求得两者结合的形成常数和配位数,使用Forster非辐射能量转移技术求出了两者的结合位置距色氨酸残基间的距离为2.60nm。  相似文献   
74.
Cell lysis was demonstrated on a microfluidic CD (Compact Disc) platform. In this purely mechanical lysis method, spherical particles (beads) in a lysis chamber microfabricated in a CD, cause disruption of mammalian (CHO-K1), bacterial (Escherichia coli), and yeast (Saccharomyces cerevisiae) cells. Interactions between beads and cells are generated in the rimming flow established inside a partially filled annular chamber in the CD rotating around a horizontal axis. To maximize bead-cell interactions in the lysis chamber, the CD was spun forward and backwards around this axis, using high acceleration for 5 to 7 min. Investigation on inter-particle forces (friction and collision) identified the following parameters; bead density, angular velocity, acceleration rate, and solid volume fraction as having the most significant contribution to cell lysis. Cell disruption efficiency was verified either through direct microscopic viewing or measurement of the DNA concentration after cell lysing. Lysis efficiency relative to a conventional lysis protocol was approximately 65%. In the long term, this work is geared towards CD based sample-to-answer nucleic acid analysis which will include cell lysis, DNA purification, DNA amplification, and DNA hybridization detection.  相似文献   
75.
IntroductionTheintramolecularenergytransferprocessandmechanismofrareearthcomplexeswithβ-diketoneshavebeengeneralystudiedandac...  相似文献   
76.
A hybrid heterogeneous catalyst system, which has been synthesized by covalently anchoring oxodiperoxo molybdenum chelate complexes onto the surface of mesoporous MCM-41, is highly active and truly heterogeneous for the liquid-phase epoxidation of cyclooctene with tBuOOH as the oxygen source.  相似文献   
77.
With the aid of matrix theory and computer a series of data can be obtained such as the total number of localities in which r species of graptolites appears, the common number of localities in which both i and j species of graptolites appear, the total number of species of graptolites in one locality, the common number of species of graptolites found in both i and j localities, the total number of zones in which r species of graptolites appears, the common number of zones in which both i and j species appear, the total number of species of graptolites found in one zone, the common number of species of graptolites found in both i and j zones. Based on these data a common problem in biostratigraphy may be solved, that is, in the absence of the zonal graptolite which species of graptolites can be chosen to replace the zonal graptolite, or how to detect the zonal graptolite of a graptolite biozone. The result of matrix treatment not only detects the graptolite biozone but is useful to infer the paleo-biogeo  相似文献   
78.
Polymer-supported phosphine ligand 3b derived from ferrocene was prepared,and applied in palladium-catalyzed Suzuki- Miyaura reactions.A range of aryl bromides can couple with phenylboronic acid to obtain corresponding biaryls in excellent yields. The recycling of the polymer-bound catalyst was tested without adding palladium.  相似文献   
79.
贾铮 《化学通报》2005,68(2):106-110,134
组合电化学是一种新的电化学研究策略,通过设计和构建大量多样性的电极阵列,并对其进行高通量筛选和表征,快速、高效地实现了体系的电化学研究。本文综述了近年来进行的组合电化学研究,重点介绍了组合光学筛选方法、组合电化学合成方法以及电化学平行筛选方法,并探讨了各种方法的优势和存在的问题。  相似文献   
80.
四君子汤和四物汤微量元素含量研究   总被引:1,自引:0,他引:1  
通过了解中药“四君子汤”和“四物汤”中微量元素含量的异同,研讨了微量元素和中医“气血”理论之间的关系。实验表明,“四君子汤”和“四物汤”在微量元素的含量方面,有一定的类同和差异。该现象同中医的“气血”理论有非常相像的地方。同时发现中药中的微量元素在煎煮过程中,并不是同想象的一样匀速进入药液,而是不同的元素在不同的时间段不同的批次进入药液,这也提示中药煎法理论有一定依据。由于目前做的实验还少,本实验留下很多问题和疑点,值得进一步做有关的实验和研究。  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