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   10221篇
  免费   2063篇
  国内免费   1696篇
化学   7731篇
晶体学   160篇
力学   579篇
综合类   235篇
数学   1104篇
物理学   4171篇
  2024年   24篇
  2023年   200篇
  2022年   291篇
  2021年   383篇
  2020年   461篇
  2019年   504篇
  2018年   420篇
  2017年   411篇
  2016年   540篇
  2015年   553篇
  2014年   664篇
  2013年   796篇
  2012年   958篇
  2011年   952篇
  2010年   714篇
  2009年   647篇
  2008年   756篇
  2007年   705篇
  2006年   580篇
  2005年   471篇
  2004年   355篇
  2003年   346篇
  2002年   393篇
  2001年   357篇
  2000年   265篇
  1999年   250篇
  1998年   160篇
  1997年   117篇
  1996年   97篇
  1995年   83篇
  1994年   76篇
  1993年   75篇
  1992年   71篇
  1991年   65篇
  1990年   53篇
  1989年   45篇
  1988年   34篇
  1987年   27篇
  1986年   20篇
  1985年   16篇
  1984年   10篇
  1983年   9篇
  1982年   8篇
  1981年   2篇
  1980年   2篇
  1968年   2篇
  1964年   1篇
  1961年   3篇
  1959年   3篇
  1936年   1篇
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
951.
This paper is joint with [27]. The authors prove in this article the existence and reveal its structure of uniform attractor for a two-dimensional nonautonomous incompressible non-Newtonian fluid with a new class of external forces.  相似文献   
952.
953.
研究了 5- ( 5-氯 - 2 -吡啶偶氮 ) - 2 .4-二氨基甲苯 ( 5- Cl- PADAT)与钌 ( )的显色反应。在 p H4.0~ 6.5HAc- Na Ac缓冲溶液中 ,在加热的条件下 ,5- Cl-PADAT与 Ru( )形成稳定的配合物 ,加入无机酸 ( HCl,HCl O4 ,H2 SO4 ,H3 PO4 )酸化后 ,其最大吸收波长位于 50 5nm处 ,表观摩尔吸光系数为 8.5×1 0 4 L· mol-1· cm-1,钌浓度在 0~ 6μg/ 1 0 m L范围内服从比耳定律 ,Ru( )与 5- Cl- PADAT配合物的摩尔比为 1∶ 2。以 EDTA为掩蔽剂 ,方法具有良好的选择性 ,已应用于合成样中钌的测定。  相似文献   
954.
Various cycloalkanes and straight‐chain alkanes were efficiently brominated with an aqueous HBr‐H2O2 system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo‐cycloalkanes in moderate yields and the straight‐chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for C? H activation through bromination.  相似文献   
955.
In this paper, we report a method for recognizing human ovarian tumor(HOT) cells using fluorescent biological label based on core-shell nanoparticles. The luminescent nanoparticles were synthesized with a water-in-oil(W/O)micromulsion technique. The fluorescent silica core-shell nanoparticles modified with anti-HER2 antibody using bifunctional cross-linker glutaraldedhyde targeted the corresponding tumor antigen in the cell surface of the SKOV3 ovarian cancer cells. The specific immunoreactivity of antibody-nanoparticles with cells was characterized by laser scanning microscopy (LSM) and scanning electron microscope (SEM). The results showed that the method offered potential advantages of sensitivity and simplicity due to high binding efficiency between nanoparticles and cells and provided an alternative method for the detection of HOT.  相似文献   
956.
957.
It has been known that the propagation rate coefficient (kp) will change with monomer conversion, Friss, Hamielec et al.1-5 have proposed many formulas about kp to fit this change. In order to obtain the relation between Arrhenius parameters and monomer conversion, a group of kp values at the same monomer conversion must be measured. We adopted a new method through analysis of kp values measured by usual experimental techniques for this purpose. Firstly, we chose a value of monomer convers…  相似文献   
958.
Theseparationofopticalisomersisarapidlygrowingareaincapillaryelectrophoresis(CE),andmostchiralseparationbyCEhavebeenperformedinaqueousbackgroundelectrolyte.Organicsolventssuchasmethanolandacetonitrilehavebeenappliedasbuffermodifiersatconcentrationtypicallynothigherthan40%inordertoincreasehydrophobicanalytesolubilityandtoimproveselectivity,resolution,ortoaltertheelectroosmoticflow(EOF)andelectrophoreticmobilityofanalyte.Buttherehavebeenonlyafewreportsonthechiralseparationusingpurenonaqueousme…  相似文献   
959.
The methanolysis of 2‐(2‐aryl ethynyl)benzonitriles is accelerated when the polar aprotic solvents are added, which could enhance the 6‐endo pathway and give isoquinolones, though the 5‐exo pathway is occupied mostly. The yields of products would also be in creased.  相似文献   
960.
With the wide application of rare earth fertilizer and medicines1, more and more rare earths enter into environment, and also into human body via food chain. Now it is very urgent to study the biological effect of rare earths on human health and environment. After entering into human body by whatever route, lanthanide ions are transported to secondary deposition sites mainly via the plasma in the blood stream. So it is very important to study lanthanides speciation in human blood plasma. Becau…  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