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   14827篇
  免费   633篇
  国内免费   43篇
化学   10119篇
晶体学   230篇
力学   472篇
综合类   1篇
数学   1143篇
物理学   3538篇
  2024年   48篇
  2023年   166篇
  2022年   372篇
  2021年   431篇
  2020年   473篇
  2019年   531篇
  2018年   494篇
  2017年   468篇
  2016年   672篇
  2015年   482篇
  2014年   768篇
  2013年   1274篇
  2012年   1120篇
  2011年   1178篇
  2010年   778篇
  2009年   602篇
  2008年   742篇
  2007年   739篇
  2006年   580篇
  2005年   502篇
  2004年   391篇
  2003年   318篇
  2002年   264篇
  2001年   160篇
  2000年   133篇
  1999年   99篇
  1998年   73篇
  1997年   100篇
  1996年   96篇
  1995年   75篇
  1994年   71篇
  1993年   96篇
  1992年   99篇
  1991年   78篇
  1990年   71篇
  1989年   72篇
  1988年   49篇
  1987年   45篇
  1986年   42篇
  1985年   63篇
  1984年   65篇
  1983年   54篇
  1982年   49篇
  1981年   40篇
  1980年   46篇
  1979年   62篇
  1978年   49篇
  1977年   53篇
  1976年   42篇
  1975年   36篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
In the present communication, we report the studies concerning liquid–liquid–solid equilibria for the ternary system sodium thiosulphate (Na2S2O3) + ethanol + water at ambient pressure and at room temperature (303 ± 2 K). The solubility data of Na2S2O3 are reported for solutions in water, ethanol and solutions of varying concentrations of ethanol in water. The phase diagram for the said system is developed, described and compared with similar system K2CO3 + methanol + water. These results have been explained in terms of structural properties of aqueous ethanol solutions and further discussed in terms of the effect of ions to cause phase separation.  相似文献   
102.
An error has been detected (and also corrected) in Theorem 2.8 of the paper entitled “Adjoining an Order Unit to a Matrix Ordered Space” (Positivity, (2005)9: 207–223; DOI ). Accordingly, some of the results of the paper have been modified. Also, a notion of C*-matricially, Riesz normed spaces has been introduced.  相似文献   
103.
104.
According to Bell's theorem, the degree of correlation between spatially separated measurements on a quantum system is limited by certain inequalities if one assumes the condition of locality. Quantum mechanics predicts that this limit can be exceeded, making it nonlocal. We analyse the effect of an environment modelled by a fluctuating magnetic field on the quantum correlations in an EPR singlet as seen in the Bell inequality. We show that in an EPR setup, the system goes from the usual ‘violation’ of Bell's inequality to a ‘non-violation’ for times larger than a characteristic time scale which is related to the parameters of the fluctuating field. We also look at these inequalities as a function of the spatial separation between the EPR pair.  相似文献   
105.
106.
The crystal and molecular structure of 1-ethyl-4-methoxy-9H-pyrido[3,4b]indole (crenatine) carbonate C14H14N2O·H2CO3, (MS, m/z 226)M R 288.3, a-carboline alkaloid, has been determined from X-ray diffraction data. The compound crystallizes in the space group Pbca with cell parameters:a=11.616(4),b=18.450(8),c=12.992(5)Å,V=2784(2)Å3,Z=8,D calc=1.375 g cm–3, (MoK)=0.71069Å,(Mo K)=0.94 cm–1,F(000)=1216,R/R w =8.2/10.3% for 1099 reflections. The ring system of the-carboline nucleus is planar. The title compound shows a two center hydrogen bond between the indole N-H group and the oxygen atom of a carbonate group. The structure does not display hydrogen bonding between-carboline groups but rather a bonding network involving the carbonate group.  相似文献   
107.
108.
109.
Summary Complexes of nickel(II) with N-(2-carboxyphenyl)benzamide (CPBH), 2-amino-N-(2-carboxyphenyl)benzamide (ACPBH), N-isoxazolyl benzamide (IB), N-anilinobenzamide (AB), N-(2-pyridyl)-3-carboxypropanamide (PCPA) and N-(2-pyridyl)-2-carboxybenzamide (PCBA) have been isolated and characterized by elemental analyses, magnetic susceptibility measurements, thermal studies, i.r. and electronic spectral studies. The electrochemical behaviour of some complexes has also been investigated.  相似文献   
110.
Summary The oxidation of MeCHO by chromium(VI) has been studied in HClO4 medium over a wide range of experimental conditions and has been found to obey the rate law;v=k[MeCHO][HCrO 4 ][H+]. The calculated H and-S values for the reaction are 30±2kJ mol–1 and 171±7J mol–1deg–1, respectively. The mechanism is discussed in terms of carbon-hydrogen bond cleavage.  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