全文获取类型
收费全文 | 4118篇 |
免费 | 802篇 |
国内免费 | 487篇 |
专业分类
化学 | 1931篇 |
晶体学 | 53篇 |
力学 | 581篇 |
综合类 | 121篇 |
数学 | 332篇 |
物理学 | 2389篇 |
出版年
2024年 | 14篇 |
2023年 | 36篇 |
2022年 | 138篇 |
2021年 | 175篇 |
2020年 | 167篇 |
2019年 | 108篇 |
2018年 | 127篇 |
2017年 | 158篇 |
2016年 | 183篇 |
2015年 | 146篇 |
2014年 | 250篇 |
2013年 | 326篇 |
2012年 | 248篇 |
2011年 | 262篇 |
2010年 | 205篇 |
2009年 | 252篇 |
2008年 | 253篇 |
2007年 | 240篇 |
2006年 | 224篇 |
2005年 | 210篇 |
2004年 | 211篇 |
2003年 | 198篇 |
2002年 | 179篇 |
2001年 | 145篇 |
2000年 | 118篇 |
1999年 | 128篇 |
1998年 | 89篇 |
1997年 | 85篇 |
1996年 | 70篇 |
1995年 | 63篇 |
1994年 | 62篇 |
1993年 | 37篇 |
1992年 | 58篇 |
1991年 | 27篇 |
1990年 | 38篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1972年 | 2篇 |
排序方式: 共有5407条查询结果,搜索用时 31 毫秒
31.
Complexes of adenine, AdH, with cobalt, nickel and copper chlorides were prepared and their thermodynamic functions were determined.
The complexing processes are endothermic in nature. The thermal behaviour of complexes was followed up by using TG and DTA
analyses. The stoichiometry of thermal decomposition of the investigated complexes was suggested.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
32.
33.
34.
Lakshmi N. Roy Rabindra N. Roy Cole E. Denton Sean R. LeNoue Chandra N. Roy Shahaf Ashkenazi Thomas B. Williams Daniel R. Church Michael S. Fuge Kartik N. Sreepada 《Journal of solution chemistry》2006,35(4):605-624
The values of the second dissociation constant, K
2, and related thermodynamic quantities of the ampholyte bis[(2-hydroxyethyl)amino]acetic acid (BICINE) have been determined at temperatures from 5 to 55 ∘C. The pH values of six equimolal buffer solutions, and four buffer solutions having ionic strengths (I = 0.16 mol⋅kg−1) similar to those in blood plasma, have been evaluated at 12 temperatures from 5 to 55 ∘C using the Bates–Guggenheim convention. The liquid junction potentials (E
j
) between the buffer solutions of BICINE and saturated KCl solution of the calomel electrode at 25 and 37 ∘C have been estimated by measurement with a flowing junction cell. These values of E
j
have been used to ascertain the operational pH values at 25 and 37 ∘C. The pK
2 values at 25 and 37 ∘C are 8.333 and 8.156, respectively. The thermodynamic quantities associated with the second acid dissociation have been calculated from the values of pK
2 as a function of temperature. The zwitterionic buffer BICINE was shown to be useful as a pH standard in the region close to that of blood serum. 相似文献
35.
36.
Perfluorocarboxylic thioesters RFC(O)SR (RF=CF3(CF2)j, R=CH3(CH2)i, i andj=0–5) were studied for the first time by GLC on packed columns using SE-30, SKTFT-50X, and XE-60 as the stationary phase.
The values of thermodynamics functions of sorption were calculated. The correlations between these functions and the molecular
structures as well as the conditions of analysis were established. The insertion of the S atom into the molecules of derivatives
of perfluorocarboxylic acids causes a decrease in the contribution of the orientation interaction and an increase in the dispersion
interaction of thioesters with the stationary phases compared to esters and amides of perfluorocarboxylic acids studied previously.
For Part 1, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1165–1168, June, 1997. 相似文献
37.
38.
39.
40.
Measurement of small-signal and large-signal responses of packaged laser modules at high temperature
Ning Hua Zhu Ji Min Wen Hai Peng Song Shang Jian Zhang Liang Xie 《Optical and Quantum Electronics》2006,38(15):1245-1257
In this paper, the pulsed injection method is extended to measure the chip temperature of various packaged laser modules,
such as the DFB laser modules, the FP laser modules, and the EML laser modules. An optimal injection condition is obtained
by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide
temperature range. The small-signal frequency responses and large-signal performances of packaged laser modules at different
chip temperature are measured. The adiabatic small-signal modulation characteristics of packaged LD are first extracted. In
the large-signal measurement, the effects of chip temperature, bias current and driving signal on the performances of the
laser modules are discussed. It has been found that the large-signal performances of the EML modules depend on the different
red-shift speeds of the DFB and EAM sections as chip temperature varying, and the optimal characteristics may be achieved
at higher temperature. 相似文献