全文获取类型
收费全文 | 125886篇 |
免费 | 1551篇 |
国内免费 | 454篇 |
专业分类
化学 | 69039篇 |
晶体学 | 2054篇 |
力学 | 4964篇 |
综合类 | 5篇 |
数学 | 12285篇 |
物理学 | 39544篇 |
出版年
2016年 | 1330篇 |
2015年 | 1021篇 |
2014年 | 1368篇 |
2013年 | 4903篇 |
2012年 | 3412篇 |
2011年 | 4449篇 |
2010年 | 2778篇 |
2009年 | 2556篇 |
2008年 | 3980篇 |
2007年 | 4022篇 |
2006年 | 4076篇 |
2005年 | 4000篇 |
2004年 | 3490篇 |
2003年 | 3191篇 |
2002年 | 3078篇 |
2001年 | 3596篇 |
2000年 | 2690篇 |
1999年 | 2211篇 |
1998年 | 1901篇 |
1997年 | 1886篇 |
1996年 | 1811篇 |
1995年 | 1780篇 |
1994年 | 1552篇 |
1993年 | 1543篇 |
1992年 | 1761篇 |
1991年 | 1753篇 |
1990年 | 1686篇 |
1989年 | 1691篇 |
1988年 | 1692篇 |
1987年 | 1690篇 |
1986年 | 1594篇 |
1985年 | 2144篇 |
1984年 | 2275篇 |
1983年 | 1892篇 |
1982年 | 2221篇 |
1981年 | 2037篇 |
1980年 | 2079篇 |
1979年 | 2066篇 |
1978年 | 2191篇 |
1977年 | 2096篇 |
1976年 | 2117篇 |
1975年 | 2057篇 |
1974年 | 1897篇 |
1973年 | 2105篇 |
1972年 | 1285篇 |
1971年 | 976篇 |
1970年 | 912篇 |
1969年 | 923篇 |
1968年 | 1050篇 |
1967年 | 1101篇 |
排序方式: 共有10000条查询结果,搜索用时 215 毫秒
31.
A Mechanistic Study on the Oxidative Degradation of Dibenzazepine Derivatives by Manganese(III) Complexes in Acidic Sulfate Media
下载免费PDF全文
![点击此处可从《国际化学动力学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The oxidative degradation of tricyclic antidepressants (TCA) was studied in the presence of a large excess of the oxidizing agent manganese(III) and its reduced form manganese(II) sulfate in acidic media. The products were detected and identified using UV–vis, ESI‐MS, IR, and EPR methods. The mechanism of the reaction was studied for the following two classes of TCA: 10,11‐dihydro‐5H‐dibenz[b, f]azepines and dibenz[b, f]azepines. The oxidative degradation between dibenz[b, f]azepines and the manganese(III) ions resulted in the formation of substituted acridine with the same substituent as in the origin dibenz[b, f]azepine derivative. The pseudo–first‐order rate constants (kobs) were determined for the degradation process. The dependences of the observed rate constants on the [MnIII] with a zero intercept were linear. The reaction between 10,11‐dihydro‐5H‐dibenz[b, f]azepines, and the manganese(III) sulfate ion resulted in oxidative dehydrogenation, which proceeded via the formation of the following two intermediates: a free organic radical and a dimer. Further oxidation of the second intermediate led to a positively charged radical dimer as the single final product. Linear dependences of the pseudo–first‐order rate constants (kobs) on the [MnIII] with a zero intercept were established for the degradation of 10,11‐dihydro‐5H‐dibenz[b, f]azepines. The observed rate constants were dependent on the [H+] and independent of the [TCA] within the excess concentration range of the manganese(III) complexes used in the isolation method. The radical product of the degradation of 10,11‐dihydro‐5H‐dibenz[b, f]azepines was not stable in the aqueous solution and was subsequently transformed to a nonradical dimer in the next slower step. The observed rate constants were independent of the [MnIII], independent of the [H+] and increased slightly with increasing TCA concentrations when TCA was used in excess. The mechanistic consequences of all of these results are discussed. 相似文献
32.
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13... 相似文献
33.
34.
35.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne). 相似文献
36.
37.
38.
39.
40.
W. L. Liang B. K. A. Ngoi L. E. N. Lim K. Venkatakrishnan C. W. Hee 《Optics & Laser Technology》2003,35(4):285-290
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays. 相似文献