全文获取类型
收费全文 | 3945篇 |
免费 | 115篇 |
国内免费 | 23篇 |
专业分类
化学 | 3280篇 |
晶体学 | 43篇 |
力学 | 46篇 |
数学 | 166篇 |
物理学 | 548篇 |
出版年
2023年 | 23篇 |
2022年 | 16篇 |
2021年 | 43篇 |
2020年 | 58篇 |
2019年 | 53篇 |
2018年 | 33篇 |
2017年 | 31篇 |
2016年 | 70篇 |
2015年 | 79篇 |
2014年 | 88篇 |
2013年 | 204篇 |
2012年 | 226篇 |
2011年 | 275篇 |
2010年 | 148篇 |
2009年 | 143篇 |
2008年 | 307篇 |
2007年 | 240篇 |
2006年 | 288篇 |
2005年 | 265篇 |
2004年 | 229篇 |
2003年 | 202篇 |
2002年 | 192篇 |
2001年 | 59篇 |
2000年 | 69篇 |
1999年 | 48篇 |
1998年 | 34篇 |
1997年 | 40篇 |
1996年 | 41篇 |
1995年 | 39篇 |
1994年 | 31篇 |
1993年 | 34篇 |
1992年 | 34篇 |
1991年 | 29篇 |
1990年 | 29篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 31篇 |
1984年 | 33篇 |
1983年 | 13篇 |
1982年 | 28篇 |
1981年 | 29篇 |
1980年 | 30篇 |
1979年 | 18篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1975年 | 19篇 |
1974年 | 13篇 |
排序方式: 共有4083条查询结果,搜索用时 109 毫秒
31.
Okada T Komatsu K Kawamoto T Yamanaka T Kagi H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(10):2423-2427
In situ Raman spectroscopic measurements of water in the region of OH vibration were conducted up to 0.4 GPa at 23 and 52 degrees C. The frequencies of the decomposed OH stretching bands initially decreased with increasing pressure, reached a minimum at 0.15 GPa and increased up to 0.3 GPa and then decreased, which corresponds to the variations of the strength of hydrogen bonding. This variation was observed at 23 degrees C, but not at 52 degrees C, which suggests a change in pressure dependence on the hydrogen bond interaction between these two temperatures. Based on the equilibration model between hydrogen-bonded and nonhydrogen-bonded molecules, the present experimental results indicate that the pressure variation of the viscosity depends on the ratio of hydrogen-bonded molecules, rather than the strength of hydrogen bonding between molecules. 相似文献
32.
Hiroyuki Higuchi Kazuhiro Takatsu Tetsuo Otsubo Yoshiteru Sakata Soichi Misumi 《Tetrahedron letters》1982,23(6):671-672
A novel cage compound was obtained by irradiation of a quadruple-layered dithiacyclophane and showed thermally reverse reaction. 相似文献
33.
Kenichi Oyaizu Junya Katoh Fumiaki Suzuki Mitsutoshi Jikei Kimihisa Yamamoto Hiroyuki Nishide Eishun Tsuchida 《先进技术聚合物》1991,2(3):155-159
Oligo(phenylene sulfide) (OPS) containing one disulfide bond at the end of the chain, which was obtained by the oxidative polymerization of diphenyl disulfide, had a relatively low Td10%(temperature for 10% weight loss) of 412 °C because of degradation of the disulfide bond. But this thermal cleavage of the disulfide bond promoted the curing reaction through thiophenoxy radical formation. OPS was allowed to react with diiodobenzene at 220 °C. The thermal stability of OPS was improved through the consumption of the disulfide bond and the coupling of the chain. 相似文献
34.
Yamamoto A Akiba N Kodama S Matsunaga A Kato K Nakazawa H 《Journal of chromatography. A》2001,928(2):139-144
A multi-beam circular dichroism (CD) detector which is easily constructed by inserting inexpensive optics into a conventional photo-diode array detector has an advantage of simultaneous detection of the absorbance and CD. The enantiomeric purity determination of malic acid in beverages was performed by this detection system. Malic acid when complexed with Cu(II) was found to have an absorbance maximum at around 750 nm. The L-malic acid-Cu(II) complex showed a positive Cotton effect in its absorbance band and its anisotropy factor (delta epsilon/epsilon) was relatively large at about 1/170. This complex was retained on a reversed-phase column with the addition of racemic 2-hydroxy-3-methylbutyric acid to the mobile phase as the ligand. A plot of the relative peak areas between the CD and the absorption (delta abs/abs) versus optical purity showed good linearity with a correlation coefficient of 0.999, and the precision expressed as the relative standard deviation of the errors from the regression line was +/-2.7% (2sigma). The accuracy of the proposed method was assessed by capillary electrophoresis. Eight commercially available juice products were analyzed using this method. Five of them were thought to be adulterated with synthetic malic acid. 相似文献
35.
36.
Masafumi Unno Hiroyuki Murakami Satoshi Kagawa Hideyuki Matsumoto 《Silicon Chemistry》2007,3(3-4):195-198
Two new silanols bearing very bulky silyl groups, (i-Pr3
Si)3SiOH and (t − BuMe2Si)3SiOH were prepared by peracidoxidation of their respective silanes. The X − ray crystallographic analysis revealed that (t − BuMe2Si)3 SiOH forms a dimeric structure with hydrogen bonding, while (i − Pr3 Si)3 SiOH exists as a monomer in the crystal. The effects of the size of the substituents as well as the reactivity of these silanols
are discussed. 相似文献
37.
38.
Dehydration of zinc biladienone was catalyzed by zinc acetate, while the reverse reaction was catalyzed by triethylamine. The transformation can be performed thermally without catalyst, and the ratio of the hydrated form to the dehydrated form depended on the solvents: the dehydrated form is favored in CHCl3 and CH2Cl2, while the hydrated form is favored in hexane, pyridine, and DMF. Kinetic studies on the thermal transformation of zinc biladienone from its hydrated blue form to the dehydrated yellow-brown form were performed in toluene and THF. The rate law was half order with respect to the zinc biladienone concentration in toluene, while first order in THF, leading to a slow transformation in concentrated solution in toluene. 相似文献
39.
Kinetics of chemiluminescence reactions of 2-methyl-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one (1c, Cypridina luciferin analogue) and substituent effects of the 6-aryl group of derivatives 1 strongly suggest that the rate-determining step is a single electron transfer from an anion derived from 1 to a triplet molecular oxygen (O2) in the oxygenation process. 相似文献
40.
Pyrene-azacrown ether hybrid: cation-π interaction 总被引:1,自引:0,他引:1
A pyrene-modified lariat ether was synthesized in order to observe the cation-π interaction in solution. 相似文献