全文获取类型
收费全文 | 1782篇 |
免费 | 39篇 |
国内免费 | 7篇 |
专业分类
化学 | 1399篇 |
晶体学 | 29篇 |
力学 | 20篇 |
数学 | 122篇 |
物理学 | 258篇 |
出版年
2022年 | 8篇 |
2021年 | 18篇 |
2019年 | 21篇 |
2018年 | 13篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 27篇 |
2013年 | 66篇 |
2012年 | 72篇 |
2011年 | 85篇 |
2010年 | 57篇 |
2009年 | 37篇 |
2008年 | 78篇 |
2007年 | 94篇 |
2006年 | 103篇 |
2005年 | 111篇 |
2004年 | 83篇 |
2003年 | 59篇 |
2002年 | 85篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 28篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 37篇 |
1984年 | 41篇 |
1983年 | 27篇 |
1982年 | 31篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 28篇 |
1978年 | 31篇 |
1977年 | 26篇 |
1976年 | 36篇 |
1975年 | 26篇 |
1974年 | 25篇 |
1973年 | 25篇 |
1972年 | 11篇 |
1971年 | 9篇 |
排序方式: 共有1828条查询结果,搜索用时 15 毫秒
91.
92.
Kazuo Sugiyama Tadao Nakaya Minoru Imoto 《Journal of polymer science. Part A, Polymer chemistry》1972,10(1):205-215
A study of the photopolymerization of vinyl monomers in the presence of tetramethyltetrazene (TMT) was made. TMT was found to act as an effective sensitizer. In the photopolymerization of vinyl monomers such as methyl methacrylate or styrene the rate of polymerization was expressed by the equation: Rp = k[TMT]1/2[monomer]. The chain-transfer constant of TMT under ultraviolet irradiation was estimated to be 3.8 × 10?2 for the above monomers. A linear correlation was found to exist between the reactivity of dimethylamino radical toward the vinyl monomers and e values for the corresponding monomers. 相似文献
93.
Choji Kashima Shigeki Hibi Tatsuya Maruyama Kazuo Harada Yoshimori Omote 《Journal of heterocyclic chemistry》1987,24(3):637-639
The relative reaction rate of five-membered heterocycles with ozone was evaluated. These relative rates were correlated to the highest bond order value in the corresponding ring, calculated by the convenient HMO method. From this correlation, the reactivity of heterocycles with ozone was able to be predicted. Also it was concluded that the predominant product in the ozonolysis of five-membered heterocycles containing an oxygen atom was the corresponding carboxylic acid, while nitrogen heterocycles gave the corresponding amide. 相似文献
94.
Masahiko Imai Lu Gong Xu Kazuo Ametani Mituaki Tutiya 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1763-1773
Polypropylene films were irradiated with 60Co γ-rays in vacuum or in air and stored in air. Just after irradiation, the concentration of carbonyl group of the sample irradiated in air only increased with dose. The concentrations of both samples increased with storage time. The more the absorbed doses, the higher the increasing rates. The increasing rate of the concentration of carbonyl group during irradiation in air was higher than those during storage in air. Just after irradiation, the tensile strengths and the elongations of the both samples somewhat increased with dose at the doses less than 5 Mrad, but decreased at doses more than 13 Mrad. The tensile strength and the elongation of the sample irradiated in air decreased with storage time. Those of the sample irradiated in vacuum also decreased with storage time but the decreasing rates were much smaller than those in the sample irradiated in air. The gel fractions of the samples irradiated in vacuum and annealed in vacuum were somewhat higher than those irradiated in vacuum and not annealed. To elucidate high oxidation rate in the sample irradiated in air during and after irradiation, reaction mechanisms were discussed. To clarify the difference of mechanical properties between the samples irradiated in vacuum and in air, the effect of crosslink was considered, together with the oxidation. 相似文献
95.
96.
Ai Ito Takamasa Amaki Ayako Ishii Kazuo Fukuda Ryu Yamasaki Iwao Okamoto 《Tetrahedron letters》2018,59(45):3994-3998
Aromatic amides bearing 2-azulenyl group on the amide nitrogen were synthesized and their structures were investigated. The π-electron density of the N-aryl group was found to influence the cis-trans conformational preferences of these compounds in solution. X-ray crystallography revealed that the plane of the 2-azulenyl ring has a strong tendency to lie coplanar with the amide plane when the azulene group is located on the same side as the amide oxygen atom. 相似文献
97.
Speciation of arsenic in body fluids 总被引:1,自引:0,他引:1
Inorganic arsenic is metabolized by consecutive reduction and methylation reactions to dimethylated arsenic (DMA), and then excreted into the urine mostly in the form of DMA. Therefore, arsenic metabolites in the body fluids and organs/tissues are present in the form of inorganic (arsenite and arsenate) and methylated arsenics (MMA and DMA). Although pentavalent arsenics can be present mostly in the form of free ions, trivalent ones may be present more in the forms conjugated with thiol groups of glutathione (GSH) or proteins. Arsenic in the body fluids (plasma, bile and urine) is present in the soluble forms and can be speciated on ion exchange columns by HPLC with on-line detection by an inductively coupled argon plasma-mass spectrometer (ICP-MS). Free forms of arsenite, arsenate, and monomethylarsonous, monomethylarsonic, dimethylarsinous and dimethylarsinic acids in the body fluids have been demonstrated to be speciated simultaneously within 10 min or so on both anion and cation exchange columns together with arsenobetaine (AsB) and arsenocholine (AsC). Trivalent arsenics conjugated with GSH were eluted in intact forms on an anion exchange column but were liberated into free forms on a cation exchange column. Thus, free and GSH-conjugated arsenic metabolites in the bile and urine have been speciated simultaneously on ion exchange columns by HPLC-ICP-MS. 相似文献
98.
99.
100.
The synthesis and crystal structure of NiMoO4·nH2O were investigated. The hydrate crystallized in the triclinic system with space group P−1, Z=4 with unit cell parameters of a=6.7791(2) Å, b=6.8900(2) Å, c=9.2486(2) Å, α=76.681(2)°, β=83.960(2)°, γ=74.218(2)°. Its ideal chemical composition was NiMoO4·3/4H2O rather than NiMoO4·1H2O. Under hydrothermal conditions the hydrate turned directly into α-NiMoO4 above 483 K, giving nanorods thinner than the crystallites of the mother hydrate. On the other hand, it turned into Anderson type of polyoxomolybdate via a solid-solution process in a molybdate solution at room temperature. 相似文献