全文获取类型
收费全文 | 4347篇 |
免费 | 337篇 |
国内免费 | 249篇 |
专业分类
化学 | 2921篇 |
晶体学 | 70篇 |
力学 | 150篇 |
综合类 | 39篇 |
数学 | 747篇 |
物理学 | 1006篇 |
出版年
2023年 | 33篇 |
2022年 | 58篇 |
2021年 | 108篇 |
2020年 | 128篇 |
2019年 | 153篇 |
2018年 | 164篇 |
2017年 | 144篇 |
2016年 | 212篇 |
2015年 | 166篇 |
2014年 | 230篇 |
2013年 | 431篇 |
2012年 | 270篇 |
2011年 | 271篇 |
2010年 | 224篇 |
2009年 | 200篇 |
2008年 | 272篇 |
2007年 | 232篇 |
2006年 | 175篇 |
2005年 | 147篇 |
2004年 | 162篇 |
2003年 | 159篇 |
2002年 | 185篇 |
2001年 | 160篇 |
2000年 | 111篇 |
1999年 | 79篇 |
1998年 | 38篇 |
1997年 | 37篇 |
1996年 | 30篇 |
1995年 | 27篇 |
1994年 | 29篇 |
1993年 | 20篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 11篇 |
1972年 | 6篇 |
排序方式: 共有4933条查询结果,搜索用时 484 毫秒
31.
M. Alves Da Silva M. Helena Gil A. P. Piedade J. S. Redinha A. M. Oliveira Brett J. M. Caridade Costa 《Journal of polymer science. Part A, Polymer chemistry》1991,29(2):269-274
The immobilization of catalase on grafted membranes of poly(ethylene)-g-co-acrylic acid and poly(tetrafluoroethylene)-g-co-acrylic acid and their application in hydrogen peroxide electrochemical sensors is described. The introduction of carboxylic acid groups onto a hydrophobic support provides a good environment for subsequent enzyme immobilization. This single membrane, hydrogen peroxide sensor showed significant improvement with respect to the double membrane versions. The response is very rapid, the linear range being from 10 μM up to 6 mM, with a detection limit of 4.7 μM, and a lifetime of more than 4 months. 相似文献
32.
采用从头计算方法,计算了反式和顺式聚乙炔的氢原子在垂直于聚乙炔分子面方向振动的红外光谱,计算表明,Gibson等用红外吸收实验所测得的谱线的确是聚乙炔的CH面外振动产生的谱线,经100℃长时间加热后,顺式聚乙炔变为反式聚炔,但波数为740cm^-1的谱级仍保留5%的强度。 相似文献
33.
通过考虑同类核子相干对间的四极相互作用,在IBM2中对Ce偶-偶同位素^128Ce-^138Ce的低激发态能谱和E2跃迁几率及分支比进行了理论分析,计算结果有效地改善了IBM中这些核的γ带能谱的Staggering现象描述,与实验观察到的低激发态结果基本一致。 相似文献
34.
DaXinSHI YaQingFENG ShunHeZHONG 《中国化学快报》2005,16(5):685-687
Photoinduced synthesis of CO2 and CH4 was investigated using a batch reaction system on several photoactive materials supported on silicon dioxide. Single semiconductor showed higher selectivity to C1 compounds. The production of C2-C3 oxygenates took place preferentially on composite semiconductor photocatalysts. In particular, it was found that acetone was the primary product over Cu/CdS-TiO2/SiO2. 相似文献
35.
Triterpenoid Constituents of Huperzia miyoshiana 总被引:1,自引:0,他引:1
Thirteen triterpenoids, including three new ones, miyoshianois A (1), B (2) and C (3), were isolated from Huperzia miyoshiana. The structures of these new compounds were established as 3-O-dihydroferuloyltohogenol (1), 16-oxo-3β,21β-dihydrox-y-serrat-14-en-24-ferulate (2) and 16-oxo-3a, 21β-dihydroxy-serrat-14-en-24-ferulate (3), respectively, on the basis of their spectroscopic analysis. 相似文献
36.
37.
A. Paesano Jr. S. C. Zanatta S. N. De Medeiros L. F. CÓtica J. B. M. Da Cunha 《Hyperfine Interactions》2005,161(1-4):211-220
We have investigated the mechanosynthesis of gadolinium and yttrium iron garnets by high-energy ball-milling of α-Fe2O3 and Gd2O3 or α-Fe2O3 and Y2O3, respectively, followed by short thermal annealings conducted at moderate temperatures. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy, in order to determine the influence of the milling time and annealing conditions on the final products. For as-milled samples of each rare-earth system, the results revealed the formation of perovskite phases, in relative amounts that depend on the milling time. The formation of garnet phases was observed in as-annealed samples treated at 1000°C for 2 h or 1100°C for 3 h, i.e., at very modest annealing requirements when compared with ordinary solid-state-reaction processes performed without previous high-energy milling. Also, the occurrence was verified of a milling time for which the relative amount of garnet phases formed by annealing was maximized. This time depends on the rare-earth composing the garnet phase and on the annealing temperature. 相似文献
38.
The collapse of a charged and radiating ball in the diffusion limit is studied using a method reported by Herrera and collaborators. The interior solution is matched with the exterior Reissner-Nordström-Vaidya metric to obtain a system of differential equations at the surface of the distribution, which can be integrated numerically for some set of initial data. For one model, the profiles of the physical variables are obtained at any piece of the material in terms of Schwarzschild-like coordinates. 相似文献
39.
40.
KMnO4引发魔芋粉-丙烯腈的接枝共聚反应 总被引:6,自引:0,他引:6
以KMnO4为引发剂进行魔芋粉与丙烯腈的接枝共聚反应。研究了魔芋粉预氧化时间、引发剂浓度、单体浓度、酸度、反应时间、反应温度和反应物加料方式等聚合条件对接枝效率的影响,并对接枝机理作了探讨。 相似文献