全文获取类型
收费全文 | 2444篇 |
免费 | 35篇 |
国内免费 | 179篇 |
专业分类
化学 | 2010篇 |
晶体学 | 15篇 |
力学 | 24篇 |
综合类 | 2篇 |
数学 | 4篇 |
物理学 | 603篇 |
出版年
2024年 | 2篇 |
2023年 | 60篇 |
2022年 | 25篇 |
2021年 | 33篇 |
2020年 | 35篇 |
2019年 | 56篇 |
2018年 | 42篇 |
2017年 | 42篇 |
2016年 | 35篇 |
2015年 | 43篇 |
2014年 | 64篇 |
2013年 | 101篇 |
2012年 | 172篇 |
2011年 | 138篇 |
2010年 | 113篇 |
2009年 | 158篇 |
2008年 | 151篇 |
2007年 | 187篇 |
2006年 | 151篇 |
2005年 | 128篇 |
2004年 | 115篇 |
2003年 | 96篇 |
2002年 | 62篇 |
2001年 | 71篇 |
2000年 | 83篇 |
1999年 | 80篇 |
1998年 | 68篇 |
1997年 | 57篇 |
1996年 | 52篇 |
1995年 | 45篇 |
1994年 | 32篇 |
1993年 | 33篇 |
1992年 | 28篇 |
1991年 | 31篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有2658条查询结果,搜索用时 15 毫秒
51.
We investigated iron and cobalt films with 20% carbon concentration with nanocrystalline structure. One of the aims of this work is to analyze the physical nature of high-speed structural self-assembling as often happens in explosive crystallization processes in these films. 相似文献
52.
Michelle J. S. Spencer Andrew Hung Ian K. Snook Irene Yarovsky 《Surface science》2003,540(2-3):420-430
The adsorption of atomic S on the Fe(1 1 0) surface is examined using density functional theory (DFT). Three different adsorption sites are considered, including the atop, hollow and bridge sites and the S is adsorbed at a quarter monolayer coverage in a p(2 × 2) arrangement. The hollow site is found to be the most stable, followed by the bridge and atop sites. At all three sites, S adsorption results in relatively minor surface reconstruction, with the most significant being that for the hollow site, with lateral displacements of 0.09 Å. Comparisons between S-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the S. At the hollow site, the presence of S causes an increase in the surface Fe d-orbital density of states between 4 and 5 eV. However, S adsorption has no significant effect on the structure and magnetic properties of the lower substrate layers. 相似文献
53.
硫氰酸铵树脂相分光光度法同时测定天然水中微量铁和钴 总被引:4,自引:0,他引:4
研究了在Tween-80存在的酸性介质中,Fe(Ⅲ)和Co(Ⅱ)与SCN^-形成稳定的有色络阴离子与阴树脂交换吸附,有色络合物富集显色于树脂组上,进行树脂组分光光度集显色于树脂相上,进行树脂相分光光度法同时测定铁和钴的实验条件,Fe(Ⅲ)和Co(Ⅱ)树脂具有色络合物最大吸收波长λmax分别为490nm和630nm,摩尔吸光系数,ε为2.4×10^5L.mol^-1.cm^-1和2.1×10^5L. 相似文献
54.
催化动力学光度法测定痕量铁 总被引:10,自引:0,他引:10
论文研究和建立了催化动力学褪色光度法测定痕量Fe(Ⅲ)的新体系,反应介质为盐酸-邻苯二甲酸氢钾(pH2.2)缓冲溶液,催化体系为痕量Fe(Ⅲ)催化过硫酸铵氧化邻甲氧基酚的自聚反应。研究了此反应体系的最佳条件、动力学参数及反应机理,考察了21种干扰离子的影响,建立了一种新型催化动力学光度法测定痕量Fe(Ⅲ)的方法。本法的线性范围0.07~1.1μg·(25mL)~(-1)。方法灵敏度远远高于普通光度法,检出限为5.4×10~(-8)g·L~(-1)。方法应用于自来水、河水、城市污水、豆奶粉和茶叶中痕量Fe(Ⅲ)的测定,相对标准偏差为0.36%~3.4%,标准加入回收率为97.3%~102.7%,结果满意。 相似文献
55.
R. Viskup B. Praher T. Stehrer J. Jasik H. Wolfmeir J.D. Pedarnig J. Heitz 《Applied Surface Science》2009,255(10):5215-5219
Time-resolved photography was employed to study plasma dynamics and particle ejection of laser-irradiated iron oxide materials. Nano-particle powder, pressed powder pellets and sintered ceramics were ablated in air and Ar gas background by means of short laser pulses (Nd:YAG laser wavelength λ = 1064 nm and pulse duration τL ≈ 6 ns; KrF laser λ = 248 nm and τL ≈ 20 ns). Plasma plume dynamics significantly depended on sample morphology. The ejection of non-luminous particles up to several hundreds of microseconds after the laser pulse was observed for powder and pressed powder target materials. Laser-induced breakdown spectroscopy (LIBS) was employed for element analysis of iron oxide powders, pressed pellets and sintered ceramics. LIBS spectra of the different targets were comparable to each other and qualitatively independent of target morphology. 相似文献
56.
A magnetic cotton/polyester fabric with photocatalytic, sonocatalytic, antibacterial and antifungal activities was successfully prepared through in-situ sonosynthesis method under ultrasound irradiation. The process involved the oxidation of Fe2+ to Fe3+ via hydroxyl radicals generated through bubbles collapse in ultrasonic bath. The treated samples were analyzed by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometry. Photocatalytic and sonocatalytic activities of magnetite treated fabrics were also evaluated toward Reactive Blue 2 decoloration under sunlight and ultrasound irradiation. Central composite design based on response surface methodology was applied to study the influence of iron precursor, pH and surfactant concentration to obtain appropriate amount for the best magnetism. Findings suggested the potential of one-pot sonochemical method to synthesize and fabricate Fe3O4 nanoparticles on cotton/polyester fabric possessing appropriate saturation magnetization, 95% antibacterial efficiency against Staphylococcus aureus and 99% antifungal effect against Candida albicans, 87% and 70% dye photocatalytic and sonocatalytic decoloration along with enhanced mechanical properties using only one iron rich precursor at low temperature. 相似文献
57.
58.
SiO2含量是铁矿石质量控制的主要技术指标,亦是衡量铁矿石品质好坏的关键指标之一,对选矿方法、配矿流程的确定具有重要意义。传统的SiO2含量测定法虽然准确度高,但工作量大,操作繁琐,花费时间长,难以快速、高效确定铁矿石中SiO2含量。采用红外光谱辐射计Turbo FT对辽宁省鞍钢集团鞍千矿业有限责任公司的“鞍山式”铁矿样品进行热红外光谱测试,分析了光谱特征,构建了比值指数(RI)、差值指数(DI)和归一化指数(NDI),并确定光谱指数与样品SiO2含量相关性最显著的敏感波段及对应的相关系数值;优选出与样品SiO2含量相关性最显著的归一化指数(NDI),构建样品SiO2含量的定量反演模型,并进行了验证。结果表明,三种光谱指数与样品SiO2含量的敏感波段均位于余辉带特征(RF)的左边界8.06与8.2 μm处,相关系数均达到0.9以上,其中NDI与样品SiO2含量的相关性最高;基于NDI构建了实验样品SiO2含量的二次函数反演模型,预测误差为3.57%。该方法相对于传统的研磨化验法,具有工作强度小、便捷、快速、高效、无污染的优点,对遥感找矿也具有一定指导意义。 相似文献
59.
60.
火焰原子吸收法测定氰化镀银液中的铜和铁 总被引:2,自引:0,他引:2
提出了用火焰原子吸收光谱法测定氰化镀银液中铜、铁含量的方法,在测定条件下,其他共存元素均无干扰。该方法的相对标准偏差为铜(1.92%-2.63%、铁3.13%-3.73%,样品加标回收率为铜96.8%-101.6%、铁97.5%-101.1%。 相似文献