全文获取类型
收费全文 | 2219篇 |
免费 | 231篇 |
国内免费 | 1143篇 |
专业分类
化学 | 2815篇 |
晶体学 | 4篇 |
力学 | 47篇 |
综合类 | 75篇 |
数学 | 9篇 |
物理学 | 643篇 |
出版年
2024年 | 7篇 |
2023年 | 56篇 |
2022年 | 57篇 |
2021年 | 71篇 |
2020年 | 54篇 |
2019年 | 59篇 |
2018年 | 58篇 |
2017年 | 81篇 |
2016年 | 72篇 |
2015年 | 69篇 |
2014年 | 134篇 |
2013年 | 119篇 |
2012年 | 119篇 |
2011年 | 135篇 |
2010年 | 115篇 |
2009年 | 140篇 |
2008年 | 154篇 |
2007年 | 155篇 |
2006年 | 142篇 |
2005年 | 163篇 |
2004年 | 149篇 |
2003年 | 135篇 |
2002年 | 134篇 |
2001年 | 118篇 |
2000年 | 75篇 |
1999年 | 84篇 |
1998年 | 93篇 |
1997年 | 100篇 |
1996年 | 86篇 |
1995年 | 111篇 |
1994年 | 102篇 |
1993年 | 83篇 |
1992年 | 86篇 |
1991年 | 75篇 |
1990年 | 70篇 |
1989年 | 74篇 |
1988年 | 19篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 3篇 |
排序方式: 共有3593条查询结果,搜索用时 328 毫秒
2.
离子交换富集-导数火焰原子吸收法测定自来水中Cu,Fe和Zn 总被引:7,自引:0,他引:7
本文研究了用 2 0 1× 7阳离子交换树脂对自来水中的微量元素进行交换富集 ,采用微量脉冲进样 导数火焰原子吸收法测定富集后溶液中的Cu ,Fe和Zn ,该方法灵敏度分别为 0 2 9,0 5 9和 0 0 6 μg·L- 1 ,精密度分别为 4 2 8% ,1 95 %和 2 2 8% ,检测限分别为 1 2 8,5 85和 0 6 8μg·L- 1 ,回收率分别为 91 13% ,10 1 34%和99 84 % ,本方法大大减少了需样量 ,简便快速 ,灵敏度高。 相似文献
3.
Shen-shui Lü 《高分子科学》2006,(5):441-447
Two kinds of water-soluble metallophthalocyanines, binuclear cobalt phthalocyanine (Co2Pc2) and binuclear ferric phthalocyanine (Fe2Pc2), were synthesized through phenylanhydride-urea route and characterized by elemental analysis and FT-IR spectra. Binuclear metallophthalocyanine derivatives (Mt2Pc2) were immobilized on silk fibers and modified viscose fibers to construct bioactive fibers of mimic enzyme. Mt2Pc2 was used as the active center of bioactive fibers, viscose and silk fibers as the microenvironments. The catalytic oxidation ability of bioactive fibers on the malodors of methanthiol and hydrogen sulfide was investigated at room temperature. The experimental results indicated that the catalytic activity of such bioactive fibers was closely correlative to the types ofbioactive fibers and substrates. 相似文献
4.
Gui Hong YAN Da XING* Shi Ci TAN Institute of Laser Life Science South China Normal University Guangzhou 《中国化学快报》2004,15(1):101-104
Electrochemiluminescence (ECL), like other chemiluminescence technique, offers high signal-to-noise ratio. Furthermore, it has the advantage over other chemiluminescence techniques of being initiated by a voltage potential. Thus, it provides a better-controlled luminescence. This technique has been used in measuring many kinds of organic and inorganic matters, and analyzing many kinds of antigen, antibody and hapten, such as carcinoembryonic antigen and alpha-fetoprotein, etc1-6. The ele… 相似文献
5.
Theoretical Calculation of Rotational Bands of ^179Pt in the Particle-Triaxial-Rotor Model 下载免费PDF全文
Theoretical calculations have been performed for nucleus ^179Pt in the particle-triaxial-rotor model with variable moment of inertia. The obtained energy spectrum agrees with the experimental data quite well. The calculated results indicate that the bands 1/2^- and 7/2^ are triaxial deformation bands and originate mainly from the v[521]1/2^- and v[633]7/2^ configurations respectively. 相似文献
6.
We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)100-xBx (x=12, 14, 16, 18,20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100 nm scale, implied by the maximum value (δM)max of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots w^- to the average crystal size D^- for the ribbons. Moreover, we find that the intrinsic coercivity jHc of the ribbons is sensitive to their crystal sizes, and the smaller D^-, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values (δФ)rms of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization σ12 kOe of the ribbons versus x. 相似文献
7.
本文研究了单取代硬脂酸二茂铁酯、双取代亚麻酸二茂铁酯、单二茂铁酸十八酯和双二茂铁酸十八酯四种二茂铁衍生物L-B膜修饰铂电极的循环伏安行为,用理论模型模拟了归一化峰面积,峰电位差随扫描速度变化的规律,以及分子相互作用能与半高宽的关系,将实验结果与理论模型的模拟结果进行比较,求得了L-B膜的层间电荷转移速度常数,L-B膜与电极之间的电荷转移速度常数,分子作用能及半峰电位等参数,并比较了四种二茂铁衍生物 相似文献
8.
钨(Ⅵ)的富集与检测方法研究进展 总被引:1,自引:0,他引:1
检测W(Ⅵ)对环境科学和生命科学研究具有积极意义。本文就1991年以来国内外W(Ⅵ)的富集手段,检测方法概况作一综述,其中包括,荧光光谱法,分光光度法,原子发射光谱法,质谱法,动力学方法,极普法,化学发光法,中子活化分析及联用技术等。 相似文献
9.
从日本冲绳采回枝管藻,用毛细管将成熟多室孢子囊挑出,在试验室条件下培养,可长成孢子体.用光学显微镜和透射电子显微镜观察发现:孢子释放后形成盘状体附着在基质上,念珠状同化丝从盘状体中间分生.同化丝可从中间部位产生分支,多室孢子囊位于部分同化丝的近端部;同化丝大量产生后基部细胞平行排列,中空,形成假薄壁组织,而后孢子体进入伸长生长阶段;在每个盘状体细胞和同化丝细胞中都有多个色素体和线粒体,蛋白核突出于色素体其他部分,类脂体存在于类囊体中;在同化丝的细胞壁上存在缺口;对同化纤毛而言,色素体和线粒体数量少,紧贴细胞膜,质壁分离严重,在细胞壁上存在“通道”. 相似文献
10.
Morphology of Platinum Nanowire Array Electrodepostied Within Anodic Aluminium Oxide Template Characterized by Atomic Force Microscopy 下载免费PDF全文
KONGLing-Bin LUMei LIMeng-Ke GUOXin-Yong LIHu-Lin 《中国物理快报》2003,20(5):763-766
Unifrom platinum nanowires were synthesized by electrodepositing the platinum under a very low altering current frequency(20Hz) and increasing voltage(5-15V)in the proes of anodic aluminium oxide(AAO) template. Atomic force microscopy observation indicates that the template membranes we obtained have hexagonally clse-packed nanochannels.The platinum nanowires have highly ordered arrays after partially dissolving the aluminium oxide membrane.With the increasing dissolvoing time,the platinum nanowire array collapsed.A concave topography of the aluminium substrate was observed after the aluminium oxide membrane was dissolved completely and the platinum nanowires were released from the template.Platinum nanowires were also characterized by transmission electron microscopy and the phase structure of the Al/AAO/Pt composite was proven by x-ray diffraction. 相似文献