全文获取类型
收费全文 | 19708篇 |
免费 | 3809篇 |
国内免费 | 2956篇 |
专业分类
化学 | 14128篇 |
晶体学 | 381篇 |
力学 | 1295篇 |
综合类 | 260篇 |
数学 | 2015篇 |
物理学 | 8394篇 |
出版年
2024年 | 89篇 |
2023年 | 421篇 |
2022年 | 765篇 |
2021年 | 820篇 |
2020年 | 1040篇 |
2019年 | 947篇 |
2018年 | 842篇 |
2017年 | 781篇 |
2016年 | 1135篇 |
2015年 | 1191篇 |
2014年 | 1346篇 |
2013年 | 1679篇 |
2012年 | 1992篇 |
2011年 | 1936篇 |
2010年 | 1397篇 |
2009年 | 1300篇 |
2008年 | 1412篇 |
2007年 | 1213篇 |
2006年 | 990篇 |
2005年 | 873篇 |
2004年 | 675篇 |
2003年 | 532篇 |
2002年 | 541篇 |
2001年 | 438篇 |
2000年 | 327篇 |
1999年 | 281篇 |
1998年 | 199篇 |
1997年 | 158篇 |
1996年 | 153篇 |
1995年 | 105篇 |
1994年 | 119篇 |
1993年 | 90篇 |
1992年 | 96篇 |
1991年 | 76篇 |
1990年 | 83篇 |
1989年 | 57篇 |
1988年 | 47篇 |
1987年 | 29篇 |
1986年 | 34篇 |
1985年 | 40篇 |
1984年 | 34篇 |
1983年 | 34篇 |
1982年 | 23篇 |
1981年 | 24篇 |
1980年 | 13篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1974年 | 13篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Aromatization of methane over different Mo-supported catalysts in the absence of oxygen 总被引:2,自引:0,他引:2
Tan Pinglian Xu Zhusheng Zhang Tao Chen Liayuan Lin Liwu 《Reaction Kinetics and Catalysis Letters》1997,61(2):391-396
Both acidity and structure of the support are important factors in converting methane to aromatics. Lower SiO2/Al2O3 ratio seems to favor the aromatization of methane over the Mo/HZSM-5 catalyst. When Pt is added as a modifier the activity
of Mo/HZSM-5 catalyst will decrease slightly, but coke formation will enhanced. 相似文献
82.
The growth of cobalt hexacyanoferrate (CoHCF) films on bare and Au-colloid-modified electrodes in nitrate or sulfate solutions was monitored by electrochemical quartz crystal microbalance. The average efficiency of CoHCF film growth for Au colloid modified electrodes is 23 and 12 ng cm(-2) s(-1) in KNO3 and K2SO4 solutions, respectively, while those values for the bare gold electrode are 15 and 9 ng cm(-2) s(-1), respectively. In K2SO4 solution, the apparent molar masses for the Au-colloid-modified electrode at lower and higher potential is 58.4 and 37.3 g mol(-1), respectively, which is larger than those for the bare gold electrode (51.7 and 26.3 g mol(-1), respectively). The respective results were also obtained in KNO3 solution. Furthermore, the difference of the apparent molar masses at lower and higher potential for Au-colloid-modified electrodes is smaller than that for bare gold electrodes in the same electrolyte. Additionally, the mechanism of charge propagation is dependent on different anions in electrolyte solutions at higher potentials where the second redox reaction of CoHCF occurs. Therefore, the existence of Au colloids can accelerate CoHCF film growth and weaken the effect of anions on mass transport. 相似文献
83.
应用核磁共振和电子自旋共振技术研究了铜锌超氧化物歧化酶(CuZnSOD)的金属重组酶与水溶液中游离组氨酸(His)的相互作用。发现在水溶液中CuZnSOD的金属重组酶活性中心的金属可与加入的His发生作用而被部分地诱导出来,与His形成络合物。 相似文献
84.
A novel route for waste water treatment: photo-assisted Fenton degradation of dye pollutants accumulated in natural polyelectrolyte microshells 总被引:2,自引:0,他引:2
The efficient accumulation of dyes in constructed natural polyelectrolyte microshells under moderate conditions, combined with the photo-assisted Fenton reagent, opens a new route for the effective elimination of dye pollutants from waste water. 相似文献
85.
86.
We have developed a coarse-grained multiscale molecular simulation method for soft matter systems that directly incorporates stereochemical information. We divide the material into disjoint groups of atoms or particles that move as separate rigid bodies; we call these groups "rigid blobs," hence the name coarse-grained rigid blob model. The method is enabled by the construction of transferable interblob potentials that approximate the net intermolecular interactions, as obtained from ab initio electronic structure calculations, other all-atom empirical potentials, experimental data, or any combination of the above. We utilize a multipolar expansion to obtain the interblob potential-energy functions. The series, which contains controllable approximations that allow us to estimate the errors, approaches the original intermolecular potential as the number of terms increases. Using a novel numerical algorithm, we can calculate the interblob potentials very efficiently in terms of a few interaction moment tensors. This reduces the labor well beyond what is required in standard molecular-dynamics calculations and allows large-scale simulations for temporal scales commensurate with characteristic times of nano- and mesoscale systems. A detailed derivation of the formulas is presented, followed by illustrative applications to several systems showing that the method can effectively capture realistic microscopic details and can easily extend to large-scale simulations. 相似文献
87.
用峰鉴别技术反相高效液相色谱法测定火锅汤料中微量吗啡 总被引:3,自引:0,他引:3
本文报道了以峰鉴别技术为定性依据的测定火锅汤料中微量吗啡的反相高效液相色谱法。本法采用改良的Stas-otto法分离提取复杂样品中的微量吗啡。由于采用峰鉴别技术,增加了定性参数,大大提高了定性方法的准确性。本法简便、快速。最低检出浓度为0.04mg/L。在数十例样品分析中,与其它仪器分析结果比照,非常符合。 相似文献
88.
GuoXiangCHENG GuangLingPEI LingGangZENG LiYongZHANG ChaoLIU 《中国化学快报》2004,15(2):242-245
In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788),the mixture of Span 85 and xylene or the mixture of Span 85 and paraffin as monomer,cross-linking agent, dispersion stabilizer and templates, respectively. The results indicate that there are dense cavities on the surface of beads, and the diameter and density of cavity are related with the composition and amount of emulsion template. The forming mechanism of cavity from thermodynamics and dynamics was proposed. 相似文献
89.
The ESR signals of bilirubin-IXα were studied including the samples treated with free radical generating and inhibiting systems, i.e.X-X0., Fe/EDTA, SOD, mannitol/ascorbate, DTPA, KCN et al.These stable signals all comprise those originated from a semiquinone radical(g=2.0012)and superoxide radical(g11=2.041, g⊥=2.0040).The latter is shown to be bound with metal ionsespecially iron, chelated by bilirubin.The iron probably comes from bilirubin precursor---hemootobin.Active oxygen free radical scavengers may destroy these radicals.Kinetic curves of regeneration of the bilirubin radicals have been determined.Bilirubin is discussed as"active oxygen trap"in mammatians. 相似文献
90.
InteractionbetweenMetalinMetalloEnzymeandSmallBiologicalMolecules¥HuJie-Han;ShuZan-Yong;TaoLi-Mei;ChengGuo-Bao(DalianInstitut... 相似文献