全文获取类型
收费全文 | 23522篇 |
免费 | 4393篇 |
国内免费 | 3423篇 |
专业分类
化学 | 17412篇 |
晶体学 | 370篇 |
力学 | 1636篇 |
综合类 | 226篇 |
数学 | 2525篇 |
物理学 | 9169篇 |
出版年
2024年 | 56篇 |
2023年 | 545篇 |
2022年 | 982篇 |
2021年 | 874篇 |
2020年 | 1096篇 |
2019年 | 992篇 |
2018年 | 850篇 |
2017年 | 746篇 |
2016年 | 1110篇 |
2015年 | 1137篇 |
2014年 | 1334篇 |
2013年 | 1648篇 |
2012年 | 2150篇 |
2011年 | 2181篇 |
2010年 | 1440篇 |
2009年 | 1375篇 |
2008年 | 1589篇 |
2007年 | 1391篇 |
2006年 | 1365篇 |
2005年 | 1143篇 |
2004年 | 870篇 |
2003年 | 739篇 |
2002年 | 738篇 |
2001年 | 615篇 |
2000年 | 527篇 |
1999年 | 567篇 |
1998年 | 400篇 |
1997年 | 368篇 |
1996年 | 421篇 |
1995年 | 351篇 |
1994年 | 324篇 |
1993年 | 241篇 |
1992年 | 228篇 |
1991年 | 180篇 |
1990年 | 163篇 |
1989年 | 130篇 |
1988年 | 119篇 |
1987年 | 76篇 |
1986年 | 71篇 |
1985年 | 53篇 |
1984年 | 40篇 |
1983年 | 39篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1973年 | 3篇 |
1957年 | 7篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Yuxin An Qian Li Jiejun Chen Xiaokang Gao Hongwei Chen Chaoni Xiao Liujiao Bian Jianbin Zheng Xinfeng Zhao Xiaohui Zheng 《Biomedical chromatography : BMC》2014,28(12):1881-1886
A new mathematical model and frontal analysis were used to characterize the binding behavior of caffeic acid to human serum albumin (HSA) based on high‐performance affinity chromatography. The experiments were carried out by injecting various mole amounts of the drug onto an immobilized HSA column. They indicated that caffeic acid has only one type of binding site to HSA on which the association constant was 2.75 × 104/m . The number of the binding site involving the interaction between caffeic acid and HSA was 69 nm . The data obtained by the frontal analysis appeared to present the same results for both the association constant and the number of binding sites. This new model based on the relationship between the mole amounts of injection and capacity factors assists understanding of drug–protein interaction. The proposed model also has the advantages of ligand saving and rapid operation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
912.
913.
Tao Jia Weilong Zhou Fenghong Li Yajun Gao Lu Wang Jianxiong Han Jingying Zhang Yue Wang 《中国科学:化学(英文版)》2015,(2):323-330
Three alcohol/water-soluble porphyrins,Zn-TPy PMe I:zinc(II)meso-tetra(N-methyl-4-pyridyl)porphyrin tetra-iodide,ZnTPy PAd Br:zinc(II)meso-tetra[1-(1-adamantylmethyl ketone)-4-pyridyl]porphyrin tetra-bromide and Mn Cl-TPy PAd Br:manganese(III)meso-tetra[1-(1-adamantylmethyl ketone)-4-pyridyl]porphyrin tetra-bromide were employed as cathode interlayers to fabricate polymer solar cells(PSCs).The PC71BM([6,6]-phenyl C71 butyric acid methyl ester)and PCDTBT(poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)])-blend films were used as active layers in polymer solar cells(PSCs).The PSCs with alcohol/water-soluble porphyrins interlayer showed obviously higher power conversion efficiency(PCE)than those without interlayers.The highest PCE,6.86%,was achieved for the device with Mn ClTPy PAd Br as an interlayer.Ultraviolet photoemission spectroscopic(UPS),carrier mobility,atomic force microscopy(AFM)and contact angle( )characterizations demonstrated that the porphyrin molecules can result in the formation of interfacial dipole layer between active layer and cathode.The interfacial dipole layer can obviously improve the open-circuit voltage(Voc)and charge extraction,and sequentially lead to the increase of PCE. 相似文献
914.
915.
The ZnO catalysts supported on Silicalite‐1 zeolites with different crystallite sizes (0.08, 0.35, 1 and 1.7 μm, respectively) and 5% Zn were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, SEM, TEM‐EDX, DRIFT spectra and NH3‐TPD, and their catalytic performance in isobutane dehydrogenation assisted by CO2 was investigated. The catalytic activity is strongly dependent on the crystallite size of Silicalite‐1 support. The ZnO/S‐1‐0.35 catalyst with ca. 0.35 μm crystallite size displays the highest activity, affording an initial isobutane conversion of 51.0% and 74.5% isobutene selectivity. This can be attributed to a higher amount of acid sites present on this catalyst as well as the largest amount of nest silanols possessed by the S‐1‐0.35 support. 相似文献
916.
917.
918.
Alexander M. Schneider Luyao Lu Eric F. Manley Tianyue Zheng Valerii Sharapov Tao Xu Tobin J. Marks Lin X. Chen Luping Yu 《Chemical science》2015,6(8):4860-4866
We report the properties of a new series of wide band gap photovoltaic polymers based on the N-alkyl 2-pyridone dithiophene (PDT) unit. These polymers are effective bulk heterojunction solar cell materials when blended with phenyl-C71-butyric acid methyl ester (PC71BM). They achieve power conversion efficiencies (up to 5.33%) high for polymers having such large bandgaps, ca. 2.0 eV (optical) and 2.5 eV (electrochemical). Grazing incidence wide-angle X-ray scattering (GIWAXS) reveals strong correlations between π–π stacking distance and regularity, polymer backbone planarity, optical absorption maximum energy, and photovoltaic efficiency. 相似文献
919.
Selective O-benzoylation of hydroxamic acids is achieved by the treatment of BPO and DABCO. Aliphatic alcohols are not reactive under these conditions. Various radical or oxidation sensitive functional groups are compatible with this protocol, and no anhydrous reagents or solvents are required for the high yields of the benzoylations. 相似文献
920.
Jian Zheng Philip A. Barrett Steven J. Pontonio Neil A. Stephenson Preeti Chandra Persefoni Kechagia 《Adsorption》2014,20(1):147-156
High-rate and high-density gas separation adsorbents used in vacuum pressure swing adsorption (VPSA) processes are described. Agglomerated zeolite Li–LSX compositions made using colloidal silica binding agents and having improved nitrogen pore diffusivity compared to like compositions prepared with traditional clay binders, are also described. Preparation methods for the colloidal silica-bound adsorbents are described together with their characterization by mercury (Hg) porosimetry, scanning electron microscopy (SEM) and low dead-volume breakthrough testing, from which the pore diffusivity is obtained. In this article, we show how the location and dispersion of the colloidal silica binding agent within the agglomerated zeolite particle yields pore-architectures that resemble “state-of-the-art” binderless adsorbents. In addition, we use VPSA process simulations to show that the best process performance is achieved by the combination of high-rate and high-density adsorbent properties. 相似文献