全文获取类型
收费全文 | 18602篇 |
免费 | 2488篇 |
国内免费 | 2943篇 |
专业分类
化学 | 14710篇 |
晶体学 | 291篇 |
力学 | 790篇 |
综合类 | 285篇 |
数学 | 2044篇 |
物理学 | 5913篇 |
出版年
2024年 | 18篇 |
2023年 | 169篇 |
2022年 | 440篇 |
2021年 | 463篇 |
2020年 | 507篇 |
2019年 | 574篇 |
2018年 | 473篇 |
2017年 | 434篇 |
2016年 | 737篇 |
2015年 | 784篇 |
2014年 | 941篇 |
2013年 | 1329篇 |
2012年 | 1511篇 |
2011年 | 1581篇 |
2010年 | 1210篇 |
2009年 | 1170篇 |
2008年 | 1412篇 |
2007年 | 1320篇 |
2006年 | 1200篇 |
2005年 | 999篇 |
2004年 | 944篇 |
2003年 | 840篇 |
2002年 | 943篇 |
2001年 | 745篇 |
2000年 | 575篇 |
1999年 | 462篇 |
1998年 | 293篇 |
1997年 | 307篇 |
1996年 | 248篇 |
1995年 | 218篇 |
1994年 | 192篇 |
1993年 | 178篇 |
1992年 | 166篇 |
1991年 | 121篇 |
1990年 | 105篇 |
1989年 | 91篇 |
1988年 | 52篇 |
1987年 | 56篇 |
1986年 | 46篇 |
1985年 | 40篇 |
1984年 | 27篇 |
1983年 | 18篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Xiao‐Feng Guo Hui‐Ying Chen Xiao‐Hai Zhou Hong Wang Hua‐Shan Zhang 《Electrophoresis》2013,34(24):3287-3292
A simple and economical CE method has been developed for the analysis of four model basic proteins by employing N‐methyl‐2‐pyrrolidonium methyl sulfonate ionic liquid (IL) as the dynamic coating material based on the interaction of both between electrostatic attraction and hydrogen bond, and between the organic cations of IL and the inner surface of bare fused‐silica capillary. The N‐methyl‐2‐pyrrolidonium‐based IL modified capillary not only generated a stable suppressed electroosmotic flow, but also effectively eliminated the wall adsorption of proteins. Several important parameters such as the IL concentration, pH values, and concentrations of the background electrolyte were optimized to improve the separation of basic proteins. Consequently, under the optimum separation conditions, a satisfied separation of basic proteins including lysozyme, cytochrome c, ribonuclease A, and α‐chymotrypsinogen A with theoretical plates ranging from 2.09 × 105 to 4.48 × 105 plates/m had been accomplished within 15 min. The proposed method first illustrated the effect of hydrogen bond between coating material and inner capillary surface on the coating, which should be a new strategy to design and select more effective coating materials to form more stable coatings in CE. 相似文献
992.
Heqing Fu Hong Huang Qi Wang Hui Zhang Huanqin Chen 《Journal of Dispersion Science and Technology》2013,34(5):634-638
The aqueous polyurethane hybrid dispersion modified by the epoxy resin were synthesized using 1,4-butanediol ( BDO ) and dimethylolpropionic(DMPA) as chain extenders. A kind of automobile interior decoration adhesive was made by the modified hybrid dispersions. Effects of the content and the kinds of epoxide resin on the properties of dispersions and dispersion-cast films such as appearance, pot life, viscosity, particle size, molecular mass, hardness, swelling in water, contact angle, strength of stress, elongation at break, and other mechanical properties were studied. At the same time the effect of the E20 content on the peel strength of the adhesive for several automobile interior decoration substrates such as rubber/wood, poly(vinyl chloride)/wood; leather/wood, sponge/wood was investigated. The experimental results show that when the epoxy resin E20 content was 8%, the modified polyurethane hybrid dispersions possess better properties and the adhesive made by the modified dispersions posses better adhesion for automobile interior decoration substrates. The stress-strain curve of the modified aqueous polyurethane hybrid dispersions films shows the modified aqueous cast films possess better rigidity and toughness. 相似文献
993.
Direct Blue 71 staining as a destaining‐free alternative loading control method for Western blotting
Li Zeng Jing Guo Hong‐Bo Xu Rongzhong Huang Weihua Shao Liu Yang Mingju Wang Jianjun Chen Peng Xie 《Electrophoresis》2013,34(15):2234-2239
In Western blotting, a suitable loading control is indispensable for correcting errors in the total amount of loaded protein. Immunodetection of housekeeping proteins and total protein staining have traditionally been used as loading control methods. Direct Blue 71 (DB71) staining—a novel, sensitive, dye‐binding staining method compatible with immunodetection—may offer advantages over these traditional loading control methods. Three common neuroscientific samples (human plasma, human oligodendrocytes, and rat brain) were employed to assess DB71 staining as a loading control method for Western blotting. DB71, CBB, one traditional housekeeping protein, and one protein of interest were comparatively assessed for reliability and repeatability and linear dynamic range over 2.5–40 μg of protein loaded. DB71's effect on the reliability and repeatability and linear dynamic range of immunoreaction were also assessed. Across all three sample types, DB71 was either equivalent or superior to CBB and housekeeping protein‐based methods in terms of reliability and repeatability and linear dynamic range. Across all three sample types, DB71 staining did not impair the reliability and repeatability or linear dynamic range of immunoreaction. Our results demonstrate that the DB71 staining can be used as a destaining‐free alternative loading control method for Western blotting. 相似文献
994.
Guo‐Ying Hong Zhong‐Xin Zhu Yuan‐Meng Duan Xuan Zhou Li‐Tai Jin 《Electrophoresis》2013,34(22-23):3171-3179
As a noncovalent fluorescence probe, in this study, salicylaldehyde azine (SA) was introduced as a sensitive fluorescence‐based dye for detecting proteins both in 1D and 2D polyacrylamide electrophoresis gels. Down to 0.2 ng of single protein band could be detected within 1 h, which is similar to that of glutaraldehyde‐silver stain, but approximately four times higher than that of SYPRO Ruby fluorescent stain. Furthermore, comparative analysis of the MS compatibility of SA stain with SYPRO Ruby stain indicated that SA stain is compatible with the downstream of protein identification by LC‐MS/MS. Additionally, the probable mechanism of the SA stain was investigated by molecular docking. The results demonstrated that the interaction between SA and protein was mainly contributed by hydrogen bonding and hydrophobic forces. 相似文献
995.
Dong‐Jun Yu Jun Hu Yan Huang Hong‐Bin Shen Yong Qi Zhen‐Min Tang Jing‐Yu Yang 《Journal of computational chemistry》2013,34(11):974-985
Understanding the interactions between proteins and ligands is critical for protein function annotations and drug discovery. We report a new sequence‐based template‐free predictor (TargetATPsite) to identify the Adenosine‐5′‐triphosphate (ATP) binding sites with machine‐learning approaches. Two steps are implemented in TargetATPsite: binding residues and pockets predictions, respectively. To predict the binding residues, a novel image sparse representation technique is proposed to encode residue evolution information treated as the input features. An ensemble classifier constructed based on support vector machines (SVM) from multiple random under‐samplings is used as the prediction model, which is effective for dealing with imbalance phenomenon between the positive and negative training samples. Compared with the existing ATP‐specific sequence‐based predictors, TargetATPsite is featured by the second step of possessing the capability of further identifying the binding pockets from the predicted binding residues through a spatial clustering algorithm. Experimental results on three benchmark datasets demonstrate the efficacy of TargetATPsite. © 2013 Wiley Periodicals, Inc. 相似文献
996.
Yongbing Pei Yuling Jiang Hong Huang Huanqin Chen 《Journal of Dispersion Science and Technology》2013,34(9):1279-1284
The acrylate redispersible polymer powder (RPP) was produced from acrylate latex via spray drying, which was synthesized by latex polymerization with the configuration of soft core and hard shell. The powder's redispersibility and stability of its reconstituted latex were achieved through incorporating monomer methacrylic acid (MAA), which has functional carboxyl group and can provide an ionization effect in alkaline range. The influence of pH value and MAA amount on the redispersibility and stability were studied. The stabilization mechanism for reconstituted latex was also investigated. The acrylate RPP has good redispersibility at MAA of 4–5% and pH values between 9.0 and 10.0. The reconstituted latex is stable at these conditions due to high zeta potential and strong electrostatic repulsion force. 相似文献
997.
Fangting Chi Xiaolin Wang Jie Xiong Sheng Hu 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(3):1331-1340
PVA functionalized with vinylphosphonic acid was prepared as a new adsorbent for uranyl (VI) adsorption from aqueous solutions. The vinylphosphonic acid was cografted onto PVA fibers by preirradiation grafting technique. The adsorbent were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorbent was observed to possess a fibrous structure and was bonded with phosphonic acid groups successfully. The adsorbent was used for the adsorption of low levels uranyl (VI) ions from aqueous solutions. The influence of analytical parameters including pH, adsorption time, amount of adsorbent, metal ion concentration, and temperature were investigated on the recovery of uranyl (VI) ion in aqueous solution. The maximum adsorption capacity (32.1 mg g?1) and fast equilibrium time (30 min) were achieved at pH of 4.5 at room temperature. Thermodynamic parameters (ΔH° = 2.695 kJ mol?1; ΔS° = 31.15 J mol?1 K?1; ΔG° = ?6.748 kJ mol?1) show the adsorption of an exothermic process and spontaneous nature, respectively. The possible coordination mechanism was illustrated. Adsorption and desorption coexist in aqueous solutions and then the system becomes equilibrium. 相似文献
998.
999.
利用现场红外光谱电化学、循环伏吸、导数循环伏吸法及其重构的电流-电位(i-E)曲线,研究对苯二酚(QH2)在不同溶剂中的电化学行为,得到可能的氧化还原机理。结果表明,在乙腈和中性非缓冲溶液中,QH2氧化终产物是对苯醌(Q)。在中性非缓冲溶液的还原的过程中,一部分Q在较正的电位下还原成QH2,另一部分Q在较负的电位下还原成Q2"。碱性溶液中,当加入1倍QH2量的OH-,循环伏安图(CV)出现2个电流相当的氧化峰(Q2",QH2);加入2倍OH-后,只出现一对氧化还原峰(Q2"/Q),从红外谱图上可清晰观察到电化学过程中氢键的变化。 相似文献
1000.
分别以La2O2CO3, CeO2, ZrO2和Al2O3为载体, 采用浸渍法制备了Ni基重整催化剂, 并以正十二烷模拟车载燃油进行催化重整反应以同时制备小分子碳氢化合物(HCs)和H2, 考察了其在4wt%Ag/Al2O3上选择性催化还原(HC-SCR)氮氧化物(NOx)的性能. 采用N2吸附-脱附、X射线粉末衍射、H2程序升温还原和热重等手段对Ni基催化剂进行了表征. 结果表明, 随着重整催化剂氧化还原性能增强, 产物中H2浓度增加, 可参与SCR反应的HCs含量减少, 从而导致重整-SCR耦合体系上NOx净化活性温度窗口向低温移动, NOx最高转化率降低. Ni/ZrO2+Ag/Al2O3耦合体系中H2/HCs符合SCR反应所需的最优比例, 在柴油车典型排气温度范围内表现出良好的NOx净化能力. 同时, 在Ni/ZrO2+Ag/Al2O3耦合体系上考察了其燃油重整-SCR的活性稳定性. 结果显示, 重整催化剂的耐久性有待进一步提高. 相似文献