全文获取类型
收费全文 | 548篇 |
免费 | 15篇 |
专业分类
化学 | 419篇 |
晶体学 | 15篇 |
力学 | 7篇 |
数学 | 28篇 |
物理学 | 94篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 13篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 21篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 24篇 |
2013年 | 48篇 |
2012年 | 40篇 |
2011年 | 36篇 |
2010年 | 22篇 |
2009年 | 16篇 |
2008年 | 29篇 |
2007年 | 15篇 |
2006年 | 16篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1994年 | 5篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1988年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1967年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有563条查询结果,搜索用时 15 毫秒
551.
Avinash Bhadani Sukhprit Singh Raman Kamboj Vinay Chauhan 《Colloid and polymer science》2013,291(10):2289-2297
Linear fatty alcohols on reaction with chloro/bromo acetic acid in the presence of catalytic amount of p-toluene sulphonic acid monohydrate under solvent-free conditions are converted into alkyl-2-haloacetate which on reaction with N-methyl pyrrolidine gives ester-functionalized pyrrolidinium surfactants. Thus, new series of ester-functionalized heterocyclic pyrrolidinium head group containing cationic surfactants have been synthesized by green approach via energy saving and cost effective methodology. These new surfactants have been investigated for their surface properties by surface tension, conductivity, and fluorescence method. Surface properties of these surfactants have been found to be far better compared to conventional heterocyclic cationic surfactants having similar hydrophobic alkyl chain length. 相似文献
552.
553.
554.
Sk. Sarif Hassan Shinjini Ghosh Diksha Attrish Pabitra Pal Choudhury Alaa A. A. Aljabali Bruce D. Uhal Kenneth Lundstrom Nima Rezaei Vladimir N. Uversky Murat Seyran Damiano Pizzol Parise Adadi Antonio Soares Tarek Mohamed Abd El-Aziz Ramesh Kandimalla Murtaza M. Tambuwala Gajendra Kumar Azad Samendra P. Sherchan Wagner Baetas-da-Cruz Kazuo Takayama ngel Serrano-Aroca Gaurav Chauhan Giorgio Palu Adam M. Brufsky 《Molecules (Basel, Switzerland)》2020,25(24)
Angiotensin-converting enzyme 2 (ACE2) is the cellular receptor for the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that is engendering the severe coronavirus disease 2019 (COVID-19) pandemic. The spike (S) protein receptor-binding domain (RBD) of SARS-CoV-2 binds to the three sub-domains viz. amino acids (aa) 22–42, aa 79–84, and aa 330–393 of ACE2 on human cells to initiate entry. It was reported earlier that the receptor utilization capacity of ACE2 proteins from different species, such as cats, chimpanzees, dogs, and cattle, are different. A comprehensive analysis of ACE2 receptors of nineteen species was carried out in this study, and the findings propose a possible SARS-CoV-2 transmission flow across these nineteen species. 相似文献
555.
Ghanshyam S. Chauhan Harinder Lal Swati Mahajan Monica Bansal 《Journal of polymer science. Part A, Polymer chemistry》2000,38(24):4506-4518
To get highly reactive polymeric materials for selective studies of enzyme immobilization, water purification, separation, and enrichment technologies, we attempted to graft 4‐vinyl pyridine (4‐VP) onto Teflon‐PFA by simultaneous γ‐ray initiation. The resulting graft copolymers were quaternized by treatment with some alkylating agents. Optimum conditions for grafting were evaluated through the variation of the total dose of radiation, the amount of water, and the monomer concentration. The effect of the solvent composition (H2O/MeOH) was also studied. In the presence of MeOH, grafting occurred less often and was nonselective as 4‐VP was incorporated on both sides in comparison with highly selective grafting in an aqueous medium. The percentages of the grafting, total conversion, and grafting efficiency and the rates of the polymerization, grafting, and homopolymerization were also evaluated. Some other monomers such as methacrylic acid, methyl methacrylate, maleic acid, acrylonitrile, and vinyl imidazole were not incorporated onto the backbone film under the optimum grafting reaction conditions evaluated for the grafting of 4‐VP. Although some grafting occurred, the graft yield was too low to be considered of any significance. The grafted films were quaternized with benzyl chloride, and quaternized and unquaternized films were used for the immobilization of lipase. The former showed high activity with lipase and has potential for development as a bioreactor. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4506–4518, 2000 相似文献
556.
Yong Chen Chwen‐Yang Shew Chukwunonso Gbemudu Bhanu P. S. Chauhan 《Macromolecular theory and simulations》2004,13(1):54-63
Summary: We have conducted Monte Carlo simulations to investigate a greatly simplified model for a blend composed of templated materials (polymers or monomers), smaller reacting particles and solvents on a two‐dimensional lattice. In the simulations, we compute the mean chain conformation of flexible templated polymers, and the distribution of the number of adjacent reacting particles aligned along the same axis to rationalize how templated materials affect the physical aggregation of smaller particles in a blend. We first examine the effects of the effective interactions between templated materials and smaller reacting particles. For repulsive interactions, flexible templated polymers tend to contract to reduce repulsions arising from smaller reacting particles, but for attractive interactions, mean chain dimension increases to maximize attraction. When templated material composition is increased, the conformational deformation of templated polymers becomes more pronounced. Moreover, in the presence of attractive interactions, reacting particles are more dispersed in the blend. In contrast, repulsive interactions increase the probability of aggregation of reacting particles. Also, our findings show that templated monomers (without chain connectivity) interact with reacting particles more effectively than with templated polymers due to the greater interacting area per monomer, which enhances the dispersion and segregation of reacting particles in the blend due to the attractive and repulsive interaction, respectively. In addition, as templated material composition is increased, the probability of forming a larger aggregate decreases. This simple model allows us to elucidate the role of templated materials on the physical aggregation of smaller particles in a blend.
557.
Summary Reaction of aromatic thioamides, LH, withcis-[Ru(CO)2Cl2] yieldscis-[Ru(CO2)Cl2LH]. The complexes have been characterised by analytical, i.r., electronic and n.m.r. spectral and magnetic measurements. All the RuII diamagnetic complexes have been assigned distorted octahedral geometry. 相似文献
558.
Phadtare S Vinod VP Wadgaonkar PP Rao M Sastry M 《Langmuir : the ACS journal of surfaces and colloids》2004,20(9):3717-3723
We demonstrate herein the formation of a free-standing gold nanoparticle membrane and its use in the immobilization of the enzyme, pepsin. The nanogold membrane is synthesized by the spontaneous reduction of aqueous chloroaurate ions at the liquid-liquid interface by the bifunctional molecule bis(2-(4-aminophenoxy)ethyl) ether (DAEE) taken in chloroform. This process results in the formation of a robust, malleable free-standing nanogold membrane consisting of gold nanoparticles embedded in a polymeric background. Recognizing that gold nanoparticles are excellent candidates for immobilization of enzymes, we have immobilized pepsin on the nanogold membrane, leading to a new class of biocatalyst. A highlight of the new pepsin-nanogold biocatalyst is the ease with which separation from the reaction medium may be achieved. The catalytic activity of pepsin in the bioconjugate was comparable to that of the free enzyme in solution. The pepsin-nanogold membrane bioconjugate material exhibited excellent biocatalytic activity over 10 successive reuse cycles as well as enhanced pH, temperature, and temporal stability. 相似文献
559.
Umar A Chauhan MS Chauhan S Kumar R Kumar G Al-Sayari SA Hwang SW Al-Hajry A 《Journal of colloid and interface science》2011,363(2):521-528
This paper reports a large-scale synthesis of ZnO balls made of fluffy thin ZnO nanosheets by simple solution process at low-temperature of 65±2°C. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties. The detailed morphological characterizations, done by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), confirmed that the synthesized products are ZnO balls which are made by accumulation of hundreds of thin ZnO nanosheets. Interestingly, it is seen that the nanosheets are arranged in such a special fashion that they made ball-like morphologies. Detailed structural examinations revealed that of as-synthesized ZnO products are well-crystalline and possessing wurtzite hexagonal phase. The optical property, measured by UV-Visible spectroscopy, substantiated good optical properties for as-synthesized ZnO balls. The as-synthesized ZnO balls were utilized as an efficient photocatalysts for the photocatalytic degradation of methylene blue (MB) dye. Almost complete degradation of MB was observed in presence of ZnO balls composed of nanosheets within 70 min under UV-light irradiation. By comparing the photocatalytic performance with commercially available TiO(2)-UV-100, it was observed that the synthesized ZnO balls exhibited superior photocatalytic performance as compared to TiO(2)-UV-100 photocatalyst. 相似文献
560.
The precipitation magnesium oxalate dihydrate, calcium oxalate monohydrate, strontium oxalate monohydrate and barium oxalate hemihydrate was studied from equivalent solutions of concentrations from 0.001 M to 0.5 M, at pHs from 7 to 6, by optical microscopy and other methods. Crystal growth started after induction periods: the precipitations were heterogeneously nucleated at low supersaturations and homogeneously nucleated at medium to high supersaturations. The crystal form and numbers of the final precipitates depended on the type and number of the nuclei (and crystallites) formed during the induction periods. Crystal numbers at medium to high supersaturation, increased with increasing initial mean metal oxalate concentrations according to the relation, N = N1c; β was 5 for calcium oxalate precipitations and β was 6 for the other metal oxalate precipitations. The N1 values increased in the order MgC2O4 · 2 H2O < BaC2O4 · 1/2 H2O < SrC2O4 · H2O < CaC2O4 · H2O. The final crystal lengths, in this supersaturation range, then decreased (from maximum values) with increasing initial concentrations according to the relation, lfin = l1/CMOxβ, where γ was 1.3 to 1.6. For precipitations from solution of any concentration at any pH, smaller crystals were obtained in the precipitates of the metal oxalate of lower solubility. 相似文献