全文获取类型
收费全文 | 292篇 |
免费 | 22篇 |
专业分类
化学 | 209篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 27篇 |
物理学 | 67篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 9篇 |
2013年 | 17篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有314条查询结果,搜索用时 15 毫秒
61.
G. Sravya G. Suresh Grigory V. Zyryanov A. Balakrishna K. Madhu Kumar Reddy C. Suresh Reddy C. Venkataramaiah W. Rajendra N. Bakthavatchala Reddy 《Journal of heterocyclic chemistry》2020,57(1):355-369
A simple method was employed for the synthesis of dihydropyrano[3, 2-b]chromenedione derivatives ( 4a-o) in high yields by condensation of 5, 5-dimethylcyclohexane-1, 3-dione( 1 ), different aromatic aldehydes ( 2a-o ), and 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one( 3 ), using meglumine as a stable and reusable catalyst. Meglumine, an amino sugar, was employed as an environmentally benign catalyst, due to its splendid properties such as being inexpensive, recyclable, and biodegradable. The accomplished protocol employs low catalyst loading and easy work-up for the synthesis of 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one derivatives. A great asset is that without any significant loss, the catalyst could be recovered and reused for extended synthetic steps. This offer huge advantage to overcome recyclability issues. Our synthesized compounds were analyzed by IR, 1H, 13C NMR, mass spectra and evaluated for their antioxidant properties by 1, 1-diphenyl-2-picryl hydrazyl radical (DPPH), hydrogen peroxide(H2O2), and nitric oxide (NO) scavenging methods. The correlation in exhibition of antioxidant activity was effective at all doses. The binding interactions and molecular docking studies for entitled compounds were studied against 3MNG protein; 4k exhibited marked binding affinity with excellent docking score of −7.6 Kcal/mol and emerged as a lead compound. 相似文献
62.
Madasu Madhu Sai Reddy Doda Prem Kumar Begari Krishna Rao Dasari Gangadhar Thalari Sudhakar Kadari Jhillu Singh Yadav 《Journal of heterocyclic chemistry》2021,58(4):942-946
Enantioselective and a highly concise total synthesis of Ambrisentan are described. The chiral auxiliary controlled enantioselective epoxidation (Azerad protocol), photochemical regioselective epoxide opening, and base mediated ester hydrolysis reactions are the key reactions. 相似文献
63.
N. T. Madhu P. K. Radhakrishnan Matthias Grunert Peter Weinberger Wolfgang Linert 《Thermochimica Acta》2003,400(1-2):29-36
The phenomenological, kinetic and mechanistic aspects of thermal decomposition of perchlorate, nitrate, chloride, bromide and iodide complexes of cobalt(II) with the Schiff base 1,2-di(imino-4′-antipyrinyl)ethane (GA) have been studied by TG and DTG analyses. The kinetic parameters like the activation energy, pre-exponential factor and entropy of activation were calculated. The decomposition reactions follow “random nucleation with one nucleus on each particle—Mampel model”. 相似文献
64.
Srinivas Gajula Madasu Madhu Suresh Kumar Chintakrinda J.S. Yadav Debendra K. Mohapatra 《Tetrahedron letters》2018,59(47):4172-4175
A general approach for a collective synthesis of natural products containing substituted THF ring is described. In this paper, Arbusculone, a small molecule natural product accomplished using a short route, is used as the key intermediate to achieve the total synthesis of Andirolactone, Pinnatolide, Ipomolactone, Cyclocapitelline, Isocyclocapitelline and their two isomers in less than ten steps. The present effort highlights protecting-group-free total syntheses and the shortest route to access these natural products from commercially available cheap starting materials. 相似文献
65.
Combining Fullerenes and Zwitterions in Non‐Conjugated Polymer Interlayers to Raise Solar Cell Efficiency
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Yao Liu Dr. Madhu Sheri Marcus D. Cole Prof. Todd Emrick Prof. Thomas P. Russell 《Angewandte Chemie (International ed. in English)》2018,57(31):9675-9678
Polymer zwitterions were synthesized by nucleophilic ring‐opening of 3,3′‐(but‐2‐ene‐1,4‐diyl)bis(1,2‐oxathiolane 2,2‐dioxide) (a bis‐sultone) with functional perylene diimide (PDI) or fullerene monomers. Integration of these polymers into solar cell devices as cathode interlayers boosted efficiencies of fullerene‐based organic photovoltaics (OPVs) from 2.75 % to 10.74 %, and of non‐fullerene‐based OPVs from 4.25 % to 10.10 %, demonstrating the versatility of these interlayer materials in OPVs. The fullerene‐containing polymer zwitterion ( C60‐PZ ) showed a higher interfacial dipole (Δ) value and electron mobility than its PDI counterpart ( PDI‐PZ ), affording solar cells with high efficiency. The power of PDI‐PZ and C60‐PZ to improve electron injection and extraction processes when positioned between metal electrodes and organic semiconductors highlights their promise to overcome energy barriers at the hard‐soft materials interface of organic electronics. 相似文献
66.
S. Munichandra Reddy D. Subba Rao K. Madhu Ch. Subramanyam P. Gnana Kumari 《Phosphorus, sulfur, and silicon and the related elements》2018,193(3):136-140
A series of new 2-(benzo[d]thiazol-2-yl) phenyl-4-nitrophenyl alkyl/aryl substituted phosphoramidate derivatives (7a-j) of biological interest are synthesized in two steps via an in situ process without the isolation of the intermediate. 2-(Benzo[d]thiazol-2-yl) phenol (3) was treated with 4-nitrophenyl phosphorodichloridate(4) to obtain the monochloro intermediate, 2-(benzo[d]thiazol-2-yl)phenyl (4-nitrophenyl) phosphorochloridate(5). It was subsequently reacted with various amines, 6(a-j) to afford the desired title products. IR, NMR (1H, 13C and 31P), mass spectral and elemental analysis are used to characterize the structures of the newly synthesized compounds. The antibacterial and antifungal activities are determined by the growth of inhibition of bacteria and fungi of the title compounds at two concentrations, 50 and 100 µg/mL, and minimum inhibitory concentrations to the active compounds. The compounds 7e, 7f and 7j exhibited promising inhibition activity against bacterial strains and 7c, 7e and 7i against A. niger and C. albicans and MIC values are in the range of 10.0–15.0 µg/mL. 相似文献
67.
S. N. Bhadani Madhu Tiwari Archana Agrawal Chandra Sekhar Kavipurapu 《Mikrochimica acta》1994,117(1-2):15-22
A sensitive Spectrophotometric method for the determination of iron with tiron and a cationic surfactant, cetylpyridinium chloride, at pH 5.6 is reported. The complex is extracted into a chloroform-propan-2-ol (41) mixture and shows maximum absorbance at 520 nm. Beer's law is obeyed in the range 1–14 g/ml with an average molar absorptivity of 15800 l mol–1 cm–1. The molar ratio as determined by Job's method for Fe:tiron:CPC is 143. Interferences by various ions are examined. Zr, Ti and Mo interfere heavily. The method is applied for the determination of iron in Al-based and Cu-based alloys, using appropriate masking agents. 相似文献
68.
Amir Goldbourt Perunthiruthy K. Madhu 《Monatshefte für Chemie / Chemical Monthly》2002,16(8):1497-1534
Experimental and theoretical aspects of the multiple-quantum magic-angle spinning experiment (MQMAS) are discussed in this review. The significance of this experiment, introduced by Frydman and Harwood, is in its ability to provide high-resolution NMR spectra of half-integer quadrupolar nuclei (I ≥ 3/2). This technique has proved to be useful in various systems ranging from inorganic materials to biological samples. This review addresses the development of various pulse schemes aimed at improving the signal-to-noise ratio and anisotropic lineshapes. Representative spectra are shown to underscore the importance and applications of the MQMAS experiment. 相似文献
69.
S. N. Bhadani Madhu Tewari Archana Agrawal K. Chandra Sekhar 《Analytical and bioanalytical chemistry》1994,349(6):478-481
A red, water-soluble complex of nickel with PAR can be extracted into chloroform with CTAB at pH 7.0. The system obeys Beer's law upto 0.5 μg/ml with a molar absorptivity of 45 200 L·mol?1·cm?1 at 540 nm. Job's method of continuous variations revealed that the composition of the extracting species is 1:2:2 for nickel:PAR:CTAB. Based on this extraction, a highly sensitive and selective spectrophotometric method for the determination of nickel in polymetallic sea-bed nodules and in steels, after prior separation of iron and manganese, was developed. The standard deviation was 0.04–0.127 μg for 5–25 μg of nickel. 相似文献
70.
MHD boundary-layer flow of a non-Newtonian nanofluid past a stretching sheet with a heat source/sink
The goal of the present paper is to examine the magnetohydrodynamic effects on the boundary layer flow of the Jeffrey fluid model for a non-Newtonian nanofluid past a stretching sheet with considering the effects of a heat source/sink. The governing partial differential equations are reduced to a set of coupled nonlinear ordinary differential equations by using suitable similarity transformations. These equations are then solved by the variational finite element method. The profiles of the velocity, temperature, and nanoparticle volume fraction are presented graphically, and the values of the Nusselt and Sherwood numbers are tabulated. The present results are compared with previously published works and are found to be in good agreement with them. 相似文献