全文获取类型
收费全文 | 2170篇 |
免费 | 71篇 |
国内免费 | 7篇 |
专业分类
化学 | 1556篇 |
晶体学 | 86篇 |
力学 | 64篇 |
综合类 | 1篇 |
数学 | 108篇 |
物理学 | 433篇 |
出版年
2023年 | 16篇 |
2022年 | 31篇 |
2021年 | 41篇 |
2020年 | 38篇 |
2019年 | 48篇 |
2018年 | 36篇 |
2017年 | 60篇 |
2016年 | 89篇 |
2015年 | 42篇 |
2014年 | 59篇 |
2013年 | 201篇 |
2012年 | 117篇 |
2011年 | 140篇 |
2010年 | 89篇 |
2009年 | 76篇 |
2008年 | 122篇 |
2007年 | 97篇 |
2006年 | 100篇 |
2005年 | 75篇 |
2004年 | 62篇 |
2003年 | 53篇 |
2002年 | 52篇 |
2001年 | 29篇 |
2000年 | 32篇 |
1999年 | 24篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 21篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 23篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 22篇 |
1985年 | 15篇 |
1984年 | 27篇 |
1983年 | 18篇 |
1982年 | 26篇 |
1981年 | 26篇 |
1980年 | 18篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 17篇 |
1973年 | 16篇 |
排序方式: 共有2248条查询结果,搜索用时 17 毫秒
991.
992.
993.
994.
Method development and validation: quantitation of telmisartan bulk drug and its tablet formulation by 1H NMR spectroscopy 下载免费PDF全文
Yashwantsinh Jadeja Bhagyawanti Chomal Madhavi Patel Hetal Jebaliya Ranjan Khunt Anamik Shah 《Magnetic resonance in chemistry : MRC》2017,55(7):634-638
The quantitative NMR (qNMR) spectroscopy is nowadays a new tool for the determination of pharmaceutical potent biologically active molecules in bulk drug and its tablet formulation than the other analytical techniques. Herein, qNMR method was developed for an anti‐hypertensive drug, telmisartan in bulk drug and its tablet formulation. The precise method was developed by using malononitrile as an internal standard. The methylene signal of telmisartan appeared at δ = 5.46 ppm (singlet) relative to the signal of malononitrile at δ = 3.59 ppm (singlet) in CDCl3, as an NMR solvent. The development and validation of the method were carried out as per International Conference on Harmonization guidelines. The method was found to be linear (r2 = 0.9999) for 0.5 to 3.5 mg/ml in the drug concentration range. The relative standard deviation for accuracy and precession was not more than 2.0%. The sensitivity of the method was carried out by limit of detection and a limit of quantification, at 0.05 and 0.2 mg/ml, respectively, concentration. The robustness of the method was studied by changing parameters as well as different solvent manufacturer company. The result shows that method was accurately developed for quantification of telmisartan in pharmaceutical dosage form. The developed method by 1H NMR spectroscopy is comparatively easy and more precise with respect to the other analytical tools. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
995.
Abbul Bashar Khan Farooq Ahmed Wani Mehraj ud din Parray Maroof Ali Neeraj Dohare Rajan Patel 《印度化学会志》2022,99(1):100309
Herein, the electrical conductivity technique used to measure the critical micelle concentration (cmc) for pure cationic surfactants (Dodecyl/cetyltrimethylammonium bromides) and phenothiazine drug (Promethazine hydrochloride), as well as their different mole fractions in 10?3 ?mol/kg 1-methyl-3-octylimidazolium chloride (C8mim.Cl) at different temperatures. By using the cmc values the regular solution theory used to evaluate the micellar mole fraction for DTAB/CTAB-PMT mixed systems. The clint's model used to calculate the ideal critical micelle concentration (cmc1) that helps to evaluate the ideal micellar mole fraction for studied mixed systems, both explain the deviation from ideality. In addition, interaction parameter βm helps to confirm the nature of interaction (either antagonistic or synergistic) for the studied systems. The calculated parameters confirm a transition in the binding nature from antagonistic to synergistic with the increase in alkyl chain length of cationic surfactant i.e., component of the binary mixed system. The ease of micellization for the studied systems discussed by the standard Gibb's energy of micellization (), as well as the standard enthalpy and standard entropy of micellization were () and (), respectively to discuss the stability of the studied systems. 相似文献
996.
Transition metal [M = VO (IV) and/or Cu (II)] complexes with Schiff base ligand, (Z)‐2‐((2‐hydroxybenzylideneamino)phenol (H2L) have been entrapped in the super cages of zeolite‐Y by Flexible Ligand Method. Synthesized materials have been characterized by preferential physico‐chemical techniques such as inductively coupled plasma optical emission spectroscopy (ICP‐OES), elemental analyses (CHN), fourier transmission infrared spectroscopy (FTIR), electronic and UV‐reflectance spectra, Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron micrographs (SEMs), X‐ray diffraction patterns (XRD) and thermogravimetric analysis (TGA). The catalytic competence of zeolite‐Y entrapped transition metal complexes was examined in Baeyer‐Villiger (BV) oxidation of cyclopentanone using 30% H2O2 as an oxidant beside neat complexes to check the aptitude of heterogeneous catalysis over the homogeneous system. The effect of experimental variables such as mole ratio of substrate to an oxidant, amount of catalyst, reaction time, varying oxidants and solvents on the conversion of cyclopentanone was also tested. Under the optimized reaction conditions, one of the zeolite‐Y entrapped transition metal complex viz. [VO(L)H2O]‐Y [where L = (Z)‐2‐((2‐hydroxybenzylideneamino)phenol] was found to be a potential contender by providing 80.22% conversion of cyclopentanone (TON: 10479.42), and the selectivity towards δ‐valerolactone was 83.56%. 相似文献
997.
Synthesis,characterization and biological application of cyclometalated heteroleptic platinum(II) complexes 下载免费PDF全文
A series of square planar cyclometalated heteroleptic platinum(II) complexes of the type [(C^N)Pt(O^O)] [where, O^O is a β‐diketonato ligand of acetylacetone (acac), C^N = cyclometalating 7‐(4‐fluorophenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L1), 7‐(4‐chlorophenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L2), 7‐(4‐bromophenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L3), 7‐(4‐methoxyphenyl)‐5‐phenylpyrazolo[1,5‐a]pyrimidine (L4), 5‐phenyl‐7‐(p‐tolyl)pyrazolo[1,5‐a]pyrimidine (L5)] have been design, synthesized and characterized. All compounds have been screened for biological studies like in vitro antibacterial, in vitro cytotoxicity, cellular level cytotoxicity, absorption titration, viscosity measurements, fluorescence quenching analysis, molecular docking and DNA nuclease. The intrinsic binding constants (Kb) of compounds with HS‐DNA has been obtained in range of 2.892–0.242 × 105 M?1. All the compounds bound with HS DNA by partial intercalative mode of binding. MIC study has been carried out against Gram(+ve) and Gram(?ve) bacterial species. In vitro cytotoxicity against brine shrimp lethality bioassay has been also carried out. The LC50 values of the ligands and complexes have been found in range of 56.49–120.22 μg/mL and 6.71–11.96 μg/mL, respectively. 相似文献
998.
Transition Metal Chemistry - This work describes a simple impregnation and soaking method for designing of stabilized nickel exchanged supported 12-tungstophosphoric acid, its characterization and... 相似文献
999.
1000.
Fine‐Tuning of Saponification‐Triggered Gelation by Strategic Modification of Peripheral Substituents: Gelation Regulators 下载免费PDF全文
Ashish Kumar Roop Shikha Singh Amit Kumar Afsar Ali Arnab Biswas Prof. Dr. Daya Shankar Pandey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13799-13804
A pioneering approach towards controlling the efficiency of saponification assisted gelation in ethyl ester based ZnII‐complexes have been described. Using four new ester containing bis‐salen ZnII complexes ( C1–C4 ) involving different para‐azo phenyl substituted ligands it has been clearly shown that gelation efficiency is greatly influenced by the electronic effects of the substituents (‐H ( C1 ), ‐CH3 ( C2 ), ‐NO2 ( C3 ), and ‐OCH3 ( C4 )). Morphological, photophysical, and rheological investigations corroborated the experimental observations well and established that gelation efficiency was enhanced with electron‐withdrawing characteristics of substituents ( C4 < C2 < C1 < C3 ). This conclusion was also supported by DFT studies. 相似文献