全文获取类型
收费全文 | 2234篇 |
免费 | 82篇 |
国内免费 | 18篇 |
专业分类
化学 | 1492篇 |
晶体学 | 67篇 |
力学 | 71篇 |
数学 | 220篇 |
物理学 | 484篇 |
出版年
2023年 | 16篇 |
2022年 | 40篇 |
2021年 | 47篇 |
2020年 | 56篇 |
2019年 | 59篇 |
2018年 | 61篇 |
2017年 | 50篇 |
2016年 | 78篇 |
2015年 | 53篇 |
2014年 | 84篇 |
2013年 | 173篇 |
2012年 | 143篇 |
2011年 | 150篇 |
2010年 | 87篇 |
2009年 | 72篇 |
2008年 | 95篇 |
2007年 | 98篇 |
2006年 | 102篇 |
2005年 | 80篇 |
2004年 | 73篇 |
2003年 | 60篇 |
2002年 | 48篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 20篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 14篇 |
1994年 | 23篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 28篇 |
1983年 | 20篇 |
1982年 | 15篇 |
1981年 | 24篇 |
1980年 | 33篇 |
1979年 | 25篇 |
1978年 | 20篇 |
1977年 | 26篇 |
1976年 | 25篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有2334条查询结果,搜索用时 15 毫秒
1.
Chromatographia - We developed a simple, rapid, ecological RP-HPLC method for the estimation of Pitavastatin (PIT), Fenofibrate (FEN), and their impurities in a novel fixed dose combination. We... 相似文献
2.
Synthesis,spectral investigation and development of tetrahedral copper(II) complexes as artificial metallonucleases and antimalarial agents
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Seven new copper(II) complexes of type [Cu(A)(L)]?H2O (A = sparfloxacin, ciprofloxacin, levofloxacin, gatifloxacin, pefloxacin, ofloxacin, norfloxacin; L = 5‐[(3‐chlorophenyl)diazenyl]‐4‐hydroxy‐1,3‐thiazole‐2(3H)‐thione) were synthesized and characterized using elemental and thermogravimetric analyses, and electronic, electron paramagnetic resonance (EPR), Fourier transform infrared and liquid chromatography–mass spectroscopies. Tetrahedral geometry around copper is assigned in all complexes using EPR and electronic spectral analyses. All complexes were investigated for their interaction with herring sperm DNA utilizing absorption titration (Kb = 1.27–3.13 × 105 M?1) and hydrodynamic volume measurement studies. The studies suggest the classical intercalative mode of DNA binding. The cleavage reaction on pUC19 DNA was monitored by agarose gel electrophoresis. The results indicate that the Cu(II) complexes can more effectively promote the cleavage of plasmid DNA. The superoxide dismutase mimic activity of the complexes was evaluated by nitroblue tetrazolium assay, and the complexes catalysed the dismutation of superoxide at pH = 7.8 with IC50 values in the range 0.597–0.900 μM. The complexes were screened for their in vitro antibacterial activity against five pathogenic bacteria. All the complexes are good cytotoxic agents and show LC50 values ranging from 5.559 to 11.912 µg ml?1. All newly synthesized Cu(II) complexes were also evaluated for their in vitro antimalarial activity against Plasmodium falciparum strain (IC50 = 0.62–2.0 µg ml?1). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
3.
Nonlinear Dynamics - In the present work, we have studied a diffusive tritrophic food chain model in which the species at each trophic level interact in accordance with Crowley–Martin... 相似文献
4.
Dhanapal Kalaimegam Raman Mohan Kamatchi R. Kumaresan G. 《Journal of Thermal Analysis and Calorimetry》2021,144(1):233-243
Journal of Thermal Analysis and Calorimetry - The role of method of synthesis on the size of flakes, dispersion stability and thermophysical properties of aqua based reduced graphene oxide (rGO)... 相似文献
5.
6.
Raju Surapuraju Pavan Kumar Narayanam Mallikarjun Kumar Banothu Kranthi Tejaswee Sreeram Singh Saranjit 《Chromatographia》2015,78(19):1245-1250
Alendronate sodium is widely used in the treatment of osteoporosis and Paget’s disease. The HPLC method development for alendronate sodium, in particular, is challenging owing to the absence of chromophoric group and its high polarity. In the present study, a short and simple isocratic method was developed involving hydrophilic interaction liquid chromatography, coupled with a charged aerosol detector. The developed method was validated according to the ICH Q2(R1) guideline and was successfully applied for the analysis of a marketed formulation containing the drug.
相似文献7.
Padavattan Govindaswamy Patrick J. Carroll Yurij A. Mozharivskyj Mohan Rao Kollipara 《Journal of Chemical Sciences》2006,118(4):319-326
The reaction of [{(η5-C5Me5)M(μ-Cl)Cl}2] {where M = Rh (1), Ir (2)} with functionalized phosphine viz., diphenyl-2-pyridylphosphine (PPh2Py) in dichloromethane solvent yield neutral ϰ1-P-coordinated rhodium and iridium complexes [(η5-C5Me5)RhCl2(κ1-P-PPh2Py)]3 and [(η5-C5Me5) IrCl2(ϰ1-P-PPh2Py)]4. Reaction of complexes 1 and 2 with the ligand PPh2Py in methanol under reflux give bis-substituted complexes such as [(η5-C5Me5)RhCl(ϰ1-P-PPh2Py)2]+
5 and [(η5-C5Me5)IrCl(ϰ1-P-PPh2Py)2]+
6, whereas stirring in methanol at room temperature gives P-, N-chelating complexes of the type [(η5-C5Me5)RhCl(ϰ2-P-N-PPh2Py)]+ 7 and [(η5-C5Me5)IrCl(ϰ2-P-N-PPh2Py)]+
8. Neutral ϰ1-P-coordinated complexes [(η5-C5Me5)RhCl2(ϰ1-P-PPh2Py)]3 and [(η5-C5Me5)IrCl2(ϰ1-P-PPh2Py)]4 easily undergo conversion to the cationic P-, N-chelating complexes [(η5-C5Me5)RhCl(ϰ2-P-N-PPh2Py)]+
7 and [(η5-C5Me5) IrCl(ϰ2-P, N-PPh2Py)]+
8 on stirring in methanol at room temperature. These complexes are characterized by FT-IR and FT-NMR spectroscopy as well as
analytical methods. The molecular structures of the representative complexes [(η5-C5Me5)RhCl2(ϰ1-P-PPh2Py)]3, [(η5-C5Me5)IrCl2(ϰ1-P-PPh2Py)]4 and hexafluorophosphate salt of complex [(η5-C5Me5)IrCl(ϰ2-P-PPh2Py)2]+
6 are established by single-crystal X-ray diffraction methods 相似文献
8.
K. Batra V. Prasad M. Mohan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):191-198
The scattering of heavy ion with a multilevel Rydberg atom in the presence of an electromagnetic field is studied. The interaction
of Rydberg atom and the e.m field is explored using non-perturbative quasi-energy technique. Although the results are presented
for selected excitations but in actual calculations we have included many levels of the atom. The effect of various parameters
are shown on collisional excitation process. As an illustration detailed calculations are performed for the inelastic proton-Na
Rydberg atom collision accompanied by the transfer of photons and the effects of dressing due to the field are considered.
The emphasis of the present work is on collision induced transitions especially the case that involves change of orbital as
well as principal quantum number.
Received 26 December 2001 / Received in final form 8 April 2002 Published online 19 July 2002 相似文献
9.
N. Raju T. Špaček J. Ježek I. M. Caminiti F. Leinisch K. Hideg P. Ježek W. E. Trommer 《Applied magnetic resonance》2006,30(3-4):373-383
Electron paramagnetic resonance (EPR) spectroscopy of spin-labeled fatty acids was used to investigate their interaction withEscherichia coli-expressed human mitochondrial uncoupling protein UCP2 refolded from inclusion bodies in nonaethylene glycol monododecyl ether (C12E9) micelles. 5-DOXYL-stearic acid and 4-PROXYL-palmitic acid bound to UCP2 exhibited additional clearly separated h+1I, h?1I “immobile” peaks in the low- and high-field region, respectively, separated by 42 and 44 Gauss, and extensively reduced h+1M, h?1M “mobile” peaks, separated by about 30 G, whereas with 7-DOXYL-stearic acid the I and M peaks were smoothed together into one wide peak. Competition of 4-PROXYL-palmitic acid with added palmitic acid, arachidonic acid, and all-cis-8,11,14-eicosatrienoic acid and of 7-DOXYL-stearic acid with arachidonic acid was indicated by the disappearance of the h+1I, h?1I “immobile” peaks, whereas redistribution in micelles without protein was indicated by the rising of the h+1M, h?1M “mobile” peaks. In conclusion, a competition of palmitic, arachidonic, and eicosatrienoic acid within a putative fatty acid binding site was observed for mitochondrial uncoupling protein UCP2. This finding together with the observation of EPR spectra of highly immobilized probes exclusively in the presence of the recombinant UCP2 suggest the existence of a fatty acid binding site on UCP2 which is a prerequisite of the fatty acid cycling mechanism as previously postulated for UCP1. 相似文献
10.