全文获取类型
收费全文 | 809篇 |
免费 | 20篇 |
国内免费 | 14篇 |
专业分类
化学 | 485篇 |
晶体学 | 7篇 |
力学 | 42篇 |
数学 | 119篇 |
物理学 | 190篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 19篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 30篇 |
2013年 | 47篇 |
2012年 | 66篇 |
2011年 | 53篇 |
2010年 | 36篇 |
2009年 | 29篇 |
2008年 | 45篇 |
2007年 | 47篇 |
2006年 | 52篇 |
2005年 | 38篇 |
2004年 | 23篇 |
2003年 | 36篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1961年 | 4篇 |
1960年 | 4篇 |
1958年 | 3篇 |
1948年 | 3篇 |
排序方式: 共有843条查询结果,搜索用时 15 毫秒
61.
Nadanathangam Vigneshwaran Gopalakrishnapillai Bijukumar Nivedita Karmakar Sneh Anand Anoop Misra 《Macromolecular Symposia》2003,193(1):119-128
Isoelectric focusing (IEF) of glycated hemoglobin (GHb) was carried out in ultra-thin polyacrylamide gels to separate the hemoglobin-advanced glycation endproducts (Hb-AGEs) from the hemoglobin-A1C (HbA1C) fraction. Precast polyacrylamide gels (Ampholine® PAGplate) were used in Pharmacia LKB Multiphor II for this purpose. The separated bands for Hb-AGE and HbA1C based on their isoelectric point (pI), were confirmed with the purifed fractions obtained from the cation exchange chromatographic technique. From the calibration curve, the pI values were found to be 6.748 and 6.495 for HbA1C and Hb-AGE, respectively. The lowering of pI values for glycated hemoglobin, when compared to unglycated hemoglobin (pI = 6.852), can be attributed to the glycation at the amino terminals of the peptide chains. Increased reduction in pI value for Hb-AGE can be attributed to the effect of glycation of amino groups at various sites on the peptide chains, apart from the terminal amino groups. Fluorescence analysis was carried out for the purified fraction of Hb-AGE which showed the formation of a new fluorophor adduct having the excitation and emission maxima at 308 nm and 345 nm, respectively. Time-dependent formation of Hb-AGE under in vitro conditions was monitored by fluorescence (308/345 nm) over a period of 120 days, which showed its formation only after 3 weeks of incubation. 相似文献
62.
Summary The general course of reactions between [MCl4 ]2– (M = Pd, Pt) and primary and secondary phosphines containing phenyl, cyclohexyl, or 2-cyanoethyl groups, in polar solvents, is to yield L3MCl2 complexes which are probably ionic [L3MCl]+Cl– These compounds can be isolated and characterized in the solid state, but in solution they are labile, and tend to react to give phosphines plus L2 MCI2. 相似文献
63.
We carried out an efficient and facile synthesis of Zn(II) complexes with heterocyclic ligands based on 2-substituted benzothiazole moieties, 2-(2′-hydroxynaphthyl)benzothiazole, 2-(2′-hydroxyphenyl)benzothiazole, and 2-(2′-merceptophenyl)benzothiazole, and amino acids, glycine and alanine, are reported and also examined for antifungal and antibacterial activities. Ligands and complexes were characterized by FTIR, 1H NMR, and elemental analysis. 相似文献
64.
Jayashree Anand S. Palaniappan D. N. Sathyanarayana 《Journal of polymer science. Part A, Polymer chemistry》1998,36(13):2291-2299
Conducting poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) blends containing 10, 30, 50, 70, and 90 % wt/wt of polystyrene (PSt) were prepared by employing a two-step emulsion pathway. The bands characteristic of both polystyrene and POT/PMT are present in the IR spectra of POT–PSt and PMT–PSt blends. The UV-visible spectra of POT–PSt and PMT–PSt blends exhibit two bands around 313 and 610 nm, confirming that some amount of POT/PMT base is present in the blends. The EPR parameters such as line width and spin concentration reveal the presence of POT/PMT salt in the respective blends. The TGA, DTA, and DSC results suggest a higher thermal stability for the POT and PMT blends than that for the respective salts. The conductivity values of POT(70)–PSt(30) and POT(90)–PSt(10) blends are almost the same (1.1 × 10−2 and 1.3 × 10−2 S cm−1, respectively) and these values are very close to that of pure POT salt, suggesting that POT can be blended with up to 30% wt/wt of PSt to improve its mechanical properties without a significant drop in its conductivity. The conductivity values of PMT–PSt blends are lower than those of the corresponding POT–PSt blends by two to three orders of magnitude, indicating that POT is a better system than PMT to prepare blends by this method. The dielectric constant and tan δ values of the blends increase with the amount POT/PMT and are greater than that of polystyrene. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2291–2299, 1998 相似文献
65.
Venkatraman S Anand VG PrabhuRaja V Rath H Sankar J Chandrashekar TK Teng W Senge KR 《Chemical communications (Cambridge, England)》2002,(16):1660-1661
First successful syntheses and structural characterization of new core modified meso aryl azuliporphyrins by a simple [3 + 1] methodology are reported. 相似文献
66.
Srikumar G. Kuttuva Anand Sundararajan Lu-Kwang Ju 《Journal of Dispersion Science and Technology》2013,34(6-7):1003-1029
The W/O xanthan fermentation is simulated by integrating the microbial kinetic behaviors and the multiple-phase process characteristics. Model 1 assumes uniform redistribution of cells, substrates and product by frequent droplet breakup and coalescence. Model 2 simulates the system of viscous aqueous phase with minimal droplet breakup and component redistribution. The real fermentation should proceed within the bounds set by the two models. Effects of various parameters are evaluated. The aqueous-phase xanthan concentration (Xn) and volumetric productivity (QP) achieved at 200 h are used as the indicators. Xn and QP increase with nitrogen-source concentration (SNO) initially but plateau (Model 1) or decrease slightly (Model 2) at high SNO. Xn (at 200 h) decreases with increasing aqueous-phase volume fraction (f). QP, however, increases with f reflecting its basing on the total dispersion volume. Increasing agitation and aeration result in higher Xn and QP. The higher agitation enhances the G/O interfacial oxygen transfer and reduces the droplet size. Increasing aeration improves the G/O interfacial transfer but increases the droplet size. Its net positive effect implies a rate-limiting step at G/O interface. The W/O fermentation can produce far higher Xn (> 200 kg/m3) and QP( > 0.8 kg/m3-h) than the conventional fermentation (Xn ~ 50 kg/m3, QP ~ 0.5 kg/m3-h). 相似文献
67.
Processes for the production of xylenes, which occur in an integrated aromatic complex, are discussed. A brief overview of the work carried out at Indian Petrochemicals Corporation Limited for the development of zeolite-based catalytic processes for the production of aromatics is presented. This includes xylene isomerization, transalkylation and disproportionation of C7 and C9 aromatics for maximization of xylenes, selective disproportionation of toluene and selective alkylation of mono-alkylaromatics to p-dialkylbenzene. Achievements in the commercialization of zeolite-based catalysts and processes for isomerization of m-xylene to p- and o-xylene along with dealkylation of ethylbenzene, and for selective ethylation of ethylbenzene to produce p-diethylbenzene are highlighted. 相似文献
68.
Anand R Puri SC Verma N Handa G Khajuria RK Gupta VK Suri OP Qazi GN 《Journal of chromatographic science》2003,41(8):444-446
The present work describes isolation of bioactive lipophilic constituent [namely, hyperforin from St. John's wort (Hypericum perforatum L.)], of approximately 98% purity by semipreparative high-performance liquid chromatography (LC). The extraction, isolation, and analysis of the collected compound is performed without the use of antioxidants and inert gas atmospheres at all the stages. Hyperforin, separated isocratically on a 12microm semiprep column, is obtained in high purity, lyophilized after the removal of the organic phase, and preserved at a low temperature. The purity of the collected marker compound is estimated by the use of LC-mass spectrometry and spectroscopic techniques. 相似文献
69.
Rajesh Kumar Verma Sanjeet K. Verma Umesh Pankaj Anand K. Gupta Khushboo Khan Karuna Shankar 《Natural product research》2015,29(3):297-300
Andrographis paniculata Nees is an annual erect herb with wide medicinal and pharmacological applications due to the presence of andrographolide and other active chemical constituents. The large-scale cultivation of the kalmegh is not in practice. The aim of this study was to establish sustainable production systems of A. paniculata cv CIM-Megha with the application of different bioinoculants and chemical fertilisers. A. paniculata herb and andrographolide yield in the dried leaves was found to be highest (218% and 61.3%, respectively) in treatment T3 (NPK+Bacillus sp.) compared with T1 (control). The soil organic carbon, soil microbial respiration, soil enzymes activity and available nutrients improved significantly with combined application of bioinoculants and chemical fertilisers. 相似文献
70.
Sharma Vasundhara Anand Anjali Singh Bhupinder 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):291-300
Ecological half-lives of radiocesium were observed on Izu-Oshima Island, Japan, a place which experiences typhoons annually. The estimated ecological half-lives (uncertainty) based on the observations above an asphalt and a bare surface were 1.6 year (31.6%) and 1.9 year (14.4%), respectively; those of 134Cs and 137Cs in soil were 1.5 year (7.2%) and 4.0 year (5.9%), respectively. The radiation level was quickly returned to the original level compared to other locations that do not experience such typhoon activity.
相似文献