全文获取类型
收费全文 | 1884篇 |
免费 | 113篇 |
国内免费 | 42篇 |
专业分类
化学 | 1442篇 |
晶体学 | 11篇 |
力学 | 85篇 |
数学 | 189篇 |
物理学 | 312篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 31篇 |
2021年 | 71篇 |
2020年 | 101篇 |
2019年 | 91篇 |
2018年 | 119篇 |
2017年 | 91篇 |
2016年 | 147篇 |
2015年 | 97篇 |
2014年 | 139篇 |
2013年 | 232篇 |
2012年 | 150篇 |
2011年 | 148篇 |
2010年 | 126篇 |
2009年 | 109篇 |
2008年 | 114篇 |
2007年 | 73篇 |
2006年 | 41篇 |
2005年 | 30篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 20篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有2039条查询结果,搜索用时 15 毫秒
891.
Capillary electrophoretic analysis of individual submicrometer size particles has been previously done using custom-built instruments. Despite that these instruments provide an excellent signal-to-noise ratio for individual particle detection, they are not capable of performing automated analyses of particles. Here we report the use of a commercial Beckman P/ACE MDQ capillary electrophoresis (CE) instrument with on-column laser-induced fluorescence (LIF) detection for the automated analysis of individual particles. The CE instrument was modified with an external I/O board that allowed for faster data acquisition rates (e.g. 100 Hz) than those available with the standard instrument settings (e.g. 4 Hz). A series of eight hydrodynamic injections expected to contain 32 +/- 6 particles, each followed by an electrophoretic separation at -300 V cm(-1) with data acquired at 100 Hz, showed 28 +/- 5 peaks corresponding to 31.9 particles as predicted by the statistical overlap theory. In contrast, a similar series of hydrodynamic injections followed by data acquisition at 4 Hz revealed only 8 +/- 3 peaks suggesting that the modified system is needed for individual particle analysis. Comparison of electropherograms obtained at both data acquisition rates also indicate: (i) similar migration time ranges; (ii) lower variation in the fluorescence intensity of individual peaks for 100 Hz; and (iii) a better signal-to-noise ratio for 4 Hz raw data. S/N improved for 100 Hz when data were smoothed with a binomial filter but did not reach the S/N values previously reported for post-column LIF detection. The proof-of-principle of automated analysis of individual particles using a commercially available CE system described here opens exciting possibilities for those interested in the study and analyses of organelles, liposomes, and nanoparticles. 相似文献
892.
Hossein Rezaei 《Journal of Dispersion Science and Technology》2016,37(7):969-979
The aim of this work was to apply dissipative particle dynamics (DPD) mesoscopic simulations to study the interfacial orientation and the effect of the nonionic surfactant, hexaethylene glycol monododecyl ether (C12E6), on different (oil (dodecane)/water) microemulsion systems. The Hildebrand-solubility-parameter model and Flory–Huggins/Hansen-solubility-parameter (FH/HSP) model were combined to evaluate the DPD interaction parameter (aij) where the solubility parameters (δi) as DPD input parameters were preliminary validated by all-atom molecular dynamics (MD) results and experimental data. The interfacial property dependence of dodecane/water/C12E6 system on the oil/water (o/w) ratio and on the concentration of surfactant and orientation at the interface were investigated. It was found that the surfactant addition reduced the IFT of o/w interfaces and this reduction was more efficient for water-in-oil microemulsions (o/w ≤ 1). 相似文献
893.
Thermodynamic Studies of Insulin Loading into a Glucose Responsive Hydrogel Based on Chitosan‐polyacrylamide‐polyethylene Glycol
下载免费PDF全文
![点击此处可从《中国化学会会志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The insulin therapy constitutes the preferred treatment for Diabetes Mellitus (DM). The traditional insulin therapy, which consists of daily subcutaneous insulin injections to control blood glucose level, is not able to regulate the blood glucose level precisely. In this research, to facilitate the diabetic patient life, an intelligent drug delivery system based on a biodegrable biopolymer to control the insulin release, was designed. In this system, chitosan‐polyethylene glycol hydrogel and glucose oxidize play the role of drug carrier and glucose biosensor, respectively. To increase the hydrogel drug loading capacity, hydrogels with different PEG content were synthesized and insulin was loaded by swelling‐diffusion method into them. The loaded hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), High performance liquid chromatography (HPLC), and Thermogravimetric analysis (TGA). Finally, the thermodynamic study for insulin loading process was performed to investigate the stability of the drug in the system. 相似文献
894.
Simple Approach to Predict Corrosion Inhibition Efficiency of Imidazole and Benzimidazole Derivatives as well as Linear Organic Compounds Containing Several Polar Functional Groups
下载免费PDF全文
![点击此处可从《无机化学与普通化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mohammad Hossein Keshavarz Karim Esmaeilpour Ahmad Nozad Golikand Zeinab Shirazi 《无机化学与普通化学杂志》2016,642(16):906-913
895.
Vahideh Zadsirjan Majid M. Heravi Mahmoud Tajbakhsh Hossein A. Oskooie Morteza Shiri Tayebeh Hosseinnejad 《Research on Chemical Intermediates》2016,42(7):6407-6422
Hydroarylation of cinnamic acid with different substituted phenols, in the presence of acidic ionic liquid, N-methyl-2-pyrrolidonum hydrosulfate ([H-NMP]HSO4) gave the corresponding dihydrocoumarins in high yields and excellent selectivity. Among these substituted phenols, while methyl phenol afforded the corresponding dihydrocoumarin, nitrophenol under the same reaction conditions diverted the course of reaction, affording 3-(4-nitrophenyl)-3-phenylpropanoic acids. We investigated this behavior from the energetic and electronic points of view, using quantum chemistry computational methods. In this respect, the electronic energy change values for the conversion reaction of substituted phenyl cinnamate esters to dihydrocoumarin compounds have been obtained via density functional theory calculations. We demonstrated that the conversion reaction in the presence of CH3 substituent is more favorable energetically than NO2 substituent. Moreover, we have concentrated on topological analysis of electron density on some key bond and ring critical points and their associated bond paths to assess the conversion of substituted phenyl cinnamate esters to dihydrocoumarins. Our calculated results showed that para-methyl phenyl cinnamate has more of electronic tendency to undergo the intramolecular cyclization step and, consequently, generate the corresponding dihydrocoumarin. 相似文献
896.
Safaei-Ghomi Javad Asgari-Keirabadi Mehrnoosh Khojastehbakht-Koopaei Bahareh Shahbazi-Alavi Hossein 《Research on Chemical Intermediates》2016,42(2):827-837
Research on Chemical Intermediates - CeO2 nanoparticles have been used as an efficient catalyst for the preparation of C-tethered bispyrazol-5-ols by pseudo five-component reaction of... 相似文献
897.
898.
899.
900.
Polymerization of ethylene using a series of binuclear and a mononuclear Ni (II)‐based catalysts
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mostafa Khoshsefat Gholam Hossein Zohuri Navid Ramezanian Saeid Ahmadjo Meisam Haghpanah 《Journal of polymer science. Part A, Polymer chemistry》2016,54(18):3000-3011
A novel series of homo‐, bi‐, and mononuclear Ni(II)‐based catalysts (BNCn n = 1–4, MNC4) were used for ethylene polymerization. The optimum conditions for the catalyst BNC4 (the highest catalytic activity) was obtained at [Al]/[Ni]=2000/1, Tp = 42 °C, and tp = 20 min that was 1073 g PE/mmol Ni h. In theoretical study, steric and electronic effects of substituents and diimine backbone led to prominent influence on the catalyst behavior. The highest MV was resulted from polymerization using BNC4; however, the highest unsaturation content was obtained from BNC1. GPC analysis showed a broad MWD (PDI = 17.8). BNC1 and BNC2 in similar structures showed broad peaks in DSC thermogram, while BNC3 and BNC4 with more electronic effects showed a peak along with a wide shoulder. Monomer pressure increasing showed enhancing in activity of the BNC4, meanwhile a peak with shoulder to a single peak in DSC thermogram and uniformity in morphology of the resulted polymer were observed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3000–3011 相似文献