全文获取类型
收费全文 | 170篇 |
免费 | 13篇 |
专业分类
化学 | 144篇 |
力学 | 12篇 |
数学 | 15篇 |
物理学 | 12篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 14篇 |
2009年 | 8篇 |
2008年 | 11篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有183条查询结果,搜索用时 62 毫秒
91.
Farshad Darvishi Jacqueline Destain Iraj Nahvi Philippe Thonart Hamid Zarkesh-Esfahani 《Applied biochemistry and biotechnology》2012,168(5):1101-1107
The extracellular lipase of Yarrowia lipolytica presents numerous potentialities for biotechnological applications. This work describes the development and storage of powders obtained from supernatants containing Y. lipolytica lipase by freeze-drying as downstream process that is important in obtaining a stable lipase powder with high enzymatic activity. Lipase was produced by Y. lipolytica U6 mutant strain in 20-L bioreactor. Non-concentrated cell-free culture supernatant samples were supplemented with different concentrations (0.5?C1?%) of maltodextrin and glycerol as additives to freeze-drying. Effects of additives, temperature, pH, and storage time on lipase powders were determined. After addition of additives, freeze-drying yield increased 3.5-fold compared to supernatant without additive. Maltodextrin with 0.5?% concentration gave the best protection of lipase during dehydration treatment and its freeze-drying yield (77?%) is better than other formulations. Lipase powders were stored at 4 and 25?°C for 46?weeks without loss of lipase activity. A common impediment to the production of commercial enzyme is their low-stability aqueous solutions. The present study shows that freeze-dried lipase powders of Y. lipolytica have good stability for storage and various applications. 相似文献
92.
Hossein Salavati Shahram Tangestaninejad Majid Moghadam Valiollah Mirkhani Iraj Mohammadpoor-Baltork 《Ultrasonics sonochemistry》2010,17(2):453-459
A Keggin type polyoxometalate (POM) has been immobilized in the unique network structure of multi-wall carbon nanotubes (CNTs). The vanadium-containing polyphosphomolybdate (PVMo) supported on CNTs, which was prepared by a one-step solid-state reaction, was characterized by FT-IR, XRD, SEM and elemental analyses. These uniform nanoparticles have an average size 20–30 nm. Furthermore, due to the chemical interaction between PVMo and carboxylic acid groups, PVMo nanoparticles were successfully immobilized on the CNTs. Moreover, the obtained composite was found as an efficient catalyst for oxidation of hydrocarbons under reflux and ultrasonic irradiation (US) conditions. 相似文献
93.
Reyhaneh Hoseinpoor Seyed Latif Mousavi Gargari Iraj Rasooli Masoumeh Rajabibazl Bahareh Shahi 《Applied biochemistry and biotechnology》2014,172(6):3079-3091
Manipulation of clinically significant antibodies can effectively improve the processes of diagnosis and treatment. Affinity maturation process has a significant role in improvement of antibodies efficiency. Error-prone PCR technique is one of the proposed methods for improvement of the affinity of antibodies. In the present research, a method was applied to camel heavy-chain antibody (VHH, nanobody) raised against UreC subunit of urease enzyme from Helicobacter pylori. This VHH was used as a starting molecule to construct a highly diversified phage displayed VHH library. The constructed library of nanobody mutants was subjected to several rounds of panning against UreC antigen. High-affinity mutant was selected. Our VHH (HMR23) showed 1.5-fold higher binding activity than the parental VHH. In addition, the mutant VHH presented a better performance in inhibition of urease activity at low concentrations retaining its specificity and thermal stability. 相似文献
94.
Efficient and Eco‐friendly Syntheses of 1,5‐Benzothiazepines and 1,5‐Benzodiazepines Catalyzed by [Hmim][NO3] under Mild Conditions 下载免费PDF全文
Hossein Loghmani‐Khouzani Panteha Tamjidi Iraj Mohammadpoor‐Baltork Marzieh Yaeghoobi Noorsaadah Abd. Rahman Ahmad Reza Khosropour Majid Moghadam Shahram Tangestaninejad Valiolah Mirkhani Mohammad Hossein Habibi Ayana Kashima Takayoshi Suzuki 《Journal of heterocyclic chemistry》2014,51(1):138-150
This article presents a synthetic method and reaction mechanism of the 1,5‐benzothiazepines and 1,5‐benzodiazepines derivatives. In this research, 36 thiazepines and diazepines (mostly new) with a new method have been prepared and their structures have been characterized by spectroscopic methods. Crystal structures of a new thiazepine and diazepine (seven‐membered rings) have also been determined and compared with thiazine (six‐membered ring). In this method, N‐methylimidazolium nitrate [Hmim][NO3] has been used as a catalyst that acts as an environmental friendly system. 相似文献
95.
Zahra Nadealian Valliolah Mirkhani Bahram Yadollahi Majid Moghadam Shahram Tangestaninejad Iraj Mohammadpoor-Baltork 《Journal of the Iranian Chemical Society》2013,10(4):777-782
The catalytic activity of [bmim]5[PW11ZnO39]·3H2O as a hybrid catalyst was studied in the oxidation of various alkenes in acetonitrile, using hydrogen peroxide as oxygen source. The effect of reaction parameters such as type of solvent and oxidant, amount of catalyst and oxidant, and temperature was also investigated. From our results, [bmim]5[PW11ZnO39]·3H2O hybrid catalyst gave higher yields and selectivity in the oxidation of alkenes and was reused four times without loss of its catalytic activity. 相似文献
96.
Hadi Kargar Majid Moghadam Valiollah Mirkhani Shahram Tangestaninejad Iraj Mohammadpoor-Baltork Simindokht Rezaei 《Transition Metal Chemistry》2013,38(1):1-5
The oxidation of 2-substituted imidazolines with sodium periodate catalyzed by tetrakis(p-aminophenyl)-porphyrinatomanganese(III) chloride, [Mn(TNH2PP)Cl], supported on functionalized multi-wall carbon nanotubes is reported. A wide variety of 2-imidazolines were efficiently converted to their corresponding imidazoles by this catalytic system. When the same reaction was subjected to ultrasonic irradiation, the reaction times were reduced significantly and the product yields were increased. This catalyst could be reused several times without significant loss of activity. The effects of reaction parameters such catalyst amount, choice of solvent, and the effects of ultrasonic irradiation on the catalytic activity have been investigated. 相似文献
97.
98.
Maryam Moosavifar Shahram Tangestaninejad Majid Moghadam Valiollah Mirkhani Iraj Mohammadpoor-Baltork 《Comptes Rendus Chimie》2011,14(10):953-956
In the present work, a mild and efficient method has been developed for the synthesis of acylals from aldehydes with acetic anhydride in the presence of molybdophosphoric acid encapsulated into dealuminated zeolite Y (MPA-DAZY) as a catalyst under solvent-free conditions at 45–55 °C in good to excellent yield. The deprotection of acylals has also been attained using this catalyst in acetonitrile. The catalyst was reused several times without efficient loss of its catalytic activity. 相似文献
99.
Iraj Behroz Dr. Patrick Durkin Dr. Stefan Grätz Maria Seidel Lida Rostock Marcello Spinczyk Dr. John B. Weston Prof. Dr. Roderich D. Süssmuth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(72):16538-16543
Albicidin is a recently described natural product that strongly inhibits bacterial DNA gyrase. The pronounced activity, particularly against Gram-negative bacteria, turns it into a promising lead structure for an antibacterial drug. Hence, structure–activity relationship studies are key for the in-depth understanding of structural features/moieties affecting gyrase inhibition, antibacterial activity and overcoming resistance. The 27 newly synthesized albicidins give profound insights into possibilities for variations of the C-terminus. Furthermore, in the present study, a novel derivative has been identified as overcoming resistance posed by the Klebsiella-protease AlbD. Structural modifications include, for example, azahistidine replacing the previous instable cyanoalanine as the central amino acid, as well as a triazole amide bond isostere between building blocks D and E. 相似文献
100.