首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1528篇
  免费   96篇
  国内免费   69篇
化学   1609篇
晶体学   9篇
综合类   2篇
数学   3篇
物理学   70篇
  2024年   4篇
  2023年   27篇
  2022年   166篇
  2021年   170篇
  2020年   100篇
  2019年   62篇
  2018年   53篇
  2017年   45篇
  2016年   89篇
  2015年   67篇
  2014年   57篇
  2013年   88篇
  2012年   68篇
  2011年   73篇
  2010年   66篇
  2009年   65篇
  2008年   61篇
  2007年   57篇
  2006年   48篇
  2005年   46篇
  2004年   42篇
  2003年   30篇
  2002年   29篇
  2001年   16篇
  2000年   18篇
  1999年   21篇
  1998年   12篇
  1997年   14篇
  1996年   12篇
  1995年   9篇
  1994年   9篇
  1993年   12篇
  1992年   7篇
  1991年   10篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1987年   4篇
  1986年   5篇
  1985年   2篇
  1984年   3篇
  1983年   3篇
  1982年   4篇
  1980年   2篇
  1978年   1篇
排序方式: 共有1693条查询结果,搜索用时 15 毫秒
91.
随着人口老龄化进程的发展,阿尔茨海默症(AD)已成为威胁中国和世界人口健康和经济的重大疾病.本文综述了近年来AD病理的分子机制的新进展,分析了其中金属代谢的意义.研究发现,在AD进程中,围绕淀粉样斑块(AP)和神经缠绕斑(NFT)的形成,多因素相互联系并发挥作用,这些主要因素包括金属内稳态、胰岛素抵抗、神经炎症、线粒体和血脑屏障改变等.与AD病理过程密切相关的主要蛋白质均参与了金属元素的生理代谢过程,而细胞金属离子的内稳态失衡加剧了AD病理的恶化.金属药物在AD诊断和治疗中可能具有以下的发展潜力:(1)AD早期诊断探针;(2)调节金属内稳态的配体和/或微量元素补充;(3)抗糖尿病金属配合物;(4)神经元和血脑屏障(BBB)保护金属药物.  相似文献   
92.
Gold (III)-N,N-dimethyldithiocarbamate [DMDT(Au)X2] complexes have recently gained increasing attention as potential anticancer agents because of their strong tumor cell growth–inhibitory effects, generally achieved by exploiting non-cisplatin-like mechanisms of action. The goal of our research work is to encapsulate the gold(III) dimethyldithiocarbamate complexes as anticancer with cucurbit[n]urils (CB[n = 5, 6]) by accurate calculations, to predict the inclusion complex formation of gold(III) species with cucurbiturils (CB[n = 5, 6]). The calculations were carried out just for the 1:1 stoichiometric complexes. Upon encapsulation, binding energy, thermodynamic parameters, structural parameters and electronic structures of complexes are investigated. The results of the thermodynamic calculations and the binding energy show that the inclusion process is exothermic and the CB[6]/[DMDT(Au)Br2] complex is more stable than other complexes. The final geometry of CB[n]/drugs indicates that the drugs were expelled from the cavity of CB[n]. NBO calculations reveal that the hydrogen bonding between CB[n] and drugs and electrostatic interactions are the major factors contributing to the overall stabilities of the complexes.  相似文献   
93.
Elevated levels of reactive oxygen species (ROS) and deficient mitochondria are two weak points of cancer cells. Their simultaneous targeting is a valid therapeutic strategy to design highly potent anticancer drugs. The remaining challenge is to limit the drug effects to cancer cells without affecting normal ones. We have previously developed three aminoferrocene (AF)-based derivatives, which are activated in the presence of elevated levels of ROS present in cancer cells with formation of electron-rich compounds able to generate ROS and reduce mitochondrial membrane potential (MMP). All of them exhibit important drawbacks including either low efficacy or high unspecific toxicity that prevents their application in vivo up to date. Herein we describe unusual AF-derivatives lacking these drawbacks. These compounds act via an alternative mechanism: they are chemically stable in the presence of ROS, generate mitochondrial ROS in cancer cells, but not normal cells and exhibit anticancer effect in vivo.  相似文献   
94.
Recently, pharmaceuticals and personal care products in the water environment exhibited potential risks to both human and aquatic organisms. In order to improve the sensitivity and accuracy of pharmaceutical detection, the polyimidazolyl acetate ionic liquid was synthesized by Radziszewski reaction and coated on cellulose filter papers as a thin-film extraction phase for extraction of non-steroidal anti-inflammatory drugs from water. The attenuated total reflection-infrared spectrometry, thermogravimetric analysis, and scanning electron microscope analyses demonstrated that the polyimidazolyl acetate ionic liquid was successfully prepared and attached to the surface of the cellulose filter paper through chemical bonding. The adsorption capacity of the homemade thin-film extraction material for the four non-steroidal anti-inflammatory drugs was greater than 8898 ng/cm2 under the optimum conditions, and the desorption rate was over 90%. Then, a paper-based thin-film extraction phase-high-performance liquid chromatography-tandem mass spectrometry method was established for the extraction of non-steroidal anti-inflammatory drugs in water. This method provided limits of detection and limits of quantification were in the range of 0.02–0.15 and 0.17–0.50 μg/L, respectively. Hence, the obtained thin-film extraction phase showed excellent recovery and reproducibility for the target non-steroidal anti-inflammatory drugs with carboxyl groups from water.  相似文献   
95.
Nanoformulations of mononuclear Pt complexes cis-PtCl2(PPh3)2 ( 1 ), [Pt(PPh3)2(L−Cys)] ⋅ H2O ( 3 , L−Cys=L-cysteinate), trans-PtCl2(PPh2PhNMe2)2 ( 4 ; PPh2PhNMe2=4-(dimethylamine)triphenylphosphine), trans-PtI2(PPh2PhNMe2)2 ( 5 ) and dinuclear Pt cluster Pt2(μ-S)2(PPh3)4 ( 2 ) have comparable cytotoxicity to cisplatin against murine melanoma cell line B16F10. Masking of these discrete molecular entities within the hydrophobic core of Pluronic® F-127 significantly boosted their solubility and stability, ensuring efficient cellular uptake, giving in vitro IC50 values in the range of 0.87–11.23 μM. These results highlight the potential therapeutic value of Pt complexes featuring stable Pt−P bonds in nanocomposite formulations with biocompatible amphiphilic polymers.  相似文献   
96.
Background: Thiazole is a good pharmacophore nucleus due to its various pharmaceutical applications. Its derivatives have a wide range of biological activities such as antioxidant, analgesic, and antimicrobial including antibacterial, antifungal, antimalarial, anticancer, antiallergic, antihypertensive, anti-inflammatory, and antipsychotic. Indeed, the thiazole scaffold is contained in more than 18 FDA-approved drugs as well as in numerous experimental drugs. Objective: To summarize recent literature on the biological activities of thiazole ring-containing compounds Methods: A literature survey regarding the topics from the year 2015 up to now was carried out. Older publications were not included, since they were previously analyzed in available peer reviews. Results: Nearly 124 research articles were found, critically analyzed, and arranged regarding the synthesis and biological activities of thiazoles derivatives in the last 5 years.  相似文献   
97.
Alzheimer’s disease (AD) is one of the most common neurodegenerative diseases leading to dementia. Despite research efforts, currently there are no effective pharmacotherapeutic options for the prevention and treatment of AD. Recently, numerous studies highlighted the beneficial effects of curcumin (CUR), a natural polyphenol, in the neuroprotection. Especially, its dual antioxidant and anti-inflammatory properties attracted the interest of researchers. In fact, besides its antioxidant and anti-inflammatory properties, this biomolecule is not degraded in the intestinal tract. Additionally, CUR is able to cross the blood–brain barrier and could therefore to be used to treat neurodegenerative pathologies associated with oxidative stress, inflammation and apoptosis. The present study aimed to assess the ability of CUR to induce neuronal protective and/or recovery effects on a rat model of neurotoxicity induced by aluminum chloride (AlCl3), which mimics the sporadic form of Alzheimer’s disease. Our results showed that treatment with CUR enhances pro-oxidant levels, antioxidant enzymes activities and anti-inflammatory cytokine production and decreases apoptotic cells in AlCl3-exposed hippocampus rats. Additionally, histopathological analysis of hippocampus revealed the potential of CUR in decreasing the hallmarks in the AlCl3-induced AD. We also showed that CUR post-treatment significantly improved the behavioral, oxidative stress and inflammation in AlCl3-exposed rats. Taken together, our data presented CUR as a nutraceutical potential through its protective effects that are more interesting than recovery ones in sporadic model of AD.  相似文献   
98.
Conifers have long been recognized for their therapeutic potential in different disorders. Alkaloids, terpenes and polyphenols are the most abundant naturally occurring phytochemicals in these plants. Here, we provide an overview of the phytochemistry and related commercial products obtained from conifers. The pharmacological actions of different phytochemicals present in conifers against bacterial and fungal infections, cancer, diabetes and cardiovascular diseases are also reviewed. Data obtained from experimental and clinical studies performed to date clearly underline that such compounds exert promising antioxidant effects, being able to inhibit cell damage, cancer growth, inflammation and the onset of neurodegenerative diseases. Therefore, an attempt has been made with the intent to highlight the importance of conifer-derived extracts for pharmacological purposes, with the support of relevant in vitro and in vivo experimental data. In short, this review comprehends the information published to date related to conifers’ phytochemicals and illustrates their potential role as drugs.  相似文献   
99.
The purpose of this review is to present an overview of roadside drug testing, driving enforcement, and drunk/drug driving detection around the world. Drunk and drug driving is a severe problem, not only in the UAE, but also around the world. This has important implications for road safety as drunk or drug driving may increase the chances of a driver’s involvement in a road crash when compared to a drug-free driver. Recently, due to increases in drug-impaired drivers’ crash involvement, many mobile roadside drug testing devices have been introduced to the market. These devices use oral fluid, urine or blood matrices. These are on-the-spot tests, which are easy to use and are applied by law enforcement agencies and the public. Law enforcement agencies most commonly use oral fluid to detect the presence of illicit drugs in drivers. This review discusses all the available devices in the market used by the authorities. It also describes the type of drugs widely abused by drivers along with behavioral testing methods. The different types of matrices used for roadside drug testing are also evaluated. Sample collection, storage, and pre-treatment methods are discussed, followed by the confirmatory analysis of positive samples. This article will significantly help law enforcement agencies compare and evaluate all the reliable roadside testing devices and new emerging confirmatory devices available to them in the market. This will help them make an informed decision on which device to adapt to their individual needs.  相似文献   
100.
The medicinal potential and volatile composition of different parts of three cultivars of grapefruit (Citrus paradisi) were evaluated for their toxicity and anti-inflammatory activities. Fresh leaf and fruit peel were separately isolated by hydrodistillation for 4 h. The essential oils were subjected to GC/GC-MS analysis for chemical profile. Toxicity of the essential oils in mice were evaluated using Lorke’s method, while an anti-inflammatory assay was performed in a rat model using egg albumin-induced oedema. The oils obtained were light yellow in colour, and odour varied from strong citrus smell to mild. Percentage yield of fresh peel oil (0.34–0.57%) was greater than the fresh leaf oil yield (0.21–0.34%). D-limonene (86.70–89.90%) was the major compound identified in the leaf oil, while β-phellandrene (90.00–91.01%) dominated the peel oil. At a dosage level of 5000 mg/kg, none of the oils showed mortality in mice. An anti-inflammatory bioassay revealed that all the oils caused a significant (p < 0.05–0.01) reduction in oedema size when compared to the negative control group throughout the 5 h post induction assessment period. The study reveals that the oils are non-toxic and demonstrate significant anti-inflammatory activity. Our findings suggest that the leaf and peel oils obtained from waste parts of grapefruit plants can be useful as flavouring agents, as well as anti-inflammatory agents.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号