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   27838篇
  免费   4643篇
  国内免费   2923篇
化学   18468篇
晶体学   267篇
力学   1923篇
综合类   217篇
数学   3432篇
物理学   11097篇
  2024年   106篇
  2023年   592篇
  2022年   1068篇
  2021年   1102篇
  2020年   1105篇
  2019年   1042篇
  2018年   974篇
  2017年   922篇
  2016年   1347篇
  2015年   1307篇
  2014年   1541篇
  2013年   2067篇
  2012年   2436篇
  2011年   2458篇
  2010年   1649篇
  2009年   1613篇
  2008年   1763篇
  2007年   1521篇
  2006年   1382篇
  2005年   1167篇
  2004年   879篇
  2003年   695篇
  2002年   628篇
  2001年   518篇
  2000年   522篇
  1999年   635篇
  1998年   528篇
  1997年   524篇
  1996年   488篇
  1995年   464篇
  1994年   386篇
  1993年   345篇
  1992年   285篇
  1991年   252篇
  1990年   238篇
  1989年   186篇
  1988年   145篇
  1987年   124篇
  1986年   93篇
  1985年   94篇
  1984年   63篇
  1983年   50篇
  1982年   52篇
  1981年   22篇
  1980年   12篇
  1979年   4篇
  1976年   1篇
  1959年   1篇
  1957年   7篇
  1936年   1篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
The lack of effective treatment for neurological disorders has encouraged the search for novel therapeutic strategies. Remarkably, neuroinflammation provoked by the activated microglia is emerging as an important therapeutic target for neurological dysfunction in the central nervous system. In the pathological context, the hyperactivation of microglia leads to neuroinflammation through the release of neurotoxic molecules, such as reactive oxygen species, proteinases, proinflammatory cytokines and chemokines. Cannabidiol (CBD) is a major pharmacologically active phytocannabinoids derived from Cannabis sativa L. CBD has promising therapeutic effects based on mounting clinical and preclinical studies of neurological disorders, such as epilepsy, multiple sclerosis, ischemic brain injuries, neuropathic pain, schizophrenia and Alzheimer’s disease. A number of preclinical studies suggested that CBD exhibited potent inhibitory effects of neurotoxic molecules and inflammatory modulators, highlighting its remarkable therapeutic potential for the treatment of numerous neurological disorders. However, the molecular mechanisms of action underpinning CBD’s effects on neuroinflammation appear to be complex and are poorly understood. This review summarises the anti-neuroinflammatory activities of CBD against various neurological disorders with a particular focus on their main molecular mechanisms of action, which were related to the downregulation of NADPH oxidase-mediated ROS, TLR4-NFκB and IFN-β-JAK-STAT pathways. We also illustrate the pharmacological action of CBD’s derivatives focusing on their anti-neuroinflammatory and neuroprotective effects for neurological disorders. We included the studies that demonstrated synergistic enhanced anti-neuroinflammatory activity using CBD and other biomolecules. The studies that are summarised in the review shed light on the development of CBD, including its derivatives and combination preparations as novel therapeutic options for the prevention and/or treatment of neurological disorders where neuroinflammation plays an important role in the pathological components.  相似文献   
92.
Lycium barbarum leaves are a kind of vegetable, and modern nutrition studies have found that they have an anti-aging function. Our study aims to investigate the anti-aging effects of Lycium barbarum leaf flavonoid (LBLF) extracts and its underlying molecular mechanism. LBLFs were purified using D101 and polyamide resin, characterized by ultraperformance liquid chromatography coupled with mass spectrometry, and administered to hydrogen peroxide (H2O2)-treated human umbilical vein endothelial cells (HUVECs) and Caenorhabditis elegans. Appropriate enrichment conditions were optimized through dynamic adsorption and desorption experiments, the content of flavonoids reached 909.84 mg/g, rutin and kaempferol being the main ones. LBLFs attenuated H2O2-induced HUVEC apoptosis, decreased reactive oxygen species and malondialdehyde production levels, increased superoxide dismutase, glutathione peroxidase and catalase activities. Furthermore, pre-treatment with LBLF increased mRNA expression of erythropoietin (EPO) and heme oxygenase-1 (HO-1) via the mitogen-activated protein kinase (MAPK) signaling pathway in HUVECs. Compared with 100 µM rutin monomer, LBLF prolonged the lifespan of Caenorhabditis elegans, enhanced their mobility in middle life stages and upregulated expression of sod-2, gcs-1 and skn-1 genes, which indicated that the anti-aging effects of LBLF were due to its redox-modulation.  相似文献   
93.
Pandemic and epidemic spread of antibiotic-resistant bacterial infections would result in a huge number of fatalities globally. To combat antibiotic-resistant pathogens, new antimicrobial strategies should be explored and developed to confront bacteria without acquiring or increasing drug-resistance. Here, oxygen saturated perfluorohexane (PFH)-loaded mesoporous carbon nanoparticles (CIL@ICG/PFH@O2) with photothermal therapy (PTT) and enhanced photodynamic therapy (PDT) utility are developed for antibacterial applications. Ionic liquid groups are grafted onto the surface of mesoporous carbon nanoparticles, followed by anion-exchange with the anionic photosensitizer indocyanine green (ICG) and loading oxygen saturated PFH to prepare CIL@ICG/PFH@O2. These CIL@ICG/PFH@O2 nanoparticles exhibit effective PTT and enhanced PDT properties simultaneously upon 808 nm light irradiation. In vitro assays demonstrate that CIL@ICG/PFH@O2 shows a synergistic antibacterial action against antibiotic-resistant pathogens (methicillin-resistant Staphylococcus aureus and kanamycin-resistant Escherichia coli). Moreover, CIL@ICG/PFH@O2 could effectively kill drug-resistant bacteria in vivo to relieve inflammation and eliminate methicillin-resistant Staphylococcus aureus-wound infection under NIR irradiation, and the released oxygen can increase collagen deposition, epithelial tissue formation and blood vessel formation to promote wound healing while enhancing the PDT effect. This study proposes a platform with enhanced PTT/PDT effects for effective, controlled, and precise treatment of topical drug-resistant bacterial infections.

We report oxygen saturated perfluorohexane (PFH)-loaded mesoporous carbon nanoparticles (CIL@ICG/PFH@O2) with photothermal therapy (PTT) and enhanced photodynamic therapy (PDT) utility for antibacterial applications.  相似文献   
94.
A formal[4+3]-cycloaddition reaction of ortho-hydroxyphenyl-substituted para-quinone methides(p-QMs)with in-situ generated azaoxyallyl cations is reported.The reaction occurs under very mild reaction conditions(transition-metal free,room temperature,cheap inorganic base)and provides a very efficient route to a series of biologically important 1,4-benzoxazepine derivatives in good to excellent yields.  相似文献   
95.
Cancer progression is linked to aberrant protein glycosylation due to the overexpression of several glycosylation enzymes. These enzymes are underexploited as potential anticancer drug targets and the development of rapid-screening methods and identification of glycosylation inhibitors are highly sought. An integrated bioinformatics and mass spectrometry-based glycomics-driven glycoproteomics analysis pipeline was performed to identify an N-glycan inhibitor against lung cancer cells. Combined network pharmacology and in silico screening approaches were used to identify a potential inhibitor, pictilisib, against several glycosylation-related proteins, such as Alpha1-6FucT, GlcNAcT-V, and Alpha2,6-ST-I. A glycomics assay of lung cancer cells treated with pictilisib showed a significant reduction in the fucosylation and sialylation of N-glycans, with an increase in high mannose-type glycans. Proteomics analysis and in vitro assays also showed significant upregulation of the proteins involved in apoptosis and cell adhesion, and the downregulation of proteins involved in cell cycle regulation, mRNA processing, and protein translation. Site-specific glycoproteomics analysis further showed that glycoproteins with reduced fucosylation and sialylation were involved in apoptosis, cell adhesion, DNA damage repair, and chemical response processes. To determine how the alterations in N-glycosylation impact glycoprotein dynamics, modeling of changes in glycan interactions of the ITGA5–ITGB1 (Integrin alpha 5-Integrin beta-1) complex revealed specific glycosites at the interface of these proteins that, when highly fucosylated and sialylated, such as in untreated A549 cells, form greater hydrogen bonding interactions compared to the high mannose-types in pictilisib-treated A549 cells. This study highlights the use of mass spectrometry to identify a potential glycosylation inhibitor and assessment of its impact on cell surface glycoprotein abundance and protein–protein interaction.  相似文献   
96.
To develop new compounds with high activity, broad spectrum and low-toxicity, 17 benzamides substituted with quinoline-linked 1,2,4-oxadiazole were designed using the splicing principle of active substructures and were synthesized. The biological activities were evaluated against 10 fungi, indicating that some of the synthetic compounds showed excellent fungicidal activities. For example, at 50 mg/L, the inhibitory activity of 13p (3-Cl-4-Cl substituted, 86.1%) against Sclerotinia sclerotiorum was superior to that of quinoxyfen (77.8%), and the inhibitory activity of 13f (3-CF3 substituted, 77.8%) was comparable to that of quinoxyfen. The fungicidal activities of 13f and 13p to Sclerotinia sclerotiorum were better than that of quinoxyfen (14.19 mg/L), with EC50 of 6.67 mg/L and 5.17 mg/L, respectively. Furthermore, the acute toxicity of 13p was 19.42 mg/L, classifying it as a low-toxic compound.  相似文献   
97.
The strength properties of green sinter beds,including the Young's modulus and maximum bed strain,were evaluated using uniaxial compression tests.The green-sint...  相似文献   
98.
Mesoscale structures that form in gas-solid flows considerably affect interphase heat transfer.A filtered interphase heat transfer model accounts for the effect...  相似文献   
99.
The traditional method for the determination of protein in food needs the operations of digestion, distillation, absorption, and titration; therefore, it is complicated and time-consuming and requires professional personnel. Is there a more convenient and faster detection method that can directly determine the ammonium ions in protein digestion solution to obtain the protein content of food and avoid the distillation–absorption–titration process? The feasibility of water ammonium ion test kits for food protein rapid detection was discussed here. After digestion, the protein in food transforms into ammonium ions in the digestion solution. Because of the variety of food, there are many different inorganic ions left in the food digestion solution, and at the same time, digestion agents are added in the digestion process and become potential interference factors in ammonium determination. Therefore, the detection accuracy of ammonium test kits needs to be evaluated first, including their anti-interference ability. The standard curve of ammonium was established by the test kit. When the ammonium concentration was 0.00–2.50 mg/L, the absorbance at 620 nm was linearly related to the ammonium concentration, the determination coefficient R2 was 0.9995, and the detection limit of this method was 0.01 mg/L. The influences of temperature, pH value, and reaction time on the test kit method were discussed. The precision was 0.90–3.33%; the repeatability was 1.71–4.86%; and the recovery rate of tap water, river water, and sea water was controlled within 90–103%. The anti-interference ability of the evaluated test kit was better than that of the national standard detection method. The test kit, combined with sample pretreatment and protein conversion formula, was used to detect protein in different types of food (milk powder, rice flour, wheat flour, soy, banana, milk, fish food, chicken food, and dog food). The results showed that there were no significant differences (ρ > 0.05) between the national method and the test kit method. The ammonium ion test kit method shortened the determination time and had higher sensitivity, showing its potential for the rapid determination of food protein.  相似文献   
100.
We give here an overview of the orbital-free density functional theory that is used for modeling atoms and molecules.We review typical approximations to the kinetic energy,exchange-correlation corrections to the kinetic and Hartree energies, and constructions of the pseudopotentials.We discuss numerical discretizations for the orbital-free methods and include several numerical results for illustrations.  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