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   2992篇
  免费   349篇
  国内免费   14篇
耳鼻咽喉   39篇
儿科学   103篇
妇产科学   146篇
基础医学   318篇
口腔科学   88篇
临床医学   192篇
内科学   666篇
皮肤病学   172篇
神经病学   116篇
特种医学   170篇
外国民族医学   6篇
外科学   507篇
综合类   54篇
预防医学   210篇
眼科学   39篇
药学   295篇
中国医学   18篇
肿瘤学   216篇
  2023年   11篇
  2022年   66篇
  2021年   122篇
  2020年   89篇
  2019年   157篇
  2018年   172篇
  2017年   138篇
  2016年   134篇
  2015年   157篇
  2014年   176篇
  2013年   207篇
  2012年   223篇
  2011年   228篇
  2010年   155篇
  2009年   135篇
  2008年   106篇
  2007年   119篇
  2006年   109篇
  2005年   111篇
  2004年   93篇
  2003年   85篇
  2002年   82篇
  2001年   20篇
  2000年   19篇
  1999年   29篇
  1998年   16篇
  1997年   16篇
  1996年   18篇
  1995年   13篇
  1994年   10篇
  1993年   12篇
  1992年   29篇
  1991年   14篇
  1990年   16篇
  1988年   20篇
  1987年   19篇
  1986年   14篇
  1985年   22篇
  1984年   11篇
  1982年   11篇
  1980年   11篇
  1979年   16篇
  1978年   10篇
  1977年   8篇
  1976年   10篇
  1971年   11篇
  1970年   10篇
  1969年   9篇
  1968年   7篇
  1967年   12篇
排序方式: 共有3355条查询结果,搜索用时 593 毫秒
71.
Objectives:To set age-specific normal reference values for brainstem, cerebellar vermis, and peduncles measurements and characterize values’ variations according to gender, age, and age by gender interaction.Methods:565 normal brain magnetic resonance examinations with normal anatomy and signal intensity of the supra- and infratentorial structures were categorized into six age groups (infant, child, adolescent, young adult, middle-age adult, and old aged adults). Patients with congenital malformations, gross pathology of the supra- or infratentorial brain, brain volume loss, developmental delay, metabolic disorders, and neuropsychological disorders (n = 2.839) were excluded. On midsagittal T1 weighted and axial T2 weighted images specific linear diameters and ratios of the brainstem, cerebellar vermis, and peduncles were attained. Two observers assessed a random sample of 100 subjects to evaluate the inter- and intraobserver reproducibility. Intraclass correlation coefficients, means ± standard deviation, one and two-way analysis of variance tests were used in the statistical analysis.Results:Good to excellent inter- and intraobserver measurements’ reproducibility were observed, except for the transverse diameter of the midbrain, the anteroposterior diameter of the medulla oblongata at the pontomedullary and cervicomedullary junctions, cerebellar vermis anteroposterior diameter, and thickness of the superior cerebellar peduncle. Age-specific mean values of the investigated measurements were established. A significant gender-related variation was recorded in the anteroposterior diameter of the basis pontis (p = 0.044), the anteroposterior diameter of the medulla oblongata at the cervicomedullary junction (p = 0.044), and cerebellar vermis height (p = 0.018). A significant age-related change was detected in all measurements except the tectal ratio. Age by gender interaction had a statistically significant effect on the tectal ratio, inferior, and middle cerebellar peduncles’ thickness (p = 0.001, 0.022, and 0.028, respectively).Conclusion:This study provides age-specific normal mean values for various linear dimensions and ratios of the posterior fossa structures with documentation of measurements’ variability according to gender, age, and their interaction.Advances in knowledge:It provides a valuable reference in the clinical practice for easier differentiation between physiological and pathological conditions of the posterior fossa structures especially various neurodegenerative diseases and congenital anomalies.  相似文献   
72.
Natural use of language involves at least two individuals. Some studies have focused on the interaction between senders in communicative situations and how the knowledge about the speaker can bias language comprehension. However, the mere effect of a face as a social context on language processing remains unknown. In the present study, we used event-related potentials to investigate the semantic and morphosyntactic processing of speech in the presence of a photographic portrait of the speaker. In Experiment 1, we show that the N400, a component related to semantic comprehension, increased its amplitude when processed within this minimal social context compared to a scrambled face control condition. Hence, the semantic neural processing of speech is sensitive to the concomitant perception of a picture of the speaker’s face, even if irrelevant to the content of the sentences. Moreover, a late posterior negativity effect was found to the presentation of the speaker’s face compared to control stimuli. In contrast, in Experiment 2, we found that morphosyntactic processing, as reflected in left anterior negativity and P600 effects, is not notably affected by the presence of the speaker’s portrait. Overall, the present findings suggest that the mere presence of the speaker’s image seems to trigger a minimal communicative context, increasing processing resources for language comprehension at the semantic level.  相似文献   
73.
74.
A simple, cost-effective and green mucilage-capped silver nanoparticles (Mucilage-AgNPs) modified glassy carbon electrode (GC) composite was constructed for efficient and facile electrochemical oxidation of glucose for the first time. Mucilage-AgNPs were synthesized through the direct chemical reduction of Ag+ by mucilage extracted from Opuntia ficus-indica. Mucilage-AgNPs were identified and characterized using ultraviolet-visible spectroscopy, transmission electron microscopy and square wave voltammetry. Modification of the GC with AgNPs was carried out via a transfer-sticking technique with an immobilization time of 1 h. The Mucilage-AgNPs/GC composite was studied as a possible anode for glucose oxidation in a biofuel cell. The composite resulted in glucose oxidation with a current density and power density of 85.7 μA cm−2 and 25.7 μW cm−2, respectively. Glucose sensing using the Mucilage-AgNPs/GC composite was achieved successfully via two pathways: glucose oxidation and AgNP inhibition. The glucose oxidation-based sensor showed a lower detection limit of 0.01 mM and a linear range of 0.01 to 2.2 mM. The AgNPs inhibition-based sensor provides an indirect determination pathway of glucose with a detection limit of 0.1 mM and a linear range of 0.1 to 1.9 mM. AgNP inhibition is a novel pathway that could be used for determining a large number of organic and inorganic molecules. Overall, the Mucilage-AgNPs/GC is considered a pioneering composite for glucose sensing and fuel cell applications.

A simple, cost-effective and green mucilage-capped silver nanoparticles (Mucilage-AgNPs) modified glassy carbon electrode (GC) composite was constructed for efficient and facile electrochemical oxidation of glucose for the first time.  相似文献   
75.
This study was carried out to evaluate the protective effects of Panax ginseng aqueous extract (GAE) against hepatorenal toxicity induced by lambda‐cyhalothrin‐acetamiprid insecticide mixture in rats. A total of 32 male albino rats were assigned into four groups. Normal control group received distilled water. Insecticide control group intoxicated with the insecticide at a dose of 2.14 mg/kg b.wt orally day after day for 45 days. GAE control group was treated with GAE at a dose 200 mg/kg b.wt orally. GAE experimental group was administered GAE 1 hour before insecticide administration. Intoxication of rats with the insecticide caused a significant increase in serum aspartate aminotransferase and alanine aminotransferase activities and urea and creatinine levels as well as malondialdehyde concentration and proteins expression of caspase‐3 and induced nitric oxide synthase in hepatic and renal tissues. However, it decreased the serum levels of total protein and globulin and reduced the glutathione content and catalase activity in hepatic and renal tissues. In addition, insecticide induced histopathological alterations in both hepatic and renal tissues. In contrast, GAE modulated insecticide‐induced alterations in liver and kidney functions and structures as it ameliorated the effects of insecticide on the above mentioned parameters. These results indicated that GAE was a potent antioxidant agent that could protect rats against insecticide‐induced hepatorenal toxicity.  相似文献   
76.
77.
78.
79.
The efficacy of a novel curcumin derivative (NCD) versus tadalafil in erectile signalling was assessed. Ten control male rats and 50 diabetic male rats were used and divided into the following: diabetic (DM), curcumin (CURC), NCD, tadalafil and NCD combined with tadalafil rat groups. Cavernous tissue gene expression of heme oxygenase‐1 (HO‐1), Nrf2, NFB and p38, enzyme activities of heme oxygenase (HO) and nitric oxide synthase (NOS), cGMP and intracavernosal pressure (ICP)/mean arterial pressure (MAP) were assessed. Results showed that 12 weeks after induction of diabetes, erectile dysfunction (ED) was confirmed by the significant decrease in ICP/MAP, a significant decrease in cGMP, NOS, HO enzyme activities, a significant decrease in HO‐1 gene and a significant increase in NF‐?β, p38 genes. Administration of all therapeutic interventions led to a significant increase in ICP/MAP, cGMP levels, a significant increase in HO‐1 and NOS enzymes, a significant increase in HO‐1, and Nrf2 gene expression, and a significant decrease in NF‐?β, p38 gene expression. NCD or its combination with tadalafil showed significant superiority and more prolonged duration of action. In conclusion, a tendency was observed that CURC and NCD have high efficacy and more prolonged duration of action in enhancing erectile function.  相似文献   
80.
We developed a novel integrative genomic tool called GRANITE (Genetic Regulatory Analysis of Networks Investigational Tool Environment) that can effectively analyze large complex data sets to generate interactive networks. GRANITE is an open-source tool and invaluable resource for a variety of genomic fields. Although our analysis is confined to static expression data, GRANITE has the capability of evaluating time-course data and generating interactive networks that may shed light on acute versus chronic treatment, as well as evaluating dose response and providing insight into mechanisms that underlie therapeutic versus sub-therapeutic doses or toxic doses. As a proof-of-concept study, we investigated lithium (Li) response in bipolar disorder (BD). BD is a severe mood disorder marked by cycles of mania and depression. Li is one of the most commonly prescribed and decidedly effective treatments for many patients (responders), although its mode of action is not yet fully understood, nor is it effective in every patient (non-responders). In an in vitro study, we compared vehicle versus chronic Li treatment in patient-derived lymphoblastoid cells (LCLs) (derived from either responders or non-responders) using both microRNA (miRNA) and messenger RNA gene expression profiling. We present both Li responder and non-responder network visualizations created by our GRANITE analysis in BD. We identified by network visualization that the Let-7 family is consistently downregulated by Li in both groups where this miRNA family has been implicated in neurodegeneration, cell survival and synaptic development. We discuss the potential of this analysis for investigating treatment response and even providing clinicians with a tool for predicting treatment response in their patients, as well as for providing the industry with a tool for identifying network nodes as targets for novel drug discovery.  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