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   26926篇
  免费   1494篇
  国内免费   147篇
耳鼻咽喉   295篇
儿科学   522篇
妇产科学   579篇
基础医学   3499篇
口腔科学   1394篇
临床医学   2082篇
内科学   7018篇
皮肤病学   720篇
神经病学   2284篇
特种医学   449篇
外科学   3717篇
综合类   132篇
一般理论   6篇
预防医学   2265篇
眼科学   509篇
药学   1626篇
中国医学   139篇
肿瘤学   1331篇
  2024年   19篇
  2023年   225篇
  2022年   517篇
  2021年   1080篇
  2020年   588篇
  2019年   922篇
  2018年   1130篇
  2017年   650篇
  2016年   641篇
  2015年   858篇
  2014年   1216篇
  2013年   1411篇
  2012年   2248篇
  2011年   2432篇
  2010年   1262篇
  2009年   1190篇
  2008年   1787篇
  2007年   1834篇
  2006年   1706篇
  2005年   1524篇
  2004年   1343篇
  2003年   1169篇
  2002年   1123篇
  2001年   128篇
  2000年   113篇
  1999年   127篇
  1998年   175篇
  1997年   162篇
  1996年   118篇
  1995年   97篇
  1994年   75篇
  1993年   84篇
  1992年   55篇
  1991年   52篇
  1990年   45篇
  1989年   26篇
  1988年   20篇
  1987年   16篇
  1986年   29篇
  1985年   30篇
  1984年   31篇
  1983年   27篇
  1982年   36篇
  1981年   41篇
  1980年   18篇
  1979年   23篇
  1978年   15篇
  1976年   12篇
  1974年   16篇
  1971年   13篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
991.
The aim of the present study was to determine the percentage of dentists who use radiographic examination on the initial appointment, and establish the relation between the use of periodontal probe and graduation year. Dentists were interviewed in their private offices in three cities in Rio Grande do Sul. They were asked about the routine use of radiographic examination and, if applicable, what technique was applied and what clinical instrument was used at the first appointment. Opened and closed questions were included in the interview and for some of them more than one answer was possible. A significant number of dentists (62.9%) reported some kind of radiographic examination at the initial appointment. Among the radiographic techniques, the periapical was the most cited (74.3%), followed by the panoramic (36.2%) and bite-wing (32.9%) techniques. There was an association between the use of periodontal probe and the use of radiographic examination at the initial appointment. Dentists who used periodontal probe used radiographic examination more frequently (p=0.010). More recently graduated dentists (1991-2005) used radiographic examination more than the others (p=0.022). In conclusion, a large number of dentists reported the use of radiographic examination at the initial appointment. There was an association between the use of this examination technique and the use of the periodontal probe; recently graduated dentists used radiographic examinations more frequently than the others.  相似文献   
992.
The hydrolytic stability of composite repairs is a desirable property. In the present study, the composite repair microtensile bond strength, failure mode distribution, and nanoleakage occurrence before and after thermocycling were evaluated. Standardized, 1-month-old composite substrates were roughened, cleaned, and randomly assigned to seven groups according to the intermediate agent applied. Resin-based, silane-based, and combined silane/adhesive coupling agents were investigated. The same resin composite as the substrate was used for repair. For each group, repaired samples were wet stored for 24 h (37 degrees C) or thermocycled (5,000 cycles, 5-55 degrees C). Failure mode and silver nitrate penetration were examined by stereomicroscopy. Intermediate agent, experimental condition, and their interaction were significant factors. Hydrophobic flowable composites resulted in statistically higher repair strengths, lower occurrence of adhesive failures, and good quality interfacial coupling without any silver uptake in both conditions. Light-curing, hydrophilic resin monomer-based intermediate agents, although not affected by thermocycling, showed a more pronounced silver penetration. The composite repair strength of a self-curing silane/adhesive agent was significantly affected by thermal stresses, despite the absence of silver uptake. A prehydrolized silane agent recorded the lowest repair strength, with minimal or no evidence of interfacial silver impregnation after thermocycling. In conclusion, flowability and hydrophobic nature can be considered important properties when selecting intermediate agents for composite repair.  相似文献   
993.
994.
OBJECTIVE: To describe the ritual and ethnobotanical treatments about migraine performed by shamans from several native cultures. METHODS: Anthropological field study conducted with Tzeltal Maya (Mexico), Kamayurá (Brazil), and Uru-Chipaya (Bolivia) American Indians. RESULTS: Migraine is called yaxti-wanjol chawaj by Tzeltal shamans. They wash the head of the patient with an herbal solution to treat headache. The boiled leaves of a shrub called payté wamal (Tagetes nelsonii) are used to relieve migraine. Migraine is called monkey's disease by Kamayurá natives. The disease is originated by the revenge of the killed monkey's spirit, striking to Kamayurá hunter on his head. It is treated with an herbal infusion applied in the eyes of the patient. Migraine is called eskeclamix by Chipaya people, and is treated by drinking the ca?ahua plant (Chenopodium palludicale) boiled with water. The patient's head may also be washed with shaman's fermented urine. CONCLUSIONS: Cultural equivalents of migraine exist in the healing system of isolated American cultures.  相似文献   
995.
996.
997.
998.

Background

The aim of this study was to investigate this involvement in not inflammatory model of pain and which opioid receptor subtype mediates noradrenaline-induced peripheral antinociception. Noradrenaline is involved in the intrinsic control of pain-inducing pro-nociceptive effects in the primary afferent nociceptors. However, inflammation can induce various plastic changes in the central and peripheral noradrenergic system that, upon interaction with the immune system, may contribute, in part, to peripheral antinociception.

Methods

Hyperalgesia was induced by intraplantar injection of prostaglandin E2 (PGE2, 2 μg) into the plantar surface of the right hind paw and the paw pressure test to evaluated the hyperalgesia was used. Noradrenaline (NA) was administered locally into right hind paw of Wistar rat (160–200 g) alone and after either agents, α2-adrenoceptor antagonist yohimbine, α1-adrenoceptor antagonist prazosin, β-adrenoceptor antagonist propranolol, μ-opioid antagonist clocinnamox, δ-opioid antagonist naltrindole and κ-opioid antagonist nor-binaltorfimina. In addition, the enkephalinase inhibitor bestatin was administered prior to NA low dose.

Results

Intraplantar injection of NA induced peripheral antinociception against hyperalgesia induced by PGE2. This effect was reversed, in dose dependent manner, by intraplantar injection of yohimbine, prazosin, propranolol, clocinnamox and naltrindole. However, injection of nor-binaltorfimina did not alter antinociception of NA after PGE2 hyperalgesia. Bestatin intensified the antinociceptive effects of low-dose of NA.

Conclusion

Besides the α2-adrenoceptor, the present data provide evidence that, in absence of inflammation, NA activating α1 and β-adrenoceptor induce endogenous opioid release to produce peripheral antinociceptive effect by μ and δ opioid receptors.  相似文献   
999.
Although multiple studies have reported the toxicological effects and underlying mechanisms of toxicity of silver nanoparticles (AgNP) in a variety of organisms, the interactions of AgNP with environmental contaminants such as cadmium are poorly understood. We used biochemical assays and mass spectrometry-based proteomics to assess the cellular and molecular effects induced by a co-exposure of HepG2 cells to AgNP and cadmium. Cell viability and energy homeostasis were slightly affected after a 4-h exposure to AgNP, cadmium, or a combination of the two; these endpoints were substantially altered after a 24-h co-exposure to AgNP and cadmium, while exposure to one of the two contaminants led only to minor changes. Proteomics analysis followed the same trend: while a 4-h exposure induced minor protein deregulation, a 24-h exposure to a combination of AgNP and cadmium deregulated 43% of the proteome. The toxicity induced by a combined exposure to AgNP and cadmium involved (1) inactivation of Nrf2, resulting in downregulation of antioxidant defense and proteasome-related proteins, (2) metabolic adaptation and ADP/ATP imbalance, and (3) increased protein synthesis possibly to reestablish homeostasis. The adaptation strategy was not sufficient to restore ADP/ATP homeostasis and to avoid cell death.  相似文献   
1000.
Background Spending on biological agents has risen dramatically due to the high cost of the drugs and the increased prevalence of spondyloarthritis. Objective To evaluate the annual cost per patient and cost for each biological drug for treating patients with spondyloarthritis from 2009 to 2016, and to calculate factors that affect treatment cost, such as optimizing therapies by monitoring drug serum levels, the use of biosimilar-TNF inhibitors, and official discounts or negotiated rebates in biologicals acquired by the pharmacy department. Method Retrospective, observational study in a Spanish tertiary hospital. Main outcome Annual cost per patient and per drug. Factors that influenced the costs and socio-demographic parameters and disease activity. Results A total of 129, 215, and 224 patients were treated in 2009, 2013, and 2016, respectively. The annual cost per patient decreased: EUR11,604 in 2009, EUR8513 in 2013, and EUR7464 in 2016. The introduction of new drugs drives economic competition, leading to total savings per drug, with discounts reaching 5.8, 12.4, 16.7, 17.7, 13.7, and 24.8% for original infliximab, etanercept, adalimumab, ertolizumab, golimumab, and secukinumab, respectively, while rebates for biosimilar infliximab reached 31.90% in 2016. The number of patients with optimized therapies reached 47.5% in 2016, which led to cost savings of EUR798,614, in addition to savings from official discounts and rebates of EUR252,706 and savings from optimized therapies of EUR545,908 in 2016. Conclusion The cost of biological treatments declined after official discounts, negotiated rebates, and optimized therapies, leading to a significant decrease in the annual cost per patient. The greatest contribution to economic savings in biological therapy according to our study was biological therapy optimization.  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