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   19221篇
  免费   1826篇
  国内免费   339篇
耳鼻咽喉   102篇
儿科学   1002篇
妇产科学   139篇
基础医学   2576篇
口腔科学   1602篇
临床医学   1234篇
内科学   1957篇
皮肤病学   272篇
神经病学   659篇
特种医学   298篇
外国民族医学   2篇
外科学   1449篇
综合类   1516篇
现状与发展   1篇
一般理论   1篇
预防医学   5600篇
眼科学   63篇
药学   1618篇
  12篇
中国医学   482篇
肿瘤学   801篇
  2024年   44篇
  2023年   310篇
  2022年   1121篇
  2021年   1437篇
  2020年   838篇
  2019年   785篇
  2018年   736篇
  2017年   712篇
  2016年   745篇
  2015年   826篇
  2014年   1179篇
  2013年   1607篇
  2012年   973篇
  2011年   1069篇
  2010年   831篇
  2009年   805篇
  2008年   865篇
  2007年   798篇
  2006年   661篇
  2005年   591篇
  2004年   487篇
  2003年   473篇
  2002年   409篇
  2001年   330篇
  2000年   275篇
  1999年   247篇
  1998年   227篇
  1997年   222篇
  1996年   193篇
  1995年   173篇
  1994年   185篇
  1993年   108篇
  1992年   139篇
  1991年   116篇
  1990年   91篇
  1989年   81篇
  1988年   84篇
  1987年   73篇
  1986年   74篇
  1985年   86篇
  1984年   58篇
  1983年   59篇
  1982年   50篇
  1981年   43篇
  1980年   35篇
  1979年   31篇
  1978年   34篇
  1977年   16篇
  1976年   20篇
  1975年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
BackgroundVoices for Food was a longitudinal community, food pantry–based intervention informed by the social ecological model, and designed to improve food security, dietary intake, and quality among clients, which was carried out in 24 rural food pantries across 6 Midwestern states.ObjectiveOur objective was to evaluate changes in adult food security, dietary intake, and quality from baseline (2014) to follow-up (2016), and to assess the role of adult food security on dietary outcomes.DesignA multistate, longitudinal, quasi-experimental intervention with matched treatment and comparison design was used to evaluate treatment vs comparison group changes over time and changes in both groups over time.Participants/settingAdult food pantry clients (n = 617) completed a demographic food security survey, and up to three 24-hour dietary recalls at baseline (n = 590) and follow-up (n = 160).InterventionCommunity coaching served as the experimental component, which only “treatment” communities received, and a food council guide and food pantry toolkit were provided to both “treatment” and matched “comparison” communities.Main outcome measuresChange in adult food security status, mean usual intakes of nutrients and food groups, and Healthy Eating Index-2010 scores were the main outcome measures.Statistical analyses performedLinear mixed models estimated changes in outcomes by intervention group and by adult food security status over time.ResultsImprovements in adult food security score (–0.7 ± 0.3; P = .01), Healthy Eating Index-2010 total score (4.2 ± 1.1; P < .0001), and empty calories component score (3.4 ± 0.5; P <.0001) from baseline to follow-up were observed in treatment and comparison groups, but no statistically significant changes were found for adult food security status, dietary quality, and usual intakes of nutrients and food groups between the 2 groups over time. The intervention effect on dietary quality and usual intake changes over time by adult food security status were also not observed.ConclusionsFood pantry clients in treatment and comparison groups had higher food security and dietary quality at the follow-up evaluation of the Voices for Food intervention trial compared with baseline, despite the lack of difference among the groups as a result of the experimental coaching component.  相似文献   
2.
3.
4.
5.
6.
Many nanoparticles (NPs) have toxic effects on multiple cell lines. This toxicity is assumed to be related to their accumulation within cells. However, the process of internalization of NPs has not yet been fully characterized. In this study, the cellular uptake, accumulation, and localization of titanium dioxide nanoparticles (TiO2 NPs) in rat (C6) and human (U373) glial cells were analyzed using time-lapse microscopy (TLM) and transmission electron microscopy (TEM). Cytochalasin D (Cyt-D) was used to evaluate whether the internalization process depends of actin reorganization. To determine whether the NP uptake is mediated by phagocytosis or macropinocytosis, nitroblue tetrazolium (NBT) reduction was measured and the 5-(N-ethyl-N-isopropyl)-amiloride was used. Expression of proteins involved with endocytosis and exocytosis such as caveolin-1 (Cav-1) and cysteine string proteins (CSPs) was also determined using flow cytometry.TiO2 NPs were taken up by both cell types, were bound to cellular membranes and were internalized at very short times after exposure (C6, 30 min; U373, 2 h). During the uptake process, the formation of pseudopodia and intracellular vesicles was observed, indicating that this process was mediated by endocytosis. No specific localization of TiO2 NPs into particular organelles was found: in contrast, they were primarily localized into large vesicles in the cytoplasm. Internalization of TiO2 NPs was strongly inhibited by Cyt-D in both cells and by amiloride in U373 cells; besides, the observed endocytosis was not associated with NBT reduction in either cell type, indicating that macropinocytosis is the main process of internalization in U373 cells. In addition, increases in the expression of Cav-1 protein and CSPs were observed.In conclusion, glial cells are able to internalize TiO2 NPs by a constitutive endocytic mechanism which may be associated with their strong cytotoxic effect in these cells; therefore, TiO2 NPs internalization and their accumulation in brain cells could be dangerous to human health.  相似文献   
7.
BackgroundGrowth hormone (GH)-producing pituitary tumors account for 10 to 15% of pituitary tumors. The hypersecretion of GH may induce changes in the airway anatomy through the activation of Insulin-like Growth factor 1(IGF-1) pathway. We sought investigate the role IGF-1 as a potential predictive factor of difficult laryngoscopy in patients with GH-producing pituitary adenoma.MethodsThis study was a single center retrospective study. We included 33 patients undergoing transsphenoidal resection of GH-producing pituitary. We recorded demographic data, el-Ganzouri risk index (EGRI) and modified Look-Evaluate-Mallampati-Obstruction-Neck mobility (mLEMON) score, and pituitary hormone plasma levels. We performed ordinal logistic regression to analyze the relationship between IGF-1 and EGRI, mLEMON, and Cormack-Lehane Grade score and a multiple logistic regression to test the capability of EGRI, mLEMON and IGF-1 levels to predict Cormack-Lehane score. Receiver operating curve (ROC), area under the curve (AUC), and cut-off value of IGF-1 were calculated.ResultsOnly 14 (42.8%) and 12 (36.36%) patients showed predictive factors of difficult intubation according to EGRI and mLEMON score, respectively. IGF-1 significantly correlated with Cormack-Lehane (p = 0.005879) but not with mLEMON and EGRI (p = 0.3080 and 0.4146, respectively). In multiple regression model IGF-1 correlated only with Cormack-Lehane grade (p = 0.0089). Area under ROC was 0.8571 and cut-off value of IGF-1 was 186.15 ng/ml.ConclusionHigher IGF-1 levels correlate with the probability of having a higher Cormack-Lehane score; classical bedside scores, such as mLEMON and EGRI, were not able to predict difficult laryngoscopy in our population.  相似文献   
8.
Titanium osteosynthesis is currently the fixation system of choice in maxillofacial traumatology. Biodegradable osteosynthesis systems have the ability to degrade in the human body. The aim of this study was to conduct a systematic review, with meta- and trial sequential analyses, to assess the efficacy and morbidity of biodegradable versus titanium osteosynthesis after maxillofacial trauma. MEDLINE, Embase, and CENTRAL were searched for randomized controlled trials and prospective and retrospective controlled studies. Five time periods were studied: perioperative, short-term (0–4 weeks), intermediate (6–12 weeks), long-term (>12 weeks), and overall follow-up. After screening 3542 records, 24 were included. All had a high risk of performance and detection bias due to the nature of the interventions. Meta-analysis showed no differences in efficacy or morbidity between biodegradable and titanium osteosynthesis. The risk of perioperative screw breakage was significantly higher (risk ratio 17.13, 95% confidence interval 2.19–34.18) and the symptomatic plate removal rate lower in the biodegradable group (risk ratio 0.11, 95% confidence interval 0.02–0.57), which was confirmed by the trial sequential analysis. The quality of evidence ranged from very low to moderate. Based on the narrative review and meta-analyses, current evidence shows that biodegradable osteosynthesis is a viable alternative to titanium osteosynthesis when applied in the treatment of maxillofacial trauma, with similar efficacy but significantly lower symptomatic plate removal rates. Perioperative screw breakage occurred significantly more often in the biodegradable group compared to the titanium group.  相似文献   
9.
10.
BackgroundChildren with IgE-mediated cow's milk allergy (IgE-CMA) with gastrointestinal symptoms tolerate yogurt at 100%. Yogurt tolerance in children with IgE-CMA with urticaria and anaphylaxis was 7%.MethodsWe enrolled children with IgE-CMA with cutaneous, respiratory, gastrointestinal and anaphylactic symptoms. All performed prick by prick (PbP) and oral food challenge (OFC) with yogurt. Some children performed also an OFC with CM mixed with wheat flour and baked, baked liquid CM, parmesan.Results34 children were enrolled, 31/34 (91%) with systemic adverse reaction after ingestion of CM (systemic CMA), 3/34 (9%) with isolated contact urticaria (ICU CMA). PbP with yogurt was negative only in one patient. OFC with yogurt was passed (that is, the OFC was negative) by 20/31 (64%) of the children with systemic CMA. 10/11 (91%) of the patients who failed OFC (that is, the OFC was positive) with yogurt were positive to SPT with casein vs. 8/20 (40%) of the patients who passed it (p = 0.018). None of the 19 children who passed OFC with yogurt failed all OFC with processed CM forms other than yogurt that tested vs. 4/8 among those who failed OFC with yogurt (p = 0.006). The rub test with yogurt was negative in 1/3 (33%) of the patients with ICU CMA.ConclusionsThe results of our study are placed alongside others already present in the literature and concerning other methods of processing CM proteins and help to reduce the dietary restrictions of the majority of children with systemic IgE-CMA.  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