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   2831篇
  免费   180篇
  国内免费   12篇
耳鼻咽喉   41篇
儿科学   89篇
妇产科学   46篇
基础医学   413篇
口腔科学   173篇
临床医学   196篇
内科学   694篇
皮肤病学   68篇
神经病学   145篇
特种医学   194篇
外国民族医学   1篇
外科学   259篇
综合类   62篇
一般理论   1篇
预防医学   285篇
眼科学   29篇
药学   164篇
中国医学   47篇
肿瘤学   116篇
  2023年   16篇
  2022年   73篇
  2021年   96篇
  2020年   65篇
  2019年   92篇
  2018年   115篇
  2017年   67篇
  2016年   72篇
  2015年   86篇
  2014年   113篇
  2013年   138篇
  2012年   195篇
  2011年   201篇
  2010年   127篇
  2009年   111篇
  2008年   138篇
  2007年   135篇
  2006年   102篇
  2005年   111篇
  2004年   71篇
  2003年   57篇
  2002年   78篇
  2001年   41篇
  2000年   49篇
  1999年   34篇
  1998年   44篇
  1997年   41篇
  1996年   40篇
  1995年   41篇
  1994年   30篇
  1993年   22篇
  1992年   24篇
  1991年   12篇
  1990年   22篇
  1989年   34篇
  1988年   21篇
  1987年   28篇
  1986年   23篇
  1985年   26篇
  1984年   25篇
  1983年   25篇
  1982年   18篇
  1981年   19篇
  1980年   18篇
  1979年   13篇
  1978年   11篇
  1976年   12篇
  1973年   11篇
  1969年   11篇
  1968年   12篇
排序方式: 共有3023条查询结果,搜索用时 31 毫秒
61.
Purpose

Regular physical activity is a good strategy to maintain the health of athletes, and prevent pain and decreased joint flexibility during the pandemic. On the other hand, higher sedentary time during the pandemic period can have deleterious effects. The objective of this study was to compare physical activity levels, sedentary time, and sleep parameters during the pre-COVID period and the COVID-19 pandemic period in young badminton athletes.

Methods

Fifteen young badminton athletes were evaluated during a pre-COVID period (July 2019) and during the COVID-19 period (July 2020). Sleep parameters, physical activity level, and sedentary time were measured using a tri-axial accelerometer. Participants wore the accelerometer on their dominant wrist for 7 days consecutively. In addition, the average of each sleep parameter [time in bed and total sleep time in hours per day, sleep efficiency (%), wake after sleep onset (WASO, total per day), and sleep latency (minutes per day)] was reported over the 7-day period.

Results

Athletes presented increased sedentary time (pre-COVID?=?7.0?±?1.1 vs.COVID-19?=?8.9?±?1.9 h/day, p?=?0.004, d?=?1.30) and significant decreases in the total PA observed in counts per day (pre-COVID?=?2,967,064.4?±?671,544.1 vs. COVID-19?=?1,868,210.2?±?449,768.4 counts/day, p?=?0.001, d?=?1.99), time in vigorous PA (pre-COVID?=?7.7?±?0.9 vs. COVID-19?=?6.1?±?1.2 h/day, p?=?0.001, d?=?1.56), and time in moderate-to-vigorous PA (pre-COVID?=?8.1?±?0.9 vs. COVID-19?=?6.5?±?1.3 h/day, p?=?0.001, d?=?1.48). There were no significant differences for time in light and moderate PA or in sleep parameters (p?>?0.05).

Conclusion

Young badminton athletes presented increased sedentary time, and decreased total physical activity, time in MVPA, and time in vigorous activities during the COVID-19 pandemic compared to the pre-COVID period, however, there were no significant differences in sleep parameters.

  相似文献   
62.
The anti-inflammatory activity of Canavalia seed lectins (Canavalia gladiata [CGL], Canavalia maritima [ConM] and Canavalia brasiliensis [ConBr]) was evaluated by intravenous administration in rats. In non-sensitized rats, cellular edema elicited by carrageenan was reduced (45–51 %) by ConM and (44–59 %) by CGL. Osmotic edema elicited by dextran was reduced by ConM and CGL in 27 % and 29 %. ConM and CGL reduced the edema elicited by l-arginine in 53 % and that of prostaglandin E2 in 48 % and 36 %. Leukocyte migration elicited by carrageenan was reduced in 49 % by ConM and in 55 % by CGL (attenuated in 4× by glucose) and peritoneal TNF-α content in 82 %. In rats sensitized, ConM inhibited the paw edema and leukocyte migration elicited by ovalbumin in 34 % and 70 %. ConM and CGL are anti-inflammatory, mainly in cellular events mediated by prostaglandin E2, nitric oxide and TNF-α in non-sensitized rats. However, only ConM is anti-inflammatory in sensitized rats. CGL effect involves the lectin domain.  相似文献   
63.
PurposeTo develop a fuzzy linguistic model to quantify the level of distress of patients seeking cosmetic surgery. Body dysmorphic disorder (BDD) is a mental condition related to body image relatively common among cosmetic surgery patients; it is difficult to diagnose and is a significant cause of morbidity and mortality. Fuzzy cognitive maps are an efficient tool based on human knowledge and experience that can handle uncertainty in identifying or grading BDD symptoms and the degree of body image dissatisfaction. Individuals who seek cosmetic procedures suffer from some degree of dissatisfaction with appearance.MethodsA fuzzy model was developed to measure distress levels in cosmetic surgery patients based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), diagnostic criterion B for BDD. We studied 288 patients of both sexes seeking abdominoplasty, rhinoplasty, or rhytidoplasty in a university hospital.ResultsPatient distress ranged from “none” to “severe” (range = 7.5–31.6; cutoff point = 18; area under the ROC curve = 0.923). There was a significant agreement between the fuzzy model and DSM-IV criterion B (kappa = 0.805; p < 0.001).ConclusionThe fuzzy model measured distress levels with good accuracy, indicating that it can be used as a screening tool in cosmetic surgery and psychiatric practice.  相似文献   
64.
Gastric adenocarcinoma is a global health concern, and Helicobacter pylori (H. pylori) infection is the main risk factor for its occurrence. Of note, the immune response against the pathogen seems to be a determining factor for gastric oncogenesis, and increasing evidence have emphasized several host and bacterium factors that probably influence in this setting. The development of an inflammatory process against H. pylori involves a wide range of mechanisms such as the activation of pattern recognition receptors and intracellular pathways resulting in the production of proinflammatory cytokines by gastric epithelial cells. This process culminates in the establishment of distinct immune response profiles that result from the cytokine-induced differentiation of T naïve cells into specific T helper cells. Cytokines released from each type of T helper cell orchestrate the immune system and interfere in the development of gastric cancer in idiosyncratic ways. Moreover, variants in genes such as single nucleotide polymorphisms have been associated with variable predispositions for the occurrence of gastric malignancy because they influence both the intensity of gene expression and the affinity of the resultant molecule with its receptor. In addition, various repercussions related to some H. pylori virulence factors seem to substantially influence the host immune response against the infection, and many of them have been associated with gastric tumorigenesis.  相似文献   
65.
RationalTherapeutic Plasma Exchange (TPE) procedures in pediatric patients are challenging due to the large extracorporeal volume of the cell separators, which were designed for adults. Red blood cell (RBC) priming is an alternative for overpassing the risks of hypovolemia, but data referring to the volume of packed RBCs to be infused are yet incomplete. Restricting the volume of RBC priming may potentially be associated with less transfusion reactions.GoalTo determine the safety of administering a reduced volume of RBC priming for pediatric patients undergoing TPE, in comparison to the standard volume recommended by the cell separators’ manufacturers.MethodsThis was a case-control study which enrolled 15 pediatric patients undergoing TPE and weighting more than 10Kg. The TPE procedures (n = 406) were divided in two groups: 1) Group1: TPE with ≤150 mL of packed RBC priming and 2) Group2: TPE with 150-250 mL of RBC priming. Groups were compared in terms of hemoglobin / hematocrit and occurrence of adverse reactions.ResultsGroup1 and Group2 did not differ significantly in relation to pre- and post-TPE hemoglobin (Hb) levels (p = 0.19 and p = 0.18, respectively). The Δ Hb (Hb pre-TPE – Hb post-TPE) was also not statistically different between the groups. The number of adverse reactions was significantly higher in Group 2 in relation to Group 1 (p = 0.01). The number of allergic reactions was also higher in Group 2 (p = 0.06).ConclusionsRestricting the volume of RBC priming to less than 150 mL is safe for pediatric patients weighting more than 10Kg and associated with lower rates of transfusion-related adverse reactions.  相似文献   
66.
The Schistosoma mansoni gene coding for a 14-kDa fatty acid-binding protein was amplified by PCR and subcloned into the prokaryotic expression vector pMAL-c2. Escherichia coli DH5alpha was transformed with the pMAL-Sm14 construct, and gene expression was induced hr isopropyl-beta-D-thiogalactopyranoside. The resulting recombinant (r) fusion protein was purified by affinity chromatography and confirmed by immunoblot analysis using antimaltose-binding protein or anti-Sm14 antibodies. Additionally, an antibody isotype profile was determined in sera of schistosomiasis patients to rSm14 or soluble adult worm antigen preparation. IgG1 and IgG3 subclass antibodies to rSm14 were predominant in sera of all patients studied whereas low levels of IgM, IgA or IgE were measured. Expression of a S. mansoni gene encoding a vaccine candidate is an important step to better study human immune responses to defined antigens.  相似文献   
67.
In a prospective study of renal involvement in 100 consecutively hospitalized patients with hepatosplenic schistosomiasis mansoni, 15 exhibited persistent proteinuria of varying degree, which in 6 instances was accompanied by hypertension. Nine patients had the nephrotic syndrome. The most common glomerular lesion in this group was membrano-proliferative glomerulonephritis. Surgical biospy obtained during splenectomy in 15 patients without clinical evidence of renal involvement showed glomerular lesions in 6 instances. Focal proliferative glomerulonephritis was the most common lesion in this group. The detection of silent glomerular lesions in patients with Schistosoma mansoni infection suggests that the glomerular alterations may precede clinical manifestations of renal disease.  相似文献   
68.
Background: There are few studies on periodontal status related to microbiologic and immunologic profiles among individuals not or occasionally using alcohol and those with alcohol dependence. The aim of this study is to determine the effect of alcohol consumption on the levels of subgingival periodontal pathogens and proinflammatory cytokines (interleukin [IL]‐1β and tumor necrosis factor [TNF]‐α) in the gingival fluid among individuals with and without periodontitis. Methods: This observational analytic study includes 88 volunteers allocated in four groups (n = 22): individuals with alcohol dependence and periodontitis (ADP), individuals with alcohol dependence and without periodontitis (ADNP), individuals not or occasionally using alcohol with periodontitis (NAP), and individuals not or occasionally using alcohol without periodontitis (NANP). Levels of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Eikenella corrodens, and Fusobacterium nucleatum were determined by real‐time polymerase chain reaction on the basis of the subgingival biofilm, and IL‐1β and TNF‐α were quantified by enzyme‐linked immunosorbent assay in gingival fluid samples. Results: Individuals with alcohol dependence showed worse periodontal status and higher levels of P. intermedia, E. corrodens, F. nucleatum, and IL‐1β than non‐users. No significant correlations between TNF‐α and bacterial levels were observed. However, in the ADP group, higher levels of E. corrodens were correlated with higher levels of IL‐1β. Conclusion: A negative influence of alcohol consumption was observed on clinical and microbiologic periodontal parameters, as well as a slight influence on immunologic parameters, signaling the need for additional studies.  相似文献   
69.
Background: New drugs for the treatment of diabetes, glucagon‐like peptide‐1 (GLP‐1) receptor agonists and inhibitors of dipeptidyl peptidase‐4 (DPP‐4) have shown pleiotropic effects on bone metabolism and anti‐inflammatory properties. The aim of this study is to evaluate the effects of exenatide (GLP‐1 agonist) and sitagliptin (DPP‐4 inhibitor) during periodontitis induction by ligature insertion in rats. Methods: Forty rats were divided into four groups: 1) animals with induced periodontitis that received exenatide (EG); 2) animals with induced periodontitis that received sitagliptin (SG); 3) animals with induced periodontitis and without drug treatment (LG); and 4) animals without induced periodontitis and without drug treatment (controls). The drugs were administered for 28 days. On the day the animals were sacrificed, blood was collected for analysis of glucose and DPP‐4 levels. The gene expressions of prostaglandin‐endoperoxide synthase 2, tissue inhibitor of metalloproteinase 1, Dpp4, nitric oxide synthase 2 (Nos2), interleukin 1β (Il1b), and matrix metalloproteinase 9 (Mmp9) in the gingiva; support and alveolar bone loss; connective tissue attachment; and the quantity of gingival collagen were evaluated. Results: Exenatide and sitagliptin treatments have led to a lower percentage of weight gain but did not influence glycemia. Sitagliptin reduced the serum concentration of DPP‐4. Interestingly, although the gene expression profile has revealed a downregulation of Mmp9, Nos2, and Il1b in both EG and SG compared to LG, a significant protective effect was not observed on alveolar bone and collagen tissue in this model. Conclusion: Regardless of the reduction of the expression of Il1b, Nos2, and Mmp9, the drugs were not effective in the stabilization or reduction of alveolar bone loss and collagen degradation in rats.  相似文献   
70.
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