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   8629篇
  免费   686篇
  国内免费   26篇
耳鼻咽喉   171篇
儿科学   404篇
妇产科学   223篇
基础医学   986篇
口腔科学   234篇
临床医学   691篇
内科学   2195篇
皮肤病学   275篇
神经病学   573篇
特种医学   300篇
外科学   1488篇
综合类   61篇
一般理论   2篇
预防医学   728篇
眼科学   194篇
药学   406篇
中国医学   34篇
肿瘤学   376篇
  2023年   36篇
  2022年   79篇
  2021年   225篇
  2020年   125篇
  2019年   288篇
  2018年   280篇
  2017年   206篇
  2016年   215篇
  2015年   220篇
  2014年   309篇
  2013年   392篇
  2012年   437篇
  2011年   520篇
  2010年   363篇
  2009年   280篇
  2008年   408篇
  2007年   460篇
  2006年   469篇
  2005年   433篇
  2004年   386篇
  2003年   374篇
  2002年   363篇
  2001年   313篇
  2000年   364篇
  1999年   268篇
  1998年   100篇
  1997年   80篇
  1996年   69篇
  1995年   60篇
  1994年   53篇
  1993年   48篇
  1992年   138篇
  1991年   121篇
  1990年   105篇
  1989年   104篇
  1988年   60篇
  1987年   59篇
  1986年   50篇
  1985年   61篇
  1984年   36篇
  1983年   35篇
  1982年   20篇
  1981年   20篇
  1980年   21篇
  1979年   27篇
  1975年   22篇
  1973年   24篇
  1972年   22篇
  1971年   21篇
  1969年   22篇
排序方式: 共有9341条查询结果,搜索用时 15 毫秒
31.
Recent models hypothesize that hostility confers increased risk of CHD through weaker parasympathetic dampening of cardiovascular reactivity (CVR). We tested this possibility using the forehead cold pressor task, a common maneuver which elicits the “dive reflex” characterized by a reflexive decrease in HR presumably through cardiac-parasympathetic stimulation. Participants were initially chosen from the outer quartiles of a sample of 670 undergraduates screened using the hostility subscale of the Aggression Questionnaire ([Buss, A.H., Perry, M., 1992. The Aggression Questionnaire. Journal of Personality and Social Psychology, 63, 452-459.]). The final sample of 80 participants was evenly divided between men and women and high and low hostility. Following a 10-min baseline, participants underwent a 3-min forehead cold pressor task. The task evoked a significant HR deceleration that was mediated by PNS activation, as assessed by respiratory sinus arrhythmia (RSA). Replicating prior research, men displayed greater decrease in HR. More important, low hostiles maintained larger HR deceleration over time compared to high hostiles although the autonomic basis for this effect was unclear. The findings broaden understanding of hostility and sex-related cardiovascular functioning and support the task as a method for evoking PNS-cardiac stimulation.  相似文献   
32.
Three previously healthy children developed gastroenteritis which led within a few days to systemic infections, two cases of bacteremia and one of meningitis. A lactose-fermentingSalmonella virchow strain was isolated from cerebrospinal fluid and blood cultures. In one case, this strain was also isolated from stool cultures. All the children had been fed the same milk formula. There was no other relationship between them. The batch of dried-milk formula was confirmed as the source of the infection by isolation of an identical lactose-fermentingSalmonella virchow strain by the Centro Nacional de Alimentación.  相似文献   
33.
The detection of anti-HBs antibody has been carried out using a new technique where a system for the detection of HBs antigen in the solid phase is adopted to demonstrate the presence of anti HBs antibody by inhibition of the immunoenzymatic reaction. The sensitivity of the method has been compared: with that of passive haemagglutination and with that of radioimmunoassay in liquid phase, for human serum obtained from 10 chronic antibody carriers and also serum from 1 rabbit, with that of solid phase radioimmunoassay for 91 positives serums. The method appears: in the range of sensitivity of passive haemagglutination and radioimmunoassay in the liquid phase, less sensitive than that of solid phase radioimmunoassay, far superior to that of electrosyneresis.  相似文献   
34.
Electric activity in the neocortex of freely moving young and aged rats   总被引:5,自引:0,他引:5  
Electroencephalographic activity of the neocortex was evaluated in young (5-7 months) and aged (26-28 months) rats. All animals in the aged group showed behavioral impairment in a spatial task (water maze). A neocortical electroencephalogram was derived simultaneously from 16 different neocortical locations and was subjected to spectral analysis. The frequency of occurrence and duration of high-voltage spindles was determined in two sessions, each involving a total of 30 min alert immobility. Changes in spectral characteristics and high-voltage spindles in response to scopolamine administration were also evaluated. The power of high-frequency activity (8-20 Hz) was significantly reduced in the aged subjects. This was greatest in the temporo-occipital regions, while no significant changes were seen in the mediofrontal region. Scopolamine resulted in a large power increase in all frequency bands, but the increase in the higher-frequency range (8-20 Hz) was significantly less in the aged group. The incidence of high-voltage spindles was 6 times higher and their total duration was 9 times longer in aged rats, with virtually no overlap with the young group. In young rats, scopolamine increased the incidence and total duration of high-voltage spindles, while it decreased both parameters in the aged subjects. Cholinergic neurons in the nucleus basalis appeared shrunken in the aged animals. These findings demonstrate that reliable electroencephalographic changes are present in the neocortex of the aged rat, and that some of the physiological alterations may be due to the pathological changes in the cholinergic nucleus basalis.  相似文献   
35.
During embryogenesis, colonization of the thymic rudiment by hemopoietic progenitor cells depends on the adhesion of these cells to the jugular endothelium. Previously, we showed that progenitor T cells (pro-T cells) interact with α6 integrins present on vascular endothelium. Here, we demonstrate that anti-α6 integrin antibodies reduced the number of thymocytes up to 80 % in a congenic mouse model for thymus colonization by pro-T cells. In organotypic thymus cultures, the anti-α6 integrin antibodies did not influence T cell development and proliferation. From this, we conclude that α6 integrin participates in thymus homing. During mouse thymus ontogeny, α6 integrin mRNA and protein expression was found as early as day 10 of development; at day 11, perithymic endothelial cells were α6 integrin positive. Two α6 integrin mRNA exist which are produced by alternative exon usage. The longer form, α6, integrin, predominates during early embryonic stages, while the shorter α6A form was present later during development. Although α6, integrins can be displayed by immature thymocytes, strongest expression was found on intra- and perithymic vascular endothelium. These data suggest that α6 integrins are involved in the homing of pro-T cells to the developing thymus by mediating adhesion of pro-T cells to the vascular endothelium.  相似文献   
36.
BackgroundObesity is a pandemic disease associated to severe health problems. Management is usually multimodal, but many patients eventually need surgery to reduce weight. Many guidelines recommend endoscopy prior to surgery. This study reviews a series of patients undergoing sleeve gastrectomy to see whether endoscopy performance and histopathological findings influence surgery outcome.Material and methodsRetrospective series of patients undergoing sleeve gastrectomy as bariatric procedure at a single institution. We have reviewed the demographic data, the associated pathologies, endoscopic findings prior to surgery, histopathological findings in the surgical resection specimen and postoperative complication rate.Results259 patients fulfilled criteria for the study. Over 70% were women and the mean age was 46.9 (SD 9.8). Preoperative endoscopy was performed in 28.9% of the patients and biopsy only in 19.3%. Helicobacter pylori was detected in 28% of the patients undergoing endoscopy (either in the biopsy or the urease test) and eradicated before surgery in all the patients. Helicobacter pylori was present in 9.7% of the surgical resection specimens and its presence was significantly associated with the development of postoperative complications, mostly staple line leaks (p = 0.01).ConclusionOur study confirms that Helicobacter infection is significantly associated with postoperative complications after sleeve gastrectomy. It is therefore important to detect its presence and eradicate it before surgery.  相似文献   
37.
Studies comparing different types of exercise-based interventions have not shown a consistent effect of training on long-term weight maintenance. The aim of this study was to compare the effects of exercise modalities combined with diet intervention on body composition immediately after intervention and at 3 years’ follow-up in overweight and obese adults. Two-hundred thirty-nine people (107 men) participated in a 6-month diet and exercise-based intervention, split into four randomly assigned groups: strength group (S), endurance group (E), combined strength and endurance group (SE), and control group (C). The body composition measurements took place on the first week before the start of training and after 22 weeks of training. In addition, a third measurement took place 3 years after the intervention period. A significant interaction effect (group × time) (p = 0.017) was observed for the fat mass percentage. It significantly decreased by 5.48 ± 0.65%, 5.30 ± 0.65%, 7.04 ± 0.72%, and 4.86 ± 0.65% at post-intervention for S, E, SE, and C, respectively. Three years after the intervention, the fat mass percentage returned to values similar to the baseline, except for the combined strength and endurance group, where it remained lower than the value at pre-intervention (p < 0.05). However, no significant interaction was discovered for the rest of the studied outcomes, neither at post-intervention nor 3 years later. The combined strength and endurance group was the only group that achieved lower levels of fat mass (%) at both post-intervention and 3 years after intervention, in comparison with the other groups.  相似文献   
38.
Exploring an alternative to improve the clinical management of hypertension, we tested the hypothesis that food supplementation with coconut oil (EVCO), alone or combined with aerobic exercise training, could exert an antihypertensive effect (primary outcome) in patients with stage 1 hypertension. Forty-five hypertensive volunteers of both genders participated in a placebo-controlled clinical trial. The volunteers were submitted to 24-hour ambulatory blood pressure monitoring, analysis of blood pressure variability (BPV), measurement of serum malondialdehyde (MDA) and nutritional assessment. Results indicate that EVCO consumption had no adverse effects. The supplementation did not increase the caloric intake compared with placebo, and the dietary constituents were similar between groups, except for the saturated fats, especially lauric acid. The analysis of blood pressure indicated absence of antihypertensive effect of EVCO alone or combined with physical training. Furthermore, no effects on blood pressure variability and oxidative stress were observed in the supplemented hypertensive patients. Thus, despite the results observed in pre-clinical studies, the current clinical study did not provide evidence to support the use of coconut oil as an adjuvant in the management of hypertension in humans.  相似文献   
39.
40.
Increasing sugar-sweetened beverages (SSB) consumption and associated health impacts warrant health-policy action. We assessed associations of socioeconomic and lifestyle variables with adolescents’ consumption of regular soda (RSD), sport (SD), and energy (ED) drinks. Cross-sectional study of 3930 Spanish adolescents (2089 girls, 1841 boys) aged 13–18 years). We compared frequency of consuming each SSB type (European Food Safety Authority questionnaire) with sociodemographic and lifestyle variables (standardized questions). RSD, SD, and ED were consumed at least weekly by 72.7%, 32.3%, and 12.3% of participants, respectively, and more frequently (p < 0.001) by boys, compared to girls. Multivariate ordinal logistic regression showed inverse association between RSD, SD, and ED consumption and parental occupation-based socioeconomic status (p < 0.01). Daily smoking was associated (p < 0.001) with higher ED (OR 3.64, 95% CI 2.39–5.55) and RSD (OR 2.15, 95% CI 1.56–2.97) consumptions. SD intake was associated inversely with smoking (OR 0.60, 95% CI 0.40–0.89, p = 0.012) and directly with physical activity (OR 2.93, 95% CI 2.18–3.95, p < 0.001). School performance was lower among ED (OR 2.14, 95% CI, 1.37–3.35, p = 0.001) and RSD (OR 1.81, 95% CI 1.24–2.64, p = 0.002) consumers, compared to SD. Maleness and low socioeconomic status predicted SSB consumption. Smoking and low school performance were associated with higher ED and RSD intakes.  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