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   3786篇
  免费   219篇
  国内免费   48篇
耳鼻咽喉   32篇
儿科学   102篇
妇产科学   75篇
基础医学   431篇
口腔科学   278篇
临床医学   706篇
内科学   576篇
皮肤病学   65篇
神经病学   328篇
特种医学   176篇
外科学   285篇
综合类   33篇
一般理论   1篇
预防医学   483篇
眼科学   77篇
药学   248篇
中国医学   44篇
肿瘤学   113篇
  2023年   23篇
  2022年   51篇
  2021年   91篇
  2020年   78篇
  2019年   95篇
  2018年   83篇
  2017年   78篇
  2016年   85篇
  2015年   131篇
  2014年   150篇
  2013年   174篇
  2012年   236篇
  2011年   273篇
  2010年   172篇
  2009年   134篇
  2008年   207篇
  2007年   239篇
  2006年   190篇
  2005年   153篇
  2004年   135篇
  2003年   104篇
  2002年   111篇
  2001年   85篇
  2000年   70篇
  1999年   61篇
  1998年   104篇
  1997年   95篇
  1996年   88篇
  1995年   73篇
  1994年   55篇
  1993年   61篇
  1992年   35篇
  1991年   40篇
  1990年   39篇
  1989年   31篇
  1988年   41篇
  1987年   20篇
  1986年   25篇
  1985年   18篇
  1984年   17篇
  1983年   12篇
  1982年   11篇
  1981年   9篇
  1980年   8篇
  1979年   6篇
  1978年   7篇
  1973年   6篇
  1970年   4篇
  1968年   6篇
  1966年   4篇
排序方式: 共有4053条查询结果,搜索用时 437 毫秒
61.
62.
This work aimed to optimise a new nanoemulsion (NE) formulation loaded with Amphotericin B (AmB) and to evaluate its in vivo antileishmanial activity and in vitro haemolytic toxicity. The influence of gradual increases in pressure, using a high-pressure homogeniser, was evaluated. The NE was characterised for droplet size, polydispersity index, zeta potential and encapsulation efficiency (EE). For antileishmanial activity studies, AmB-NE was administered intravenously in mice infected by Leishmania infantum chagasi, which causes Visceral Leishmaniasis (VL). When the NE was submitted to gradual increases in pressure, the PI values and droplet size decreased. The droplet size (~145?nm) was lower than that obtained in previous studies. The zeta potential was negative and the EE was almost 100%. The haemolytic toxicity, evaluated on human red blood cells, for AmB-loaded NE was lower than that observed for the conventional AmB (C-AmB). C-AmB at 2?mg/kg was very toxic. In contrast, administration of the AmB-loaded NE, at same dose, did not result in any sign of acute toxicity, promoting a significant reduction in parasite burden as compared to the C-AmB. These findings suggest that this new AmB-loaded NE constitutes an attractive alternative for the treatment of VL due to improved efficacy and lower toxicity.  相似文献   
63.
Background and aim: Fecal calprotectin (FC) is a noninvasive marker of intestinal inflammation. Predicting relapses in Crohn’s disease (CD) patients can allow earlier changes in therapy. The aim of this study was to evaluate the role of FC in predicting relapse in CD patients in clinical remission within six months follow-up.

Methods: Patients with CD who were in clinical remission at least ≥3 months were included in this study. The first FC sample during the remission period was evaluated and was used as the baseline value. Relapse was defined as an unexpected escalation in therapy, hospitalization or need for surgery for active CD. The accuracy and optimal cutoff FC values for predicting clinical relapse at six months were assessed by the area under the ROC curve (AUC).

Results: One hundred and forty-four patients were evaluated, with mean age of 38.4 years. Of these, 13 (9%) had a relapse during the follow-up period. The mean FC value was significantly lower for non-relapsers (203.2?μg/g) than for relapsers (871.3?μg/g), p?<?.001. The AUC for predicting relapse by using FC values was 0.924. The optimal cutoff FC value to predict relapse was 327?μg/g; with values of sensitivity, specificity, negative predictive value and positive predictive value were 92.3%, 82.4%, 99.1% and 34.3%, respectively.

Conclusions: FC is more useful in predicting remission maintenance than relapse in patients with CD in clinical remission. Values of FC ≤327?μg/g can exclude relapse at least at six months follow-up period.  相似文献   

64.
65.
Myofibroblasts are hybrid-phenotype differentiated cells in between fibroblasts and smooth muscle cells. Due to their contractile features and ability to synthesize extracellular matrix components, cytokines, proteases, and proangiogenic factors, myofibroblasts have been implicated in the pathogenesis of fibrocontractive diseases and in the progression of many tumors, including oral squamous cell carcinoma (SCC).ObjectiveTo perform a literature review on the origin of myofibroblasts, their main morpho-physiological and immunohistochemical aspects, and to discuss the correlations with oral SCC.MethodA search was made on the PUBMED database to select the main papers in the literature in English related to the subject, published between January 1991 and December 2011.ConclusionMyofibroblasts are an important component of the stroma of oral SCCs, although they are not present in all tumors. Abundant presence of myofibroblasts may be associated with local disease recurrence and decreased patient survival. However, given the relatively limited number of studies on the subject, further research is needed to clarify the molecular mechanisms by which myofibroblasts influence the biological behavior of oral SCC.  相似文献   
66.
67.
The dopamine transporter (DAT) is responsible for terminating dopamine (DA) signaling and is the primary site of cocaine''s reinforcing actions. Cocaine self-administration has been shown previously to result in changes in cocaine potency at the DAT. To determine whether the DAT changes associated with self-administration are due to differences in intake levels or temporal patterns of cocaine-induced DAT inhibition, we manipulated cocaine access to produce either continuous or intermittent elevations in cocaine brain levels. Long-access (LgA, 6 h) and short-access (ShA, 2 h) continuous self-administration produced similar temporal profiles of cocaine intake that were sustained throughout the session; however, LgA had greater intake. ShA and intermittent-access (IntA, 6 h) produced the same intake, but different temporal profiles, with ‘spiking'' brain levels in IntA compared with constant levels in ShA. IntA consisted of 5-min access periods alternating with 25-min timeouts, which resulted in bursts of high responding followed by periods of no responding. DA release and uptake, as well as the potency of cocaine for DAT inhibition, were assessed by voltammetry in the nucleus accumbens slices following control, IntA, ShA, and LgA self-administration. Continuous-access protocols (LgA and ShA) did not change DA parameters, but the ‘spiking'' protocol (IntA) increased both release and uptake of DA. In addition, high continuous intake (LgA) produced tolerance to cocaine, while ‘spiking'' (IntA) produced sensitization, relative to ShA and naive controls. Thus, intake and pattern can both influence cocaine potency, and tolerance seems to be produced by high intake, while sensitization is produced by intermittent temporal patterns of intake.  相似文献   
68.
Parasitology Research - Phthalimide, 1,3-thiazole, and thiazolidinone cores are considered privileged scaffolds and represent an attractive starting point to design new bioactive compounds for...  相似文献   
69.
Considering the complex relationship between asthma symptoms and exercise, asthmatics are usually believed to be less active in daily life than healthy subjects. However, few studies have objectively assessed daily-life physical activity (DLPA) of asthmatic adults. Objective: To objectively assess DLPA of a sample of Brazilian asthmatic women in comparison to healthy controls, and to investigate the associations between DLPA and asthma control, health-related quality of life, anxiety and depression levels, and the Six-minute walk test (6MWT) in this population. Methods: Sixty-six women were included, 36 in the asthma group (AG) and 30 in the control group (CG). The AG was composed by clinically stable moderate-to-severe asthmatics. The CG was composed by apparently healthy volunteers. All subjects underwent DLPA assessment (considered as the average of steps taken during six consecutive days measured by a pedometer) and performed the 6MWT. Additionally, participants in the AG were assessed using the Asthma Control Questionnaire, the Asthma Quality of Life Questionnaire (AQLQ), and the Hospital Anxiety and Depression Scale. Results: There was no difference between the AG and the CG regarding DLPA (7490.3 ± 3330.2 vs 6876.4 ± 3242.1 steps respectively, p = 0.45), even after adjustment for covariates. DLPA was significantly correlated to the activity limitation domain of the AQLQ among asthmatics (r = 0.43, p < 0.01). Conclusion: Despite the association between self-perceived activity limitation and DLPA among asthmatics, there were no differences regarding DLPA between a sample of moderate-to-severe Brazilian asthmatic women and apparently healthy controls.  相似文献   
70.
Metabolic Brain Disease - Leptin is an adipose tissue-derived hormone that acts on the hypothalamus in order to maintain energy homeostasis. However, leptin can also induce an inflammatory...  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