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   3060篇
  免费   215篇
  国内免费   14篇
耳鼻咽喉   23篇
儿科学   142篇
妇产科学   108篇
基础医学   424篇
口腔科学   46篇
临床医学   290篇
内科学   633篇
皮肤病学   88篇
神经病学   343篇
特种医学   71篇
外科学   339篇
综合类   31篇
一般理论   7篇
预防医学   258篇
眼科学   58篇
药学   174篇
中国医学   16篇
肿瘤学   238篇
  2024年   7篇
  2023年   50篇
  2022年   97篇
  2021年   162篇
  2020年   100篇
  2019年   127篇
  2018年   139篇
  2017年   108篇
  2016年   110篇
  2015年   112篇
  2014年   142篇
  2013年   153篇
  2012年   272篇
  2011年   301篇
  2010年   152篇
  2009年   123篇
  2008年   188篇
  2007年   166篇
  2006年   153篇
  2005年   146篇
  2004年   117篇
  2003年   94篇
  2002年   89篇
  2001年   19篇
  2000年   11篇
  1999年   10篇
  1998年   12篇
  1997年   10篇
  1996年   6篇
  1995年   8篇
  1994年   8篇
  1993年   8篇
  1992年   13篇
  1991年   4篇
  1990年   10篇
  1988年   4篇
  1987年   6篇
  1986年   4篇
  1985年   6篇
  1984年   5篇
  1983年   4篇
  1981年   2篇
  1980年   3篇
  1978年   2篇
  1976年   4篇
  1975年   3篇
  1974年   6篇
  1973年   2篇
  1970年   2篇
  1969年   2篇
排序方式: 共有3289条查询结果,搜索用时 15 毫秒
131.
It is suggested that masticatory dysfunction affects the central nervous system; however, the underlying mechanism remains unknown. Brain‐derived neurotrophic factor (BDNF) and its receptor, TrkB, are known to play important roles in memory and learning. In this study, we examined the effects of mastication on memory, the expression levels of BDNF and TrkB, and the number of neurons in the hippocampus of mice. Male C57 BL/6J mice (3 weeks old) were randomly divided into the control group (N = 7) fed chow pellets and the experimental group (N = 7) fed a liquid diet, which reduces mastication during eating. At 14 weeks of age, we performed a passive avoidance test and found that memory and learning ability were impaired in the experimental group compared with the control group. After the behavioral experiment, brains were harvested and analyzed morphologically and biochemically. In the hippocampus of the experimental group, the expression levels of BDNF were significantly higher, whereas those of TrkB were lower than those of the control group. In the cerebral cortex, these levels remained unchanged between the two groups. The ratio of phospho‐p44/42 ERK/pan ERK, a downstream molecule of BDNF/TrkB signaling, in the experimental group was significantly lower than that of the control group in the cortex and hippocampus. The number of pyramidal neurons in the hippocampus was lower in the experimental group than in the control group. These findings suggest that reduced mastication induced by a liquid diet in early childhood may impair memory and learning ability, accompanied by neuronal loss in the hippocampus. © 2014 Wiley Periodicals, Inc.  相似文献   
132.
The presence of mirror dystonia (dystonic movement induced by a specific task performed by the unaffected hand) in the dominant hand of writer's cramp patients when the nondominant hand is moved suggests an abnormal interaction between the 2 hemispheres. In this study we compare the level of interhemispheric inhibition (IHI) in 2 groups of patients with writer's cramp, one with the presence of a mirror dystonia and the other without as well as a control group. The level of bidirectional IHI was measured in wrist muscles with dual‐site transcranial magnetic stimulation with a 10‐millisecond (short IHI) and a 40‐millisecond (long IHI) interstimulus interval during rest and while holding a pen in 9 patients with mirror dystonia 7 without mirror dystonia, and 13 controls. The group of patients without mirror dystonia did not differ from the controls in their IHI level. In contrast, IHI was significantly decreased in the group of patients with mirror dystonia in comparison with the group without mirror dystonia and the controls in both wrist muscles of both the dystonic and unaffected hand whatever the resting or active condition (P = 0.001). The decrease of IHI level in the group of patients with mirror dystonia was negatively correlated with the severity and the duration of the disease: the weaker the level of IHI, the more severe was the disease and the longer its duration. Interhemispheric inhibition disturbances are most likely involved in the occurrence of mirror dystonia. This bilateral deficient inhibition further suggests the involvement of the unaffected hemisphere in the pathophysiology of unilateral dystonia. © 2013 International Parkinson and Movement Disorder Society  相似文献   
133.
AimsThis meta-analysis aims to analyze the association of calcium channel blocker (CCB) use with COVID-19 clinical outcomes.MethodsPubMed, ProQuest, Science Direct, Scopus, and medRxiv databases were searched systematically in a limited period. The primary outcome was mortality.ResultsA total of 119,298 patients from 31 eligible studies were included. Pooled analysis of the random-effect model revealed CCB was not associated with reduced mortality (OR = 1.21 [95%CI: 0.98–1.49], p = 0.08). Interestingly, subgroup analysis in hypertensive patients revealed significantly reduced mortality (OR = 0.69 [95%CI: 0.52–0.91], p = 0.009).ConclusionCCB usage was not associated with the outcome of COVID-19. However, CCB was associated with a decreased mortality rate in hypertensive COVID-19 patients.  相似文献   
134.
Now that the human genome has been sequenced, the challenge of assigning function to human genes has become acute. Existing approaches using microarrays or proteomics frequently generate very large volumes of data not directly related to biological function, making interpretation difficult. Here, we describe a technique for integrative systems biology in which: (i) primary cells are cultured under biologically meaningful conditions; (ii) a limited number of biologically meaningful readouts are measured; and (iii) the results obtained under several different conditions are combined for analysis. Studies of human endothelial cells overexpressing different signaling molecules under multiple inflammatory conditions show that this system can capture a remarkable range of functions by a relatively small number of simple measurements. In particular, measurement of seven different protein levels by ELISA under four different conditions is capable of reconstructing pathway associations of 25 different proteins representing four known signaling pathways, implicating additional participants in the NF-kappaBorRAS/mitogen-activated protein kinase pathways and defining additional interactions between these pathways.  相似文献   
135.
Agonists of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR gamma) are pharmacologically active antihyperglycemic agents that act by increasing peripheral tissue sensitivity to insulin. Many of these agonists have antihyperglycemic activity that is directly proportional to their ability to bind and activate PPAR gamma; however, recent data bring this relationship into question. In this report we describe a new PPAR gamma agonist, CLX-0921, that is derived from a natural product. This thiazolidinedione (TZD) has a spectrum of activity that differs from commercially available TZDs. It is a weak activator of PPAR gamma (EC(50) of 0.284 micromol/L) compared to rosiglitazone (EC(50) 0.009 micromol/L). Despite this difference, the drug maintains potent glucose uptake activity in vitro and glucose-lowering activity in vivo that is equipotent to that of rosiglitazone. Moreover, CLX-0921 showed a 10-fold reduction in in vitro adipogenic potential compared to rosiglitazone. CLX-0921 also increases glycogen synthesis, an activity not typically associated with rosiglitazone or pioglitazone. Thus CLX-0921 appears to have a distinct spectrum of activity relative to other TZDs.  相似文献   
136.
A 48-year-old woman underwent surgery for a lesion seen on ultrasound and interpreted as a uterine myoma. The surgery revealed multiple nodules that had seeded on the omentum, peritoneum, and ovaries. The macroscopic interpretation was either metastasis or tuberculosis. The biopsy showed noncaseating granulomas, and a diagnosis of peritoneal sarcoidosis was reported. The AFB (acid fast bacillus) and L?wenstein-Jensen culture were negative. She was treated with methylprednisolone for 1 year for pulmonary sarcoidosis progression, with a resulting decrease in her DLCO (diffusing lung capacity for carbon monoxide). Computed tomography showed only a slight decrease in the multiple nodules and cysts. She is currently symptom-free.  相似文献   
137.
Primary hyperparathyroidism (PHP) is an uncommon disease in children and adolescents. The association between PHP and slipped capital femoral epiphysis is rare, and so far only four cases have been reported in the literature. Herein, we report a case of PHP due to a parathyroid adenoma, with several painful skeletal deformities and associated with slipped capital femoral epiphysis in an 18-year-old male patient. Laboratory evaluation showed: calcium of 13.6 mg/dL, parathyroid hormone of 1,524 pg/mL and alkaline phosphatase of 3,449 U/L. Deformities were caused by late diagnosis during the growth spurt, and this association is the result of combinations between metabolic and mechanical factors. The patient underwent parathyroidectomy and, in agreement with the literature, since the removal of the adenoma is followed by prompt resolution of the slipped capital femoral epiphysis we decided for a conservative approach. We observed improvement of the pain and normalization of calcium and parathyroid hormone levels.  相似文献   
138.

Aims

To determine the frequency of increasing levels of stress hyperglycemia and its associated complications in surgery patients without a history of diabetes.

Methods

We reviewed hospital outcomes in 1971 general surgery patients with documented preoperative normoglycemia [blood glucose (BG) < 140 mg/dL] who developed stress hyperglycemia (BG > 140 mg/dL or > 180 mg/dL) within 48 h after surgery between 1/1/2010 and 10/31/2015.

Results

A total of 415 patients (21%) had ≥ 1 episode of BG between 140 and 180 mg/dL and 206 patients (10.5%) had BG > 180 mg/dL. The median length of hospital stay (LOS) was 9 days [interquartile range (IQR) 5,15] for BG between 140 and 180 mg/dL and 12 days (IQR 6,18) for BG > 180 mg/dL compared to normoglycemia at 6 days (IQR 4,11), both p < 0.001. Patients with BG 140–180 mg/dL had higher rates of complications with an odds ratio (OR) of 1.68 [95% confidence interval (95% CI) 1.15–2.44], and those with BG > 180 mg/dL had more complications [OR 3.46 (95% CI 2.24–5.36)] and higher mortality [OR 6.56 (95% CI 2.12–20.27)] compared to normoglycemia.

Conclusion

Increasing levels of stress hyperglycemia are associated with higher rates of perioperative complications and hospital mortality in surgical patients without diabetes.  相似文献   
139.
Recent discoveries have led to the identification of a novel group of immune cells, the innate lymphoid cells (ILCs). The members of this group are divided into three subpopulations: ILC1s, ILC2s, and ILC3s. ILC2s produce Th2 cytokines, IL-4, IL-5, and IL-13, upon activation by epithelial cell-derived cytokines, lipid mediators (cysteinyl leukotrienes and prostaglandin D2), and TNF family member TL1A and promote structural and immune cell responses in the airways after antigen exposure. In addition, ILC2 function is also influenced by inducible T cell costimulator (ICOS)/ICOS-ligand (ICOS-L) interactions via direct contact between immune cells. The most common airway antigens are allergens and viruses which are highly linked to the induction of airway diseases with underlying type 2 inflammation including asthma and allergic rhinitis. Based on recent findings linking ILC2s and airway Th2 responses, there is intensive investigation into the role of ILC2s in human disease with the hope of a better understanding of the pathophysiology and the discovery of novel potential therapeutic targets. This review summarizes the recent advances made in elucidating ILC2 involvement in human Th2 airway disease.  相似文献   
140.

Background

African American youth residing in urban poverty have been shown to be at increased risk for exposure to violence and for psychological symptoms, but there has been little investigation of mediating processes that might explain this association.

Objectives

This study tested the quality of parent–adolescent relationships and adolescent nondisclosure to adults as mediating mechanisms through which exposure to community violence may lead to psychological symptoms.

Methods

The current study surveyed a sample of 152 low-income urban African American early adolescents (aged 12–14). Participants completed self-report questionnaires assessing exposure to community violence, nondisclosure, parent–adolescent relationship, and psychological symptoms (i.e., internalizing and externalizing symptoms).

Results

Path analyses revealed that parent–adolescent relationship quality and nondisclosure both functioned as mediators of the relation between exposure to community violence and both internalizing and externalizing symptoms, though significant direct effects for violence exposure on externalizing symptoms remained. Decomposition of effects revealed that nondisclosure was a stronger mediator than parent–adolescent relationship quality. Results also indicated that exposure to violence can lead to externalizing (but not internalizing) symptoms first by way of parent–adolescent relationship quality and then nondisclosure.

Conclusions

Combined, these findings suggest that the development of preventive interventions designed to assist adults and parents improve communication and strengthen relationships with adolescents might reduce the negative effects of exposure to community violence on adolescent mental health.
  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