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   3280篇
  免费   220篇
  国内免费   6篇
耳鼻咽喉   24篇
儿科学   114篇
妇产科学   241篇
基础医学   460篇
口腔科学   98篇
临床医学   345篇
内科学   823篇
皮肤病学   52篇
神经病学   386篇
特种医学   69篇
外科学   305篇
综合类   15篇
一般理论   2篇
预防医学   206篇
眼科学   32篇
药学   161篇
中国医学   3篇
肿瘤学   170篇
  2023年   32篇
  2022年   34篇
  2021年   137篇
  2020年   50篇
  2019年   122篇
  2018年   134篇
  2017年   94篇
  2016年   100篇
  2015年   85篇
  2014年   138篇
  2013年   185篇
  2012年   263篇
  2011年   231篇
  2010年   131篇
  2009年   118篇
  2008年   197篇
  2007年   186篇
  2006年   197篇
  2005年   188篇
  2004年   165篇
  2003年   121篇
  2002年   120篇
  2001年   29篇
  2000年   35篇
  1999年   16篇
  1998年   29篇
  1997年   18篇
  1996年   20篇
  1995年   12篇
  1994年   12篇
  1993年   24篇
  1992年   10篇
  1991年   25篇
  1990年   18篇
  1989年   13篇
  1988年   18篇
  1987年   16篇
  1986年   23篇
  1985年   13篇
  1983年   14篇
  1982年   7篇
  1981年   8篇
  1980年   6篇
  1979年   8篇
  1978年   7篇
  1976年   8篇
  1975年   10篇
  1974年   13篇
  1971年   6篇
  1967年   11篇
排序方式: 共有3506条查询结果,搜索用时 31 毫秒
51.
52.
Nonalcoholic fatty liver disease (NAFLD) is a serious health problem. Although NAFLD represents a form of lipotoxicity, its pathogenesis remains poorly understood. The aim of this study was to examine the cellular mechanisms involved in free fatty acid (FFA)-mediated hepatic lipotoxicity. FFA treatment of liver cells resulted in Bax translocation to lysosomes and lysosomal destabilization with release of cathepsin B (ctsb), a lysosomal cysteine protease, into the cytosol. This process was also partially dependent on ctsb. Lysosomal destabilization resulted in nuclear factor kappa B-dependent tumor necrosis factor alpha expression. Release of ctsb into the cytoplasm was also observed in humans with NAFLD and correlated with disease severity. In a dietary murine model of NAFLD, either genetic or pharmacological inactivation of ctsb protected against development of hepatic steatosis, liver injury, and insulin resistance with its associated "dysmetabolic syndrome." In conclusion, these data support a lipotoxic model of FFA-mediated lysosomal destabilization.  相似文献   
53.
OBJECTIVE: To analyze some of the factors associated with material living conditions of adolescents and their means for earning a living, such as idea construction and gender representations, related to sexual and reproductive conduct. MATERIAL AND METHODS: The investigation was conducted in Asuncion, Paraguay, in 2000. Qualitative data collection techniques (in-depth interviews) and interpretive analysis were used. A total of 40 interviews were conducted of young people between the ages of 15 and 20, grouped as "schooled" and "not schooled." RESULTS: Gender constructions exist, denominated in this study as "modern" and "traditional," that classify perceptions about gender roles for women and their position in relation to males, as well as for partner relationships and the exercise of power in such contexts. Ideas and representations about maternity are also defined. CONCLUSIONS: The distinct gender image "types" associated with the adolescents means for earning a living simultaneously condition certain perceptions about gender roles and reproductive conduct.  相似文献   
54.
INTRODUCTION: Targets for radiofrequency ablation (RFA) of atrial fibrillation are increasingly being selected based on anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures, we evaluated whether stereotactic catheter guidance might facilitate anatomical catheter navigation and RFA to the great vessels, the fossa ovalis and the left atrium (LA). METHODS AND RESULTS: An electromagnetic catheter's position system was superimposed on three-dimensional (3D) MR images using fiducial markers. This allowed the dynamic display of the catheter position on the true anatomy of previously acquired MRI in real-time. To assess the reproducibility of RFA, repeat ablations were created at the identical anatomic site in the inferior vena cava (IVC) in 5 swine. Average distance of the repeated ablations was 4.4 +/- 2.4 mm.In five swine the catheter was anatomically guided with the MRI to the fossa ovalis and a single RFA was performed. On the pathological specimen all ablation sites were located within the fossa ovalis with an average distance of 3.9 +/- 2.1 mm from its center. In two of the experiments the ablation catheter was passed into the left atrium and anatomically targeted ablation performed in the lateral wall of the left atrial appendage. Catheter location and ablation site were confirmed by autopsy and histology. CONCLUSION: Real-time display of the catheter position on 3D-MRI allows anatomically targeted catheter navigation and RFA in the IVC, the fossa ovalis, and the left atrium. This may facilitate anatomically based interventions like septal puncture or pulmonary vein ablation and decrease fluoroscopy times.  相似文献   
55.
Decreased pituitary-gonadal secretion in men with obstructive sleep apnea   总被引:6,自引:0,他引:6  
Decreased libido is frequently reported in male patients with obstructive sleep apnea (OSA). The decline in morning serum testosterone levels previously reported in these patients was within the normal adult male range and does not explain the frequent association of OSA and sexual dysfunction. We determined serum LH and testosterone levels every 20 min between 2200-0700 h with simultaneous sleep recordings in 10 men with sleep apnea and in 5 normal men free of any breathing disorder in sleep. The mean levels and area under the curve of LH and testosterone were significantly lower in OSA patients compared with controls [LH, 24.9 +/- 10.2 IU/liter.h vs. 43.4 +/- 9.5 (P < 0.005); testosterone, 67.2 +/- 11.5 nmol/liter.h vs. 113.3 +/- 26.8 (P < 0.003)]. Four of 10 patients had hypogonadal morning (0700 h) serum testosterone levels. Analysis of covariance (ANCOVA) revealed that the 2 groups differed significantly in the amount of LH and testosterone secreted at night independent of age or degree of obesity. After partialing out body mass index, there was a significant negative correlation between the amounts of LH and testosterone secreted at night and the respiratory distress index, but not with degree of hypoxia. Our findings suggest that OSA in men is associated with dysfunction of the pituitary-gonadal axis. The relation between LH-testosterone profiles and the severity of OSA suggests that sleep fragmentation and, to a lesser extent, hypoxia in addition to the degree of obesity and aging may be responsible for the central suppression of testosterone in these patients.  相似文献   
56.
CONTEXT: In clinical practice, patients with acromegaly may be switched from therapy with long-acting somatostatin analogs to pegvisomant. The effect of changing therapies on glucose homeostasis and safety has not been reported. OBJECTIVES: The objectives of this study were to monitor changes in IGF-I levels, glycemic control, and safety, particularly liver function and tumor size. DESIGN: This was a multicenter, open-label, 32-wk trial study. SETTING: The study was performed at outpatient clinics. PATIENTS: Fifty-three patients with acromegaly previously treated with octreotide long-acting release (LAR) participated in this study. Intervention: Pegvisomant (10 mg/d) was initiated 4 wk after the last dose of octreotide LAR and was adjusted based on serum IGF-I concentrations at wk 12, 20, and 28. MAIN OUTCOME MEASURES: The main outcome measures were changes in IGF-I, glycosylated hemoglobin A1c (HbA1c), fasting plasma glucose, and safety during the first 12 wk after conversion. RESULTS: At the end of pegvisomant treatment, IGF-I was normalized in 78% of patients. At wk 32, median fasting glucose concentration and HbA1c were reduced (-1.4 mmol/liter and -0.4%, respectively; both P < or = 0.0001) in the study population. Improvements in glycemic control occurred in patients with normal IGF-I concentrations at wk 4 [n = 15; fasting glucose, -1.7 mmol/liter (P < or = 0.0001); HbA1c -0.2% (P = 0.03)]. Decreases in fasting glucose and HbA1c levels were observed in patients with and without diabetes. HbA1c was reduced by more than 1.0% in patients with diabetes. Median pituitary tumor volume did not change, although tumor volume increased in two patients with macroadenomas. CONCLUSIONS: Conversion from octreotide LAR to pegvisomant was safe and well tolerated. Improved glycemic control indicates that pegvisomant should be considered in patients with acromegaly and diabetes.  相似文献   
57.
BackgroundIcosapent ethyl (IPE) is approved for the prevention of major adverse cardiovascular events (MACE) in patients with hypertriglyceridemia. However, due to budget constraints, access to IPE will inevitably be limited to a fraction of eligible patients. To help maximize value for money spent, we estimated the number of preventable MACE when providing IPE for primary versus secondary prevention.MethodsThe number of preventable MACE was estimated by dividing the available budget by the cost needed to treat (CNT) to prevent one MACE. CNT was calculated as the product of the number needed to treat (NNT) to prevent 1 MACE by therapy cost. NNT values were determined according to the Reduction of Cardiovascular Events with Icosapent Ethyl–Intervention Trial (REDUCE-IT) results. The budget limit was set as the United States’ threshold suggested by the Institute for Clinical and Economic Review. Sensitivity analysis was performed regarding the cost of IPE in the United States.ResultsThe NNT to prevent 1 MACE over 4.9 years in the Reduction of Cardiovascular Events with Icosapent Ethyl–Intervention Trial primary prevention cohort was 59 (95% confidence interval [CI]: 24-∞) versus 14 (11-21) for secondary prevention. At an annual IPE cost of $2915, the CNT to prevent 1 MACE was $842,726 (95% CI: $342,804-∞) and $199,969 ($157,118-$299,953) accordingly. A total of $819 million worth of IPE can avoid 4762 MACE (95% CI: 0-11,707) versus 20,069 (13,379-25,541), when provided as primary versus secondary prevention therapy; P < .001. The number of avoided MACE is sensitive to IPE price.ConclusionsPrioritizing IPE therapy for patients with an established cardiovascular disease may provide significantly more value for money than primary prevention.  相似文献   
58.

Background:

Food addiction is a debated topic in neuroscience. Evidence suggests diabetes is related to reduced basal dopamine levels in the nucleus accumbens, similar to persons with drug addiction. It is unknown whether insulin sensitivity is related to endogenous dopamine levels in the ventral striatum of humans. We examined this using the agonist dopamine D2/3 receptor radiotracer [11C]-(+)-PHNO and an acute dopamine depletion challenge. In a separate sample of healthy persons, we examined whether dopamine depletion could alter insulin sensitivity.

Methods:

Insulin sensitivity was estimated for each subject from fasting plasma glucose and insulin using the Homeostasis Model Assessment II. Eleven healthy nonobese and nondiabetic persons (3 female) provided a baseline [11C]-(+)-PHNO scan, 9 of which provided a scan under dopamine depletion, allowing estimates of endogenous dopamine at dopamine D2/3 receptor. Dopamine depletion was achieved via alpha-methyl-para-tyrosine (64mg/kg, P.O.). In 25 healthy persons (9 female), fasting plasma and glucose was acquired before and after dopamine depletion.

Results:

Endogenous dopamine at ventral striatum dopamine D2/3 receptor was positively correlated with insulin sensitivity (r(7)=.84, P=.005) and negatively correlated with insulin levels (r(7)=-.85, P=.004). Glucose levels were not correlated with endogenous dopamine at ventral striatum dopamine D2/3 receptor (r(7)=-.49, P=.18). Consistently, acute dopamine depletion in healthy persons significantly decreased insulin sensitivity (t(24)=2.82, P=.01), increased insulin levels (t(24)=-2.62, P=.01), and did not change glucose levels (t(24)=-0.93, P=.36).

Conclusion:

In healthy individuals, diminished insulin sensitivity is related to less endogenous dopamine at dopamine D2/3 receptor in the ventral striatum. Moreover, acute dopamine depletion reduces insulin sensitivity. These findings may have important implications for neuropsychiatric populations with metabolic abnormalities.  相似文献   
59.
BackgroundPatients with dementia and multiple chronic conditions (MCC) frequently experience polypharmacy, increasing their risk of adverse drug events.ObjectivesTo elucidate patient, family, and physician perspectives on medication discontinuation and recommended language for deprescribing discussions in order to inform an intervention to increase awareness of deprescribing among individuals with dementia and MCC, family caregivers and primary care physicians. We also explored participant views on culturally competent approaches to deprescribing.DesignQualitative approach based on semi-structured interviews with patients, caregivers, and physicians.ParticipantsPatients aged ≥ 65 years with claims-based diagnosis of dementia, ≥ 1 additional chronic condition, and ≥ 5 chronic medications were recruited from an integrated delivery system in Colorado and an academic medical center in Maryland. We included caregivers when present or if patients were unable to participate due to severe cognitive impairment. Physicians were recruited within the same systems and through snowball sampling, targeting areas with large African American and Hispanic populations.ApproachWe used constant comparison to identify and compare themes between patients, caregivers, and physicians.Key ResultsWe conducted interviews with 17 patients, 16 caregivers, and 16 physicians. All groups said it was important to earn trust before deprescribing, frame deprescribing as routine and positive, align deprescribing with goals of dementia care, and respect caregivers’ expertise. As in other areas of medicine, racial, ethnic, and language concordance was important to patients and caregivers from minority cultural backgrounds. Participants favored direct-to-patient educational materials, support from pharmacists and other team members, and close follow-up during deprescribing. Patients and caregivers favored language that explained deprescribing in terms of altered physiology with aging. Physicians desired communication tips addressing specific clinical situations.ConclusionsCulturally sensitive communication within a trusted patient-physician relationship supplemented by pharmacists, and language tailored to specific clinical situations may support deprescribing in primary care for patients with dementia and MCC.Electronic supplementary materialThe online version of this article (10.1007/s11606-020-06063-y) contains supplementary material, which is available to authorized users.KEY WORDS: deprescribing, patient-physician communication, dementia  相似文献   
60.
Summary The aim of conducting this study was to assess the clinical relevance of matrix metalloproteinase (MMP) inhibition by doxycycline, an effective MMP inhibitor, in a rat model of extensive myocardial infarction (MI) and left ventricular (LV) dysfunction. Rats (n = 22) were subjected to extensive anterior MI. Doxycycline (25 mg SC, daily) or saline (control) injections were started for nine days thereafter. The effect of doxycycline on MMP activity in the infarcted and remote myocardium was measured by zymography, in another subgroup (n = 8), nine days after MI. Echocardiography and magnetic resonance imaging (MRI) studies were performed at one and thirty days after MI to assess LV remodeling and function. After 4 weeks, hearts were fixed, and subjected to morphometric and histological analysis. Compared with control, doxycycline treatment attenuated MMP-9 and -2 activity in both infarcted and remote myocardium. Serial echocardiography studies showed that doxycycline failed to attenuate scar thinning, LV dilatation and dysfunction. MRI study showed that doxycycline impaired LV compensatory hypertrophy. Furthermore, compared with control, doxycycline reduced vessel density (/mm2 ± SEM) in the infarcted myocardium (84 ± 16 vs. 46 ± 9/mm2, respectively; p < 0.05). Our work suggest that effective MMPs’ inhibition in the infarcted and remote myocardium by doxycycline does not prevent LV remodeling and dysfunction but impairs angiogenesis and compensatory LV hypertrophy. Our findings caution against aggressive, non-selective inhibition of MMPs in the early healing phase after MI.  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