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   3669篇
  免费   193篇
  国内免费   34篇
耳鼻咽喉   30篇
儿科学   35篇
妇产科学   280篇
基础医学   373篇
口腔科学   129篇
临床医学   333篇
内科学   857篇
皮肤病学   44篇
神经病学   332篇
特种医学   228篇
外科学   550篇
综合类   10篇
一般理论   1篇
预防医学   128篇
眼科学   108篇
药学   129篇
中国医学   1篇
肿瘤学   328篇
  2024年   11篇
  2023年   33篇
  2022年   86篇
  2021年   157篇
  2020年   91篇
  2019年   113篇
  2018年   134篇
  2017年   77篇
  2016年   108篇
  2015年   103篇
  2014年   145篇
  2013年   177篇
  2012年   261篇
  2011年   271篇
  2010年   172篇
  2009年   137篇
  2008年   215篇
  2007年   244篇
  2006年   186篇
  2005年   217篇
  2004年   162篇
  2003年   155篇
  2002年   107篇
  2001年   58篇
  2000年   42篇
  1999年   41篇
  1998年   28篇
  1997年   27篇
  1996年   25篇
  1995年   19篇
  1994年   16篇
  1993年   9篇
  1992年   35篇
  1991年   26篇
  1990年   20篇
  1989年   23篇
  1988年   23篇
  1987年   21篇
  1986年   10篇
  1985年   17篇
  1984年   17篇
  1983年   10篇
  1982年   8篇
  1981年   7篇
  1979年   9篇
  1974年   8篇
  1973年   5篇
  1972年   3篇
  1970年   3篇
  1969年   3篇
排序方式: 共有3896条查询结果,搜索用时 15 毫秒
101.
PurposeTo compare patterns of choroidal venous drainage in eyes with pachychoroid disease to those of healthy subjects using ultra-widefield indocyanine green angiography (UWF ICGA).MethodsPatients with pachychoroid disease and healthy controls were recruited at two referral centers. UWF ICGA images were used to evaluate the proportion of the postequatorial fundus drained by major vortex vein systems in each quadrant and to study the incidence and topography of choroidal vascular hyperpermeability (CVH) and intervortex venous anastomoses. Widefield swept-source optical coherence tomography (SS-OCT) was used to evaluate choroidal thickness at the posterior pole in eyes with pachychoroid disease.ResultsFifty-two pachychoroid eyes and 26 healthy eyes were evaluated. Eyes with pachychoroid disease showed a significant within-subject variance in the proportion of the postequatorial fundus drained by each vortex vein system (range, 4.1%–48.1%; P < 0.0001) that was not seen in controls (range, 17.3%–31.7%; P = 0.11). CVH was present in all pachychoroid disease eyes and three of 26 controls. Intervortex venous anastomoses were present in 46 of 52 pachychoroid disease eyes and nine of 26 control eyes. Vortex vein systems with large drainage areas showed greater density of CVH spots. SS-OCT demonstrated asymmetric choroidal drainage in the macula of 59% of pachychoroid eyes. CVH and intervortex venous anastomoses were more prominent in areas showing maximal choroidal thickness.ConclusionsIn eyes with pachychoroid disease, imbalanced choroidal venous drainage with congestion of specific vortex vein systems may contribute to a state of choroidal venous insufficiency characterized by regional choroidal thickening, CVH and remodeling of venous drainage routes.  相似文献   
102.
Obesity is common in psoriatic patients, and it has been shown to be important for many aspects of the condition. In particular, low-calorie diets can improve the symptoms and response to treatment in pustular psoriasis. The present study investigates the influence of body-weight alteration on the disease's clinical manifestations in moderate to severe psoriasis patients treated with biological drugs. Finally, the influence of a caloric restriction was assessed. This observational transversal study enrolled 33 patients attending our Severe Psoriasis Outpatient Clinic, who were treated with biological drugs. Body Mass Index (BMI) was used as a diagnostic indicator of being overweight and of obesity. Waist circumference was also measured. Body weight and Psoriasis Area Severity Index (PASI) index were measured at follow-up visits at 4 and 8 months. Nonparametric test of Mann–Whitney was used to detect the differences between patient groups. Fisher's exact test was performed to evaluate the different results depending on the therapeutic changes of BMI. There was a strong prevalence of overweight-obese individuals in the group with a mean BMI of 30.59 ± 6.94. Waist circumference was also above normal in the majority of the patients. Obese patients had a PASI index higher than the average of the whole group (25.03 ± 12.43), with grade III obese patients having an average PASI of 44 ± 3.37. At the first and second follow-ups, patients who put on weight did not achieve PASI 50; patients who had a stable weight presented variable response to treatment, while patients who decreased their weight achieved PASI 90 or PASI 75 even when not responding at the first. Further studies are needed to understand if the poor response observed in heavier patients is due to biological drugs pharmacokinetics or because therapy should be BMI based rather than administered in fixed doses, posing then an ethical consideration.  相似文献   
103.
104.

Objective

The detectability of high frequency oscillations (HFO, >200 Hz) in the intraoperative ECoG is restricted by their low signal-to-noise ratio (SNR). Using the somatosensory evoked HFO, we quantify how HFO detectability can benefit from a custom-made low-noise amplifier (LNA).

Methods

In 9 patients undergoing tumor surgery in the central region, subdural strip electrodes were placed for intraoperative neurophysiological monitoring. We recorded the somatosensory evoked potential (SEP) simultaneously by custom-made LNA and by a commercial device (CD). We varied the stimulation rate between 1.3 and 12.7 Hz to tune the SNR of the N20 component and the evoked HFO and quantified HFO detectability at the single trial level. In three patients we compared Propofol® and Sevoflurane® anesthesia.

Results

In the average, amplitude decreased in both in N20 and evoked HFO amplitude with increasing stimulation rate (p < 0.05). We detected a higher percentage of single trial evoked HFO with the LNA (p < 0.001) for recordings with low impedance (<5 kΩ). Average amplitudes were indistinguishable between anesthesia compounds.

Conclusion

Low-noise amplification improves the detection of the evoked HFO in recordings with subdural electrodes with low impedance.

Significance

Low-noise EEG might critically improve the detectability of interictal spontaneous HFO in subdural and possibly in scalp recordings.  相似文献   
105.
Neurological Sciences - To study for the first time the incidence of adult-onset CNS tumors in Southern Sardinia, Italy. Clinical records of patients &gt; 18&nbsp;years old who...  相似文献   
106.
Background: A facial bone (<2 mm) overlying maxillary anterior teeth may be prone to resorptive processes after extraction and immediate implant placement. A thin bone contributes to risk of bone fenestration, dehiscence, and soft‐tissue recession. This study measures the distance between the cemento‐enamel junction (CEJ) and alveolar bone crest and the thickness of facial alveolar bone at points 1 to 5 mm from the bone crest for the six maxillary anterior teeth. Methods : Sixty‐six tomographic scans (31 males and 35 females; aged 17 to 69 years; mean age: 39.9 years) of intact anterior maxilla were randomly selected and evaluated by two calibrated and independent examiners (MG and TP). Results: A high variation of CEJ–bone crest (0.8 to 7.2 mm) was detected. A significantly larger CEJ–bone crest was measured in smokers (P <0.05) and patients who were ≥50 years old (P <0.05). The average bone thickness at 3 mm from the CEJ for the maxillary right central incisor was 1.41 mm and for the maxillary left central incisor was 1.45 mm. For the maxillary right and left lateral incisors, the crestal bone thickness averaged 1.73 and 1.59 mm, respectively. For the maxillary right and left canines, the crestal bone thickness averaged 1.47 and 1.60 mm, respectively. Conclusions : The present study supports the finding of a predominantly thin facial bone overlying the six maxillary anterior teeth. Therefore, it is essential to make informed treatment decisions based on thorough site evaluation before immediate implant placement.  相似文献   
107.

Background

The presence of defects at stress-redistribution thallium-201 scintigraphy is related to a higher risk of cardiac events. However, the prognostic value of defects that become reversible after reinjection is not known. In this study we evaluated the prognostic contribution of stress-redistribution-reinjection with special regard to 3-hour fixed defects that become reversible after reinjection.

Methods and Results

We studied 122 patients with chronic myocardial infarction (>2 months) and suspected or known residual ischemia, with stress-redistribution-reinjection planar scintigraphy. Thallium scans were analyzed by three observers (three segments per view, 5-point score) and classified as normal, fixed, and reversible. The lung/heart ratio was also calculated. At a median follow-up of 47 months, 10 patients had hard events (four deaths and six myocardial infarctions) (group I), 12 patients had unstable angina (group II), 12 patients underwent planned coronary artery bypass grafting or percutaneous transluminal coronary angioplasty (group III), and 86 patients had no events (group IV). The presence of fixed defects that became reversible after reinjection did not identify patients at higher risk. The number of reversible defects at 3 hours was significantly higher only in patients who underwent revascularization. Unstable angina was not predicted by any scintigraphic pattern. The variables that were statistically related to hard events by univariate analysis were increased lung uptake, reversible cavity dilation, and the number of fixed defects that remained fixed after reinjection. By Cox multivariate analysis, the strongest predictor of hard events was the presence of more than three fixed defects that remained fixed after reinjection as a marker of irreversible myocardial damage.

Conclusions

201TI reinjection is a useful approach for not only detecting viable myocardium but also risk stratification in patients with chronic myocardial infarction.  相似文献   
108.
BACKGROUND: Radiofrequency ablation (RFA) is a novel technique for the treatment of liver malignancies that is becoming increasingly more popular because of its feasibility, effectivity, repeatability, and safety. However, an increased number of complications after RFA has been reported in literature. The aim of this paper is to discuss the possible role of RFA in rapid intrahepatic spreading of hepatocellular carcinoma (HCC). PATIENTS AND METHODS: We treated a 66-year-old woman who had a 3.5-cm HCC with two courses of percutaneous RFA using a modified needle with seven hooks. The effectiveness of the treatment was assessed 1 month later by enhanced computed tomography. RESULTS: Two courses of treatment were needed owing to the nodule position (close to the inferior vena cava). Computed tomography scan performed 1 month after the second RFA showed an intrahepatic arteriovenous fistula. Angiography performed after 1 month showed a rapid intrahepatic spreading of HCC. CONCLUSIONS: Radiofrequency ablation can create an arteriovenous fistula that can facilitate migration of tumoral cells from the nodule to the hepatic portal system and rapid intrahepatic dissemination of HCC.  相似文献   
109.
BackgroundThe discovery of the prominent action of Calcitonin Gene Related Peptide –CGRP- on trigeminal afferents and meningeal vessels, opened a new era in migraine treatment. However, how the block of nociceptive afferents could act on central mechanisms of migraine is still not clear. In this pilot study we aimed to test the effect of 3 months Galcanezumab (CGA) therapy on occipital visual reactivity in migraine patients, using the Steady State Visual Evoked Potentials-SSVEPs and Functional Near Infrared Spectroscopy –fNIRS.MethodThirteen migraine patients underwent clinical and neurophysiological examination in basal condition (T0), 1 h after GCA injection (T1) and after 3 months of GCA treatment (T2). Ten healthy volunteers were also evaluated.ResultsAt T2, there was a reduction of headache frequency and disability. At T2, the EEG power significantly diminished as compared to T0 and T1 at occipital sites, and the topographical analysis confirmed a restoration of SSVEPs within normal values. The Oxyhemoglobin levels in occipital cortex, which were basically increased during visual stimulation in migraine patients, reverted to normal values at T2.ConclusionsThe present pilot study indicates that Galcanezumab could act on cortical targets located beyond the pain network, restoring the abnormal occipital reactivity. This effect could indicate the possible disease modifying properties of CGRP related monoclonal antibodies.  相似文献   
110.
Objectives

Tooth clenching has been suggested to be related to temporomandibular pain. However, the electromyographic characteristics of daytime clenching episodes have been minimally investigated. This study aimed to analyze the frequency, amplitude, and duration of daytime clenching episodes in patients with masticatory muscle pain and pain-free individuals.

Methods

Fifteen women with masticatory muscles myalgia (MP group, mean ± SD age = 26.4 ± 7.6 years) matched for age to 18 pain-free women (CTR group, mean ± SD age = 25.3 ± 2.8 years) were submitted to three different ability tasks (filling out questionnaires for 40 min, reading for 20 min, and playing a videogame for 20 min). The electromyographic activity periods (AP) of the right masseter greater than 10 % (AP10), 20 % (AP20), and 30 % (AP30) of the maximum voluntary contraction were analyzed.

Results

The mean frequencies of AP10, AP20, and AP30 were greater in MP than in CTR individuals (all p < 0.05). The mean duration of AP10 was higher in MP group than CTR group only while filling out the questionnaires (p = 0.0033). CTR group had an increased frequency and duration of AP10 while playing the videogame than while reading a magazine. The ability tasks did not affect the muscle activity in the MP group.

Conclusions

Individuals with masticatory muscle pain have an increased frequency of both high and low-intense daytime clenching episodes. The type of ability task affects the frequency and the duration of clenching episodes only in pain-free individuals.

Clinical relevance

Clinicians should recognize that the frequency and intensity of daytime clenching are noticeably increased in individuals with masticatory muscle pain in order to better tailor treatment.

  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