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   4342篇
  免费   189篇
  国内免费   12篇
耳鼻咽喉   103篇
儿科学   192篇
妇产科学   210篇
基础医学   677篇
口腔科学   31篇
临床医学   260篇
内科学   980篇
皮肤病学   69篇
神经病学   384篇
特种医学   69篇
外科学   186篇
综合类   26篇
预防医学   371篇
眼科学   112篇
药学   578篇
中国医学   13篇
肿瘤学   282篇
  2024年   7篇
  2023年   31篇
  2022年   203篇
  2021年   302篇
  2020年   104篇
  2019年   134篇
  2018年   142篇
  2017年   129篇
  2016年   152篇
  2015年   153篇
  2014年   200篇
  2013年   283篇
  2012年   361篇
  2011年   371篇
  2010年   197篇
  2009年   147篇
  2008年   233篇
  2007年   304篇
  2006年   272篇
  2005年   255篇
  2004年   187篇
  2003年   184篇
  2002年   143篇
  2001年   12篇
  2000年   4篇
  1999年   3篇
  1998年   5篇
  1997年   10篇
  1996年   6篇
  1995年   4篇
  1992年   1篇
  1988年   1篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
排序方式: 共有4543条查询结果,搜索用时 15 毫秒
81.
Infections caused by the spirochete Borrelia burgdorferi sensu lato may be accompanied by other microorganisms, such as Anaplasma, Ehrlichia and Babesia. These pathogens are transmitted by the ticks and are a risk to humans and animals. Ixodes ricinus ticks collected from recreational areas of Szczecin and northwestern Poland contained DNA of the pathogens mentioned above and cases of double and triple coinfection have been documented. The aim of this paper was to determine if dogs suspect to tick infestation in the area of study are a reservoir for these pathogens and to examine the possibility of coinfection. Canine blood was sampled, part of the material originated from dogs exhibiting symptoms of borreliosis. In an earlier study, the samples were screened for DNA from B. burgdorferi sensu lato. In order to screen for A. phagocytophila and Babesia sp. DNA, a PCR-based method was used with the following primers: EHR521/EHR747 for Anaplasma and FOR1/REV1 for Babesia. In 192 samples only two contained A. phagocytophila DNA. One of these samples originated from a healthy canine, the other from an individual with symptoms of borreliosis. The examined samples were not positive for Babesia sp. DNA. Coinfection was not discovered. The low level of A. phagocytophila infection may indicate that the domestic dog is not a reservoir for Anaplasma and Babesia in Szczecin and northwestern Poland. Moreover, this area does not have populations of the brown dog tick (Rhipicephalus sanguineus) or Dermacentor reticulates--both of which are vectors of E. canis and B. canis and commonly induce ehrlichiosis and babesiosis in canines.  相似文献   
82.
83.
Here we report a patient with 11p15.4p15.5 duplication and 13q34 deletion presenting with Beckwith–Wiedemann syndrome (BWS) and moderate deficiency of factor VII (FVII). The duplication was initially diagnosed on methylation‐sensitive multiplex ligation‐dependent probe amplification. Array comparative genome hybridization confirmed its presence and indicated a 13q34 distal deletion. The patient's clinical symptoms, including developmental delay and facial dysmorphism, were typical of BWS with paternal 11p15 trisomy. Partial 13q monosomy in this patient is associated with moderate deficiency of FVII and may also overlap with a few symptoms of paternal 11p15 trisomy such as developmental delay and some facial features. To our knowledge this is the first report of 11p15.4p15.5 duplication associated with deletion of 13q34 and FVII deficiency. Moreover, this report emphasizes the importance of detailed clinical as well as molecular examinations in patients with BWS features and developmental delay.  相似文献   
84.
AIMS: Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a nuclear receptor regulating cardiac metabolism that also has anti-inflammatory properties. Since the activation of inflammatory signalling pathways is considered to be important in cardiac hypertrophy and fibrosis, it is anticipated that PPARalpha modulates cardiac remodelling. Accordingly, in this study the hypothesis was tested that the absence of PPARalpha aggravates the cardiac hypertrophic response to pressure overload. METHODS AND RESULTS: Male PPARalpha-/- and wild-type mice were subjected to transverse aortic constriction (TAC) for 28 days. TAC resulted in a more pronounced increase in ventricular weight and left ventricular (LV) wall thickness in PPARalpha-/- than in wild-type mice. Compared with sham-operated mice, TAC did not affect cardiac function in wild-type mice, but significantly depressed LV ejection fraction and LV contractility in PPARalpha-/- mice. Moreover, after TAC mRNA levels of hypertrophic (atrial natriuretic factor, alpha-skeletal actin), fibrotic (collagen 1, matrix metalloproteinase-2), and inflammatory (interleukin-6, tumour necrosis factor-alpha, cyclo-oxygenase-2) marker genes were higher in PPARalpha-/- than in wild-type mice. The mRNA levels of genes involved in fatty acid metabolism (long-chain acyl-CoA synthetase, hydroxyacyl-CoA dehydrogenase) were decreased in PPARalpha-/- mice, but were not further compromised by TAC. CONCLUSION: The present findings show that the absence of PPARalpha results in a more pronounced hypertrophic growth response and cardiac dysfunction that are associated with an enhanced expression of markers of inflammation and extracellular matrix remodelling. These findings indicate that PPARalpha exerts salutary effects during cardiac hypertrophy.  相似文献   
85.
Modification of ultrasmall gold nanoparticles (AuNPs) with the lipoic acid derivative of folic acid was found to enhance their accumulation in the cancer cell, as compared to AuNPs without addressing units. The application of lipoic acid enabled the control of the gold nanoparticle functionalities leading to enhanced solubility and allowing for attachment of both the folic acid and the cytotoxic drug, doxorubicin. More robust attachment of doxorubicin to the nanoparticle through the amide bond resulted in toxicity comparable with that of the drug alone, opening a new perspective for designing more potent, but less toxic nanopharmaceuticals. The increased uptake was accompanied by pronounced nuclear accumulation and observable cytotoxicity. Doxorubicin binding via covalent amide bonds enhanced stability of the whole drug vehicle and provided much better control over doxorubicin release in the cell environment, as compared to physical adsorption or pH sensitive bonding commonly used for anthracycline carriers. Confocal microscopy revealed that the bond was stable in the cytoplasm for 22 h. The ability to slow down the rate of drug release may be crucial for the application in sustained anticancer drug delivery. Biological analyses performed using MTT assay and confocal microscopy confirmed that the ultrasmall AuNPs with the lipoic acid derivative of folic acid exhibit relatively low cytotoxicity, however when loaded with a chemotherapeutic, they cause a significant reduction in the cell viability.

Modification of ultrasmall gold nanoparticles (AuNPs) with the lipoic acid derivative of folic acid was found to enhance their accumulation in the cancer cell, as compared to AuNPs without addressing units.  相似文献   
86.
Purpose: To detect any improvement of awareness in prolonged disorders of consciousness in the long term.

Methods: A total of 34 patients with prolonged disorders of consciousness (27 vegetative state and seven minimally conscious state; 16 males; aged 21–73) were included in the study. All patients were initially diagnosed with vegetative/minimally conscious state on admission to our specialist neurological rehabilitation unit. Re-assessment was performed 2–16?years later using Coma Recovery Scale-Revised.

Results: Although remaining severely disabled, 32% of the patients showed late improvement of awareness evidenced with development of non-reflexive responses such as reproducible command following and localization behaviors. Most of the late recoveries occurred in patients with subarachnoid hemorrhage (5/11, 45.5%). The ages of patients within the late recovery group (Mean?=?45, SD?=?11.4) and non-recovery group (Mean?=?43, SD?=?15.5) were not statistically different (p?=?0.76).

Conclusions: This study shows that late improvements in awareness are not exceptional in non-traumatic prolonged disorders of consciousness cases. It highlights the importance of long-term follow up of patients with prolonged disorders of consciousness, regardless of the etiology, age, and time passed since the brain injury. Long-term follow up will help clinicians to identify patients who may benefit from further assessment and rehabilitation. Although only one patient achieved recovery of function, recovery of awareness may have important ethical implications especially where withdrawal of artificial nutrition and hydration is considered.

  • Implications for rehabilitation
  • Long-term regular follow-up of people with prolonged disorders of consciousness is important.

  • Albeit with poor functional outcomes late recovery of awareness is possible in both traumatic and non-traumatic prolonged disorders of consciousness cases.

  • Recovery of awareness has significant clinical and ethical implications especially where withdrawal of artificial nutrition and hydration is considered.

  相似文献   
87.

Purpose

We report here a unique case of a sudden loss of vision as the first symptom of an advanced chronic nephropathy.

Methods and Results

A 25-year-old man was referred to the Department of Ophthalmology with sudden visual deterioration presumptively diagnosed as bilateral retinitis. The patient had never been under any medical care before and had never had any clinical signs of any chronic disease. He underwent an ophthalmic examination with optical coherence tomography (OCT). Based on the clinical features, OCT scans and systemic blood pressure (BP) assessment (225/145 mm Hg), the patient was definitely diagnosed with hypertensive retinopathy and choroidopathy due to hypertensive crisis. After urgent diagnostic procedures, the patient was diagnosed with a chronic kidney disease at stage 5 in the course of chronic glomerulonephritis. Immediately, a renal replacement therapy was started and the patient was qualified for renal transplantation.

Conclusion

Adolescents with an unclear picture of retinal lesions, who have neither a history nor clinical signs of a systemic disease, should undergo careful systemic screening with BP assessment. A sudden deterioration of vision may be the first symptom of a previously undiagnosed severe systemic disease (very rare chronic) that requires immediate treatment.Key Words: Hypertensive crisis, Hypertensive choroidopathy, Hypertensive retinopathy, Chronic renal failure  相似文献   
88.

Purpose

To describe total fluid intake (TFI) according to socio-demographic characteristics in children and adolescents worldwide.

Methods

Data of 3611 children (4–9 years) and 8109 adolescents (10–18 years) were retrieved from 13 cross-sectional surveys (47 % males). In three countries, school classes were randomly recruited with stratified cluster sampling design. In the other countries, participants were randomly recruited based on a quota method. TFI (drinking water and beverages of all kinds) was obtained with a fluid-specific record over 7 consecutive days. Adequacy was assessed by comparing TFI to 80 % of adequate intake (AI) for total water intake set by European Food Safety Authority. Data on height, weight and socio-economic level were collected in most countries.

Results

The mean (SD) TFI ranged from [1.32 (0.68)] to [1.35 (0.71)] L/day. Non-adherence to AIs for fluids ranged from 10 % (Uruguay) to >90 % (Belgium). Females were more likely to meet the AIs for fluids than males (4–9 years: 28 %, OR 0.72, p = 0.002; 10–18 years: 20 %, OR 0.80, p = 0.001), while adolescents were less likely to meet the AI than children (OR 1.645, p < 0.001 in males and OR 1.625, p < 0.001 in females).

Conclusions

A high proportion of children and adolescents are at risk of an inadequate fluid intake. This risk is especially high in males and adolescents when compared with females or children categories. This highlights water intake among young populations as an issue of global concern.
  相似文献   
89.
Weight loss from exercise-induced energy deficits is usually less than expected. The objective of this systematic review was to investigate predictors of energy compensation, which is defined as body energy changes (fat mass and fat-free mass) over the total amount of exercise energy expenditure. A search was conducted in multiple databases without date limits. Of 4745 studies found, 61 were included in this systematic review with a total of 928 subjects. The overall mean energy compensation was 18% ± 93%. The analyses indicated that 48% of the variance of energy compensation is explained by the interaction between initial fat mass, age and duration of exercise interventions. Sex, frequency, intensity and dose of exercise energy expenditure were not significant predictors of energy compensation. The fitted model suggested that for a shorter study duration, lower energy compensation was observed in younger individuals with higher initial fat mass (FM). In contrast, higher energy compensation was noted for younger individuals with lower initial FM. From 25 weeks onward, energy compensation was no longer different for these predictors. For studies of longer duration (about 80 weeks), the energy compensation approached 84%. Lower energy compensation occurs with short-term exercise, and a much higher level of energy compensation accompanies long-term exercise interventions.  相似文献   
90.
Heart Failure Reviews - Few millions of new cancer cases are diagnosed worldwide every year. Due to significant progress in understanding cancer biology and developing new therapies, the mortality...  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