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   25721篇
  免费   1248篇
  国内免费   176篇
耳鼻咽喉   199篇
儿科学   525篇
妇产科学   439篇
基础医学   2816篇
口腔科学   618篇
临床医学   2050篇
内科学   6753篇
皮肤病学   486篇
神经病学   2968篇
特种医学   775篇
外科学   3870篇
综合类   43篇
一般理论   5篇
预防医学   1082篇
眼科学   451篇
药学   1449篇
中国医学   30篇
肿瘤学   2586篇
  2024年   26篇
  2023年   172篇
  2022年   389篇
  2021年   747篇
  2020年   443篇
  2019年   616篇
  2018年   691篇
  2017年   551篇
  2016年   620篇
  2015年   690篇
  2014年   1010篇
  2013年   1268篇
  2012年   1993篇
  2011年   1988篇
  2010年   1155篇
  2009年   1067篇
  2008年   1745篇
  2007年   1804篇
  2006年   1666篇
  2005年   1644篇
  2004年   1626篇
  2003年   1349篇
  2002年   1318篇
  2001年   188篇
  2000年   113篇
  1999年   147篇
  1998年   249篇
  1997年   210篇
  1996年   194篇
  1995年   170篇
  1994年   129篇
  1993年   130篇
  1992年   112篇
  1991年   88篇
  1990年   86篇
  1989年   65篇
  1988年   66篇
  1987年   63篇
  1986年   56篇
  1985年   56篇
  1984年   78篇
  1983年   44篇
  1982年   45篇
  1981年   43篇
  1980年   33篇
  1979年   20篇
  1978年   16篇
  1977年   30篇
  1976年   17篇
  1974年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.

Background

Cancer survival rates are lower in Eastern Europe.

Objectives

To describe, based on a single-centre database in northern Italy, clinical, histopathological, and prognostic features of melanoma in a migrant population from Eastern Europe.

Materials & methods

We retrospectively analysed data from 18,190 consecutive foreign patients who visited our institution, with 49 cases of melanoma from Eastern Europe. The control group was represented by 1,003 Italian melanoma patients diagnosed and followed at our centre during the same time period.

Results

Patients from Eastern Europe were mainly females with lower median age, without significant differences regarding primary melanoma site, relative to the control group. Diagnosiswas made at the place of birth in 30.6% and in our centre for the remainder. Median Breslow thickness was greater (p = 0.0178), and aggressive histotypes (p = 0.0017) and ulcerated melanomas (p = 0.002) were significantly over-represented, particularly when diagnosed in the patients’ native country. Disease was more advanced at diagnosis (p = 0.0001), regardless of the place of initial diagnosis (51% had a progressive disease within one year which rose to 80% if diagnosed before admission to our centre), and the percentage of patients who died within one year was significantly higher (p = 0.022), relative to the control group.

Conclusion

Our study shows a poor prognosis for melanoma patients diagnosed in Eastern Europe. Moreover, for migrant populations moving from Eastern to Western European countries, financial difficulties, poor social integration, and language barriers, with consequent late access to healthcare facilities, may account for a worse prognosis.
  相似文献   
993.

Background

Actinic keratosis (AK) is a common keratinocyte intraepidermal neoplasia.

Objective

To assess AK prevalence and potential risk factors in patients attending Italian general dermatology clinics.

Materials & methods

This retrospective study was conducted on clinical data from consecutive white outpatients aged ≥30 years, attending 24 general dermatology clinics between December 2014 and February 2015. AK prevalence (entire population) and multivariate risk factor analysis (patients with current/previous AK and complete data) are presented.

Results

AK prevalence in 7,284 patients was 27.4% (95% CI: 26.4-28.4%); 34.3% in men and 20.0% in women (p<0.001). Independent AK risk factors in 4,604 patients were: age (OR: 4.8 [95% CI: 3.5-6.5] for 46-60 years, increasing with older age to OR: 41.5 [95% CI: 29.5-58.2] for >70 years), history of other non-melanoma skin cancers (OR: 2.7 [2.2-3.3]), residence in southern Italy/Sardinia (OR: 2.6 [2.1-3.0]), working outdoors >6 hours/day (OR: 1.9 [1.4-2.4]), male gender (OR: 1.7 [1.4-2.0]), facial solar lentigos (OR: 1.6 [1.4-1.9]), light hair colour (OR: 1.5 [1.2-1.8]), prolonged outdoor recreational activities (OR: 1.4 [1.2-1.7]), light eye colour (OR: 1.3 [1.1-1.6]), skin type I/II (OR: 1.3 [1.1-1.6]), and alcohol consumption (OR: 1.2 [1.0-3.3]). BMI ≥25.0 (OR: 0.6 [0.5-0.7]), regular sunscreen use (OR: 0.7 [0.6-0.8]), and a lower level of education (OR: 0.8 [0.7-1.0]) were independent protective factors.

Conclusions

AK prevalence was high in Italian dermatology outpatients. We confirm several well-known AK risk factors and reveal possible novel risk and protective factors. Our results may inform on the design and implementation of AK screening and educational programmes.
  相似文献   
994.
: This study was performed to characterize the dynamic factors determining ventricular interdependence in an open-pericardium intact animal model. Materials and: Simultaneous measures of right ventricular (RV) and left ventricular (LV) pressures and volumes in 6 urethane-anesthetized openchested, open-pericardium rabbits. RV and LV V were calculated every 2 milliseconds. Measurements were made at initial baseline blood volume, and again after two infusions of 20 mL/kg isoconductive colloid solution. At each blood volume level, partial aortic (AO), pulmonary artery (PAO), and inferior vena caval (IVC) occlusions were performed. Biventricular diastolic compliance and end-systolic elastance were calculated from these data.: Baseline end-diastolic (ED) and end-systolic (ES) V were 3.29 ± 0.55 and 2.43 ± 0.33 mL (x ± SD) for the LV, and 3.38 ± 1.56 and 2.84 ± 1.36 mL for the RV, respectively. AO increased all LV pressure and volume (P < .05) but did not alter RV ED volume (2.85 ± 1.20 mL) or ED pressure (3.3 ± 2.0 to 3.6 ± 2.1 mm Hg). PAO increased RV ES pressure (P < .05) but did not alter RV ED volume, ED pressure, or ES volume, although it decreased LV ED volume (2.82 ± 0.59, P < .05). AO also immediately increased end-systolic RV elastance to a value greater than that defined by IVC (7.9 ± 4.4 to 10.9 ± 6.6 mm Hg/mL, P < .05). Intravascular volume expansion though increasing baseline pressure and volume, did not alter qualitatively biventricular responses to AO, PA, or IVC.: Ventricular interdependence has both systolic and diastolic components that have differing directional effects. In the pericardectomized rabbit, increases in RV ED volume decrease LV ED volume by decreasing LV diastolic compliance, but do not alter LV systolic function. Whereas, increases in LV ED volume decrease RV ES volume resulting in an increase in RV maximal elastance, but minimally alter RV diastolic function.  相似文献   
995.
The laparoscopic approach has represented a major step forward in general and emergency surgery. Its application in the emergency setting still raises a number of concerns that limit its more widespread use. To assess the true scope of laparoscopic surgery in the acute abdominal setting, we retrospectively evaluated our experience. From February 2003 to June 2007, 314 patients underwent an emergency laparoscopic operation, for low abdominal pain (193 patients), acute cholecystitis (78 patients), bowel obstruction (18 patients), diffuse peritonitis (16 patients), blunt abdominal trauma (6 patients), and acute pancreatitis (3 patients). Laparoscopy yielded a good diagnostic definition in all cases. The conversion rate was 16.6% (52 patients). Mean operative time was 63 +/- 29 minutes. The general major morbidity rate was 1.5% (4 patients) and the mortality rate was 0.4% (1 pt.). The laparoscopic approach in patients with abdominal emergencies is a useful tool that yields a reliable diagnostic definition in uncertain cases and allows minimal access treatment of the causative disease in the majority of cases.  相似文献   
996.
Dendritic cells (DCs) are the most potent antigen-presenting cells, yet little data are available on the differential characteristics of donor and recipient DCs (dDCs and rDCs, respectively) during the process of islet allograft rejection. DTR-GFP-DC mice provide a novel tool to monitor DC trafficking and characteristics during allograft rejection. We show rapid migration of dDCs to recipient lymphoid tissues as early as 3 h post-islet allotransplantation. Compared with rDCs, dDCs express different patterns of chemokine receptors, display differential proliferative capacity, and exhibit a higher level of maturity; these findings could be attributed to the effects of injury that dDCs undergo during islet cell preparation and engraftment. Intriguingly, we detected dDCs in the spleen of recipients long after rejection of islet allografts. Given that dDCs express high levels of CCR7, islets were cultured before transplant with the ligand for CCR7 (CCL21). This novel method, which enabled us to enhance the efflux of dDCs from islet preparations, resulted in a prolongation of islet allograft survival in immunocompetent recipients. This study introduces dDCs and rDCs as two distinct types of DCs and provides novel data with clinical implications to use chemokine-based DC-depleting strategies to prolong islet allograft survival.  相似文献   
997.
Abdi R  Fiorina P  Adra CN  Atkinson M  Sayegh MH 《Diabetes》2008,57(7):1759-1767
Mesenchymal stem cells (MSCs) are pluripotent stromal cells that have the potential to give rise to cells of diverse lineages. Interestingly, MSCs can be found in virtually all postnatal tissues. The main criteria currently used to characterize and identify these cells are the capacity for self-renewal and differentiation into tissues of mesodermal origin, combined with a lack in expression of certain hematopoietic molecules. Because of their developmental plasticity, the notion of MSC-based therapeutic intervention has become an emerging strategy for the replacement of injured tissues. MSCs have also been noted to possess the ability to impart profound immunomodulatory effects in vivo. Indeed, some of the initial observations regarding MSC protection from tissue injury once thought mediated by tissue regeneration may, in reality, result from immunomodulation. Whereas the exact mechanisms underlying the immunomodulatory functions of MSC remain largely unknown, these cells have been exploited in a variety of clinical trials aimed at reducing the burden of immune-mediated disease. This article focuses on recent advances that have broadened our understanding of the immunomodulatory properties of MSC and provides insight as to their potential for clinical use as a cell-based therapy for immune-mediated disorders and, in particular, type 1 diabetes.  相似文献   
998.
In rabbits undergoing peritoneal dialysis, hypertonic (6% dextrose) dialysis solution increased the net ultrafiltration rate (UF) from 233 to 462 microL/kg/min, which was not proportional to the increment in the osmotic gradient, so the ultrafiltration coefficient decreased. As intraperitoneal dwell of hypertonic dialysate was prolonged, the gross and net UFs and ultrafiltration coefficients decreased, and the UF per dextrose absorption declined. The decrement in UF was multifactorial, including a component of fluid and solute stagnation, increasing the distance over which osmotic forces must exert their effects. Excessively hypertonic dialysis fluid should be used only briefly to achieve ultrafiltration efficiently and to avoid the high dextrose loading.  相似文献   
999.
We report a case of a rare neurological tumour arising in the knee joint with no apparent connection to the major nerve trunks in the area. After the patient failed to improve through rehabilitation, surgery was performed, revealing a concomitant tear of the medial meniscus as well as a mass which was excised through an external supero-medial incision into the knee. Histopathological analysis later confirmed the diagnosis of a neurilemoma.  相似文献   
1000.
Pericyte-mediated capillary constriction decreases cerebral blood flow in stroke after an occluded artery is unblocked. The determinants of pericyte tone are poorly understood. We show that a small rise in cytoplasmic Ca2+ concentration ([Ca2+]i) in pericytes activated chloride efflux through the Ca2+-gated anion channel TMEM16A, thus depolarizing the cell and opening voltage-gated calcium channels. This mechanism strongly amplified the pericyte [Ca2+]i rise and capillary constriction evoked by contractile agonists and ischemia. In a rodent stroke model, TMEM16A inhibition slowed the ischemia-evoked pericyte [Ca2+]i rise, capillary constriction, and pericyte death; reduced neutrophil stalling; and improved cerebrovascular reperfusion. Genetic analysis implicated altered TMEM16A expression in poor patient recovery from ischemic stroke. Thus, pericyte TMEM16A is a crucial regulator of cerebral capillary function and a potential therapeutic target for stroke and possibly other disorders of impaired microvascular flow, such as Alzheimer’s disease and vascular dementia.  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