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   14917篇
  免费   929篇
  国内免费   93篇
耳鼻咽喉   131篇
儿科学   320篇
妇产科学   875篇
基础医学   1895篇
口腔科学   311篇
临床医学   1684篇
内科学   3145篇
皮肤病学   276篇
神经病学   1141篇
特种医学   420篇
外科学   1987篇
综合类   282篇
一般理论   8篇
预防医学   796篇
眼科学   425篇
药学   1066篇
中国医学   126篇
肿瘤学   1051篇
  2023年   67篇
  2022年   198篇
  2021年   356篇
  2020年   156篇
  2019年   312篇
  2018年   415篇
  2017年   250篇
  2016年   280篇
  2015年   440篇
  2014年   538篇
  2013年   754篇
  2012年   1100篇
  2011年   1170篇
  2010年   743篇
  2009年   601篇
  2008年   864篇
  2007年   864篇
  2006年   827篇
  2005年   797篇
  2004年   724篇
  2003年   636篇
  2002年   608篇
  2001年   549篇
  2000年   526篇
  1999年   376篇
  1998年   108篇
  1997年   100篇
  1996年   91篇
  1995年   78篇
  1994年   66篇
  1993年   54篇
  1992年   181篇
  1991年   152篇
  1990年   116篇
  1989年   112篇
  1988年   105篇
  1987年   82篇
  1986年   71篇
  1985年   62篇
  1984年   46篇
  1983年   32篇
  1982年   25篇
  1981年   23篇
  1980年   18篇
  1979年   43篇
  1978年   24篇
  1977年   22篇
  1976年   20篇
  1975年   24篇
  1973年   25篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
991.
The purpose of the present study was to examine the effect of the long-term administration of human atrial natriuretic peptide (ANP) on testosterone production in male mice. Twenty-five mice received ANP (20 ng/hour/g body weight) for 7 days via mini-osmotic pump, and the other group (n = 25) received twice-daily intraperitoneal injections. After death, levels of follicle-stimulating hormone, luteinizing hormone (LH), and testosterone in plasma, pituitary gland, and testis were measured by radioimmunoassay. Five mice from each group were examined histologically. In the minipump group, pituitary and plasma levels were significantly higher than those in the control group (771.2 +/- 43.6 vs 644.8 +/- 24.9 ng/mg and 6.7 +/- 0.6 ng/mg vs 2.5 +/- 0.6 ng/mL, respectively). In the intraperitoneal group, plasma LH levels were significantly higher in the ANP-treated group than that in control mice (9.6 +/- 0.3 ng/mg vs 3.8 +/- 0.5 ng/mL), whereas pituitary levels did not differ significantly. In both studies, testicular and plasma testosterone levels were significantly lower than those in control mice (P <.02). Histological features of the testes in ANP-treated mice revealed structural disorganization and inhibition of spermatogenesis. We conclude that the chronic administration of ANP may result in reduced testosterone production due to testicular damage.  相似文献   
992.
The aim of this study was to assess changes in L-3, 4-dihydroxyphenylalanine (L-DOPA) biotransformation in response to two-pulse infusion of L-DOPA into the striatum of freely-moving young (3-4 month) and old (21-26 month) male Wistar rats. In addition, the effects of L-DOPA infusion on the vesicular dopamine (DA) store in young rats were also studied. Both L-DOPA-induced DA overflow and uptake of the perfused L-DOPA by the striatum were used to study L-DOPA biotransformation during microdialysis. High potassium-induced DA depletion was performed to assess the dynamics of the vesicular DA store following L-DOPA infusion. Concentric microdialysis probes were stereotaxically implanted in the lateral striatum of rats of both age groups and microdialysis was begun 24 h later. All rats received 2x20 min infusions of 3 mgr L-DOPA separated by an interval of 60 min. In the striatum of both groups, L-DOPA-induced DA overflow and uptake of exogenous L-DOPA were both significantly enhanced during the second infusion compared to the first. In young rats, when a 20-min infusion of 3 mgr L-DOPA was given between 2x20 min infusions of 100 mM potassium, no increased DA release was seen at the second high potassium challenge compared with the first. Our results suggest that the enhancement of DA overflow induced by the second L-DOPA infusion is, at least partially, due to an increase in L-DOPA biotransformation, and not simply to an enlarged DA pool. In contrast to the in vitro results, our own in vivo results show that L-DOPA utilization in the aging striatum does not deteriorate with age.  相似文献   
993.
Atypical hemolytic uremic syndrome commonly presents with the triad of microangiopathic hemolytic anemia, thrombocytopenia, and renal function impairment without an antecedent hemorrhagic diarrhea. Less known are extrarenal complications due to abnormal vascular permeability, although these are a major cause of morbidity and mortality for the patients. Furthermore, it is increasingly recognized that the disease may present with hypertension or renal function impairment with no or mild thrombocytopenia and microangiopathic hemolytic anemia. Awareness of the full spectrum of atypical hemolytic uremic syndrome may facilitate its diagnosis and treatment before serious complications or death occurs.  相似文献   
994.
995.
996.

Introduction

Sepsis is the leading cause of acute kidney injury (AKI) in critical patients. The optimal timing of initiating renal replacement therapy (RRT) in septic AKI patients remains controversial. The objective of this study is to determine the impact of early or late initiation of RRT, as defined using the simplified RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification (sRIFLE), on hospital mortality among septic AKI patients.

Methods

Patient with sepsis and AKI requiring RRT in surgical intensive care units were enrolled between January 2002 and October 2009. The patients were divided into early (sRIFLE-0 or -Risk) or late (sRIFLE-Injury or -Failure) initiation of RRT by sRIFLE criteria. Cox proportional hazard ratios for in hospital mortality were determined to assess the impact of timing of RRT.

Results

Among the 370 patients, 192 (51.9%) underwent early RRT and 259 (70.0%) died during hospitalization. The mortality rate in early and late RRT groups were 70.8% and 69.7% respectively (P > 0.05). Early dialysis did not relate to hospital mortality by Cox proportional hazard model (P > 0.05). Patients with heart failure, male gender, higher admission creatinine, and operation were more likely to be in the late RRT group. Cox proportional hazard model, after adjustment with propensity score including all patients based on the probability of late RRT, showed early dialysis was not related to hospital mortality. Further model matched patients by 1:1 fashion according to each patient's propensity to late RRT showed no differences in hospital mortality according to head-to-head comparison of demographic data (P > 0.05).

Conclusions

Use of sRIFLE classification as a marker poorly predicted the benefits of early or late RRT in the context of septic AKI. In the future, more physiologically meaningful markers with which to determine the optimal timing of RRT initiation should be identified.  相似文献   
997.
BACKGROUND: Penicillium species are prevalent airborne fungi. However, the prevalence of allergic sensitization to Penicillium antigens and the true impact of these ubiquitous fungi on atopic respiratory disorders remain to be determined. OBJECTIVE: The purpose of this study was to analyze the prevalence of immunoglobulin (Ig)E and IgG antibodies against Penicillium chrysogenum (Pen ch 13), the alkaline serine protease major allergen of P. chrysogenum, in asthmatic patients of different age groups. METHODS: Pen ch 13 was purified from a culture medium of P. chrysogenum. The reactivity of IgE and IgG antibodies to Pen ch 13 in the serum samples of 212 asthmatic patients was analyzed by immunoblotting methods. RESULTS: Sixty-nine (33%) of the 212 sera analyzed showed IgE and/or IgG immunoblot reactivity to Pen ch 13. Significant differences in the prevalence of IgE and/or IgG antibody reactivity to Pen ch 13 were found among eight different age groups of 212 asthmatic patients. The frequency of IgE-binding reactivity to Pen ch 13 increased significantly with the age of the patients. It was 7% for the group less than 10 years old and 42% for the group older than 70 years old. In addition, a significant difference between the prevalence of IgE (7%) and IgG (33%) antibodies against Pen ch 13 in the group aged 10 or less was also found. CONCLUSIONS: Our study demonstrates that IgE and IgG antibodies specific for Pen ch 13 were detected in approximately one-third of the 212 asthmatic patients analyzed. Our results suggest that allergic sensitization to Pen ch 13, and possibly to other airborne Penicillium species, is more common in older asthmatic patients.  相似文献   
998.
Cushing's disease is rare in children and adolescents. We report the clinical presentations of three children with Cushing's disease. All three exhibited the typical symptoms and signs of weight gain and growth retardation. Tw o also demonstrated personality changes, hypertension and hypokalemia, the last of these being rarely reported in patients with Cushing's disease. Lack of diurnal changes in serum cortisol levels was the most common biochemical finding. Serum cortisol levels were suppressed by low-dose dexamethasone in one patient, which is not typical for patients with Cushing's disease. Imaging studies are essential for localizing the tumor. Transsphenoidal surgery remains the treatment of choice, and pituitary irradiation should be considered for those patients whose tumors cannot be totally removed. Careful follow-up of these patients with awareness of the possibilities of relapse and the complications of hypopituitarism is indicated.  相似文献   
999.
de la Cerda F, Jimenez WA, Gjertson DW, Venick R, Tsai E, Ettenger R. Renal graft outcome after combined liver and kidney transplantation in children: UCLA and UNOS experience.
Pediatr Transplantation 2010: 14:459–464. © 2010 John Wiley & Sons A/S. Abstract: Although it has been described in adults that renal grafts in the context of CLKT have a lower number of AR episodes and improved renal allograft survival, this has never been examined in pediatrics. We performed a single center retrospective case–control study examining 10 patients aged 10 ± 6 yr with a CLKT that survived the post‐surgery period of six months, and compared outcomes to a group of 20 KO transplants matched for age, era, and immunosuppression. We observed a significant reduction in the incidence of AR episodes in the CLKT group. To evaluate whether or not this experience was reproducible nationally, we performed an analysis of the 1995–2005 UNOS database. As of March 2007, 111 CLKT and 3798 KO transplants were identified from the OPTN/UNOS data. There was a significant improvement in the late kidney graft survival at five yr post‐transplant in the CLKT group. These findings support the concept that liver transplantation is immunologically protective of the kidney allograft in CLKT.  相似文献   
1000.
Lee T  Tsai IC  Fu YC  Jan SL  Wang CC  Chang Y  Chen MC 《Pediatric radiology》2006,36(12):1273-1282
Background Echocardiography is the first-line modality for the investigation of neonatal congenital heart disease. Diagnostic cardiac catheterization, which has a small but recognized risk, is usually performed if echocardiography fails to provide a confident evaluation of the lesions. Objective To verify the technical and clinical feasibilities of replacing diagnostic cardiac catheterization with multidetector-row CT (MDCT) in neonatal complex congenital heart disease. Materials and methods Over a 1-year period we prospectively enrolled all neonates with complex congenital heart disease referred for diagnostic cardiac catheterization after initial assessment by echocardiography. MDCT was performed using a 40-detector-row CT scanner with dual syringe injection. A multidisciplinary congenital heart disease team evaluated the MDCT images and decided if further diagnostic cardiac catheterization was necessary. The accuracy of MDCT in detecting separate cardiovascular anomalies and bolus geometry of contrast enhancement were calculated. Results A total of 14 neonates were included in the study. No further diagnostic cardiac catheterization was needed in any neonate. The accuracy of MDCT in diagnosing separate cardiovascular anomalies was 98% (53/54) with only one atrial septal defect missed in a patient with coarctation syndrome. The average cardiovascular enhancement in evaluated chambers was 471 HU. No obvious beam-hardening artefact was observed. Conclusion The technical and clinical feasibility of MDCT in complex congenital heart disease in neonates is confirmed. After initial assessment with echocardiography, MDCT could probably replace diagnostic cardiac catheterization for further anatomical clarification in neonates.  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