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   1476篇
  免费   133篇
  国内免费   59篇
耳鼻咽喉   5篇
儿科学   48篇
妇产科学   26篇
基础医学   200篇
口腔科学   34篇
临床医学   220篇
内科学   294篇
皮肤病学   8篇
神经病学   85篇
特种医学   123篇
外科学   240篇
综合类   41篇
一般理论   2篇
预防医学   97篇
眼科学   24篇
药学   107篇
中国医学   11篇
肿瘤学   103篇
  2024年   6篇
  2023年   19篇
  2022年   29篇
  2021年   55篇
  2020年   28篇
  2019年   37篇
  2018年   60篇
  2017年   47篇
  2016年   51篇
  2015年   45篇
  2014年   74篇
  2013年   62篇
  2012年   104篇
  2011年   89篇
  2010年   73篇
  2009年   56篇
  2008年   65篇
  2007年   81篇
  2006年   58篇
  2005年   46篇
  2004年   53篇
  2003年   37篇
  2002年   42篇
  2001年   19篇
  2000年   9篇
  1999年   14篇
  1998年   38篇
  1997年   36篇
  1996年   21篇
  1995年   30篇
  1994年   18篇
  1993年   17篇
  1992年   6篇
  1991年   11篇
  1990年   15篇
  1989年   17篇
  1988年   16篇
  1987年   11篇
  1986年   17篇
  1985年   15篇
  1984年   13篇
  1983年   7篇
  1982年   10篇
  1981年   14篇
  1980年   11篇
  1979年   12篇
  1977年   17篇
  1976年   11篇
  1973年   8篇
  1966年   9篇
排序方式: 共有1668条查询结果,搜索用时 15 毫秒
11.
Heterogeneity of B cell involvement in acute nonlymphocytic leukemia   总被引:2,自引:0,他引:2  
In order to study the pattern of B cell involvement in acute nonlymphocytic leukemia (ANLL), multiple B lymphoid cell lines were established by Epstein-Barr virus transformation of peripheral blood mononuclear cells from two patients with the disease who were heterozygous for the X chromosome-linked glucose-6-phosphate dehydrogenase (G6PD). In one patient, the progenitor cells involved by the leukemia exhibited multipotent differentiative expression, whereas in the other patient the cells showed differentiative expression restricted to the granulocytic pathway. In the patient whose abnormal clone showed multipotent expression, the ratio of B-A G6PD in B lymphoid cell lines was skewed in the direction of type B (the enzyme characteristic of the leukemia clone) and significantly different from the 1:1 ratio expected. It is, therefore, likely that the neoplastic event occurred in a stem cell common to the lymphoid series as well as to the myeloid series. In contrast, evidence for B cell involvement was not detected in the patient whose ANLL progenitor cells exhibited restricted differentiative expression. These findings underscore the heterogeneity of ANLL. Clinically and morphologically similar malignancies in these two patients originated in progenitors with different patterns of stem cell differentiative expression. This difference may reflect differences in cause and pathogenesis.  相似文献   
12.
Leung GK  Ng GK  Ho W  Hung KN  Yuen WK 《Injury》2012,43(9):1419-1422
IntroductionTo review the outcome of patients with post-traumatic acute subdural haematoma (ASDH) before and after the establishment of a hospital trauma team at a designated trauma centre.MethodA retrospective analysis was conducted on 82 consecutive patients who underwent surgery for post-traumatic ASDH. The ‘PRE’ and ‘POST’ groups included patients admitted before and after the establishment of a hospital trauma team, respectively.Injury severity was assessed by the admission Glasgow coma score, imaging findings, and the revised trauma score. Clinical outcome measures were the hospital length of stay and the Glasgow outcome score (GOS) upon hospital discharge.ResultsThe overall mortality rate was 53.7%. No significant difference was found between the PRE and POST groups. The mean length of hospital stay was also comparable between the two groups. The functional status of those who survived acute hospital care was significantly better in the POST group. Good outcome (GOS of 4 or 5) was achieved in 66.7% of the survivors in the POST group, compared with 25.0% in the PRE group (p = 0.024).ConclusionPost-traumatic ASDH carried a poor prognosis. The mortality rate and hospital length of stay of patients were not found to be reduced after the establishment of a hospital trauma team. The latter, however, was associated with significantly better functional outcome amongst survivors. Although causality cannot be established due to the multitude of factors which may have affected patient outcome, our findings nonetheless provide further support for the introduction of a multidisciplinary hospital trauma team for the optimal care of trauma patients.  相似文献   
13.
BACKGROUND: Aortic valve replacement in the young adult (aged 18 to 50 years) is a choice between a mechanical prosthesis with attendant lifelong anticoagulation or biological prostheses of varying types that may have limited life expectancy in this age group. METHODS: The Cardiac Surgical Research Foundation database was accessed to determine long-term outcomes in patients having aortic valve replacement with the St. Jude Medical Valve. This database has been privately maintained since the world's first St. Jude Medical (SJM) valve implant in 1977. Patients were contacted by questionnaire or by telephone if the survey was not returned. Follow-up was 93% complete. RESULTS: From October 1977 through October 1997, 271 patients less than 50 years of age had isolated aortic valve replacement. Follow-up was 1957 patient years. Thirty-day operative mortality was 1.1% with 18 late deaths, 4 of which were valve related. Ninety percent of survivor INR responses indicated a frequency of monthly INR checks or less. Valve-related events including percent per patient year and mortality related to these events included thromboembolism, 6 episodes (0.3% per patient year, no deaths); anticoagulant-related bleeding, 6 events (0.3% per patient year, 2 deaths); paravalvular leak, 6 events (0.3% per patient year, 2 deaths); valve thrombosis, 2 events (0.1% per patient year, no deaths); and endocarditis, 3 events (0.15% per patient year, no deaths). There was no incidence of structural valve failure. CONCLUSIONS: The SJM valve has a long record of excellent performance with durability lasting more than 20 years. The incidence of untoward events is low and death over time due to valve-related complications is low (4 of 271). The SJM valve has become our valve of choice for younger patients.  相似文献   
14.
15.
Objective: Two major changes have occurred in inguinal hernia repair during the last two decades: (i) the use of tension‐free mesh repair; and (ii) the application of laparoscopic technique for repair. The aims of the present study were to study: (i) how inguinal hernia repair was carried out; and (ii) the outcome of inguinal hernia repair in Hospital Authority (HA) hospitals. Methodology: This was a retrospective analysis on 8311 elective inguinal hernia repairs performed in 16 HA hospitals from January 2001 to December 2003. The mean age was 63.9 ± 14.2 years, and the male to female ratio was 22.0 : 1.0. Among these, 869 (10.5%) repairs were performed with the laparoscopic approach and 7442 (89.5%) repairs with the open approach. The proportion of laparoscopic hernia repair increased from 8.7% to 12.6%. Results: For open repair, 39% of cases were carried out with regional anaesthesia, 32% with general anaesthesia and 29% with local anaesthesia (LA). Furthermore, mesh repair was used in 88% of the patients. For laparosocpic repair, 98.4% of cases were carried out under general anaesthesia, and all patients had mesh repair using the totally extraperitoneal approach. A significantly higher proportion of bilateral repair and recurrent hernia repair was performed with the laparoscopic approach (P = 0.000). For primary unilateral repair, there was no significant difference in the postoperative length of stay (LOS) and the total LOS between the laparoscopic and the open surgery groups. No difference in LOS was found in recurrent hernia repair between the two groups. With respect to bilateral repair, both the preoperative LOS (P = 0.036) and total LOS (P = 0.039) were shorter in the laparoscopic group. Furthermore, a significantly higher proportion of day‐surgery patients was observed in the laparoscopic group than the open surgery group (21.3%vs 16.9%, P = 0.001). Nevertheless, when only the results of 2003 were analyzed, the postoperative LOS (P = 0.000) and total LOS (P = 0.000) were significantly shorter in the laparoscopic group than the open surgery group. The LOS parameters were significantly shorter in the open surgery LA subgroup compared with the non‐LA subgroup (P = 0.000), and they were not different from those in the laparoscopic group. Conclusions: The open mesh repair is the predominant approach for inguinal hernia repair in HA hospitals. The originally described local anaesthetic approach was under utilized, although it resulted in good outcome. The use of laparoscopic hernia repair is increasing and a learning curve was recently observed with improved outcome.  相似文献   
16.
Generalized low bone mass has been well documented in patients with adolescent idiopathic scoliosis (AIS). However, studies linking calcium-intake (CA), weight-bearing physical-activity (PA) and bone mass of AIS are lacking. We aimed to study the relationship between CA, PA and bone mass in AIS girls and compared to those of healthy non-AIS controls during the peripubertal period. Newly diagnosed AIS girls (n=596) aged 11–16 years with Cobb angle 10° were recruited to compare with age-matched healthy girls (n=302) in a cross-sectional study. Anthropometric parameters, pubertal status, CA and PA were assessed. Areal bone mass of lumbar spine and femoral neck, and volumetric bone mass of distal radius and tibia were determined by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography, respectively. The results showed that weight and body mass index (BMI) of AIS were lower than the controls (P<0.05). Corrected height and arm span of AIS were longer than those of controls from 13 years onwards (P<0.02). Median CA of AIS was <410 mg/day across the ages and did not differ from the controls (P=0.063). Median PA of AIS (1.6 h/day) was lower than the controls (1.8 h/day) (P=0.025). Bone mass of AIS was on average 6.5% lower than controls across the ages (P<0.05). CA and PA were significantly correlated with bone mass of AIS (P<0.04). Multivariate analysis showed that AIS in girls was associated with lower bone mass, and that both CA and PA were independent predictors of bone mass in AIS. In conclusion, AIS girls were found to have lower body weight and BMI, longer segmental lengths and generalized low bone mass. Inadequate calcium intake and weight-bearing physical activity were significantly associated with low bone mass in AIS girls during the peripubertal period. The importance of preventing generalized osteopenia in the control of AIS progression during the peribubertal period warrants further study.  相似文献   
17.
OBJECTIVES: Pathological and biochemical features of prostate cancers detected on repeat biopsies in men with total PSA level between 2.0 and 4 ng/ml were evaluated and compared to those cancers detected on first biopsy. METHODS: 315 men with PSA level between 2.0 and 4 ng/ml underwent transrectal ultrasound guided sextant biopsy and two additional transition zone biopsies (Octant Biopsy). All subjects whose biopsy samples were negative for prostate cancer underwent a repeat biopsy after 6 weeks. Those with clinically localized cancers were offered surgery or radiation therapy. Pathological and clinical features of patients diagnosed with prostate cancer on initial and repeat biopsy were compared. RESULTS: Cancer detection rates on first and second biopsy were 24% (75/315) and 13% (29/224), respectively. Overall, of patients with clinically localized disease (83% of cancers detected), 87% underwent radical prostatectomy, 11% opted for radiation therapy and 2% opted for watchful waiting. Cancers found in the first biopsy group were more multifocal (p = 0.01) while cancers found on second biopsy were more located in the apical-dorsal region (p = 0.003). No significant differences were noted with respect to extracapsular extension, seminal vesical invasion, positive margins, final pathological stage, Gleason score, percentage Gleason grade 4/5, serum PSA and patient age between first and second biopsy. CONCLUSIONS: With an octant biopsy regime, biochemical and pathological features of cancers detected on initial and repeat biopsy in the PSA range 2.0 to 4 ng/ml are comparable in terms of PSA, grade, stage and cancer volume suggesting identical cancer characteristics, thus advocating for a repeat prostate biopsy in case of a negative finding on initial biopsy.  相似文献   
18.
19.
金刚大化学成分的研究   总被引:1,自引:0,他引:1  
从百部科黄精叶钩吻属植物金刚大(Croomia japonica Miq)的根部分得五个成分,分别为粉蕊黄杨胺A(pachysamine A,Ⅰ)、金刚大啶(croomionidine,Ⅱ)、金刚大碱(croomme,Ⅲ)、脱氢金刚大碱(didehydrocroomine,Ⅳ)和β-谷甾醇。应用波谱(IP,MS,1HNMR和13CNMR等)分析、理化数据测定和化学转化,确定丁它们的结构,其中金刚大啶为新甾体生物碱。  相似文献   
20.
BACKGROUND: Recently, a number of surgical and laser approaches have been used to improve visual outcome in cases of central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO). Intravitreal steroid injection alone appears to offer only temporary improvement at best. Radial optic neurotomy for CRVO and arteriovenous adventitial sheathotomy for BRVO are the most frequently utilized surgical procedures for these conditions, but evidence regarding efficacy is still lacking. We have suggested that macular decompression by internal limiting membrane (ILM) peeling may reduce macular edema and hemorrhage and improve visual acuity by relieving elevated intraretinal tissue pressure and facilitating egress of blood and extracellular fluid out of inner retinal layers into the vitrectomized vitreous cavity. METHODS: 50 cases of severe visual loss due to macular edema caused by CRVO or BRVO, not eligible for laser photocoagulation, underwent pars plana vitrectomy with removal of preretinal hyaloid, peeling of the ILM stained with indocyanine green dye, air-fluid exchange, and postoperative prone positioning. RESULTS: In all cases, intraretinal blood and retinal thickening diminished within 6 weeks of surgery. Visual acuity improved in 87% of CRVO cases and 68% of BRVO cases. Vision improved and stabilized at 39 days after surgery. Average improvement was 2.6 lines with a 6-line improvement in 1 case. There was no difference in outcome between cases with ischemic or nonischemic features on fluorescein angiography. INTERPRETATION: Macular decompression using vitrectomy and ILM peeling is effective in the treatment of severe visual loss due to macular edema in CRVO and in those BRVO cases that do not qualify for laser photocoagulation.  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