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   18819篇
  免费   1083篇
  国内免费   80篇
耳鼻咽喉   75篇
儿科学   415篇
妇产科学   222篇
基础医学   2356篇
口腔科学   735篇
临床医学   1871篇
内科学   4251篇
皮肤病学   384篇
神经病学   1991篇
特种医学   895篇
外科学   3014篇
综合类   109篇
一般理论   4篇
预防医学   1206篇
眼科学   130篇
药学   1247篇
中国医学   24篇
肿瘤学   1053篇
  2023年   145篇
  2022年   154篇
  2021年   393篇
  2020年   290篇
  2019年   403篇
  2018年   481篇
  2017年   455篇
  2016年   429篇
  2015年   496篇
  2014年   668篇
  2013年   1052篇
  2012年   1373篇
  2011年   1308篇
  2010年   816篇
  2009年   786篇
  2008年   1201篇
  2007年   1257篇
  2006年   1206篇
  2005年   1157篇
  2004年   995篇
  2003年   998篇
  2002年   930篇
  2001年   168篇
  2000年   108篇
  1999年   136篇
  1998年   192篇
  1997年   204篇
  1996年   145篇
  1995年   142篇
  1994年   143篇
  1993年   138篇
  1992年   107篇
  1991年   108篇
  1990年   94篇
  1989年   93篇
  1988年   86篇
  1987年   83篇
  1986年   76篇
  1985年   82篇
  1984年   73篇
  1983年   78篇
  1982年   77篇
  1981年   75篇
  1980年   58篇
  1979年   52篇
  1978年   62篇
  1977年   52篇
  1976年   43篇
  1975年   46篇
  1973年   32篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
BACKGROUND AND PURPOSE: Breast cancer is diagnosed worldwide in approximately one million women annually and radiation therapy is an integral part of treatment. The purpose of this study was to investigate the molecular basis underlying response to radiotherapy in breast cancer tissue. MATERIAL AND METHODS: Tumour biopsies were sampled before radiation and after 10 treatments (of 2 Gray (Gy) each) from 19 patients with breast cancer receiving radiation therapy. Gene expression microarray analyses were performed to identify in vivo radiation-responsive genes in tumours from patients diagnosed with breast cancer. The mutation status of the TP53 gene was determined by using direct sequencing. RESULTS AND CONCLUSION: Several genes involved in cell cycle regulation and DNA repair were found to be significantly induced by radiation treatment. Mutations were found in the TP53 gene in 39% of the tumours and the gene expression profiles observed seemed to be influenced by the TP53 mutation status.  相似文献   
972.
The prognostic significance of serum ferritin on survival in lung cancer was evaluated. One hundred and ninety-seven patients were referred for evaluation of pulmonary lesions; 115 patients (85 men) had primary lung cancer. Their median age was 57 years. Seventy-four patients (43 men) with benign lung disease were enrolled as controls. Their median age was 53 years. Serum ferritin was measured at diagnosis. Non-small cell lung cancer (NSCLC) (n=90) was graded according to the TNM-system and small cell lung cancer (SCLC) (n=25) in limited and extensive disease. Follow-up was median 30 months (range 23-36). Patients with lung cancer had higher median ferritin than controls (245 vs. 145 microg/l, p<0.00001): the prevalence of ferritin >300 microg/l was 37% in patients with lung cancer and 14% in controls (p<0.001). There was no significant difference in ferritin between patients with different stages either in NSCLC or in SCLC. Patients with SCLC had higher median ferritin than patients with NSCLC (344 vs. 233 microg/l, p<0.05). No significant differences in ferritin could be demonstrated among the other histological tumour types. The overall survival rate in patients with lung cancer was 52% after 1 year, 33% after 2 years, and 13% after 3 years. Survival rate was lower in patients with ferritin >300 microg/l than in those with ferritin < or =300 microg/l (p<0.0001). The probability of survival 1, 2 and 3 years after diagnosis in patients with ferritin >300 microg/l was 36, 20 and 4%, respectively, and in patients with ferritin < or =300 it was 63, 42 and 18%, respectively (p<0.0001). An elevated ferritin was a significant prognostic factor (p<0.01) even after adjustment for performance status, age, sex, TNM stage, and histological tumour type. TNM stage and performance status were likewise predictors of survival (p<0.01 and p<0.001, respectively). There exists a clinically relevant relationship between serum ferritin concentration and the prognosis of survival in patients with primary lung cancer. The routine use of serum ferritin should be considered in the evaluation and follow-up of pulmonary malignancies.  相似文献   
973.
BACKGROUND AND PURPOSE: The aim of this study was to evaluate the patterns of failure and the treatment of recurrences, in a series of primary irradiated patients with squamous cell carcinoma of the glottic larynx. MATERIALS AND METHODS: Eight hundred and sixty-one consecutive patients were included in this study from 1963 to 1991, out of which 74 were females and 787 males. The stages were: I 56, II 26, III 15, and IV 3%. In 847 of 861 cases (98%) the primary treatment was delivered with curative intent, and out of these 834 patients received primary radical radiotherapy. RESULTS: With a minimum follow up of 5 years, 274/861(32%) patients had persistent or recurrent disease; in 91% of these the persistent or recurrent disease was in the T-position, 15% in the N-position, and 5% developed distant metastases. Curative salvage attempt was possible in 207 patients, and 145 were subsequently controlled. A total of 718 (83%) patients obtained ultimate tumour control, 584 (68%) without a laryngectomy (134 of the controlled had a laryngectomy, 109 had a total laryngectomy and 25 had a partial laryngectomy). In the patients treated with curative intent, the overall 5-year local tumour control, loco-regional tumour control, disease specific survival rate and overall survival rate was 72, 70, 86 and 66%, respectively. For patients with small tumours the disease specific survival for T1a, T1b and T2 was 95, 93 and 83%, respectively. In the 718 patients cured for their glottic carcinoma, 204 new primary malignant tumours were detected. CONCLUSIONS: The study shows that laryngeal glottic carcinoma can be effectively managed by primary radiotherapy and surgery salvage. The control is obtained with a high proportion of laryngeal preservation (68%). Recurrences treated with surgical salvage have a success rate of 70%. New primaries are a major problem.  相似文献   
974.
Ten hips underwent impaction bone grafting with cement as revision of the femoral stem for severe osteolysis. At clinical follow-up of a median of 4 years (range 3.0–4.6 years) there were no failures. The median Harris hip score increased from 53 to 80, and pain score from 25 to 40. Radiographically, there was no resorption of the impacted grafts. All of the 9 patients with radiographical follow-up of more than 1 year showed trabecular remodelling, 7 of whom had signs of cortical repair. Subsidence was a median of 2 mm, with the maximum subsidence being 5 mm. The results appeared clinically stable after 4 years with radiographic reconstitution of the bone stock.  相似文献   
975.
Objective:  We have previously described an association between use of cod liver oil (a dietary n-3 fatty acid supplement) and reduced risk of type 1 diabetes. n-3 fatty acids are ligands for the peroxisome proliferator-activated receptor-γ ( PPARG ), which has recently been implicated in the control of inflammation and possibly autoimmunity. We aimed to estimate the association between the common Pro12Ala polymorphism of PPARG2 and risk of type 1 diabetes, and to test whether there is gene–environment interaction with use of cod liver oil in the first year of life or gene–gene interaction with the established insulin gene ( INS ) and human leukocyte antigen DQ ( HLA-DQ ) genetic susceptibility loci.
Methods:  We designed a population-based case–control study of childhood-onset type 1 diabetes in Norway with information on use of cod liver oil in the first year of life from questionnaires and PPARG2 genotype data for 483 cases and 1520 control subjects. We used logistic regression for analysis.
Results:  The odds ratio for the PPARG2 Ala/Ala or Pro/Ala vs. Pro/Pro genotype and type 1 diabetes was 0.89 (95% CI: 0.69–1.13, p = 0.33). There was no significant interaction with cod liver oil in the first year of life [P (interaction) = 0.35] or with the INS polymorphism [P(interaction) = 0.42].
Conclusions:  Although the association between PPARG2 and type 1 diabetes was not significant, the observed odds ratio was almost identical to that observed in two previous studies and can contribute to meta-analysis indicating a weak but significant association. Our hypothesized interaction between cod liver oil and PPARG2 in reducing type 1 diabetes risk was not supported.  相似文献   
976.

Background  

Few studies have investigated the specific effect of single intervention components in randomized controlled trials. The purpose was to investigate the effect of adding group-based diet and exercise counselling to individual life-style counselling on long-term changes in dietary habits.  相似文献   
977.
A number of genes have altered activity in small-cell lung cancer (SCLC), but especially genes of the myc family (c-myc, L-myc and N-myc) are expressed at high levels in SCLC. Most studies have explored expression at the mRNA level, whereas studies of myc family oncoprotein expression are sparse. We examined the expression of myc proto-oncogenes at the mRNA and protein level in 23 cell lines or xenografts. In the cell lines, the doubling time and the cell-cycle distribution, as determined by flow-cytometric DNA analysis, were examined to establish whether the level of myc-gene-family expression correlated with proliferative parameters. All tumours expressed at least one myc family member at the mRNA level. Exclusive c-myc mRNA expression was demonstrated in 8 tumours, L-myc in 7 and N-myc in I. Five tumours expressed both c-myc and L-myc, and 2 tumours expressed both c-myc and N-myc. In general, the level of expression of c-myc and N-myc was similar at the mRNA and the protein level. Expression of c-myc was positively correlated with the proliferative index (sum of S and G2 + M phases) of cell lines, but not with the population doubling time. In general, L-myc-expressing cell lines had a low proliferative index. There was no systematic difference in myc expression between cell lines and xenografts of individual tumours.  相似文献   
978.
Objective To compare obstetric and perinatal outcome between two different expectant managements in women with prelabour rupture of the membranes (PROM).
Design A randomised study.
Participants One thousand three hundred and eighty-five women with rupture of the membranes at 34 to 42 weeks without contractions.
Interventions Women without contractions 2 h after admission were randomised to early induction the following morning after PROM (early induction group) or induction two days later (late induction group). Women with contractions starting within 2 h after admission were included in the calculations as a short latency group. Digital examinations of the cervix were avoided until onset of active labour. Labour was induced with oxytocin in both groups if no spontaneous contractions occurred or if chorioamnionitis or fetal distress was detected.
Main outcome measures The frequency of spontaneous deliveries, operative deliveries, maternal and neonatal infections.
Results In nulliparous women, a higher rate of spontaneous deliveries was found in the late induction group (89%) compared with the early induction group (81%) (   P < 0.05  ). The ventouse extraction rate was 7% and 14% respectively (   P < 0.05  ). A low (2–4%) caesarean section rate was recorded and did not differ between the groups. Endometritis was detected in six women after delivery. Sixty-one children were treated with antibiotics, and no difference could be detected between the groups.
Conclusions A higher rate of spontaneous deliveries was found among nulliparous women with prolonged latency as compared with brief latency prior to induction. A protocol of no digital examination before labour was associated with infrequent maternal and fetal morbidity, regardless of latency.  相似文献   
979.
Flow cytometric DNA analysis with assessment of S-phase fraction and DNA ploidy was compared to Nottingham histologic grade. The study population consisted of 654 patients who presented between 1987 and 1996 with primary operable breast cancer and whose tumours had been analysed for S-phase fraction and DNA ploidy at the time of surgery. Grade, tumour size, node status, steroid receptor status, age, S-phase fraction and DNA ploidy were analysed univariately and multi-variately in a Cox proportional hazard analysis. In the univariate analyses all parameters were statistically significantly associated with breast cancer mortality during the follow-up period of 2–11 years. The most powerful predictor of death from breast cancer in the multiple regression analysis was grade. Patients with grade 1 tumours have excellent prognosis. We conclude that tumour grade is a strong prognostic indicator applicable to all breast cancer patients, regardless of size and nodal status, and advocate its general use.  相似文献   
980.
The European Journal of Health Economics -  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