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   89757篇
  免费   4445篇
  国内免费   369篇
耳鼻咽喉   2400篇
儿科学   2863篇
妇产科学   2812篇
基础医学   11575篇
口腔科学   2547篇
临床医学   6094篇
内科学   21583篇
皮肤病学   2589篇
神经病学   7797篇
特种医学   1825篇
外国民族医学   1篇
外科学   10106篇
综合类   535篇
一般理论   23篇
预防医学   8304篇
眼科学   1845篇
药学   7396篇
中国医学   513篇
肿瘤学   3763篇
  2023年   544篇
  2022年   1243篇
  2021年   3073篇
  2020年   1451篇
  2019年   2665篇
  2018年   3332篇
  2017年   2041篇
  2016年   2018篇
  2015年   2161篇
  2014年   3379篇
  2013年   4666篇
  2012年   6381篇
  2011年   6977篇
  2010年   3856篇
  2009年   2997篇
  2008年   4910篇
  2007年   5426篇
  2006年   5195篇
  2005年   5148篇
  2004年   4847篇
  2003年   4552篇
  2002年   4052篇
  2001年   2077篇
  2000年   2229篇
  1999年   1757篇
  1998年   592篇
  1997年   485篇
  1996年   369篇
  1995年   316篇
  1994年   276篇
  1993年   207篇
  1992年   565篇
  1991年   465篇
  1990年   466篇
  1989年   345篇
  1988年   351篇
  1987年   307篇
  1986年   279篇
  1985年   266篇
  1984年   174篇
  1983年   173篇
  1982年   144篇
  1981年   166篇
  1980年   120篇
  1979年   167篇
  1978年   136篇
  1974年   117篇
  1973年   86篇
  1971年   93篇
  1969年   96篇
排序方式: 共有10000条查询结果,搜索用时 665 毫秒
991.
PURPOSE: It has been hypothesized that tumors with high interstitial fluid pressure (IFP) and/or hypoxia respond poorly to chemotherapy (CT) because of poor drug delivery. Preclinical studies have shown that paclitaxel reduces the IFP and improves the oxygenation (pO(2)) of tumors. Our aim is to evaluate the IFP and pO(2) before and after neoadjuvant CT using sequential paclitaxel and doxorubicin in patients with breast cancer tumors of >/= 3 cm. PATIENTS AND METHODS: Patients were randomly assigned, according to an institutional review board-approved phase II protocol, to receive neoadjuvant sequential CT consisting of either four cycles of dose-dense doxorubicin at 60 mg/m(2) every 2 weeks followed by nine cycles of weekly paclitaxel at 80 mg/m(2) (group 1) or vice versa, with paclitaxel administered before doxorubicin (group 2). Patients were re-evaluated clinically and radiologically. The IFP (wick-in-needle technique) and pO(2) (Eppendorf) were measured in tumors at baseline and after completing the administration of the first and second drug. RESULTS: IFP and pO(2) were measured in 54 patients at baseline and after the first CT. Twenty-nine and 25 patients were randomly assigned to groups 1 and 2, respectively. Paclitaxel, when administered first, decreased the mean IFP by 36% (P = .02) and improved the tumor pO(2) by almost 100% (P = .003). In contrast, doxorubicin did not have a significant effect on either parameter. This difference was independent of the tumor size or response measured by ultrasound. CONCLUSION: Paclitaxel significantly decreased the IFP and increased the pO(2), whereas doxorubicin did not cause any significant changes. Tumor physiology could potentially be used to optimize the sequence of neoadjuvant CT in breast cancer.  相似文献   
992.
BACKGROUND AND PURPOSE: To determine whether the information gathered from a fixed number of periodic verification films accurately reflects the true imprecision in patient positioning during the whole radiation therapy of early breast cancer. PATIENTS AND METHODS: A total of 204 medial and lateral treatment fields were evaluated in 102 breast cancer patients treated with conservative surgery and radiation therapy. For each treatment field, the central lung distance was measured on portal films obtained from one simulation and four treatment controls at weekly intervals during breast irradiation. Systematic and random errors in patient positioning throughout all treatment fractions were estimated from the available controls using Bayesian methods. RESULTS: The average systematic and random errors during treatment controls were 2.7 and 1.9 mm, respectively. For these mean control values, the probabilities that the true systematic and random errors remain below 5mm during all treatment fractions were 99 and 100%, respectively. CONCLUSIONS: Reproducibility of patient positioning was supported by a virtually null probability for systematic or random errors greater than 5 mm during the whole radiation therapy. Weekly verification films seem to be sufficient to estimate patient positioning errors with high accuracy in radiotherapy of early breast cancer.  相似文献   
993.
INTRODUCTION: This study aims to asses the effectiveness and toxicity of boost radiotherapy concomitant and concurrent cisplatin for patients with locally advanced head and neck cancer (LAHNC). MATERIAL AND METHODS: There were 30 patients included in a prospective, phase II single-institution trial and of whom, 29 were at AJCC stage IV and 1 at stage III. Treatment consisted of radiotherapy acceleration fractionation with concomitant boost, 72 Gy, and 2 cycles of concomitant cisplatin (20 mg/m2/day continuous infusion; days 1-5 and 29-33). Amifostine, (i.v. 200 mg/m2) was administered to 26 prior to the first fraction of radiotherapy. Endpoints of the study were quality-of-life (QL), overall survival, and local control of disease. RESULTS: Complete response (CR) was achieved in 23 patients (77%), 2 patients had partial response (PR) (7%), 4 had no response (13%), and 1 was not evaluated for response. The 2-year overall survival and loco-regional control were 60% and 56%, respectively. Main toxicity was grade 3 or 4 mucositis in 93% of the patients. QL scores (questionnaire QLQC30; version 3.0) and the HN cancer module QLQ-HN35) showed a worsening in areas related to the treatment e.g. dry mouth, problems stretching the mouth, and sticky saliva. CONCLUSIONS: this combination modality is active, but toxic, in the treatment for LAHNC. Concomitant boost radiotherapy is probably, not the best radiotherapy schema for combining with chemotherapy in LAHNC.  相似文献   
994.
INTRODUCTION: Presence of circulating DNA in the serum of patients with cancer makes detection of tumour-specific genetic alterations feasible. OBJECTIVE: To study serum DNA concentration in patients diagnosed as having advanced Non-Small Cell Lung Cancer (NSCLC) and to evaluate its relationship with age, histology, stage, response, time-to-progression (TTP), and survival. METHODS: Serum DNA from 78 patients was purified and spectrophotometrically quantified. RESULTS: No significant correlations were found between serum DNA concentration and age, histology, response and survival. There was a significant correlation with respect to stage (IIIB = 408.75 ng/ml; IV = 478.74 ng/ml; p = 0.02). When patients were grouped according to DNA concentration, significant correlation with TTP was found; establishing a cut-off point at 500 ng/ml ([DNA] < 500 ng/ml TTP = 7.25 months, 95%CI: 3.5-5.25; [DNA ] > or = 500 ng/ml TTP = 4.25 months, 95%CI: 2-6.5; p = 0.05). CONCLUSIONS: Using the present method, DNA concentration quantification appears to be simple, but with certain deficiencies due to inter-sample variability and low specificity. This is because total DNA concentration is measured without distinguishing as to whether it is tumour-related. We suggest that there is a correlation between DNA concentration and prognosis which enables an analysis of the natural history of the disease.  相似文献   
995.
PURPOSE: Elderly patients constitute a subpopulation with special characteristics that differ from those of the nonelderly and have been underrepresented in clinical trials. This study was performed to determine the efficacy and safety of irinotecan (CPT-11) in combination with fluorouracil (FU) administered as a 48-hour continuous infusion twice a month in elderly patients. PATIENTS AND METHODS: Patients > or = 72 years old with metastatic colorectal cancer, Eastern Cooperative Oncology Group performance status of 0 to 1, no geriatric syndromes, and no prior treatment were treated every 2 weeks with CPT-11 180 mg/m2 plus FU 3,000 mg/m2 in a 48-hour continuous infusion. RESULTS: By intent-to-treat analysis, in 85 assessable patients, the objective response rate was 35% (95% CI, 25% to 46%), and stable disease was 33% (95% CI, 23% to 44%). Median time to progression was 8.0 months (95% CI, 6.0 to 10.0 months), and median overall survival time was 15.3 months (95% CI, 13.8 to 16.9 months). Toxicity was moderate. Grade 3 and 4 neutropenia, diarrhea, and asthenia were observed in 21%, 17%, and 13% of patients, respectively. Only one case of neutropenic fever occurred. There were two toxic deaths, one was a result of grade 4 diarrhea and acute kidney failure, and the other was a result of massive intestinal hemorrhage in the first cycle. The study of prognostic factors did not reveal any predictive factor of response. Response to treatment and baseline lactate dehydrogenase were the main factors conditioning progression-free and overall survival. CONCLUSION: Twice a month continuous-infusion CPT-11 combined with FU is a valid therapeutic alternative for elderly patients in good general condition.  相似文献   
996.
Prognostic factors in maxillary sinus and nasal cavity carcinoma   总被引:2,自引:0,他引:2  
AIMS: The aim of the present study is to define prognostic factors, particularly the impact of treatment on paranasal sinus and nasal cavity malignancies. MATERIAL AND METHODS: Retrospective study of patients with maxillary antrum and nasal fossae malignancies. A maxillectomy classification as performed to treat malignancies in our institution is described. Multivariate analysis of prognostic factors was done using the Cox's model. RESULTS: One hundred and nine patients were evaluated. Squamous cell carcinoma was found in 62 cases and in 95 patients the epicentre of the tumour was located in the maxillary antrum. Ten patients were treated with surgery only, 39 patients with surgery and adjuvant radiation therapy, 37 cases received only radiotherapy, and 18 received radiotherapy followed by surgery; in five cases a combination of chemo-radiotherapy was used. Multivariate analysis identified T classification, orbit invasion, N classification, site of origin of tumour in nasal fossae, and no surgical resection as independent prognostic factors (p=0.0001). CONCLUSION: T4 tumours with orbit invasion present bad prognosis as compared to other T4 tumours. Surgical resection should be included in the treatment strategy. Because of the high frequency of lymph-node metastasis, neck treatment should be considered in T4 tumours.  相似文献   
997.
Methylenetetrahydrofolate reductase (MTHFR) polymorphisms have been associated not only with the risk for acute lymphoblastic leukemia (ALL) in adults and children, but also with increased methotrexate toxicity. The present study aimed to investigate whether MTHFR polymorphisms modify the risk for development of secondary malignancies in children treated for ALL with protocols that included high-dose methotrexate. MTHFR genotypes were determined in DNA samples isolated from archived bone marrow smears of 15 patients with a second malignancy and a matched control group of 30 patients who did not developed a second malignancy after the treatment for ALL. The frequencies of MTHFR C677T and A1298C genotypes in all patients were: C677T: CC 40%, CT 46.7% and TT 13.3% and A1298C: AA 46.7%, AC 44.4% and CC 8.9%. The relative risk for second malignancy was not significantly increased in ALL patients having at least one polymorphic C667T [odds ratio (OR) 1.51; 95% confidence interval (CI) 0.43 - 5.31] or one polymorphic A1298C allele (OR 1; 95% CI 0.29 - 3.46). Our study suggests that MTHFR polymorphisms are not associated with increased risk of second cancer in children treated with high-dose methotrexate.  相似文献   
998.
Introduction This phase II study investigated the anti-tumour activity and toxicity of CPT-11 (250 mg/m2 i.v. infusion over 60 minutes) administered every 2 weeks as second-line chemotherapy in patients with advanced colorectal cancer (CRC). Material and methods Patients (n=63) with histology diagnosis of advanced CRC and proven resistance to previous fluoropyrimidine therapy were enrolled. Results A total of 510 CPT-11 cycles were administered, with a mean of 8 cycles per patient (range: 1–32). The median relative dose intensity was 93%. Partial response (PR) was obtained in 11 patients (17.5%; 95%CI: 8.1%–26.7%) and 29 patients (46.0%) showed stable disease (clinical benefit of 63.5%). The median duration of response was 6.8 months (95%CI: 6.1–7.5 months), median survival was 8.8 months (95%CI: 6.3–11.5 months) and median time to disease progression was 4.5 months (95%CI: 3.9–5.0 months). Overall, this schedule of CPT-11 chemotherapy was well tolerated by the patient. Neutropenia was the most frequent grade 3/4 haematological toxicity (20.6% of patients and 4.1% of cycles). Neutropenia with concurrent fever or infection occurred in 7 patients (11.1%). Late onset diarrhoea was the most frequent grade 3/4 non-haematological toxicity (19.0% of patients and 2.3% of cycles). Other, lower-incidence, toxicities were anaemia, fever, infection, mucositis, nausea and vomiting. There were no toxic deaths. Conclusions We found that CPT-11, administered as 250 mg/m2 i.v. infusion over 60 minutes every 2 weeks, was active and well tolerated schedule in the second-line chemotherapy of advanced CRC patients. This bi-weekly scheme could be used as an alternative to the weekly or the every-three-week schedule as well as in combined therapies with other chemotherapeutic agents for the treatment of advanced, metastatic, CRC.  相似文献   
999.
1000.
Purpose We retrospectively reviewed our institution’s database to investigate the outcome and impact of combined radiochemotherapy (RT/CT; concomitant or in sequence) in localised small-cell lung cancer (L-SCLC). Material and methods Between January 1995 to November 1999, 79 patients with L-SCLC received combined RT/CT at our Institution. RT was delivered concurrently or sequentially following the CT. Patients with treatment response received additional prophylactic cranial irradiation (PCI). Results Of the patients treated, 54% had received concurrent CT/RT compared to 46% receiving RT following the CT. PCI was administered to 80% of the patients. Complete response was observed in 66% of patients. With a median follow up of 30 months, median overall survival was 15.9 months; 14.3 months for patients who received RT following CT and 21.6 months for those receiving concurrent CT/RT. The type of schedule of combined radiochemotherapy was an independent prognostic factor for survival free of local recurrence, as was additional PCI for distant metastasis-free survival. Conclusions Our results are similar to those reported previously in the literature. The main point of interest is that our patients were non-selected. We strongly support the use of concurrent CT/RT so as to achieve results comparable to the best in the literature.
  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