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   8518篇
  免费   527篇
  国内免费   26篇
耳鼻咽喉   81篇
儿科学   187篇
妇产科学   112篇
基础医学   1301篇
口腔科学   120篇
临床医学   769篇
内科学   1901篇
皮肤病学   125篇
神经病学   1030篇
特种医学   755篇
外国民族医学   2篇
外科学   1071篇
综合类   70篇
一般理论   2篇
预防医学   433篇
眼科学   145篇
药学   514篇
中国医学   4篇
肿瘤学   449篇
  2023年   82篇
  2022年   114篇
  2021年   212篇
  2020年   118篇
  2019年   156篇
  2018年   173篇
  2017年   165篇
  2016年   200篇
  2015年   209篇
  2014年   285篇
  2013年   359篇
  2012年   567篇
  2011年   568篇
  2010年   351篇
  2009年   300篇
  2008年   489篇
  2007年   537篇
  2006年   475篇
  2005年   440篇
  2004年   426篇
  2003年   356篇
  2002年   375篇
  2001年   177篇
  2000年   163篇
  1999年   163篇
  1998年   117篇
  1997年   90篇
  1996年   49篇
  1995年   41篇
  1994年   54篇
  1993年   40篇
  1992年   85篇
  1991年   90篇
  1990年   91篇
  1989年   97篇
  1988年   78篇
  1987年   68篇
  1986年   62篇
  1985年   75篇
  1984年   53篇
  1983年   41篇
  1982年   34篇
  1979年   53篇
  1978年   30篇
  1977年   22篇
  1976年   22篇
  1975年   19篇
  1974年   19篇
  1973年   18篇
  1972年   20篇
排序方式: 共有9071条查询结果,搜索用时 15 毫秒
91.
PURPOSE: The role of unrelated allogeneic stem-cell transplantation in acute lymphoblastic leukemia (ALL) patients is still not clear, and only limited data are available from the literature. We analyzed factors affecting clinical outcome of ALL patients receiving a related or unrelated stem-cell graft from matched donors. PATIENTS AND METHODS: The total study population was 264 adult patients receiving a myeloablative allogeneic stem-cell transplant for ALL at nine bone marrow transplantation centers between 1990 and 2002. Of these, 221 patients receiving a matched related or unrelated graft were analyzed. One hundred forty-eight patients received transplantation in complete remission; 62 patients were in relapse; and 11 patients were refractory to chemotherapy before transplant. Fifty percent of patients received bone marrow, and 50% received peripheral blood stem cell from a human leukocyte antigen-identical related (n = 103), or matched unrelated (n = 118) donor. RESULTS: Disease-free survival (DFS) at 5 years was 28%, with 76 patients (34%) still alive (2.2 to 103 months post-transplantation), and 145 deceased (65 relapses, transplant-related mortality, 45%). We observed an advantage regarding DFS in favor of patients receiving transplantation during their first complete remission (CR) in comparison with patients receiving transplantation in or after second CR (P =.014) or who relapsed (P <.001). We observed a clear trend toward improved survival in favor of B-lineage ALL patients compared with T-lineage ALL patients (P =.052), and Philadelphia chromosome-positive patients had no poorer outcome than Philadelphia chromosome-negative patients. Total-body irradiation-based conditioning improved DFS in comparison with busulfan (P =.041). CONCLUSION: Myeloablative matched related or matched unrelated allogeneic hematopoietic stem-cell transplantation in ALL patients should be performed in first CR.  相似文献   
92.
PURPOSE: To compare the effectiveness and side effects of methadone and morphine as first-line treatment with opioids for cancer pain. PATIENTS AND METHODS: Patients in international palliative care clinics with pain requiring initiation of strong opioids were randomly assigned to receive methadone (7.5 mg orally every 12 hours and 5 mg every 4 hours as needed) or morphine (15 mg sustained release every 12 hours and 5 mg every 4 hours as needed). The study duration was 4 weeks. RESULTS: A total of 103 patients were randomly assigned to treatment (49 in the methadone group and 54 in the morphine group). The groups had similar baseline scores for pain, sedation, nausea, confusion, and constipation. Patients receiving methadone had more opioid-related drop-outs (11 of 49; 22%) than those receiving morphine (three of 54; 6%; P =.019). The opioid escalation index at days 14 and 28 was similar between the two groups. More than three fourths of patients in each group reported a 20% or more reduction in pain intensity by day 8. The proportion of patients with a 20% or more improvement in pain at 4 weeks in the methadone group was 0.49 (95% CI, 0.34 to 0.64) and was similar in the morphine group (0.56; 95% CI, 0.41 to 0.70). The rates of patient-reported global benefit were nearly identical to the pain response rates and did not differ between the treatment groups. CONCLUSION: Methadone did not produce superior analgesic efficiency or overall tolerability at 4 weeks compared with morphine as a first-line strong opioid for the treatment of cancer pain.  相似文献   
93.
PURPOSE: Amplification of the MYCN oncogene at chromosome 2p24-25 identifies an aggressive subtype of human neuroblastoma with a poor clinical outcome. Differences in amplicon structure and coamplification of genes telomeric and centromeric to the MYCN oncogene have previously been described. A relevant role of gene coamplification for neuroblastoma pathogenesis remains elusive. PATIENTS AND METHODS: We analyzed 98 primary neuroblastoma tumors with MYCN amplification for coamplification of seven additional genes at chromosome 2p24-25 (DDX1, NAG, NSE1, LPIN1, EST-AA581763, SMC6, and SDC1). Two semiquantitative multiplex polymerase chain reactions were used to obtain the amplification status of the target genes in relation to a reference gene on chromosome 2q (Inhibin-beta-b). Furthermore, mRNA expression pattern of coamplified genes in a subset of tumors was analyzed. RESULTS: Our results show that the frequency of gene coamplification on 2p24-25 in neuroblastoma is correlated directly to the physical distance to MYCN. Coamplification is correlated to an upregulated gene expression for DDX1 and NAG. Coamplification of the DDX1 gene within 400kb telomeric to MYCN identifies a subgroup of advanced stage neuroblastoma tumors with a more favorable outcome (P =.027, log-rank test). A high expression level of DDX1 is associated with a trend towards a better survival probability (P =.058, log-rank test). CONCLUSION: Our results indicate that DDX1 coamplification correlates with a better prognosis and improved patient survival in MYCN-amplified neurobastoma.  相似文献   
94.
95.
Purpose: The purpose of this work was to investigate the ovarian renin-angiotensin system (RAS) during severe ovarian hyperstimulation syndrome (OHSS) with ascites and pleural effusion. Methods: Two patients who developed severe OHSS after ovarian stimulation for in vitro fertilization were investigated. Both patients presented ascites and pleural effusion. Blood, ascites, and pleural fluid were simultaneously sampled during therapeutic paracentesis and thoracocentesis. Renin activity, active renin, prorenin, and angiotensin II immunoreactivity (Ang II-ir) were measured simultaneously in plasma, ascites, and pleural fluid. Results: Prorenin, renin activity, active renin, and Ang II-ir levels were much higher than normal plasmatic laboratory norms in the three compartments. Prorenin and Ang II-ir levels were the highest in the ascites, while they were in the same range in the pleural fluid and in the plasma. Conclusions: The present findings provide additional evidence for the ovarian origin of the prorenin and Ang II-ir in the ascites of severe OHSS.  相似文献   
96.
97.
BACKGROUND: We hypothesized that the use of aprotinin would ameliorate the reperfusion injury observed after lung transplantation because of a reduction in the inflammatory response. METHODS: We used an isolated, whole blood-perfused, ventilated rabbit lung model to study the effects of aprotinin during reperfusion. The control animals (group A, n = 8) underwent lung harvest after pulmonary arterial prostaglandin E1 injection and Euro-Collins preservation flush before saline storage for 18 hours at 4 degrees C. The experimental groups received either a low dose (3,000 KIU/mL; group B, n = 8) or a high dose (10,000 KIU/mL; group C, n = 8) of aprotinin added to the pulmonary flush before storage. Each lung was reperfused at 37 degrees C at a rate of 60 mL/min. RESULTS: The arterial partial pressure of oxygen values of group B (low-dose aprotinin) were significantly higher than those of group A (control) after 10 minutes of reperfusion (69.19 +/- 5.69 mm Hg versus 264.30 +/- 48.59 mm Hg, respectively, p = 0.001). Similar results were recorded at 20 and at 30 minutes of reperfusion. Similarly, after 10 minutes of reperfusion, the differences between groups A and C were 69.19 +/- 5.69 mm Hg versus 235.91 +/- 28.63 mm Hg, respectively (p = 0.001). CONCLUSIONS: The addition of aprotinin to the Euro-Collins pulmonary flush significantly improves arterial oxygenation in the early reperfusion period. The enhanced oxygenation suggests that aprotinin may offer protection against early reperfusion injury.  相似文献   
98.
PURPOSE: To evaluate the impact of patient, tumor, and treatment-related factors on outcome in unselected patients with recurrent osteosarcoma. PATIENTS AND METHODS: Five hundred seventy-six consecutive patients who had achieved a first complete surgical remission (CR) during combined-modality therapy on neoadjuvant Cooperative Osteosarcoma Study Group (COSS) protocols and then developed recurrent osteosarcoma were analyzed (median time from biopsy to relapse, 1.6 years; range, 0.1 to 14.3 years). There were 501 patients with metastases, 44 with local recurrences, and 31 with both. Metastases involved lungs (469 patients), bones (90 patients), and/or other sites (54 patients). RESULTS: After a median follow-up of 1.2 years for all patients and 4.2 years for survivors, actuarial overall survival (OS) rates at 2, 5, and 10 years were 0.38, 0.23, and 0.18, respectively. Five-year OS was 0.39 for 339 patients with and 0.00 for 229 patients without a second surgical CR (P < .0001). A long time to relapse, a solitary lesion, and, in the case of pulmonary metastases, unilateral disease and the absence of pleural disruption, were of positive prognostic value in uni- and multivariate analyses, as were a second surgical CR and the use of second-line chemotherapy. Radiotherapy was associated with moderately prolonged survival in patients without a second CR. The very limited prognostic differences associated with the use of second-line chemotherapy appeared to be more pronounced with polychemotherapy. CONCLUSION: Time to relapse and tumor burden correlate with postrelapse outcome in osteosarcoma. Complete surgery is an essential component of curative second-line therapy. Chemotherapy, particularly chemotherapy with more than one agent, may contribute to limited improvements in outcome.  相似文献   
99.
Peritoneal fluid samples from 42 patients with ovarian carcinomas were tested for their suppressive effects on in vitro responses of normal lymphocytes. Suppression was detected both in a natural killer cell assay against K562 cells and in an assay measuring phytohemagglutinin-induced lymphoproliferation. There was no correlation between the level of immunosuppression and the 1-year survival. The greatest suppression was seen in radically operated patients and in patients with normal amounts of peritoneal fluid. Complete suppression was also seen in two patients operated for benign diseases. The results indicate that immunosuppression is not restricted to malignant ascites, but may be a normal function of the peritoneal fluid.  相似文献   
100.
R Yarom  F Bergmann  B Yagen 《Toxicon》1987,25(2):167-174
Topical applications of various doses of T-2 toxin to rats led to delayed skin reactions. Following a dose-dependent latent period of 12-24 hr, there appeared vascular dilation, stasis, edema and mononuclear cell infiltration, with many degranulating mast cells. These signs were earliest and strongest in the subcutis. Epidermal necrosis occurred 1-2 days later and was probably caused secondarily by ischemia, due to microcirculatory failure. Ultrastructurally, endothelial cells of small vessels were the earliest sites of change. While intercellular junctions remained closed and pinocytosis decreased, the cytoplasm contained many ribosomes, vacuoles, and abnormal mitochondria. Another early effect of topical T-2 toxin was an increase in number and degranulation of mast cells, especially in the subcutis. The resemblance of the skin injury to that produced by irradiation is noted.  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