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   7849篇
  免费   434篇
  国内免费   32篇
耳鼻咽喉   30篇
儿科学   275篇
妇产科学   49篇
基础医学   973篇
口腔科学   247篇
临床医学   672篇
内科学   1380篇
皮肤病学   196篇
神经病学   562篇
特种医学   595篇
外科学   934篇
综合类   42篇
预防医学   1286篇
眼科学   161篇
药学   466篇
  1篇
中国医学   5篇
肿瘤学   441篇
  2023年   21篇
  2022年   55篇
  2021年   116篇
  2020年   57篇
  2019年   75篇
  2018年   112篇
  2017年   102篇
  2016年   129篇
  2015年   157篇
  2014年   173篇
  2013年   247篇
  2012年   356篇
  2011年   375篇
  2010年   248篇
  2009年   316篇
  2008年   345篇
  2007年   386篇
  2006年   331篇
  2005年   318篇
  2004年   319篇
  2003年   311篇
  2002年   250篇
  2001年   127篇
  2000年   153篇
  1999年   133篇
  1998年   159篇
  1997年   180篇
  1996年   218篇
  1995年   299篇
  1994年   296篇
  1993年   281篇
  1992年   226篇
  1991年   208篇
  1990年   148篇
  1989年   100篇
  1988年   87篇
  1987年   90篇
  1986年   92篇
  1985年   76篇
  1984年   53篇
  1983年   47篇
  1982年   40篇
  1981年   58篇
  1980年   44篇
  1979年   38篇
  1978年   35篇
  1977年   47篇
  1976年   35篇
  1975年   31篇
  1973年   25篇
排序方式: 共有8315条查询结果,搜索用时 46 毫秒
991.
992.

Background

Accurate quantification of liver fibrosis is essential for therapeutic decision-making and follow-up of chronic liver diseases.

Aims

To optimize the quality of non-invasive assessment of liver fibrosis in patients with chronic hepatopathy we compared Doppler ultrasound with liver histology and transient elastography (TE).

Methods

In this prospective observational study, we performed Doppler ultrasound of hepatic blood vessels as well as TE in 125 patients who underwent liver biopsy for diagnostic work-up of hepatopathy. Hepatic venous flow was evaluated by determining resistance index (HVRI) of the right hepatic vein. Doppler and TE results were compared with histological staging, grading and degree of steatosis obtained by liver biopsy.

Results

HVRI showed a high reliability in predicting fibrosis stage FII or higher (AUROC 93.7 %, HVRI < 1.185; sensitivity 89.66 % and specificity 86.32 %) and was superior to TE. Neither steatosis nor inflammation had significant influence on HVRI-based estimation of fibrosis (1.45 ± 0.2; 1.26 ± 0.05; 1.06 ± 0.06; 0.87 ± 0.08; 0.46 ± 0.11 for F0–FIV, respectively). HVRI differed significantly in different stages of fibrosis. In contrast, portal vein and hepatic artery only showed significant changes in higher stages of fibrosis. Hepatic artery resistance index was elevated (0.67–0.74; p < 0.05); portal vein flow maximum and undulation were significantly reduced in higher fibrosis (p < 0.05 and p < 0.01, respectively).

Conclusions

Hepatic blood flow analysis, especially HVRI, provides useful information during assessment of hepatopathy and is a reliable predictor of liver fibrosis stage FII or higher as part of the non-invasive diagnostic work-up and follow-up in chronic liver disease.  相似文献   
993.
The purpose of this study was to define, in a phase I study in leukemia, the maximally tolerated dose (MTD), major toxicities, and possible antitumor activity of Topotecan, a new topoisomerase I (topo I) inhibitor. Topotecan was delivered by a 5-day continuous infusion every 3 to 4 weeks to patients with refractory or relapsed acute leukemia, at doses ranging from 3.5 mg/m2 to 18 mg/m2 per course. Twenty-seven patients were treated, including 17 patients with acute myelogenous or undifferentiated leukemia, 7 with acute lymphocytic leukemia, and 3 with chronic myelogenous leukemia in blastic phase. Severe mucositis was the dose-limiting toxicity occurring in two of five patients treated with Topotecan 11.8 mg/m2 per course; a third patient had prolonged myelosuppression. At the MTD of 10 mg/m2 per course, 1 of 12 patients had severe mucositis and 5 had mild-to- moderate mucositis. Nausea, vomiting, diarrhea, and prolonged myelosuppression were uncommon. Three patients (11%) achieved a complete response, two (7%) had a partial response, and one (4%) had a hematologic improvement. The overall complete plus partial response rate was 19%, and 24% in acute myelogenous or undifferentiated leukemia. A novel in vitro assay that quantifies Topotecan-stabilized topo I-DNA complexes in patient samples was used, which demonstrated heterogeneity in the ability of Topotecan to interact with topo I, the intracellular target of Topotecan. This phase I study defined the MTD of Topotecan to be 10 mg/m2 by continuous infusion over 5 days every 3 to 4 weeks in patients with refractory or relapsed acute leukemia. Severe mucositis was the dose-limiting toxicity. Future studies will define the precise activity of Topotecan in different leukemia subsets, its efficacy in combination with other antileukemic drugs, and correlations between Topotecan-induced topo I-DNA complex formation and individual patient response to Topotecan.  相似文献   
994.
The very high cure rate in advanced B-cell non-Hodgkin's lymphoma in children using intensive multiagent therapy has been previously reported by the French Societe Francaise d'Oncologie Pediatrique lymphoma Malin B type (LMB) group. To address the issue of salvageability in an unselected group of patients who had all received the same front-line therapy, the outcome of relapses following the LMB 84 (216 patients) protocol have been reviewed. Fourteen percent of patients achieving complete remission (CR) relapsed, ie, 27 of 195. Relapse sites comprised the central nervous system (CNS) alone (6 cases), lung or mediastinum (2 cases), abdomen (8 cases), head and neck (2 cases), or multifocal (9 cases). There were three early deaths due to disease. Twenty-four patients received rescue chemotherapy regimens and 15 were treated with high-dose chemotherapy and bone marrow rescue (1 allogeneic). Of these, 9 were in second CR, 4 in second partial remission, and 2 treated during progressive disease. One died in CR from treatment-related toxicity. Ten relapsed postbone marrow transplant and 4 are alive disease free and probably cured. Two of the long-term survivors had some delay during initial chemotherapy due to toxicity and two were isolated CNS relapses. Twelve of 27 patients did not proceed to megatherapy (12 of 12 died).  相似文献   
995.
We describe our 9-year experience with lectin-treated T-cell-depleted haplocompatible parental bone marrow transplantation (BMT) for 24 patients with severe combined immunodeficiency disease (SCID). Nineteen of 21 evaluable patients had T-cell engraftment; 2 of 11 patients tested had B-cell and monocyte engraftment. Fourteen of 24 (58%) patients are alive 7 months to 9.8 years post-BMT. Seventeen of 24 patients received pretransplant conditioning with chemotherapy and/or total body irradiation, and 8 of 24 received more than one transplant. Patients who received conditioning had a survival rate of 61% versus 57% for those who received no conditioning. None received graft-versus- host disease (GVHD) prophylaxis and no patient had acute or chronic GVHD greater than grade I. Kinetics and follow-up of immune recovery were analyzed in 14 patients who are greater than 1 year from transplant. Half of the patients showed evidence of T-cell function by 3 months and normal T-cell function by 4 to 7 months post-BMT. On average, T-cell numbers and subsets became normal 10 to 12 months posttransplant. Recovery of B-cell function was more delayed, although in most patients B-cell numbers and IgM levels were normal by 12 months post-BMT. B-cell function, as determined by isohemagglutinin titers or specific antibodies to pneumococcal polysaccharide, keyhole limpet hemocyanin, or tetanus toxoid, became normal in 10 of 14 patients 2 to 8 years post-BMT. Seven of the 14 are off gammaglobulin therapy. Production of isohemagglutinins tended to predict recovery of antibody response to pneumococcal polysaccharide (P < .064). Based on these results, we believe that haplocompatible BMT is an effective, curative treatment for patients with SCID who lack an HLA-matched related donor.  相似文献   
996.
Twenty-four patients whose cells contained a variety of 11q23 rearrangements, including translocations, insertions, and an inversion, were studied using fluorescence in situ hybridization with cosmid, phage, and plasmid probes mapped to 11q22-24. In 17 patients, the breakpoints of the common 11q23 translocations involving chromosomes 4, 6, 9, and 19 as well as some uncommon translocations involving 3q23, 17q25, 10p11, and an insertion 10;11 were all located in the breakpoint cluster region of the MLL gene, regardless of age, phenotype of disease, or involvement of a third chromosome. The breakpoints in 11q23 in the other 7 patients with a t(7;11)(p15;q23), inv(11)(p11q23), t(4;11)(q23;q23), der(5)t(5;11)(q13;q23), ins(10;11)(p11;q23q24), t(11;14)(q23;q11), or t(11;18;11) (p15;q21;q23) were located either centromeric to CD3D or telomeric to THY1. Thus, although most 11q23 rearrangements, involve the same breakpoint cluster region of MLL, there is heterogeneity in the breakpoint in some of the rare rearrangements.  相似文献   
997.
Although peripheral blood stem cell collections (PBSC) are thought to have less tumor involvement than bone marrow (BM), the incidence of circulating tumor cells in patients with breast cancer has not been widely investigated. We prospectively investigated the incidence and viability of tumor cell involvement in PBSC and BM collections from breast cancer patients undergoing high-dose chemotherapy/hematopoietic stem cell transplantation. Paired samples of PBSC and BM from 48 patients were analyzed using an immunocytochemical technique that detects one epithelial-derived tumor cell per 5 x 10(5) mononuclear cells. Immunostained tumor cells were detected in 9.8% (13/133) PBSC specimens from 9/48 (18.7%) patients and in 62.3% (38/61) BM specimens from 32/48 (66.7%) patients, a significantly higher rate than in PBSC (P < .005). The geometric mean concentration of tumor cells in contaminated PBSC specimens was 0.8/10(5) mononuclear cells (range 0.33 to 2.0/10(5)) compared with 22.9/10(5) mononuclear cells in BM (range 1 to 3,000/10(5), P < .0001). In culture experiments, clonogenic tumor colonies grew in 21/26 immunocytochemically positive specimens. No tumor colony growth was detected in 30/32 immunocytochemically negative specimens. Immunocytochemical detection of tumor involvement in BM and PBSC correlated significantly with in vitro clonogenic growth (P < .0001). We conclude that PBSC contain fewer tumor cells than paired BM specimens from patients with advanced breast cancer and that these tumor cells appear to be capable of clonogenic growth in vitro.  相似文献   
998.

Background

By taking parameters into account that describe the variability of continuously monitored glucose and long-term metabolic control [hemoglobin A1c (HbA1c)], the glucose pentagon model (GPM) allows characterization of the glucose profile of individual patients with diabetes in a graphical format. A glycemic risk parameter (GRP) derived from this model might allow a better prognosis of the risk to develop diabetes-related complications than the HbA1c.

Methods

To evaluate this hypothesis, we analyzed a subset of data from the Juvenile Diabetes Research Foundation continuous glucose monitoring (CGM) study. The values of the different parameters that are integrated in the GPM were extracted automatically from CGM profiles registered before and after 6 months by means of the Medtronic CGM system in 108 patients.

Results

In these patients, the significant reduction in HbA1c from 7.4% to 7.0% was accompanied by a reduction in glycemia from 164 to 156 mg/dl, standard deviation from 61 to 57 mg/dl, area under the curve >160 mg/dl 29.2 to 23.1, and time per day >160 mg/dl 634 to 576 min. This led to a subsequent reduction in GRP from 3.3 to 2.7; this decrease by 18.2% was significantly larger than that in HbA1c by 8.6% (p < .001). Changes in individual GPMs/GRPs support this observation. They also show the impact of high glycemic variability on GPM/GRP.

Conclusions

Our analysis of data of a study with a considerable sample size and study duration showed that the GPM is not only helpful for rapid assessment of individual glycemic profiles and how therapeutic interventions influence these, but also appears to provide a better prognosis of the risk to develop late complications than the HbA1c per se. However, it is also clear that a true validation of such a model requires performance of a long-term study in a large number of patients with diabetes.  相似文献   
999.
We investigated the use of a new conditioning regimen followed by allogeneic bone marrow transplantation (BMT) for treating children with acute lymphoblastic leukaemia (ALL) after relapse within 6 months of the completion of therapy. One hundred and sixteen children with acute lymphoblastic leukaemia in second or subsequent complete remission (CR) underwent allogeneic bone marrow transplantation from HLA-identical siblings after a preparative regimen comprising total body irradiation (TBI), high-dose cytosine arabinoside and melphalan (TAM regimen). The Kaplan-Meier product-limit estimate (mean ± SE) of disease-free survival (DFS) at 7 years was 59.5 ± 9% (95% confidence interval). The estimated chance of relapse was 22.5 ± 15% with a median follow-up of 88.5 months (range 51–132). 26 patients (22.4%) died with no evidence of recurrent leukaemia, mainly from interstitial pneumonitis, veno-occlusive disease or acute graft-versus-host disease (GVHD). Three factors significantly affected DFS: acute GVHD, site of relapse and, for children in second remission after a marrow relapse, the disease status at the time of transplantation. The DFS were 59.02 ± 12.6%, 37.5 ± 19.8% and 77.4 ± 15% among patients in CR2 after a marrow relapse, in CR3 or in untreated partial marrow relapse, and in CR2 after an isolated CNS relapse, respectively. The lowest DFS was seen in children with acute GVHD grades 3–4. Two significant factors were associated with relapse: the marrow status at the time of transplantation and chronic GVHD. The relapse rate was lower among children in CR2 or with chronic GVHD. We conclude that transplantation after the TAM regimen is an effective therapy for this population with acceptable toxicity, particularly for children in second remission after a very early marrow relapse, or those with early isolated CNS involvement.  相似文献   
1000.
The centrosome plays an important role in maintenance of cell polarity and in progression through the cell cycle by determining the number, polarity, and organization of interphase and mitotic microtubules. By examining a set of 35 high grade human breast tumors, we show that centrosomes of adenocarcinoma cells generally display abnormal structure, aberrant protein phosphorylation, and increased microtubule nucleating capacity in comparison to centrosomes of normal breast epithelial and stromal tissues. These structural and functional centrosome defects have important implications for understanding the mechanisms by which genomic instability and loss of cell polarity develop in solid tumors.  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