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   30020篇
  免费   1650篇
  国内免费   268篇
耳鼻咽喉   254篇
儿科学   587篇
妇产科学   642篇
基础医学   3116篇
口腔科学   712篇
临床医学   2135篇
内科学   8566篇
皮肤病学   367篇
神经病学   2544篇
特种医学   1151篇
外科学   5545篇
综合类   59篇
一般理论   6篇
预防医学   1185篇
眼科学   538篇
药学   1744篇
中国医学   62篇
肿瘤学   2725篇
  2024年   32篇
  2023年   305篇
  2022年   631篇
  2021年   1074篇
  2020年   603篇
  2019年   875篇
  2018年   1024篇
  2017年   755篇
  2016年   901篇
  2015年   940篇
  2014年   1264篇
  2013年   1572篇
  2012年   2381篇
  2011年   2281篇
  2010年   1303篇
  2009年   1245篇
  2008年   1963篇
  2007年   1909篇
  2006年   1800篇
  2005年   1789篇
  2004年   1681篇
  2003年   1446篇
  2002年   1288篇
  2001年   190篇
  2000年   192篇
  1999年   222篇
  1998年   222篇
  1997年   179篇
  1996年   180篇
  1995年   169篇
  1994年   142篇
  1993年   132篇
  1992年   152篇
  1991年   113篇
  1990年   105篇
  1989年   82篇
  1988年   77篇
  1987年   66篇
  1986年   74篇
  1985年   64篇
  1984年   53篇
  1983年   50篇
  1982年   69篇
  1981年   37篇
  1980年   34篇
  1979年   38篇
  1978年   23篇
  1976年   24篇
  1974年   19篇
  1970年   17篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
PURPOSE: Stroma cells play a relevant role in tumor development and progression. We investigated the activity of herceptin (HER), a humanized monoclonal antibody widely used for the treatment of HER2-overexpressing epithelial cancer, toward stroma cell lines L87/4 and L88/5. EXPERIMENTAL DESIGN: We studied the antiproliferative potential of HER and role of human serum in HER activity. We also investigated the ability of HER to alter ancillary functions of L87/4 and L88/5, such as support to long-term hematopoiesis, growth factor production, breast cancer cell adhesion, and proliferation. RESULTS: Flow cytometry showed that HER2 membrane expression in L87/4 and L88/5 stroma cells was intermediate between the expression in HER2-negative/dim MCF-7 breast cancer cells and HER2-bright SK-BC3 breast cancer cells. HER2 gene amplification was not detected by fluorescence in situ hybridization in either stromal cell lines. HER significantly inhibited L87/4 and L88/5 proliferation. Mean ID(50)s were found to be 2000 and 1700 micro g/ml for L87/4 and L88/5, respectively, after 3-day exposure and 800 micro g/ml for both cell lines after 9-day exposure. The presence of 10% human serum in the culture increased HER inhibitory activity. IC(50) of stroma cells was found to be intermediate between HER2-bright breast cancer cells (SK-BC3) and HER2-negative/dim breast cancer cells (MCF-7). The drug did not significantly affect the ability of stroma cells to support long-term hematopoiesis in the cobblestone area forming cell assay. In contrast, in coculture assay, MCF7 cells demonstrated a worse adhesion and growth capability on HER-treated stroma layers when compared with untreated stroma. Moreover, HER significantly reduced vascular endothelial growth factor production by L88/5 cells. CONCLUSIONS: Our data support the novel finding that HER may have a relevant activity against stroma cells.  相似文献   
102.
OBJECTIVE: To determine the relationship between p53 overexpression and vascular endothelial growth factor (VEGF) upregulation in liver and abdominal metastases from colon cancer. The analysis in the two metastatic sites was carried out to evaluate the potential role of microenvironment in the molecular regulation of VEGF. METHODS: Bioptic specimens of liver and abdominal metastases from colon carcinomas were examined by immunohistochemistry for p53 and VEGF expressions. Consecutive cases with assessable tumor tissue were selected. RESULTS: The study population consisted of 24 cases having liver metastases and 34 cases having abdominal metastases. Abdominal metastases showed a higher number of VEGF-positive cases and a higher intensity of VEGF immunoreactivity than liver metastases did (p = 0.01). The combined analysis of p53 and VEGF showed a strong association between the two markers in the 24 liver metastases; 9 cases were VEGF positive/p53 positive and 15 cases were VEGF negative/p53 negative. This relationship was not found in the 34 abdominal metastases, which showed concordance between the two markers in 9 VEGF-positive/p53-positive cases only. CONCLUSIONS: Microenvironment factors like hypoxia may have a predominant role in inducing VEGF expression and they can override the molecular control of p53 on VEGF.  相似文献   
103.
Purpose: A new technique is presented for in vivo measurements of the dose equivalent from photoneutrons produced by high-energy radiotherapy accelerators.Methods and Materials: The dosimeters used for this purpose are vials of superheated halocarbon droplets suspended in a tissue-equivalent gel. Neutron interactions nucleate the formation of bubbles, which can be recorded through the volume of gel they displace from the detector vials into graduated pipettes. These detectors offer inherent photon discrimination, dose-equivalent response to neutrons, passive operation, and small sensitive size. An in vivo vaginal probe was fabricated containing one of these neutron detector vials and a photon-sensitive diode. Measurements were carried out in patients undergoing high-energy x-ray radiotherapy and were also repeated in-phantom, under similar irradiation geometries.Results and Conclusion: Neutron doses of 0.02 Sv were measured in correspondence to the cervix, 50 cm from the photon beam axis, following a complete treatment course of 46.5 Gy with an upper mantle field of 18-MV x-rays. This fraction of dose from neutrons is measured reliably within an intense photon background, making the technique a valid solution to challenging dosimetry problems such as the determination of fetal exposure in radiotherapy. These measurements can be easily carried out with tissue-equivalent phantoms, as our results indicate an excellent correlation between in vivo and in-phantom dosimetry.  相似文献   
104.
We present a 70-year-old woman with pre-B acute lymphoblastic leukemia in whom serial imaging studies showed the development of multiple vertebral collapse, and communicating superior and inferior Schmorl’s nodes creating a longitudinal channel (”tunneling” Schmorl’s nodes) through the anterior aspect of T12 to L3 vertebral bodies of her osteoporotic thoracolumbar spine. This was observed after achieving complete remission of the disease and during maintenance therapy. The finding is felt to be secondary to iatrogenic exacerbation of osteoporosis. Received: 26 May 2000 Revision requested: 23 June 2000 Revision received: 10 July 2000 Accepted: 13 July 2000  相似文献   
105.
Children with cognitive disabilities are at greater risk of experiencing pain. It has been shown that this paediatric population often receive inadequate pain management. Pain may be very difficult to assess, especially in a defined subgroup with non‐communicating intellectual disability or severe cognitive disability. Accordingly, several observational pain assessment tools have been proposed to overcome this issue. Due to the absence of an ideal measurement tool, accurate pain assessment requires, after a case‐by‐case analysis, selecting the more appropriate tool or a variety of combined instruments. The aim of this work is to provide a comprehensive review of the pain assessment tools commonly used in cognitively impaired children. Critical discussion on features and clinical applicability may suggest how to overcome this difficult challenge. Furthermore, this review will help further research aiming to design new instruments and to improve already‐in‐use tools.  相似文献   
106.
107.
Deep vein thrombosis results from the cooperative action of leukocytes, platelets, and endothelial cells. The proline-rich tyrosine kinase Pyk2 regulates platelet activation and supports arterial thrombosis. In this study, we combined pharmacological and genetic approaches to unravel the role of Pyk2 in venous thrombosis. We found that mice lacking Pyk2 almost completely failed to develop deep venous thrombi upon partial ligation of the inferior vena cava. Pyk2-deficient platelets displayed impaired exposure of phosphatidylserine and tissue factor expression by endothelial cells and monocytes was completely prevented by inhibition of Pyk2. In human umbilical vein endothelial cells (HUVEC), inhibition of Pyk2 hampered IL-1β-induced expression of VCAM and P-selectin, and von Willebrand factor release. Pyk2-deficient platelets showed defective adhesion on von Willebrand factor and reduced ability to bind activated HUVEC under flow. Moreover, inhibition of Pyk2 in HUVEC strongly reduced platelet adhesion. Similarly, Pyk2-deficient neutrophils were unable to efficiently roll and adhere to immobilized endothelial cells under venous flow conditions. Moreover, platelets and neutrophils from Pyk2-knockout mice showed defective ability to form heterogeneous aggregates upon stimulation, while platelet monocyte interaction occurred normally. Consequently, platelet neutrophil aggregates, abundant in blood of wild-type mice upon inferior vena cava ligation, were virtually undetectable in Pyk2-knockout mice. Finally, we found that expression of Pyk2 was required for NETosis induced by activated platelets. Altogether our results demonstrate a critical role of Pyk2 in the regulation of the coordinated thromboinflammatory responses of endothelial cells, leukocytes and platelets leading to venous thrombosis. Pyk2 may represent a novel promising target in the treatment of deep vein thrombosis.  相似文献   
108.
Nanoporous Au has been subjected to serial block face-scanning electron microscopy (SBF-SEM) 3D-characterisation. Corresponding sections have been digitalized and used to evaluate the associated mechanical properties. Our investigation demonstrates that the sample is homogeneous and isotropic. The effective Young’s modulus estimated by an analytical multiscale approach agrees remarkably well with the values stated in the literature.  相似文献   
109.
Simple SummaryGlioblastoma is an aggressive brain tumor with a dismal prognosis. In a minority of cases, it presents with multiple lesions already at the time of diagnosis, affecting patients’ survival and treatment. Our retrospective study aims to increase the current understanding and define a treatment for this sub-entity, to improve patient survival. Chemoradiotherapy is a also safe and efficacy treatment in patients with multiple lesions. Survival advantages from extensive resection remain unclear.AbstractGlioblastomas with multiple foci at presentation (mGBMs) account for 2–35% of all GBMs. mGBMs have limited existing data and no standardized treatment. This study aims to determine their incidence, demographic and clinical features, outcome, and prognostic factors in terms of overall survival. We performed a monocentric retrospective study, reviewing patients treated at the Istituto Oncologico Veneto. Inclusion criteria were: new diagnosis of GBM and presence of multiple lesions on pre-treatment MRI. ECOG PS was used to evaluate clinical condition, RANO criteria for radiological assessment, and CTCAE v5.0 for treatment-related adverse events. The incidence of newly diagnosed mGBM was 7.2% and the study population consisted of 98 patients. Median age was 63 years, M:F ratio of 1.8:1, and a surgical approach was undertaken in 73 patients (mostly partial resection). MGMT was methylated in 47.5%, and 82 patients received active oncological treatment (65.9% radiotherapy plus temozolomide (RT + TMZ)). The disease control rate with RT + TMZ was 63%. Median OS of the entire study population was 10.2 months (95% CI 6.6–13.8), and median PFS was 4.2 months (95% CI 3.2–5.2). The ECOG PS, the extent of resection, and the RT + TMZ were significant prognostic factors in the univariate analysis for OS, but only the RT + TMZ was a significant independent OS predictor in the multivariate analysis (HR = 3.1, 95% IC 1.3–7.7, p = 0.014). The incidence of mGBM is not rare. RT + TMZ is confirmed to be an independent prognostic factor for survival and a safe and effective treatment. When feasible, RT + TMZ should be considered as a possible first-line treatment. The role of the extent of resection is still unclear.  相似文献   
110.
Intraperitoneal administration of quercetin (6.25–50 mg/kg) significantly (p<0.5-0.01) reduced intestinal transit in mice and this effect was antagonized by yohimbine and phentolamine but not by atropine or naloxone. Quercetin (12.5–50 mg/kg) reduced also (p<0.05-0.01) intraluminal accumulation of fluid and diarrhoea induced by castor oil and these effects were antagonized by yohimbine. Finally quercetin (12.5–50 mg/kg) reduced the area of gastric ulcer but not the number. It is suggested that α2-adrenergic receptors mediate the effect of quercetin on intestinal motility and secretion.  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