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   17829篇
  免费   1285篇
  国内免费   67篇
耳鼻咽喉   127篇
儿科学   547篇
妇产科学   537篇
基础医学   2476篇
口腔科学   291篇
临床医学   2033篇
内科学   3368篇
皮肤病学   478篇
神经病学   1798篇
特种医学   492篇
外科学   1875篇
综合类   113篇
一般理论   7篇
预防医学   1951篇
眼科学   423篇
药学   1054篇
  1篇
中国医学   19篇
肿瘤学   1591篇
  2024年   25篇
  2023年   234篇
  2022年   355篇
  2021年   686篇
  2020年   465篇
  2019年   582篇
  2018年   757篇
  2017年   509篇
  2016年   604篇
  2015年   670篇
  2014年   824篇
  2013年   1109篇
  2012年   1630篇
  2011年   1600篇
  2010年   811篇
  2009年   759篇
  2008年   1162篇
  2007年   1175篇
  2006年   1025篇
  2005年   947篇
  2004年   825篇
  2003年   752篇
  2002年   713篇
  2001年   86篇
  2000年   50篇
  1999年   76篇
  1998年   106篇
  1997年   101篇
  1996年   62篇
  1995年   52篇
  1994年   49篇
  1993年   56篇
  1992年   39篇
  1991年   24篇
  1990年   21篇
  1989年   19篇
  1988年   7篇
  1987年   8篇
  1986年   18篇
  1985年   16篇
  1984年   18篇
  1983年   16篇
  1982年   23篇
  1981年   12篇
  1980年   10篇
  1979年   8篇
  1978年   10篇
  1977年   9篇
  1971年   8篇
  1967年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
PURPOSE: Vaccines, cytokines, and other biologic-based therapies are being developed as antineoplastic agents. Many of these agents are designed to induce an autologous immune response directed against the malignancy. In contrast, hematopoietic stem-cell transplantation is being developed as a form of allogeneic immunotherapy. This study tests the tolerance and antineoplastic activity of sequential infusions of partially HLA-matched allogeneic blood mononuclear cells (obtained from relatives) when administered outside of the context of a hematopoietic stem-cell transplantation. The cells are irradiated to prevent graft-versus-host disease. PATIENTS AND METHODS: Fifteen patients with relapsed or refractory malignancies for which no standard therapy was available were enrolled onto a clinical trial designed to assess the tolerability and antineoplastic effects of irradiated partially HLA-matched blood mononuclear cells obtained from relatives. RESULTS: There was disease regression in three patients with metastatic renal cell carcinoma during treatment. There was disease progression in six patients with metastatic renal cell carcinoma and two patients with metastatic melanoma during treatment. There was no change in disease state in several other patients. CONCLUSION: Irradiated allogeneic blood mononuclear cells administered outside the context of hematopoietic stem-cell transplantation may induce disease responses in patients with relapsed or refractory malignancies. Transfusion of irradiated allogeneic blood mononuclear cells should be developed further as a novel therapeutic antineoplastic approach.  相似文献   
62.
Foetal abdominal cysts are frequently found on routine antenatal ultrasound. Various sonographic features might help in their differential diagnosis. However, a definitive diagnosis is often not made until postnatal life, and detection of an intra‐abdominal cyst antenatally rarely alters obstetric management. A review of possible causes of a foetal abdominal cyst is presented.  相似文献   
63.
Psoas abscess in children, and especially in neonates, is an uncommon condition which is difficult to diagnose clinically. The US, CT and MR findings of a psoas abscess in a neonate, which extended to the thigh, are reported. Imaging was helpful in revealing the abnormality, in demonstrating its extension and in determining its nature. The child was treated conservatively and the abscess resolved, leaving atrophy of the psoas muscle. Received: 24 June 1997 Accepted: 9 January 1998  相似文献   
64.
Zusammenfassung. Die Klonierung, Sequenzierung und Produktion von hochreinen Allergenen bietet die Möglichkeit, perfekt standardisierte Allergenpräparate herzustellen. Die Entwicklung eines neuen Klonierungssystems, das auf filamentösen Phagen basiert, führte zu einer schnellen Isolierung und Charakterisierung von Aspergillus fumigatus-Allergenen. Die auf diesem Weg rekombinant hergestellten Proteine wurden serologisch und klinisch geprüft und ihr routinemä-ßiger Einsatz im ImmunoCAP-System evaluiert. Es gelang eine quantitative Übereinstimmung zwischen Hauttestergebnissen und Serologie nachzuweisen, welche das Potential rekombinanter Allergene in der Diagnostik allergischer Krankheiten aufzeigt. Darüber hinaus trägt die Charakterisierung der Pilzallergene wesentlich zum Verständnis der moiekularen Natur der allergieauslösenden Komponenten bei Zum jetzigen Zeitpunkt können, abgesehen von Proteinen mit unbekannten biologischen Funktionen, die Pilzallergene in zwei Klassen eingeteilt werden: 1. Spezies-spezifische sezcrnierte Allergene und 2. cytoplasmatische, hoch konservierte Proteine. Diese letztgenannten Pilzallergene zeigen auch zu Proteinen aus phylogenetisch weit entfernten Organismen weitreichende Sequenzhomologien. Neben der daraus zu erwartenden IgE-Kreuzreaktivität findet man in einigen Fällen auch eine Kreuzreaktivität mit den homologen humanen Proteinen, was auf Autoimmunreaktionen, bei Pilzalleigien hindeutet. Summary. Cloning, sequencing and production of highly pure recombinant allergens allows to produce perfectly standardised allergen preparations. The development of a new cloning system based on filamentous phage allowed the fast isolation and characterisation of allergens from the fungus Aspergillus fumigatus. The produced recombinant allergens were tested in serological and clinical studies as well as for their performance for routine assessments in the ImmunoCAP-system. Thereby, a perfect correlation between skin test results and serology was found showing the potential of recombinant allergens for the diagnosis of allergic diseases. Moreover, the characterisation of fungal allergens substantially contributes to our understanding of the molecular nature of proteins involved in the elication of allergic reactions. Apart from allergenic proteins with unknown biological function, fungal allergens can be subdivided into two classes: 1. Species-specific, secreted proteins and 2. cytoplasmic, even in phylogenetically distant organisms, well conserved proteins. These fungal allergens show extended sequence similarity, a high level of IgE cross-reactivity and in some cases also cross-reactivity with homologous human proteins indicating autoimmune reactions involved in fungal allergy.  相似文献   
65.
MR imaging of the neonatal brain at 3 Tesla   总被引:1,自引:0,他引:1  
3 Telsa MR scanners are now becoming more widely available and 3 Telsa is likely to become the filed strength of choice for clinical imaging of the brain. The neonatal brain can be safely and successfully imaged at 3 Telsa. The improved signal to noise afforded by a higher field strength may be used to improve image quality or shorten acquisition times. This may be exploited for conventional T1 and T2 weighted imaging and also for advanced techniques such as diffusion tensor imaging, angiography and functional magnetic resonance studies.  相似文献   
66.
OBJECTIVE: Elevated levels of umbilical cord nucleated red blood cells (nRBCs) have been used to assess in utero hypoxia. Although the umbilical nRBC value has been the 'gold standard', umbilical blood may not be obtained at delivery. We determined if the levels of nRBCs and white blood cell (WBC) counts in fixed placental sections might serve as a proxy for cord blood values. STUDY DESIGN: Umbilical blood and placenta were collected from 25 deliveries at Harbor-UCLA Medical Center. Umbilical blood and placental sections were analyzed for nRBCs (per 100 WBC) and WBC differential, and compared with the t-test or the Mann-Whitney rank sum test. RESULTS: nRBC counts were equivalent in umbilical cord and placental sections (5 vs. 4/100 WBC). Umbilical lymphocyte and polymorphonuclear leukocyte (PMN) counts were normally distributed, averaging 35 +/- 9 and 56 +/- 2/100 WBC, respectively. Placental lymphocyte (33 +/- 2/100 WBC) and PMN (60 +/- 2/100 WBC) counts were equivalent to cord blood values. CONCLUSION: WBC differentials and nRBC counts are equivalent in umbilical cord blood and processed placental pathology sections. For infants in whom cord blood cell counts are desired though umbilical cord samples are unavailable, fixed placental sections may serve as a proxy.  相似文献   
67.
BACKGROUND AND PURPOSE: Predictive factors for local-regional (LR) failures after parotid-sparing, Intensity modulated (IMRT) or 3D conformal radiotherapy for head and neck (HN) cancers were assessed. PATIENTS AND METHODS: One hundred and fifty-eight patients with mostly stages III-IV HN squamous cell carcinoma underwent curative bilateral neck irradiation aimed at sparing the parotid glands. Patient, tumor, and treatment factors were analyzed as predictive factors for LR failure. RESULTS: Twenty-three patients had LR recurrence (19 in-field and four marginal). No differences were found in the doses delivered to the PTVs of patients with or without in-field recurrences. In univariate analysis, tumor site was highly predictive for LR failure in both postoperative and definitive RT patients. In postoperative RT patients, pathologic tumor size, margin status, extracapsular extension (ECE) and number of lymph node metastases, were also significantly predictive. Multivariate analysis showed tumor site (oropharynx vs. other sites) to be a significant predictor in all patients, and involved margins and number of involved lymph nodes in postoperative patients. CONCLUSIONS: Clinical rather than dosimetric factors predicted for LR failures in this series, and were similar to those reported following standard RT. These factors may aid in the selection of patients for studies of treatment intensification using IMRT.  相似文献   
68.
PURPOSE: Epstein-Barr virus (EBV) in Hodgkin's lymphoma (HL) cells has been considered as a prognostic marker for this heterogeneous disease, but studies have yielded mixed findings, likely because of selected patient series and failure to acknowledge an effect of age on outcome. This study assessed survival after HL in a population-based cohort large enough to examine the joint effects of EBV with other factors including age, sex, and histologic subtype. PATIENTS AND METHODS: Included were 922 patients with classical HL diagnosed between mid-1988 and 1997 in the Greater San Francisco Bay Area, with archived biopsy specimens assayed for EBV with immunohistochemistry and in situ hybridization. Vital status was followed through December 30, 2003 (median follow-up time, 97 months). Overall and disease-specific survival were analyzed with the Kaplan-Meier method and Cox proportional hazards regression models. RESULTS: In children less than 15 years old, EBV presence was suggestively associated (P = .07) with favorable survival. In adults aged 15 to 44 years, EBV did not affect HL outcome, although a protective effect was suggested. In older adults (45 to 96 years), EBV presence nearly doubled the risk of overall and HL-specific mortality but only for patients with nodular sclerosis (NS) histologic subtype (hazard ratio for death = 2.5; 95% CI, 1.5 to 4.3). CONCLUSION: In HL, EBV tumor cell presence is associated with better survival in young patients and poorer survival in older patients with NS, independent of other factors. Variation in outcome by age and histology could indicate biologically distinct disease entities. Evidence that EBV is a meaningful prognostic marker may have therapeutic relevance.  相似文献   
69.
70.
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