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   1950篇
  免费   112篇
  国内免费   13篇
耳鼻咽喉   10篇
儿科学   97篇
妇产科学   109篇
基础医学   171篇
口腔科学   45篇
临床医学   176篇
内科学   373篇
皮肤病学   45篇
神经病学   103篇
特种医学   175篇
外科学   165篇
综合类   138篇
预防医学   139篇
眼科学   10篇
药学   116篇
  1篇
中国医学   74篇
肿瘤学   128篇
  2021年   22篇
  2020年   21篇
  2019年   17篇
  2018年   26篇
  2017年   31篇
  2016年   25篇
  2015年   48篇
  2014年   51篇
  2013年   58篇
  2012年   76篇
  2011年   60篇
  2010年   59篇
  2009年   57篇
  2008年   70篇
  2007年   60篇
  2006年   59篇
  2005年   39篇
  2004年   37篇
  2003年   36篇
  2002年   21篇
  2001年   54篇
  2000年   29篇
  1999年   30篇
  1998年   45篇
  1997年   58篇
  1996年   49篇
  1995年   44篇
  1994年   55篇
  1993年   36篇
  1992年   21篇
  1991年   20篇
  1990年   16篇
  1989年   30篇
  1988年   30篇
  1987年   35篇
  1986年   26篇
  1985年   19篇
  1984年   18篇
  1983年   17篇
  1982年   13篇
  1981年   24篇
  1980年   17篇
  1959年   36篇
  1958年   59篇
  1957年   87篇
  1956年   45篇
  1955年   75篇
  1954年   67篇
  1953年   17篇
  1952年   14篇
排序方式: 共有2075条查询结果,搜索用时 15 毫秒
51.
Simon  SI; Rochon  YP; Lynam  EB; Smith  CW; Anderson  DC; Sklar  LA 《Blood》1993,82(4):1097-1106
We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to beta 2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and beta 2- integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the beta 2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an approximately 50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by approximately 50%. We examined the aggregation of neutrophils from patients genetically deficient in beta 2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and beta 2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the beta 2-integrin and the other expressed the L- selectin adhesive epitope.  相似文献   
52.
53.
Petrequin  PR; Todd  RF d; Smolen  JE; Boxer  LA 《Blood》1986,67(4):1119-1125
The widespread assumption that cytoplasts generated from human polymorphonuclear leukocytes (PMNs) are vesicles consisting solely of cytoplasm surrounded by plasma membrane and devoid of granule activity remains to be tested. PMN cytoplasts were prepared by centrifugation of intact cells on a Ficoll step gradient in the presence of cytochalasin B. Two granule membrane markers, Mol, a fluorometrically detectable antigen, and cytochrome b, both of which have been shown to translocate to the plasma membrane during granule release, were compared for their activity in cytoplasts and intact PMNs. We found that the amount of Mol detected on the plasma membrane of intact PMNs, as compared with other membrane markers (such as antigens LFA-1 and beta 2m), increased 1.6- fold upon exposure of PMNs to Ficoll plus cytochalasin B prior to centrifugation. Another twofold increase in Mol expression occurred upon cytoplast preparation. Release of the granule enzymes, vitamin B12- binding protein, and lysozyme were also followed and correlated well (r = .78 and .92) with the amount of Mol antigen present on the cell surface. Cytochrome b was also found to be higher (1.4-fold) on plasma membranes isolated from cytoplasts than on plasma membranes isolated from intact control cells. These results indicate that some fusion of granule membranes and plasma membranes occurred during treatment of PMNs with Ficoll plus cytochalasin b and during cytoplast preparation.  相似文献   
54.
55.
Phospholipase A2 levels in acute chest syndrome of sickle cell disease   总被引:4,自引:2,他引:4  
Acute chest syndrome (ACS) is associated with significant morbidity and is the leading cause of death in patients with sickle cell disease (SCD). Recent reports suggest that bone marrow fat embolism can be detected in many cases of severe ACS. Secretory phospholipase A2 (sPLA2) is an important inflammatory mediator and liberates free fatty acids, which are felt to be responsible for the acute lung injury of the fat embolism syndrome. We measured SPLA2 levels in 35 SCD patients during 20 admissions for ACS, 10 admissions for vaso-occlusive crisis, and during 12 clinic visits when patients were at the steady state. Eleven non-SCD patients with pneumonia were also evaluated. To determine if there was a relationship between sPLA2 and the severity of ACS we correlated SPLA2 levels with the clinical course of the patient. In comparison with normal controls (mean = 3.1 +/- 1.1 ng/mL), the non- SCD patients with pneumonia (mean = 68.6 +/- 82.9 ng/mL) and all three SCD patient groups had an elevation of SPLA2 (steady state mean = 10.0 +/- 8.4 ng/mL; vaso-occlusive crisis mean = 23.7 +/- 40.5 ng/mL; ACS mean = 336 +/- 209 ng/mL). In patients with ACS sPLA2 levels were 100- fold greater than normal control values, 35 times greater than values in SCD patients at baseline, and five times greater than non-SCD patients with pneumonia. The degree of SPLA2 elevation in ACS correlated with three different measures of clinical severity and, in patients followed sequentially, the rise in SPLA2 coincided with the onset of ACS. The dramatic elevation of SPLA2 in patients with ACS but not in patients with vaso-occlusive crisis or non-SCD patients with pneumonia and the correlation between levels of SPLA2 and clinical severity suggest a role for SPLA2 in the diagnosis and, perhaps, in the pathophysiology of patients with ACS.  相似文献   
56.
The objective of this study is to describe a case-series of potassium aluminium tetrafluoride (KAlF4)-induced occupational asthma (OA) and/or occupational rhinitis (OR). The study involves five patients from a heat-exchanger production line who were examined (including specific inhalation challenge tests) for suspected OA and/or OR caused by a flux containing almost 100% KAlF4 − with fluorides’ workplace air concentrations ranging between 1.7 and 2.8 mg/m3. No subject had a previous history of asthma. All five patients had a positive specific challenge test (three patients were diagnosed with OA alone, one with OR and one with both OR and OA). At the follow-up visit, after three years on average, all patients needed permanent corticosteroid therapy (four topical, one oral). After elimination from the exposure, only one of the observed subjects gave an indication of an improvement, two subjects stabilized and two worsened. Our case series focuses on the correlation between patients’ exposure to fluorides in air-conditioner production and the subsequent occurrence of OR/OA. Currently, it is uncertain whether these OR/OA were caused by hypersensitivity or irritation.  相似文献   
57.
目的探讨腹腔镜手术对不孕症患者的诊断及治疗价值。方法回顾性分析新疆医科大学第一附属医院2010年9月-2014年5月收治的319例不孕症患者的临床资料,对所有患者行腹腔镜下诊断及相应的手术治疗(包括盆腔粘连分解、输卵管造口术、输卵管灼断术等)。结果 319例患者腹腔镜术中检查与术前子宫输卵管碘油造影结果的符合率为72.1%(230/319),其中有43例术中发现子宫肌瘤,56例术中发现输卵管系膜囊肿,8例患者术中发现子宫内膜异位症,有2例患者诊断为盆腔结核,1例术中发现结肠肌瘤(术前考虑卵巢囊肿),其余为不同程度的盆腔慢性炎症。轻度粘连69例,妊娠21例,宫外孕2例,妊娠率33.33%。中重度粘连250例,其中行灼断术34例,灼断术患者后行体外受精及胚胎移植(IVF-ET),妊娠13例,妊娠率38.23%(13/34)。其余216例,失访3例,妊娠31例,宫外孕3例、妊娠率15.9%。结论腹腔镜对诊断输卵管性不孕及盆腔疾病有重要价值,子宫输卵管造影仅能初级筛查,诊断价值有限。在治疗输卵管粘连梗阻中,腹腔镜的治疗价值有待进一步探讨,临床预后与盆腔炎症的程度有关,应个体化选择手术方案。  相似文献   
58.
59.
Liver metastases from differentiated thyroid carcinoma (LMDTC) are rare and usually occur in disseminated metastatic disease. The aim of this study was to review the diagnosis and management of LMDTC. Between 1995 and 2011, 14 patients with a mean age of 59.7 years (+/-10.2) were treated for LMDTC. Data were retrospectively reviewed and analyzed. Seven patients had distant metastases at diagnosis, including 2 with synchronous liver lesions. The average time of onset of LMDTC from initial diagnosis was 52.2 months (+/49.5). All LMDTC were discovered during routine radiologic monitoring. Histologic analysis confirmed LMDTC in 5 patients. Eight patients received tyrosine kinase inhibitors, 1 patient underwent resection of their LMDTC after chemotherapy. Six patients (disseminated metastases, significant comorbidities) did not receive any specific treatment. The median survival after diagnosis of LMDTC was 17.4 months (+/-3.3): 23.6 months (+/-2.9) for patients who underwent chemotherapy versus 3.9 months (+/-0.9) for patients who did not receive any specific treatment (P < 0.001). Developing DTC liver metastasis is a very poor prognostic sign. Chemotherapy by TKIs, especially, hold promise in the cure of LMDTC for selected patients.Key words: Liver metastasis, Thyroid carcinomaDifferentiated thyroid carcinoma, encompassing follicular and papillary carcinomas, has a good prognosis and long-term survival rates. Indeed, the 10-year survival rate is 80–95%. The incidence of distant metastases at the time of initial presentation of differentiated thyroid carcinoma (DTC) is 4%. During the course of treatment and follow-up, the prevalence of distant metastases ranges from 2% in low-risk patients, to 33% in high-risk patients. Distant metastases occur primarily in the lungs and, to a lesser extent, in bones. The presence of distant metastases is the most significant prognostic factor and is associated with poor outcomes. Only 50% of patients survive 10 years after a diagnosis of the metastatic DTC.13Liver metastases from differentiated thyroid carcinoma (LMDTC) are rare, with a reported frequency of 0.5%. They tend to occur during the terminal phase of the disease are a grave event. Survival ranges from 1 to 60 months after diagnosis of LMDTC in the largest series of 11 cases.4Because of this rarity, there is little information available on the diagnosis and management of LMDTC. We have therefore undertaken a retrospective, multicenter study on LMDTC and analyzed factors affecting survival.  相似文献   
60.
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