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   15245篇
  免费   1168篇
  国内免费   252篇
耳鼻咽喉   176篇
儿科学   327篇
妇产科学   508篇
基础医学   1816篇
口腔科学   771篇
临床医学   1506篇
内科学   2970篇
皮肤病学   170篇
神经病学   1517篇
特种医学   548篇
外科学   1980篇
综合类   916篇
一般理论   1篇
预防医学   1018篇
眼科学   435篇
药学   1023篇
  4篇
中国医学   179篇
肿瘤学   800篇
  2023年   125篇
  2022年   203篇
  2021年   331篇
  2020年   232篇
  2019年   256篇
  2018年   315篇
  2017年   307篇
  2016年   299篇
  2015年   417篇
  2014年   428篇
  2013年   597篇
  2012年   695篇
  2011年   856篇
  2010年   638篇
  2009年   591篇
  2008年   725篇
  2007年   780篇
  2006年   716篇
  2005年   647篇
  2004年   622篇
  2003年   605篇
  2002年   581篇
  2001年   480篇
  2000年   451篇
  1999年   411篇
  1998年   217篇
  1997年   200篇
  1996年   172篇
  1995年   144篇
  1994年   159篇
  1993年   132篇
  1992年   239篇
  1991年   235篇
  1990年   207篇
  1989年   212篇
  1988年   202篇
  1987年   163篇
  1986年   174篇
  1985年   169篇
  1984年   116篇
  1983年   119篇
  1982年   81篇
  1980年   70篇
  1979年   87篇
  1978年   82篇
  1977年   72篇
  1975年   95篇
  1974年   71篇
  1973年   64篇
  1972年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
BACKGROUND: Dyslipidaemia, inflammation and oxidative stress are prominent risk factors that potentially cause vascular disease in haemodialysis patients. Dialysis modalities affect uraemic dyslipidaemia, possibly by modifying oxidative stress, but the effects of dialyser flux and membrane material on atherogenic remnant particles and oxidized low-density lipoproteins (LDL) are unknown. METHODS: We performed a randomized crossover study in 36 patients on haemodialysis to analyse the effect of dialyser flux and membrane material on plasma lipids, apolipoproteins and markers of inflammation and oxidative stress. Stable patients on low-flux dialysis with polysulphone for >/=6 weeks were assigned to high-flux polysulphone or high-flux modified cellulose with similar dialyser surface area and permeability characteristics and crossed over twice every 6 weeks. RESULTS: Thirty patients completed the study per protocol. Treatments with high-flux polysulphone and modified cellulose lowered serum triglyceride (by 20% and 10%, respectively; P<0.05) and remnant-like particle cholesterol by 32% (P<0.001) and 11% (NS) after the first 6 weeks of treatment. Oxidized LDL decreased significantly with high-flux polysulphone, but not with modified cellulose. Apolipoproteins CII and CIII were reduced, whereas the ratio CII/CIII was increased (all P<0.05). Acute-phase proteins and LDL and high-density lipoprotein cholesterol remained unaffected. CONCLUSIONS: This randomized crossover study demonstrates a potent effect of high-flux haemodialysis on uraemic dyslipidaemia. Polysulphone membrane material showed superiority on oxidatively modified LDL, an indicator of oxidative stress in haemodialysis patients.  相似文献   
32.
OBJECTIVES: Persisting air leakage after pulmonary resection remains a significant problem. The aim of the study was to evaluate the incidence of air leakage after standard lobectomy and test the efficacy and safety of TachoComb (TC). METHODS: A total of 189 patients undergoing lobectomy were enrolled in a multi-centre, open, randomised, and prospective study to test the efficacy and safety of TachoComb (TC) for air leakage treatment. Air leakage was assessed by water submersion test, and scored as grades 0 if no, 1 if countable, 2 if a stream of and 3 if coalescent bubbles have been observed. Any sites with grade 3 air leakage received further stapling or limited suturing until grade 0, 1 or 2 was obtained. Treatment of air leakage was done with TC or suturing according to randomisation. Air leakage was assessed by further submersion tests. Postoperative air leakage was assessed using the Pleur-Evac system. RESULTS: Overall incidence of air leakage 48+/-6 h after surgery was 34% for TC and 37% for standard treatment (P=0.76). The reduction of intra-operative air leak intensity in the subgroup with grades 1-2 was significantly higher for the TC group (P=0.015). Postoperative air leakage intensity in the subgroup with air leakage grades 1-2 was lower for TC than standard treatment (P=0.047). The mean duration of postoperative air leakage in the subgroup with grades 1-2 was shorter for the TC group than for standard treatment, i.e. 1.9+/-1.4 vs. 2.7+/-2.2 days (P=0.015). CONCLUSIONS: TC could be proven as well-tolerated and safe. In the subgroup of patients with established air leakage, TC showed superior potential in reduction of intra-operative air leakage as well as in reduction of intensity and duration of postoperative air leakage.  相似文献   
33.
Accordingtothedatafromepidemiology,thein-cidenceofcancerrisessteadilywithadvancingage.Age?specificincidenceratesfromtheThirdNationalCancerSurveyoftheUnitedStatesrevealedthattheriskofcancerdevelopmentinthe6thdecadeoflifeisapproximately1%,whichincreasesto2%inthe81styearoflife(1).Theincidencesofmostgyneco-logiccancersincludingcervicalcancer,endometrialcancer,ovariancancerandvulvarcancerpeakaftertheageof60years(2-4).Surgeryisoneofthemaintreatmentoptionsforgynecologiccancerandmaybringaboutsomeeff…  相似文献   
34.
目的 研究在IL 2和IL 4作用下 ,趋化性细胞因子受体CCR3在人生发中心 (germinalcenter,GC)B细胞上的表达及其功能特性。方法 采用流式细胞术检测人GCB细胞上CCR3表达和在CCR3配体eotaxin作用下B细胞的凋亡 ,实时定量RT PCR和Northernblot法检测GCB细胞内CCR3mRNA的表达 ,淋巴细胞趋化和黏附试验检测B细胞的趋化和黏附能力。结果 人GCB细胞极低表达趋化性细胞因子受体CCR3,经IL 2和IL 4作用后 ,GCB细胞高表达CCR3,但此时CCR3不能在其配体作用下诱导GCB细胞的趋化和黏附功能 ,而是诱导GCB细胞凋亡。结论 IL 2和IL 4联合诱导人GCB细胞CCR3表达 ,CCR3可能具有死亡受体的功能。  相似文献   
35.
Cardiac insufficiency, coronary heart disease, and arrhythmia are not only more frequent in elderly patients, they are very often combined. By reason of cardiac morbidity and general morbidity as well as changed physiological and pathophysiological conditions, diagnosis of cardiac disease in elderly patients is more difficult. These conditions also apply to modifications in the therapy of cardiac diseases in advanced age. Especially pharmacodynamic and pharmacokinetic effects in advanced age combined with multimorbidity also account for the risk of interactions because of the simultaneous application of different pharmacological groups.  相似文献   
36.
OBJECTIVES: The use of OKT3 for treatment of advanced high-grade acute rejection episodes eventually can result in cytokine release and consecutive pulmonary edema. Temporary extracorporeal membrane oxygenation (ECMO) bridging can be used to overcome this crucial period before the beneficial effects of OKT3 can be observed. METHODS: We summarize our experience with three patients, who underwent lung transplantation and presented with severe acute rejection episodes. OKT3 had to be initiated due to insufficient response to standard rejection therapy with corticosteroids. Upon initiation of OKT3 treatment, a massive life-threatening deterioration of lung function in spite of heavily invasive respirator treatment was seen and temporary ECMO support was imperative to support graft function. Results of this treatment were retrospectively reviewed. RESULTS: In all cases femoro-femoral veno-arterial ECMO was used for support of the impaired graft and after a period of 4-5 days led to a massive improvement of graft function. In the further course two patients could be discharged from hospital and are still alive 30 and 36 months, respectively, after the described incident. One patient died 4 months later due to liver failure. CONCLUSIONS: We conclude that the use of ECMO support in patients experiencing significant side effects from OKT3 therapy is a useful and effective therapeutic tool to overcome the initial critical period until the lung has sufficiently recovered.  相似文献   
37.
BACKGROUND: Development of more than one primary melanoma in a patient is a relatively uncommon but well-recognized phenomenon. Its frequency has ranged from 1.2% to 8.2% in several series. This subgroup of patients with multiple primary lesions has not been characterized sufficiently. We report the experience of the Melanoma Unit of University Hospital Spedali Civili of Brescia, Italy. METHOD: Study subjects were drawn from 1240 patients with histologically confirmed melanoma, including melanoma in situ. From this group, multiple melanomas developed in 47 patients (3.79%). Every one of our patients has been taught to perform self-examination of the skin to detect suspicious pigmented lesions. RESULTS: Of the 47 patients described in this study, 38 had two primary melanomas, 7 had three melanomas and 2 had 5 and 10 melanomas, respectively. Mean age at first diagnosis was 46.2 years. The majority of subsequent melanomas (74.5%) were removed within 5 years of the initial operation. Synchronous lesions were found in 10 patients. In male patients, the lesion appeared most frequently on the trunk; in female patients, melanoma appeared mostly on the lower extremities. The second primary melanomas developed in the same anatomic region from the first in 53.2% of our patients. The proportion of in situ to invasive melanomas was greater for the second melanomas compared with the first melanomas. Regarding invasive melanomas, the mean thickness of the first melanomas was 1.31 mm compared with 0.66 mm for the second ones. Dividing patients into two groups, of more and less than 50, it is highlighted that in older patients synchronous lesions appear more frequently (36.4% vs. 8.0%); the median time interval between sequential melanomas is longer (84 vs. 63.7 months); and the ratio between the primary and secondary melanoma mean thickness is lower (1.21 : 1.08 vs. 1.43 : 0.63 mm). CONCLUSIONS: The study confirms that second primary melanoma is usually thinner than the first lesion, and it is more common in the same region of the body as the initial melanoma. The highest risk for a second melanoma is during the first 5 years, but a much longer time interval of 28 years is possible. Continued medical follow-up with complete skin examinations seems prudent, but it is very important to promote self-skin evaluation in patients to detect not only metastases but also subsequent primary melanomas in their earliest phases.  相似文献   
38.
39.
目的 研究α-黑素细胞刺激素(α-MSH)对脑缺血-再灌注后脑组织炎性细胞浸润及粘附分子(ICAM-1)表达的影响。方法用线栓法建立大鼠大脑中动脉栓塞(MCAO)模型,治疗组腹腔注射α-MSH,用髓过氧化物酶(MPO)定量测定法评价脑缺血组织中中性粒细胞浸润程度,免疫组化法检测ICAM-1表达情况,并电镜观察超微结构的改变。结果 α-MSH能明显改善细胞超微结构的损害;α-MSH治疗组再灌注后脑组织ICAM-1表达明显下调,MPO含量减少,与脑缺血组比较有显著差异(P<0.05)。结论 α-MSH能减轻脑缺血-再灌注后脑组织炎性细胞浸润及粘附分子(ICAM-1)表达,对脑缺血再灌注损伤具有保护作用。  相似文献   
40.
H P Haber  N Benda  G Fitzke  A Lang  M Langenberg  J Riethmüller    M Stern 《Gut》1997,40(3):406-411
BACKGROUND: Colonic strictures represent an advanced stage of fibrosing colonopathy in patients with cystic fibrosis. AIMS: To clarify whether ultrasonography can identify patients with an early stage of fibrosing colonopathy and to determine clinical factors that influence bowel wall thickening. PATIENTS: Ninety patients with cystic fibrosis, median age 10 years, and 46 healthy controls, median age 13 years, were investigated. METHODS: Bowel wall thickness was measured by ultrasound in a prospective study. RESULTS: In cystic fibrosis, wall thickness of both small intestine and colon was significantly (p < 0.0001) higher than in controls; 81% of patients with cystic fibrosis had a maximum colon wall thickness at any site of 2 mm or more, a value that was never reached by controls. The maximum colon wall thickness was 6.5 mm. Bowel wall thickness was unchanged at re-examination after one year. There was no progression even with high dose pancreatic supplements. There was no association between bowel wall thickness and clinical features such as previous meconium ileus, intestinal resection, distal intestinal obstruction syndrome, abdominal pain, or pancreatic enzyme dose. CONCLUSIONS: There is genuine intestinal involvement in cystic fibrosis; in a few cases this could lead to fibrosing colonopathy.  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