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   17573篇
  免费   3442篇
  国内免费   75篇
耳鼻咽喉   262篇
儿科学   388篇
妇产科学   404篇
基础医学   1293篇
口腔科学   438篇
临床医学   5177篇
内科学   2843篇
皮肤病学   310篇
神经病学   1773篇
特种医学   388篇
外科学   2628篇
综合类   346篇
一般理论   8篇
预防医学   2287篇
眼科学   584篇
药学   762篇
中国医学   10篇
肿瘤学   1189篇
  2023年   512篇
  2022年   142篇
  2021年   315篇
  2020年   446篇
  2019年   245篇
  2018年   769篇
  2017年   814篇
  2016年   731篇
  2015年   774篇
  2014年   920篇
  2013年   1044篇
  2012年   616篇
  2011年   671篇
  2010年   720篇
  2009年   828篇
  2008年   542篇
  2007年   617篇
  2006年   569篇
  2005年   531篇
  2004年   544篇
  2003年   451篇
  2002年   439篇
  2001年   483篇
  2000年   392篇
  1999年   478篇
  1998年   382篇
  1997年   362篇
  1996年   404篇
  1995年   294篇
  1994年   292篇
  1993年   227篇
  1992年   365篇
  1991年   357篇
  1990年   306篇
  1989年   299篇
  1988年   292篇
  1987年   277篇
  1986年   257篇
  1985年   182篇
  1984年   175篇
  1983年   140篇
  1982年   117篇
  1981年   107篇
  1980年   97篇
  1979年   134篇
  1978年   116篇
  1977年   98篇
  1975年   96篇
  1974年   130篇
  1973年   114篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
BACKGROUND: Stringent transcranial Doppler (TCD) criteria for diagnosing occlusion are needed for more reliable TCD performance at bedside in the acute stroke setting. SUBJECTS AND METHODS: At three academic stroke centers, we performed TCD examination for patients with symptoms of cerebral ischemia who underwent digital subtraction angiography (DSA). We used a standard insonation protocol with power M-mode Doppler (PMD) TCD (TCD 100 M, Spencer Technologies Inc., Seattle, WA). We collected mean flow velocity (MFV), pulsatility indices (PI), and power M-mode resistance signature (absent, high, or low) in symptomatic middle (MCA), anterior (ACA), posterior (PCA), and in affected (a), ipsilateral (i), and contralateral (c-lat) cerebral arteries. Ratios of aMCA/c-lat MCA, aMCA/iACA, and aMCA/iPCA MFV were subsequently calculated. PMD-TCD flow findings were evaluated with a receiver-operating characteristic (ROC) analysis for angiographically proven MCA occlusion. RESULTS: We studied 120 patients with acute cerebral ischemia with PMD-TCD examinations prior to or immediately after DSA. Lower aMCA velocities pointed to higher probability of occlusion (P= .055). The aMCA/iPCA MFV ratio was superior to the aMCA/iACA ratio and strongly predictive of occlusion at a threshold ratio of 0.5 (RR 2.31 CI(95) 2.13-2.51). High resistance or absent M-mode flow signatures in the proximal MCA were present in 87% of M1 and M2 MCA occlusions (probability 87%). In the presence of a low-resistance PMD signature, obtaining the aMCA/iPCA MFV ratio <0.5 increases probability of occlusion to 87%. Normal MFV ratios and low-resistance M-mode signatures are highly predictive of a negative angiogram for MCA occlusion. CONCLUSION: In acute cerebral ischemia, reliable criteria for proximal MCA occlusion have been developed based on combination of MFV ratios and M-mode flow resistance signatures. Validation of these criteria will require multicenter studies.  相似文献   
22.
23.
High levels of tumor necrosis factor-alpha (TNF-alpha), a pro-inflammatory cytokine, are present in the wound fluid of chronic nonhealing wounds. This leads to increased inflammation, cytokine expression, and ultimately results in impaired wound healing and tissue destruction. Etanercept is a recombinant fusion protein that consists of the soluble TNF receptor (p75) linked to the Fc portion of human IgG1. It is an effective inhibitor of TNF-alpha and has been shown to provide rapid and sustained improvement in rheumatoid arthritis by acting as a soluble receptor binding TNF-alpha and preventing its proinflammatory activities. Therefore, the aim of this study was to determine whether Etanercept could inhibit TNF-alpha activity in chronic wound fluid. Wound fluid was collected from the venous leg ulcers of 16 different patients. The effect of Etanercept on TNF-alpha activity was evaluated using both a TNF-alpha bioassay and an enzyme-linked immunoassay. Etanercept was found to reduce the cytotoxic effect of chronic wound fluid on L929 fibroblasts by approximately 30% and neutralized TNF-alpha binding in the enzyme-linked immunoassay by up to 80%. Direct application of Etanercept to chronic wounds may therefore reduce the inflammatory activity of TNF-alpha, which could reduce the chronicity of venous leg ulcers and thus aid in the healing of these wounds.  相似文献   
24.
25.
26.
Summary: This is the first report of the largest study of blood pressure measurement in pregnancy in a New Zealand population using standardized definitions and methodology. Over 3,800 women who delivered in an 8-month period in the Wellington region were included in the study. Blood pressure measurement and the presence of oedema and proteinuria were recorded from booking until delivery and in the puerperium. Only 2.7% of women were unable to be contacted after delivery for details on outcomes. The results established normal ranges for blood pressure throughout pregnancy. The data show that Mood pressure greater than 140/90 until 35 weeks' gestation is outside 2 standard deviations at all gestations and justifies using these measurements as the definition of hypertension in pregnancy. The fall in blood pressure in the 2nd trimester was less than 1 mm Ffg per week in both the systolic and diastolic pressures. This fall was smaller than previously recorded in other studies. Gestational hypertension was the commonest blood pressure abnormality occurring in 15.2% of the population. This represented 69% of the pregnant women with a hypertensive disorder. The overall incidence of both gestational hypertension and preeclampsia was 18.5% which is higher than reported in other parts of the world. In this study obesity was significantly associated with hypertensive disorders in pregnancy. An arm circumference of >33 cm, one of the measurements of obesity, was found in 6.8% of the study population. Even after the effect of arm circumference was taken into account, hypertensive disorders were also more common in Pacific Island women. Ankle oedema was significantly associated with the development of both gestational hypertension and preeclampsia but the incidence of oedema was noted in only 11.9% of the subjects.  相似文献   
27.
28.
Surgical management of 100 consecutive esophageal strictures   总被引:1,自引:0,他引:1  
We report our experience with 100 consecutive patients with reflux-induced esophageal structure managed surgically. Preoperative dilatation, total fundoplication gastroplasty, and postoperative dilatation were used in 98 patients. Only two required resection of the esophageal structure. We have identified preoperative factors that adversely affect the results. These include scleroderma; previous operation, either esophageal or gastric, and the severity of the esophageal stricture. Results of nonresectional operations are excellent in uncomplicated cases or with the addition of only one complicating factor. The more complicating factors, the worse the results. Those patients with three preoperative complicating factors do poorly and may benefit from esophageal resection. We conclude that results obtained from this conservative nonresectional management program justify continuance of the use of total fundoplication gastroplasty with preoperative and postoperative dilatation in the management of such patients.  相似文献   
29.
The use of adjuvant radiation therapy in breast cancer patients treated with mastectomy and adjuvant chemotherapy has been controversial. In order to assess the necessity and effectiveness of adjuvant radiation therapy in this setting, we reviewed the results in 510 patients with T1-T3 tumors and pathologically positive nodes or tumors larger than 5 cm and negative nodes who were treated with adjuvant chemotherapy. Patients with four or more positive nodes or at least one positive apical node were randomized to receive either five or ten cycles of cyclophosphamide/Adriamycin (Adria Laboratories, Columbus, OH) (CA) and patients with one to three positive nodes or operable tumors larger than 5 cm and pathologically negative nodes were randomized to receive eight cycles of either cyclophosphamide, methotrexate, and 5-fluorouracil (5-FU) (CMF) or methotrexate and 5-FU (MF) chemotherapy. Two hundred six of these patients were subsequently rerandomized to receive either no further treatment or adjuvant radiotherapy. Thirty-five patients withdrew after randomization, including 34 who declined to receive radiotherapy. Radiation therapy consisted of 4,500 cGy in 5 weeks to the chest wall and appropriate draining lymph nodes. Median follow-up from chemotherapy randomization is 45 months for patients in the CA arm and 53 months for those in the CMF/MF arm. The crude rate of local failure (chest wall or draining lymph node areas) as first site of failure for patients randomized to receive chemotherapy only was 14%; for those randomized to receive both chemotherapy and radiotherapy it was 5% (P = .03). For patients in the CMF/MF arm, the rate of local failure as the first site of failure was nearly the same for patients randomized to chemotherapy only as for those randomized to adjuvant radiotherapy as well (5% v 2%). For patients in the CA arm, the crude rate of local failure was 20% for patients randomized to receive chemotherapy only, and 6% for those randomized to both types of adjuvant treatment (P = .03). Among the 43 patients treated with CA who actually received radiotherapy, there was only one local failure, compared with 12 local failures among the 59 patients (20%) who actually did not receive radiotherapy (P = .007). No significant difference was seen in disease-free survival or overall survival in either the CA or the CMF/MF arm between patients randomized to receive radiation therapy and those randomized to no further treatment.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
30.
目的:讨论在院前和急诊科对创伤性休克病人施行早期急救护理,对挽救病人的生命及伤情预后有重要的意义.方法:对我科1997年2月至2001年4月27例创伤性休克病人进行早期,快速,积极的补液,输血增加有效循环量,监测生命体征等综合性抢救治疗与护理措施.结果:经早期积极急救护理,26例病人收缩压维持在60mmHg以上,意识清醒,脉搏有力,转入手术室或专科治疗,1例病人伤势严重抢救无效死亡.结论:创伤性休克病人,伤势复杂,死亡率高,伤后早期院前与急诊科的有效救护,是提高抢救成功率的关键.  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