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   713篇
  免费   53篇
  国内免费   37篇
耳鼻咽喉   27篇
儿科学   18篇
妇产科学   13篇
基础医学   66篇
口腔科学   17篇
临床医学   111篇
内科学   148篇
皮肤病学   8篇
神经病学   34篇
特种医学   103篇
外国民族医学   1篇
外科学   54篇
综合类   32篇
一般理论   1篇
预防医学   77篇
眼科学   8篇
药学   54篇
肿瘤学   31篇
  2023年   5篇
  2019年   6篇
  2018年   11篇
  2017年   7篇
  2016年   8篇
  2015年   6篇
  2014年   10篇
  2013年   21篇
  2012年   23篇
  2011年   34篇
  2010年   17篇
  2009年   25篇
  2008年   28篇
  2007年   34篇
  2006年   27篇
  2005年   35篇
  2004年   29篇
  2003年   28篇
  2002年   21篇
  2001年   15篇
  2000年   13篇
  1999年   22篇
  1998年   23篇
  1997年   21篇
  1996年   32篇
  1995年   16篇
  1994年   14篇
  1993年   29篇
  1992年   13篇
  1991年   8篇
  1990年   7篇
  1989年   20篇
  1988年   22篇
  1987年   17篇
  1986年   8篇
  1985年   7篇
  1984年   14篇
  1983年   9篇
  1982年   12篇
  1981年   13篇
  1980年   6篇
  1979年   5篇
  1978年   7篇
  1977年   6篇
  1976年   6篇
  1975年   5篇
  1973年   6篇
  1972年   6篇
  1971年   5篇
  1970年   5篇
排序方式: 共有803条查询结果,搜索用时 15 毫秒
51.
The elderly and individuals who have chronic obstructive pulmonary disease (COPD) may be sensitive to particulate matter (PM) air pollution. We evaluated short-term health responses of 13 elderly volunteers with COPD and 6 age-matched healthy adults to controlled exposures of ambient PM pollution in suburban Los Angeles. Using a Harvard particle concentrator and a whole-body chamber, we exposed each person on separate occasions to approximately 200 microg/m(3) concentrated ambient particles (CAP) less than 2.5 mum in diameter and to filtered air (FA). Each exposure lasted 2 h with intermittent mild exercise. We found no significant effects of CAP on symptoms, spirometry, or induced sputum. A significant negative effect of CAP on arterial oxygenation (measured by pulse oximetry) immediately postexposure was more pronounced in healthy subjects. Peripheral blood basophils increased after CAP in healthy but not in COPD subjects. In both groups, red cell counts increased slightly 1 day after exposure to FA but not to CAP. Preexposure ectopic heartbeats were infrequent in healthy subjects, but increased modestly during/after CAP exposure relative to FA. Ectopic beats were more frequent in COPD subjects, but decreased modestly during/after CAP relative to FA. Heart-rate variability over multi-hour intervals was lower after CAP than after FA in healthy elderly subjects but not in COPD subjects. Thus, in this initial small-scale study of older volunteers experimentally exposed to ambient PM, some acute cardiopulmonary responses were consistent with effects reported from epidemiologic studies. Unexpectedly, individuals with COPD appeared less susceptible than healthy elderly individuals. Further investigation of older adults is warranted to understand the pathophysiology and public health significance of these findings.  相似文献   
52.
The sodium-iodide symporter (NIS) is expressed by papillary (PTC) and follicular (FTC) thyroid carcinoma, and is essential for iodine uptake. We hypothesized that PTC and FTC with detectable NIS immunostaining would be more amenable to radioactive iodine ((131)I) treatment and follow a more benevolent course. To test this, we determined NIS expression by immunohistochemistry in 23 PTC, 9 FTC, and 12 benign thyroid lesions from children and adolescents. NIS expression was determined by two blinded examiners and graded as absent = 0, minimal = 1, moderate = 2, intense = 3, and very intense = 4. NIS was detected in 35% (eight of 23) of PTC, 44% (four of 9) of FTC, 25% (two of eight) of benign tumors, and 100% (four of four) of autoimmune lesions. The intensity of NIS expression was similar in PTC (0.61 +/- 0.24), FTC (0.56 +/- 0.24), and benign tumors (0.50 +/- 0.33) but was more intense in autoimmune lesions (3.0 +/- 0.7, p < 0.005). Distant metastases were found only among PTC with undetectable NIS (two of 15, 13%), and recurrence developed exclusively from PTC and FTC with undetectable NIS (four of 20, 20% versus zero of 12, p = 0.043). The dose of iodine 131 required to achieve remission in the five patients with PTC who had undetectable NIS (213.3 +/- 53 mCi) was greater than that required by patients with similar age and extent of disease for whom NIS expression is unknown (109 +/- 22 mCi, p = 0.06). We conclude that NIS expression is associated with a lower risk of recurrence for PTC and FTC of children and adolescents.  相似文献   
53.
INTRODUCTION: Some studies have suggested that ophthalmic nonsteroidal anti-inflammatory drugs (NSAIDs) decrease the pain associated with corneal abrasions without impairing healing. This evidence-based emergency medicine (EBEM) critical appraisal reviews the literature, including additional studies appearing since the publication of an earlier EBEM review in 1999. METHODS: The updated search for randomized controlled trials from 1999 to 2002 complemented the previous 1966 to 1999 search. The methodologic quality of the studies was assessed. Qualitative methods were used to summarize the study results. RESULTS: The search identified 3 studies not included in the previously published review of ophthalmic NSAIDs, yielding a total of 5 blinded, randomized, placebo-controlled trials involving NSAIDs for corneal abrasions. The methodologic quality of the new studies was somewhat higher than that of the 2 original studies and was rated as "good" to "strong." The qualitative summary indicates that NSAIDs provide greater pain relief and improvement of other subjective symptoms when compared with placebo. However, whether the reduction of pain, as measured by visual analog pain scales, exceeds the minimal clinically significant difference is equivocal. The use of ophthalmic NSAIDs may decrease the need for sedating analgesics. CONCLUSION: Ophthalmic NSAIDs appear to be useful for decreasing pain in patients with corneal abrasions who can afford the medication and who must return to work immediately, particularly where potential opioid-induced sedation is intolerable.  相似文献   
54.
55.
Neoadjuvant therapy for organ preservation in head and neck cancer   总被引:2,自引:0,他引:2  
OBJECTIVES/HYPOTHESIS: We designed two sequential trials of induction chemotherapy followed by definitive radiation in patients with potentially resectable head and neck cancer to determine whether organ preservation is feasible without apparent compromise of survival Study Design Both trials were Phase II studies. METHODS: Two clinical trials were conducted sequentially at the University of Michigan. Fifty-two patients enrolled in the first study and were treated with a planned three cycles of carboplatin and 5-fluorouracil. Patients who achieved at least 50% reduction in the size of the primary tumor received definitive radiation therapy, to a dose of 6600 to 7380 cGy. Patients with minimal response or progression had immediate salvage surgery. Thirty-seven patients enrolled in the second trial, in which the chemotherapy consisted of carboplatin, 5-fluororuracil, and leukovorin. Responders were treated with accelerated radiation therapy, to a total dose of 7120 cGy delivered in 41 fractions over 5.5 weeks. RESULTS: Toxicity and response were similar in both trials; therefore, the results are reported first separately and then combined for all 89 patients. Tumor sites included: oropharynx, 55 patients; hypopharynx, 34 patients. Eighty-three percent of patients tolerated all three cycles of chemotherapy and toxicity was mild. Response to chemotherapy was: 48% complete response at the primary tumor site, and 34% partial response at the primary tumor site. Initial organ preservation at individual tumor sites was: oropharynx, 58%; hypopharynx, 59%. Median survival was 28 months, and survival at 3 and 5 years was 40% and 24%, respectively. CONCLUSIONS: These two regimens were well tolerated, and survival did not appear to be compromised by organ preservation treatment compared with historical controls. This approach warrants further investigation, particularly in those patients for whom surgery could be functionally debilitating.  相似文献   
56.
Geographic variation in allergic fungal rhinosinusitis   总被引:4,自引:0,他引:4  
Allergic fungal rhinosinusitis (AFRS) has a worldwide distribution. This survey of 20 otolaryngologic practices throughout the United States confirmed a variation in the frequency of AFRS relative to endoscopic sinus procedures performed for all other diagnoses. The highest incidence occurred in Memphis, Tennessee at 23%, with three other southern practices reporting a frequency of at least 10%. In the northern locations the frequency ranged from 0 to 4%. No correlation with mould counts was demonstrated, possibly because of incomplete mould data relative to most of the surgical locations.  相似文献   
57.
Carboxylesterases constitute a class of enzymes that play important roles in the hydrolytic metabolism of drugs and other xenobiotics, patients with liver conditions such as cirrhosis show increased secretion of proinflammatory cytokines [e. g., interleukin-6 (IL- 6)] and decreased capacity of hydrolysis. In this sfudy, we provide a molecular explanation linking cytokine secretion directly to the decreased capacity of hydrolytic biotransformation. In both primary hepatocytes and HepG2 cells, treatment with IL-6 decreased the expression of human carboxylesterases HCE1 and HCE2 by as much as 60%. The decreased expression occurred at both mRNA and protein levels, and it was confirmed .by enzymatic assay. In cotransfection experiments, both HCE1 and HCE2 promoters were significantly repressed, and the repression was comparable with the decrease in HCE1 and HCE2 mRNA, suggesting that transrepression is responsible for the suppressed expression. In addition, pretreatment with IL-6 altered the cellular responsiveness in an opposite manner of overexpression of HCE1 and HCE2 toward various ester therapeutic agents ( e. g., clopidogrel). Transfection of HCE1, for example, decreased the cytotoxicity induced by antithrombogenic agent clopidogrel, whereas pretreatment with IL-6 increased the cytotoxicity. Such a reversal was observed with other ester drugs, including anticancer agent irinotecan and anti-influenza agent oseltamivir. The altered cellular responsiveness was observed when drugs were assayed at sub-and low-micromolar concentrations, suggesting that suppressed expression of carboxylesterases by IL-6 has profound pharmacological consequences, particularly with those that are hvdrolvzed in an isoform-specific manner.  相似文献   
58.
Eight patients (seven post partum, one post abortion) with massive pelvic hemorrhage related to pregnancy and one patient with uncontrollable bleeding following a cervical biopsy underwent angiography to facilitate the identification and treatment of bleeding sites. In all nine patients pelvic hemorrhage was successfully controlled with embolization under angiographic guidance. Angiographic embolization allowed preservation of the uterus in six patients referred prior to hysterectomy, and one patient subsequently became pregnant. When conservative measures and minor surgical repairs have failed, embolization should be the next step in the treatment of postpartum hemorrhage to avoid major surgery in an unstable patient and to maintain reproductive function.  相似文献   
59.
60.
Using a new technique for antigen localization, we have demonstrated platelet proteins in megakaryocytes in plastic-embedded biopsy specimens of normal human bone marrow. In a series of 25 specimens, megakaryocytes showed labeling with antibodies to the integral membrane glycoproteins IIIa, IIb, and the IIb-IIIa complex; granule membrane protein 140; and five alpha-granule matrix proteins: thrombospondin, factor VIII-related antigen, beta-thromboglobulin, platelet factor 4, and fibrinogen. The antibodies to the membrane glycoproteins IIIa, IIb, and IIb-IIIa produced diffuse cytoplasmic staining and heavier staining on the plasma membrane, whereas the antibodies to the alpha-granule matrix proteins produced a distinct granular staining within the cytoplasm. Staining for granule membrane protein 140 was also granular in distribution. Rare mononuclear cells consistent with megakaryocyte precursors were labeled with these markers. Other enzyme histochemical and lectin-binding studies showed that the enzyme alpha-naphthyl acetate esterase, the lectin Ulex europaeus I, and the periodic-acid Schiff reaction were consistent, but not specific, markers of megakaryocytes. This immunohistochemical technique should facilitate the examination of qualitative and quantitative changes in megakaryocytes in a variety of physiologic and pathologic processes.  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