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   9879篇
  免费   969篇
  国内免费   18篇
耳鼻咽喉   168篇
儿科学   392篇
妇产科学   205篇
基础医学   1302篇
口腔科学   128篇
临床医学   984篇
内科学   1713篇
皮肤病学   357篇
神经病学   1018篇
特种医学   470篇
外科学   1289篇
综合类   239篇
一般理论   5篇
预防医学   1243篇
眼科学   145篇
药学   688篇
中国医学   4篇
肿瘤学   516篇
  2021年   103篇
  2020年   71篇
  2019年   112篇
  2018年   137篇
  2017年   131篇
  2016年   100篇
  2015年   122篇
  2014年   202篇
  2013年   301篇
  2012年   339篇
  2011年   370篇
  2010年   235篇
  2009年   221篇
  2008年   399篇
  2007年   493篇
  2006年   417篇
  2005年   375篇
  2004年   375篇
  2003年   359篇
  2002年   354篇
  2001年   340篇
  2000年   405篇
  1999年   320篇
  1998年   192篇
  1997年   146篇
  1996年   153篇
  1995年   149篇
  1994年   141篇
  1993年   121篇
  1992年   281篇
  1991年   227篇
  1990年   264篇
  1989年   224篇
  1988年   236篇
  1987年   202篇
  1986年   203篇
  1985年   227篇
  1984年   140篇
  1983年   107篇
  1982年   116篇
  1981年   79篇
  1980年   80篇
  1979年   117篇
  1978年   106篇
  1977年   87篇
  1976年   104篇
  1975年   83篇
  1974年   93篇
  1973年   93篇
  1972年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To investigate the numbers, clinical characteristics, resource use, and outcomes of admissions who met precise clinical and physiologic criteria for severe sepsis (as defined in the PROWESS trial) in the first 24 hrs in the intensive care unit. DESIGN: Observational cohort study, with retrospective analysis of prospectively collected data. SETTING: Ninety-one adult general intensive care units in England, Wales, and Northern Ireland between 1995 and 2000. PATIENTS: Patients were 56,673 adult admissions. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We found that 27.1% of adult intensive care unit admissions met severe sepsis criteria in the first 24 hrs in the intensive care unit. Most were nonsurgical (67%), and the most common organ system dysfunctions were seen in the cardiovascular (88%) and respiratory (81%) systems. Modeling the data for England and Wales for 1997 suggested that 51 (95% confidence interval, 46-58) per 100,000 population per year were admitted to intensive care units and met severe sepsis criteria in the first 24 hrs.Of the intensive care unit admissions who met severe sepsis criteria in the first 24 hrs, 35% died before intensive care unit discharge and 47% died during their hospital stay. Hospital mortality rate ranged from 17% in the 16-19 age group to 64% in those >85 yrs. In England and Wales in 1997, an estimated 24 (95% confidence interval, 21-28) per 100,000 population per year died after intensive care unit admissions with severe sepsis in the first 24 hrs.For intensive care unit admissions who met severe sepsis criteria in the first 24 hrs, median intensive care unit length of stay was 3.56 days (interquartile range, 1.50-9.32) and median hospital length of stay was 18 days (interquartile range, 8-36 days). These admissions used 45% of the intensive care unit and 33% of the hospital bed days used by all intensive care unit admissions. CONCLUSIONS: Severe sepsis is common and presents a major challenge for clinicians, managers, and healthcare policymakers. Intensive care unit admissions meeting severe sepsis criteria have a high mortality rate and high resource use.  相似文献   
992.
993.
994.
Osteocalcin (OC), a major noncollagenous bone matrix protein, is expressed prevalently in prostate cancer epithelial cells, adjacent fibromuscular stromal cells, and osteoblasts in locally recurrent prostate cancer and prostate cancer bone metastasis [Matsubara, S., Wada, Y., Gardner, T.A., Egawa, M., Park, M.S., Hsieh, C.L., Zhau, H.E., Kao, C., Kamidono, S., Gillenwater, J.Y., and Chung, L.W. (2001). Cancer Res. 61, 6012-6019]. We constructed an adenovirus vector carrying osteocalcin promoter-driven herpes simplex virus thymidine kinase (Ad-OC-hsv-TK) to cotarget prostate cancer cells and their surrounding stromal cells. A phase I dose escalation clinical trial of the intralesional administration of Ad-OC-hsv-TK followed by oral valacyclovir was conducted at the University of Virginia (Charlottesville, VA) in 11 men with localized recurrent and metastatic hormone-refractory prostate cancer (2 local recurrent, 5 osseous metastasis, and 4 lymph node metastasis) in order to determine the usefulness of this vector for the palliation of androgen-independent prostate cancer metastasis. This is the first clinical trial in which therapeutic adenoviruses are injected directly into prostate cancer lymph node and bone metastasis. Results show that (1). all patients tolerated this therapy with no serious adverse events; (2). local cell death was observed in treated lesions in seven patients (63.6%) as assessed by TUNEL assay, and histomorphological change (mediation of fibrosis) was detected in all posttreated specimens; (3). one patient showed stabilization of the treated lesion for 317 days with no alternative therapy. Of the two patients who complained of tumor-associated symptoms before the treatment, one patient with bone pain had resolution of pain, although significant remission of treated lesions was not observed by image examination; (4). CD8-positive T cells were predominant compared with CD4-positive T cells, B cells (L26 positive), and natural killer cells (CD56 positive) in posttreated tissue specimens; (5). levels of HSV TK gene transduction correlated well with coxsackie-adenovirus receptor expression but less well with the titers of adenovirus injected; and (6). intrinsic OC expression and the efficiency of HSV TK gene transduction affected the levels of HSV TK protein expression in clinical specimens. Our data suggest that this form of gene therapy requires further development for the treatment of androgen-independent prostate cancer metastasis although histopathological and immunohistochemical evidence of apoptosis was observed in the specimens treated. Further studies including the development of viral delivery will enhance the efficacy of Ad-OC-hsv-TK.  相似文献   
995.
BACKGROUND: Hepatitis G virus (HGV) is a blood-borne flavivirus that may cause acute and chronic transfusion-transmitted infections. Patients with complement component 1 (C1) inhibitor (C1-INH) deficiency may acquire blood-borne infections through infusion of plasma concentrates. STUDY DESIGN AND METHODS: Serum samples from 84 patients with C1-INH deficiency (19 who received unmodified C1-INH concentrates, 23 who received steam-heated concentrates, and 42 untreated patients) were tested for HGV RNA and hepatitis C virus (HCV) RNA by a nested polymerase chain reaction (PCR). The samples were also tested for antibodies to the E2 envelope protein of HGV (anti-HGV) and to HCV with enzyme-linked immunosorbent assays. RESULTS: Nine (11%) patients had serum HGV RNA; that is, 7 (17%) of 42 patients previously treated with C1-INH concentrates and 2 of 42 previously untreated patients. HGV RNA was as common in the 19 patients treated with unmodified concentrates as in the 23 given steam-heated concentrates (16 vs. 17%, p = 0.60). Anti-HGV was more common among the recipients of unmodified concentrates than among those given steam-heated concentrates (26 vs. 0%, p = 0.014). HCV RNA was more frequently detected in treated patients than in untreated patients (33 vs. 7%, p = 0.005) and in the 19 recipients of unmodified concentrates than in the 23 treated with steam-heated concentrates (58 vs. 16%, p = 0.003). Only one HGV RNA- seropositive patient had elevated serum aminotransferase activity, compared to 11 with HCV RNA. CONCLUSION: HGV was transmitted by both unmodified and steam-heated concentrates, but it caused persistent viremia in a minority of the cases and was rarely associated with liver disease.  相似文献   
996.
Background: Previous studies have demonstrated the efficacy of oxycodone and hydrocodone for the treatment of acute pain. However, to the best of the authors' knowledge, no previous reports have compared the efficacies of these commonly prescribed agents. Objectives: To compare the efficacies of oxycodone and hydrocodone for the treatment of acute pain associated with fractures in emergency department (ED) patients. Methods: This prospective, double‐blind, randomized, controlled trial was conducted at an urban trauma center with an annual census of 65,000. Eligible participants included ED patients over the age of 12 years with fractures who consented to participate. Subjects were randomized to receive either oxycodone (5 mg orally [po]) with acetaminophen, or hydrocodone (5 mg po) with acetaminophen. Measurements included demographic information; pain scores on a verbal numeric rating scale at baseline and at 30 and 60 minutes; vital signs at baseline and at 30 and 60 minutes; and adverse effects. Ninety‐five‐percent confidence intervals (95% CIs) constructed about means and proportions were used to assess differences between the oxycodone and hydrocodone groups in analgesic efficacy and side effects. Results: Seventy‐three subjects were randomized to receive oxycodone or hydrocodone. Sixty‐seven subjects completed the ED study period (n= 35, oxycodone; n= 32, hydrocodone). There was no difference between the two groups in age, weight, gender, ethnicity, diagnoses, baseline pain scores, or vital signs. Patients in both groups had pain relief from baseline to 30 minutes (oxycodone mean change 3.7, 95% CI = 2.9 to 4.6; hydrocodone mean change 2.5, 95% CI = 1.7 to 3.3), and from baseline to 60 minutes (oxycodone mean change 4.4, 95% CI = 3.2 to 5.6; hydrocodone mean change 3.0, 95% CI = 2.1 to 3.9). There was no difference in pain between the patients treated with oxycodone and hydrocodone at 30 minutes (mean difference between groups ?0.6, 95% CI =?1.8 to 0.5) or at 60 minutes (mean difference ?0.5, 95% CI =?2.0 to 1.0). There was no difference between the groups in nausea, vomiting, itching, or drowsiness; however, the hydrocodone patients had a higher incidence of constipation (oxycodone 0%, hydrocodone 21%, difference in proportions 21%, 95% CI = 3% to 39% more with hydrocodone). Conclusions: Treatment with acetaminophen and either oxycodone, 5 mg po, or hydrocodone, 5 mg po, resulted in pain relief among ED patients with acute fractures, and there was no difference between the two agents at 30 and 60 minutes. Adverse effect profiles were similar, with the exception of a higher incidence of subsequent constipation with the use of hydrocodone. These results suggest that oxycodone and hydrocodone have similarly potent analgesic effects in the first hour of treatment for ED patients with acute fractures.  相似文献   
997.
Bangladesh is a young, struggling nation that is emerging with strong religious and family networks and a positive hope for the future. Children are viewed as the step toward that future. The attitudes toward handicapped children were explored by examining the available health services and then conducting a survey of parents of handicapped children. Since there are few treatment facilities and these are located in cities, many children do not receive treatment. Family-oriented treatment in which therapeutic activities are incorporated into the child's daily routine and where therapists can train the child and family members, periodically reassess the child, and provide guidance and advice when necessary may be an effective way to treat handicapped children. Unlike more developed nations, the families of Bangladesh were not interested in institutions for their handicapped children, and expressed hope even in the face of serious disabilities. Providing training to these families could perhaps help them achieve that hope.  相似文献   
998.
Oxygen-haemoglobin dissociation curves were determined on dogs' blood using a modified and miniaturised dissociation curve analyser. The Bohr factor describes the way in which pH varies the PO2 corresponding to a particular oxyhaemoglobin concentration. The factor was similar for three saturations and was little affected by whether the pH was changed by changing PCO2, or by adding fixed acid or alkali. The haemoglobin saturations in the mid-range tended to be lower than those predicted by the equation of Rossing and Cain (1966)  相似文献   
999.
Data quality in a distributed data processing system: the SHEP Pilot Study   总被引:1,自引:0,他引:1  
The Systolic Hypertension in the Elderly Program (SHEP) Pilot was a collaborative clinical trial that distributed to the clinics all data processing tasks except for randomization assignment codes and morbidity and mortality data. The clinics used customized programs to enter and verify data interactively, to maintain their own local master files, and to transmit the data electronically to the Coordinating Center. We measured quality control based on criteria from centralized as well as distributed models: the error rate for baseline forms was 0.5 per 1000 items. Ninety-eight percent of the forms were query-free, and a central reentry of the data in a 5% sample yielded a miskey rate of 2 per 1000 items. The potential problems of distributed data processing are vulnerability of the local master files and the time demands on Coordinating Center programmers for maintaining clinic computer systems. The advantages are the active involvement of clinic staff in their own quality control, the functional accessibility of the clinics to the Coordinating Center in controlling protocol decisions and data monitoring, and the level of accuracy, completeness, and timeliness of the data that can be achieved.  相似文献   
1000.
Adverse reactions in blood donors with a history of seizures or epilepsy   总被引:1,自引:0,他引:1  
BACKGROUND: Individuals with epilepsy or seizure disorders are restricted from donating blood because of concern that they are prone to adverse donor reactions such as syncope and convulsions. A study evaluating whether that concern is warranted is reported. STUDY DESIGN AND METHODS: During a 2-year period beginning in 1987, blood donors in Maryland with a history of seizures were actively recruited by the American Red Cross. Adverse donor reactions were classified as "slight", indicating dizziness and nausea without loss of consciousness; "moderate," denoting syncope; and "severe," indicating convulsive syncope. RESULTS: There were 329,143 satisfactory blood donations; 613 individuals reporting a history of seizures donated blood a total of 723 times. Among donors with seizures, 186 (35.7%) were taking antiepileptic medication, and 61 (8.4%) had had one or more seizures in the preceding year. Individuals with seizures had a low incidence of adverse reactions (3.34%). Although this incidence was slightly higher than that in the entire population (2.24%), the difference was not significant. In particular, the risk of syncope with or without convulsive activity was low for people with seizures (0.21%) and not significantly greater than that in other donors (0.28%). CONCLUSION: Individuals with seizures or epilepsy are not at greater risk for adverse reactions after blood donation, and major restrictions on their participation as blood donors are not warranted.  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