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   8258篇
  免费   540篇
  国内免费   9篇
耳鼻咽喉   61篇
儿科学   132篇
妇产科学   141篇
基础医学   923篇
口腔科学   103篇
临床医学   1110篇
内科学   1449篇
皮肤病学   99篇
神经病学   719篇
特种医学   482篇
外国民族医学   1篇
外科学   943篇
综合类   100篇
一般理论   8篇
预防医学   1114篇
眼科学   99篇
药学   575篇
中国医学   6篇
肿瘤学   742篇
  2023年   37篇
  2022年   68篇
  2021年   154篇
  2020年   86篇
  2019年   166篇
  2018年   207篇
  2017年   141篇
  2016年   146篇
  2015年   196篇
  2014年   249篇
  2013年   497篇
  2012年   654篇
  2011年   688篇
  2010年   383篇
  2009年   367篇
  2008年   579篇
  2007年   568篇
  2006年   542篇
  2005年   534篇
  2004年   546篇
  2003年   581篇
  2002年   488篇
  2001年   94篇
  2000年   84篇
  1999年   108篇
  1998年   93篇
  1997年   60篇
  1996年   52篇
  1995年   52篇
  1994年   43篇
  1993年   38篇
  1992年   32篇
  1991年   40篇
  1990年   24篇
  1989年   15篇
  1988年   16篇
  1987年   15篇
  1986年   13篇
  1985年   19篇
  1984年   15篇
  1983年   11篇
  1982年   9篇
  1980年   5篇
  1979年   5篇
  1977年   8篇
  1976年   8篇
  1975年   5篇
  1973年   9篇
  1970年   6篇
  1968年   5篇
排序方式: 共有8807条查询结果,搜索用时 31 毫秒
71.
BackgroundPulmonary contusions are common injuries. Computed tomography reveals vast contused lung volume spectrum, yet pulmonary contusions are defined dichotomously (unilateral vs bilateral). We assessed whether there is stepwise increased risk of pulmonary complications among patients without, with unilateral, and with bilateral pulmonary contusion.MethodsWe identified adults admitted with rib fractures using the largest US inpatient database. After propensity-score-matching patients without vs with unilateral vs bilateral pulmonary contusions and adjusting for residual confounders, we compared risk for pneumonia, ventilator-associated pneumonia (VAP), respiratory failure, intubation, and mortality.ResultsAmong 148,140 encounters of adults with multiple rib fractures, 19% had concomitant pulmonary contusions. Matched patients with pulmonary contusions had increased risk of pneumonia 19% [95%CI:16–33%], respiratory failure 40% [95%CI: 31–50%], and intubation 46% [95%CI: 33–61%]. Delineation showed bilateral contusions, not unilateral contusions, attributed to increased risk of complications.ConclusionsThere is likely a correlation between contused lung volume and risk of pulmonary complications; dichotomously classifying pulmonary contusions is insufficient. Better understanding this correlation requires establishing the clinically significant contusion volume and a correspondingly refined classification system.  相似文献   
72.
BACKGROUND CONTEXTSurgery for vertebral column tumors is commonly associated with intraoperative blood loss (IOBL) exceeding 2 liters and the need for transfusion of allogeneic blood products. Transfusion of allogeneic blood, while necessary, is not benign, and has been associated with increased rates of wound complication, venous thromboembolism, delirium, and death.PURPOSETo develop a prediction tool capable of predicting IOBL and risk of requiring allogeneic transfusion in patients undergoing surgery for vertebral column tumors.STUDY DESIGN/SETTINGRetrospective, single-center study.PATIENT SAMPLEConsecutive series of 274 patients undergoing 350 unique operations for primary or metastatic spinal column tumors over a 46-month period at a comprehensive cancer centerOUTCOME MEASURESIOBL (in mL), use of intraoperative blood products, and intraoperative blood products transfused.METHODSWe identified IOBL and transfusions, along with demographic data, preoperative laboratory data, and surgical procedures performed. Independent predictors of IOBL and transfusion risk were identified using multivariable regression.RESULTSMean age at surgery was 57.0±13.6 years, 53.1% were male, and 67.1% were treated for metastatic lesions. Independent predictors of IOBL included en bloc resection (p<.001), surgical invasiveness (β=25.43 per point; p<0.001), and preoperative albumin (β=?244.86 per g/dL; p=0.011). Predictors of transfusion risk included preoperative hematocrit (odds ratio [OR]=0.88 per %; 95% confidence interval [CI, 0.84, 0.93]; p<0.001), preoperative MCHgb (OR=0.88 per pg; 95% CI [0.78, 1.00]; p=0.048), preoperative red cell distribution width (OR=1.32 per %; 95% CI [1.13, 1.55]; p<0.001), en bloc resection (OR=3.17; 95%CI [1.33, 7.54]; p=0.009), and surgical invasiveness (OR=1.08 per point; [1.06; 1.11]; p<0.001). The transfusion model showed a good fit of the data with an optimism-corrected area under the curve of 0.819. A freely available, web-based calculator was developed for the transfusion risk model (https://jhuspine3.shinyapps.io/TRUST/).CONCLUSIONSHere we present the first clinical calculator for intraoperative blood loss and transfusion risk in patients being treated for primary or metastatic vertebral column tumors. Surgical invasiveness and preoperative microcytic anemia most strongly predict transfusion risk. The resultant calculators may prove clinically useful for surgeons counseling patients about their individual risk of requiring allogeneic transfusion.  相似文献   
73.
An audit of 265 intensive care unit (ICU) admissions from the operating room was performed for the year 1991. In a quality assurance exercise we identified 34 unanticipated ICU admissions (UIAs) by a retrospective peer review of the medical charts. Of these UIAs, 16 were deemed predictable and seven preventable. Five of the seven potentially preventable UIAs were judged to have had inappropriate intravenous fluid management. This has prompted changes in our education programme. In an assessment of our resource management, we evaluated prospectively collected data on the Apache II scores on the day of admission, the incidence of ICU-specific interventions, length of stay in ICU, and outcomes. ICU-specific interventions were not initially required in 36% of admissions and these patients had a low risk (1.1%) of eventually requiring ICU-specific interventions. In comparison with patients requiring ICU-specific interventions, they had lower Apache II scores (10.2 vs 13.1), shorter ICU stays (medians of one vs two days), lower ICU mortality (0 vs 8.2%), P < 0.05, but hospital mortality was not different (7.4 vs 15.3%). This audit has prompted re-organisation of our intensive care services, so that patients not requiring ICU-specific interventions will be managed in an intermediate care area with nurse.patient ratios of 1:3 or 4, in comparison with 1:1 or 2 ratios in the intensive care area.  相似文献   
74.
Research Objectives: To develop population-based estimates of estrogen replacement therapy use rates in 1995 among women over age 65 living in the community; to estimate the impact of socioeconomic and health characteristics on estrogen use. Method: Estimates are based on a large, nationally representative sample of Medicare beneficiaries; detailed self-report data were merged with Medicare claims. Results: Overall, 13.1% of women reported use of estrogen replacement therapy in 1995. Estrogen users were more likely to be white, age 65–74, with private insurance, high income, history of osteoporosis and heart problems, no history of breast cancer, and a patient of gynecologists. Conclusions: Estrogen use was substantially lower among the socioeconomically disadvantaged, controlling for medical history variables, suggesting considerable inequity in access to estrogen replacement therapy treatment.  相似文献   
75.
A quasi-experimental design was used to assess the efficacy of a leisure education-based later-life planning model for 10 older adults with mental retardation. Prior to the initiation of the planning process, they were interviewed and completed three standardized scales designed to assess life and leisure satisfaction and leisure constraints. A comparison group completed these scales but did not participate in the planning process. At the completion of the study, both groups completed the same scales. Results demonstrated that the planning-process group had significantly higher life and leisure satisfaction at the end of the study. Many participants also made changes to their lifestyles consistent with plans made during the study. Results suggest that a later-life planning process may contribute to the quality of life of older adults with mental retardation.  相似文献   
76.
Primary Care Groups (PCGs) represent a natural evolution of the various models--total purchasing, multifunds and locality commissioning--embraced by the term "primary care commissioning". They will involve large numbers of different professionals working together to commission improved health care for their populations. The total purchasing pilots (TPPs) were the subjects of an extensive evaluation which has highlighted the significance of developing and improving relationships between the key players as a prerequisite for the successful implementation of their strategy. Management arrangements were central to this success. Similar considerations will be of crucial importance for the PCGs which are considerably larger and more complex organisations than the TPPs.  相似文献   
77.
The introduction of total purchasing pilots (TPPs) into the National Health Service (NHS) gave general practitioners (GPs) significant new opportunities to take responsibility for the development of community and continuing care (CCC) services. Based on five case studies of TPPs involved in developing CCC this paper asks three questions: (1) to what extent were the TPP’s involvement in CCC informed by an awareness of CCC policy?; (2) were TPPs involved in joint commissioning to develop integrated purchasing or provision which was informed by population based needs assessment?; (3) were TPPs seeking to involve users, carers and voluntary agencies in their plans? The findings indicate that TPPs showed little awareness of national or local policy for CCC, although their project initiatives did address some of the policy issues (in particular a recognition of the need for joint working at the practice level). At the time of fieldwork, four of the case study TPPs had begun to investigate the potential for integrated purchasing, and three of them had relatively sophisticated models of both horizontally and vertically integrated provision of care. However, the TPPs developments were not based on systematic population based needs assessment. The paper concludes that there is potential for the primary care led groups proposed in the recent white papers in England, Scotland and Wales to improve integration of care both horizontally and vertically. However, they may need policy guidance and push to: encourage them to put CCC high on their agenda for action; to work with people with expertise in population based, prevention focused, needs assessment; and to find innovative ways to include users, carers and voluntary agencies. Incentives or levers (such as control over budgets) may be needed to promote joint working between staff in different agencies.  相似文献   
78.
Purpose. The described structure pharmacokinetic pharmacodynamic relationships (SPPR) study explored the utilization of tetramethylcyclopropane analogues of valpromide (VPD), or tetra-methylcyclopropane carboxamide derivatives of valproic acid (VPA) as new antiepileptics. Methods. The study was carried out by investigating the pharmacokinetics in dogs and pharmacodynamics (anticonvulsant activity and neurotoxicity) of the following three cyclopropane analogues of VPD: 2,2,3,3-tetramethylcyclopropane carboxamide (TMCD), N-methyl TMCD (M-TMCD) and N-[(2,2,3,3-tetramethylcyclopropyl)carbonyl]-glycinamide (TMC-GLD). Results. The three investigated compounds showed a good anticonvulsant profile in mice and rats due to the fact that they were metabolically stable VPD analogues which were not biotransformed to their non-active acid, 2,2,3,3-tetramethylcyclopropane carboxylic acid (TMCA). M-TMCD was metabolized to TMCD and TMC-GLD underwent partial biotransformation to its glycine analogue N-[(2,2,3,3-tetramethylcyclopropyl)carbonyl]-glycine (TMC-GLN). Unlike TMC-GLN, the above mentioned amides had low clearance and a relatively long half life. Conclusions. In contrast to VPD which is biotransformed to VPA, the aforementioned cyclopropane derivatives were found to be stable to amide-acid biotransformation. TMCD and M-TMCD show that cyclic analogues of VPD, like its aliphatic isomers, must have either two substitutions at the position to the carbonyl, such as in the case of TMCD, or a substitution in the and in the positions like in the VPD isomer, valnoctamide (VCD). This paper discusses the antiepileptic potential of tetramethylcyclopropane analogues of VPD which are in animal models more potent than VPA and may be non-teratogenic and non-hepatotoxic.  相似文献   
79.
PURPOSE: Tumor hypoxia confers chemotherapy resistance. Tirapazamine is a cytotoxin that selectively targets hypoxic cells and has supra-additive toxicity with platinums and taxanes in preclinical studies. We conducted a Phase I study of tirapazamine, carboplatin, and paclitaxel and assessed potential plasma markers of hypoxia as surrogates for response. EXPERIMENTAL DESIGN: Forty-two patients with advanced solid tumors were treated at four dose levels; parallel dose escalations were carried out in chemotherapy-naive and previously treated subjects. Pre and post-therapy plasma levels of the hypoxia-induced proteins plasminogen activator inhibitor-1 and vascular endothelial growth factor were measured. RESULTS: Three of four chemotherapy-na?ve patients developed dose-limiting toxicities at dose level 4 (grade 3 stomatitis/infection, grade 3 emesis, and grade 4 febrile neutropenia). Four of seven previously treated patients developed dose-limiting toxicities at dose level 3, including one death [grade 3 myalgia, grade 3 infection/grade 4 neutropenia, grade 3 infection/grade 4 neutropenia, and grade 5 infection (death)/grade 4 neutropenia]. Of 38 patients assessable for response, 3 had a complete response, 1 a partial response, 1 an unconfirmed partial response, and 23 had stable disease in at least one evaluation; 10 quickly progressed. One complete responder had normalization of vascular endothelial growth factor and plasminogen activator inhibitor-1 levels. CONCLUSION: Dose levels 3 (carboplatin AUC of 6, 225 mg/m(2) paclitaxel, and 330 mg/m(2) tirapazamine) and 2 (carboplatin AUC 6, 225 mg/m(2) paclitaxel, and 260 mg/m(2) tirapazamine) are the maximum tolerated doses for chemotherapy naive and patients treated previously, respectively. Dose level 3 is the experimental arm of a Phase III Southwest Oncology Group trial (S0003) in advanced non-small cell lung cancer. Potential markers of tumor hypoxia may be useful correlates in studies of hypoxic cytotoxins and are being prospectively investigated in S0003.  相似文献   
80.
The purpose is to determine breast cancer risk factors and correlates of mammographic parenchymal patterns among Alaska Native women. A retrospective review was performed of mammograms and mammogram records among 528 sequential screening mammogram examinations performed in Anchorage, Alaska. Mammogram density was classified by American College of Radiology (Breast Imaging Reporting and Data System) density patterns 1-4 (fat-->dense) and by percent density. Clinical data, including risk factors, ethnic group (Indian, Aleut, or Eskimo), and smoking status were obtained. Results were analyzed by univariate and multivariate analyses. Of 528 women, 164 were Indian, 155 were Aleut, and 209 were Eskimo. Mean age at first birth was lower and parity higher compared with published data in white women. Breast cancer risk factors were similar across ethnic groups. In multivariate analysis, patient age, parity, hormone replacement therapy, hysterectomy, and history of biopsy were associated, and smoking was not associated with density scores. Aleut and Indian women were less likely to have high-density mammograms than were Eskimo women (P = 0.0448). No significant differences were found between ethnic group for conventional breast cancer risk factors. Mammogram density was associated with age at screening, parity, hormone replacement therapy, hysterectomy, history of biopsy, and ethnicity but not smoking status. Eskimo women had higher mammogram density than Aleuts or Indians.  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