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   2302篇
  免费   148篇
  国内免费   15篇
耳鼻咽喉   10篇
儿科学   97篇
妇产科学   15篇
基础医学   320篇
口腔科学   220篇
临床医学   226篇
内科学   362篇
皮肤病学   24篇
神经病学   217篇
特种医学   86篇
外科学   478篇
综合类   17篇
一般理论   3篇
预防医学   89篇
眼科学   45篇
药学   139篇
中国医学   2篇
肿瘤学   115篇
  2023年   18篇
  2022年   15篇
  2021年   24篇
  2020年   27篇
  2019年   30篇
  2018年   42篇
  2017年   36篇
  2016年   48篇
  2015年   46篇
  2014年   73篇
  2013年   108篇
  2012年   146篇
  2011年   152篇
  2010年   93篇
  2009年   116篇
  2008年   170篇
  2007年   164篇
  2006年   151篇
  2005年   151篇
  2004年   148篇
  2003年   137篇
  2002年   125篇
  2001年   21篇
  2000年   19篇
  1999年   24篇
  1998年   25篇
  1997年   24篇
  1996年   21篇
  1995年   23篇
  1994年   16篇
  1993年   16篇
  1992年   17篇
  1991年   23篇
  1989年   18篇
  1988年   18篇
  1987年   10篇
  1986年   8篇
  1985年   14篇
  1984年   13篇
  1982年   8篇
  1981年   10篇
  1980年   6篇
  1979年   10篇
  1978年   7篇
  1976年   7篇
  1975年   10篇
  1974年   8篇
  1973年   8篇
  1969年   7篇
  1967年   6篇
排序方式: 共有2465条查询结果,搜索用时 15 毫秒
11.
Long-term administration of high doses of xylitol and other polyols in rats has been associated with an increase in adrenal medullary hyperplasia and neoplasia. In order to exclude age-related factors and to differentiate between unspecific stress reactions and direct effects of the compound administered, a model was developed for quantifying early adrenomedullary responses. Male SD rats were fed xylitol (10% or 20% in the diet) for 2 and 8 weeks, and early biochemical changes were correlated with a stereological analysis of the adrenal medulla. At first, the in vivo rate of catecholamine (CA) biosynthesis was slightly decreased (at 2 weeks). This was followed by an increase in dopamine--hydroxylase (DBH) activity (at 8 weeks). By that time, the total chromaffin cell volume had increased and the number of chromaffin cells per reference volume had decreased in a dose-dependent way. The total number of chromaffin cells per adrenal gland showed a distinct tendency towards an increase. Adrenal epinephrine and norepinephrine contents were not altered, and both tyrosine hydroxylase and phenylethanolamine-N-methyltransferase activities remained unchanged. These data suggest that continued xylitol administration evoked an inhibitory effect on CA synthesis that, together with stimulation of the adrenal medulla brought about by the compound, resulted in compensatory medullary hypertrophy and hyperplasia.  相似文献   
12.
13.
Zusammenfassung Der standardisierte Fragebogen zur Erfassung muskuloskeletaler Beschwerden des japanischen Komitees zum Studium arbeitsbedingter Gesundheitsstörungen im Hals-Arm-Gebiet wurde auf Deutsch übertragen und seine Reliabilität und Validität überprüft. Im Fragebogen wird anhand eines Körperschemas nach der Häufigkeit (nie/selten, gelegentlich, fast täglich) von Beschwerden (Schmerzen, Steifigkeit, Müdigkeit) in 12 Körperregionen gefragt. Der Fragebogen wurde gleichzeitig mit ärztlichen Palpationsuntersuchungen bei 644 Personen aus zwölf Berufsgruppen im Dienstleistungssektor eingesetzt. Auf Grund einer Faktoranalyse der Fragebogenresultate kann festgestellt werden, dass Beschwerden regional getrennt (nämlich im Nacken-Schultergebiet, dem Rücken und je der rechten und linken oberen Extremität) auftreten und für diese Regionen die Symptome zu Indizes zusammengefasst werden können. Diese Indizes sind reliabel (Cronbach 0.8). Mit zunehmenden Indexwerten nehmen schmerzhafte Palpationsbefunde stetig zu. Beschwerden korrelieren mit vermehrtem Medikamentenkonsum und Arztkonsultationen. Der Fragebogen stellt folglich ein valides Untersuchungsinstrument für muskuloskeletale Beschwerden am Arbeitsplatz dar.
Summary The standardized illustrated questionnaire on musculoskeletal disorders of the Japanese Committee on Occupational Cervico-brachial Disorders was translated into German. This questionnaire, composed of 37 items about the occurrence (never/seldom, occasionally, almost daily) of symptoms (pain, stiffness, fatique) in twelve body regions, was used together with medical examinations (pressure points), and further information was gathered on the consumption of analgetics and medical visits prompted by musculoskeletal symptoms. The questionnaire's reliability and validity were tested in 644 persons from twelve occupational groups within the service sector. Factoranalyses showed that symptoms can be grouped into four distinct regions of occurrence: neck/shoulder/area, back/low back, and both left and right upper extremities. Indices based on these regions are consistent (Cronbach 0.8). Palpation findings steadily increase with increasing index values. The consumption of medicaments and medical visits positively correlate with the indices. Consequently the questionnaire is judged to be a valid instrument for studying musculoskeletal disorders at the workplace.

Résumé Le questionnaire illustré et standardisé sur les symptômes musculaires et osseux du comité japonais sur la cervico-brachialgie professionelle a été traduit en allemand et sa reliabilité et validité ont été testées. Le questionnaire est composé de 37 variables sur la fréquence (jamais/rarement, par occasion, presque toujours) des symptômes (douleur, raideur, fatigue) dans douze régions du corps. Il était distribué simultanément aux examens médicaux parmi 644 personnes de douze groupes d'employés dans le secteur de service. D'autres informations concernent la fréquence de la consommation des analgésiques et des visites médicales pour des douleurs musculaires. Une analyse factorielle a montré que les symptômes peuvent être groupés en quatre régions du corps: nuque/épaules, dos et les extrémités supérieurs. Les indices sur ces régions sont consistant (Cronbach 0.8). Les douleurs provoquées par la palpation augmentent avec la valeur de l'index. La consommation des analgésiques et les consultations sont correlées avec les indices. Par conséquent, le questionnaire illustré est un instrument valable pour étudier les problèmes musculaires sur les lieux de travail.
  相似文献   
14.
PURPOSE: CEACAM6, CEACAM1, and human carcinoembryonic antigen (CEA) are coexpressed in normal colorectal epithelia, but show deregulated expression in colorectal cancers (CRC). Upregulation of CEACAM6 expression in hyperplastic polyps and early adenomas represents one of the earliest observable molecular events leading to colorectal tumors. The aim of our study was to evaluate the prognostic relevance of CEACAM6, CEACAM1, and CEA tissue expression in patients with CRC. PATIENTS AND METHODS: Immunohistochemical analysis was carried out on tissue microarrays from 243 paraffin-embedded biopsies from a randomized controlled clinical trial (Swiss Group for Clinical Cancer Research [SAKK] 40/81) of adjuvant fluorouracil-based chemotherapy with CEACAM-specific monoclonal antibodies. The median follow-up was 8 years. Overall survival (OS) and disease-free survival (DFS) were calculated using Kaplan-Meier estimates and hazard ratios (HRs) estimated using Cox proportional hazards models. RESULTS: Tissue expression of CEACAM6, CEACAM1, and CEA was enhanced in 55%, 58%, and 94% of patients, respectively. Multivariate Cox analysis including sex, age, tumor site, stage, differentiation grade, treatment, and nodal status as covariates showed that CEACAM6 overexpression independently predicted poor OS (HR, 1.86; P =.0100) and DFS (HR, 2.00; P =.0028), whereas CEACAM1 or CEA were not significantly related to these outcomes. The data did not provide evidence for or against the hypothesis that the CEACAM6 effect on survival differs according to treatment. CONCLUSION: Expression of the cell adhesion molecule CEACAM6 in CRC is an independent prognostic factor allowing subdivision of patients into low- and high-risk groups. Whether CEACAM6 or CEA and CEACAM1 might be useful as predictive markers of chemotherapy benefit remains unclear.  相似文献   
15.
OBJECTIVE: To describe a nosocomial norovirus outbreak, its management, and its financial impact on hospital resources. DESIGN: A matched case-control study and microbiological investigation. METHODS: We compared 16 patients with norovirus infection with control-patients matched by age, gender, disease category, and length of stay. Bed occupancy-days during the peak incidence period of the outbreak were compared with the corresponding periods in 2001 and 2002. Expenses due to increased workload were calculated based on a measuring system that records time spent for nursing care per patient per day. RESULTS: The attack rates were 13.9% among patients and 29.5% among healthcare workers. The median number of occupied beds was significantly lower due to bed closure during the peak incidence in 2003 (29) compared with the median number of occupied beds in 2001 and 2002 combined (42.5). Based on this difference and a daily charge of 562.50 dollars per patient, we calculated a revenue loss of 37,968 dollars. Additional expenses totaled 10,300 dollars for increased nursing care. Extra costs for microbiological diagnosis totaled 2707 dollars. Lost productivity costs due to healthcare workers on sick leave totaled 12,807 dollars. The expenses for work by the infection control team totaled 1408 dollars. The financial impact of this outbreak on hospital resources comprising loss of revenue and extra costs for microbiological diagnosis but without lost productivity costs, increased nursing care, and expenses for the infection control team totaled 40,675 dollars. CONCLUSIONS: Nosocomial norovirus outbreaks result in significant loss of revenue and increased use of resources. Bed closures had a greater impact on hospital resources than increased need for nursing care  相似文献   
16.
17.
This study aimed at examining the effects of nine weeks of sand-based plyometric-jump training (PJT) combined with endurance running on either outdoor or treadmill surface on measures of physical fitness. Male participants (age, 20.1 ± 1.7 years) were randomly assigned to a sand-based PJT combined with endurance running on outdoor surface (OT, n = 25) or treadmill surface (TT, n = 25). The endurance running intervention comprised a mixed training method, i.e., long slow distance, tempo, and interval running drills. A control group was additionally included in this study (CG, n = 25). Participants in CG followed their regular physical activity as OT and TT but did not receive any specific intervention. Individuals were assessed for their 50-m linear sprint time, standing long jump (SLJ) distance, cardiorespiratory fitness (i.e., Cooper test), forced vital capacity (FVC), calf girth, and resting heart rate (RHR). A three (groups: OT, TT, CG) by two (time: pre, post) ANOVA for repeated measures was used to analyze the exercise-specific effects. In case of significant group-by-time interactions, Bonferroni adjusted paired (within-group) and independent (between-group comparisons at post) t-tests were used for post-hoc analyses. Significant group-by-time interactions were found for all dependent variables (p < 0.001 – 0.002, ɳp2 = 0.16 – 0.78). Group-specific post-hoc tests showed improvements for all variables after OT (p < 0.001, Hedges’g effect size [g] = 0.05 – 1.94) and TT (p < 0.001, g = 0.04 – 2.73), but not in the CG (p = 0.058 – 1.000, g = 0.00 – 0.34). Compared to CG, OT showed larger SLJ (p = 0.001), cardiorespiratory fitness (p = 0.004), FVC (p = 0.008), and RHR (p < 0.001) improvements. TT showed larger improvements in SLJ (p = 0.036), cardiorespiratory fitness (p < 0.001), and RHR (p < 0.001) compared with CG. Compared to OT, TT showed larger improvements for SLJ (p = 0.018). In conclusion, sand-based PJT combined with either OT or TT similarly improved most measures of physical fitness, with greater SLJ improvement after TT. Coaches may use both concurrent exercise regimes based on preferences and logistical constrains (e.g., weather; access to treadmill equipment). Key points
  • Concurrent training in the form of sand-based plyometric-jump training and endurance running exercise can enhance physical fitness in young individuals;
  • Compared to treadmill running, rating of perceived exertion was higher in outdoor running sessions;
  • Sand-based plyometric-jump training may induce greater standing long jump performance when combined with endurance running on treadmill surface as compared to outdoor surface.
Key words: Muscle strength, musculoskeletal and neural physiological phenomena, movement, resistance training, high-intensity interval training, exercise  相似文献   
18.
19.
ObjectiveA recent study suggested that the anti-inflammatory effect of immunonutrition starts after only two d. We therefore investigated the effect of an immunoenriched oral diet administered for three d preoperatively.MethodsIn this prospective, randomized, double-blind, placebo-controlled study, well-nourished patients (Nutrition Risk Screening 2002 <3) with gastrointestinal cancer who were scheduled for major elective abdominal cancer surgery were randomly assigned to either 750 mL of an immunoenriched formula (IEF group) or 750 mL of an isocaloric, isonitrogenous placebo diet (Con group) for 3 consecutive d preoperatively.ResultsA total of 108 patients (IEF group: n = 55; Con group: n = 53) were randomized. The two groups were comparable for all baseline and surgical characteristics. The overall mortality was 2.8% and not significantly different between the two groups (IEF group: 3.6% vs. Con group: 1.9%, P = 1.00). Intention-to-treat analysis showed no difference for the incidence of postoperative overall (IEF group: 29% vs. Con group: 30%; P = 1.00) and infectious (IEF group: 15% vs. Con group: 17%; P = 0.79) complications. Length of hospital stay was 12 ± 4.9 d in the IEF group and 11.6 ± 5.3 d in the Con group (P = 0.68).ConclusionsPreoperative oral supplementation with an immunoenriched diet for 3 d preoperatively did not improve postoperative outcome compared with the placebo in well-nourished patients with elective gastrointestinal cancer surgery.  相似文献   
20.
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