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   31348篇
  免费   2610篇
  国内免费   687篇
耳鼻咽喉   238篇
儿科学   1280篇
妇产科学   778篇
基础医学   1766篇
口腔科学   908篇
临床医学   3642篇
内科学   6502篇
皮肤病学   405篇
神经病学   1328篇
特种医学   786篇
外国民族医学   1篇
外科学   2936篇
综合类   4207篇
现状与发展   1篇
预防医学   4839篇
眼科学   334篇
药学   2258篇
  36篇
中国医学   1145篇
肿瘤学   1255篇
  2024年   149篇
  2023年   886篇
  2022年   1709篇
  2021年   2187篇
  2020年   1871篇
  2019年   1716篇
  2018年   1698篇
  2017年   1262篇
  2016年   1169篇
  2015年   1104篇
  2014年   2324篇
  2013年   2183篇
  2012年   1826篇
  2011年   1975篇
  2010年   1594篇
  2009年   1520篇
  2008年   1402篇
  2007年   1436篇
  2006年   1031篇
  2005年   938篇
  2004年   726篇
  2003年   609篇
  2002年   419篇
  2001年   399篇
  2000年   277篇
  1999年   269篇
  1998年   213篇
  1997年   202篇
  1996年   173篇
  1995年   169篇
  1994年   158篇
  1993年   122篇
  1992年   133篇
  1991年   116篇
  1990年   89篇
  1989年   80篇
  1988年   55篇
  1987年   63篇
  1986年   47篇
  1985年   58篇
  1984年   57篇
  1983年   42篇
  1982年   39篇
  1981年   33篇
  1980年   28篇
  1979年   17篇
  1978年   22篇
  1977年   14篇
  1976年   15篇
  1975年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
BACKGROUND: Color Doppler ultrasonography of intrarenal arterial resistance index (RI), performed early after kidney transplant, has proven to reliably predict short-term allograft function. The aim of this study was to assess whether it could also predict long-term renal function. METHODS: We retrospectively analysed 76 kidney transplant patients who underwent RI assessment within 1 month after the transplant, subdivided into two groups according to RI values, lower (group A) or higher (group B) than its median value (0.635). RESULTS: Compared with group A subjects, the patients of group B were older at the time of transplant (42 +/- 9 vs 35 +/- 8 years; P = 0.001), the donor age was also older (41 +/- 16 vs 33 +/- 13 years; P = 0.02) and had a slightly higher proteinuria (0.54 +/- 0.5 vs 0.32 +/- 0.2 g/24 h; P = 0.02). Serum creatinine, ciclosporin or tacrolimus trough level, arterial blood pressure, number of human leukocyte antigen (HLA) mismatches, anti-hypertensive medications and incidence of delayed graft function were not significantly different between the two groups. By univariate analysis, RI turned out to directly correlate with the recipient age, donor age and daily proteinuria (P = 0.007, P = 0.0007 and P = 0.02, respectively). Multivariate analysis showed that only donor and recipient age maintained their independent predictive value on RI. Kaplan-Meier analysis, considering a serum creatinine increase >50% as the endpoint of the study, showed a statistically significant different graft survival in the two groups (log-rank test = 5.489; P = 0.01). The univariate relative risk of deterioration of graft function among patients with higher RI was 3.77. Proteinuria and recipient age increased the risk as well. CONCLUSIONS: Our data seem to suggest that early determination of RI can help predict long-term graft function in kidney transplant recipients.  相似文献   
52.
目的研究寡克隆区带(OCB)和IgG指数在多发性硬化(MS)中的临床意义。方法收集MS患者54例和其他神经系统疾病(OND)患者271例,包括中枢神经系统感染性疾病62例及非感染性疾病209例的脑脊液和血清标本,分别进行OCB检测(聚丙烯酰胺凝胶电泳)和IgG指数的计算(免疫火箭电泳法)。结果MS组OCB阳性率为35.2%;OND组为8.9%,其中感染组为24.2%,非感染组为4.5%。MS与OND组整体比较OCB阳性率有显著性差异(P〈0.05),但与感染组相比无显著性差异(P〉0.05)。MS组IgG指数阳性率为83.3%,OND组为78.2%(P〉0.05)。结论OCB对MS有一定的辅助诊断价值,但需除外CNS感染性疾病。IgG指数阳性可作为参考。  相似文献   
53.
周军  王健  罗林丽  石恒林 《现代预防医学》2007,34(20):3977-3978,3982
[目的]通过监测老年病人麻醉诱导时脑电双频指数(BIS)的变化,探讨既能维持足够麻醉深度又能避免严重低血压的异丙酚诱导用量。[方法]40例ASA II~I级的老年病人(65~85岁),随机分成两组。A组静脉注射异丙酚1.6 mg/kg;B组静脉注射异丙酚,其用量是使BIS下降到40~50时的用量。两组均复合维库溴铵0.1 mg/kg和瑞芬太尼1ug/kg诱导后行气管插管分别记录基础值、插管前、插管后1 min、5 min和10 min时的收缩压(SBP)、舒张压(DBP)、平均动脉压(MAP)、心率(HR),同时记录诱导异丙酚用药量和BIS的变化。[结果]A组异丙酚诱导用药量(99.7±18.05)mg,平均(1.64±0.7)mg/kg,B组(82.9±12.5)mg,平均(1.35±0.5)mg/kg,差异有统计学意义(P﹤0.05)。A组血压(BP)和BIS比B组明显降低。[结论]老年病人异丙酚麻醉诱导的合适用量为(1.35±0.5)mg/kg;既能维持老年人足够的麻醉深度又能避免严重低血压的发生。  相似文献   
54.
BACKGROUND: The reasons for mis-reporting food consumption warrant investigation. OBJECTIVE: To document intention to mis-report food consumption and its associations with psychological measures in women. DESIGN: A total of 184 female volunteers aged 18-65 years, comprising 50 seeking help in primary care to lose weight with a body mass index (BMI) >/=30 kg m(-2) (obese-clinical group) and 134 nurses (nonclinical groups) (BMI <25 kg m(-2), n = 52; BMI 25-29.9 kg m(-2), n = 45; BMI >/=30 kg m(-2), n = 37) were studied. A questionnaire was administered containing three psychological tests (self-esteem, psychological well-being and Stunkard's three-factor eating questionnaire) and new items to address food intake mis-reporting. RESULTS: Overall, 68% of participants declared an inclination to mis-report (64% nonclinical, 78% clinical). Inclination to under-report was 29, 33 and 51% in the three nonclinical groups; and 46% among the obese clinical patients. Among the same groups, inclination to over-report were 39, 29, 11 and 32%. After adjusting for social deprivation and BMI, women inclined to mis-report had higher hunger (P = 0.008) and disinhibition (P = 0.005) scores than those intending to report accurately. These variables were associated with current dieting, frequency of dieting, self-reported bingeing and dissatisfaction with body weight. CONCLUSIONS: These findings indicate that intentional under-reporting and over-reporting of food consumption are common in women of all BMI categories and are associated with eating behaviour. Current dieting, frequency of dieting in the past, self-reported bingeing and dissatisfaction with body weight seem to mediate this relationship.  相似文献   
55.
PURPOSE: Evaluate the effectiveness of body mass index (BMI) tables placed in exam rooms as an intervention to encourage providers to calculate and record BMI scores in patients' medical records. DESIGN: In a prospective cohort design, medical record data for 276 adult patients at a federally funded community health center in New England were examined from August 2000 to August 2002 following the intervention. METHODS: Prominent, multicolored, laminated BMI tables were posted in the exam rooms of one of the study site's three primary health care teams. Medical record data collected included documentation of BMI calculation in medical records, documentation of an obesity diagnosis, and inclusion of heights and current weights. Frequency distributions were calculated; chi-square tests were used to identify associations. FINDINGS: In contrast to the comparison teams, patients on the intervention team were more likely to have BMI recorded in the medical record. A statistically significant increase in the diagnosis of obesity was observed throughout the health center after the intervention. CONCLUSIONS: Posting BMI tables in exam rooms contributed to increased BMI documentation in patients' medical records.  相似文献   
56.
目的 观察2-乙氧基乙醇(2-Ethoxythanol,EE)急性染毒对SD大鼠血清和睾丸某些抗氧化指标的变化,探讨EE致睾丸损伤的可能机制。方法 选择健康雄性SD大鼠,体重180-220g。随机分为对照组、EE800、1600和3200mg/kg组4组,每组24只。采取一次性灌胃染毒。于灌胃后12、24、48和72h,将各组动物随机处死6只,留取动物血液、睾丸,制备血清和睾丸匀浆,测定血清和睾丸匀浆脂质过氧化物(LPO)水平、超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性,以及血清铜蓝蛋白(CP)活性。结果 与对照组比较,各染毒组睾/体比明显下降(P<0.05),睾丸匀浆LPO水平和血清CP活性增高。染毒12、24h,血清CAT、睾丸匀浆CAT和SOD活性增高,而染毒48、72h后,血清CAT、睾丸匀浆CAT和SOD活性显著降低(P<0.05)。EE各染毒组血清LPO水平和SOD活性变化不明显。结论 推测EE毒作用的靶器官可能是睾丸,睾丸抗氧化功能的改变是EE致睾丸毒性的可能机制。  相似文献   
57.
Physical inactivity, excess adiposity and premature mortality   总被引:5,自引:0,他引:5  
The purpose of this report is to review the evidence that physical inactivity and excess adiposity are related to an increased risk of all‐cause mortality, and to better identify the independent contributions of each to all‐cause mortality rates. A variance‐based method of meta‐analysis was used to summarize the relationships from available studies. The summary relative risk of all‐cause mortality for physical activity from the 55 analyses (31 studies) that included an index of adiposity as a covariate was 0.80 [95% confidence interval (CI) 0.78–0.82], whereas it was 0.82 [95% CI 0.80–0.84] for the 44 analyses (26 studies) that did not include an index of adiposity. Thus, physically active individuals have a lower risk of mortality by comparison to physically inactive peers, independent of level of adiposity. The summary relative risk of all‐cause mortality for an elevated body mass index (BMI) from the 25 analyses (13 studies) that included physical activity as a covariate was 1.23 [95% CI 1.18–1.29], and it was 1.24 [95% CI 1.21–1.28] for the 81 analyses (36 studies) that did not include physical activity as a covariate. Studies that used a measure of adiposity other than the BMI show similar relationships with mortality, and stratified analyses indicate that both physical inactivity and adiposity are important determinants of mortality risk.  相似文献   
58.
 In order to determine the dynamics of hematopoietic cell turnover, proliferative activity and incidence of apoptosis (programmed cell death) were evaluated in bone marrow trephine biopsies. Selection of patients (20 in each group) included in addition to a control group, idiopathic thrombocytopenia (ITP), reactive thrombocytosis (TH), secondary polycythemia-smokers' polyglobuly (PG), primary (essential-hemorrhagic) thrombocythemia (PTH), polycythemia vera (PV), and finally acute myeloid leukemia (AML). Apoptosis was demonstrated by the in situ end-labeling technique (ISEL) and proliferative activity by applying the monoclonal antibody PC10 raised against proliferating cell nuclear antigen (PCNA). To assess dynamic features of hematopoiesis, an index was calculated consisting of the ratio between PCNA-positive nuclei and the apoptotic cell fraction. This factor was termed the hematopoietic turnover index (HTI). Morphometric analysis revealed that the HTI was significantly increased in AML and PV. According to cell culture studies both disorders are characterized by either a prevalent proliferation of the myeloid or erythroid cell mass. On the other hand, PG, PTH, and TH showed no relevant enhancement of this index in comparison to the control specimen. In vitro experiment results are in keeping with the finding that PG and PTH are not associated with a significant expansion of the erythroid lineage (CFU-E). Similar to ITP and TH, in PTH megakaryocyte proliferation (CFU-MEG) is the predominant feature of cell turnover. Differences between PTH and TH are in line with the reduced in vitro formation of CFU-MEG in the latter disorder. In conclusion, our in situ study on turnover rates of the bone marrow in various neoplastic and reactive lesions extends previous experimental data on hematopoietic cell kinetics. Received: 10 March 1997 / Accepted: 18 May 1997  相似文献   
59.
Abstract From August to October 1991, the periodontal status of 1001 Yemenis representing the age groups 12-14, 15-19, 20-24 and 35-44 years was recorded and evaluated with preference to the CPITN, the calculus index and clinical attachment levels. The impact of chewing khat, the leaves of a cultivated, alkaloid shrub, and of using the traditional miswak chewing stick for oral hygiene purposes were investigated. The results show that 6.9% of the juvenile probands (15-19 years) had healthy periodontal tissue (CPITN 0). whereas bleeding on probing and calculus (CPITN 1+2) were registered in 86.2%. In the 35-44 year age group. 1.7% were periodontally healthy, whereas 84.5% displayed plaque retention or shallow pocketing (CPITN 2-3) and 12.5% deep pocketing (CPITN 4). The treatment needs in all age groups are confined primarily to calculus removal and instruction in oral hygiene. The clinical attachment level and the calculus index revealed age-related attachment loss and calculus formation, primarily among male probands. The higher khat consumption among the male population is reflected in its detrimental effect on the periodontal tissue, especially among younger probands. Oral hygiene aids have also an influence on periodontal status, with a toothbrush proving more efficient than the miswak. WHO efforts directed towards prophylactic programs need to be intensified but can be staffed by dental hygienists.  相似文献   
60.
Objective To analyze the relations between obstructive sleep apnea and bradyarrhythmia.Methods From 1999 to 2005,203 patients who came from Bering Tongren Hospital and Fuwai Hospital were found to have sleep apnea in an ambulatory study. A Hoher electrecardiogram was recorded for 24 hours within 2 weeks after patients were diagnosed as obstructive sleep apnem Results Nocturnal episodes of bradyarrhythmia were identified in 12(5.9%)of 203 patients.Body mass index and respiratory disturbance index in patients with bradyarrhythmia(n=12)were higher than those in patientswithour bradyarrhymia(n=191)(34±5 735.24±6 and 63±15 vs.25±5,respectively,both P<0.01).There was a significant difference in end-apneic oxygen saturation in apnea/hypopnea episodes with and without bradyarrhythmia(63%±15% vs.75%±11%,P<0.05).A linear relation between end-apneic oxygen saturation and number of sinus arrests and heart blocks was not found.Conclusions Patients with apnea-associated bradyarrhythmia have higher body mflgB index and higher respiratory disturbance index than patients without bradyarrhythmi&Bradyarrhythmia occurres independently from decrease in oxygen saturation.  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