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   660篇
  免费   68篇
  国内免费   1篇
耳鼻咽喉   5篇
儿科学   46篇
妇产科学   4篇
基础医学   70篇
口腔科学   29篇
临床医学   147篇
内科学   83篇
皮肤病学   9篇
神经病学   58篇
特种医学   14篇
外科学   68篇
综合类   3篇
一般理论   1篇
预防医学   77篇
眼科学   5篇
药学   60篇
肿瘤学   50篇
  2023年   2篇
  2022年   7篇
  2021年   13篇
  2020年   13篇
  2019年   24篇
  2018年   20篇
  2017年   22篇
  2016年   21篇
  2015年   20篇
  2014年   25篇
  2013年   43篇
  2012年   38篇
  2011年   35篇
  2010年   25篇
  2009年   28篇
  2008年   49篇
  2007年   48篇
  2006年   42篇
  2005年   54篇
  2004年   43篇
  2003年   40篇
  2002年   36篇
  2001年   7篇
  2000年   2篇
  1999年   4篇
  1998年   5篇
  1997年   7篇
  1996年   6篇
  1995年   4篇
  1994年   6篇
  1993年   5篇
  1992年   6篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   3篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1971年   3篇
  1970年   2篇
  1969年   1篇
排序方式: 共有729条查询结果,搜索用时 15 毫秒
91.
Dental caries and mutans streptococci in relation to plasma ascorbic acid   总被引:1,自引:0,他引:1  
Ascorbic acid (AA) affects in vitro growth of bacteria and may also act in vivo to decrease caries activity. The aim of this study was to evaluate the possible association of AA level in plasma with number of caries lesions, relative numbers of some species of oral cariogenic flora, and rate of salivary secretion. The caries status and some bacteriologic variables of dentulous adult subjects with a low level of AA in the plasma (≤25 μmol/1; n =75) were compared with those of controls (plasma level ≥50 μmol/1; n =75) matched for age, sex, and number of teeth. For each subject, site-specific recordings of the presence or absence of plaque, dental caries, fillings, and erosions were recorded clinically by the same dentist in a double-blind system. The amounts of visible plaque and numbers of decayed tooth surfaces were significantly higher in the low AA group than in the controls. No between-group differences were found in the number of fillings and the amount of oral bacterial growth. The frequencies of consumption of vegetables, berries, and other fruit were significantly lower in the low AA group than in the controls.  相似文献   
92.
The fms-like tyrosine kinase 4 (FLT4) complementary DNA was cloned from a human HEL erythroleukemia cell library by polymerase chain reaction-amplification. We previously reported a partial sequence of FLT4 and showed that the FLT4 gene maps to chromosomal region 5q33-qter (O. Aprelikova, K. Pajusola, J. Partanen, E. Armstrong, R. Alitalo, S. Bailey, J. McMahon, J. Wasmuth, K. Huebner, and K. Alitalo, Cancer Res., 52: 746-748, 1992). Here we present the full-length sequence of the predicted FLT4 protein. The extracellular domain of FLT4 consists of 7 immunoglobulin-like loops, including 12 potential glycosylation sites. On the basis of structural similarities FLT4 and the previously known FLT1 and kinase insert domain-containing receptor tyrosine kinase/fetal liver kinase 1 (KDR/FLK1) receptors constitute a subfamily of class III tyrosine kinases. FLT4 was expressed as 5.8- and 4.5-kilobase mRNAs which were found to differ in their 3' sequences and to be differentially expressed in the HEL and DAMI leukemia cells. Interestingly, a Wilms' tumor cell line, a retinoblastoma cell line, and a nondifferentiated teratocarcinoma cell line expressed FLT4, whereas differentiated teratocarcinoma cells were negative. Most fetal tissues also expressed the FLT4 mRNA, with spleen, brain intermediate zone, and lung showing the highest levels. In in situ hybridization the FLT4 autoradiographic grains decorated bronchial epithelial cells of fetal lung. No evidence was obtained for the expression of FLT4 in the endothelial cells of blood vessels.  相似文献   
93.
The activity of coumarin 7-hydroxylase (coumarin 7-hydroxylation) was inhibited in B6 mouse liver after a single injection of methylglyoxal bis(guanylhydrazone (MGBG). The decrease in the activity in vivo was greatest (70%) one day after the drug injection and the hydroxylase activity in microsomal fraction prepared from livers of MGBG-treated B6 mice was still 25% decreased 5 days after the drug. The amount of cytochrome P-450 also was decreased in MGBG-treated livers with the same time-dependency as the inhibition of coumarin 7-hydroxylation. MGBG and its close derivative 1,1'-[methylethanediylidene)dinitrilo)bis(3-aminoguanidine) (MBAG) inhibited the activity in vitro of coumarin 7-hydroxylase, benzo(a)pyrene hydroxylase and 7-ethoxy 0-de-ethylase when microsomes were prepared from livers of untreated B6 mice. In every case MBAG was a better inhibitor than MGBG in vitro. The in vitro inhibition of MGBG of several drug metabolizing enzymes was not reversed when microsomes were preincubated with 1 mM putrescine, spermidine or spermine. These results suggest that the anti-cancer drug, MGBG, has a severe effect(s) on the drug metabolizing system at concentrations reached during the treatment of patients with MGBG.  相似文献   
94.
During autumn 2005, we conducted 3,436 interviews in European and Asian countries. We found risk perceptions of avian influenza to be at an intermediate level and beliefs of efficacy to be slightly lower. Risk perceptions were higher in Europe than in Asia; efficacy [corrected] beliefs were lower in Europe than in Asia.  相似文献   
95.
Inflammation is regarded as an important mechanism in mortality and morbidity associated with exposures of cardiorespiratory patients to urban air particulate matter. We investigated the association of the chemical composition and sources of urban air fine (PM(2.5-0.2)) and coarse (PM(10-2.5)) particulate samples with the inflammatory activity in the mouse lung. The particulate samples were collected during selected seasons in six European cities using a high-volume cascade impactor. Healthy C57BL/6J mice were intratracheally instilled with a single dose (10 mg/kg) of the particulate samples. At 4, 12, and 24 h after the exposure, the lungs were lavaged and the bronchoalveolar lavage fluid (BALF) was assayed for indicators of inflammation and tissue damage: cell number, total protein, and cytokines (tumor necrosis factor [TNF]-alpha, interleukin [IL]-6, and KC). Dicarboxylic acids and transition metals, especially Ni and V, in PM(2.5-0.2) correlated positively and some secondary inorganic ions (NO3(-), NH4(+)) negatively with the inflammatory activity. Total organic matter and SO4(2-) had no consistent correlations. In addition, the soil-derived constituents (Ca2+, Al, Fe, Si) showed positive correlations with the PM(2.5-0.2)-induced inflammatory activity, but their role in PM(10-2.5) remained obscure, possibly due to largely undefined biogenic material. Markers of poor biomass and coal combustion, i.e., monosaccharide anhydrides and As, were associated with elevated PAH contents in PM(2.5-0.2) and a consistent immunosuppressive effect. Overall, our results support epidemiological findings that the local sources of incomplete combustion and resuspended road dust are important in urban air particulate pollution-related health effects.  相似文献   
96.
97.
Dyslipidaemia exists frequently after renal transplantation (RTx) and promotes atherosclerosis. In this study, we examined the association between daily intake of nutrients and serum lipids after paediatric RTx. We studied 45 children with acceptably functioning kidney grafts and adequately completed food records at a median age of 10.6 years (range 4.3–17.2 years), a median 5.2 years (range 1.0–11.0) after RTx, and 178 healthy controls at a median age of 9.0 years (range 3.2–18.7 years). Serum total cholesterol (TC), triglyceride, and apolipoprotein B concentrations were higher in the RTx patients than in the controls (P < 0.001), despite similar dietary intakes of saturated and polyunsaturated fats, and cholesterol. Both the RTx patients and controls ingested a low amount of polyunsaturated fats [mean (SD) percent of total calories (E%) 4.8 (1.3) and 4.6 (1.5), respectively] and an excessive amount of saturated fats [mean (SD) E% 14.4 (2.4) and 14.1 (2.8), respectively]. In multiple regression analyses, dietary fibre was negatively associated with serum TC concentration. The standard deviation score for body mass index was negatively associated with serum concentration of high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein diameter, and positively with serum triglyceride concentration. In addition, dietary total fat intake was positively associated with serum HDL-C. In conclusion, the higher prevalence of dyslipidaemia in our paediatric RTx patients than in the controls was not explained by the diet. However, the type of fat consumed implicates the counselling for a healthier dietary lifestyle, with an increase in the ingestion of polyunsaturated fats and a decrease in that of saturated fats.  相似文献   
98.
The combined use of acetaminophen and a nonsteroidal antiinflammatory drug has been shown to provide better postoperative analgesia than either drug alone in several adult studies. However, there are no pediatric studies analyzing similar effects when the currently recommended doses of acetaminophen are used. In a double-blind, placebo-controlled design we randomized 120 children, aged 1-9 yr, undergoing orthopedic or soft tissue surgery, into 3 groups to receive either acetaminophen 60 mg/kg rectally and 40 mg/kg orally, ketoprofen 2 mg/kg IV twice, or the combination of the active drugs. The first drug doses were given at anesthetic induction and the second doses 8 h thereafter. During anesthesia all children received sevoflurane and a continuous infusion of remifentanil. Postoperative pain was evaluated by the behavioral objective pain scale (0-9) for 24 h. The rescue medication was morphine 0.05 mg/kg IV. The primary outcome variable was morphine consumption. For statistical analysis, analysis of variance, chi2 test and Kaplan-Meier survival analysis were used. Morphine requirement was less in the combination than in the acetaminophen group both in the postanesthesia care unit (2.5 +/- 1.7 versus 3.9 +/- 2.1 morphine doses) and during the 24-h postoperative follow-up (4.1 +/- 2.5 versus 5.9 +/- 2.9 morphine doses) (P < 0.05). No differences existed between the ketoprofen and the acetaminophen groups. The objective pain scale scores were lowest in the combination group both in the postanesthesia care unit and in the postoperative ward (P < 0.05). When children were divided based on their surgery, opioid requirement and pain scores were less in the combination than in the parent drug groups only after orthopedic surgery. The combination of acetaminophen 100 mg/kg and ketoprofen 4 mg/kg in a day provided better analgesia and lower pain scores after orthopedic, but not soft tissue, surgery in children.  相似文献   
99.
BACKGROUND: Hypercholesterolemia after organ transplantation is common. Previously, we observed higher serum total cholesterol (TC) concentrations in our pediatric kidney than liver or heart transplant recipients. To find an explanation to the observed difference, our kidney recipients' cholesterol synthesis and absorption efficiency was compared to those of liver and heart recipients. METHODS: Serum noncholesterol sterol ratios (10 x mmol to the mol of TC, surrogate estimates of hepatic cholesterol synthesis and intestinal absorption) were studied in 50 pediatric kidney, 25 liver and 12 heart transplant recipients without diabetes or cholestasis, and in 29 controls. RESULTS: The kidney recipients had lower Delta-cholesterol (P=0.031), similar lathosterol and higher desmosterol ratios (markers of cholesterol synthesis) (P=0.020), and similar campesterol and sitosterol ratios (markers of cholesterol absorption) when compared to the controls. The liver recipients had lower campesterol ratios than the kidney recipients and controls (P=0.002). Glomerular filtration rates were not associated with the ratios of noncholesterol sterols. Multivariate analysis showed markers of cholesterol synthesis to be lower and absorption to be higher in the kidney than the liver or the heart transplant recipients. Weight-adjusted dosages of immunosuppressive agents were associated with some ratios of noncholesterol sterols and cholestanol though these varied between the transplant recipient groups. CONCLUSIONS: Serum TC concentration in kidney recipients was not significantly associated with absorption efficiency or synthesis of cholesterol, though kidney transplantation was associated with low synthesis and high absorption efficiency of cholesterol. Immunosuppressive therapy with cyclosporine and methylprednisolone may modulate absorption efficiency and synthesis of cholesterol.  相似文献   
100.
One hundred and twenty-one cleft children (67 with isolated cleft lip (CL), 32 with isolated submucous cleft palate (SMCP), and 22 with combined cleft lip and submucous cleft palate (CL + SMCP)) were compared retrospectively from lateral cephalograms taken at a mean age of 6.2 years (range 5.5–7.9). None of the children had had their palates repaired or been operated on to treat velopharyngeal insufficiency (VPI). The children with CL + SMCP and CL had similar morphology. They had greater maxillary length, greater maxillary and mandibular prominence, less vertical growth pattern, less deep nasopharyngeal airways, and thinner upper lips than those with isolated SMCP. After 6 years of age one patient with CL + SMCP, none with CL, and 16 with SMCP needed operations for VPI. This small series suggests that children with CL + SMCP and SMCP have different morphology. Although CL + SMCP is a combination of two types of clefts, it seems to be associated with similar morphology to CL.  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