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   444篇
  免费   21篇
耳鼻咽喉   5篇
儿科学   15篇
妇产科学   13篇
基础医学   73篇
口腔科学   10篇
临床医学   51篇
内科学   69篇
皮肤病学   5篇
神经病学   14篇
特种医学   6篇
外科学   30篇
综合类   18篇
一般理论   1篇
预防医学   64篇
眼科学   13篇
药学   54篇
中国医学   2篇
肿瘤学   22篇
  2023年   5篇
  2022年   13篇
  2021年   14篇
  2020年   10篇
  2019年   11篇
  2018年   14篇
  2017年   10篇
  2016年   9篇
  2015年   11篇
  2014年   21篇
  2013年   32篇
  2012年   30篇
  2011年   26篇
  2010年   21篇
  2009年   18篇
  2008年   19篇
  2007年   24篇
  2006年   21篇
  2005年   25篇
  2004年   11篇
  2003年   11篇
  2002年   16篇
  2001年   7篇
  2000年   10篇
  1999年   6篇
  1998年   4篇
  1997年   5篇
  1996年   2篇
  1995年   2篇
  1992年   3篇
  1991年   2篇
  1990年   3篇
  1989年   4篇
  1988年   2篇
  1987年   2篇
  1986年   2篇
  1985年   4篇
  1984年   3篇
  1981年   6篇
  1979年   5篇
  1975年   2篇
  1974年   3篇
  1973年   1篇
  1972年   2篇
  1971年   2篇
  1970年   2篇
  1969年   1篇
  1968年   2篇
  1967年   1篇
  1965年   1篇
排序方式: 共有465条查询结果,搜索用时 15 毫秒
1.
The porcine circovirus type 2 (PCV2) is a swine infectious viral pathogen of great significance in global swine herds. It was recently detected at another Province of South Africa sequel to the first detection of North American‐like strain (PCV2a) at Gauteng about two decades ago, but there is a dearth of information about the genomic features and diversity of the viral strains in circulation within the country and the entire sub‐Saharan Africa region. To date, only one complete genome of the virus from South Africa is available on global data base. This current effort is therefore geared towards the full‐genome characterization of the circulating PCV2 strains in the pigs of Eastern Cape Province. With the use of conventional polymerase chain reaction method, fifteen complete PCV2 genomes were successfully amplified, sequenced and assembled from field samples obtained from non‐vaccinated pigs in the region. Neighbor Joining and Maximum Likelihood phylogenetic analyses of the ORF2 gene and full genomes unanimously showed that most of the assembled genomes (11) belong to genotype PCV2b. Furthermore, three of the characterized sequences formed clade with other reference mutant PCV2b and PCV2b subtype 1C (i.e. PCV2d) strains from the USA, China and South Korea. The last sequence, however, clustered with other reference strains belonging to PCV2 intermediate clade 2 (PCV2‐IM2), recently identified in a global PCV2 strains phylogenetic analysis. This study reports the first complete genome sequences of PCV2b, PCV2d and PCV2‐IM2 in pigs from South Africa, and it gives a possible insight into the genetic characteristics and variability of the viral strains presently in circulation within the country. It further emphasizes the need for more stringent measures in curtailing the introduction and spread of transboundary swine pathogens in the country and entire Southern African region.  相似文献   
2.
3.
Recent studies have shown that tetrafluoroethylene is a renal and hepatic carcinogen in the rat. In this study, we have examined the ability of a single i.p. dose of 1,1,2,2-tetrafluoroethyl-l-cysteine (TFEC), a major metabolite of tetrafluoroethylene, to produce hepatic and renal injury in male and female rats. We have also examined the effect of blocking the renal organic anion transport system with probenecid and of inhibiting the activity of cysteine conjugate β-lyase with aminooxyacetic acid on the extent of renal injury produced by TFEC. Doses of ≥12.5 mg/kg TFEC produced renal tubular necrosis to the pars recta of the proximal tubules within 24 h in both male and female rats. This was associated with an increased kidney to body weight ratio and plasma urea at doses of ≥25 mg/kg. No consistent evidence of liver injury was seen at doses up to 50 mg/kg TFEC in rats of either sex, although occasional vacuolation of hepatocytes and a small dose-related increase in liver to body weight ratio was observed. Prior treatment of female rats with probenecid completely prevented the renal injury produced by either 25 or 50 mg/kg TFEC as judged by plasma urea and histopathology. However, prior treatment of female rats with aminooxyacetic acid afforded no protection against the nephrotoxicity produced by either TFEC or the cysteine conjugate of hexachloro-1,3-butadiene. Thus no major sex difference in nephrotoxicity in the rat was seen with TFEC, while accumulation of TFEC, or its N-acetyl derived metabolite, into renal proximal tubular cells via a probenecid sensitive transport system appears to be a key event in the mechanism of nephrotoxicity. The lack of protection observed with the cysteine conjugate β-lyase inhibitor, aminooxyacetic acid, may reflect the inability to completely inhibit the mitochondrial form of this enzyme and thereby prevent the formation of the reactive metabolite. Our acute studies provide no insight concerning the liver carcinogenicity of tetrafluoroethylene. Received: 8 December 1997 / Accepted: 3 February 1998  相似文献   
4.
Risk factors that may independently predict mortality and morbidity in patients with abdominal gunshot wounds have not been fully elucidated. We prospectively studied the effects of 12 potential risk factors on mortality and morbidity in 82 patients with abdominal gunshot wounds who required laparotomy. Univariate analysis of these factors revealed that shock on admission, presence of penetrating colon injury and number of intra-abdominal organs injured (NOI)>2 were associated with greater than threefold increased incidence of death (p<0.05). Penetrating abdominal trauma index (PATI) score>15 was associated with twentyfold increased incidence of death (P<0.0001). Multivariate analysis showed that only PATI (P=0.001), number of postoperative complications per patient (N(comp)) (P=0.023) and presence of shock on admission (P=0. 028) were independently significant in predicting mortality. PATI was the only risk factor that independently predicted the development of postoperative infectious complications and N(comp) (P<0.0001). The type of gun used was not a significant risk factor (P>0.05). The 15 (18.3%) non-survivors were significantly older than survivors (P=0.02), had longer operations (P=0.004) and their NOI, PATI and N(comp) were significantly higher (P<0.001). The uniformly prolonged injury to surgery time in all patients contributed to the high incidence of infectious complications (62.2%) and mortality. PATI score was the most important factor found to be independently associated with mortality and morbidity in our subset of patients with prolonged injury to surgery time and high rate of colon injury.  相似文献   
5.
Anomalous right coronary artery from the pulmonary artery (ARCAPA) is a rare congenital coronary anomaly that has an incidence of 0.002%. We report a case of a previously healthy female who presented to our hospital with pneumonia and was incidentally discovered to have ARCAPA. This was initially diagnosed on echocardiography by the unusual echocardiographic finding of multiple color flow Doppler signals around the right ventricular free wall and apex which were subsequently confirmed by angiography to be due to extensive collateral circulation between the left and right coronary arteries. This represents an unusual echocardiographic manifestation of this very rare condition.  相似文献   
6.
The current study is an effort to investigate the chemical constituents and antioxidant potential of Cnidoscolous chayamansa McVaugh (Euphorbiacea) root on carbon tetrachloride-induced liver damage. Albino rats were grouped into four: A - D. Groups A and B received 1?mL/kg BW of olive oil and 1?mL/kg body weight (BW) of carbon tetrachloride (CCl4), respectively, for 8 days while those in C and D received 1?mL/ kg BW each of CCl4 and 500 and 1000?mg/kg BW of aqueous extract of C. chayamansa root, respectively, for the same period. Chemical analysis of the plant root revealed the presence of tannins, phenolics, flavonoids, saponins, Fe, Zn, Mg, Ca, vitamins A and C. Administration of CCl4 resulted in significant increase (P?<0.05) in liver malondialdehyde concentration while the activities of liver alkaline phosphatase, superoxide dismutase, glutathione peroxidase and catalase were significantly reduced (P?<0.05). Simultaneous administration of CCl4 and the plant extract at 500 and 1000?mg/kg BW produced values of these biochemical parameters that compared favourably with the control (P?>0.05) in addition to increasing superoxide dismutase activity in the liver (P?<0.05). We conclude that aqueous extract of C. chayamansa root possessed antioxidant activity and protected the hepatocyte against CCl4-induced damage. The antioxidant activity of the plant may be due to its chemical constituents.  相似文献   
7.
8.
9.

Background

The management of childhood intussusception in our sub-region is still via surgical intervention. Currently, the gold standard of treatment is non-operative reduction. We sought to assess the suitability of hydrostatic (saline) reduction of intussusception in children in our institution.

Materials and methods

A prospective study was conducted between January 2016 and June 2017 in all children with ultrasound confirmed intussusception at a tertiary teaching hospital in Nigeria. All children excluding those with signs of peritonitis, bowel gangrene and intestinal prolapse were selected for ultrasound-guided hydrostatic reduction (USGHR). We allowed a maximum of three attempts at reduction.

Results

The age range was 3 months to 48 months with a mean of 10.8?±?9.1 months. Forty percent (N?=?18) presented after 24 h of onset of symptoms. The success rate of hydrostatic reduction with saline enema was 84.4% (N?=?38). Two (4.4%) perforations occurred during the procedure. Three (7.5%) patients had recurrent intussusception within six months. The duration of symptoms greater than 24 h, age and sex of patients did not influence successful reduction p?>?0.05. The duration of admission between those who had successful non-operative reduction and those who subsequently had operative reduction and or resection attained statistical significant difference, p?=?0.001. There was no mortality. We achieved a 68% decrease in the operative reduction of intussusception using USGHR as the primary modality of treatment.

Conclusion

Our study found out that USGHR is a suitable alternative for the treatment of childhood intussusception.
  相似文献   
10.
ObjectiveTo assess the effectiveness of a multimedia informed consent tool for adults participating in a clinical trial in the Gambia.MethodsAdults eligible for inclusion in a malaria treatment trial (n = 311) were randomized to receive information needed for informed consent using either a multimedia tool (intervention arm) or a standard procedure (control arm). A computerized, audio questionnaire was used to assess participants’ comprehension of informed consent. This was done immediately after consent had been obtained (at day 0) and at subsequent follow-up visits (days 7, 14, 21 and 28). The acceptability and ease of use of the multimedia tool were assessed in focus groups.FindingsOn day 0, the median comprehension score in the intervention arm was 64% compared with 40% in the control arm (P = 0.042). The difference remained significant at all follow-up visits. Poorer comprehension was independently associated with female sex (odds ratio, OR: 0.29; 95% confidence interval, CI: 0.12–0.70) and residing in Jahaly rather than Basse province (OR: 0.33; 95% CI: 0.13–0.82). There was no significant independent association with educational level. The risk that a participant’s comprehension score would drop to half of the initial value was lower in the intervention arm (hazard ratio 0.22, 95% CI: 0.16–0.31). Overall, 70% (42/60) of focus group participants from the intervention arm found the multimedia tool clear and easy to understand.ConclusionA multimedia informed consent tool significantly improved comprehension and retention of consent information by research participants with low levels of literacy.  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