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   449篇
  免费   21篇
  国内免费   5篇
耳鼻咽喉   1篇
儿科学   21篇
妇产科学   11篇
基础医学   27篇
口腔科学   6篇
临床医学   28篇
内科学   74篇
皮肤病学   8篇
神经病学   16篇
特种医学   83篇
外科学   81篇
综合类   42篇
预防医学   16篇
眼科学   6篇
药学   21篇
肿瘤学   34篇
  2022年   1篇
  2021年   4篇
  2020年   3篇
  2019年   2篇
  2018年   10篇
  2017年   5篇
  2016年   3篇
  2015年   7篇
  2014年   8篇
  2013年   21篇
  2012年   6篇
  2011年   11篇
  2010年   25篇
  2009年   24篇
  2008年   7篇
  2007年   13篇
  2006年   29篇
  2005年   15篇
  2004年   38篇
  2003年   16篇
  2002年   10篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   25篇
  1997年   22篇
  1996年   21篇
  1995年   28篇
  1994年   16篇
  1993年   7篇
  1992年   4篇
  1991年   3篇
  1990年   4篇
  1989年   13篇
  1988年   10篇
  1987年   7篇
  1986年   9篇
  1985年   2篇
  1984年   5篇
  1983年   7篇
  1982年   3篇
  1981年   5篇
  1980年   6篇
  1978年   4篇
  1977年   4篇
排序方式: 共有475条查询结果,搜索用时 31 毫秒
91.
92.
Background Though the use of median stermotomy has been fairly standardized for the approach to the heart and great vessels, since the advent of cosmetically appealing incisions, thoracotomy has come to be a justifiable alternative incision. This paper presents our experience with this approach and the advantages over the conventional approach as well as over other incisions for the correction of intra-cardiac anomalies. Methods 93 patients underwent open cardiac procedures using the posterior thoracotomy approach since June 1997 to December 2000. There were 69 patients with ostium secundum atrial septal defects and 12 patients with sinus venous defects. Other anomalies included perimembranous ventricular septal defects in 3 patients, partial atrioventricular septal defects in 3 patients and transitional atrioventricular septal defects in 2 patients. Besides these, one patient each underwent atrial septectomy with right modified Blaloc—Taussing shunt and correction of hemianomalous pulmonary venous connection with intact atrial septum using this approach. The median age of the patients was 8 years with a range of 10 months to 41 years. 10 patients were males. Results The median operation time (skin to skin) was 236 minutes. Median bypass times and aortic cross clamp times were 63 minutes and 31.5 minutes respectively. The median ICU stay was 25.2 hours. There were no significant immediate post operative complications requiring intervention in any patient. The mean chest drainage was 80 ml per 24 hours. One patient had a superficial wound dehiscence which healed with daily dressings One patient had atelectasis of the right upper lobe which recovered with chest physiotherapy. All patients are on regular follow up to assess the status of their scars. One patients developed a mass on the right atrial free wall following closure of atrial septal defect one year earlier and the underwent reoperation for removal of the mass. Patients on follow up were interrogated and all were satisfied with the cosmesis of their scars. None of the patients had any physical disability due to their scars. Conclusions The limited posterior thoracotomy incision offers a cosmetically attractive approach to the heart in selected patients. The approach is easy and the techniques reproducible. The technique carries with it no additional risk and has the advantage of not interfering with future development of the breast in young pre pubertal girls.  相似文献   
93.
Kimura disease is a rare idiopathic chronic inflammatory disease, characterized by subcutaneous nodular lesions in the head and neck area. Ophthalmic manifestation of Kimura disease involves orbital and eyelid lesions mostly in Asian patients, but it has been described in White patients and Black Caribbean patients. Kimura disease is usually associated with eosinophilia and occasionally with renal disease. Here, we report a case of Kimura disease of the eyelid in a 50-year-old Indian man with eosinophilia. The main differential diagnosis was angiolymphoid hyperplasia with eosinophilia. Histology is crucial to separate these two entities, and our case was shown to be Kimura disease by histology. To our knowledge, this is the first report of a person of Indian origin to develop Kimura disease involving the eyelid.  相似文献   
94.
In human in-vitro fertilization (IVF)-embryo transfer, the in-vitro culture environment differs from in-vivo conditions in that the oxygen concentration is higher, and in such conditions the mouse embryos show a higher concentration of reactive oxygen species (ROS) in simple culture media. ROS are believed to cause damage to cell membranes and DNA fragmentation in somatic cells. This study was conducted to ascertain the level of H2O2 concentration within embryos and the morphological features of cell damage induced by H2O2. A total of 62 human oocytes and embryos (31 fragmented, 15 non-fragmented embryos, 16 unfertilized oocytes) was obtained from the IVF-embryo transfer programme. The relative intensity of H2O2 concentrations within embryos was measured using 2',7'-dichlorodihydrofluorescein diacetate by Quanti cell 500 fluorescence imaging and DNA fragmentation was observed with transmission electron microscopy and an in-situ apoptosis detection kit. The H2O2 concentrations were significantly higher in fragmented embryos (72.21 +/- 9.62, mean +/- SEM) compared to non-fragmented embryos (31.30 +/- 3.50, P < 0.05) and unfertilized oocytes (30.75 +/- 2.67, P < 0.05). Apoptosis was observed only in fragmented embryos, and was absent in non-fragmented embryos. Electron microscopic findings confirmed apoptotic bodies and cytoplasmic condensation in the fragmented blastomeres. We conclude that there is a direct relationship between increased H2O2 concentration and apoptosis, and that further studies should be undertaken to confirm these findings.   相似文献   
95.
Acute porphyria is rare in orientals. We describe a Chinese woman with recurrent generalised tonic-clonic seizures and abdominal pain. Genomic DNA studies identified a heterozygous base substitution from guanine to adenine at nucleotide position 503, resulting in substitution of arginine by histidine at position 168 of the protein (R168H). This genetic abnormality is similar to the mutation reported in Caucasians with variegate porphyria. To the best of our knowledge, this is the first report in the English literature a Chinese patient with variegate porphyria with an identifiable mutation. A brief review of porphyria is presented.  相似文献   
96.

Background

Despite its known advantages, breastfeeding rates are low world over. Large number of factors affect breastfeeding. This study was designed to detect maternal and neonatal factors that adversely affect breastfeeding in the perinatal period.

Methods

A prospective, single-blinded study was conducted on randomly chosen mother-infant pairs in the maternity ward of a tertiary care service hospital. Only full term singletons born by normal vaginal delivery were studied. The B.R.E.A.S.T observation score and time spent by the infant at the mother''s breast were primary outcome variables. Maternal age, gravida, para status and education level were recorded. Birth weight, sex, gestation age of the infant and time interval from birth to observation were also recorded. Initial univariate analysis followed by multivariate analysis was performed using SPSS ver 7.5 software.

Results

A total of 54 mother-infant pairs formed the study group; 19(35.2%) were primigravidas. Primigravidas status of the mother led to significantly lower scores (p<0.04; 95% CI 0.10 to 3.62) as did maternal age < 26 years (p<0.04; 95% CI 0.2. to 3.46) on univariate analysis. Low birth weight (<2500 g) was the only neonatal factor that significantly lowered breastfeeding scores (p<0.02;95%Cl 0.56 to 6.31). On multivariate analysis only primigravida status was significantly associated with lower scores (p<0.02). The alpha value of the study was 5% and the power was 74%. Time spent by infant on breast was not significantly different between primigravida and non-primigravida mothers.

Conclusion

Primigravida status adversely affects breastfeeding scores; therefore counseling and support should be focused on this group. Extra care should also be taken to ensure adequate breastfeeding by younger mothers and in those with low birth weight infants. Larger studies with long-term follow up will be able to identify other factors and dertermine the effects of focused counseling and support in the perinatal period upon long-term breastfeeding rates.Key Words: Breastfeeding, Primigravida, Counseling  相似文献   
97.
Despite extensive research into its patho-physiology, investigations and treatment, sepsis remains an important cause of neonatal morbidity and mortality. The incidence in developing countries is 10 times that in the developed world. A large number of pro-and anti-inflammatory cytokines (interleukins, eicosanoids, tumour necrosis factor-alpha, nitric oxide) have been identified, the interplay of which leads to the Systemic Inflammatory Response Syndrome (SIRS) which can have devastating consequences on all systems of the body. In India the common organisms include Staphylococcus, E coli, Klebsiella and Candida. A number of maternal and neonatal risk factors have been identified. The initial signs and symptoms are subtle and can easily be missed. Early investigations and screening tests are important and a promising number of new tests are being studied. The gold standard for diagnosis is a positive culture from a body fluid or local source in the presence of SIRS. The threshold for starting antibiotics should be low in high-risk neonates and broad spectrum antibiotics covering the likely organisms should be given intravenously in all suspected cases in a hospital setting. This should be continued for at least 24-48 hours (till negative reports are available) in suspected cases and for 2-3 weeks in proven cases. Prophylaxis is aimed at preventing nosocomial and cross infections. Strict hand-washing, meticulous asepsis protocols, identification of high risk groups and prompt and better screening tests are essential in controlling this problem.KEY WORDS: Neonate, Sepsis, Systemic inflammatory response syndrome  相似文献   
98.
Shiao  YH; Lee  SH; Kasprzak  KS 《Carcinogenesis》1998,19(7):1203-1207
Nickel(II) compounds are known human and animal carcinogens. In this study, the effects of nickel(II) acetate on cell cycle, apoptosis and p53 expression were investigated in order to unveil the elements of early cellular responses to the metal. Chinese hamster ovary (CHO) cells were grown for 72 h in Ham's F-12 medium containing 0, 40, 80, 160, 240, 320, 480 or 640 microM nickel(II) acetate. DNA fragmentation, representative of apoptosis, was examined by agarose gel electrophoresis. The distribution of cells among various phases of cell cycle was determined by DNA flow cytometry. Expression of p53 protein was measured by the Western blotting technique. DNA fragmentation was detectable in cells treated with > or = 160 microM nickel(II) and its intensity increased with increasing nickel(II) concentration. The proportion of cells at S phase declined in a nickel(II) concentration- dependent manner. The decline was accompanied by an increase of cell proportion in G2/M phase and the increase became statistically significant in cells exposed to at least 480 microM nickel(II). Expression of p53 protein was not different from that in the control among samples treated with < or = 480 microM nickel(II). However, an extra fraction that migrated close to the p53 protein fraction was detected in cells treated with 640 microM nickel(II). Our findings suggest that nickel(II) modulates cellular response through effectors involved in both G2/M arrest and apoptosis regulatory pathways. The proportion of cells arrested at G2/M phase or undergoing apoptosis depends directly on nickel(II) concentration. High concentration of nickel(II) appears to up-regulate protein(s) other than the common form of p53 protein.   相似文献   
99.
陈耀明  蔡纯一  龚康孙 《药学学报》1989,24(12):887-894
本文报道9个估计具有血管紧张素转化酶抑制活性的N-(4-乙氧羰基-4-取代丁酰基)-N-取代甘氨酸及其相应叔丁酯的合成和鉴定。药理初试结果,化合物Ⅶ7和Ⅶ9显示明显降压活性。  相似文献   
100.
The purpose of this study was to evaluate the gait responses of individuals with low vision compared to those of normal-visioned individuals when their vision is challenged by extreme levels of light. Twenty subjects with age-related maculopathy (ARM) and 20 subjects with normal vision first walked along a flat, unobstructed path immediately after the ambient light level was changed from low (5 lux) to high (2500 lux). The procedure was repeated after the light was reduced from the high to the low level. Muscle activity, temporal and kinematic variables, and ground reaction forces were used to detect gait characteristics because of ambient light level changes. Data suggested that ARM subjects walked slower and with more caution than normal subjects but that these differences were not related to ambient light level. Head angle, an estimate of gaze direction, was lower for ARM subjects during high light, but the gaze direction for both groups was low during low light. Among these ARM subjects, extreme levels of ambient light did not affect gait; subjects made adaptations that were reasonable to encourage safe ambulation, despite the direction of light change. Normal-visioned individuals in this study experienced more difficulty in low light than high light situations.  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