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   430544篇
  免费   29422篇
  国内免费   6496篇
耳鼻咽喉   5672篇
儿科学   8630篇
妇产科学   10538篇
基础医学   58329篇
口腔科学   12504篇
临床医学   36746篇
内科学   85265篇
皮肤病学   8904篇
神经病学   29647篇
特种医学   15928篇
外国民族医学   103篇
外科学   66201篇
综合类   20402篇
现状与发展   7篇
一般理论   70篇
预防医学   21403篇
眼科学   10894篇
药学   36631篇
  63篇
中国医学   5791篇
肿瘤学   32734篇
  2022年   3583篇
  2021年   5625篇
  2020年   4050篇
  2019年   4538篇
  2018年   6453篇
  2017年   5189篇
  2016年   5264篇
  2015年   6642篇
  2014年   8920篇
  2013年   10463篇
  2012年   14699篇
  2011年   15003篇
  2010年   9589篇
  2009年   8560篇
  2008年   12391篇
  2007年   13144篇
  2006年   12837篇
  2005年   11635篇
  2004年   10272篇
  2003年   9835篇
  2002年   9258篇
  2001年   28999篇
  2000年   29437篇
  1999年   24338篇
  1998年   5573篇
  1997年   4670篇
  1996年   4180篇
  1995年   3771篇
  1994年   3368篇
  1993年   2995篇
  1992年   16197篇
  1991年   14933篇
  1990年   14280篇
  1989年   14053篇
  1988年   12669篇
  1987年   12140篇
  1986年   11170篇
  1985年   10374篇
  1984年   6949篇
  1983年   5625篇
  1982年   2731篇
  1979年   5488篇
  1978年   3361篇
  1977年   2976篇
  1975年   2647篇
  1974年   3069篇
  1973年   2868篇
  1972年   2833篇
  1971年   2773篇
  1969年   2550篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
We report the case of a fetus with a sonographic mid-gestation diagnosis of hyperechogenic cerebellum suspected to be of hemorrhagic origin on fetal brain magnetic resonance imaging (MRI). No etiological factors for fetal hemorrhage were found other than a maternal heterozygocity for factor V Leiden. Following termination of the pregnancy, autopsy confirmed the prenatal diagnosis of massive cerebellar hemorrhage without underlying vascular anomaly. As an additional tool to ultrasonography, fetal brain MRI can affirm the hemorrhagic origin of hyperechogenic cerebellar lesions, especially by showing a high signal on T1-weighted images.  相似文献   
994.
A genome-wide screen was conducted using a large white sample to identify QTLs for FNCS geometry. We found significant linkage of FNCS parameters to 20q12 and Xq25, plus significant epistatic interactions and sex-specific QTLs influencing FNCS geometry variation. INTRODUCTION: Bone geometry, a highly heritable trait, is a critical component of bone strength that significantly determines osteoporotic fracture risk. Specifically, femoral neck cross-sectional (FNCS) geometry is significantly associated with hip fracture risk as well as genetic factors. However, genetic research in this respect is still in its infancy. MATERIALS AND METHODS: To identify the underlying genomic regions influencing FNCS variables, we performed a remarkably large-scale whole genome linkage scan involving 3998 individuals from 434 pedigrees for four FNCS geometry parameters, namely buckling ratio (BR), cross-sectional area (CSA), cortical thickness (CT), and section modulus (Z). The major statistical approach adopted is the variance component method implemented in SOLAR. RESULTS: Significant linkage evidence (threshold LOD = 3.72 after correction for tests of multiple phenotypes) was found in the regions of 20q12 and Xq25 for CT (LOD = 4.28 and 3.90, respectively). We also identified eight suggestive linkage signals (threshold LOD = 2.31 after correction for multiple tests) for the respective geometry traits. The above findings were supported by principal component linkage analysis. Of them, 20q12 was of particular interest because it was linked to multiple FNCS geometry traits and significantly interacted with five other genomic loci to influence CSA variation. The effects of 20q12 on FNCS geometry were present in both male and female subgroups. Subgroup analysis also revealed the presence of sex-specific quantitative trait loci (QTLs) for FNCS traits in the regions such as 2p14, 3q26, 7q21 and 15q21. CONCLUSIONS: Our findings laid a foundation for further replication and fine-mapping studies as well as for positional and functional candidate gene studies, aiming at eventually finding the causal genetic variants and hidden mechanisms concerning FNCS geometry variation and the associated hip fractures.  相似文献   
995.
The efficacy of two dry cow treatment (DCT) regimens for subclinical Staphylococcus aureus mastitis was evaluated in naturally infected dairy cows. At dry‐off, cows were assigned to two treatment groups by randomized blocks on the basis of parity and somatic cell count (SCC). Two antibiotic DCT regimens were used, namely: (1) a single intramammary infusion containing sodium nafcillin, procaine benzylpenicillin and dihydrostreptomycin; and (2) systemic cefquinome administered intramuscularly, twice at a 24‐h interval. In the intramammary (IMM) treatment group, the S. aureus intramammary infection (IMI) rate was reduced from 40% (56/140 quarters) before dry‐off to 20% (28/140) after calving. Seventy per cent (39/56) of the S. aureus‐positive quarters were negative after calving, and 13% (11/84) of the negative quarters were positive after calving. In the systemic treatment group, the S. aureus IMI rate increased from 39% (29/74 quarters) before dry‐off to 55% (41/74) after calving. Twenty‐eight per cent (8/29) of the S. aureus‐positive quarters were negative after calving and 45% (20/45) of the negative quarters were positive after calving. The odds ratio of an S. aureus‐positive quarter being negative after calving in the IMM group relative to the systemic therapy group was 44.6 (95% confidence interval = 2.1–909.1, P < 0.01). Parity, quarter, milk SCC and N‐acetyl‐βD‐glucosaminidase were tested in the model, and were found to have no significant effect on S. aureus cure rates or new IMI rates. The IMM treatment resulted in a higher cure rate compared with that observed in previous studies. The very low cure rate after systemic cefquinome treatment was comparable to the spontaneous cure rate observed in untreated controls in previous studies. The unfavourable results of the cefquinome systemic DCT might reflect inadequate pharmacokinetic properties of the drug regarding poor udder penetration in subclinical mastitis and short antimicrobial effect compared with the IMM treatment.  相似文献   
996.
The bronchomotor effects of a deep inhalation (DI) may provide relevant information about the mechanisms of exercise-induced airway obstruction in children and may be assessed by respiratory conductance (Grs) measured using the forced oscillation technique. The aims of the present study were to assess the effect of DI on Grs after exercise in relationship to the lung function response to exercise. Grs at 12 Hz using a head generator and spirometric data were measured in 62 children suspected of asthma before and 5 min after a 6-min free run. After exercise, Grs was significantly increased by DI in 38 subjects, who also showed larger Grs and forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) responses to exercise than the 24 nonresponders. Stepwise regression indicated significant correlation between the response of Grs to DI and both Grs and FEV1/FVC responses to exercise. The data are consistent with exercise-induced bronchoconstriction being reversed by deep inhalation.  相似文献   
997.
Our objective was to analyze problems in the perioperative management and long-term outcome of living donor liver transplantation (LDLT) for biliary atresia (BA). Many reports have described the effectiveness of liver transplantation (LT) for BA, particularly in pediatric cases, but little information is available regarding LT in adults (> or =16 years old). Between June 1990 and December 2004, 464 patients with BA underwent LDLT at Kyoto University Hospital, of whom 47 (10.1%) were older than 16 years. In this study, we compared the outcomes between adult (> or =16 years old) and pediatric (<16 years old) patients. The incidence of post-transplant intestinal perforation, intra-abdominal bleeding necessitating repeat laparotomy and biliary leakage was significantly higher (p < 0.0001, <0.001 and <0.001, respectively) in adults. Overall cumulative 1-, 5- and 10-year survival rates in pediatric patients were significantly higher (p < 0.005) than in adults. Two independent prognostic determinants of survival were identified: a MELD score over 20 and post-transplant complications requiring repeat laparotomy. Outcome of LDLT in adult BA patients was poorer than in pediatric patients. It seems likely that LT will be the radical treatment of choice for BA and that LDLT should be considered proactively at the earliest possible stage.  相似文献   
998.
Summary We observed a rare cerebrovascular anomaly in a patient with brain-stem infarction. Two right vertebral arteries arose from the subclavian artery and communicated directly with each other under the transverse foramen of the fourth cervical vertebra. The left vertebral artery consisted of a rudimentary artery that arose from the left subclavian artery, ran through the transverse foramen of the sixth cervical vertebra and then tapered down to disappear at the fourth/fifth cervical vertebrae, plus a second, accessory artery that arose from a branch of the left thyrocervical trunk, ran through the transverse foramen of the fifth cervical vertebra and tapered off to disappear at the first/second cervical vertebrae.  相似文献   
999.
In the past 20 years, we experienced 242 myasthenic patients in our hospital. Fifty five cases were administered high doses of adrenocorticosteroid hormone for a long time. Among them, we analysed 39 cases with complete clinical records from admission to the present. We analysed 5 additional cases in whom responses to the therapy somewhat unique in that four cases have not shown any improvement until the drug was reduced to certain dosages, and in the 5th case change of method from alternate-day to every day brought good recovery of the symptoms. As a result, adrenocorticosteroid hormone was effective for 100% of the patients in this series. However, complete remission appeared in the above mentioned 10 patients (26%), after 2-3 years' continuous administration. Prognosis was far better in those who showed shorter durations between the onset of the disease and thymectomy or thymectomy than in those of longer one. In these cases, the maximum daily doses were 60-100 mg in alternate-day administration, and the total amount of prednisolone was 9-15 g in individual cases. Through data of these cases, it is recommended that the maximum dosage is to be continued for as long as 2 to 19 weeks with average 7 weeks.  相似文献   
1000.
We treated 5 cases of severe hydronephrosis with balloon dilation. Those hydronephrosis were due to the ureteral stricture with small stone fragments after ESWL (Lithostar). In each case, in situ ESWL had been done on a long-lodged ureteric stone with severe hydronephrosis. And even after the disintegration of stone with ESWL, hydronephrosis remained due to ureteral stricture with small stone fragments. Balloon dilation was done through percutaneous nephrostomy tract in 4 cases and via retrograde transurethral routine in 1 case. Balloon dilation catheter (7 fr. 6 mm diameter 4-10 cm length, Bard Co.) was used. There was no need for stone extraction. After dilation, ureteric stents (8.2/7 fr.) were kept in place for 4-8 weeks. Intravenous urogram was taken on 4-8 weeks after removing ureteric stents. In all of the 5 cases, improvement of hydronephrosis was remarkable. And there was no residual stone fragments in 4 cases. It is concluded that balloon dilation for ureteral stricture with stone fragments after ESWL is very useful. For the valid evaluation of balloon dilation, further experience and longer observation are requisite.  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