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   175650篇
  免费   10048篇
  国内免费   456篇
耳鼻咽喉   2282篇
儿科学   5590篇
妇产科学   3692篇
基础医学   23741篇
口腔科学   7555篇
临床医学   13036篇
内科学   39446篇
皮肤病学   4396篇
神经病学   14657篇
特种医学   5467篇
外国民族医学   26篇
外科学   21876篇
综合类   1425篇
现状与发展   1篇
一般理论   60篇
预防医学   18073篇
眼科学   3259篇
药学   10645篇
中国医学   692篇
肿瘤学   10235篇
  2023年   935篇
  2022年   2030篇
  2021年   3823篇
  2020年   2568篇
  2019年   3617篇
  2018年   5051篇
  2017年   3765篇
  2016年   3517篇
  2015年   4073篇
  2014年   5618篇
  2013年   7105篇
  2012年   11055篇
  2011年   11461篇
  2010年   5819篇
  2009年   5256篇
  2008年   8904篇
  2007年   9518篇
  2006年   8842篇
  2005年   9100篇
  2004年   8552篇
  2003年   7807篇
  2002年   5871篇
  2001年   5001篇
  2000年   4987篇
  1999年   4387篇
  1998年   1589篇
  1997年   1321篇
  1996年   1310篇
  1995年   1111篇
  1994年   1093篇
  1993年   988篇
  1992年   2673篇
  1991年   2587篇
  1990年   2359篇
  1989年   2357篇
  1988年   2123篇
  1987年   1971篇
  1986年   1844篇
  1985年   1764篇
  1984年   1264篇
  1983年   1016篇
  1982年   572篇
  1981年   522篇
  1980年   495篇
  1979年   923篇
  1978年   608篇
  1977年   480篇
  1975年   547篇
  1974年   546篇
  1973年   547篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
Although previous studies have shown successful treatment of persistent diarrhea (PD) with the use of yogurt-based diets, some recent ones speculate the need of special formulas for the nutritional management of PD complicated cases. In the present study, we tested the hypothesis that the consumption of 3 lactose-free diets, with different degrees of complexity, is associated with lower stool output and shorter duration of diarrhea when compared with the use of a yogurt-based one on the nutritional management of PD. A total of 154 male infants, aged between 1 and 30 months, with PD and with or without dehydration, were randomly assigned to 1 of 4 treatment groups. Throughout the study, the patients were placed in a metabolic unit; their body weights and intakes of oral rehydration solution, water, and formula diets, in addition to outputs of stool, urine, and vomit, were measured and recorded at 24-hour intervals. Four different diets were used in this study: diet 1, yogurt-based formula; diet 2, soy-based formula; diet 3, hydrolyzed protein-based formula; and diet 4, amino acid–based formula. Throughout the study, only these formula diets were fed to the children. The data showed that children fed the yogurt-based diet (diet 1) or the amino acid–based diet (diet 4) had a significant reduction in stool output and in the duration of diarrhea. The use of an inexpensive and worldwide-available yogurt-based diet is recommended as the first choice for the nutritional management of mild to moderate PD. For the few complicated PD cases, when available, a more complex amino acid–based diet should be reserved for the nutritional management of these unresponsive and severe presentations. Soy-based or casein-based diets do not offer any specific advantage or benefits and do not seem to have a place in the management of PD.  相似文献   
72.
Background  Nonmelanoma skin cancer (NMSC) has been linked to cutaneous human papillomaviruses of the genus beta (betaPV).
Objectives  We sought to assess the presence of betaPV in NMSC biopsies from a group of Scottish skin cancer patients, both immunocompetent (IC) patients and immunosuppressed (IS) organ transplant recipients.
Methods  One hundred and twenty-one paraffin-embedded skin tumours (27 actinic keratosis, 41 intraepidermal carcinoma, 53 squamous cell carcinoma) and 11 normal skin samples were analysed for the presence of betaPV by a polymerase chain reaction–reverse hybridization assay designed to detect the presence of the 25 known betaPV genotypes.
Results  In IC patients, betaPV was detected in 30 of 59 (51%) tumours and two of 11 (18%) normal skin samples ( P  =   0·046). In IS patients, betaPV was found in 27 of 62 (44%) tumours; no normal skin samples were available for comparison. The most frequently found genotypes were HPV-24, HPV-15 and HPV-38. Of those tumours infected with betaPV, 28 of 57 (49%) were infected with more than one genotype (range 2–8). Tumours from IS patients were from a younger age group (mean age 57·4 years) than IC patients (mean age 73·8 years). Multiple infections were more common in tumours from IC patients (21 of 30; 70%) compared with those from IS patients (seven of 27; 26%) ( P  <   0·001). In the IC group, age did not appear to influence the distribution of single and multiple infections whereas in IS patients the proportion of multiple infections to single infections increased with age. There were no multiple infections in normal skin.
Conclusions  A wide spectrum of betaPV types was detected in our samples. Further characterization of betaPV in vivo is needed in order to determine the mechanisms by which the virus contributes to cutaneous carcinogenesis.  相似文献   
73.
74.
The goal of this longitudinal study was to investigate the precursors of early reading development in 52 children with cerebral palsy at kindergarten level in comparison to 65 children without disabilities. Word Decoding was measured to investigate early reading skills, while Phonological Awareness, Phonological Short-term Memory (STM), Speech Perception, Speech Production and Nonverbal Reasoning were considered reading precursors. Children with cerebral palsy lag behind on all reading precursors at the beginning of the second year of kindergarten. For the children without disabilities, early reading skills in Grade 1 were best predicted by Phonological Awareness and Phonological STM while Speech Production was the most important predictor of early reading success for the children with cerebral palsy, followed by Phonological Awareness and Speech Perception. Furthermore, for children with cerebral palsy, Speech Production appears to dominate reading development, as Speech Production measured at the beginning of the second year of kindergarten was strongly predictive of all other reading precursors measured at the end of the second year of kindergarten. The results of this study reveal that children with cerebral palsy with additional speech impairments are at risk for limited literacy development. Clinical implications are discussed.  相似文献   
75.

Background  

Pneumococcal diseases remain a major cause of morbidity and mortality worldwide. Updated data on drug-resistance from different populations may be important to recognize changes in disease patterns. This study assessed current levels of penicilin resistance among Streptococcus Pneumoniae causing pneumonia in Spanish middle age and older adults.  相似文献   
76.
77.
78.
We review the association between surgically resolvable aortic disease and horseshoe kidney with a discussion of diagnostic problems and therapeutic options.Male patient 81 years of age with horseshoe kidney and an abdominal aortic aneurysm that was discovered by chance in an abdominal ultrasound during a check-up for his prostate condition.A retroperitoneal approach was used in order to resect the aneurysm and perform an aorto-aortic bypass with no complications occurring. Two years after the diagnosis, the patient is still asymptomatic from a vascular point of view.The co-presence of horseshoe kidney and aortic disease needing surgical correction is infrequent, but it significantly increases the technical complexity of aortic reconstruction. A literature review is included.  相似文献   
79.
Immigrants, and especially those recently arrived in host countries, are a high-risk group for tuberculosis. In 2006 in France, nearly half of the new cases of tuberculosis were reported in this group. The incidence rate among people born abroad was about seven times higher than that observed in people born in France (38.9/105 vs 5.2/105). The incidence was also the highest in districts with a high proportion of socioeconomically vulnerable population, such as Paris and greater Paris area. The characteristics of French born and non-French born cases differed. Patients born abroad were less likely to have pulmonary tuberculosis (68.2% vs 78.2; p < 0.001) and were more likely to live in institutions (such as migrant shelters) and to harbor multiresistant tuberculosis strains. A national tuberculosis control program was launched in France in 2007, to decrease the prevalence of tuberculosis in targeted populations.  相似文献   
80.
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