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   908篇
  免费   33篇
  国内免费   66篇
耳鼻咽喉   2篇
儿科学   56篇
妇产科学   11篇
基础医学   72篇
口腔科学   40篇
临床医学   136篇
内科学   210篇
皮肤病学   23篇
神经病学   11篇
特种医学   247篇
外科学   59篇
综合类   30篇
预防医学   22篇
眼科学   14篇
药学   36篇
中国医学   1篇
肿瘤学   37篇
  2021年   6篇
  2020年   2篇
  2019年   2篇
  2018年   3篇
  2017年   5篇
  2016年   5篇
  2015年   14篇
  2014年   13篇
  2013年   21篇
  2012年   11篇
  2011年   9篇
  2010年   29篇
  2009年   41篇
  2008年   14篇
  2007年   58篇
  2006年   21篇
  2005年   24篇
  2004年   18篇
  2003年   7篇
  2002年   14篇
  2001年   14篇
  2000年   12篇
  1999年   14篇
  1998年   60篇
  1997年   70篇
  1996年   70篇
  1995年   59篇
  1994年   42篇
  1993年   49篇
  1992年   8篇
  1991年   15篇
  1990年   13篇
  1989年   41篇
  1988年   22篇
  1987年   36篇
  1986年   12篇
  1985年   25篇
  1984年   15篇
  1983年   23篇
  1982年   19篇
  1981年   17篇
  1980年   21篇
  1979年   2篇
  1978年   5篇
  1977年   9篇
  1976年   4篇
  1975年   6篇
  1966年   2篇
  1948年   1篇
  1947年   1篇
排序方式: 共有1007条查询结果,搜索用时 0 毫秒
41.
42.
This is the first controlled study of the frequency of backpain in a European caucasian population with diffuse idiopathicskeletal hyperostosis (DISH). Elderly patients admitted to hospital for reasons other thanback pain were assessed for the presence of spinal DISH usingthe routine lateral chest radiograph films. A total of 106 probands(82 males, 24 females) with a mean age of 70 years fulfilledthe criteria for DISH as defined previously. One hundred andseventyeight patients (117 males, 61 females) not meeting thesecriteria were used as controls. The prevalence of back painwas assessed by a blinded interviewer using a structured questionnaire.Our primary hymthesis was that spinal DISH positive probandshad not had back pain more often than controls. The controlledstudy showed no statistically significant difference in painfrequency between spinal DISH positive probands and controlsat any spinal level. We conclude that back pain does not occur more often in radiographicallydefined DISH positive probands than in controls. The radiologicalfinding of spinal DISH, as far as it does not lead to stenosisof the spinal canal or dysphagia, thus seems to be a findingwithout clinical relevance. KEY WORDS: Spine, Radiographs, Pain, Osteoarthritis, Forestier's disease, Ankylosing vertebral hyperostosis  相似文献   
43.
目的:观察差速贴壁技术对星形胶质细胞纯化率的影响,旨在建立一套可靠的大鼠脑皮质星形胶质细胞的取材分离、纯化培养技术。方法:实验于2006-06/08在泰山医学院生命科学研究所完成。实验材料:出生2~3d的Wistar大鼠,雌雄不拘,由泰山医学院生命科学研究所实验动物中心提供。实验方法:选用出生二三天的Wistar大鼠进行脑皮质星形胶质细胞原代培养。实验分两组培养:常规培养组和差速贴壁培养组。差速贴壁培养组分别于15,30min取出,轻轻翻转培养瓶,将上清液移至另一培养瓶中,放入培养箱中继续培养。7~10d后传代,待细胞分层生长后,置于37℃摇床中250r/min振荡18h,倒掉上清液,D-Hank’s液洗3次后,加入0.25%胰酶消化,倒置显微镜下观察,待细胞突起回缩后加入含血清的培养基终止消化,用吸管反复吹打使细胞从瓶壁上脱落,细胞悬液1000r/min离心5min后,弃上清液,加入含体积分数为0.2血清的DMEM培养基混悬沉淀,接种入预先涂有L-多聚赖氨酸的培养瓶中继续培养。采用双重免疫荧光法鉴定星形胶质细胞纯度,测定积分吸光度值判断星形胶质细胞的生长状况。结果:①应用差速贴壁技术培养星形胶质细胞可明显提高星形胶质细胞纯度[常规培养组:(82±3)%,差速贴壁培养组15min:(94±2)%,差速贴壁培养组30min:(95±2)%,P<0.01]。差速贴壁需要充分的时间,15min组和30min组在提高星形胶质细胞纯度方面无明显差别。②差速贴壁培养组星形胶质细胞积分吸光度值高于常规培养组(常规培养组:528±25,差速贴壁培养组15min:972±17,差速贴壁培养组30min:996±35,P<0.05)。结论:①差速贴壁技术可明显提高星形胶质细胞纯化度,并且星形胶质细胞生长状态明显优于常规培养方法。②最佳差速贴壁时间为15min,过长差速贴壁时间对提高星形胶质细胞纯度无明显影响。  相似文献   
44.
In-vitro fertilization patients (n = 15) at risk of ovarian hyperstimulation syndrome (OHSS) (oestradiol > or =4500 pg/ml on the day of human chorionic gonadotrophin administration and 25 or more follicles of intermediate or large size) underwent aspiration of all follicles and cryopreservation of all fertilized oocytes at the pronuclear stage. Patients were monitored for up to 2 weeks post- retrieval. Subsequent transfer of cryopreserved-thawed embryos was performed in programmed cycles using exogenous oestrogen and progesterone for endometrial preparation. Two patients (13%) developed OHSS necessitating hospitalization and vaginal aspiration of ascitic fluid. Two other patients (13%) developed moderate OHSS requiring ascitic fluid vaginal aspiration in the office setting, with dramatic improvement of the condition. Subsequent transfer of cryopreserved- thawed embryos yielded a clinical pregnancy rate of 58% per transfer and ongoing or delivery rates of 42 and 67% per transfer and per patient respectively. By eliminating pregnancy potential with cryopreservation of all prezygotes and examining the pregnancy potential with subsequent cryopreserved-thawed transfers, it is concluded that OHSS is reduced, but not eliminated for patients at risk. Subsequent transfer of cryopreserved-thawed prezygotes in a programmed cycle with exogenous steroids yields an excellent pregnancy rate.   相似文献   
45.
Diabetic ketoacidosis (DKA) is a true pediatric and medical emergency. Diagnosis should be entertained and confirmed within 30 min of presentation. Any delay in making the diagnosis or instituting fluid and electrolyte correction is likely to increase morbidity and mortality. Slow and careful monitoring and correction of water, sodium and potassium levels should decrease DKA-associated problems with either continuous intravenous low-dose insulin or intramuscular insulin protocols designed to slowly bring the hyperglycemic and hyperosmotic state towards normal homeostasis. Special attention should be paid to potassium replenishment. Most patients do not require bicarbonate replacement. Cerebral edema, when it occurs, is associated with an approximately 50% morbidity and mortality; therefore, all attempts should be made at early recognition and prevention since treatment is less than ideal. Recurrent ketoacidosis is often related to omitted insulin and major psychosocial turmoil in the family, such as depression substance abuse, physical and/or sexual abuse. Prevention of recurrent DKA remains a major challenge for diabetologists and involves detailed assessment of family psychodynamics plus responsibility for home monitoring and insulin administration by a mature adult. Sick day guidelines should be taught and reviewed frequently in an effort to decrease ketoacidosis and metabolic decompensation during episodes of intercurrent illness. □ Cerebral edema, diabetic ketoacidosis, diabetes mellitus, DKA, sick day guidelines, sick day management, type 1 diabetes mellitus  相似文献   
46.
OBJECTIVE: To determine if sexually transmitted diseases (STDs), including human immunodeficiency virus (HIV) infection, risk assessment, and education tools provided as part of office-based primary care reduce adolescent risky sexual behaviors. DESIGN: A randomized intervention trial with 3- and 9-month follow-up. SETTING: Five staff-model managed care sites in Washington, DC (n = 19 pediatricians). PATIENTS: Consecutive 12- to 15-year-olds receiving a general health examination; 81% minority. Participation rate = 215/432 (50%). Nine-month follow-up rate = 197/215 (92%). INTERVENTION: Audiotaped STD risk assessment and education about staying safe (safer = condoms, safest = abstinence). MAIN OUTCOME MEASURES: Adolescent-reported sexual intercourse and condom use. RESULTS: More intervention adolescents reported pediatrician discussion on 11/13 sexual topics. Although more vaginal intercourse (odds ratio [OR] = 2.46, 95% confidence interval [CI] = 1.04-5.84) was reported in the intervention group at 3 months, this was not true of overall sexual intercourse (OR = 1.55, 95% CI =.73-3.32). More sexually active adolescents reported condom use in the intervention group at 3 months (OR = 18.05, 95% CI = 1.27-256.03). At 9 months, there were no group differences in sexual behaviors; however, more signs of STD were reported by the control (7/103) than the intervention group (0/94). CONCLUSIONS: STD risk assessment and education tools administered in a single office visit facilitated STD/HIV prevention education. Any impact on sexual activity and condom use was short-lived. Further research is needed to develop brief, office-based sexual risk reduction for young adolescents.  相似文献   
47.
Friedreich ataxia is a progressive neurodegenerative disorder caused by loss of function mutations in the frataxin gene. In order to unravel frataxin function we developed monoclonal antibodies raised against different regions of the protein. These antibodies detect a processed 18 kDa protein in various human and mouse tissues and cell lines that is severely reduced in Friedreich ataxia patients. By immunocytofluorescence and immunocytoelectron microscopy we show that frataxin is located in mitochondria, associated with the mitochondrial membranes and crests. Analysis of cellular localization of various truncated forms of frataxin expressed in cultured cells and evidence of removal of an N-terminal epitope during protein maturation demonstrated that the mitochondrial targetting sequence is encoded by the first 20 amino acids. Given the shared clinical features between Friedreich ataxia, vitamin E deficiency and some mitochondriopathies, our data suggest that a reduction in frataxin results in oxidative damage.   相似文献   
48.
Lung carcinoids occur sporadically and rarely in association with multiple endocrine neoplasia type 1 (MEN1). There are no well defined genetic abnormalities known to occur in these tumors. We studied 11 sporadic lung carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene were inactivated. All four tumors showed the presence of a MEN1 gene mutation and loss of the other allele. Observed mutations included a 1 bp insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide substitution affecting a donor splice site. Each mutation predicts truncation or potentially complete loss of menin. The remaining seven tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH. The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a complex germline MEN1 gene mutation. The data implicate the MEN1 gene in the pathogenesis of sporadic lung carcinoids, representing the first defined genetic alteration in these tumors.   相似文献   
49.
50.
Nasopharyngeal carriage of Haemophilus influenzae and Streptococcus pneumoniae was studied in 621 healthy Chinese children and 300 healthy Vietnamese children aged from 2 months to 5 years in Hong Kong. The carriage rate of H, influenzae type b in Vietnamese children was 1.3% (CI 0.04-2.63%); it was zero in Chinese. The carriage rate of non-typable H. influenzae was 5.8% (CI 1.4-7.6%) in Chinese and 65.4% (CI 58.9-69.8%) in Vietnamese. The carriage rates of S. pneumoniae were 10.8% (CI 8.3-13.2%) and 55.7% (CI 50.1-61.3%) in Chinese and Vietnamese children, respectively. Univariate and multivariate logistic regression analyses were performed to search for factors associated with differences in carriage rates of both H. influenzae and S. pneumoniae between Chinese and Vietnamese children. Although older age, smaller living area and parental smoking were associated with higher carriage rates, these could not explain the remarkably low carriage rates of both bacteria in Chinese children.  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