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   1861篇
  免费   123篇
  国内免费   11篇
耳鼻咽喉   9篇
儿科学   94篇
妇产科学   36篇
基础医学   205篇
口腔科学   116篇
临床医学   213篇
内科学   429篇
皮肤病学   50篇
神经病学   97篇
特种医学   198篇
外科学   154篇
综合类   53篇
预防医学   96篇
眼科学   39篇
药学   80篇
中国医学   1篇
肿瘤学   125篇
  2022年   19篇
  2021年   33篇
  2020年   18篇
  2019年   22篇
  2018年   42篇
  2017年   20篇
  2016年   42篇
  2015年   39篇
  2014年   65篇
  2013年   74篇
  2012年   76篇
  2011年   76篇
  2010年   91篇
  2009年   87篇
  2008年   61篇
  2007年   95篇
  2006年   72篇
  2005年   76篇
  2004年   56篇
  2003年   53篇
  2002年   39篇
  2001年   42篇
  2000年   27篇
  1999年   32篇
  1998年   47篇
  1997年   49篇
  1996年   56篇
  1995年   50篇
  1994年   27篇
  1993年   30篇
  1992年   14篇
  1991年   19篇
  1990年   24篇
  1989年   36篇
  1988年   27篇
  1987年   27篇
  1986年   26篇
  1985年   38篇
  1984年   29篇
  1983年   25篇
  1981年   25篇
  1980年   14篇
  1979年   21篇
  1978年   9篇
  1977年   22篇
  1976年   13篇
  1975年   11篇
  1974年   12篇
  1973年   10篇
  1972年   13篇
排序方式: 共有1995条查询结果,搜索用时 15 毫秒
81.
82.
In the hope of developing a vaccine against Clostridium difficile based on its toxin(s), we have developed a fermentation medium for the bacterium that results in the formation of Toxin A and contains no meat or dairy products, thus obviating the problem of possible prion diseases. Particular preparations of hydrolyzed soy proteins, especially Soy Peptone A3, have been found to replace both the meat/dairy product tryptone in the preparation of working cell banks and seed media, and NZ-Soy BL4 does the same in the fermentation medium. These replacements yield even higher toxin titers.  相似文献   
83.
We evaluated the association of body mass index (BMI) with migraine and migraine specifics in a cross-sectional study of 63 467 women aged ≥ 45 years, of whom 12 613 (19.9%) reported any history of migraine and 9195 had active migraine. Compared with women without migraine and a BMI < 23 kg/m2, women with a BMI ≥ 35 kg/m2 had adjusted odds ratios (ORs) (95% confidence intervals) of 1.03 (0.95, 1.12) for any history of migraine. Findings were similar for active migraineurs. Women with a BMI of ≥ 35 kg/m2 had increased risk for low and high migraine frequency, with the highest estimate for women who reported daily migraine. Compared with women with the lowest associated risk (migraine frequency < 6 times/year; BMI between 27.0 and 29.9 kg/m2), women with a BMI ≥ 35 kg/m2 had an OR of daily migraine of 3.11 (1.12, 8.67). Among the women with active migraine, a BMI ≥ 35 kg/m2 was associated with increased risk of phonophobia and photophobia and decreased risk of a unilateral pain characteristic and migraine aura. Our data confirm previous findings that the association between BMI with migraine is limited to migraine frequency and specific migraine features.  相似文献   
84.
85.
Accurate pregnancy dating is vital to obstetric management. However, first trimester fetal charts commonly used in Australia rely on data reported more than three decades ago. This study reports first trimester dating and growth charts for crown‐rump length between 5 and 14 weeks of gestation and biparietal diameter between 9 and 14 weeks of gestation on an Australia population using modern real‐time ultrasound equipment. All consenting eligible women attending a large Sydney clinic for first trimester ultrasound between March 2005 and December 2006 were recruited. Measurements were carried out to Australasian Society for Ultrasound in Medicine standard protocols. Statistical analyses were undertaken using polynomial regression models and thorough diagnostic checks made. Overall 396 eligible women consented to the study, with 268 between 9 and 14 weeks of gestation. The average participant age was 34 years (range 22–45 years), 371 and all yielded valid biometry measurements. Equations, means and 90% reference intervals for crown‐rump length measurements and biparietal diameter measurements were derived using polynomial regression models. Thorough residual and diagnostic checks were made. Once validated by others, we believe they will warrant consideration for use by Australasian Society for Ultrasound in Medicine.  相似文献   
86.
A cross sectional study assessed the bone mineral density (BMD) of 20 young adult patients who received a renal transplantation in childhood. The BMD of the lumbar spine, mainly trabecular bone, and of the total body, mainly cortical bone, were measured and expressed as an SD score. Fourteen patients (70%) had a BMD SD score of the lumbar spine below -1, of whom six patients were below -2. Fifteen patients (75%) had a BMD SD score of the total body below -1, of whom seven patients were below -2, Both trabecular and cortical bone appeared to be involved in the osteopenic process. The cumulative dose of prednisone was inversely correlated to both lumbar spine and total body BMD SD score. In a multiple regression analysis the cumulative dose of prednisone appeared to be the only factor with a significant effect on BMD SD score. Most young adult patients who had received a renal transplantation in childhood had moderate to severe osteopenia. Corticosteroid treatment played a major part in the development of osteopenia in these patients.  相似文献   
87.
Employee retention is a huge problem. There are staff shortages in radiology because not enough people are entering the profession; too many people are leaving the profession for retirement, higher-paying jobs or jobs with less stress; and there are not enough opportunities for career advancement. Staff shortages are exacerbated by difficulty in retaining people who enter the profession. While much work has been focused on recruitment and getting more people "in the front door," I suggest that the bulk of future efforts be focused on employee retention and "closing the back door." Employee retention must be an ongoing process, not a program. Approaches to employee retention that focus on external things, i.e., things that the company can do to or for the employee, generally are not successful. The truth is that employee retention processes must focus on what the employee gets out of the job. The process must be a benefits-based approach that helps employees answer the question, "What's in it for me?" The retention processes must be ongoing and integrated into the daily culture of the company. The best way to keep your employees is to treat them like customers. Customer service works for external customers. We treat them nicely. We work to satisfy them. We help them achieve their goals. Why not do the same for our employees? If positive customer service policies and practices can satisfy and keep external customers, why not adapt these policies and practices for employees? And, there is a service/satisfaction link between employee retention and higher levels of customer satisfaction. Customers prefer dealing with the same employees over and over again. Employee turnover destroys a customer's confidence in the company. Just like a customer does not want to have to "train and educate" a new provider, they do not want to do the same for your "revolving door" employees. So, the key is to keep employees so they in turn will help you keep your customers. Because the techniques of this process mirror the activities of customer service and customer relationship management, I call the combined process C/ERM for customer/employee relationship management. Both activities must be going on simultaneously to create a loyalty link that ensures customer satisfaction and retention through employee service, satisfaction and retention.  相似文献   
88.
BACKGROUND: Since 1991 the authors have offered a course that identifies content deficits, but only provides instruction directed at improving verbal and nonverbal behaviors. We report the outcome of this 10-year effort as success on the certifying examination of the American Board of Surgery between 1991 and 2001. METHODS: Sixteen 5-day courses were scheduled over 10 years. Participants included those who had not taken the oral examination or had failed at least once and invited senior faculty (n = 26). Sites were chosen to replicate the actual examination setting. RESULTS: There were 122 participants, with follow-up data available on 88. Success in the certifying examination after completing the course is 96 percent. CONCLUSIONS: Evaluation of communication deficits and training to improve them is strongly associated with success. Clearly, this course is effective at identifying communication behaviors that are interfering with success on the certifying examination of the American Board of Surgery.  相似文献   
89.
OBJECTIVE: To clinically characterize affected individuals in families with paroxysmal kinesigenic dyskinesia (PKD), examine the association with infantile convulsions, and confirm linkage to a pericentromeric chromosome 16 locus. BACKGROUND: PKD is characterized by frequent, recurrent attacks of involuntary movement or posturing in response to sudden movement, stress, or excitement. Recently, an autosomal dominant PKD locus on chromosome 16 was identified. METHODS: The authors studied 11 previously unreported families of diverse ethnic background with PKD with or without infantile convulsions and performed linkage analysis with markers spanning the chromosome 16 locus. Detailed clinical questionnaires and interviews were conducted with affected and unaffected family members. RESULTS: Clinical characterization and sampling of 95 individuals in 11 families revealed 44 individuals with paroxysmal dyskinesia, infantile convulsions, or both. Infantile convulsions were surprisingly common, occurring in 9 of 11 families. In only two individuals did generalized seizures occur in later childhood or adulthood. The authors defined a 26-cM region using linkage data in 11 families (maximum lod score 6.63 at theta = 0). Affected individuals in one family showed no evidence for a shared haplotype in this region, implying locus heterogeneity. CONCLUSIONS: Identification and characterization of the PKD/infantile convulsions gene will provide new insight into the pathophysiology of this disorder, which spans the phenotypic spectrum between epilepsy and movement disorder.  相似文献   
90.
The relationship between homovanillic acid (HVA), vanillylmandelic acid (VMA), and creatinine in the urine of 6 month old babies has been studied and reference ranges in the form of centiles constructed for HVA and VMA against creatinine. Over 10,000 urine samples were collected from babies in four health districts in the north of England. HVA and VMA concentration, either independently or when divided by creatinine concentration, were dependent upon the absolute concentration of creatinine in the sample. After adjustment for creatinine significant differences in the mean concentration of HVA were found between sexes. No such differences were found for VMA. HVA and VMA were also found to be age dependent. Centiles were constructed using a procedure which makes no distributional assumptions about the data. The net effect of utilising these centiles was to increase the predictive value of a positive screening test from 20% to 40% without any increase in the false negative rate.  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