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   18026篇
  免费   1740篇
  国内免费   21篇
耳鼻咽喉   239篇
儿科学   529篇
妇产科学   391篇
基础医学   2200篇
口腔科学   348篇
临床医学   2404篇
内科学   3452篇
皮肤病学   203篇
神经病学   1389篇
特种医学   714篇
外国民族医学   3篇
外科学   2435篇
综合类   468篇
一般理论   9篇
预防医学   1977篇
眼科学   595篇
药学   1488篇
中国医学   13篇
肿瘤学   930篇
  2021年   313篇
  2020年   205篇
  2019年   290篇
  2018年   321篇
  2017年   204篇
  2016年   282篇
  2015年   299篇
  2014年   401篇
  2013年   571篇
  2012年   797篇
  2011年   864篇
  2010年   472篇
  2009年   399篇
  2008年   728篇
  2007年   821篇
  2006年   842篇
  2005年   773篇
  2004年   762篇
  2003年   697篇
  2002年   651篇
  2001年   568篇
  2000年   602篇
  1999年   527篇
  1998年   211篇
  1997年   188篇
  1996年   188篇
  1995年   185篇
  1994年   162篇
  1993年   149篇
  1992年   408篇
  1991年   413篇
  1990年   381篇
  1989年   397篇
  1988年   344篇
  1987年   328篇
  1986年   329篇
  1985年   314篇
  1984年   262篇
  1983年   223篇
  1982年   150篇
  1981年   118篇
  1979年   193篇
  1978年   167篇
  1977年   141篇
  1976年   128篇
  1974年   160篇
  1973年   144篇
  1972年   129篇
  1971年   116篇
  1969年   111篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
AIM: To examine in vitro the effects of brief contact with various infusion solutions on red blood cells from newborn infants, as occurs in the "waste" syringe during routine blood sampling from umbilical artery catheters. The mixture of blood and solution in the "waste" syringe is usually reinfused into the baby. Reinfused red blood cells may be damaged by the infusion solution. It is hypothesised that an isotonic amino acid solution would cause no red blood cell agglutination and no more haemolysis than many commonly used solutions. METHODS: Blood was obtained from the placentas of 15 normal term babies. Haemolysis was estimated by measuring plasma (free) haemoglobin after mock blood sampling. Agglutination was measured semiquantitatively by direct observation. RESULTS: A 0.25% normal saline solution caused 5.4% haemolysis, significantly more than all the other fluids tested. There was less haemolysis with 0. 25% normal saline when there was complete mixing of blood and solution within the "waste" syringe. Normal saline and isotonic sodium acetate solutions caused < 0.1% haemolysis, significantly less than all the other fluids tested. The isotonic amino acid solution caused 0.8% haemolysis, which is similar to that caused by the remaining solutions tested. Agglutination was seen with isotonic dextrose and with the two isotonic amino acid solutions containing cysteine. CONCLUSIONS: Isotonic amino acid solution (without added cysteine) caused no agglutination and the same or less haemolysis than many commonly used solutions and may offer advantages in nutrition and fluid balance.  相似文献   
992.
Spontaneous bone healing in the rabbit   总被引:2,自引:0,他引:2  
Cranioplasty is the most common method for correcting cranial defects. A number of innovations have been made to optimize bone repair. Before their use in humans, extensive animal trials must be performed to establish efficacy. However, the literature provides only scant and inconsistent data regarding animal controls. The purpose of this study, therefore, was to determine the critical size cranial defect in the rabbit model. Cranial defects ranging from 0.5 to 1.5 cm were created in 18 New Zealand White rabbits. The rabbits were then killed at 9 and 18 weeks and the defects examined using CT imaging and histologic analysis to determine bone healing. It was determined that cranial defects greater than 1.5 cm failed to heal spontaneously. Thus, the critical size cranial defect in the rabbit model is 1.5 cm.  相似文献   
993.
OBJECTIVE: To examine upper-extremity motor recovery of subjects with tetraplegia with both complete and incomplete injuries, to predict which patients and at what time they would recover a motor level. DESIGN: Prospective, multicenter clinical study of upper-extremity motor recovery in subjects with acute traumatic spinal cord injury. SETTING: Three regional spinal cord injury centers. SUBJECTS: One hundred sixty-seven individuals with acute traumatic tetraplegia (144 males [86%], and 23 females [14%]) between the ages of 15 and 75 years (mean age, 35.5 yrs). METHODS: Subjects were examined and classified using sequential manual muscle tests performed on admission, 72 hours, 1, 2, and 3 weeks, and 1, 2, 3, 6, 12, 18, and 24 months postinjury. C5 biceps, C6 extensor carpi radialis, C7 triceps, and C8 flexor digitorum profundus were evaluated using a 0-5 scale. Analyses of the right motor levels used a series of logistic regression models, and for multiple measurements on each subject, models were estimated using generalized estimating equations. RESULTS: The analysis for recovery of the biceps for the C4 group showed 70% of complete compared with 90% of incomplete injuries recovered (p < .001); of the extensor carpi radialis in the C5 group, 75% complete and 90% incomplete recovered (p < .002); and of the triceps in the C6 group, 85% of complete and 90% of incomplete injuries recovered (p < .16). CONCLUSION: Predicting future potential for upper-extremity motor recovery and for independence in self-care in groups of patients at a specific motor level is possible within the first week of injury.  相似文献   
994.
995.
S-Methylation by thiopurine methyltransferase (TPMT) is an important route of metabolism for the thiopurine drugs. About one in 300 individuals are homozygous for a TPMT mutation associated with very low enzyme activity and severe myelosuppression if treated with standard doses of drug. To validate the use of molecular genetic techniques for the detection of TPMT deficiency, we have determined red blood cell TPMT activity in 240 adult blood donors and 55 normal children. Genotype was determined by restriction fragment length analysis of polymerase chain reaction products in a cohort of 79 of the blood donors and five cases of azathioprine-induced myelosupression, and this confirmed a close relationship between genotype and phenotype. In 17 of the 24 cases in which mutations were found, DNA was also available from remission bone marrow. In one of these cases, DNA from the remission marrow sample indicated the presence of a non-mutated allele that had not been seen in the blast DNA sample obtained at presentation. These results indicate that polymerase chain reaction-based assays give reliable and robust results for the detection of TPMT deficiency, but that caution should be exercised in relying exclusively on DNA obtained from lymphoblasts in childhood leukaemia.  相似文献   
996.

Background  

Primary care internationally is approaching a new paradigm. The change agenda implicit in this threatens to de-stabilise and challenge established general practice and primary care.  相似文献   
997.

Background  

The workplace is an ideal setting for health promotion. Helping employees to be more physically active can not only improve their physical and mental health, but can also have economic benefits such as reduced sickness absence. The current paper describes the development of a three month theory-based intervention that aims to increase levels of moderate intensity physical activity amongst employees in sedentary occupations.  相似文献   
998.
This study examines the correlates of marital satisfaction using data from a national probability sample of African Americans (N = 962) and Black Caribbeans (N = 560). Findings reveal differences between African Americans and Black Caribbeans, and men and women within those groups, in the predictors of marital satisfaction. Black Caribbean women reported overall higher levels of marital satisfaction than African American women. The findings amply demonstrate the significance of ethnic diversity within the Black population in the United States. Difficulties with finances (budgeting, credit issues, and debt management) are one of the key issues that generate conflict in marriages; stress generated as a result of financial problems can lower marital satisfaction. Because these issues are salient for couples at any given time in the family life cycle, counseling at critical points in the marriage (birth of children, launching of children from home, and retirement) may be helpful.  相似文献   
999.
Alkaloids in Sophora alopecuroides seed and relevant tests for activity]   总被引:2,自引:1,他引:2  
Seven alkaloids were isolated from the seed of Sophora alopecuroides and identified to be oxymatrin, oxysophocarpine, cytisine, matrine, sophocarpine, sophoridine and nicotine respectively by comparing chromactographic and spectral characteristics with authentic known compounds. Nicotine was isolated from Sophora for the first time. The activity of extracts and alkaloids against cancer, virus, dermatophytes and bacteria was carried out in vitro.  相似文献   
1000.
The validity of self-reported fruit and vegetable intake in minority populations has not been adequately established. In this study, the authors examined the association of three food frequency questionnaires (FFQs) and 24-hour dietary recalls with serum carotenoid levels. Approximately 1,000 African-American adults recruited from 15 churches in Atlanta, Georgia (1997-1998) completed three fruit and vegetable FFQs: a seven-item instrument assessing intake during the past month; a two-item measure assessing usual intake; and a 36-item measure adapted from the Health Habits and History Questionnaire. A total of 414 participants received a 24-hour recall by telephone, and 105 of them received two additional recalls. Serum levels of lycopene, lutein, cryptoxanthin, alpha-carotene, and beta-carotene were assessed in 813 participants and used as the validity criterion. The correlations of fruit and vegetable servings with specific and total serum carotenoid levels were generally higher for the 36-item FFQ than for the two-item and seven-item instruments. The strongest correlation of fruit and vegetable servings with total carotenoid levels was observed for the three recalls (r = 0.42), with the 36-item FFQ and the single 24-hour recall yielding comparable correlations (r = 0.35 and r = 0.37, respectively). The validity of the 36-item fruit and vegetable FFQ was generally as strong as the validity of both 1 and 3 days of recalls. Given the lower cost and time needed for administration relative to recalls, it appears that the 36-item FFQ has merit for evaluating fruit and vegetable health interventions.  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