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   1656篇
  免费   171篇
  国内免费   12篇
耳鼻咽喉   17篇
儿科学   36篇
妇产科学   86篇
基础医学   215篇
口腔科学   44篇
临床医学   232篇
内科学   378篇
皮肤病学   30篇
神经病学   159篇
特种医学   55篇
外科学   223篇
综合类   52篇
一般理论   3篇
预防医学   93篇
眼科学   19篇
药学   145篇
肿瘤学   52篇
  2023年   15篇
  2022年   16篇
  2021年   33篇
  2020年   24篇
  2019年   33篇
  2018年   33篇
  2017年   21篇
  2016年   32篇
  2015年   34篇
  2014年   38篇
  2013年   54篇
  2012年   57篇
  2011年   75篇
  2010年   32篇
  2009年   40篇
  2008年   63篇
  2007年   54篇
  2006年   68篇
  2005年   62篇
  2004年   67篇
  2003年   66篇
  2002年   54篇
  2001年   51篇
  2000年   74篇
  1999年   51篇
  1998年   24篇
  1996年   16篇
  1994年   24篇
  1993年   16篇
  1992年   28篇
  1991年   44篇
  1990年   37篇
  1989年   31篇
  1988年   33篇
  1987年   34篇
  1986年   36篇
  1985年   38篇
  1984年   15篇
  1983年   29篇
  1980年   13篇
  1979年   15篇
  1978年   21篇
  1976年   18篇
  1975年   11篇
  1974年   24篇
  1973年   23篇
  1972年   13篇
  1971年   15篇
  1969年   13篇
  1966年   12篇
排序方式: 共有1839条查询结果,搜索用时 0 毫秒
71.
Twenty-six severely isoimmunized pregnancies managed exclusively with ultrasonographically guided intravascular fetal transfusions are reported. The mean gestational age plus and minus one standard deviation (+/- SD) was 26.3 +/- 3.6 weeks and the mean hematocrit (+/- SD) prior to initial transfusion was 20.6 +/- 6.7%. Four of seven hydropic fetuses and 9 of 19 without hydrops were less than or equal to 26 weeks gestation at the first transfusion. Overall survival was 85% (22/26). Survival was similar whether or not fetal hydrops was present (6/7 vs. 16/19) and whether or not the first transfusion was administered at less than or equal to 26 weeks gestation (10/13 vs. 12/13).  相似文献   
72.
In 458 consecutive chorionic villus sampling (CVS) procedures, we observed a significant influence of uterine position upon sampling efficacy. Compared with anteverted (N = 243) or axial (N = 149) locations, the retroverted uterus (N = 66) was associated with a lower mean sample weight per aspiration (22, 18, and 15 mg, respectively; P less than .01) and a greater frequency of multiple-pass procedures (23, 31, and 52%, respectively; P less than .0001). To improve sampling efficiency in selected cases of uterine retroversion, we adopted a transvesical approach. When compared with transabdominal or transcervical techniques, transvesical CVS had the highest single-pass success rate (33, 33, and 60%, respectively). Only one in 30 transvesical cases required three placental passes, compared with nine of 36 retroverted uteri sampled by either transabdominal or transcervical techniques (P less than .05). The mean transvesical sample weight was 18.7 mg; at least 10 mg was retrieved in all cases. Post-procedure bleeding occurred in four instances and an additional patient suffered a spontaneous loss at 16 weeks' gestation. Aneuploidy was found in four of 30 biopsy specimens, and the remaining pregnancies either have delivered at term (N = 18) or are continuing (N = 7). Our preliminary experience suggests that selected use of this CVS method may improve sampling efficiency without increasing the incidence of complications.  相似文献   
73.
Human immunodeficiency virus infection in pregnancy   总被引:1,自引:0,他引:1  
Many aspects of HIV infection in pregnancy remain unclear. Subsets at increased risk for perinatal transmission, adverse pregnancy outcome, and development of symptomatic HIV infection need to be identified. For instance, relative risks may be quite different in asymptomatic HIV infected patients with T4 lymphocyte counts greater than 200 cells per cubic millimeter compared to those with either symptoms of HIV infection or T4 cell counts less than 200 cells per cubic millimeter. At present, antiviral therapeutic trials do not include pregnant women or neonates less than 3 months of age. In the future, antiviral therapy with agents, such as AZT, may reduce the risk of transplacental and intrapartum HIV transmission. Obstetricians will be involved increasingly in providing care to HIV-infected patients and educating patients in order to prevent HIV infection.  相似文献   
74.
EDITORIAL COMMENT: We have published this letter in the position of an article to make sure that readers do not overlook it. The letter is signed by a number of specialist medical obstetrician ultmsonologists in Melbourne and they clearly state a different point of view to that expressed by Burrows, Ramsden and Frazer. (Aust NZ J Obstet Gynaecol 1993; 33:262–264).  相似文献   
75.
Sixty-seven women with primary addiction to cocaine were evaluated during their pregnancies by multiple ultrasound studies. Ultrasonic parameters included biparietal diameter, femur length, abdominal circumference, and head circumference. These values were compared with ultrasonic growth parameters in nonaddicted fetuses. Head and abdominal circumference data were used to evaluate the fetuses according to growth pattern. With this system of scoring, subtleties of asymmetric versus symmetric intrauterine growth retardation become apparent. In addition, birth weights of addicted infants were compared with birth weights of nonaddicted infants. The results suggest that, although statistically significant differences in birth weights cannot be demonstrated, abnormal growth of the addicted fetuses does occur. Addicted fetuses show a greater proportion of biparietal diameter and abdominal circumference values below the 50th and 25th percentiles than nonaddicted fetuses, and addicted fetuses more frequently exhibit intrauterine growth retardation patterns. These data suggest that it is fruitful to study these infants with near-normal size but with abnormal intrauterine growth patterns.  相似文献   
76.
An outbreak of viral gastroenteritis caused illness in 92 people during October 2000. All the cases had an association with one hotel and 80% of cases identified had attended one of two buffet meals on 18th October 2000. Cohort analysis did not implicate any particular foodstuff in this outbreak. All bacteriological tests on food samples were negative. Small round structured virus (SRSV)/Norwalk-like virus (NLV) particles were seen by electron microscopy in 6 out of 27 stool samples submitted for analysis. This paper describes the outbreak and in particular the lessons learned from the management and control of it. These include practical points with regard to the outbreak control team, liaison with the microbiology laboratory, handling data, agreeing a case definition, and occupational health issues. All can be applied elsewhere by those responsible for managing outbreaks at a local level.  相似文献   
77.
OBJECTIVES: There is an accumulating body of research related to the psychosomatic study of blood pressure. One variable that has received attention is defense use. We examined the relation between defense use and blood pressure in men and women of different ages. METHODS: A random sample of 667 participants was selected from a population-based study. Resting blood pressure was obtained, and each participant was rated for defense use by a trained observer using Defense-Q. An Adaptive Defense Profile (ADP) score was calculated for each participant, and this score was related to blood pressure. RESULTS: Regression analyses revealed a significant main effect for the ADP score for both diastolic and systolic blood pressure. Those persons with higher ADP scores had lower diastolic and systolic blood pressure. As well, a significant Age x Sex x ADP score interaction was found for diastolic blood pressure. Older women with a less ADP score had higher diastolic blood pressure. CONCLUSIONS: These findings suggest the continued investigation of defense use and blood pressure.  相似文献   
78.
BACKGROUND: The number of proteins with mutations resulting in amyloidosis has continued to increase. Five proteins--transthyretin, fibrinogen alpha-A chain, apolipoprotein AI, lysozyme, apolipoprotein AII, cystatin C and gelsolin--can be associated with hereditary amyloidosis involving the kidney. METHODS: A French family with a history of autosomal dominant hereditary amyloidosis with early sicca syndrome and nephropathy leading to renal failure after the fifth to the seventh decade was studied. Several tissue specimens obtained from the proband and his relatives were examined. Immunohistochemistry was performed on paraffin embedded sections using the indirect immunoperoxidase technique. We searched for mutations in the five exons and flanking introns of the lysozyme gene. RESULTS: Amyloid deposits from the bowel, labial salivary gland and kidney were intensively stained by anti-lysozyme antibody. Sequence analysis of lysozyme exon 2 from the affected individuals revealed a nucleotide substitution predicting a substitution of the amino acid at position 64 in the mature protein from tryptophane, an aromatic residue to the cationic residue arginine (W64R). CONCLUSION: We report a novel mutation (W64R) of the lysozyme that is associated with hereditary amyloidosis and prominent nephropathy. Since the treatment of hereditary amyloidosis greatly varies with the nature of the amyloid protein, thorough characterization of the latter is crucial for the management of the disease.  相似文献   
79.
Hypertensive (n=93) and normotensive (n=39) white individuals were given a high sodium intake of approximately 350 mmol/d for 5 days followed by a low sodium intake of 10 to 20 mmol/d for 5 days. With this acute and large reduction in salt intake, no significant change was seen in blood pressure in the normotensive individuals, but blood pressure decreased in the hypertensive individuals. Compared with normotensive subjects, hypertensive patients had a 7/7-mm Hg greater fall in blood pressure (P<0.05 for systolic and P<0.01 for diastolic, adjusted for age), with similar changes in urinary sodium excretion. From the high-salt to low-salt diet, plasma renin activity rose from 0.90 to 5.99 ng. mL(-1). h(-1) in normotensives, whereas in hypertensives it rose from 0.73 to only 3.14 ng. mL(-1). h(-1) (P<0.05 between hypertensives and normotensives). Plasma aldosterone rose by 1396 pmol/L in normotensive subjects and by 511 pmol/L in hypertensive patients (P<0.05). Significant inverse correlations were obtained for all subjects between the fall in blood pressure from the high-salt to low-salt diet and the rise in plasma renin activity and aldosterone that occurred in addition to the absolute level on the low-salt diet. These results demonstrate that the larger fall in blood pressure with an acute reduction in salt intake in hypertensives compared with normotensives is, at least in part, due to a less-responsive renin-angiotensin-aldosterone system in the hypertensive patients.  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