首页 | 官方网站   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   10486篇
  免费   1068篇
  国内免费   15篇
医药卫生   11569篇
  2023年   133篇
  2022年   92篇
  2021年   445篇
  2020年   284篇
  2019年   386篇
  2018年   415篇
  2017年   313篇
  2016年   348篇
  2015年   371篇
  2014年   428篇
  2013年   555篇
  2012年   848篇
  2011年   867篇
  2010年   453篇
  2009年   351篇
  2008年   550篇
  2007年   618篇
  2006年   529篇
  2005年   568篇
  2004年   514篇
  2003年   402篇
  2002年   447篇
  2001年   95篇
  2000年   96篇
  1999年   99篇
  1998年   87篇
  1997年   54篇
  1996年   70篇
  1995年   54篇
  1994年   47篇
  1993年   58篇
  1992年   69篇
  1991年   67篇
  1990年   53篇
  1989年   45篇
  1988年   38篇
  1987年   57篇
  1986年   62篇
  1985年   57篇
  1984年   40篇
  1983年   44篇
  1982年   38篇
  1981年   25篇
  1980年   26篇
  1979年   34篇
  1978年   19篇
  1977年   18篇
  1975年   17篇
  1974年   21篇
  1972年   17篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
62.
For years it has been recognised that many sports place demands on vision and particular visual skills. There is much evidence to show that the correction of visual dysfunction such as ametropia and binocular and accommodative anomalies results in improved sporting performance for those sports. More controversial and of special interest is the suggestion that it is possible to train visual abilities of subjects who do not present with traditionally recognised functional disorders of vision. It has been proposed that sporting performance can be improved as a result of this training. However, this review found the evidence to be inconclusive. In addition, there are studies that suggest athletes have better visual abilities than non-athletes and good athletes have better abilities than less skilled athletes. However, it has not been determined whether these superior abilities are innate to the athlete or have developed through practice. A review of the available literature was unable to prove (or disprove) either of these proposals. However, there appears to be enough evidence to warrant further investigation of these questions, in order that the area of sports vision and vision training can be more fully understood. This will enable clinicians to take full advantage of the potential of sports vision practice to assist athletes. (Clin Exp Optom 1995; 78: 3: 98–105)  相似文献   
63.
64.
Physiologic measurements in nonhuman primates usually are collected from animals that are chemically or physically restrained. Both types of restraint may affect the parameters measured, and those effects can vary with age. Heart rate, respiratory rate, oxygen saturation, expired CO2, blood pressure, temperature, blood glucose, hematocrit, and venous blood gasses were measured in rhesus monkeys that were either infused intravenously with ketamine for 24 h or were cage-housed and physically restrained for sample collection. The subjects were pregnant monkeys at gestational day 120 to 123, infants 5 to 6 d old, and infants 35 to 37 d old. Heart rate and blood pressure were lower in ketamine-treated monkeys than physically restrained monkeys. Heart rate was higher in infants than adults, whereas blood pressure was lower in infants. Respiratory rate was higher in infants than adults and higher in physically restrained infants than ketamine-sedated infants but was not affected by ketamine in pregnant adults. Hematocrit was decreased in older infants. In summary, both physical restraint and ketamine sedation altered several physiologic parameters in pregnant and infant rhesus macaques. Investigators should consider these effects when designing experiments and evaluating experimental outcomes in monkeys.  相似文献   
65.
66.
67.
Human trophoblast implantation is a highly regulated process of invasion that requires action of proteolytic enzymes to degrade extracellular matrix components of the endometrium. Among these enzymes, matrix metalloproteinases (MMPs) seem to be particularly important in this degradative process. We previously showed that gelatinase A is extensively expressed in vivo in the human placenta. A new MMP, MT-NINIP-1 (membrane-type matrix metalloproteinase-1), which is thought to activate progelatinase A, has recently been described. In this study, we examined the expression of NIT-NIMP-1, by immunohistochemistry and in situ hybridization, in human placental bed biopsies taken during the first trimester of gestation. Human first trimester intermediate trophoblasts synthesized MT-MMP-1 mRNAs and the protein. The MT-MMP-1 pattern of distribution in placental beds was similar to that of gelatinase A, suggesting a pivotal role for MT-MMP-1 in placentation, perhaps by activating progelatinase A.  相似文献   
68.
Intranasal immunization of mice with Rib, a cell surface protein of group B streptococcus (GBS), conjugated to or simply coadministered with the recombinant cholera toxin B subunit, induces systemic immunoglobulin G (IgG) and local IgA antibody responses and confers protection against lethal GBS infection. These findings have implications for the development of a human GBS vaccine.  相似文献   
69.
Cardiac myxomas are the most frequent cardiac tumors and cause for significant morbidity and mortality. Recent evidence indicates that cardiac myxomas are, in fact, neoplasms rather than organized thrombi. Cardiac myxomas may present as solitary lesions or in association with the Carney complex. Carney complex has been linked to chromosome 2p16 and the PRKAR1A gene at 17q22-24. In this study, we analyzed sporadic cardiac myxomas to evaluate whether the genetic alterations seen in Carney complex are present in non Carney complex associated cardiac myxomas as well. We analyzed microdissected material from 13 patients with cardiac myxomas for the markers PRKAR1 9CA, D2S2153, D2S2251 and D2S123. None of the cases demonstrated loss of heterozygosity or definite band changes suggestive of microsatellite instability for any of the markers used. We conclude that sporadic cardiac myxomas are genetically not related to Carney complex and most likely do not represent an incomplete form of Carney complex.  相似文献   
70.
Legionella gormanii sp. nov   总被引:15,自引:18,他引:15       下载免费PDF全文
A new species of Legionella was isolated from soil collected from a creek bank. The name Legionella gormanii sp. nov. is proposed.  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-23

京公网安备 11010802026262号