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   39400篇
  免费   3117篇
  国内免费   167篇
医药卫生   42684篇
  2023年   219篇
  2022年   411篇
  2021年   800篇
  2020年   498篇
  2019年   791篇
  2018年   905篇
  2017年   703篇
  2016年   722篇
  2015年   854篇
  2014年   1255篇
  2013年   1644篇
  2012年   2347篇
  2011年   2566篇
  2010年   1355篇
  2009年   1187篇
  2008年   2150篇
  2007年   2158篇
  2006年   2068篇
  2005年   1976篇
  2004年   2017篇
  2003年   1843篇
  2002年   1629篇
  2001年   872篇
  2000年   776篇
  1999年   781篇
  1998年   420篇
  1997年   330篇
  1996年   310篇
  1995年   312篇
  1994年   261篇
  1993年   256篇
  1992年   570篇
  1991年   558篇
  1990年   493篇
  1989年   549篇
  1988年   509篇
  1987年   494篇
  1986年   472篇
  1985年   500篇
  1984年   341篇
  1983年   313篇
  1982年   227篇
  1981年   195篇
  1979年   278篇
  1978年   207篇
  1977年   173篇
  1976年   183篇
  1974年   197篇
  1973年   207篇
  1971年   163篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
BACKGROUND/PURPOSE: Sensitive skin is a condition associated with reduced tolerance to environmental factors and/or the application of topical products, such as cosmetics. Its pathophysiology has not been fully elucidated and few data are available on its prevalence. The aim of this study was to investigate possible correlation between objective sensitivity and skin surface microrelief. METHODS: During an epidemiological survey conducted for a campaign promoted by International Society of Plastic Dermatology in Italy, 243 adult healthy subjects of both sexes with no evident dermatological disorder but positive to the lactic acid stinging test, were submitted to cyanoacrylate stratum corneum stripping from the volar forearm for the determination of the irregularity of the skin surface microrelief (irregularity skin index (ISI)). RESULTS: A significant correlation was found between intensity of symptoms in stingers and ISI (r(s)=-0.47; P<0.001). CONCLUSION: Sensitive skin is common in the healthy population. ISI can contribute towards the identification of subjects with sensitive skin and the development of more specific skin treatments for this prevalent condition.  相似文献   
3.
4.
Richard Ila  Michele Solem 《Alcohol》2006,39(3):169-178
Previously, we have demonstrated that chronic-alcohol exposure alters insulin-like growth factor 1 (IGF1) signaling in adult rat heart cells. This report examines the effects of alcohol in vitro on the expression of protein kinase C (PKC) alpha, delta, and epsilon using the embryonic heart cell line, H9c2, and how this may be linked to changes in IGF1 signal transduction. Western blot analyses of H9c2 protein preparations demonstrate that there are significant increases in the total protein levels of PKC delta and epsilon after 4 days exposure to alcohol, and similar increases were found after 2 and 6 days exposure. In addition, there was a significant increase in PKC delta and epsilon in the membranal fractions and a decrease in the cytosolic fractions. No change was found in the expression or activity levels for PKC alpha. Chronic-alcohol exposure (100 mM, 4 days) increased the basal tyrosine kinase activity of the IGF1 receptor (IGF1R), and altered its rate of activation. Chronic-alcohol exposure also reduced the rate of Erk1/Erk2 activation by IGF1. Chronic alcohol blocked the proliferative effects of IGF1 on cell growth and reduced cell viability both in the presence and absence of IGF1, and this alcohol-induced reduction in cell viability was blocked using siRNA to inhibit PKC delta. In addition, a reduction in the amount of myosin light chain 2 was found in the alcohol-exposed cells. In conclusion, chronic alcohol alters PKC delta and epsilon expression and activity, and suppresses the IGF1 signaling pathway in embryonic heart cell culture. Blockage of PKC delta expression using siRNA inhibits the suppressive effects of alcohol on cell viability.  相似文献   
5.
BACKGROUND: The recurrent chronic orofacial swelling caused by orofacial granulomatosis (OFG) can cause significant cosmetic and functional problems but can be prevented if the disease is diagnosed early and promptly treated. Although the enlargement of the lips is described to be the most common presenting complaint, the clinical onset of OFG may be characterized by minor associated mucosal and neurological manifestations, making early diagnosis very difficult or, sometimes, merely presumable. PATIENTS AND METHODS: We retrospectively analyzed the clinical manifestations of 19 patients with OFG, who were examined at our institution between 1998 and 2002, in order to determine their initial manifestations and presenting symptoms. RESULTS: A total of 10 patients showed classical recurrent enlargement of the lips (six lower; four upper) as presenting symptom. In the other nine patients, OFG onset was characterized by transient unilateral facial nerve palsy (two cases), intraoral manifestations (two cases), recurrent swelling of the periorbital area (two cases), of the chin (one case), of the zygomatic area (one case), and of the cheeks (one case). CONCLUSION: Our data underlined that OFG onset could be frequently characterized by widely variable, multiform, and temporary clinical findings. Involvement of atypical sites of the orofacial region and presence of single minor manifestations may occur as presenting symptoms, often preceding the development of traditional clinical findings.  相似文献   
6.
Background: Drugs are routinely combined in anesthesia and pain management to obtain an enhancement of the desired effects. However, a parallel enhancement of the undesired effects might take place as well, resulting in a limited therapeutic usefulness. Therefore, when addressing the question of optimal drug combinations, side effects must be taken into account.

Methods: By extension of a previously published interaction model, the authors propose a method to study drug interactions considering also their side effects. A general outcome parameter identified as patient's well-being is defined by superposition of positive and negative effects. Well-being response surfaces are computed and analyzed for varying drugs pharmacodynamics and interaction types. In particular, the existence of multiple maxima and of optimal drug combinations is investigated for the combination of two drugs.

Results: Both drug pharmacodynamics and interaction type affect the well-being surface and the deriving optimal combinations. The effect of the interaction parameters can be explained in terms of synergy and antagonism and remains unchanged for varying pharmacodynamics. For all simulations performed for the combination of two drugs, the presence of more than one maximum was never observed.  相似文献   

7.
Uniparental isodisomy (iUPD) is a rare genetic condition caused by non-disjunction during meiosis that ultimately leads to a duplication of either the maternal or paternal chromosome in the affected individual. Two types of disorders can result, those due to imprinted genes and those due to homozygosity of recessive disease-causing mutations. Here, we describe the third known case of complete chromosome 4 iUPD of maternal origin. This condition became apparent during whole genome linkage studies of psychiatric disorders in the Portuguese population. The proband is an adult female with normal fertility and no major medical complaints, but a history of major depressive disorder and multiple suicide attempts. The proband's siblings and parents had normal chromosome 4 genotypes and no history of mood disturbance. A brief review of other studies lends support for the possibility that genes on chromosome 4 might confer risk for mood disorders. We conclude that chromosome 4 maternal uniparental disomy (UPD) is a rare disorder that may present with a major depressive phenotype. The lack of a common disease phenotype between this and two other cases of chromosome 4 iUPD [Lindenbaum et al. [1991] Am J Med Genet 49(Suppl 285):1582; Spena et al. [2004] Eur J Hum Genet 12:891-898) would suggest that there is no vital maternal gene imprinting on chromosome 4. However, since there is no reported case of paternal chromosome 4 UPD, paternal gene imprinting on chromosome 4 cannot be excluded.  相似文献   
8.
This study examined the interface between acute hospital care and return to home in relation to elderly patients' perceived ability and preparedness to cope at home. Seventy-six (n = 76) elderly patients aged 60 years and over were randomly recruited from a large Queensland hospital and interviewed prior to discharge about their perceived health, functional status and their ‘readiness’ to cope at home. They were followed up at home 7–10 days post-discharge. Comparisons were made between a number of measures at discharge and post-discharge. Although the majority of patients indicated that they would cope very well upon discharge, a large number of patients reported experiencing considerable difficulty with activities of daily living, particularly instrumental activities of daily living prior to and especially after discharge. The self-reported health status of patients similarly deteriorated between discharge and follow-up. Despite a large number of patients experiencing functional limitations, few were referred to hospital or community-based therapy services. Some policy implications are explored.  相似文献   
9.
Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant Po2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T.  相似文献   
10.
Serial blood samples were taken at two-hour intervals over a 24-hour period from 25 premenopausal vegetarians (12 vegans and 13 ovolactovegetarians) and from 21 omnivorous controls. All members of the former group had been on a vegetarian diet for a minimum of three years. The mean proportion of estradiol unbound to blood proteins was similar in both vegetarians (1.26%) and meat eaters (1.16%). However, the amount bound to albumin was significantly raised in vegetarians (50.1% vs. 43.1%, p less than 0.009), whereas that bound to sex hormone-binding globulin (SHBG) was correspondingly lower (48.7% vs. 55.8%, p = 0.01). Mean levels of SHBG were similar in vegetarians (59.9 nmole/l) and omnivores (62.0 nmole/l), as was the total amount of free fatty acid (0.42 mmole/l for both). Within the vegetarian group, no differences were detected between vegans and ovolactovegetarians.  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