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   383篇
  免费   19篇
  国内免费   4篇
耳鼻咽喉   1篇
儿科学   3篇
妇产科学   39篇
基础医学   84篇
口腔科学   3篇
临床医学   31篇
内科学   87篇
皮肤病学   3篇
神经病学   33篇
外科学   53篇
综合类   1篇
预防医学   26篇
眼科学   1篇
药学   24篇
中国医学   2篇
肿瘤学   15篇
  2024年   1篇
  2022年   12篇
  2021年   30篇
  2020年   13篇
  2019年   13篇
  2018年   14篇
  2017年   13篇
  2016年   22篇
  2015年   16篇
  2014年   21篇
  2013年   14篇
  2012年   44篇
  2011年   48篇
  2010年   12篇
  2009年   17篇
  2008年   16篇
  2007年   29篇
  2006年   18篇
  2005年   9篇
  2004年   13篇
  2003年   12篇
  2002年   10篇
  2001年   1篇
  2000年   1篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
排序方式: 共有406条查询结果,搜索用时 15 毫秒
1.
Technology is a prominent way that young children choose to play. With new advents in technology, children are finding it easier to gain access to technology through parents’ cell phones and tablets. The influx of technology in the daily lives of children is putting into question whether or not children are spending too much time engaging in such play. In the current study, data were collected on how 3–5-year-old children played on a typical weekday and weekend. Of the weekday activities, parents (n?=?31) reported 53.00 hours of technology play for an average of 1.71 hours per child per day. There was an increased amount of time spent on non-technology activities listed by parents for a total of 59.25 hours and an average of 1.91 hours per child. A smaller number of parents (n?=?14) recorded outdoor play, totalling 17.50 hours with an average of 1.25 hours per child.  相似文献   
2.
3.
The proportion of new HIV diagnoses between May and December 2009 across Odessa recently-infected was estimated using the BED-CEIA assay. Logistic regression models were used to explore factors associated with testing as recent. Of 1,313 newly-diagnosed individuals, 321 (24 %) were classified as recent. Recent infection was less likely among older adults [odds ratio (OR) = 0.70 per 10-year increase, 95 % CI 0.60–0.82]. Compared to men residing in Odessa city, women in rural Odessa and non-resident men were more likely to be recently-infected (OR 1.85, 1.26–2.71 and 2.83, 1.15–6.97, respectively). Reason for test was not associated with recent infection. In sensitivity analysis, after excluding individuals tested due to clinical indications, the proportion recently-infected and the association with age remained virtually unchanged. Our findings suggest a high risk of onward transmission, particularly in younger age groups. These findings highlight the need for tailored prevention strategies and ongoing RITA testing to monitor and evaluate effectiveness of prevention programmes.  相似文献   
4.
The adaptive immune system relies on rare cognate lymphocytes to detect pathogen-derived antigens. Na?ve lymphocytes recirculate through secondary lymphoid organs in search of cognate antigen. Here, we show that the na?ve-lymphocyte recirculation pattern is controlled at the level of innate immune recognition, independent of antigen-specific stimulation. We demonstrate that inflammation-induced lymphocyte recruitment to the lymph node is mediated by the remodeling of the primary feed arteriole, and that its physiological role is to increase the efficiency of screening for rare antigen-specific lymphocytes. Our data reveal a mechanism of innate control of adaptive immunity: by increasing the pool of na?ve lymphocytes for detection of foreign antigens via regulation of vascular input to the local lymph node.  相似文献   
5.
Objective: To investigate risk factors for postpartum hemorrhage (PPH) in vaginal deliveries and the influence of previous PPH on the subsequent pregnancy.

Study design: A retrospective cohort study including first singleton deliveries between the years 1988 and 2012 was performed comparing deliveries with and without PPH. In addition, perinatal outcomes of the subsequent pregnancy were evaluated. Multivariable analysis was performed to control for confounders.

Results: PPH complicated 0.8% of all first vaginal deliveries. Significant risk factors for PPH in vaginal delivery, using a multiple logistic regression model, were: post-term pregnancy, fertility treatments, hypertensive disorders, labor dystocia during the 2nd, and perineal tears grade 2 and 3, respectively. Previous PPH was found to be an independent risk factor for PPH in the subsequent pregnancy. Moreover, previous PPH was found to be a significant risk factor for cesarean section (CS) deliver, to complicate delivery with revision of uterus cavity, anemia, and to require blood transfusion.

Conclusion: Previous PPH poses a risk for recurrent PPH in subsequent delivery and an increased risk for CS. As PPH remains one of the major causes of maternal morbidity, this study strengthens the need for a comprehensive evaluation of prior PPH as a major risk factor for PPH recurrence.  相似文献   

6.
Objective: To establish whether failure to progress during labor poses a risk factor for another non-progressive labor (NPL) during the subsequent delivery.

Methods: A retrospective cohort study including singleton pregnancies that failed to progress during the previous labor and resulted in a cesarean section (CS) was conducted. Parturients were classified into three groups for both previous and subsequent labors: CS due to NPL stage I, stage II and an elective CS as a comparison group.

Results: Of 202?462 deliveries, 10?654 women met the inclusion criteria: 3068 women were operated due to NPL stage I and 1218 due to NPL stage II. The comparison group included 6368 women. Using a multivariable logistic regression models, NPL stage I during the previous delivery was found as an independent risk factor for another NPL stage I in the subsequent labor (adjusted odds ratio [OR]?=?2.9; 95% confidence interval [CI]?=?2.4–3.7; p?p?=?0.033; adjusted OR?=?5.3; 95% CI?=?3.7–7.5; p?Conclusion: A previous CS due to a NPL is an independent risk factor for another NPL in the subsequent pregnancy and for recurrent cesarean delivery.  相似文献   
7.
Multicellular spheroids are useful models of mammalian tissue for studies of cell proliferation, differentiation, replacement therapies and drug action. Having a size of 100–500 μm they mimic in vivo micro-environment and characteristic gradients of O2, pH and nutrients. We describe the use of cell-penetrating O2 probes based on phosphorescent Pt-porphyrins to perform high-resolution 2D and 3D mapping of O2 in spheroid structures by live cell fluorescence imaging technique. Optimised procedures for preparation of neurospheres from cortical neural cells isolated from embryonic rat brain, their staining with the phosphorescent O2 probes NanO2 and MM2 and subsequent analysis of oxygenation on different live cell imaging platforms, including widefield and confocal phosphorescence lifetime imaging microscopy (PLIM), conventional confocal and two-photon ratiometric intensity based O2 detection are presented. This is followed by a series of physiological experiments in which oxygenation patterns of the neurospheres are correlated with culturing conditions (atmospheric hypoxia and hyperoxia, size, growth factors), distribution of stem cells, mature neurons and astrocytes, HIF-2α stabilisation and responses to metabolic stimulation. The O2 imaging method allows multiplexing with many conventional fluorescent probes to perform multi-parametric imaging analysis of cells in 3D microenvironment. It can be applied to other types of spheroids and 3D tissue models.  相似文献   
8.
In this paper, we develop and validate an osteometry-based mechanistic approach to calculation of available range of motion (aROM) in presacral intervertebral joints in sagittal bending (SB), lateral bending (LB), and axial rotation (AR). Our basic assumption was the existence of a mechanistic interrelation between the geometry of zygapophysial articular facets and aROM. Trigonometric formulae are developed for aROM calculation, of which the general principle is that the angle of rotation is given by the ratio of the arc length of motion to the radius of this arc. We tested a number of alternative formulae against available in vitro data to identify the most suitable geometric ratios and coefficients for accurate calculation. aROM values calculated with the developed formulae show significant correlation with in vitro data in SB, LB, and AR (Pearson r = 0.900) in the reference mammals (man, sheep, pig, cow). It was found that separate formulae for different zygapophysial facet types (radial (Rf), tangential (Tf), radial with a lock (RfL)) give significantly greater accuracy in aROM calculation than the formulae for the presacral spine as a whole and greater accuracy than the separate formulae for different spine regions (cervical, thoracic, lumbar). The advantage of the facet-specific formulae over the region-specific ones shows that the facet type is a more reliable indicator of the spine mobility than the presence or absence of ribs. The greatest gain in calculation accuracy with the facet-specific formulae is characteristic in AR aROM. The most important theoretical outcome is that the evolutionary differentiation of the zygapophysial facets in mammals, that is the emergence of Tf joints in the rib cage area of the spine, was more likely associated with the development of AR rather than with SB mobility and, hence, with cornering rather than with forward galloping. The AR aROM can be calculated with the formulae common for man, sheep, pig, and cow. However, the SB aROM of the human spine is best calculated with different coefficient values in the formulae than those for studied artiodactyls. The most suitable coefficient values indicate that the zygapophysial articular facets tend to slide past each other to a greater extent in the human thoracolumbar spine rather than in artiodactyls. Due to this, artiodactyls retain relatively greater facet overlap in extremely flexed and extremely extended spine positions, which may be more crucial for their quadrupedal gallop than for human bipedal locomotion. The SB, LB, and AR aROMs are quite separate in respect of the formulae structure in the cervical region (radial facet type). However, throughout the thoracolumbar spine (tangential and radial with lock facets), the formulae for LB and AR are basically similar differing in coefficient values only. This means that, in the thoracolumbar spine, the greater the LB aROM, the greater the AR aROM, and vice versa. The approach developed promises a wide osteological screening of extant and extinct mammals to study the sex, age, geographical variations, and disorders.  相似文献   
9.
10.
Aims To compare clinical status, mother‐to‐child transmission (MTCT) rates, use of prevention of (PMTCT) interventions and pregnancy outcomes between HIV‐infected injecting drug users (IDUs) and non‐IDUs. Design and setting Prospective cohort study conducted in seven human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) Centres in Ukraine, 2000–10. Participants Pregnant HIV‐infected women, identified before/during pregnancy or intrapartum, and their live‐born infants (n = 6200); 1028 women followed post‐partum. Measurements Maternal and delivery characteristics, PMTCT prophylaxis, MTCT rates, preterm delivery (PTD) and low birth weight (LBW). Findings Of 6200 women, 1111 (18%) reported current/previous IDU. The proportion of IDUs diagnosed with HIV before conception increased from 31% in 2000/01 to 60% in 2008/09 (P < 0.01). Among women with undiagnosed HIV at conception, 20% of IDUs were diagnosed intrapartum versus 4% of non‐IDUs (P < 0.01). At enrolment, 14% of IDUs had severe/advanced HIV symptoms versus 6% of non‐IDUs (P < 0.001). IDUs had higher rates of PTD and LBW infants than non‐IDUs, respectively, 16% versus 7% and 22% versus 10% (P < 0.001). IDUs were more likely to receive no neonatal or intrapartum PMTCT prophylaxis compared with non‐IDUs (OR 2.81, p < 0.001). MTCT rates were 10.8% in IDUs versus 5.9% in non‐IDUs; IDUs had increased MTCT risk (adjusted odds ratio 1.32, P = 0.049). Fewer IDUs with treatment indications received HAART compared with non‐IDUs (58% versus 68%, P = 0.03). Conclusions Pregnant human immunodeficiency virus‐infected injecting drug users in Ukraine have worse clinical status, poorer access to prevention of mother‐to‐child transmission prophylaxis and highly active antiretroviral therapy, more adverse pregnancy outcomes and higher risk of mother‐to‐child transmission than non‐injecting drug user women.  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