全文获取类型
收费全文 | 3685篇 |
免费 | 304篇 |
国内免费 | 6篇 |
出版年
2024年 | 4篇 |
2023年 | 24篇 |
2022年 | 66篇 |
2021年 | 116篇 |
2020年 | 73篇 |
2019年 | 72篇 |
2018年 | 93篇 |
2017年 | 79篇 |
2016年 | 144篇 |
2015年 | 219篇 |
2014年 | 234篇 |
2013年 | 266篇 |
2012年 | 303篇 |
2011年 | 312篇 |
2010年 | 225篇 |
2009年 | 171篇 |
2008年 | 214篇 |
2007年 | 195篇 |
2006年 | 205篇 |
2005年 | 190篇 |
2004年 | 158篇 |
2003年 | 157篇 |
2002年 | 144篇 |
2001年 | 30篇 |
2000年 | 17篇 |
1999年 | 20篇 |
1998年 | 27篇 |
1997年 | 24篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1970年 | 5篇 |
排序方式: 共有3995条查询结果,搜索用时 946 毫秒
121.
Adi L. Tarca Edgar Hernandez-Andrade Hyunyoung Ahn Maynor Garcia Zhonghui Xu Steven J. Korzeniewski Homam Saker Tinnakorn Chaiworapongsa Sonia S. Hassan Lami Yeo Roberto Romero 《PloS one》2016,11(11)
ObjectivesTo assess the value of single and serial fetal biometry for the prediction of small- (SGA) and large-for-gestational-age (LGA) neonates delivered preterm or at term.MethodsA cohort study of 3,971 women with singleton pregnancies was conducted from the first trimester until delivery with 3,440 pregnancies (17,334 scans) meeting the following inclusion criteria: 1) delivery of a live neonate after 33 gestational weeks and 2) two or more ultrasound examinations with fetal biometry parameters obtained at ≤36 weeks. Primary outcomes were SGA (<5th centile) and LGA (>95th centile) at birth based on INTERGROWTH-21st gender-specific standards. Fetus-specific estimated fetal weight (EFW) trajectories were calculated by linear mixed-effects models using data up to a fixed gestational age (GA) cutoff (28, 32, or 36 weeks) for fetuses having two or more measurements before the GA cutoff and not already delivered. A screen test positive for single biometry was based on Z-scores of EFW at the last scan before each GA cut-off so that the false positive rate (FPR) was 10%. Similarly, a screen test positive for the longitudinal analysis was based on the projected (extrapolated) EFW at 40 weeks from all available measurements before each cutoff for each fetus.ResultsFetal abdominal and head circumference measurements, as well as birth weights in the Detroit population, matched well to the INTERGROWTH-21st standards, yet this was not the case for biparietal diameter (BPD) and femur length (FL) (up to 9% and 10% discrepancy for mean and confidence intervals, respectively), mainly due to differences in the measurement technique. Single biometry based on EFW at the last scan at ≤32 weeks (GA IQR: 27.4–30.9 weeks) had a sensitivity of 50% and 53% (FPR = 10%) to detect preterm and term SGA and LGA neonates, respectively (AUC of 82% both). For the detection of LGA using data up to 32- and 36-week cutoffs, single biometry analysis had higher sensitivity than longitudinal analysis (52% vs 46% and 62% vs 52%, respectively; both p<0.05). Restricting the analysis to subjects with the last observation taken within two weeks from the cutoff, the sensitivity for detection of LGA, but not SGA, increased to 65% and 72% for single biometry at the 32- and 36-week cutoffs, respectively. SGA screening performance was higher for preterm (<37 weeks) than for term cases (73% vs 46% sensitivity; p<0.05) for single biometry at ≤32 weeks.ConclusionsWhen growth abnormalities are defined based on birth weight, growth velocity (captured in the longitudinal analysis) does not provide additional information when compared to the last measurement for predicting SGA and LGA neonates, with both approaches detecting one-half of the neonates (FPR = 10%) from data collected at ≤32 weeks. Unlike for SGA, LGA detection can be improved if ultrasound scans are scheduled as close as possible to the gestational-age cutoff when a decision regarding the clinical management of the patient needs to be made. Screening performance for SGA is higher for neonates that will be delivered preterm. 相似文献
122.
123.
124.
Megan B. Machmuller Jacqueline E. Mohan Jeffrey M. Minucci Carly A. Phillips Nina Wurzburger 《Biogeochemistry》2016,129(3):255-272
Climate change may affect the microbial production and temperature sensitivity of extracellular enzymes that release carbon (C) and nutrients from soil organic matter. We measured the response of six hydrolytic enzymes involved in C, nitrogen (N), and phosphorus (P) degradation to experimental warming in a mixed-deciduous forest persisting on highly-weathered Ultisols (Whitehall Forest, Georgia, US). We found that warming produced no consistent enzyme response. However, we observed significant seasonal variation in enzyme activities, temperature sensitivities and elemental enzyme ratios (C:N and C:P). Seasonal differences in enzyme activity and temperature sensitivity were best explained by soil moisture and temperature. Our results suggest that seasonal dynamics in soil microclimate, organic matter supply, and microbial demand exert more control on enzyme dynamics than does a uniform increase in soil temperature. 相似文献
125.
126.
Karol Szeszko Nina Smolinska Marta Kiezun Kamil Dobrzyn Anna Maleszka Tadeusz Kaminski 《Functional & integrative genomics》2016,16(2):101-114
Reproductive functions are closely related to nutritional status. Recent studies suggest that adiponectin may be a hormonal link between them. Adiponectin is an adipocytokine, abundantly expressed in adipose tissues. It plays a dominant role in lipid and carbohydrate metabolism by stimulating fatty acid oxidation, decreasing plasma triglycerides, and increasing cells’ sensitivity to insulin and has direct antiatherosclerotic effects. The hormone is also postulated to play a modulatory role in the regulation of the reproductive system. The aim of this study was to identify differentially expressed genes (DE-genes) in response to adiponectin treatment of porcine luteal ovarian cells. The global expression of genes in the porcine ovary was investigated using the Porcine (V2) Two-color gene expression microarray, 4?×?44 (Agilent, USA). Analysis of the microarray data showed that 701 genes were differentially expressed and 389 genes showed a fold change greater than 1.2 (p?<?0.05). Among this number, 186 genes were up-regulated and 203 were down-regulated. The list of DE-genes was used for gene ontology analyses. The biological process list was generated from up-regulated and down-regulated DE-genes. We found that up-regulated products of DE-genes take part in 30 biological processes and down-regulated products in 9. Analysis of the interaction network among DE-genes showed that adiponectin interacts with genes involved in important processes in luteal cells. These results provide a basis for future work describing the detailed interactions and relationships explaining local regulation of adiponectin actions in the ovary of pigs. 相似文献
127.
128.
Anmol Kumar Jaakko Kopra K?rt Varendi Lauriina L. Porokuokka Anne Panhelainen Satu Kuure Pepin Marshall Nina Karalija Mari-Anne H?rma Carolina Vilenius Kersti Lillev?li Triin Tekko Jelena Mijatovic Nita Pulkkinen Madis Jakobson Maili Jakobson Roxana Ola Erik Palm Maria Lindahl Ingrid Str?mberg Vootele V?ikar T. Petteri Piepponen Mart Saarma Jaan-Olle Andressoo 《PLoS genetics》2016,12(1)
129.
Down‐regulation of microRNAs of the miR‐200 family and up‐regulation of Snail and Slug in inflammatory bowel diseases — hallmark of epithelial−mesenchymal transition
下载免费PDF全文
![点击此处可从《Journal of cellular and molecular medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
130.
Nina Tonn Sara C. Novais Cátia S. E. Silva Hugo A. Morais João P. S. Correia 《Marine Biology Research》2016,12(9):948-957
Animal welfare during handling and transportation to aquaculture facilities or public aquaria is commonly estimated by addressing injury and mortality levels. Although these procedures have been optimized for different species, data on individual species’ cellular capabilities to tolerate stress are still scarce. In the present study, several biomarkers related with oxidative stress and energy metabolism were assessed in Holothuria forskali during animal acclimation, pre-transport, transport and quarantine. Combined analyses confirmed that sea cucumbers experienced high oxidative stress during transport, but had the capability to deal with it using a complex of cellular defence mechanisms, which enabled recovery from oxidative stress without permanent damage. Through a better understanding of individual species and the development of optimal parameters, this approach has the potential to improve animal wellbeing during and after acclimation, transportation and recovery processes. 相似文献