全文获取类型
收费全文 | 2187篇 |
免费 | 256篇 |
出版年
2021年 | 40篇 |
2019年 | 21篇 |
2018年 | 23篇 |
2017年 | 24篇 |
2016年 | 39篇 |
2015年 | 50篇 |
2014年 | 43篇 |
2013年 | 72篇 |
2012年 | 86篇 |
2011年 | 88篇 |
2010年 | 71篇 |
2009年 | 60篇 |
2008年 | 65篇 |
2007年 | 82篇 |
2006年 | 41篇 |
2005年 | 71篇 |
2004年 | 60篇 |
2003年 | 53篇 |
2002年 | 82篇 |
2001年 | 72篇 |
2000年 | 65篇 |
1999年 | 58篇 |
1998年 | 30篇 |
1997年 | 33篇 |
1996年 | 25篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 31篇 |
1992年 | 57篇 |
1991年 | 41篇 |
1990年 | 44篇 |
1989年 | 38篇 |
1988年 | 40篇 |
1987年 | 35篇 |
1986年 | 44篇 |
1985年 | 49篇 |
1984年 | 39篇 |
1983年 | 23篇 |
1982年 | 27篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 18篇 |
1978年 | 20篇 |
1977年 | 20篇 |
1975年 | 20篇 |
1974年 | 35篇 |
1973年 | 22篇 |
1971年 | 30篇 |
1968年 | 18篇 |
1966年 | 22篇 |
排序方式: 共有2443条查询结果,搜索用时 762 毫秒
221.
Background and Objectives
Existing data on pregnancy complications in inflammatory bowel disease (IBD) are inconsistent. To address these inconsistencies, we investigated potential associations between IBD, IBD-related medication use during pregnancy, and pregnancy loss, pre-eclampsia, preterm delivery, Apgar score, and congenital abnormalities.Methods
We conducted a cohort study in >85,000 Danish National Birth Cohort women who were pregnant in the period 1996-2002 and had information on IBD, IBD-related medication use (systemic or local corticosteroids, 5-aminosalicylates), pregnancy outcomes and potential confounders. We evaluated associations between IBD and adverse pregnancy/birth outcomes using Cox regression and log-linear binomial regression.Results
IBD was strongly and significantly associated with severe pre-eclampsia, preterm premature rupture of membranes and medically indicated preterm delivery in women using systemic corticosteroids during pregnancy (hazard ratios [HRs] >7). IBD was also associated with premature preterm rupture of membranes in women using local corticosteroid medications (HR 3.30, 95% confidence interval [CI] 1.33-8.20) and with medically indicated preterm delivery (HR 1.91, 95% CI 0.99-3.68) in non-medicated women. Furthermore, IBD was associated with low 5-minute Apgar score in term infants (risk ratio [RR] 2.19, 95% CI 1.03-4.66). Finally, Crohn’s disease (but not ulcerative colitis) was associated with major congenital abnormalities in the offspring (RR 1.85, 95% CI 1.06-3.21). No child with a congenital abnormality born to a woman with IBD was exposed to systemic corticosteroids in utero.Conclusion
Women with IBD are at increased risk of severe pre-eclampsia, medically indicated preterm delivery, preterm premature rupture of membranes, and delivering infants with low Apgar score and major congenital malformations. These associations are only partly explained by severe disease as reflected by systemic corticosteroid use. 相似文献222.
Herein, we describe a novel technique for heterotopic abdominal heart-lung transplantation (HAHLT) in rats. The configuration of the transplant graft involves anastomosis of donor inferior vena cava (IVC) to recipient IVC, and donor ascending aorta (Ao) to recipient abdominal Ao. The right upper and middle lung lobes are preserved and function as conduits for blood flow from right heart to left heart.There are several advantages to using this technique, and it lends itself to a broad range of applications. Because the graft is transplanted in a configuration that allows for dyamic volume-loading, cardiac function may be directly assessed in vivo. The use of pressure-volume conductance catheters permits characterization of load-dependent and load-independent hemodynamic parameters. The graft may be converted to a loaded configuration by applying a clamp to the recipient’s infra-hepatic IVC. We describe modified surgical techniques for both donor and recipient operations, and an ideal myocardial protection strategy. Depending on the experimental aim, this model may be adapted for use in both acute and chronic studies of graft function, immunologic status, and variable ventricular loading conditions. The conducting airways to the transplanted lung are preserved, and allow for acute lung re-ventilation. This facilitates analysis of the effects of the mixed venous and arterial blood providing coronary perfusion to the graft.A limitation of this model is its technical complexity. There is a significant learning curve for new operators, who should ideally be mentored in the technique. A surgical training background is advantageous for those wishing to apply this model. Despite its complexity, we aim to present the model in a clear and easily applicable format. Because of the physiologic similarity of this model to orthotopic transplantation, and its broad range of study applications, the effort invested in learning the technique is likely to be worthwhile. 相似文献
223.
Sara Charmsaz Kirrilee Beckett Fiona M. Smith Claudia Bruedigam Andrew S. Moore Fares Al-Ejeh Steven W. Lane Andrew W. Boyd 《PloS one》2015,10(6)
Members of the Eph family of receptor tyrosine kinases and their membrane bound ephrin ligands have been shown to play critical roles in many developmental processes and more recently have been implicated in both normal and pathological processes in post-embryonic tissues. In particular, expression studies of Eph receptors and limited functional studies have demonstrated a role for the Eph/ephrin system in hematopoiesis and leukemogenesis. In particular, EphA2 was reported on hematopoietic stem cells and stromal cells. There are also reports of EphA2 expression in many different types of malignancies including leukemia, however there is a lack of knowledge in understanding the role of EphA2 in hematopoiesis and leukemogenesis. We explored the role of EphA2 in hematopoiesis by analyzing wild type and EphA2 knockout mice. Mature, differentiated cells, progenitors and hematopoietic stem cells derived from knockout and control mice were analyzed and no significant abnormality was detected. These studies showed that EphA2 does not have an obligatory role in normal hematopoiesis. Comparative studies using EphA2-negative MLL-AF9 leukemias derived from EphA2-knockout animals showed that there was no detectable functional role for EphA2 in the initiation or progression of the leukemic process. However, expression of EphA2 in leukemias initiated by MLL-AF9 suggested that this protein might be a possible therapy target in this type of leukemia. We showed that treatment with EphA2 monoclonal antibody IF7 alone had no effect on tumorigenicity and latency of the MLL-AF9 leukemias, while targeting of EphA2 using EphA2 monoclonal antibody with a radioactive payload significantly impaired the leukemic process. Altogether, these results identify EphA2 as a potential radio-therapeutic target in leukemias with MLL translocation. 相似文献
224.
简要介绍了应用于中华鲟(Acipenser sinensis)的pop-up标志固定方法,包括预埋体的制作、植入及pop-up标志悬挂等技术,并对其应用效果进行了评价。 相似文献
225.
Emma Holder Barbara Stevenson Raymond Farley Tom Hilliard Theresa Wodehouse Lucinda Somerton Mia Larsen Jean O'Donoghue Rebecca L. Coles Ronald K. Scheule Seng H. Cheng Deborah R. Gill Stephen C. Hyde Uta Griesenbach Eric W. F. W. Alton David J. Porteous A. Christopher Boyd 《The journal of gene medicine》2010,12(1):55-63
226.
Aranapakam M. Venkatesan O. Dos Santos John Ellingboe Deborah A. Evrard Boyd L. Harrison Deborah L. Smith Rosemary Scerni Geoffrey A. Hornby Lee E. Schechter Terrence H. Andree 《Bioorganic & medicinal chemistry letters》2010,20(3):824-827
Several benzofuran derivatives linked to a 3-indoletetrahydropyridine through an alkyl chain were prepared and evaluated for serotonin transporter and 5-HT1A receptor affinities. Their design, synthesis and structure–activity relationships are described. 相似文献
227.
Zhenrong Xu Salvacion Cacatian Jing Yuan Robert D. Simpson Lanqi Jia Wei Zhao Colin M. Tice Patrick T. Flaherty Joan Guo Alexey Ishchenko Suresh B. Singh Zhongren Wu Brian M. McKeever Boyd B. Scott Yuri Bukhtiyarov Jennifer Berbaum Jennifer Mason Reshma Panemangalore Maria Grazia Cappiello Ross Bentley David A. Claremon 《Bioorganic & medicinal chemistry letters》2010,20(2):694-699
Structure-guided drug design led to new alkylamine renin inhibitors with improved in vitro and in vivo potency. Lead compound 21a, has an IC50 of 0.83 nM for the inhibition of human renin in plasma (PRA). Oral administration of 21a at 10 mg/kg resulted in >20 h reduction of blood pressure in a double transgenic rat model of hypertension. 相似文献
228.
229.
Background
Vibrio Pathogenicity Island-2 (VPI-2) is a 57 kb region present in choleragenic V. cholerae isolates that is required for growth on sialic acid as a sole carbon source. V. cholerae non-O1/O139 pathogenic strains also contain VPI-2, which in addition to sialic acid catabolism genes also encodes a type 3 secretion system in these strains. VPI-2 integrates into chromosome 1 at a tRNA-serine site and encodes an integrase intV2 (VC1758) that belongs to the tyrosine recombinase family. IntV2 is required for VPI-2 excision from chromosome 1, which occurs at very low levels, and formation of a non-replicative circular intermediate. 相似文献230.
Julie L. McAuley Jerry E. Chipuk Kelli L. Boyd Nick Van De Velde Douglas R. Green Jonathan A. McCullers 《PLoS pathogens》2010,6(7)
With the recent emergence of a novel pandemic strain, there is presently intense interest in understanding the molecular signatures of virulence of influenza viruses. PB1-F2 proteins from epidemiologically important influenza A virus strains were studied to determine their function and contribution to virulence. Using 27-mer peptides derived from the C-terminal sequence of PB1-F2 and chimeric viruses engineered on a common background, we demonstrated that induction of cell death through PB1-F2 is dependent upon BAK/BAX mediated cytochrome c release from mitochondria. This function was specific for the PB1-F2 protein of A/Puerto Rico/8/34 and was not seen using PB1-F2 peptides derived from past pandemic strains. However, PB1-F2 proteins from the three pandemic strains of the 20th century and a highly pathogenic strain of the H5N1 subtype were shown to enhance the lung inflammatory response resulting in increased pathology. Recently circulating seasonal influenza A strains were not capable of this pro-inflammatory function, having lost the PB1-F2 protein''s immunostimulatory activity through truncation or mutation during adaptation in humans. These data suggest that the PB1-F2 protein contributes to the virulence of pandemic strains when the PB1 gene segment is recently derived from the avian reservoir. 相似文献