全文获取类型
收费全文 | 14518篇 |
免费 | 1399篇 |
国内免费 | 10篇 |
出版年
2023年 | 78篇 |
2022年 | 194篇 |
2021年 | 393篇 |
2020年 | 221篇 |
2019年 | 316篇 |
2018年 | 299篇 |
2017年 | 300篇 |
2016年 | 470篇 |
2015年 | 813篇 |
2014年 | 897篇 |
2013年 | 1003篇 |
2012年 | 1248篇 |
2011年 | 1205篇 |
2010年 | 750篇 |
2009年 | 680篇 |
2008年 | 882篇 |
2007年 | 854篇 |
2006年 | 747篇 |
2005年 | 697篇 |
2004年 | 663篇 |
2003年 | 544篇 |
2002年 | 528篇 |
2001年 | 109篇 |
2000年 | 70篇 |
1999年 | 115篇 |
1998年 | 144篇 |
1997年 | 95篇 |
1996年 | 88篇 |
1995年 | 81篇 |
1994年 | 85篇 |
1993年 | 76篇 |
1992年 | 58篇 |
1991年 | 64篇 |
1990年 | 74篇 |
1989年 | 54篇 |
1988年 | 58篇 |
1987年 | 58篇 |
1986年 | 42篇 |
1985年 | 64篇 |
1984年 | 63篇 |
1983年 | 61篇 |
1982年 | 65篇 |
1981年 | 61篇 |
1980年 | 62篇 |
1979年 | 48篇 |
1978年 | 42篇 |
1977年 | 45篇 |
1976年 | 50篇 |
1974年 | 38篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
941.
Theresa W. Gauthier Sowmya S. Mohan Teresa S. Gross Frank L. Harris David M. Guidot Lou Ann S. Brown 《PloS one》2015,10(5)
The accumulation of fatty acid ethyl esters (FAEEs) in meconium of term newborns has been described as one potential biomarker of maternal alcohol use during pregnancy. FAEEs accumulate in multiple alcohol-exposed fetal tissues and in the placenta. Limited research has focused on the identification of the premature newborn exposed to alcohol in utero. We hypothesized that maternal alcohol use occurs in a significant proportion of premature deliveries and that this exposure can be detected as elevated placental FAEEs. The goals of this study were to 1) determine the prevalence of maternal alcohol use in the premature newborn and 2) investigate whether placental FAEEs could identify those newborns with fetal alcohol exposure. This prospective observational study evaluated 80 placentas from 80 women after premature delivery. Subjects were interviewed for alcohol intake and placental FAEEs were quantified via GC/MS. Receiver Operator Characteristic (ROC) Curves were generated to evaluate the ability of placental FAEEs to predict maternal drinking during pregnancy. Adjusted ROC curves were generated to adjust for gestational age, maternal smoking, and illicit drug use. 30% of the subjects admitted to drinking alcohol during pregnancy and approximately 14% answered questions indicative of problem drinking (designated AUDIT+). The specific FAEEs ethyl stearate and linoleate, as well as combinations of oleate + linoleate + linolenate (OLL) and of OLL + stearate, were significantly (p<0.05) elevated in placentas from AUDIT+ pregnancies. Adjusted ROC Curves generated areas under the curve ranging from 88–93% with negative predictive values of 97% for AUDIT+ pregnancies. We conclude that nearly one third of premature pregnancies were alcohol-exposed, and that elevated placental FAEEs hold great promise to accurately determine maternal alcohol use, particularly heavy use, in pregnancies complicated by premature delivery. 相似文献
942.
Weight change in the first 2 months of a lifestyle intervention predicts weight changes 8 years later 下载免费PDF全文
943.
Blunted suppression of acyl‐ghrelin in response to fructose ingestion in obese adolescents: The role of insulin resistance 下载免费PDF全文
944.
Rafael Chacon Alexey Wilfrido Clara Jorge Jara Julio Armero Celina Lozano Nathalie El Omeiri Marc-Alain Widdowson Eduardo Azziz-Baumgartner 《PloS one》2015,10(10)
We estimate the proportion of patients hospitalized for suspected dengue that tested positive for influenza virus in El Salvador during the 2012 influenza season. We tested specimens from 321 hospitalized patients: 198 patients with SARI and 123 patients with suspected dengue. Among 121 hospitalized suspected dengue (two co-infected excluded) patients, 28% tested positive for dengue and 19% positive for influenza; among 35 with suspected dengue and respiratory symptoms, 14% were positive for dengue and 39% positive for influenza. One percent presented co-infection between influenza and dengue. Clinicians should consider the diagnosis of influenza among patients with suspected dengue during the influenza season. 相似文献
945.
Frequent self‐weighing as part of a constellation of healthy weight control practices in young adults 下载免费PDF全文
946.
947.
Najma Latif Alfred Quillon Padmini Sarathchandra Ann McCormack Alec Lozanoski Magdi H. Yacoub Adrian H. Chester 《PloS one》2015,10(6)
Valve interstitial cells (VICs) are fibroblastic in nature however in culture it is widely accepted that they differentiate into a myofibroblastic phenotype. This study assessed a fibroblast culture media formulation for its ability to maintain the phenotype and function of VICs as in the intact healthy valve. Normal human VICs were cultured separately in standard DMEM and in fibroblast media consisting of FGF2 (10ng/ml), insulin (50ng/ml) and 2% FCS for at least a week. Cell morphology, aspect ratio, size, levels and distribution of protein expression, proliferation, cell cycle, contraction and migration were assessed. Some VICs and some valve endothelial cells expressed FGF2 in valve tissue and this expression was increased in calcified valves. VICs in DMEM exhibited large, spread cells whereas VICs in fibroblast media were smaller, elongated and spindly. Aspect ratio and size were both significantly higher in DMEM (p<0.01). The level of expression of α-SMA was significantly reduced in fibroblast media at day 2 after isolation (p<0.01) and the expression of α-SMA, SM22 and EDA-fibronectin was significantly reduced in fibroblast media at days 7 and 12 post-isolation (p<0.01). Expression of cytoskeletal proteins, bone marker proteins and extracellular matrix proteins was reduced in fibroblast media. Proliferation of VICs in fibroblast media was significantly reduced at weeks 1 (p<0.05) and 2 (p<0.01). Collagen gel contraction was significantly reduced in fibroblast media (p<0.05). VICs were found to have significantly fewer and smaller focal adhesions in fibroblast media (p<0.01) with significantly fewer supermature focal adhesions in fibroblast media (p<0.001). Ultrastructurally, VICs in fibroblast media resembled native VICs from intact valves. VICs in fibroblast media demonstrated a slower migratory ability after wounding at 72 hours (p<0.01). Treatment of human VICs with this fibroblast media formulation has the ability to maintain and to dedifferentiate the VICs back to a fibroblastic phenotype with phenotypic and functional characteristics ascribed to cells in the intact valve. This methodology is fundamental in the study of normal valve biology, pathology and in the field of tissue engineering. 相似文献
948.
David M Albala Jerome B Riebman Richard Kocharian Bogdan Ilie John Albanese Jessica Shen Liza Ovington Jonathan Batiller 《Reviews in urology》2015,17(1):25-30
In the United States, fibrin sealants have been used to achieve hemostasis for nearly two decades. Although their clinical utility was first demonstrated in cardiac surgery, their effectiveness and safety have since been demonstrated to extend to a wide array of procedures. Fibrin sealants typically contain two components—fibrinogen and thrombin—that are combined and delivered simultaneously to a target bleeding site in order to achieve hemostasis. However, many commercial formulations contain other additional components, such as antifibrinolytic agents, that have been associated with adverse outcomes. This subanalysis compares the safety and effectiveness of a fibrin sealant versus an absorbable hemostat for achieving hemostasis during urologic procedures with mild to moderate bleeding.Key words: Hemostasis, Hemostatics, Fibrin tissue adhesive, Urologic surgical procedures, Surgical techniqueIn the United States, fibrin sealants have been used to achieve hemostasis for nearly two decades. Although their clinical utility was first demonstrated in cardiac surgery,1 their effectiveness and safety have since been demonstrated to extend to a wide array of procedures, including cardiovascular, gastrointestinal, pneumothoracic, neurologic, urologic, otolaryngologic, dental, and reconstructive surgeries.2,3 Within the field of urology, fibrin sealants have been used to manage bleeding from renal trauma,4 as well as to facilitate hemostasis during renal surgeries, including partial nephrectomies.5–7Fibrin sealants typically contain two components—fibrinogen and thrombin—that are combined and delivered simultaneously to a target bleeding site (TBS) in order to achieve hemostasis.3 Many commercial formulations contain other additional components, such as antifibrinolytic agents, that have been associated with adverse outcomes. For example, in an observational study (N = 4374), the antifibrinolytic aprotinin was associated with an increased risk of long-term mortality within 5 years following coronary artery bypass graft surgery.8 Furthermore, repeated exposure to aprotinin may lead to allergic or potentially fatal anaphylactic reactions.9–11 For this reason, the US Food and Drug Administration (FDA) issued an alert in 2006 indicating that caution should be used when using aprotinin in patients with a history of previous exposure to the product.12 Tranexamic acid, another antifibrinolytic present in some commercial fibrin sealants, has been associated with alterations in neural tissue growth and adherence.13 Because of the risk of cerebral neurologic toxicity, fibrin sealants containing tranexamic acid are contraindicated for use in neurosurgery or in surgical procedures during which contact with cerebrospinal fluid or dura mater may occur.14In a phase III, randomized, single-blind, parallel-group, multicenter study,15 the fibrin sealant CROSSEAL™ (Ethicon, Inc., Somerville, NJ) significantly reduced the time to hemostasis during liver resection surgery compared with conventional hemostatic techniques. EVICEL® Fibrin Sealant (Human) (Ethicon, Inc.), the successor of CROSSEAL, requires no antifibrinolytic additive and is therefore both aprotinin and tranexamic acid free, and achieves hemostasis using exclusively human components.16 The effectiveness and safety of this fibrin sealant for hemostasis in soft tissue during elective retroperitoneal or intra-abdominal surgery were compared with an absorbable hemostat (SURGICEL® Absorbable Hemostat; Ethicon, Inc.) in a randomized, active-controlled, multicenter study.17 This article describes a subanalysis of data from the largest patient subgroup from that study, and evaluates the effectiveness and safety of a fibrin sealant versus an absorbable hemostat for patients who underwent urologic surgical procedures. 相似文献
949.
Jun N‐terminal kinase activity is required for invagination but not differentiation of the sea urchin archenteron 下载免费PDF全文
Jason T. Long Leslie Irwin Addison C. Enomoto Zachary Grow Jessica Ranck Margaret T. Peeler 《Genesis (New York, N.Y. : 2000)》2015,53(12):762-769
Although sea urchin gastrulation is well described at the cellular level, our understanding of the molecular changes that trigger the coordinated cell movements involved is not complete. Jun N‐terminal kinase (JNK) is a component of the planar cell polarity pathway and is required for cell movements during embryonic development in several animal species. To study the role of JNK in sea urchin gastrulation, embryos were treated with JNK inhibitor SP600125 just prior to gastrulation. The inhibitor had a limited and specific effect, blocking invagination of the archenteron. Embryos treated with 2 μM SP600125 formed normal vegetal plates, but did not undergo invagination to form an archenteron. Other types of cell movements, specifically ingression of the skeletogenic mesenchyme, were not affected, although the development and pattern of the skeleton was abnormal in treated embryos. Pigment cells, derived from nonskeletogenic mesenchyme, were also present in SP600125‐treated embryos. Despite the lack of a visible archenteron in treated embryos, cells at the original vegetal plate expressed several molecular markers for endoderm differentiation. These results demonstrate that JNK activity is required for invagination of the archenteron but not its differentiation, indicating that in this case, morphogenesis and differentiation are under separate regulation. genesis 53:762–769, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
950.
Elamaran Meibalan Mary Ann Comunale Ana M. Lopez Lawrence W. Bergman Anand Mehta Akhil B. Vaidya James M. Burns Jr. 《Eukaryotic cell》2015,14(4):371-384
Malaria parasites replicating inside red blood cells (RBCs) export a large subset of proteins into the erythrocyte cytoplasm to facilitate parasite growth and survival. PTEX, the parasite-encoded translocon, mediates protein transport across the parasitophorous vacuolar membrane (PVM) in Plasmodium falciparum-infected erythrocytes. Proteins exported into the erythrocyte cytoplasm have been localized to membranous structures, such as Maurer''s clefts, small vesicles, and a tubovesicular network. Comparable studies of protein trafficking in Plasmodium vivax-infected reticulocytes are limited. With Plasmodium yoelii-infected reticulocytes, we identified exported protein 2 (Exp2) in a proteomic screen of proteins putatively transported across the PVM. Immunofluorescence studies showed that P. yoelii Exp2 (PyExp2) was primarily localized to the PVM. Unexpectedly, PyExp2 was also associated with distinct, membrane-bound vesicles in the reticulocyte cytoplasm. This is in contrast to P. falciparum in mature RBCs, where P. falciparum Exp2 (PfExp2) is exclusively localized to the PVM. Two P. yoelii-exported proteins, PY04481 (encoded by a pyst-a gene) and PY06203 (PypAg-1), partially colocalized with these PyExp2-positive vesicles. Further analysis revealed that with P. yoelii, Plasmodium berghei, and P. falciparum, cytoplasmic Exp2-positive vesicles were primarily observed in CD71+ reticulocytes versus mature RBCs. In transgenic P. yoelii 17X parasites, the association of hemagglutinin-tagged PyExp2 with the PVM and cytoplasmic vesicles was retained, but the pyexp2 gene was refractory to deletion. These data suggest that the localization of Exp2 in mouse and human RBCs can be influenced by the host cell environment. Exp2 may function at multiple points in the pathway by which parasites traffic proteins into and through the reticulocyte cytoplasm. 相似文献