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261.
Annemijn Vis Jan CAM Lammers Roel de Vroege Martijn MJ van Nieuwburg Marlijn S Jansen Joyce MJ Visser Bart Meuris Paul F Gründeman Jolanda Kluin 《Comparative medicine》2021,71(3):235
Sheep are a commonly used and validated model for cardiovascular research and, more specifically, for heart valve research. Implanting a heart valve on the arrested heart in sheep is complex and is often complicated by difficulties in restarting the heart, causing significant on-table mortality. Therefore, optimal cardioprotective management during heart valve implantation in sheep is essential. However, little is known about successful cardioprotective management techniques in sheep. This article reports our experience in the cardioprotective management of 20 female sheep that underwent surgical aortic valve replacement with a stented tissue-engineered heart valve prosthesis. During this series of experiments, we modified our cardioprotection protocol to improve survival. We emphasize the importance of total body hypothermia and external cooling of the heart. Furthermore, we recommend repeated cardioplegia administration at 20 min intervals during surgery, with the final dosage of cardioplegia given immediately before the de-clamping of the aorta. To reduce the number of defibrillator shocks during a state of ventricular fibrillation (VF), we have learned to restart the heart by reclamping the aorta, administering cardioplegia until cardiac arrest, and de-clamping the aorta thereafter. Despite these encouraging results, more research is needed to finalize a protocol for this procedure.Sheep are a commonly used and well-validated model for cardiovascular research, particularly for heart valve research, as blood pressure, heart rate, cardiac output, and intracardiac pressures are similar between sheep and humans. Sheep are particularly useful for heart valve research because observable changes in implanted heart valve bioprostheses that would take several years to develop in humans are apparent after only a few months in sheep.3,11 This feature allows the ovine model to provide relevant and important information about heart valve prostheses in a relatively short time span. The first preclinical step in developing novel heart valves is to test the valve in the pulmonary position in sheep. This surgical technique is relatively easy, as the procedure can be performed on a beating heart in a low-pressure circulation. However, aortic valve surgery is the most frequently performed valvular surgical intervention in human patients.12 Thus, an important next step is to prove the clinical applicability of a new valve by testing the valve in-vivo in the aortic position in an animal model. In contrast to pulmonary valve replacement, aortic valve replacement must be performed on an arrested heart, which makes the surgical procedure significantly more complex. The sheep is a difficult model for aortic valve replacements due to its narrow annulus, short distance between the annulus and coronary ostia, a short ascending aorta, and difficulty in de-airing of the heart prior to suturing the aortotomy.19 Consequently, high on-table mortality rates, ranging from 9% to 33%, have been reported.1,18,21,24 Furthermore, the incidence of mortality during the first 30 d after surgery, directly related to the surgical procedure, is often high, ranging from 17% to 50%.1,2,16,18,21 Therefore, optimizing cardioprotective strategies during surgery would improve postoperative survival. However, little is known about protective strategies in sheep. In the current series of experiments, we implanted stented, tissue engineered, aortic heart valve prostheses in 20 adult domestic sheep and developed cardioprotective techniques to increase survival rates. In this observational study, we share our experience and insights regarding cardioprotective management to potentially improve the outcome of future surgeries that require an arrested heart in sheep. 相似文献
262.
Messenger RNA encoding the D2 dopaminergic receptor detected by in situ hybridization histochemistry in rat brain 总被引:1,自引:0,他引:1
A 30 base synthetic oligonucleotide probe was used to detect the mRNA encoding the rat D2 dopaminergic receptor. On Northern analysis, the probe identified a single species of mRNA of approximately 2.9 kb, present at highest levels in the striatum but also found in the brainstem, neocortex and diencephalon. On sections, neurons containing high levels of the mRNA were detected in the striatum, the substantia nigra pars compacta and the ventral tegmental area. Lower levels of signal were seen over neurons in the hypothalamus, the frontal neocortex, and the globus pallidus. 相似文献