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51.
52.
Max Chacn Hector Rojas-Pescio Sergio Pealoza Jean Landerretche 《Entropy (Basel, Switzerland)》2022,24(3)
The mechanism of cerebral blood flow autoregulation can be of great importance in diagnosing and controlling a diversity of cerebrovascular pathologies such as vascular dementia, brain injury, and neurodegenerative diseases. To assess it, there are several methods that use changing postures, such as sit-stand or squat-stand maneuvers. However, the evaluation of the dynamic cerebral blood flow autoregulation (dCA) in these postures has not been adequately studied using more complex models, such as non-linear ones. Moreover, dCA can be considered part of a more complex mechanism called cerebral hemodynamics, where others (CO2 reactivity and neurovascular-coupling) that affect cerebral blood flow (BF) are included. In this work, we analyzed postural influences using non-linear machine learning models of dCA and studied characteristics of cerebral hemodynamics under statistical complexity using eighteen young adult subjects, aged 27 ± 6.29 years, who took the systemic or arterial blood pressure (BP) and cerebral blood flow velocity (BFV) for five minutes in three different postures: stand, sit, and lay. With models of a Support Vector Machine (SVM) through time, we used an AutoRegulatory Index (ARI) to compare the dCA in different postures. Using wavelet entropy, we estimated the statistical complexity of BFV for three postures. Repeated measures ANOVA showed that only the complexity of lay-sit had significant differences. 相似文献
53.
Alvaro Valencia Darren Ledermann Rodrigo Rivera Eduardo Bravo Marcelo Galvez 《国际流体数值方法杂志》2008,58(10):1081-1100
Hemodynamics plays an important role in the progression and rupture of cerebral aneurysms. The current work describes the blood flow dynamics and fluid–structure interaction in seven patient‐specific models of bifurcating cerebral aneurysms located in the anterior and posterior circulation regions of the circle of Willis. The models were obtained from 3D rotational angiography image data, and blood flow dynamics and fluid–structure interaction were studied under physiologically representative waveform of inflow. The arterial wall was assumed to be elastic, isotropic and homogeneous. The flow was assumed to be laminar, non‐Newtonian and incompressible. In one case, the effects of different model suppositions and boundary conditions were reported in detail. The fully coupled fluid and structure models were solved with the finite elements package ADINA. The vortex structure, pressure, wall shear stress (WSS), effective stress and displacement of the aneurysm wall showed large variations, depending on the morphology of the artery, aneurysm size and position. The time‐averaged WSS, effective stress and displacement at the aneurysm fundus vary between 0.17 and 4.86 Pa, 4.35 and 170.2 kPa and 0.16 and 0.74 mm, respectively, for the seven patient‐specific models of bifurcating cerebral aneurysms. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
54.
Flow dynamics plays an important role in the pathogenesis and treatment of cerebral aneurysms. The temporal and spatial variations of wall shear stress in the aneurysm are hypothesized to be correlated with its growth and rupture. In addition, the assessment of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils. This work describes the flow dynamics in a patient‐specific model of carotid artery with a saccular aneurysm under Newtonian and non‐Newtonian fluid assumptions. The model was obtained from three‐dimensional rotational angiography image data and blood flow dynamics was studied under physiologically representative waveform of inflow. The three‐dimensional continuity and momentum equations for incompressible and unsteady laminar flow were solved with a commercial software using non‐structured fine grid with 283 115 tetrahedral elements. The intra‐aneurysmal flow shows complex vortex structure that change during one pulsatile cycle. The effect of the non‐Newtonian properties of blood on the wall shear stress was important only in the arterial regions with high velocity gradients, on the aneurysmal wall the predictions with the Newtonian and non‐Newtonian blood models were similar. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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56.
用精制蝮蛇抗栓酶(Svate-3)治疗了108例急性期脑血栓形成病人,治疗前后分别测定病人血清微量元素锌、铜、铬、锰、硒及体液免疫指标 IgG, IgA, IgM及循环免疫复合物(CIC), 同时设定对照组观察 Svate-3的临床疗效.观察结果表明,治疗组疗效优于对照组.测定结果表明,Svate-3能使脑血栓病人血清 Zn增加(P<0.05),血清 Cu减少(P<0.05 ), Zn/Cu比值增加(P<0.05),Svate-3可使体液免疫 IgA增加(P<0.01) . 相似文献
57.
GE Peng-fei LIU Bin FAN Wen-hai LI Shu-lei YANG Fu-wei LUO Yi-nan ZHANG Ping 《高等学校化学研究》2011,(2):249-253
Proteasome activity reduction is an important pathological phenomenon, resulting in proteins aggregation and neuronal death in the injured neurons induced by transient ischemia. Our previous report showed that the trap of proteasome in the protein aggregates was a reason to lead to the reduction of proteasome activity. However, the patterns of proteasome entered into protein aggregates are not clear. In this study, we used a global ischemia model, Hematoxylin-Eosin staining, differential centrifuge, proteas... 相似文献
58.
《Analytical letters》2012,45(5):395-405
Abstract Creatine kinase serum enzymes were separated by low pressure liquid chromatography with a Glycophase DEAE column. The separated MB creatine kinase isozyme was assayed by measurinq the amount of ATP formed from ADP and creatine phosphate in the presence of the enzyme. High performance 1iquid chromatography was used to determine ATP. 相似文献
59.
Sung Won Youn Ho Kyun Kim Hong Tae Kim Sung Mi Han Jin Kuk Do Young Rok Do Hui Joong Lee Jongmin Lee Jae Hong Lim 《Journal of synchrotron radiation》2014,21(1):215-222
Phase‐contrast synchrotron X‐ray microtomography (pcSyncX) based on the highly coherent X‐ray beam has previously been used to visualize the microstructures of biologic specimens, but it has never been used to evaluate embolic debris adherent on a cerebral protection device (CPD). The purpose of this study was to demonstrate the feasibility of pcSyncX for evaluating embolic debris during carotid artery stenting (CAS). Five patients (four males, age range 67–77 years) with severe carotid artery stenosis underwent CAS. The retrieved CPD was exposed to synchrotron radiation and 1000 pcSyncX projection images were obtained by rotating the CPD through 180°. An X‐ray shadow of a CPD was converted into a visual image by the scintillator. After microtomographic reconstruction, the three‐dimensionally reconstructed images were further segmented into the embolic debris and CPD. The total volume of emboli was calculated by summing the volume at each scanning level. The number of membrane pores covered by emboli as seen from the outer surface was counted and the percentage of covered area was calculated. Embolic debris was clearly demonstrated not only on the inner surface and within pores but also on the outer surface of the CPD. The mean total volume of embolic debris was 0.538 × 10–6 mm3 (range 0.225–0.965 × 10–6 mm3). Most (61.5%) of the debris was located at the apical one‐third of the CPD and 20.8% of the pore area was covered by debris. 相似文献
60.
Baimei Shi Qiannan Li Ying Feng Xufen Dai Rui Zhao Ye Zhao Pu Jia Shixiang Wang Jie Yu Sha Liao Yi‐fei Li Xiaohui Zheng 《Journal of separation science》2020,43(2):531-546
As a representative formulation of Radix Salviae miltiorrhizae (Danshen)‐Lignum Dalbergiae odoriferae (Jiangxiang), Xiangdan injection is widely prescribed for cardio‐ and cerebrovascular diseases in practice. This necessitates a pharmacokinetic investigation of this formulation to make it safer and more broadly applicable. We developed and validated a sensitive, selective, and reliable high‐performance liquid chromatography with tandem mass spectrometry method for the simultaneous determination of 11 phenolic compounds including danshensu plus two diterpenoid quinones like cryptotanshinone and tanshinone IIA in rat. We applied this method for the pharmacokinetic studies of the 13 compounds in a rat model of middle cerebral artery occlusion after intravenous injection of Xiangdan injection or Danshen injection. In sham‐operated rats, the animals taking Xiangdan injection exhibited significant growth of the area under the curve for danshensu, protocatechuic aldehyde, and tanshinone IIA compared with the changes seen in the data of those administrated with Danshen injection. Such a pattern was also observed in middle cerebral artery occlusion rats, whereas increased the area under the curve values were observed for danshensu, protocatechuic aldehyde, caffeic acid, rosmarinic acid, and tanshinone IIA. These results demonstrated that synergistic interactions occurred between the components of Danshen and the active compounds of Jiangxiang both in sham‐operated and middle cerebral artery occlusion rats, increasing the bioavailability of Danshen. The results presented herein can be used to determine a reference dose for the clinical application of Xiangdan injection, and to elucidate the synergistic mechanism of Danshen and Jiangxiang. 相似文献