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81.
Consistent Forcing Scheme in the Simplified Lattice Boltzmann Method for Incompressible Flows 下载免费PDF全文
Yuan Gao Liuming Yang Yang Yu Guoxiang Hou & Zhongbao Hou 《Communications In Computational Physics》2021,30(5):1427-1452
Considering the fact that the lattice discrete effects are neglected while introducing a body force into the simplified lattice Boltzmann method (SLBM), we propose
a consistent forcing scheme in SLBM for incompressible flows with external forces. The
lattice discrete effects are considered at the level of distribution functions in the present
forcing scheme. Consequently, it is more accurate compared with the original forcing
scheme used in SLBM. Through Taylor series expansion and Chapman-Enskog (CE)
expansion analysis, the present forcing scheme can be proven to recover the macroscopic Navier-Stokes (N-S) equations. Then, the macroscopic equations are resolved
through a fractional step technique. Furthermore, the material derivative term is discretized by the central difference method. To verify the results of the present scheme,
we simulate with multiple forms of external force interactions including the space- and
time-dependent body forces. Hence, the present forcing scheme overcomes the disadvantages of the original forcing scheme and the body force can be accurately imposed
in the present scheme even when a coarse mesh is applied while the original scheme
fails. Excellent agreements between the analytical solutions and our numerical results
can be observed. 相似文献
82.
Jan Buschbaum Linda Freitag Theodor F. Slongo Stephan Zeiter Michael Schütz Markus Windolf 《Journal of children's orthopaedics》2021,15(2):137
PurposeVarus-valgus deformities in children and adolescents are often corrected by temporary hemi-epiphysiodesis, in which the physis is bridged by an implant to inhibit growth. With standard implant solutions, the acting forces cannot be regulated, rendering the correction difficult to control. Furthermore, the implant load steadily increases with ongoing growth potentially leading to implant-related failures. A novel implant concept was developed applying a controlled constant force to the physis, which carries the potential to avoid these complications. The study aim was to proof the concept in vivo by analyzing the effect of three distinct force levels on the creation of varus deformities.MethodsThe proposed implant is made of a conventional cerclage wire and features a twisted coil that unwinds with growth resulting in an implant-specific constant force level. The proximal medial tibial physes of 18 lambs were treated with the implant and assigned to three groups distinct by the force level of the implant (200 N, 120 N, 60 N).ResultsThe treatment appeared safe without implant-related failures. Deformity creation was statistically different between the groups and yielded on average 10.6° (200 N), 4.8° (120 N) and 0.4° (60 N) over the treatment period. Modulation rates were 0.51°/mm (200 N), 0.23°/mm (120 N) and 0.05°/mm (60 N) and were constant throughout the treatment.ConclusionBy means of the constant force concept, controlled growth modulation appeared feasible in this preclinical experiment. However, clinical trials are necessary to confirm whether the results are translatable to the human pathological situation. 相似文献
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84.
目的研究血管粘弹性对脉动血流在(扌衮)法推拿作用下切应力的影响.方法建立具有局部轴向运动狭窄的粘弹性血管中脉动血流模型.设血液为牛顿流体,血管壁为线性粘弹体.在(扌衮)法推拿作用下血管受水平外力作用形成轴向运动缓变狭窄,血流遵循线化Navier-stokes方程.结果粘弹性血管在(扌衮)法作用下,距离血管入口z=31
cm处的平均切应力、最大切应力和瞬时切应力以及最大狭窄下游血管段最大切应力随着血管粘性系数和手法频率的改变而有较大变化.结论(扌衮)法推拿作用下粘弹性血管的血管切应力有显著变化,这与中医推拿的活血化淤相吻合. 相似文献
85.
一种肌电控制假手的新型自适应增力机构 总被引:2,自引:0,他引:2
介绍一种用于肌电控制假手的新型自适应切换增力机构。对比现在国内外的各种假手增力机构,它不用超越离合器,因而更为简单、可靠、耐用。它不仅为广大的上肢残疾患者带来福音,也是康复器械上的一大革新 相似文献
86.
目的研制能够抗剪切力的镍钛记忆合金髌骨爪,用于髌骨骨折的治疗。方法利用镍钛记忆合金的生物特性和髌骨的解剖特征以及髌骨骨折后膝关节活动时骨折端受力情况,设计一种符合髌骨解剖学特征和同时具有抗张力和抗剪切力的形态记忆髌骨爪。临床应用髌骨骨折41例。平均随访2.1年。结果抗剪切力记忆合金髌骨爪能够起到有效的生物固定,将记忆应力加压于骨折端,形成三唯记忆接骨,防止因骨折端产生的剪切力而出现髌骨上下错位,保证了膝关节的正常活动。骨折平均愈合时间为1.8月,关节活动度正常。结论抗剪切力镍钛记忆合金髌骨爪是治疗髌骨单纯骨折的一种有效的技术和方法。 相似文献
87.
Summary The central changes associated with a period of strength training have been investigated in a group of 32 young healthy volunteers. Subjects participated in one of three 12 week training programmes, which required different degrees of skill and coordination. Study 1 consisted of unilateral isometric training of the quadriceps with the contralateral leg acting as a control, the apparatus providing firm back support and a lap strap. In Study 2 training consisted of unilateral concentric leg-extension with back support and hand-grips. In Study 3 subjects performed bilateral leg-extension with no back support. Measurements of maximum voluntary isometric strength were made at 2–3 week intervals and a continual record was kept of the weights lifted in Studies 2 and 3. The largest increase in isometric force was seen for the trained leg in Study 1 (approximately 40%). There was no significant change in strength in the contralateral untrained leg. In Studies 2 and 3 there was a large increase in training weights (about 200%) associated with smaller increase in isometric force (15–20%). It is concluded that a large part of the improvement in the ability to lift weights was due to an increased ability to coordinate other muscle groups involved in the movement such as those used to stabilise the body. The importance of these findings for athletic training and rehabilitation is discussed. 相似文献
88.
89.
目的 探究Chevron截骨术截骨远端外侧位移距离对外翻足关节接触特征的影响,为临床上选择合适的位移距离提供参考依据。方法 测量踝关节中立位状态下正常足、外翻足及外翻足Chevron截骨术截骨远端分别向外侧位移2.0、4.0、6.0 mm后前足、中足和后足各关节接触力、峰值压强和接触面积,并对结果进行分析。结果 与正常足相比,外翻足第1跖楔关节(t=-3.33, P=0.02)、跟骰关节(t=-2.74, P=0.03)和距下关节(后关节面)(t=-2.89, P=0.03)的接触力显著增高;外翻足距舟关节(t=-2.73, P=0.03)与跟骰关节(t=-2.74, P=0.03)的峰值压强显著增高;行Chevron截骨术后,随着截骨远端向外侧位移距离的增加,外翻足第1跖楔关节和跟骰关节的接触力逐渐减小;外翻足距舟关节和跟骰关节的峰值压强逐渐减小。结论 中度外翻足行Chevron截骨术后,当第1跖骨截骨远端向外侧位移6 mm时能有效恢复部分关节间力的分布,且能缓解部分关节局部应力集中现象。 相似文献
90.
Van der Veen Jacoba Te Wierik Gerrit H. P. Van der Wal Liesbeth Eissens Anko C. Lerk Coenraad F. 《Pharmaceutical research》1994,11(4):499-502
Amylodextrin is a linear dextrin and can be produced by enzymatic hydrolysis of the -1,6 glycosidic bonds of amylopectin. Tablets compacted from pure amylodextrin showed good binding properties and did not disintegrate in aqueous media. Extended and decreasing drug release rates were found for tablets of 300 mg with a diameter of 9 mm containing 70% amylodextrin and 30% theophylline monohydrate, when compacted at 5 kN. Almost-constant drug release rates were obtained for these tablets when compacted at 10 or 15 kN. Nearly constant drug release rates were also shown for amylodextrin tablets with a drug load up to 75% compacted at 10 kN. Both release rate and release profile could be adjusted by selecting tablet thickness and incorporation of either lactose as a highly soluble excipient or talc as a hydrophobic excipient. 相似文献