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81.
Isha Jain Christine Stroka Jianying Yan Wei-Min Huang M Kathryn Iovine 《Developmental dynamics》2007,236(9):2668-2674
Fin length in the zebrafish is achieved by the distal addition of bony segments of the correct length. Genetic and molecular data provided evidence that segment growth uses a single pulse of growth, followed by a period of stasis. Examination of cell proliferation during segment growth was predicted to expose a graphical model consistent with a single burst of cell division (e.g., constant, parabolic, or exponential decay) during the lengthening of the distal-most segment. Cell proliferation was detected either by labeling animals with bromodeoxyuridine (during S-phase) or monitoring histone3-phosphate (mitosis). Results from both methods revealed that the number of proliferating cells fluctuates in apparent pulses as a segment grows (i.e., during the growth phase). Thus, rather than segment size being the result of a single burst of proliferation, it appears that segment growth is the result of several pulses of cell division that occur approximately every 60 microns (average segment length approximately 250 microns). These results indicate that segment lengthening requires multiple pulses of cell proliferation. 相似文献
82.
目的探讨全髋关节置换术均衡双下肢长度的临床意义和手术设计。方法回顾分析2000-2004年获得随访的单侧全髋关节置换手术病例48例,采用骨水泥型假体12髋,混合型假体36髋,术前双下肢等长30例(含股骨颈骨折患者),10例患肢长度短缩1.0-2.0cm,6例短缩2.0-4.0cm,2例短缩4.0-6.0cm。通过术前肢体长度测量及X片测量制定手术方案,选择假体、预估颈长和截骨平面;术中正确磨削髋臼,寻找最佳旋转中心,结合透视及特殊试验修正截骨平面,调节假体颈长,达到均衡双下肢长度的目的。结果全部病例采用Harris评分,优30例,良12例,中4例,差2例。术前等长30例巾术后出现5例手术侧延长1.0-2.0cm,1例延长2.5cm。术前不等长的18例中,术后恢复等长10例,6例手术侧延长1.0-2.0cm,2例术前重度短缩的先天性髋关节发育不良病人术后仍然短缩2.0-3.0cm。术后肢体等长35例Harris评分平均92.3分,术后肢体不等长13例Harris评分平均88.6分。结论全髋关节置换术的手术设计。手术技巧以及假体设计等诸多因素影响下肢长度,术后肢体不等长降低了患者的满意度。应重视术前测量及术中综合评价方法的运用,重视软组织平衡技术和肢长调节,掌握全髋置换术中均衡下肢长度的手术技术,进一步改善手术效果。 相似文献
83.
OLAV STOKLAND J
RGEN THORVALDSON ARNFINN ILEBEKK FREDRIK KIIL 《Acta physiologica (Oxford, England)》1983,117(4):481-489
To examine the factors contributing to the rise in systemic blood pressure during α- and β- adrenergic stimulation, phenylephrine, an α-adrenergic agonist, and norepinephrine, an α- and β-adrenergic agonist, were infused intravenously to anesthetized dogs until mean aortic blood pressure was raised equally by 40–60 mmHg. Changes in preload were estimated by changes in left ventricular end-diastolic pressure or segment length recorded by an ultrasonic technique. By obstructing the inferior vena cava (IVC), the increase in preload could be reduced to control level during phenylephrine and norepinephrine infusions without altering peripheral resistance (mean aortic blood pressure/cardiac output). Normalization of preload reduced the pressure response by 2/3 during phenylephrine infusion and by 1/4 during norepinephrine infusion. However, after β-adrenergic blockade by propranolol, normalization of preload reduced the pressure response by 2/3 during both phenylephrine and norepinephrine infusions. Thus, during α-adrenergic stimulation, the increase in preload is a more important factor than the increase in peripheral resistance. Norepinephrine raised stroke volume by 24±5%. When the increase in stroke volume was prevented by IVC obstruction, the pressure response to norepinephrine was halved. Thus, during norepinephrine infusion the rise in stroke volume caused by β-adrenergic stimulation is as important as α-adrenergic stimulation for the pressure response. 相似文献
84.
Chemical neuromodulation of frontal-executive functions in humans and other animals 总被引:20,自引:0,他引:20
Robbins TW 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2000,133(1):130-138
Neuromodulation of frontal-executive function is reviewed in the context of experiments on rats, monkeys and human subjects. The different functions of the chemically identified systems of the reticular core are analysed from the perspective of their possible different interactions with the prefrontal cortex. The role of dopamine in spatial working memory is reviewed, taking account of its deleterious as well as facilitatory effects. Baseline-dependent effects of dopaminergic manipulation are described in rats on an attentional task, including evidence of enhanced function following infusions of D1 receptor agonists into the prefrontal cortex. The precise nature of the cognitive task under study is shown to be a powerful determinant of the effects of mesofrontal dopamine depletion in monkeys. Parallels are identified in human subjects receiving drugs such as the indirect catecholamine agonists L-dopa, methylphenidate and the dopamine D2 receptor blocker sulpiride. The effects of these drugs on different types of cognitive function sensitive to frontal lobe dysfunction are contrasted with those of a manipulation of 5-HT function, dietary tryptophan depletion. Hypotheses are advanced that accord the ascending systems a greater deal of specificity in modulating prefrontal cortical function than has hitherto been entertained, and clinical and theoretical implications of this hypothesis are discussed. 相似文献
85.
学习障碍儿童记忆的比较研究 Ⅰ.学习障碍儿童的短时记忆和工作记忆 总被引:8,自引:0,他引:8
目的:考查学习障碍儿童的短时记忆和工作记忆及各型学习障碍儿童短时记忆特征,比较短时记忆和工作记忆对学习的相对贡献。方法:根据儿童的学科成绩、智力水平、教师对学习能力的评定,结合临床观察,从三所小学1564名学生中筛查出学习障碍儿童97人(男71人,女26人),正常学习儿童63人(男36,女27人),并根据主要困难所在把学习障碍儿童分为三组:语文障碍(31人)、数学障碍(21人)和混合型障碍(45人)。对每个入组儿童作个别记忆测查,内容包括短时记忆(数字、汉词和符号)和工作记忆(数字、汉词、符号、故事)。结果:混合型障碍的短时记忆和工作记忆均低于对照组,语文障碍对言语材料的短时记忆和工作记忆中的故事理解低于对照组,数学障碍仅言语材料的短时记忆低于对照组;三型学习障碍之间仅在数字广度和故事Ⅱ阅读理解二项任务上有差异;短时记忆和工作记忆与学习成绩均有中度相关,工作记忆与数学成绩的相关更高。结论:学习障碍儿童存在共同的短时记忆和工作记忆缺陷,但缺陷程度有差异,这种缺陷可能与言语编码缺陷或记忆系统本身功能障碍有关。 相似文献
86.
S. A. Brandt Christoph J. Ploner Bernd-Ulrich Meyer Stefanie Leistner Arno Villringer 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,118(2):197-204
We investigated the role of the dorsolateral prefrontal cortex (DLPFC) and the posterior parietal cortex (PPC) in a visuospatial
delayed-response task in humans. Repetitive transcranial magnetic stimulation (20 Hz, 0.5 s) was used to interfere temporarily
with cortical activity in the DLPFC and PPC during the delay period. Omnidirectional memory-guided saccades with a 3-s delay
were used as a quantifiable motor response to a visuospatial cue. The question addressed was whether repetitive transcranial
magnetic stimulation (rTMS) over the DLPFC or PPC during the sensory of memory phase affects accuracy of memory-guided saccades.
Stimulation over the primary motor cortex served as control. Stimulation over the DLPFC significantly impaired accuracy of
memory-guided saccades in amplitude and direction. Stimulation over the PPC impaired accuracy of memory-guided saccades only
when applied within the sensory phase (50 ms after cue offset), but not during the memory phase (500 ms after cue offset).
These results provide further evidence for a parieto-frontal network controlling performance of visuospatial delayed-response
tasks in humans. It can be concluded that within this network the DLPFC is mainly concerned with the mnemonic respresentation
and the PPC with the sensory representation of spatially defined perceptual information.
Received: 22 April 1996/Accepted: 16 June 1997 相似文献
87.
The purpose of the study was to investigate the characteristics of shock attenuation during high-speed running. Maximal running
speed was identified for each subject [n=8 males, 25 (SD 4.6) years; 80 (8.9) kg; 1.79 (0.06) m] as the highest speed that could be sustained for about 20 s on a
treadmill. During testing, light-weight accelerometers were securely mounted to the surface of the distal antero-medial aspect
of the leg and frontal aspect of the forehead. Subjects completed running conditions of 50, 60, 70, 80, 90, and 100% of their
maximal speeds with each condition lasting about 20 s. Stride length, stride frequency, leg and head peak impact acceleration
were recorded from the acceleration profiles. Shock attenuation was analyzed by extracting specific sections of the acceleration
profiles and calculating the ratio of head to leg power spectral densities across the 10–20 Hz frequency range. Both stride
length and stride frequency increased across speeds (P<0.05) and were correlated with running speed (stride length r=0.92, stride frequency r=0.89). Shock attenuation increased about 20% per m·s–1 across speeds (P<0.05), which was similar to the 17% increase in stride length per m·s–1. Additionally, shock attenuation was correlated with stride length (r=0.71) but only moderately correlated with stride frequency (r=0.40) across speeds. It was concluded that shock attenuation increased linearly with running speed and running kinematic
changes were characterized primarily by stride length changes. Furthermore, the change in shock attenuation was due to increased
leg not head peak impact acceleration across running speeds.
Electronic Publication 相似文献
88.
Summary Previous papers gave some methods for the reliable measurement of the tibia-calcaneum angle. It is of common use to evaluate the physical properties of triceps surae on the basis of torque-angle curves. However this method is reliable only if each tibia-calcaneum angle corresponds to a defined distance between the insertions of the muscle in subjects of the same height. Evidence is given by radiological measurements that this correspondance is correct in normal children. However, this is no longer true in certain cerebral palsied children because of abnormal translation of the calcaneum and/or abnormal ratio of bone sizes. In this case the torque-angle curves do not define properly the torque-length curves. A method of correction is given. This correction may be as high as 15.MaÎtre de Recherche INSERM (Paris), grant No. 7411766 and U.E.R. Paris-Ouest 相似文献
89.
乙/丙型肝炎病毒双重感染患者前C区终止变异低频率 总被引:1,自引:0,他引:1
目的了解乙型肝炎病毒(HBV)与丙型肝炎病毒(HCV)双重感染患者前C区基因变异,及其可能的临床意义。方法用聚合酶链反应(PCR)与限制片段长度多态性(RFLP)来分析25例HBVDNA和HCVRNA均阳性(A组)和31例HBsAg和HBVDNA阳性但抗-HCV和HCVRNA均阴性(B组)的慢性肝病患者前C区密码28终止变异(终28)。结果HBV和HCV双重感染患者(A组)血清HBVDNA第1次PCR阳性率(16%)明显低于单独HBV感染组(65%)(P<0.001);前C终28检出率(28%)亦明显低于单独HBV感染(68%)(P<0.001)。结论提示双重感染患者HBV前C终止变异低频率可能与HBV低水平复制有关 相似文献
90.
Huang W Sher YP Delgado-West D Wu JT Peck K Fung YC 《Annals of biomedical engineering》2001,29(7):535-551
The remodeling of the pulmonary arterial tissue in response to a step change of the oxygen concentration in the gas in which a rat lives was recorded as function of time and function of O2 concentration. Three steps of changing from 20.9% to 17.2%, 13.6%, and 10% O2 were imposed. Earlier work in our laboratory has shown that pulmonary arterial tissue remodeling is significant in the first 24 h after a step change of oxygen tension. Hence we made measurements in this period. Furthermore, data were obtained for tissue remodeling of circumferential and axial lengths of the pulmonary arteries. We recorded the activities of gene expressions in the lung tissues by microarray, determined the dose response curves of gene expression in the homogenized whole lungs with respect to four levels of O2 concentration, and obtained the time courses of gene expression in the lung parenchyma in 30 days after a step decrease of O2 concentration from 20.9% to 10%. We would like to suggest that the correlation of gene expression with physiological function parameters, i.e., time, O2 tension, blood pressure, opening angle, wall thicknesses, etc., is the way to narrow down the search for specific genes for specific physiological functions. © 2001 Biomedical Engineering Society.
PAC01: 8719Uv 相似文献