全文获取类型
收费全文 | 44814篇 |
免费 | 3354篇 |
国内免费 | 1791篇 |
专业分类
耳鼻咽喉 | 378篇 |
儿科学 | 1410篇 |
妇产科学 | 304篇 |
基础医学 | 4665篇 |
口腔科学 | 189篇 |
临床医学 | 4521篇 |
内科学 | 3231篇 |
皮肤病学 | 81篇 |
神经病学 | 14209篇 |
特种医学 | 2997篇 |
外国民族医学 | 5篇 |
外科学 | 3203篇 |
综合类 | 5795篇 |
现状与发展 | 2篇 |
预防医学 | 1433篇 |
眼科学 | 174篇 |
药学 | 3639篇 |
13篇 | |
中国医学 | 1210篇 |
肿瘤学 | 2500篇 |
出版年
2024年 | 90篇 |
2023年 | 601篇 |
2022年 | 937篇 |
2021年 | 1652篇 |
2020年 | 1500篇 |
2019年 | 1388篇 |
2018年 | 1281篇 |
2017年 | 1430篇 |
2016年 | 1466篇 |
2015年 | 1548篇 |
2014年 | 2519篇 |
2013年 | 3207篇 |
2012年 | 2371篇 |
2011年 | 2486篇 |
2010年 | 2207篇 |
2009年 | 2003篇 |
2008年 | 2178篇 |
2007年 | 2234篇 |
2006年 | 2156篇 |
2005年 | 1891篇 |
2004年 | 1467篇 |
2003年 | 1446篇 |
2002年 | 1182篇 |
2001年 | 1049篇 |
2000年 | 822篇 |
1999年 | 766篇 |
1998年 | 684篇 |
1997年 | 762篇 |
1996年 | 618篇 |
1995年 | 520篇 |
1994年 | 542篇 |
1993年 | 389篇 |
1992年 | 402篇 |
1991年 | 339篇 |
1990年 | 309篇 |
1989年 | 296篇 |
1988年 | 294篇 |
1987年 | 246篇 |
1986年 | 318篇 |
1985年 | 381篇 |
1984年 | 384篇 |
1983年 | 254篇 |
1982年 | 321篇 |
1981年 | 271篇 |
1980年 | 242篇 |
1979年 | 132篇 |
1978年 | 96篇 |
1977年 | 79篇 |
1976年 | 69篇 |
1975年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
磁共振成像对颅内脑膜瘤水肿分析 总被引:1,自引:0,他引:1
目的:探讨脑膜瘤周围脑水肿的程度和肿瘤的生长部位.质地.组织学亚型的相关性.研究其瘤周水肿的形成原因.材料和方法:使用经手术和病理证实的65例脑膜瘤MRI和临床病理资料.观察分析脑膜瘤的瘤周水肿的程度.肿瘤的质地,组织学亚型等.结果:发生于大脑颅盖部或/和有矢状窦受累的脑膜瘤有明显的脑水肿.而发生于其它部位(颅底,丘脑、小脑、脑池等)无或只有轻度脑水肿.结论:轻度脑水肿主要是脑膜瘤对脑组织的直接压迫,而中,重度脑水肿主要是脑膜瘤对大脑表面引流静脉尤其是矢状窦的压迫或阻塞.脑水肿和肿瘤的发生部位有关,面和肿瘤的质地、组织学亚型无关. 相似文献
82.
D. McCormick 《Neuropathology and applied neurobiology》1993,19(2):146-151
There is evidence from investigations of non-CNS neoplasms that secreted proteolytic enzymes may facilitate tumour invasion by partially degrading extracellular matrix (ECM). Among the enzymes which may be involved are members of the cysteine proteinase superfamily and especially cathepsin B (CB). In the present investigation we have studied CB in human gliomas in vitro , concentrating particularly on CB secretion, as extracellular enzyme is of prime importance in this context. We have found that CB is secreted by gliomas in vitro as a latent zymogen, requiring activation. This has been confirmed by gel chromatography which indicated that CB is secreted as a 42 kDa proenzyme which may be proteolytically processed to an enzymatically active 29 kDa molecule. The inactive, high molecular weight, latent CB is stable at extracellular pH in contrast to the activated low molecular weight form which rapidly loses activity at this pH. We have also measured secretion of cysteine proteinase inhibitors (CPI), as their presence would have a direct influence on the effective activity of CB, and found that all of the gliomas secreted significant amounts of a CPI as assessed by papain inhibition. Our experiments suggest that a number of factors are involved in the regulation of extracellular glioma-derived CB activity. These include: rate of secretion of pro-CB, rate of CB activation, destabilization of CB at neutral pH and the presence of cysteine proteinase inhibitors. 相似文献
83.
Dr. J. Tajti MD PhD ; Dr. K. Sas MD ; Dr. D. Szok MD ; Dr. E. Vörös MD ; Dr. L. Vécsei MD DSc 《Headache》1996,36(4):259-260
We report on a patient with clusterlike headache and multiple brain metastases of lung cancer. Initially, cluster headache was suggested clinically by characteristic symptoms without any focal central nervous system signs. However, magnetic resonance imaging demonstrated multiple brain metastases. It is possible that tumor necrosis factor may have played a role in initiating the clusterlike headache. 相似文献
84.
Effects of Ethanol in an Experimental Model of Combined Traumatic Brain Injury and Hemorrhagic Shock 总被引:3,自引:2,他引:1
Brian J. Zink MD Susan A. Stern MD Xu Wang MD Carl C. Chudnofsky MD 《Academic emergency medicine》1998,5(1):9-17
Objectives: Given that clinical and laboratory studies suggest that ethanol and hemorrhagic shock (HS) potentiate traumatic brain injury (TBI), the authors studied the effects of ethanol in a model of combined TBI and HS.
Methods: A controlled porcine model of combined TBI and HS was evaluated for the effect of ethanol on survival time, hemodynamic function, and cerebral tissue perfusion. Anesthetized swine (17–24 kg) were instrumented, splenectomized, and subjected to fluid percussion TBI with concurrent 25-mL/kg graded hemorrhage over 30 minutes. Two groups were studied: control ( n = 11) and ethanol ( n = 11). Ethanol, 3.5 g/kg intragastric, was given 100 minutes prior to TBI/HS. Systemic and cerebral physiologic and metabolic parameters were monitored for 2 hours without resuscitation. Regional cerebral blood flow (rCBF) and renal blood flow were measured with dye-labeled microspheres. Data were analyzed with 2-sample t-test and repeated-measures ANOVA.
Results: Ethanol levels at the time of injury were 162 ± 68 mg/dL. Average TBI was 2.65 ± 0.35 atm. Survival time was significantly shorter in the ethanol group (60 ± 27 min vs 94 ± 28 min, p = 0.011). The ethanol group had significantly lower mean arterial pressure, cerebral perfusion pressure, and cerebral venous
O2 saturation in the postinjury period. Cerebral O2 extraction ratios and cerebral venous lactate levels were significantly higher in the ethanol group. A trend toward lower postinjury rCBF in all brain regions was observed in the ethanol group.
Conclusion: In this TBI/HS model, ethanol administration decreased survival time, impaired the hemodynamic response, and worsened measures of cerebral tissue perfusion. 相似文献
Methods: A controlled porcine model of combined TBI and HS was evaluated for the effect of ethanol on survival time, hemodynamic function, and cerebral tissue perfusion. Anesthetized swine (17–24 kg) were instrumented, splenectomized, and subjected to fluid percussion TBI with concurrent 25-mL/kg graded hemorrhage over 30 minutes. Two groups were studied: control ( n = 11) and ethanol ( n = 11). Ethanol, 3.5 g/kg intragastric, was given 100 minutes prior to TBI/HS. Systemic and cerebral physiologic and metabolic parameters were monitored for 2 hours without resuscitation. Regional cerebral blood flow (rCBF) and renal blood flow were measured with dye-labeled microspheres. Data were analyzed with 2-sample t-test and repeated-measures ANOVA.
Results: Ethanol levels at the time of injury were 162 ± 68 mg/dL. Average TBI was 2.65 ± 0.35 atm. Survival time was significantly shorter in the ethanol group (60 ± 27 min vs 94 ± 28 min, p = 0.011). The ethanol group had significantly lower mean arterial pressure, cerebral perfusion pressure, and cerebral venous
O
Conclusion: In this TBI/HS model, ethanol administration decreased survival time, impaired the hemodynamic response, and worsened measures of cerebral tissue perfusion. 相似文献
85.
Sources of P300 attenuation after head injury: Single-trial amplitude, latency jitter, and EEG power
Single trial amplitude, latency jitter, and electroencephalographic (EEG) power were examined as sources of the group difference in averaged P300 amplitude among 15 traumatically brain injured and 20 control individuals in an auditory oddball paradigm. Mean amplitude of the individual trials was highly correlated with the amplitude of the averaged P300, with little additional unique variance attributable to latency jitter or EEG power. The group difference in P300 amplitude was also explained by the mean amplitude of the single trials. These results support the robustness of the event-related potential averaging technique within the paradigm used. 相似文献
86.
Intracranial actinomycosis in juvenile patients
Case report and review of the literature 总被引:1,自引:0,他引:1
F. Puzzilli Maurizio Salvati Andrea Ruggeri Antonino Raco Roberto Bristot Stefano Bastianello Pierpaolo Lunardi 《Child's nervous system》1998,14(9):463-466
A case of actinomycotic brain infection in a juvenile patient is described. Cases of actinomycosis affecting the head and
neck are rare, particularly in juvenile patients. In this case complete resolution of the infection was achieved by means
of surgical treatment and prolonged antibiotic therapy. The authors emphasize the importance of a combined approach for treatment
of this unusual brain infection and stress the difficulties involved in the diagnosis of this pathology.
Received: 3 November 1997 相似文献
87.
目的:从牛脑中分离纯化酸性成纤维细胞生长因子(aFGF)并鉴定生物活性,方法:根据DenisGOSPODAROW-ICZ的方法,新鲜牛脑匀浆,三步硫酸铵盐析。最后沉淀物溶解透析后予离子交换层析及琼脂糖胶亲和层析,促3T3细胞DNA合成率鉴定生物活性。结果:用1.0mol/LNaCl的缓冲液洗脱得到分子量为13600的多肽,得率为610μg/kg牛脑,氨基酸组成分析与已知的aFGF相同,促3T3细胞DNA合成的最低浓度为0.5ng/ml,最大效应浓度50ng/ml,ED50值为8ng/ml。结论:aFGF具有强烈的促细胞增殖作用。 相似文献
88.
D. Novitzky J. Rhodin D.K.C. Cooper Y. Ye K.-W. Min L. DeBault 《Transplant international》1997,10(1):24-32
Abstract Electromicroscopic examinations were carried out on 30 myocardial biopsies taken from 22 human donor hearts immediately after excision (prestorage) or immediately before transplantation (post-storage). All electron micrographs were independently examined by two morphologists. Eleven structures were examined in each micrograph, and each structure was scored according to the degree of injury. A good interobserver correlation was obtained in 84 % of the structures scored. In the prestorage left ventricular biopsies ( n = 11), approximately 20 %-25 % showed moderate to severe ultrastructural injury. The ultrastructural injury observed in the poststorage left ventricular biopsies ( n = 15) was no different from that in the prestorage group, particularly injury to the sarcomere and mitochondria. A similar degree and pattern of injury was seen in the right ventricle ( n = 4). There was no evidence that an ischemic storage period of less than 6 h increased the degree of injury seen. However, there was a higher incidence of moderate to severe injury in those hearts excised from donors initially dependent on high inotropic support. 相似文献
89.
3-Methoxytyramine (3-MT) is a minor metabolite of dopamine which is suggested to reflect the turnover and utilization of dopamine. A novel, isocratic HPLC method has been developed which can be used to analyse 3-MT in homogenates of rat brain without the need for additional purification procedures. Furthermore, the coulometric electrochemical detection system is sensitive enough to measure 3 pg of 3-MT (equivalent to 0.6 ng/g tissue wet weight). 3-Methoxytyramine was measured in the striatum and n. accumbens after decapitation and rapid freezing, using 3-methoxy-4-hydroxybenzylamine as the internal standard. The effects of dopaminergic and other drugs on this metabolite were examined using this method. -Methyl-p-tyrosine (200 mg/kg i.v.) produced parallel linear decreases in dopamine and 3-MT in naive rats, but not those pretreated with tranylcypromine (5 mg/kg i.p.). Methamphetamine (0.3–10 mg/kg i.p.) and amphetamine (0.3–10 mg/kg i.p.) both dose-dependently increased 3-MT in naive and tranylcypromine-pretreated rats. In naive animals, 3-MT was not altered by intraperitoneal injection of the dopamine reuptake inhibitors, bupropion (10 mg/kg) and nomifensine (10 mg/kg) or by sibutramine HCl (3 mg/kg), amitriptyline (10 mg/kg), desipramine (10 mg/kg) and zimeldine (10 mg/kg). 3-Methoxy-tyramine was decreased by apomorphine (5 mg/kg i.p.) and also by large doses of the selective D2 antagonist, BRL 34778 (5 mg/kg i.p.) or
-DOPA (50 mg/kg i.p.). The selective D1 antagonist, SCH 23390 (0.1 or 5 mg/kg i.p.) was without effect. In tranylcypromine-pretreated rats, 3-MT was dose-dependently reduced and increased by apomorphine (0.01–5 mg/kg i.p.) and BRL 34778 (0.1–5 mg/kg i.p.), respectively. The drug SCH 23390 (0.1–5 mg/kg i.p.) produced much smaller increases in 3-MT which were probably mediated through the striatonigral pathway. Overall, the data suggest that measurement of 3-MT, after inhibition of monoamine oxidase, is a useful index of the release and utilization of dopamine. However, after substantial and prolonged depletion of dopamine, levels of 3-MT in naive animals are a better index. Also, the formation of 3-MT in naive rats provides a sensitive method for distinguishing between dopamine releasing agents and reuptake inhibitors. 相似文献
90.
Summary 67 cases of brain abscess were analyzed retrospectively. As 2 comatose patients died on admission before any treatment was started, the results are based on 65 treated patients. Different methods of treatment included: total removal in 36 patients, drainage in 14, aspiration in 6 and conservative treatment in 9. Management mortality was 18,5% and was almost not dependent on the method of treatment (except aspiration) being lowest in the drainage group. The mortality was significantly higher in patients with serious impairment of consciousness on admission.Follow-up examination after 1 to 11 years was performed in 47 out of 53 discharged patients and revealed in 25 of them (53%) full recovery. 10 additional cases (21%) are independent. The best early and long term results were obtained in patients by drainage and medical treatment.Chronic epilepsy developed in 34% of patients with supratentorial lesions. The risk of epilepsy was lowest in the group of patients treated by drainage.The authors present the opinion that removal of brain abscess is necessary only in exceptional cases. 相似文献