全文获取类型
收费全文 | 11148篇 |
免费 | 927篇 |
国内免费 | 329篇 |
专业分类
耳鼻咽喉 | 29篇 |
儿科学 | 222篇 |
妇产科学 | 60篇 |
基础医学 | 1132篇 |
口腔科学 | 326篇 |
临床医学 | 873篇 |
内科学 | 1158篇 |
皮肤病学 | 159篇 |
神经病学 | 1168篇 |
特种医学 | 1713篇 |
外科学 | 709篇 |
综合类 | 986篇 |
预防医学 | 886篇 |
眼科学 | 89篇 |
药学 | 1933篇 |
中国医学 | 707篇 |
肿瘤学 | 254篇 |
出版年
2024年 | 11篇 |
2023年 | 126篇 |
2022年 | 175篇 |
2021年 | 430篇 |
2020年 | 297篇 |
2019年 | 331篇 |
2018年 | 343篇 |
2017年 | 364篇 |
2016年 | 406篇 |
2015年 | 445篇 |
2014年 | 767篇 |
2013年 | 697篇 |
2012年 | 742篇 |
2011年 | 866篇 |
2010年 | 688篇 |
2009年 | 634篇 |
2008年 | 650篇 |
2007年 | 594篇 |
2006年 | 494篇 |
2005年 | 496篇 |
2004年 | 378篇 |
2003年 | 334篇 |
2002年 | 253篇 |
2001年 | 222篇 |
2000年 | 173篇 |
1999年 | 126篇 |
1998年 | 131篇 |
1997年 | 133篇 |
1996年 | 113篇 |
1995年 | 151篇 |
1994年 | 149篇 |
1993年 | 119篇 |
1992年 | 79篇 |
1991年 | 56篇 |
1990年 | 58篇 |
1989年 | 43篇 |
1988年 | 33篇 |
1987年 | 31篇 |
1986年 | 27篇 |
1985年 | 34篇 |
1984年 | 38篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
《Brain & development》2020,42(3):307-310
We report a case of a 22-month-old Spanish girl who presented acute encephalopathy with biphasic seizures and late reduced diffusion (AESD). Serum procalcitonin (PCT) reached a maximum of 50.5 ng/mL on the first day whereas C-reactive protein (CRP) peaked at 1.21 mg/dL on the second. At the time of discharge, right spastic hemiparesis persisted. MR spectroscopy on day 23 revealed a decrease in N-acetylaspartate and an increase in choline. To our knowledge, we report the first case of AESD in Europe. These findings support the role of PCT and PCT/CRP ratio in the early diagnosis of AESD and correlation of MR spectroscopy findings with neurological outcome. 相似文献
32.
《Brain & development》2020,42(10):767-770
MR spectroscopy in a patient with hyponatremic encephalopathy due to the syndrome of inappropriate secretion of antidiuretic hormone revealed decreased N-acetyl-aspartate, creatine plus phosphocreatine, choline-containing compounds, and myo-inositol, with normal glutamate and increased glutamine, which normalized after Na normalization. The decreased concentrations of creatine plus phosphocreatine, choline-containing compounds and myo-inositol are explained by their release as osmolytes from brain cells to adapt to hypo-osmolality induced cerebral edema. Increased glutamine, which not only acts as an osmolyte but also protects neurons under excitotoxic conditions, may suggest that a disrupted glutamate-glutamine cycle may play an important role in the pathogenesis of hyponatremic encephalopathy. 相似文献
33.
34.
Francesca Zoratto Clelia Buccheri Romina Mura Luisa Altabella Marion Vanneste Marie Villotte Giovanni Laviola Francois Dauphin Eleni Paizanis Walter Adriani Rossella Canese 《Synapse (New York, N.Y.)》2020,74(4):e22138
We aimed at the further characterization of rats in which SERT gene silencing was achieved by hippocampal injection of a lentiviral vector, carrying three si-RNA to block SERT mRNA at 66% of normal levels. Improved self-control and reduced restlessness were already demonstrated in these rats. Present further studies consisted of male adult rats, bilaterally inoculated within the hippocampus; control rats received lentivirus particles inactivated with heat. Both groups were maintained in isolation for 5 months, starting from inoculation. Neurochemical changes were studied by proton magnetic resonance spectroscopy (1H-MRS): we found increased hippocampal viability and bioenergetic potential; however, rats showed a behaviorally depressive pattern, also characterized by enhanced affiliation. Based on the extent of such effects, the whole lenti-SERT group was divided into two subgroups, termed intermediate- and extreme- phenotype profiles. While all rats had a widespread modification within dorsal/ventral striatum, amygdala, and hypothalamus, only the former subgroup showed an involvement of Raphé medialis, while, for the latter subgroup, an increase of SERT within hippocampus was unexpectedly caused. Within the less-affected “intermediate” rats, hippocampal 5-HT7 receptors were down-modulated, and also similarly within substantia nigra, septum, and neocortex. This picture demonstrates that additional rather than fewer neurobiological changes accompany a lower phenotypic expression. Overall, tapping hippocampal SERT affected the balance between habits versus strategies of coping by promoting morphogenetic processes indicative of a serotonergic fiber plasticity. Supplementary studies about serotonergic dynamics and neurogenesis within fronto-striatal circuits are needed. 相似文献
35.
36.
V. Sawlani N. Davies M. Patel R. Flintham C. Fong G. Heyes G. Cruickshank N. Steven A. Peet A. Hartley H. Benghiat S. Meade P. Sanghera 《Clinical oncology (Royal College of Radiologists (Great Britain))》2019,31(1):41-49
Aims
Following stereotactic radiosurgery (SRS), brain metastases initially increase in size in up to a third of cases, suggesting treatment failure. Current imaging using structural magnetic resonance imaging (MRI) cannot differentiate between tumour recurrence and SRS-induced changes, creating difficulties with patient management. Combining multiparametric MRI techniques, which assess tissue physiological and metabolic information, has shown promise in answering this clinical question.Materials and methods
Multiparametric MRI techniques, including spectroscopy, diffusion and perfusion imaging, were used for the differentiation of radiation-related changes and tumour recurrence after SRS for intracranial metastases in six cases. All patients presented with enlargement of the treated lesion, an increase in perilesional brain oedema and aggravation or appearance of neurological signs and symptoms from 7 to 29 weeks after primary treatment.Results
Multiparametric imaging helped to differentiate features of tumour progression (n = 4) from radiation-related changes (n = 2). A low apparent diffusion coefficient (ADC) <1000 × 10?6 mm2/s, high relative cerebral blood volume (rCBV) ratio > 2.1, high choline:creatine (Cho:Cr) ratio > 1.8 suggested tumour recurrence. A high ADC > 1000 × 10?6 mm2/s, low rCBV ratio < 2.1, Cho:Cr ratio < 1.8 suggested SRS-induced radiation changes. Multiparametric MRI diagnosis was confirmed by histology or radiological and clinical follow-up.Conclusion
Multiparametric MRI was helpful in the early identification of radiation-related changes and tumour recurrence and may be useful for monitoring treatment changes in intracranial neoplasms after SRS treatment. 相似文献37.
Debra Rivera Irene Kalleveen Catalina Arteaga de Castro Hanneke van Laarhoven Dennis Klomp Wybe van der Kemp Jaap Stoker Aart Nederveen 《NMR in biomedicine》2020,33(4)
High field 31P spectroscopy has thus far been limited to diffuse liver disease. Unlike lower field‐strength scanners, there is no body coil in the bore of the 7 T and despite inadequate penetration depth (<10 cm), surface coils are the current state‐of‐the‐art for acquiring anatomical images to support multinuclear studies. We present a system of proton antennas and phosphorus loops for 31P spectroscopy and provide the first ultrahigh‐field phosphorus metabolic imaging of a tumor in the abdomen. Herein we characterize the degree to which antennas are isolated from underlying loops. Next, we evaluate the penetration depth of the two antennas available during multinuclear examinations. Finally, we combine phosphorus spectroscopy (two loops) with parallel transmit imaging (eight antennas) in a patient. The loops and antennas are inherently decoupled (no added circuitry, <0.1% power coupling). The penetration depth of two antennas gives twice that of conventional loops. The liver and full axial slice of the abdomen were imaged with eight transmit/receive antennas using parallel transmit B1‐shimming to overcome image voids. Phosphorus spectroscopy from a liver metastasis resolved individual peaks for phosphocholine and phosphoethenalomine. Proton antennas are inherently decoupled from phosphorus loops. By using two proton antennas it is possible to perform region‐of‐interest image‐based shimming in over 80% of the liver volume, thereby enabling phosphorus spectroscopy of localized disease. Shimming of the full extent of the abdominal cross‐section is feasible using a parallel transmit array of eight antennas. A system architecture capable of supporting eight‐channel parallel transmit and multinuclear spectroscopy is optimal for supporting multiparametric body imaging, including metabolic imaging, for monitoring the response of patients with liver metastases to cancer treatments and for patient risk stratification. In the meantime, the existing infrastructure using two antennas is sufficient for preliminary studies in metabolic imaging of tumors in the liver. 相似文献
38.
Marcello Panagia Huamei He Tomas Baka David R. Pimentel Dominique Croteau Markus M. Bachschmid James A. Balschi Wilson S. Colucci Ivan Luptak 《NMR in biomedicine》2020,33(5)
Metabolic heart disease (MHD), which is strongly associated with heart failure with preserved ejection fraction, is characterized by reduced mitochondrial energy production and contractile performance. In this study, we tested the hypothesis that an acute increase in ATP synthesis, via short chain fatty acid (butyrate) perfusion, restores contractile function in MHD. Isolated hearts of mice with MHD due to consumption of a high fat high sucrose (HFHS) diet or on a control diet (CD) for 4 months were studied using 31P NMR spectroscopy to measure high energy phosphates and ATP synthesis rates during increased work demand. At baseline, HFHS hearts had increased ADP and decreased free energy of ATP hydrolysis (ΔG ~ ATP), although contractile function was similar between the two groups. At high work demand, the ATP synthesis rate in HFHS hearts was reduced by over 50%. Unlike CD hearts, HFHS hearts did not increase contractile function at high work demand, indicating a lack of contractile reserve. However, acutely supplementing HFHS hearts with 4mM butyrate normalized ATP synthesis, ADP, ΔG ~ ATP and contractile reserve. Thus, acute reversal of depressed mitochondrial ATP production improves contractile dysfunction in MHD. These findings suggest that energy starvation may be a reversible cause of myocardial dysfunction in MHD, and opens new therapeutic opportunities. 相似文献
39.