首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3180篇
  免费   150篇
  国内免费   14篇
耳鼻咽喉   27篇
儿科学   55篇
妇产科学   40篇
基础医学   636篇
口腔科学   25篇
临床医学   215篇
内科学   884篇
皮肤病学   55篇
神经病学   237篇
特种医学   142篇
外科学   315篇
综合类   21篇
预防医学   211篇
眼科学   19篇
药学   243篇
中国医学   8篇
肿瘤学   211篇
  2023年   20篇
  2022年   71篇
  2021年   137篇
  2020年   65篇
  2019年   75篇
  2018年   78篇
  2017年   67篇
  2016年   81篇
  2015年   92篇
  2014年   125篇
  2013年   171篇
  2012年   259篇
  2011年   273篇
  2010年   170篇
  2009年   104篇
  2008年   195篇
  2007年   180篇
  2006年   170篇
  2005年   167篇
  2004年   144篇
  2003年   128篇
  2002年   107篇
  2001年   22篇
  2000年   12篇
  1999年   30篇
  1998年   12篇
  1997年   14篇
  1995年   12篇
  1994年   9篇
  1993年   8篇
  1992年   20篇
  1991年   11篇
  1990年   18篇
  1989年   9篇
  1988年   14篇
  1985年   14篇
  1984年   14篇
  1983年   9篇
  1982年   11篇
  1981年   8篇
  1979年   14篇
  1978年   9篇
  1977年   10篇
  1974年   14篇
  1973年   22篇
  1972年   16篇
  1971年   14篇
  1970年   13篇
  1969年   8篇
  1966年   8篇
排序方式: 共有3344条查询结果,搜索用时 31 毫秒
61.
Bone regeneration is a long-term process requiring proper scaffolding and drug delivery systems. The current study delivers a three-dimensional (3D) scaffold prepared by blend centrifugal spinning loaded with the osteogenic supplements (OS) β-glycerol phosphate, ascorbate-2-phosphate and dexamethasone. The OS were successfully encapsulated into a fibrous scaffold and showed sustained release for 30 days. Furthermore, biological testing showed the osteoinductive properties of the scaffolds on a model of human mesenchymal stem cells and stimulatory effect on a model of osteoblasts. The osteoinductive properties were further proved in vivo in critical size defects of rabbits. The amount of bone trabecules was bigger compared to control fibers without OS. The results indicate that due to its long-term drug releasing properties, single step fabrication process and 3D structure, the system shows ideal properties for use as a cell-free bone implant in tissue-engineering.

Bone regeneration is a long-term process requiring proper scaffolding and drug delivery systems.  相似文献   
62.
Epicardial RFA to Achieve Electrical PV Isolation. During catheter ablation of atrial fibrillation, ablation within the pulmonary veins is undesirable due to the risk of pulmonary venous stenosis and the possibility of leaving residual cuffs of arrhythmogenic tissue proximal to the ablation lesion set. An extra-ostial pulmonary vein isolation strategy may circumvent these limitations, but achieving electrical isolation can be technically challenging, even with the use of saline-irrigated radiofrequency energy technology. This report describes the successful use of epicardial radiofrequency ablation in a patient in whom endocardial irrigated radiofrequency ablation failed to achieve extra-ostial pulmonary vein isolation.  相似文献   
63.
Middle meningeal vessels, dural venous sinuses, and emissary veins leave imprints and canals in the endocranium, and thus provide evidence of vascular patterns in osteological samples. This paper investigates whether craniovascular morphology undergoes changes in craniosynostotic human skulls, and if specific alterations may reflect structural and functional relationships in the cranium. The analyzed osteological sample consists of adult individuals with craniosynostoses generally associated with dolichocephalic or brachycephalic proportions, and a control sample of anatomically normal adult skulls. The pattern and dominance of the middle meningeal artery, the morphology of the confluence of the sinuses, and the size and number of the emissary foramina were evaluated. Craniovascular morphology was more diverse in craniosynostotic skulls than in anatomically normal skulls. The craniosynostotic skulls often displayed enlarged occipito-marginal sinuses and more numerous emissary foramina. The craniosynostotic skulls associated with more brachycephalic morphology often presented enlarged emissary foramina, while the craniosynostotic skulls associated with dolichocephalic effects frequently displayed more developed posterior branches of the middle meningeal artery. The course and morphology of the middle meningeal vessels, dural venous sinuses, and emissary veins in craniosynostotic skulls can be related to the redistribution of growth forces, higher intracranial pressure, venous hypertension, or thermal constraints. These functional and structural changes are of interest in both anthropology and medicine, involving epigenetic traits that concern the functional and ontogenetic balance between soft and hard tissues.  相似文献   
64.
ObjectiveDespite profound neurological symptomatology there are only few MRI studies focused on the brain abnormalities in alpha-mannosidosis (AM). Our aim was to characterize brain MRI findings in a large cohort of AM patients along with clinical manifestations.MethodsTwenty-two brain MRIs acquired in 13 untreated AM patients (8 M/5F; median age 17 years) were independently assessed by three experienced readers and compared to 16 controls.ResultsFocal and/or diffuse hyperintense signals in the cerebral white matter were present in most (85%) patients. Cerebellar atrophy was common (62%), present from the age of 5 years. Progression was observed in two out of 6 patients with follow-up scans. Cortical atrophy (62%) and corpus callosum thinning (23%) were already present in a 13-month-old child. The presence of low T2 signal intensity in basal ganglia and thalami was excluded by the normalized signal intensity profiling. The enlargement of perivascular spaces in white matter (38%), widening of perioptic CSF spaces (62%), and enlargement of cisterna magna (85%) were also observed. Diploic space thickening (100%), mucosal thickening (69%) and sinus hypoplasia (54%) were the most frequent non-CNS abnormalities.ConclusionWhite matter changes and cerebellar atrophy are proposed to be the characteristic brain MRI features of AM. The previously reported decreased T2 signal intensity in basal ganglia and thalami was not detected in this quantitative study. Rather, this relative MR appearance seems to be related to the diffuse high T2 signal in the adjacent white matter and not the gray matter iron deposition that has been hypothesized.  相似文献   
65.
66.
Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare developmental lung disorder that is uniformly lethal. Affected infants die within the first few weeks of their life despite aggressive treatment, although a few cases of late manifestation and longer survival have been reported. We have shown previously that mutations and deletions in FOXF1 are a cause of this disorder. Although most of the cases of ACD/MPV are sporadic, there have been infrequent reports of familial cases. We present a family with five out of six children affected with ACD/MPV. DNA analysis identified a missense mutation (c.416G>T; p.Arg139Leu) in the FOXF1 gene that segregated in the three affected siblings tested. The same variant is also present as a de novo mutation in the mother and arose on her paternally derived chromosome 16. The two tested affected siblings share the same chromosome 16 haplotype inherited from their maternal grandfather. Their single healthy sibling has a different chromosome 16 haplotype inherited from the maternal grandmother. The results are consistent with paternal imprinting of FOXF1 in human.  相似文献   
67.
68.
69.
70.
Human visceral (VL, also known as Kala-azar) and cutaneous (CL) leishmaniasis are important infectious diseases affecting countries in East Africa that remain endemic in several regions of Ethiopia. The transmission and epidemiology of the disease is complicated due to the complex life cycle of the parasites and the involvement of various Leishmania spp., sand fly vectors, and reservoir animals besides human hosts. Particularly in East Africa, the role of animals as reservoirs for human VL remains unclear. Isolation of Leishmania donovani parasites from naturally infected rodents has been reported in several endemic countries; however, the status of rodents as reservoirs in Ethiopia remains unclear. Here, we demonstrated natural Leishmania infections in rodents. Animals were trapped in 41 localities of endemic and non-endemic areas in eight geographical regions of Ethiopia and DNA was isolated from spleens of 586 rodents belonging to 21 genera and 38 species. Leishmania infection was evaluated by real-time PCR of kinetoplast (k)DNA and confirmed by sequencing of the PCR products. Subsequently, parasite species identification was confirmed by PCR and DNA sequencing of the 18S ribosomal RNA internal transcribed spacer one (ITS1) gene. Out of fifty (8.2%) rodent specimens positive for Leishmania kDNA-PCR and sequencing, 10 were subsequently identified by sequencing of the ITS1 showing that five belonged to the L. donovani complex and five to L. tropica. Forty nine kDNA-positive rodents were found in the endemic localities of southern and eastern Ethiopia while only one was identified from northwestern Ethiopia. Moreover, all the ten ITS1-positive rodents were captured in areas where human leishmaniasis cases have been reported and potential sand fly vectors occur. Our findings suggest the eco-epidemiological importance of rodents in these foci of leishmaniasis and indicate that rodents are likely to play a role in the transmission of leishmaniasis in Ethiopia, possibly as reservoir hosts.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号