全文获取类型
收费全文 | 3900篇 |
免费 | 284篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 32篇 |
儿科学 | 164篇 |
妇产科学 | 105篇 |
基础医学 | 593篇 |
口腔科学 | 32篇 |
临床医学 | 307篇 |
内科学 | 928篇 |
皮肤病学 | 145篇 |
神经病学 | 586篇 |
特种医学 | 115篇 |
外科学 | 248篇 |
综合类 | 1篇 |
一般理论 | 1篇 |
预防医学 | 228篇 |
眼科学 | 37篇 |
药学 | 264篇 |
中国医学 | 9篇 |
肿瘤学 | 418篇 |
出版年
2024年 | 8篇 |
2023年 | 39篇 |
2022年 | 99篇 |
2021年 | 135篇 |
2020年 | 103篇 |
2019年 | 115篇 |
2018年 | 125篇 |
2017年 | 105篇 |
2016年 | 126篇 |
2015年 | 150篇 |
2014年 | 174篇 |
2013年 | 221篇 |
2012年 | 303篇 |
2011年 | 303篇 |
2010年 | 189篇 |
2009年 | 148篇 |
2008年 | 281篇 |
2007年 | 262篇 |
2006年 | 262篇 |
2005年 | 227篇 |
2004年 | 191篇 |
2003年 | 184篇 |
2002年 | 148篇 |
2001年 | 29篇 |
2000年 | 32篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 6篇 |
1965年 | 2篇 |
排序方式: 共有4213条查询结果,搜索用时 15 毫秒
21.
22.
Face-selective processing and the effect of pleasant and unpleasant emotional expressions on ERP correlates. 总被引:9,自引:0,他引:9
Previous studies have revealed that decoding of facial-expressions starts very early in the brain ( approximately 180 ms post-stimulus) and might be processed separately from the basic stage of face perception. In order to explore brain potentials (ERPs) related to decoding of facial-expressions and the effect of emotional valence of the stimulus, we analyzed 18 normal subjects. Faces with five basic emotional expressions (fear, anger, surprise, happiness, sadness) and neutral stimulus were presented in random order. The results demonstrated that an emotional face elicited a negative peak at approximately 230 ms (N230), distributed mainly over the posterior site for each emotion. The electrophysiological activity observed may represent specific cognitive processing underlying the decoding of emotional facial-expressions. Nevertheless, differences in peak amplitude were observed for high-arousal negative expressions compared with positive (happiness) and low-arousal expressions (sadness). N230 amplitude increased in response to anger, fear and surprise, suggesting that subjects' ERP variations are affected by experienced emotional intensity, related to arousal and unpleasant value of the stimulus. 相似文献
23.
Surface properties and cell response of low metal ion release Ti-6Al-7Nb alloy after multi-step chemical and thermal treatments 总被引:5,自引:0,他引:5
Ti-6Al-7Nb samples treated by innovative multi-step chemical and thermal processes were characterized in order to evaluate their surface properties and cell interaction. The main object was to asses if the treatments were effective in order to obtain a surface presenting at the same time bone-like apatite induction ability, low metal ion release, good cell response and high protein binding. The morphology, crystallographic structure, porosity and wettability of the treated materials were investigated, as well as their interaction with simulated body fluid during soaking for different times. Cytotoxicity, protein adsorption tests and in vitro fibroblast and osteoblast-like cell cultures were also performed. 相似文献
24.
Ahmad W Noci S Faiyaz ul Haque M Sarno T Aridon P Ahmad MM Amin-Ud-Din M Rafiq MA ul Haque S De Fusco M Ballabio A Franco B Casari G 《American journal of medical genetics》2001,100(1):62-65
Nonspecific X-linked mental retardation is a nonprogressive, genetically heterogeneous condition that affects cognitive function in the absence of other distinctive clinical manifestations. We report here linkage data on a large Pakistani family affected by a form of X-linked nonspecific mental retardation. X chromosome genotyping of family members and linkage analysis allowed the identification of a new disease locus, MRX53. The defined critical region spans approximately 15 cM between DXS1210 and DXS1047 in Xq22.2-26. A LOD score value of 3.34 at no recombination was obtained with markers DXS1072 and DXS8081. 相似文献
25.
Mireille Baltzinger Michela Ori Massimo Pasqualetti Irma Nardi Filippo M Rijli 《Developmental dynamics》2005,234(4):858-867
The skeletal structures of the face and throat are derived from cranial neural crest cells (NCCs) that migrate from the embryonic neural tube into a series of branchial arches (BAs). The first arch (BA1) gives rise to the upper and lower jaw cartilages, whereas hyoid structures are generated from the second arch (BA2). The Hox paralogue group 2 (PG2) genes, Hoxa2 and Hoxb2, show distinct roles for hyoid patterning in tetrapods and fishes. In the mouse, Hoxa2 acts as a selector of hyoid identity, while its paralogue Hoxb2 is not required. On the contrary, in zebrafish Hoxa2 and Hoxb2 are functionally redundant for hyoid arch patterning. Here, we show that in Xenopus embryos morpholino-induced functional knockdown of Hoxa2 is sufficient to induce homeotic changes of the second arch cartilage. Moreover, Hoxb2 is downregulated in the BA2 of Xenopus embryos, even though initially expressed in second arch NCCs, similar to mouse and unlike in zebrafish. Finally, Xbap, a gene involved in jaw joint formation, is selectively upregulated in the BA2 of Hoxa2 knocked-down frog embryos, supporting a hyoid to mandibular change of NCC identity. Thus, in Xenopus Hoxa2 does not act redundantly with Hoxb2 for BA2 patterning, similar to mouse and unlike in fish. These data bring novel insights into the regulation of Hox PG2 genes and hyoid patterning in vertebrate evolution and suggest that Hoxa2 function is required at late stages of BA2 development. 相似文献
26.
Carlo Caffarelli Carla Mastrorilli Angelica Santoro Massimo Criscione Michela Procaccianti 《Nutrients》2021,13(2)
Hazelnuts commonly elicit allergic reactions starting from childhood and adolescence, with a rare resolution over time. The definite diagnosis of a hazelnut allergy relies on an oral food challenge. The role of component resolved diagnostics in reducing the need for oral food challenges in the diagnosis of hazelnut allergies is still debated. Therefore, three electronic databases were systematically searched for studies on the diagnostic accuracy of specific-IgE (sIgE) on hazelnut proteins for identifying children with a hazelnut allergy. Studies regarding IgE testing on at least one hazelnut allergen component in children whose final diagnosis was determined by oral food challenges or a suggestive history of serious symptoms due to a hazelnut allergy were included. Study quality was assessed by the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Eight studies enrolling 757 children, were identified. Overall, sensitivity, specificity, area under the curve and diagnostic odd ratio of Cor a 1 sIgE were lower than those of Cor a 9 and Cor a 14 sIge. When the test results were positive, the post-test probability of a hazelnut allergy was 34% for Cor a 1 sIgE, 60% for Cor a9 sIgE and 73% for Cor a 14 sIgE. When the test results were negative, the post-test probability of a hazelnut allergy was 55% for Cor a 1 sIgE, 16% for Cor a9 sIgE and 14% for Cor a 14 sIgE. Measurement of IgE levels to Cor a 9 and Cor a 14 might have the potential to improve specificity in detecting clinically tolerant children among hazelnut-sensitized ones, reducing the need to perform oral food challenges. 相似文献
27.
Nutritional status in oncological patients may differ according to several modifiable and non-modifiable factors. Knowledge of the epidemiology of malnutrition/cachexia/sarcopenia may help to manage these complications early in the course of treatment, potentially impacting patient quality of life, treatment intensity, and disease outcome. Therefore, this narrative review aimed to critically evaluate the current evidence on the combined impact of tumor- and treatment-related factors on nutritional status and to draw some practical conclusions to support the multidisciplinary management of malnutrition in cancer patients. A comprehensive literature search was performed from January 2010 to December 2020 using different combinations of pertinent keywords and a critical evaluation of retrieved literature papers was conducted. The results show that the prevalence of weight loss and associated symptoms is quite heterogeneous and needs to be assessed with recognized criteria, thus allowing a clear classification and standardization of therapeutic interventions. There is a large range of variability influenced by age and social factors, comorbidities, and setting of cures (community-dwelling versus hospitalized patients). Tumor subsite is one of the major determinants of malnutrition, with pancreatic, esophageal, and other gastroenteric cancers, head and neck, and lung cancers having the highest prevalence. The advanced stage is also linked to a higher risk of developing malnutrition, as an expression of the relationship between tumor burden, inflammatory status, reduced caloric intake, and malabsorption. Finally, treatment type influences the risk of nutritional issues, both for locoregional approaches (surgery and radiotherapy) and for systemic treatment. Interestingly, personalized approaches based on the selection of the most predictive malnutrition definitions for postoperative complications according to cancer type and knowledge of specific nutritional problems associated with some new agents may positively impact disease course. Sharing common knowledge between oncologists and nutritionists may help to better address and treat malnutrition in this population. 相似文献
28.
Laparoscopic procedures in pregnancy 总被引:7,自引:0,他引:7
As the applications of laparoscopy for general surgical procedures expanded in the 1990s, pregnancy was initially considered a contraindication. Several case reports have suggested the safety of laparoscopy in pregnancy. Previous clinical studies indicate a higher fetal mortality may exist and advised caution. To evaluate the fetal outcome of laparoscopic procedures in pregnant patients at our institution, we retrospectively reviewed the medical records between 1991 and 1997 and identified 21 pregnant patients who underwent either a laparoscopic (n = 12) or open (n = 9) procedure. Appendectomies, cholecystectomies, and diagnostic laparoscopies were performed. Specific variables including age, length of procedure, hospital stay, duration of parenteral analgesic use, gestational age at the time of surgery and delivery, O2 saturation and EtCO2 during surgery, APGAR scores, and birth weights were compared between the two groups. Laparoscopic procedures during pregnancy resulted in shorter hospital stays (34 hours versus 91 hours; P = 0.01), less use of parenteral narcotic analgesics (5 hours versus 29 hours; P = 0.05), and no prolongation of operative times (51 minutes versus 63 minutes; P = 0.20). In addition, laparoscopy was performed at earlier gestational ages (12 weeks versus 29 weeks; P = 0.001). There was one miscarriage 7 days after a laparoscopic cholecystectomy early in the 1st trimester that was not statistically significant. Our experience did not show a higher incidence of fetal loss when comparing laparoscopic to open procedures in pregnant patients. 相似文献
29.
30.
Donato Gemmati Alessia Ongaro Gian L Scapoli Matteo Della Porta Silvia Tognazzo Maria L Serino Eros Di Bona Francesco Rodeghiero Giuseppe Gilli Roberto Reverberi Angelo Caruso Michela Pasello Agnese Pellati Monica De Mattei 《Cancer epidemiology, biomarkers & prevention》2004,13(5):787-794
Folate and methionine metabolism is involved in DNA synthesis and methylation processes. Polymorphisms in the genes of folate metabolism enzymes have been associated with some forms of cancer. In a case-control study, we evaluated whether four common polymorphisms in methylenetetrahydrofolate reductase (MTHFR C677T and A1298C), methionine synthase (MS A2756G), and methionine synthase reductase (MTRR A66G) genes may have a role in altering susceptibility to adult acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). We analyzed DNA of 120 adult ALL, 200 NHL, and 257 healthy control subjects. Individual carrying the MTHFR 677TT genotype showed a 3.6-fold decreased ALL risk [odds ratio (OR) 0.28, 95% confidence interval (95% CI) 0.12-0.72] than wild-types. Similarly, MS 2756GG individuals showed a 5.0-fold decreased ALL risk (OR 0.20, 95% CI 0.02-1.45) than wild-types. In combined results, subjects with the MTHFR 677CT/TT and MS 2756AG/GG genotypes revealed a 3.6-fold ALL risk reduction (OR 0.28, 95% CI 0.14-0.58) and those with the MTHFR 677TT and MTRR 66AG genotypes revealed a 4.2-fold ALL risk reduction (OR 0.24, 95% CI 0.06-0.81). Finally, those with the MS 2756AG/GG and MTRR 66AG/GG genotypes revealed a 2.2-fold ALL risk reduction (OR 0.45, 95% CI 0.10-0.85). Single analysis for NHL did not show any significant difference for all the polymorphisms investigated, but in the low-grade NHL subgroup, we found a 2.0-fold risk reduction for the MTRR 66GG homozygous genotype (OR 0.50, 95% CI 0.25-0.99), which was higher (OR 0.37, 95% CI 0.14-0.85) when analyzed in combination with MS 2756AA genotype. These data are in accordance with the hypothesis that polymorphisms in the genes for folate and methionine metabolism might play a greater role in the occurrence of ALL than NHL by influencing DNA synthesis and/or DNA methylation. 相似文献