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   909篇
  免费   51篇
  国内免费   6篇
耳鼻咽喉   4篇
儿科学   25篇
妇产科学   12篇
基础医学   140篇
口腔科学   12篇
临床医学   65篇
内科学   239篇
皮肤病学   8篇
神经病学   84篇
特种医学   29篇
外科学   137篇
综合类   7篇
一般理论   2篇
预防医学   46篇
眼科学   1篇
药学   80篇
中国医学   4篇
肿瘤学   71篇
  2023年   5篇
  2022年   21篇
  2021年   22篇
  2020年   9篇
  2019年   12篇
  2018年   15篇
  2017年   8篇
  2016年   16篇
  2015年   19篇
  2014年   29篇
  2013年   15篇
  2012年   43篇
  2011年   49篇
  2010年   38篇
  2009年   35篇
  2008年   40篇
  2007年   43篇
  2006年   50篇
  2005年   44篇
  2004年   59篇
  2003年   34篇
  2002年   31篇
  2001年   32篇
  2000年   20篇
  1999年   18篇
  1998年   9篇
  1997年   4篇
  1996年   7篇
  1995年   8篇
  1992年   20篇
  1991年   14篇
  1990年   9篇
  1989年   24篇
  1988年   17篇
  1987年   13篇
  1986年   23篇
  1985年   15篇
  1984年   11篇
  1983年   9篇
  1980年   3篇
  1979年   8篇
  1978年   4篇
  1976年   3篇
  1974年   4篇
  1972年   5篇
  1970年   7篇
  1969年   7篇
  1968年   4篇
  1967年   10篇
  1966年   3篇
排序方式: 共有966条查询结果,搜索用时 15 毫秒
51.
Mutations of the epidermal growth factor receptor (EGFR) gene are found at a relatively high frequency in glioma, with the most common being the de2-7 EGFR (or EGFRvIII). This mutation arises from an in-frame deletion of exons 2-7, which removes 267 amino acids from the extracellular domain of the receptor. Despite being unable to bind ligand, the de2-7 EGFR is constitutively active and imparts a significant in vivo growth advantage to glioma cells. In order to examine the signalling pathways activated by the de2-7 EGFR and its biological effects in an in vitro system, the de2-7 EGFR gene was transfected into the murine IL-3-dependent pro-B-cell line BaF/3. Expression of the de2-7 EGFR enhanced the survival of BaF/3 cells in the absence of IL-3 by reducing apoptosis in a phosphatidylinositol 3-kinase (PI3-K)-dependent manner. Interestingly, while de2-7 EGFR also enhanced proliferation of BaF/3 cells in low levels of IL-3, this effect was independent of PI3-K. Survival and proliferation were further enhanced when BaF/3 cells were cotransfected with the de2-7 and wt EGFR. This was due to heterodimerization between the de2-7 and wt EGFR leading to trans-phosphorylation of the wt EGFR. This observation is directly relevant to glioma where de2-7 and wt EGFR appear to be coexpressed. Thus, expression of de2-7 EGFR in BaF/3 cells provides an in vitro model for evaluating the signalling pathways activated by this receptor.  相似文献   
52.
This article describes the unusual case of a 60-year-old woman suffering from pure progressive aphemia. The fusion of multimodal neuroimaging (MRI, perfusion SPECT) implicated the right frontal lobe, especially the inferior frontal gyrus. This area also showed the greatest functional MRI activation during the performance of a covert phonemic fluency task. Results are discussed in terms of bihemispheric language representation. The fusion of three sets of neuroimages has aided in the interpretation of the patient's cognitive brain dysfunction.  相似文献   
53.
Vaccine products currently licensed in the US and other countries are marketed in vials and syringes that may contain natural latex allergens. Little scientific information exists regarding the safety of vaccination of latex-allergic individuals. A review of data within the Vaccine Adverse Event Reporting System (VAERS), a large registry of reported possible vaccine adverse reactions was conducted. A search of the database, which contains >160,000 vaccine adverse event reports, revealed only 28 cases of possible immediate-type hypersensitivity reactions in vaccine recipients with a history of allergy to latex. Given the large number of immunizations administered every year in the US, the reported risk of allergic reactions possibly due to latex contamination of vaccines appears to be very small.  相似文献   
54.
PURPOSE: To evaluate fertility in male patients with osteosarcoma after chemotherapy including high doses of alkylating agents. PATIENTS AND METHODS: Postchemotherapy fertility was evaluated in 96 male patients who received chemotherapy at the authors' institution from 1976 to 1996 for localized bone osteosarcoma of the extremities. Four drugs were administrated (doxorubicin, cisplatin, methotrexate, ifosfamide) at different doses according to six different protocols. Eleven patients were prepubertal and 85 were postpubertal at the time of chemotherapy. The median age of these patients at the time of chemotherapy was 17 years (range 10-42), the median age at the time of the interview was 27 years (range 19-53), and the median follow-up from the end of chemotherapy was 9 years (range 4-17). RESULTS: Of the 96 patients, 26 underwent sperm analysis and 20 showed oligo- or azoospermia. Patients who received high-dose ifosfamide showed a higher incidence of azoospermia. Six patients were normospermic and received no ifosfamide or lower doses of ifosfamide. Eight patients fathered a total of 12 children. No birth defects or congenital anomalies were observed in their offspring. CONCLUSIONS: The rate of sterility was related to ifosfamide dosage. It appears that pubertal maturation is not affected by chemotherapy. No congenital malformations were seen in the children of the few patients who fathered children.  相似文献   
55.
OBJECTIVE: The main objective was to assess the sensitivity, specificity and reliability of PAPNET-assisted diagnosis in comparison with conventional screening. SETTING: Seven Italian and one English University or Research Institutes, and a random sample of an other 20 Italian Laboratories of the Italian National Health Service (INHS) provided the cervical smears. METHODS: During the training phase every center examined in rotation four sets of slides for a total of 300 representative slides. Afterwards, 900 "positive" slides were added to the 3,100 slides which were collected consecutively without any selection or exclusion. The eight main centers were divided into four couples and each couple of centers examined 775 slides with the PAPNET system, "blindly" to the original diagnosis. An expert cytopathologist (M.A.) of the National Institute of Health (NIH) reassessed 40% of the slides with an original negative diagnosis to evaluate the false negative rate. Two expert NIH cytopathologists (M.A., G.M.) re-examined all slides where a disagreement had been observed between the original and one or both of the study diagnoses. The main analyses concerned the following three main categories: WNL and unsatisfactory for evaluation; ASCUS, AGUS and LSIL; HSIL and carcinoma. A special algorithm was devised to define the reference diagnosis for sensitivity and specificity assessment. RESULTS: Laboratories, even belonging to the same couple, classified as "no review" a very different proportion of slides ranging from 35% to 74%. The index of kappa agreement between the members of couples examining the same sets of slides was low or very low, ranging from 0.30 to 0.03. The sensitivity of the review classification was particularly low in some laboratories. Surprisingly, only a small correlation was observed between the sensitivity of the review classification and the proportion of slides classified as "review". The "tentative" diagnosis on PAPNET tiles of the "review" slides was almost as reliable as the microscopic diagnosis. In the overall performance, there were many significant differences among the eight laboratories. The best laboratory had a sensitivity of 95% and a specificity of 96%. At least three laboratories displayed unacceptably low sensitivity and one a very low specificity. CONCLUSION: Altogether these results seem to confirm that there are wide differences among cytological laboratories per se, and that these differences are intensified by the use of an instrument like PAPNET. The huge variation in performance may be explained by differences in basic skills and by different training, but it is difficult to understand exactly what could have been done to reduce it.  相似文献   
56.
Erythromycin resistance among Streptococcus pyogenes strains has been reported in Italy at high rates during the last few years. A total of 152 erythromycin-resistant isolates of this species from southern Italian regions were characterized for the macrolide-resistance phenotype and screened by PCR for the corresponding genetic determinant. A close correlation was found between these phenotypic/genotypic data concerning macrolide resistance and results of Sma I macrorestriction fragment patterns (PFGE) analysis. In fact, the vast majority of the isolates assigned to individual PFGE classes mostly belonged to a single phenotype of macrolide resistance. All untypeable isolates belonged to the M phenotype. Twenty-two distinct PFGE types were recognized, of which 11 were recorded in only one isolate (one-strain type); about 50% of typeable isolates fell into five type clusters and 70% in seven. The increased erythromycin resistance among Italian isolates of S. pyogenes does not appear to be due to the spread of a single clone, but results indicate that the majority of group A streptococci examined are probably spread from a limited number of clones.  相似文献   
57.
Classification criteria for Sj?gren's syndrome (SS) were developed and validated between 1989 and 1996 by the European Study Group on Classification Criteria for SS, and broadly accepted. These have been re-examined by consensus group members, who have introduced some modifications, more clearly defined the rules for classifying patients with primary or secondary SS, and provided more precise exclusion criteria.  相似文献   
58.
ICU nurses hold an important role in the management of septic patients underlining with their ability to recognize SIRS that is the first step in the proinflammatory and procoagulant cascade following an infection. Early and timely approach to organ dysfunction can indeed modify the damages due to hypoperfusion. The ability to recognize organ dysfunction using different monitoring devices available should be part of the nursing attitudes.  相似文献   
59.
The conformation of several Met-Ile-Phe-Leu analogues was analyzed using circular dichroism and infra-red absorption. Their effect on human neutrophils was verified by receptor binding assays and measurements of lysozyme release. The results demonstrate that in amphipatic environments the compounds examined can be highly and weakly ordered in beta-turn structures, in dependence on their N-terminal substituents. The ability of the compounds to evoke neutrophil functions appears strongly and weakly influenced by N- and C-terminal modification, respectively.  相似文献   
60.
Abstract. A survey in the cities of Genoa and Savona (Italy) was performed to examine stress levels in caregivers of patients with Alzheimers disease in the context of a project of the Italian Ministry of Health named Cronos. It offered free anticholinesterase inhibitor therapy to patients who addressed dedicated Neurological Units; in this occasion caregivers could be invited to express the main difficulties encountered in managing demented people during an interview conducted by health personnel of the Neurophysiology Service. Caregivers were mainly women, daughters or spouses, with a medium educational level, retired, housekeepers, employees or teachers; they claimed a lowering of economic standard of living of the family owing to extra expenses for assistance. Satisfaction was expressed towards specialists, while support by general practitioners and other sanitary services was usually lacking and money contribution from the government or territorial services was considered inadequate. From the emotional point of view, caregivers claim loss of free time, friendships and hobbies, and feel isolated in the social context; sometimes the patients death is thought of as a solution. A strong need for information and support is clearly emerging and any further interventions should take these requirements into consideration.  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