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   18301篇
  免费   1033篇
  国内免费   98篇
耳鼻咽喉   316篇
儿科学   467篇
妇产科学   310篇
基础医学   2634篇
口腔科学   1565篇
临床医学   1324篇
内科学   3837篇
皮肤病学   429篇
神经病学   1236篇
特种医学   550篇
外科学   2134篇
综合类   103篇
一般理论   3篇
预防医学   2045篇
眼科学   253篇
药学   1280篇
中国医学   189篇
肿瘤学   757篇
  2023年   192篇
  2022年   407篇
  2021年   726篇
  2020年   453篇
  2019年   585篇
  2018年   731篇
  2017年   508篇
  2016年   546篇
  2015年   630篇
  2014年   806篇
  2013年   986篇
  2012年   1399篇
  2011年   1613篇
  2010年   857篇
  2009年   664篇
  2008年   1062篇
  2007年   1024篇
  2006年   878篇
  2005年   777篇
  2004年   657篇
  2003年   577篇
  2002年   473篇
  2001年   380篇
  2000年   341篇
  1999年   308篇
  1998年   131篇
  1997年   98篇
  1996年   104篇
  1995年   57篇
  1994年   62篇
  1993年   52篇
  1992年   140篇
  1991年   123篇
  1990年   91篇
  1989年   106篇
  1988年   101篇
  1987年   69篇
  1986年   88篇
  1985年   66篇
  1984年   61篇
  1983年   52篇
  1982年   33篇
  1981年   33篇
  1980年   34篇
  1979年   45篇
  1978年   31篇
  1977年   29篇
  1976年   36篇
  1975年   24篇
  1969年   25篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
This study presents a method of interpretative and systematic research with appliance to the development of studies in nursing called "the grounded theory", whose theoretical support is the symbolic interactionism. The purpose of the paper is to describe the grounded theory as an alternative methodology for the construction of knowledge in nursing. The study highlights four topics: the basic principle, the basic concepts, the trajectory of the method and the process of analysis of the data. We conclude that the systematization of data and its interpretation, based on social actors' experience, constitute strong subsidies to generate theories through this research tool.  相似文献   
992.
993.
The inquiry of this study is the beliefs related to the nursing professional in the first decades of this activity in Brazil. The investigation presupposes that some of these beliefs are still current. The objective is to point out the beliefs expressed by Revista Brasileira de Enfermagem (Brazilian Journal of Nursing) in 33 articles, during the period between 1932 (when the journal was created) and 1954. Five notions of the nursing professional were identified through the analyses of the symbology presented on the cover of the periodical--Egyptian mythology; ideal, science and art, inscribed in a triangle. The categories established for nurses were: self-forgetful, heroine, socially committed, mercenary and bad angel. Finally, the study proposes an interpretation to the ideas presented in the triangle.  相似文献   
994.
The present study has as objective to describe the methodologies for development of systems of information in health and the nursing, reflecting on aspects theoretical and practical based of this proposal. In this perspective, it focuses, critically, the hard and soft vision of the information system, the alternative methodologies and the necessities of new approaches in the system of information in nursing. It concludes emphasizing the necessity of if developing information systems that are extracted of the necessities of the practical of nursing and with the participation of these professionals.  相似文献   
995.
OBJECTIVE: Microsporidian Encephalitozoon cuniculi has been recognized as an opportunistic pathogen in immunosuppressed individuals, such as AIDS patients. The objective of the study was to develop pharmacologically immunosuppressed animals as a model of the natural occurring E. cuniculi infection. METHODS: Distinct groups of adult Balb-C mice were immunosuppressed with different doses of dexamethasone (Dx, 3 or 5 mg/kg/day, intraperitoneal route - IP) and inoculated with E. cuniculi spores by IP route intraperitoneally. Control groups (inoculated animals but non-immunosuppressed and non- inoculated animals but immunosuppressed) were also used. The spores of E. cuniculi were previously cultivated in MDCK cells. The animals were sacrificed and necropsied at 7, 14, 21, 28 and 35 days post-inoculation. Tissue fragments were collected and processed for light microscopy studies, using Gram-chromotrope and hematoxylin-eosin staining techniques. RESULTS: In all immunosuppressed and inoculated inoculated immunosuppressed mice,specially in those that received 5 mg/kg/day of dexamethasone, the most prominent necropsy findings were hepatomegaly and splenomegaly. The experimental inoculation resulted in a disseminated non-lethal infection, characterized by granulomatous lesions in several organs (liver, lungs, kidneys, gut and brain) but notably in the hepatic tissue. Spores of E. cuniculi were only seen in few animals treated with 5 mg/kg/day of Dx at 35 days post-infection. CONCLUSIONS: Microsporidiosis in Dx-immunosuppressed mice provides a useful model for studies of the microsporidial infection, resembling that one naturally occurring in immunodeficient individuals with AIDS.  相似文献   
996.
997.
The purpose of this exploratory study was to verify the problem of nursing aides professionalization and to analyze the offer of courses and demand regarding technical level capacitation at the state of S?o Paulo, Brazil. Data were obtained through the analysis of documents on professional capacitation in the area in the 1990s. Authors identified a scenario of conceptual and political changes regarding the professionalization and the existence of a great number of aides being professionalized. They also verified a tendency to increase the offer of courses and the demand regarding the capacitation and specialization at the technical level.  相似文献   
998.
A prolonged toxicity study was carried out in young European eel (Anguilla anguilla L.) to evaluate the effects of environmental contaminants, namely, two individual standard compounds, benzo[a]pyrene (BaP) and dehydroabietic acid (DHAA), and a complex mixture, bleached kraft pulp mill effluent (BKPME). Fish were exposed to BaP (0.22, 0.45, and 0.9 microM) and BKPME (3.12%, 6.25%, and 12.5% (v/v)) for 3, 7, and 30 days and to DHAA (0.07, 0.15, and 0.30 microM) for 3, 7, 30, 90, and 180 days. The biomarkers include biotransformation and genotoxicity indicators, such as total ethoxyresorufin O-deethylase (EROD) activity and frequency of erythrocytic nuclear abnormalities (ENAs), respectively. Hematological dynamics was assessed as frequency of immature erythrocytes (IEs). Histopathological examinations were carried out for the highest concentrations and for 30 days and longer exposures. Total EROD increases significantly only after 180 days of DHAA exposure. However, significant ENA induction was generally observed during exposure to all contaminants tested. Nevertheless, some of the ENA results suggest an altered genotoxic response, which may arise either from short-term exposures to the highest contaminant levels or long-term exposures to the lowest contaminant levels. IE frequency decreased significantly after 30 days of exposure to 0.45 microM BaP and 180 days of exposure to the entire DHAA concentration range. Increased density of pigmented macrophage aggregates in 30-day BaP- and BKPME-exposed fish as well as in 90- and 180-day DHAA-exposed fish confirmed histopathological liver alterations. Bile accumulation in hepatocytes after BaP treatment, cytoplasmic vacuolization and cell atrophy following DHAA exposure, as well as liver loss of parenchymal cells in BKPME-exposed fish, were also detected. Dispersed necrosis and focal inflammation were observed in the livers of all treated groups. Fish exposed to DHAA and BKPME showed skin and gill disruption as well as kidney Malpighian corpuscle alterations. All 30-day-treated groups revealed intense spleen hemosiderosis, indicating increased erythrophagia. This splenic effect may be strongly correlated with the observed disappearance of ENAs. Neoplastic lesions were not found. A multibiomarker strategy, which includes EROD, ENA, and IE assays as well as histopathological studies, contributed to a better understanding of the global toxic process.  相似文献   
999.
The objective of the present investigation was to study the protection afforded by a single administration of pralidoxime against the muscle necrosis induced by the organophosphate compound metamidophos at different times after intoxication. The fiber necrosis of the diaphragm muscle was quantified by a morphometric technique, comparing the area fraction occupied by necrotic muscle fibers in animals that received pralidoxime at different times after intoxication, i.e., 0, 1, 3, 6, and 12 h. Pralidoxime administration protected metamidophos-induced muscle necrosis in all groups studied except for the 12-h group. The earlier the administration of pralidoxime the greater the protection against muscle necrosis. This protection was not accompanied by complete reactivation of plasma cholinesterase activity. Results support the current opinion that pralidoxime should be administered as soon as possible after organophosphate intoxication, because in addition to reversing the muscarinic effects, early administration of pralidoxime also prevents muscle necrosis--which could impair muscular function and respiratory condition. The time difference between recovery of plasma cholinesterase activity and muscle necrosis protection indicates that this method is not completely trustworthy for patient follow-up, since some improvement may occur in spite of the low plasma cholinesterase activity.  相似文献   
1000.
The clinical course of multiple sclerosis (MS) is highly variable ranging from benign to aggressive, and is difficult to predict. Since magnetization transfer (MT) imaging can detect focal abnormalities in normal-appearing white matter (NAWM) before the appearance of lesions on conventional MRI, we hypothesized that changes in MT might be able to predict the clinical evolution of MS. We assessed MR data from MS patients who were subsequently followed clinically for 5 years. We computed the mean MT ratio (MTr) in gray matter, in lesions identified on T2-weighted MRI, and in NAWM, as well as in a thick central brain slice for each patient. Patients were divided into stable and worsening groups according to their change in Expanded Disability Status Scale (EDSS) scores over 5 years. We calculated the sensitivity, specificity, predictive value, and odds ratio of the baseline MTr measures in order to assess their prognostic utility. We found significant differences in baseline MTr values in NAWM (p = 0.005) and brain slice (p = 0.03) between clinically stable and worsening MS patients. When these MTr values were compared with changes in EDSS over 5 years, a strong correlation was found between the EDSS changes and MTr values in both NAWM (SRCC = −0.76, p < 0.001) and in the brain slice (SRCC = 0.59, p = 0.01). Baseline NAWM MTr correctly predicted clinical evolution in 15/18 patients (1 false positive and 2 false negatives), yielding a positive predictive value of 77.78 %, a negative predictive value of 88.89 %, and an odds ratio of 28. The relationship between 5-year changes in EDSS and MTr values in T2 weighted MRI lesions was weaker (SRCC = −0.43, p = 0.07). Our data support the notion that the quantification of MTr in the NAWM can predict the clinical evolution of MS. Lower MTr values predict poorer long-term clinical outcome. Abnormalities of MTr values in the NAWM are more relevant to the development of future patient disability than those in the T2-weighted MRI lesions. Received: 3 May 2001, Received in revised form: 11 October 2001, Accepted: 22 October 2001  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