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   8509篇
  免费   546篇
  国内免费   57篇
耳鼻咽喉   51篇
儿科学   213篇
妇产科学   253篇
基础医学   1333篇
口腔科学   188篇
临床医学   763篇
内科学   1813篇
皮肤病学   84篇
神经病学   791篇
特种医学   349篇
外国民族医学   1篇
外科学   1261篇
综合类   84篇
一般理论   12篇
预防医学   609篇
眼科学   173篇
药学   552篇
中国医学   4篇
肿瘤学   578篇
  2023年   47篇
  2022年   53篇
  2021年   161篇
  2020年   84篇
  2019年   158篇
  2018年   213篇
  2017年   127篇
  2016年   153篇
  2015年   195篇
  2014年   290篇
  2013年   385篇
  2012年   488篇
  2011年   535篇
  2010年   302篇
  2009年   255篇
  2008年   499篇
  2007年   524篇
  2006年   475篇
  2005年   433篇
  2004年   497篇
  2003年   436篇
  2002年   402篇
  2001年   127篇
  2000年   145篇
  1999年   157篇
  1998年   99篇
  1997年   67篇
  1996年   68篇
  1995年   68篇
  1994年   57篇
  1993年   41篇
  1992年   63篇
  1991年   42篇
  1990年   46篇
  1989年   46篇
  1988年   52篇
  1987年   40篇
  1986年   63篇
  1985年   49篇
  1984年   57篇
  1983年   50篇
  1982年   44篇
  1981年   42篇
  1980年   35篇
  1979年   31篇
  1978年   35篇
  1977年   36篇
  1975年   29篇
  1973年   35篇
  1971年   23篇
排序方式: 共有9112条查询结果,搜索用时 546 毫秒
81.
The purpose of cardiopulmonary bypass is to maintain perfusion and oxygenation of the vital organs in the absence of heart and lung function, usually to facilitate surgery on the heart, but occasionally in other situations. Although the intricacies of the modern extracorporeal circuit and the conduct of cardiopulmonary bypass are the domain of the clinical perfusion scientist (‘perfusionist’), safe surgery mandates a good understanding of some fundamentals by the anaesthetist and the surgeon. This review is aimed at the anaesthetist. First, we will systematically examine the main components of the extracorporeal circuit, travelling in the direction that blood travels, from the venous cannula to the arterial cannula. Then we will describe the process of preparing for bypass, ‘going on’, conducting a bypass run, and weaning and separation from bypass. It is crucial to have clear communication between the surgeon, perfusionist and anaesthetist. This can be difficult for the novice because a quite specific language has evolved in cardiac operating theatres to signal key events in the cardiopulmonary bypass sequence. As we go through this article, we will highlight commonly used terminology and expressions used.  相似文献   
82.
ObjectiveWe sought to assess how women interpret the information they find online about the overall safety and risk of infertility associated with abortion and cesarean delivery (CD).MethodsWe conducted an exploratory, prospective study tracking the internet searches of 100 reproductive-aged individuals who identify as women. We directed participants to search for information about either (1) whether surgical abortion or CD is safe or (2) the risk of infertility following surgical abortion or CD. Our data collection had 3 phases: baseline survey, directed internet search, and a postsearch survey. We analyzed participants’ pre- and postsurvey responses using bivariate tests and analyzed within-subject changes. We evaluated the sites they visited based on expert ratings of site content based on trustworthiness and slant.ResultsWomen perceived abortion as safer and less likely to cause infertility after their web searches than before (70% perceived abortion in the United States as very/completely safe presearch vs 92% postsearch; p < 0.02). Women's perceptions about CD did not change. Participants sought information from web pages that experts largely deemed trustworthy and lacking in slant.ConclusionsWomen's perceptions about abortion safety and risk can be influenced by information they find online; perceptions about CD safety and risk may be less influenced by online information.ImplicationsDisseminating high quality, user-friendly abortion information on highly ranked and easily findable websites can help women find evidence-based information and influence knowledge about abortion.  相似文献   
83.
Certain delivery systems are intended to release the active ingredient in different phases to obtain the desired therapeutic effect. For these formulations, such as a bilayer tablet, it is desirable to distinguish and measure the release of drug from the different phases simultaneously. Mass spectrometric methods were developed to measure three ibuprofen isotopomers in serum and two in dissolution fluid. The analytical methods were linear (r 0.992) over the concentration range of interest and recovery was greater than 99.2% for all isotopomers. Coadministration of [2H0]ibuprofen, [2H4]ibuprofen, and [2H7]ibuprofen to male beagles demonstrated that the isotopomers were bioequivalent and verified the absence of any kinetic isotope effect due to deuterium incorporation (p = 0.286). These methods were then used to evaluate a bilayer tablet formulation composed of an immediate release layer of 100 mg [2H4]ibuprofen and a sustained release layer with a drug load of 300 mg [2H0]ibuprofen. Two different rate-controlling polymer matrices that provided similar in vitro dissolution profiles were compared in the sustained release phase, while the immediate release formulation remained the same. In male beagles, the HPMC matrix delivered a significantly greater amount of ibuprofen (p < 0.05). The AUC was threefold greater for HPMC (1067 ± 437 nmole * h/ml) versus EUDRAGIT® (320 ± 51), and Cmax was nearly four times greater (145 ± 62.1 nmole/ml for HPMC versus 37.9 ± 14.4 for EUDRAGIT®). Although Tmax for HPMC (3.4 ± 1.9 h) lagged behind EUDRAGIT® (2.0 ± 0.82 h), the difference was not significant (p > 0.05). The immediate release layer was absorbed to the same extent as an oral solution (containing [2H7]ibuprofen) that was administered concomitantly with the bilayer tablet. Using the stable isotope markers also demonstrated that the release rates of the two layers were independent of each other, both in vivo and in vitro. Stable isotope techniques are a useful tool in the development of biphasic release formulations since they can be used to determine proper drug load of each phase as well as the appropriate rate of release.  相似文献   
84.
BACKGROUND: Antiendomysium antibodies (EMA) detection in serum is the best screening test for coeliac disease (CD): in saliva it has not yet been assayed. Aims of this study are: to verify the presence of EMA in saliva collected with a not invasive technique; to evaluate the validity of serum and salivary EMA in CD screening. METHODS: We investigated 130 subjects divided into 3 groups: "A": 45 untreated CD patients (mean age 6.11); "B": 18 CD patients treated with a gluten free diet (mean age 13.2); "C": 67 controls (mean age 8.9). We performed the EMA test using the indirect immunofluorescence technique, in serum and in saliva concentrated samples. RESULTS: Our results show: sensitivity EMA serum 100%; specificity EMA serum 96.5%; sensitivity EMA saliva 46.5%; specificity EMA saliva 100%; pos. pred. value EMA serum 93.5%; neg. pred. value serum 100%; pos. pred. value EMA saliva 100%; neg. pred. value saliva 78.7%. CONCLUSIONS: Conclusion indicates a high specificity of salivary EMA and a high sensitivity of serum EMA, anyway biopsy is still recommended for diagnosis of CD.  相似文献   
85.
BACKGROUND: Many advances have been made in the sensitivity of assays for hepatitis C virus antibodies (HCV-Ab). Nevertheless, polymerase chain reaction (PCR) is still the best method to establish if infection has become chronic. In this study we utilised third-generation assays for HCV-Ab in a four-year follow-up to determine the trend in antibody levels in currently and past infected patients. METHODS: Seventy-two multitransfused subjects were enrolled. All the patients were reactive at the first test with third-generation screening and confirmatory assays (ELISA-3 and RIBA-3) for HCV-Ab. They were subsequently retested in a follow-up ranging from 41 to 47 months. Viraemia was investigated with a standardised PCR kit; negative samples were reevaluated with nested PCR. Differences in antibody trend were calculated with the Wilcoxon signed-rank test. RESULTS: No statistical variation in antibody titre was found in the 41 HCV-RNA positive patients, although some of these showed a decrease in anti-c100p level. In contrast, anti-c22p, anti-c33c and anti-c100p levels decreased significantly in the 19 past infected patients. Twelve patients were HCV-RNA negative or intermittently positive with commercial PCR test, and consistently or intermittently positive in nested PCR: in these patients, antibody trend varied. CONCLUSIONS: Although resolving hepatitis is associated with a decrease in antibody titre, the trend should be observed for a long period to distinguish between chronic and past infection. However, the evaluation in a single patient can be unreliable. Since a doubtful response for HCV-RNA is in some cases obtained, further improvements in the diagnosis of chronic HCV infection are needed.  相似文献   
86.
INTRODUCTION: Breast scintigraphy (BS) with the bone-seeking agent 99mTc-medronate (MDP) can be usefully combined with mammography to diagnose and characterize questionable breast lumps. However this radiotracer does not seem to provide any further prognostic information about breast cancer. Therefore we investigated the prognostic yield of MDP-BS searching for correlations between scintigraphic findings and the major biological and histologic parameters. MATERIALS AND METHODS: We retrospectively analyzed a series of 44 primary breast cancers. All patients had undergone 99mTc-MDP bone scan for preoperative staging, as well as conventional breast imaging. We statistically compared the cancer/background ratio (c/b index) with lesion histotype, diameter, grading, and the tissue concentrations of steroid receptors, cathepsine D, type 1 timidine kinase, pS2 and p53 proteins. RESULTS: MDP-BS failed to depict 11 of 44 lesions (O 0.5-2 cm), detected 7 of 16 mammographically questionable lesions and correctly visualized the two multifocal cases. Also, MDP-BS depicted no metastatic axillary lymph nodes. We found no statistically significant correlation between the c/b index and the prognostic markers. DISCUSSION AND CONCLUSIONS: Differently from BS with 99mTc-MIBI, 201T1, 18F-FDG, 111In-OCT and radiolabeled estrogens and despite its good overall accuracy, MDP-BS appears to have no prognostic role. In fact, despite the well-known capability of soft tissue lesions to take up the tracer, MDP tumor trapping seems to depend mainly on the increased permeability of neovessels and on interstitial space enlargement. Few reports are available in the literature on the correlation between in vivo MDP uptake by the breast cancer and prognostic parameters. Thus, we tested possible correlations between the amount of MDP taken up by the breast cancer, histologic features and cell concentrations of some major biomarkers. The lack of any statistical significance is in agreement with the theory, and confirms the little prognostic value of MDP-BS. Nevertheless, further trials are warranted on larger series of cases to validate our personal findings.  相似文献   
87.
Although estimates as to the incidence of personality disorder in the elderly remain controversial, it is well known that such a disorder is prevalently ego-syntonic and capable of interfering with the onset and treatment of other somatic and psychic pathologies, especially in later life, when individuals tend tobe particularly vulnerable. Misdiagnosis or failure to treat these disorders may greatly diminish the quality of life of older adults and their families. The aim of this work is to define the chief psychopharmacological and psychotherapeutic guidelines for treating personality disorders in the elderly. Pharmacologically, patients require treatment with molecules designed to rebalance neurotransmitter system alterations, which underlie the symptomatological picture. As regards psychotherapeutic treatment, although there are only a few validation studies, we believe that dialectical behavior therapy and interpersonal psychotherapy may constitute valid therapeutic approaches that meet both the needs and the individual characteristics of patients affected by personality disorder and those of elderly patients.  相似文献   
88.
OBJECTIVE: This study measures and compares use of and satisfaction with medical and social services in addition to subjectively perceived needs of family supporters of patients with probable or possible Alzheimer's disease (AD) and family supporters of non-demented elderly people. Differences in judgement of services within the subpopulation of families of AD patients are also assessed by gender and burden level.METHODS: The main family supporters of 60 community-dwelling elderly (aged over 65) with Alzheimer's disease and of 60 age- and sex-matched controls were tested with a detailed questionnaire on use and satisfaction with services, any unmet needs and kinds of intervention perceived to be helpful.RESULTS: Supporters of elderly people with AD were significantly more involved in providing care than supporters of non-demented people. Judgement on the health, social relations and financial status of their families was significantly worse in AD supporters than in supporters of non-demented elderly people. Although the former made more use of available health and social services than the control population, they did appear to make little use of such services, not only because of lack of information but also for logistic reasons or because they would prefer a service with more specifically trained operators or more tailored intervention. AD family supporters would like to receive more information and support from their general practitioner, which confirms the importance of this figure in management of this pathology. They were less satisfied with the care provided than the control population, particularly those with a moderate-high burden. Irrespective of burden level, they also expressed a need for financial and psychological support and adequate intervention schemes, especially within the home. These should be provided by specially trained personnel and be tailored to specifically manage the individual patient's problems, especially in relation to behavioural disorders. This would help alleviate caregiver burden and allow patients to continue to be managed at home.  相似文献   
89.
Berengario da Carpi was magister of anatomy and surgery at the University of Bologna from 1502 to 1527. Eustachio and Falloppia defined him as 'the restaurator of anatomy'. He was a great surgeon, anatomist and physician of illustrious patients including Lorenzo II dei Medici, Giovanni dalle Bande Nere, Galeazzo Pallavicini, Cardinal Colonna, and Alessandro Soderini. He had strong links to the intellectuals of his time (Forni, Bonamici, Manuzio, Pomponazzi) as well as with the Medici family. He was respected by the Popes Julius II, Leo X and Clement VII. His main contributions are the Isogogae Breves, De Fractura calvae sive cranei, and the illustrated Commentaria on the Anatomy of Mondino de Liucci, a textbook utilized for more than 200 years, which Berengario aimed to restore to its initial text. The Commentaria constitutes the material for the last part of this paper which concludes with a personal translation of some passages on 'The kidney', where the author gives poignant examples of experimental ingenuity.  相似文献   
90.
A case of unusual transmission by Plasmodium falciparum malaria is reported. The patient, had not been travelling outside North-West of Italy for the previous 6 months, he was not drug abuser. He had spent the last two months prior his admission, partly in his home town, an urban area in the region of Piemonte, and partly in a resort area on the Ligurian sea. Neither place has ever been associated with unusual malaria transmission. The possible transmission way is through a live vector imported from endemic area in a port terminal near a resort area.  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