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   12465篇
  免费   825篇
  国内免费   61篇
耳鼻咽喉   77篇
儿科学   387篇
妇产科学   357篇
基础医学   1752篇
口腔科学   189篇
临床医学   1385篇
内科学   2592篇
皮肤病学   275篇
神经病学   1377篇
特种医学   389篇
外科学   1109篇
综合类   198篇
一般理论   1篇
预防医学   1046篇
眼科学   370篇
药学   694篇
中国医学   31篇
肿瘤学   1122篇
  2023年   143篇
  2022年   228篇
  2021年   469篇
  2020年   303篇
  2019年   436篇
  2018年   404篇
  2017年   331篇
  2016年   373篇
  2015年   383篇
  2014年   504篇
  2013年   707篇
  2012年   1027篇
  2011年   1029篇
  2010年   543篇
  2009年   448篇
  2008年   792篇
  2007年   817篇
  2006年   709篇
  2005年   609篇
  2004年   610篇
  2003年   551篇
  2002年   549篇
  2001年   79篇
  2000年   72篇
  1999年   97篇
  1998年   101篇
  1997年   72篇
  1996年   55篇
  1995年   49篇
  1994年   51篇
  1993年   45篇
  1992年   41篇
  1991年   50篇
  1990年   33篇
  1989年   34篇
  1988年   28篇
  1987年   39篇
  1985年   36篇
  1984年   33篇
  1983年   23篇
  1982年   33篇
  1981年   36篇
  1980年   35篇
  1979年   24篇
  1978年   25篇
  1976年   20篇
  1974年   23篇
  1973年   21篇
  1972年   19篇
  1971年   21篇
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
981.
982.
BACKGROUND. In some active multiple sclerosis (MS) lesions, a strong immune reaction at the lesion edge may contain growth and thereby isolate the lesion from the surrounding parenchyma. Our previous studies suggest that this process involves opening of the blood-brain barrier in capillaries at the lesion edge, seen on MRI as centripetal contrast enhancement and a colocalized phase rim. We hypothesized that using these features to characterize early lesion evolution will allow in vivo tracking of tissue degeneration and/or repair, thus improving the evaluation of potential therapies for chronic active lesions.METHODS. Centripetally and centrifugally enhancing lesions were studied in 17 patients with MS using 7-tesla MRI. High-resolution, susceptibility-weighted, T1-weighted (before/after gadolinium), and dynamic contrast–enhanced scans were acquired at baseline and months 1, 3, 6, and 12. For each lesion, time evolution of the phase rim, lesion volume, and T1 hypointensity were assessed. In autopsies of 3 progressive MS cases, the histopathology of the phase rim was determined.RESULTS. In centripetal lesions, a phase rim colocalized with initial contrast enhancement. In 12 of 22, this phase rim persisted after enhancement resolved. Compared with centripetal lesions with transient rim, those with persistent rim had less volume shrinkage and became more T1 hypointense between months 3 and 12. No centrifugal lesions developed phase rims at any time point. Pathologically, persistent rims corresponded to an iron-laden inflammatory myeloid cell population at the edge of chronic demyelinated lesions.CONCLUSION. In early lesion evolution, a persistent phase rim in lesions that shrink least and become more T1 hypointense over time suggests that the rim might mark failure of early lesion repair and/or irreversible tissue damage. In later stages of MS, phase rim lesions continue to smolder, exerting detrimental effects on affected brain tissue.TRIAL REGISTRATION. NCT00001248.FUNDING. The Intramural Research Program of NINDS supported this study.  相似文献   
983.
OBJECTIVE: To develop a hierarchical scale that measures activity limitations in walking in patients with lower-extremity disorders who live at home. DESIGN: Cross-sectional study. SETTING: Orthopedic workshops and outpatient clinics of secondary and tertiary care centers. PARTICIPANTS: Patients (N=981; mean age +/- standard deviation, 58.6+/-15.4 y; 46% men) living at home, with different lower-extremity disorders: stroke, poliomyelitis, osteoarthritis, amputation, complex regional pain syndrome type I, and diabetic and degenerative foot disorders. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: (1) Fit of the monotone homogeneity model, indicating whether items can be used for measuring patients; (2) fit of the double monotonicity model, indicating invariant (hierarchical) item ordering; (3) intratest reliability, indicating repeatability of the sum score; (4) robustness, addressing the clinimetric properties within subgroups of patients; and (5) differential item functioning, addressing the validity of comparisons between subgroups of patients. RESULTS: Thirty-five of 41 dichotomous items had (1) good fit of the monotone homogeneity model (coefficient H=.50), (2) good fit of the double monotonicity model (coefficient H(T)=.33), (3) good intratest reliability (coefficient rho=.95), (4) satisfactory robustness (within subgroups of patients defined by age, sex, and diagnosis), and (5) some differential item functioning (6 items in amputees compared with nonamputees). CONCLUSIONS: A hierarchical scale, with excellent scaling characteristics, was developed to measure activity limitations in walking in patients with lower-extremity disorders who live at home. The measurements should be interpreted cautiously when making comparisons between amputees and nonamputees.  相似文献   
984.

Introduction

Current practices for renal replacement therapy in intensive care units (ICUs) remain poorly defined. The DOse REsponse Multicentre International collaborative initiative (DO-RE-MI) will address the issue of how the different modes of renal replacement therapy are currently chosen and performed. Here, we describe the study protocol, which was approved by the Scientific and Steering Committees.

Methods

DO-RE-MI is an observational, multicentre study conducted in ICUs. The primary end-point will be the delivered dose of dialysis, which will be compared with ICU mortality, 28-day mortality, hospital mortality, ICU length of stay and number of days of mechanical ventilation. The secondary end-point will be the haemodynamic response to renal replacement therapy, expressed as percentage reduction in noradrenaline (norepinephrine) requirement. Based on the the sample analysis calculation, at least 162 patients must be recruited. Anonymized patient data will be entered online in electronic case report forms and uploaded to an internet website. Each participating centre will have 2 months to become acquainted with the electronic case report forms. After this period official recruitment will begin. Patient data belong to the respective centre, which may use the database for its own needs. However, all centres have agreed to participate in a joint effort to achieve the sample size needed for statistical analysis.

Conclusion

The study will hopefully help to collect useful information on the current practice of renal replacement therapy in ICUs. It will also provide a centre-based collection of data that will be useful for monitoring all aspects of extracorporeal support, such as incidence, frequency, and duration.  相似文献   
985.
986.
987.
The cellular uptake of nonphosphorylated myo-inositol (MI) and its incorporation into phosphoinositide in the rat epitrochlearis muscle was measured. Cellular uptake of [2-3H]MI was determined by the difference between total uptake and [2-3H]MI present in the extracellular fluid determined with [1-14C]mannitol. Cellular uptake was parabolic and directly proportional to medium MI concentrations between 25 and 3,200 μM. Saturation of a MI carrier was not evident. Moreover, uptake was not inhibited by 2 mM ouabain, 0.3 mM 2,4-dinitrophenol, or 22 mM glucose. Insulin, 100 mU/ml, was without effect on either cellular uptake of [2-3H]MI or its incorporation into phosphoinositides. In muscles that were preloaded with [2-3H]MI and then incubated in media that contained a constant amount of MI but no [2-3H]MI, 44.3% of the [2-3H]MI was released after 10 min increasing to 62.5% by 120 min. Cellular MI concentrations were 0.18 μmol/g wet tissue (four times plasma levels) in rapidly isolated and frozen epitrochlearis muscle. When muscle was incubated without MI, 48% of endogenous MI was lost rapidly. Restoration of cellular MI in 50 μM MI media occurred in two phases, a rapid uptake phase lasting 10 min and a subsequent slow phase of MI uptake.  相似文献   
988.
This article describes a case study that aimed to consider the unique needs of a client who has intellectual disabilities and a terminal illness. Data collection included semi-structured interviews with the client and professionals involved in his care. Five broad sets of themes emerged from these interviews. Although these are not unique to the rapidly evolving field of palliative care, they are less familiar within the specialism of intellectual disabilities, i.e. difficulties and delays around diagnosing the illness, consent issues, conflicts between the carers and the family, truth-telling, and the need for professional support. Professionals who work with a person with intellectual disabilities and a terminal illness need to be aware that special issues may arise. The effects of potential problems with comprehension and communication need to be assessed individually. A close collaboration between all professionals, carers, family and the client, and the mutual sharing of expertise, is essential to ensure the best possible care.  相似文献   
989.
990.
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