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   34500篇
  免费   2224篇
  国内免费   99篇
耳鼻咽喉   496篇
儿科学   843篇
妇产科学   480篇
基础医学   4181篇
口腔科学   459篇
临床医学   3745篇
内科学   7060篇
皮肤病学   426篇
神经病学   3056篇
特种医学   1372篇
外科学   5724篇
综合类   398篇
一般理论   40篇
预防医学   3095篇
眼科学   526篇
药学   2571篇
中国医学   30篇
肿瘤学   2321篇
  2024年   27篇
  2023年   251篇
  2022年   473篇
  2021年   1094篇
  2020年   642篇
  2019年   988篇
  2018年   1180篇
  2017年   813篇
  2016年   827篇
  2015年   990篇
  2014年   1481篇
  2013年   1948篇
  2012年   2817篇
  2011年   2884篇
  2010年   1510篇
  2009年   1400篇
  2008年   2404篇
  2007年   2347篇
  2006年   2161篇
  2005年   2183篇
  2004年   2056篇
  2003年   1840篇
  2002年   1692篇
  2001年   197篇
  2000年   175篇
  1999年   222篇
  1998年   317篇
  1997年   239篇
  1996年   239篇
  1995年   168篇
  1994年   167篇
  1993年   143篇
  1992年   90篇
  1991年   86篇
  1990年   70篇
  1989年   69篇
  1988年   62篇
  1987年   46篇
  1986年   42篇
  1985年   47篇
  1984年   60篇
  1983年   63篇
  1982年   70篇
  1981年   45篇
  1980年   35篇
  1979年   23篇
  1978年   20篇
  1977年   19篇
  1976年   13篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Immunization with amyloid-β (Aβ) peptide reduces amyloid load in animal studies and in humans; however clinical trials resulted in the development of a pro-inflammatory cellular response to Aβ. Apoptosis has been employed to stimulate humoral and Th2-biased cellular immune responses. Thus, we sought to investigate whether immunization using a DNA vaccine encoding Aβ in conjunction with an attenuated caspase generates therapeutically effective antibodies. Plasmids encoding Aβ and an attenuated caspase were less effective in reducing amyloid pathology than those encoding Aβ alone. Moreover, use of Aβ with an Arctic mutation (E22G) as an immunogen was less effective than wild-type Aβ in terms of improvements in pathology. Low levels of IgG and IgM were generated in response to immunization with a plasmid encoding wild-type Aβ. These antibodies decreased plaque load by as much as 36 ± 8% and insoluble Aβ42 levels by 56 ± 3%. Clearance of Aβ was most effective when antibodies were directed against N-terminal epitopes of Aβ. Moreover, immunization reduced CAA by as much as 69 ± 12% in TgCRND8 mice. Finally, high-molecular-weight oligomers and Aβ trimers were significantly reduced with immunization. Thus, immunization with a plasmid encoding Aβ alone drives an attenuated immune response that is sufficient to clear amyloid pathology in a mouse model of Alzheimer's disease.  相似文献   
22.
Context The assessment of ethical problem solving in medicine has been controversial and challenging. The purposes of this study were: (i) to create a new instrument to measure doctors’ decisions on and reasoning approach towards resolving ethical problems; (ii) to evaluate the scores generated by the new instrument for their reliability and validity, and (iii) to compare doctors’ ethical reasoning abilities between countries and among medical students, residents and experts. Methods This study used 15 clinical vignettes and the think‐aloud method to identify the processes and components involved in ethical problem solving. Subjects included volunteer ethics experts, postgraduate Year 2 residents and pre‐clerkship medical students. The interview data were coded using the instruments of the decision score and Ethical Reasoning Inventory (ERI). The ERI assessed the quality of ethical reasoning for a particular case (Part I) and for an individual globally across all the vignettes (Part II). Results There were 17 Canadian and 32 Taiwanese subjects. Based on the Canadian standard, the decision scores between Taiwanese and Canadian subjects differed significantly, but made no discrimination among the three levels of expertise. Scores on the ERI Parts I and II, which reflect doctors’ reasoning quality, differed between countries and among different levels of expertise in Taiwan, providing evidence of construct validity. In addition, experts had a greater organised knowledge structure and considered more relevant variables in the process of arriving at ethical decisions than did residents or students. The reliability of ERI scores was 0.70–0.99 on Part I and 0.75–0.80 on Part II. Conclusions Expertise in solving ethical problems could not be differentiated by the decisions made, but could be differentiated according to the reasoning used to make those decisions. The difference between Taiwanese and Canadian experts suggests that cultural considerations come into play in the decisions that are made in the course of providing humane care to patients.  相似文献   
23.
OBJECTIVE: To quantify the dietary calcium and vitamin D intake in adult renal-transplant recipients attending at a large teaching hospital in Ireland for follow-up. SETTING: Outpatient renal-transplant follow-up clinic. SUBJECTS: Fifty-nine adult renal transplant recipients (58% male) with a mean age of 46 years, a median transplant duration of 6 years, and a mean estimated glomerular filtration rate (eGFR) of 50 mL/min per 1.73 m2. Fifty-three percent were at National Kidney Foundation stage 3 chronic kidney disease, and 14% had stage 4 chronic kidney disease. INTERVENTION: This cross-sectional, observational study used a tailored food frequency questionnaire specific for calcium and vitamin D intake in Irish adults, which was completed during a face-to-face interview with each subject. MAIN OUTCOME MEASURE: The main outcome measure was the average daily dietary and supplemented calcium and vitamin D intake. RESULTS: The median interquartile range (IQR) dietary calcium intake was 820 mg/day (range, 576-1,177 mg/day), and was similar in men and women (recommended intake > or = 1,000 mg/day in adult men and nonmenopausal adult women, > or = 1,500 mg/day in menopausal women). Five participants received calcium supplementation. Overall, 59% of men and 64% of women had total calcium intakes below the recommended amounts. The median IQR estimated dietary vitamin D intake was 5.2 microg/day (range, 2.4-6.4 microg/day) in women, and 4.6 microg/day (range, 2.2-6.6 microg/day) in men (recommended intake, > or = 10 microg/day). Six subjects received vitamin D supplementation. Total vitamin D intakes were suboptimal in 91% of men and 87% of women. Dietary calcium and vitamin D intakes significantly correlated with each other, but neither was significantly related to eGFR category, and was similarly low in both presumed menopausal women and in the initial year posttransplantation. CONCLUSION: These findings suggest that dietary and total calcium and vitamin D intakes in adult renal-transplant patients are in many cases inadequate.  相似文献   
24.
Conclusions  Despite the utility and benefits that each imaging modality has to offer, it is easy to see why there is still no perfect choice for a noninvasive cardiac imaging modality to assist in the management of chest pain patients. All of the current imaging techniques have their own significant strengths and weaknesses when compared with other modalities. SPECT and echocardiography are wellestablished technologies that can directly assess the presence of myocardial ischemia and its functional consequence on RF; newer and more expensive techniques such as MDCT and CMR can directly assess coronary anatomy and have just started to be evaluated in the acute chest pain setting. There are no studies that directly compare these technologies, and more data are clearly needed before the question of whether anatomic imaging versus perfusion/function imaging is the better approach can be answered. Other comparisons such as relative safety, availability, logistics, and cost-effectiveness between the various technologies are also lacking. Of all of the imaging modalities discussed, MCE is the only portable technology. The images do not require expensive software or other technology for offline processing before interpretation, and any trained cardiologist can read the study at the bedside or, potentially, over the Internet, providing near-instantaneous results in the acute cardiac setting, where time is of the essence. MCE is also relatively cheap compared with other technologies, a potential advantage for payors but not necessarily for payees. How reimbursement rates and fee structures eventually affect clinical practice is also unknown. Despite these and other questions that need to be answered before any one technique will be used exclusively, the future of noninvasive cardiac imaging remains an exciting and ever-changing field. The adaptation of any one of these techniques into its proper role in the ED Journal of Nuclear Cardiology Wyrick and Wei 753 Volume 13, Number 6;749-55 Cardiac imaging in patients with chest pain will take considerably more time and effort in terms of research, money, and time-tested clinical experience.  相似文献   
25.
Smith Kevin C.  BA  BSc  MD  FACP  FRCPC    Melnychuk Michael  BSc  DDS 《Dermatologic surgery》2005,31(S4):1635-1637
Background. Injection of filler substances into the lips is painful, and many patients also find the injection of local or regional anesthesia into the lips painful.
Objective. To develop a highly effective and painless form of anesthesia to facilitate injection of filler substances into the lips.
Methods. Five percent lidocaine cream was applied simultaneously to the skin, vermilion, and mucosa of the lips (with the use of a barrier to keep the cream in contact with the mucosa and out of the rest of the mouth) for 20 to 30 minutes.
Results. Profound anesthesia of the lips was reliably produced, with no complications.
Conclusions. This "anesthetic cream block" is easier to perform and better tolerated than injectable anesthetics. Use of this technique is likely to expand the range of physicians who perform filler injections on the lips and will probably also expand the range of patients who wish to have filler injections done on their lips and who (because they had little or no discomfort) are willing to return for additional filler injections in the future.  相似文献   
26.
This study examined the use and effectiveness of the Alert assessment form. The form is part of the Alert system, used by one large acute care hospital to identify patients with a propensity for violence. All reported incidents of patient violence from August 1, 2003, through December 31, 2004, were included in patient charts. One hundred seventeen violent patient charts were reviewed and compared with 161 non-violent patient charts, randomly chosen from the same time period. Overall use of the Alert assessment form for violent and non-violent patients was 75.7% and 35.4%, respectively. The assessment form was found to have moderate sensitivity (71%) and high specificity (94%). It is reasonably effective in identifying potentially violent or aggressive patients when it is used according to protocol. Efforts to improve the tool are warranted, as is evaluation of its benefit in settings with low prevalence of violence. Also, greater effort must be taken to prevent violence once an aggressive patient has been identified.  相似文献   
27.
28.
We describe a novel human zinc finger cNDA, C2H2-171. This cDNA represents an mRNA which encodes a protein of 484 amino acids and a calculated molecular weight of 54 kD. Four zinc finger-like domains are found in the C-terminal end of the protein. At the N-terminus, C2H2-171 contains a POZ/tramtrack-like domain similar to that found in the tumor associated zinc finger proteins LAZ-3/BCL-6 and PLZ-F, as well as in non-zinc finger proteins. C2H2-171 RNA is preferentially expressed in the brain, and increases during the course of murine development, with maximal expression in the adult. C2H2-171 RNA is differentially expressed in brain regions, with the highest level of expression in the cerebellum. C2H2-171 RNA was expressed at high levels in primary cerebellar granule cell neurons compared to astrocytes. The gene encoding C2H2-171 is highly conserved in vertebrates, and maps to the terminus of human chromosome 1 (1q44-ter). This chromosomal location is associated with a number of cytogenetic aberrations including those involving brain developmental anomalies and tumorigenesis. These data suggest that C2H2-171 may play an important role in vertebrate brain development and function.  相似文献   
29.
Tremper  Kevin K. 《Journal canadien d'anesthésie》1990,37(1):Slxxvii-Slxxxviii
Canadian Journal of Anesthesia/Journal canadien d'anesthésie -  相似文献   
30.

Background  

Cerebrospinal fluid (CSF) pleocytosis may be seen in asymptomatic HIV-infected individuals. This finding complicates interpretation of CSF abnormalities when such individuals are evaluated for other central nervous system infections. The goal of this study was to determine the relationship between CSF pleocytosis, central nervous system (CNS) antiretroviral penetration, adherence to antiretroviral medication regimens, neurological symptoms and performance on neuropsychological tests.  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