首页 | 官方网站   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   38368篇
  免费   2126篇
  国内免费   201篇
医药卫生   40695篇
  2023年   317篇
  2022年   693篇
  2021年   1437篇
  2020年   801篇
  2019年   1219篇
  2018年   1500篇
  2017年   889篇
  2016年   916篇
  2015年   1146篇
  2014年   1577篇
  2013年   1952篇
  2012年   2897篇
  2011年   3198篇
  2010年   1690篇
  2009年   1518篇
  2008年   2405篇
  2007年   2464篇
  2006年   2327篇
  2005年   2105篇
  2004年   1875篇
  2003年   1675篇
  2002年   1555篇
  2001年   458篇
  2000年   464篇
  1999年   425篇
  1998年   283篇
  1997年   238篇
  1996年   200篇
  1995年   162篇
  1994年   135篇
  1993年   149篇
  1992年   216篇
  1991年   205篇
  1990年   193篇
  1989年   123篇
  1988年   109篇
  1987年   88篇
  1986年   116篇
  1985年   110篇
  1984年   85篇
  1983年   67篇
  1982年   65篇
  1981年   60篇
  1979年   49篇
  1978年   43篇
  1976年   35篇
  1974年   35篇
  1972年   36篇
  1971年   37篇
  1970年   37篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
A comparative study of an O2-diffusion cathode and a H2-diffusion anode has been performed to ascertain the limiting processes, when they are combined in a flow alkaline fuel cell with hydroperoxide ion generation. The linear sweep voltammograms and the impedance diagrams of both electrodes show large differences. The cathode reaction is charge transfer-controlled up to current densities of at least 1 A cm?2, whereas the dissociative adsorption, charge transfer and diffusion of H2 appear to limit the anode reaction. The anode, with limiting current densities of about 90 and 150 mA cm?2 for 1.0 and 6.0 M KOH, respectively, then clearly controls the hydroperoxide ion production in the fuel cell. Diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy reveal that, the carbon of the H2-diffusion anode does not undergo significant oxygen functionalisation during hydroperoxide ion generation in the fuel cell.  相似文献   
82.
We thank Dr Villata et al. for their thought-provoking comments.Their concern about the suitableness to choose combined endpointsin clinical trials deserves some comment.  相似文献   
83.
84.
INTRODUCTION: The management of children receiving small bowel grafts involves potentially life-threatening complications that affect their nutritional status. The aim of this paper was to define these factors and their influence on nutritional outcome. PATIENTS AND METHODS: Patients with intestinal failure (IF) who received an isolated small bowel transplantation (SBT) or small bowel/liver transplantation (SBLT) at our hospital during the last 6 years were reviewed for weight Z-score, biochemical nutritional parameters, total parenteral nutrition (TPN) weaning, catheter-related sepsis, rejection and steroid treatment. RESULTS: Twenty patients, 11 females and 9 males, received a SBT or a SBLT and survived the postoperative period; in the present study we only included 11 children with follow-up periods longer than 1 year. Seven males and 4 females with a mean age of 4.5 years (range, 1 to 20 years) received 6 SBLT and 5 SBT. Nine (82%) were weaned from TPN to an amino-acid or peptide enteral formula during the first 6 months after surgery. During the first year there was a significant increase in total protein from 5.11 +/- 1.8 mg/dl to 6.1 +/- 1.5 mg/dl (p < 0.05) and an increase in albumin from 3.8 +/- 0.9 mg/dl to 4.5 +/- 1.1 mg/dl (p < 0.05). There was an increase in weight Z-score in 9 patients (82%) during the first year. Mean Z-score improved from - 2.6 +/- 1 at transplant to - 1.0 +/- 0.6 (p < 0.05) after 1 year. Three patients (27.2%) had at least one rejection period, which was treated with steroids alone or in combination. Mean weight Z-score 1 year after surgery was - 0.9 +/- 0.6 for patients without rejection and - 1.24 +/- 0.8 for those with at least one rejection episode treated with steroids (p > 0.1). Four patients (36%) had at least one catheter-related sepsis episode. Mean weight Z-score 1 year after surgery was - 1.01 +/- 0.6 for patients without catheter-related sepsis and - 1.24 +/- 0.8 for those with at least one catheter-related sepsis episode (p > 0.1). CONCLUSIONS: There was a significant improvement in weight Z-score and biochemical nutritional parameters 1 year after receiving a small bowel graft. No influence of steroids or catheter-related sepsis on children's nutritional status was noted 1 year after surgery, although this point will need further evaluation.  相似文献   
85.
In this study, we analyzed the spatiotemporal expression patterns of the high-molecular weight (MAP2a and b) and low-molecular weight (MAP2c and d) cytoskeletal microtubule-associated protein-2 (MAP2) isoforms with Western blotting, and the cellular localization of the high-molecular weight MAP2 isoforms with immunocytochemistry in the hippocampi of 1- to 21-day-old rats. Moreover, the temporal profile (from 30 min to 1 week) of MAP2 isoform reactivity to kainic acid-induced status epilepticus was studied in P9 rats. During development, the expression of the high-molecular weight MAP2 isoforms significantly increased, while the low-molecular weight isoforms decreased, the most prominent changes occurring during the second postnatal week. This developmental increase in the high-molecular weight MAP2 expression was also confirmed with immunocytochemistry, which showed increased immunoreactivity, particularly in the molecular layers of the dentate gyrus, and in CA1 and CA3 stratum radiatum. In 9-day-old rats, status epilepticus resulted in a rapid transient increase (about 210%) in the high-molecular weight MAP2 expression, without any effect on the low-molecular weight MAP2. Moreover, disturbed dendritic structure in the CA1 and CA3 stratum radiatum was manifested as formation of varicosities 3h after the kainic acid treatment. The strictly developmentally regulated MAP2 isoform expression suggests different functional roles for these proteins during the postnatal development in the rat hippocampus. Moreover, high-molecular weight MAP2s may play a role in nerve cell survival during cell stress.  相似文献   
86.

Objectives  

This study was designed to assess the prevalence of adverse drug reactions (ADRs) in the internal medicine wards of two teaching Hospitals, identify the most common ADRs, the principal medications involved, and determine the risk factors implicated in the occurrence of such ADRs.  相似文献   
87.
Ischemic stroke occurs in 0.2-0.4% of patients undergoing left heart catheterization, and is responsible for 5-10% of the mortality associated with the procedure. The main predisposing factors for this complication are female gender, complex atherosclerotic plaques in the ascending aorta, and peripheral arterial disease. The possibility of timely intervention with reperfusion therapy supports close clinical monitoring during the immediate post-catheterization period. The cardiologist should be familiar with the various types of stroke reperfusion therapy and its indications according to the time interval between catheterization and the stroke. The decision should be discussed with neurology and neuroradiology.  相似文献   
88.
We report on the vaginal mucosal folds (VMF) at the urethral external meatus. Resection of the VMF reduces the dispersed micturition and other urinary symptoms. EDITORIAL COMMENT: The investigators describe the presence of a vaginal mucosal fold (VMF) just dorsal to the urethral meatus and its relationship to voiding abnormalities. VMF were found on physical examination in 8.9% of the clinic population, all of whom complained of dispersed micturition, and 79% also experienced other voiding abnormalities. The complaint of dispersed micturition was successfully treated with excision of the VMF, and the other associated symptoms were improved. This structure should be routinely looked for on physical examination, especially in patients with voiding symptoms. Only further investigation of this newly described entity at other centers around the world will determine the incidence of the anatomic finding and the prevalence of associated voiding disturbances across different populations.  相似文献   
89.
New methods for simplified quantitation of effector-target conjugation have been developed. The binding unit (BU) is defined as the number of target cells required to bind a specified percentage of effector cells. The number of binding units is determined from binding isotherms in which effector conjugate frequencies are measured by holding constant the number of effector cells and by varying the number of target cells. Alternately, a binding unit can be defined as the number of effector cells required to bind a specified percentage of target cells. In this case, BU is computed from binding isotherms in which target conjugate frequencies are measured at different values of effector cells by holding constant the number of target cells. Also, the area under the curve (AUI) of these isotherms is another index that can be used as an overall measure of the binding capacity in an effector-target system. The experimental values of BU and AUI determined from effector and target isotherms agree well with theoretical predictions based on our previously developed binding model (J. Immunol. Methods (1992) 155, 133–147). The relationship between BU and AUI, and procedures to determine these parameters are shown. The value of these indices to express effector-target conjugation quantitatively has been confirmed by determining the values of BU and AUI for the NK-K562 effector-target system.  相似文献   
90.
Background: Reduction in salivary secretion is the hallmark of Sjögren's syndrome (SS). Calmodulin (CaM) and calmodulin binding proteins (CaMBPs) play a key role in the secretory process of saliva. Recent studies have suggested that SS‐B, an autoantibody associated with SS, is a CaMBP. This finding suggests that CaMBP may contribute to the loss of saliva in SS. To better understand the role(s) of these proteins in SS, the purpose of this study was to compare salivary CaMBPs in Sjögren's patients and controls. Methods: Saliva samples were collected from 20 patients and 20 age‐, race‐, and gender‐matched controls. CaM overlay was used to identify CaMBPs in saliva of patients and controls. Results: Higher number of salivary CaMBPs was observed among patients than controls. Conclusions: The increased number of salivary CaMBPs in SS may suggest a potential role for these proteins in the pathogenesis of the disease.  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-23

京公网安备 11010802026262号