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   1208篇
  免费   83篇
  国内免费   4篇
耳鼻咽喉   19篇
儿科学   27篇
妇产科学   38篇
基础医学   162篇
口腔科学   14篇
临床医学   108篇
内科学   211篇
皮肤病学   8篇
神经病学   98篇
特种医学   86篇
外科学   146篇
综合类   23篇
一般理论   1篇
预防医学   122篇
眼科学   10篇
药学   75篇
中国医学   4篇
肿瘤学   143篇
  2022年   8篇
  2021年   17篇
  2020年   11篇
  2019年   15篇
  2018年   13篇
  2017年   16篇
  2016年   15篇
  2015年   17篇
  2014年   24篇
  2013年   42篇
  2012年   64篇
  2011年   51篇
  2010年   37篇
  2009年   37篇
  2008年   54篇
  2007年   61篇
  2006年   58篇
  2005年   45篇
  2004年   43篇
  2003年   46篇
  2002年   30篇
  2001年   35篇
  2000年   37篇
  1999年   34篇
  1998年   29篇
  1997年   18篇
  1996年   20篇
  1995年   19篇
  1994年   13篇
  1993年   22篇
  1992年   28篇
  1991年   31篇
  1990年   32篇
  1989年   35篇
  1988年   25篇
  1987年   27篇
  1986年   19篇
  1985年   14篇
  1984年   13篇
  1983年   11篇
  1980年   9篇
  1978年   9篇
  1977年   7篇
  1976年   11篇
  1974年   6篇
  1972年   7篇
  1965年   5篇
  1957年   6篇
  1956年   5篇
  1954年   5篇
排序方式: 共有1295条查询结果,搜索用时 15 毫秒
101.
BACKGROUND: Platelet concentrates prepared from whole blood are generally suspended in a standard volume of 50 to 60 mL of plasma and can be stored thus at 20 to 24 degrees C for up to 5 days. In vitro studies suggested that this plasma volume could be reduced to 30 to 35 mL without impairing platelet function. STUDY DESIGN AND METHODS: This study evaluated whether platelets stored for 5 days in a reduced volume (30-35 mL) of plasma maintained their in vivo viability, hemostatic function, and recovery in recipients. Paired autologous platelet survival studies were done in 20 adult volunteers to assess platelet viability. A rabbit ear bleeding-time model was used to compare the hemostatic effectiveness of human platelet concentrates stored for 5 days in the standard or reduced volume of plasma. Platelet recovery was compared in thrombocytopenic hospital patients. RESULTS: Paired platelet survival studies indicated no significant difference between the values in platelet concentrates stored for 5 days in the reduced volume of plasma and the values in those stored in the standard volume. In the animal model, there was no significant difference in the bleeding times achieved by either set of platelet concentrates. The platelet count increments in thrombocytopenic patients were measured. The platelet count increments in patients who received reduced-volume platelet concentrates were as good as the increments achieved in patients given standard-volume concentrates. CONCLUSION: The in vivo viability, recovery, and hemostatic function of platelets collected in polyvinylchloride plastic containers and stored in 30 to 35 mL of plasma for 5 days are maintained as well as those of platelets stored in 50 to 60 mL of plasma.  相似文献   
102.
BackgroundAn impairment of the 5-fluorouracil (5-FU) catabolic pathway, represented by alterations in the dihydropyrimidine dehydrogenase (DPYD) gene, is considered a crucial factor contributing to the development of 5-FU-related toxicity. The β-ureidopropionase (BUP1) enzyme catalyzes the final step in the 5-FU catabolic pathway; however, alterations in the UPB1 gene coding for the BUP1 enzyme have not yet been analyzed in fluoropyrimidine (FP)-treated patients suffering from 5-FU-related toxicity.MethodsWe have performed a mutation analysis of the entire coding sequence of UPB1 based on denaturing high-performance liquid chromatography in 113 cancer patients treated by FP-containing regimes. These patients included 67 individuals suffering from severe 5-FU-related toxicity and 46 individuals with excellent tolerance of chemotherapy.ResultsNine UPB1 variants were detected in the subpopulation of patients with severe toxicity, including a novel mutation affecting the coding sequence (c.872_873 + 11del13). An analysis of UPB1 variants on 5-FU-related toxicity in the population of all analyzed patients revealed an association between the c.-80C > G (rs2070474) variant and gastrointestinal toxicity. A strong positive correlation was found between the carriers of the c.-80 GG genotype and the development of severe (grade 3–4) mucositis (OR = 7.5; 95% CI = 2.60 – 21.60; p = 0.0002).ConclusionOur results suggest that UPB1 variants may contribute to the development of 5-FU-related toxicity in some FP-treated patients; however, the role of UPB1 alterations is probably less significant than that of DPYD alterations.  相似文献   
103.
104.
Xiaozhou Zhou  John E. Novotny  Liyun Wang   《BONE》2009,45(4):704-710
Solute transport in the lacunar–canalicular system (LCS) is essential for bone metabolism and mechanotransduction. Using the technique of fluorescence recovery after photobleaching (FRAP) we have been quantifying solute transport in the LCS of murine long bone as a function of loading parameters and molecular size. However, the influence of LCS anatomy, which varies among animal species, bone type and location, age and health condition, is not well understood. In this study, we developed a mathematical model to simulate solute convection in the LCS during a FRAP experiment under a physiological cyclic flow. We found that the transport rate (the reciprocal time constant for refilling the photobleached lacuna) increased linearly with canalicular number and decreased with canalicular length for both diffusion and convection. As a result, the transport enhancement of convection over diffusion was much less sensitive to the variations associated with chick, mouse, rabbit, bovine, dog, horse, and human LCS anatomy, when compared with the rates of diffusion or convection alone. Canalicular density did not affect transport enhancement, while solute size and the lacunar density had more complicated, non-linear effects. This parametric study suggests that solute transport could be altered by varying LCS parameters, and that the anatomical details of the LCS need systemic examination to further understand the etiology of aged and osteoporotic bones.  相似文献   
105.
PURPOSE: Angelman syndrome (AS) is a neurogenetic disorder characterized by developmental delay and a frequently refractory epileptic condition. Valproate, clonazepam and/or phenytoin are said to be the most effective antiepileptic drugs (AEDs) against the seizures in AS. Experience with the newer AEDs is very limited despite their better safety profile and tolerability. Considering its favorable side effect profile and its effectiveness against both partial and generalized seizures, we hypothesized that lamotrigine (LTG) might be more efficacious and better tolerated. METHODS: Potential patients for this retrospective study were identified from the epilepsy clinics at Notre-Dame, Sainte-Justine, and Yale New Haven hospitals. Patients were included in the study if they had AS along with refractory seizures. The medical record of each patient was reviewed with interest on seizure types, previous AEDs and response to LTG. RESULTS: Five patients (2M, 3F) were included in this study. Age at LTG ranged from 10 to 33 years old. All had >or=2 seizure types, mainly generalized tonic-clonic, myoclonic seizures, and atypical absences. Previously tried AEDs included valproic acid (5), benzodiazepines (5), phenytoin (4), carbamazepine (3), and topiramate (1). One patient had pancreatitis on phenytoin, one had worsened seizures on carbamazepine, and one developed hepatic encephalopathy on valproic acid. Three patients became seizure-free with LTG (9, 20, and 36 months FU), one was seizure-free for 1 year with subsequent loss of efficacy, and one showed >50% reduction in myoclonic seizures (20 months FU). No side effects were reported. CONCLUSION: LTG can be efficacious and well tolerated in patients with AS.  相似文献   
106.
Capillary electrophoresis with end-column amperometric detection (CE-EC) was used to determine the regional distribution of norepinephrine (NE) in the hearts of sympathetically innervated (control) and chemically sympathectomized rats. Key features of the method are (i) the sample preparation and clean-up step that involved the application of off-line solid phase extraction (SPE) with a 95% NE recovery and (ii) the use of a diamond microelectrode for detection. NE was quantified in the left and right ventricle, the ventricular septum, and the left and right atrium. The NE concentration in the atria was three to five times higher than in the ventricles and ventricular septum of control rats. Basal NE levels in the left and right ventricle and the ventricular septum were reduced to below the detection limit (0.034 microg/g tissue) in tissues treated with the neurotoxin, 6-hydroxydopamine (6-OHDA), while only a moderate reduction was observed in the left and right atrium. Importantly, the diamond microelectrode provided low and stable background current and low peak-to-peak noise 相似文献   
107.
BACKGROUND: To develop strategies for the prediction of sepsis outcome systemic procalcitonin (PCT) levels were correlated with various clinical parameters. METHODS: PCT levels and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were assessed on the day of sepsis diagnosis in a large series (n = 160) of patients developing sepsis after major visceral surgery. RESULTS: In multivariate analysis, systemic PCT and the APACHE II score could be identified as independent early predictive indicators of lethal sepsis. Combining both indicators at sepsis onset, a prognosis score could be calculated using binary logistic regression analysis allowing the identification of high- and low-risk groups. While 71% of the high-risk patients died of sepsis, 77% of patients assigned to the low-risk group survived the septic complication (sensitivity 71%, specificity 77%). CONCLUSION: Calculation of the prognosis-score allowed for an early prediction of the septic course with high sensitivity and specificity. This information could aid in deciding on adequate treatment strategies.  相似文献   
108.
109.
Oncologists often manage cancer-associated symptoms including pain. When symptoms are severe, anesthesia-pain medicine (APM) and/or palliative medicine (PM) can effectively treat symptoms. Nevertheless, symptom management may be suboptimal, leading to diminished quality of life (QOL). We assessed the value of PM vs. APM consultation in cancer patients referred for pain management alone. Patients referred to an APM-based Cancer Pain Clinic (CPC) over an 8-month period were evaluated by PM or APM based on the first available appointment. Symptoms and QOL were assessed by the MD Anderson Symptom Inventory and Linear Analog Self-Assessment at baseline and 4-6 weeks after initial encounter. Data were analyzed on an available-case basis. Sixty-two patients (37 PM, 25 APM) completed the initial survey, with 48 patients (31 PM, 17 APM) completing followup. Mean pain score improved from 7.97 to 5.47 in the PM group (P < 0.0001) and from 7.1 to 4.5 (P = 0.29) in the APM group. The PM group demonstrated a clinically significant improvement in 8/19 symptoms vs. 3/19 in the APM group and in 3/5 QOL parameters in the PM group vs. 1/5 in the APM group. Our small sample size weakens our power and ability to detect significant differences between the groups. Only one follow-up symptom-assessment point was obtained. PM consultation is as effective as APM in improving cancer pain but may be more effective with symptom management and improving QOL.  相似文献   
110.
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