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   876676篇
  免费   72022篇
  国内免费   2996篇
耳鼻咽喉   12877篇
儿科学   24805篇
妇产科学   25259篇
基础医学   125981篇
口腔科学   25753篇
临床医学   77415篇
内科学   166796篇
皮肤病学   17107篇
神经病学   70913篇
特种医学   35790篇
外国民族医学   184篇
外科学   137381篇
综合类   27135篇
现状与发展   6篇
一般理论   266篇
预防医学   67763篇
眼科学   20883篇
药学   66209篇
  20篇
中国医学   2567篇
肿瘤学   46584篇
  2018年   7913篇
  2015年   8407篇
  2014年   11980篇
  2013年   17507篇
  2012年   23761篇
  2011年   25020篇
  2010年   14620篇
  2009年   13655篇
  2008年   23365篇
  2007年   25326篇
  2006年   25204篇
  2005年   24856篇
  2004年   24192篇
  2003年   23303篇
  2002年   22335篇
  2001年   36139篇
  2000年   36813篇
  1999年   31230篇
  1998年   9415篇
  1997年   8744篇
  1996年   8658篇
  1995年   8167篇
  1994年   7866篇
  1992年   26754篇
  1991年   26166篇
  1990年   25700篇
  1989年   24732篇
  1988年   23260篇
  1987年   22929篇
  1986年   21778篇
  1985年   21129篇
  1984年   16412篇
  1983年   14017篇
  1982年   8860篇
  1981年   8206篇
  1980年   7675篇
  1979年   16740篇
  1978年   12118篇
  1977年   10182篇
  1976年   9333篇
  1975年   10154篇
  1974年   12643篇
  1973年   12144篇
  1972年   11542篇
  1971年   10687篇
  1970年   10221篇
  1969年   9911篇
  1968年   8906篇
  1967年   8232篇
  1966年   7653篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Four years of data are reported on the drug cost avoidance and the net cost savings associated with a clinical pharmacy intervention program. In 1986 the pharmacy department at a 324-bed nonprofit community medical center began a clinical intervention program by adding one full-time equivalent for providing clinical services. A new clinical pharmacist position was created in 1988. A reorganization in 1989 resulted in further increases in staffing, including the creation of a clinical coordinator position to oversee the intervention program, and in administrative time. Staff pharmacists self-report a broad range of interventions on a clinical documentation form. During the period 1986-1989, monthly data on the number of types of interventions recommended, the percentage of recommendations accepted by the medical staff, and drug cost avoidance were tabulated. Cost avoidance was calculated by subtracting the cost of therapy ordered by the physician from the cost of therapy initiated as a result of the intervention. Net drug cost savings were calculated by subtracting from cost avoidance the cost of pharmacist time required for performing the interventions. The average number of interventions per month ranged from 170 in 1986 to 292 in 1990. During an 18-month period before the clinical coordinator was added, average monthly cost avoidance and net savings were $4932 and $3739, respectively. Average monthly cost avoidance increased to $6244 and savings to $4644 in a 12-month period after the clinical coordinator was added. A four-year study of a clinical intervention program showed that the dollar value and impact outlasted the initial success expected for such programs.  相似文献   
992.
993.
Summary: Purpose: Quantitative MRI techniques provide an unparalleled opportunity to examine in vivo the relationship between the extent and laterality of hippocampal pathology and associated neuropsychological deficits. The purpose of this study was to examine the nature of the relationship between quantitative measures of hippocampal pathology and neuropsychological measures, using a multivariate approach. Methods: We examined the relationship between two MRI measures of hippocampal structure; hippocampal volumes (HCvol) and T2 relaxation times (HCT2), and memory performance, in 80 presurgical temporal lobe epilepsy patients. Results: As a group, patients with left hippocampal sclerosis (LHS) performed more poorly that those with right hippocampal sclerosis (RHS) on immediate and delayed prose recall. In the group as a whole, right hippocampal volume was significantly correlated with the delayed recall of a complex figure. None of the verbal memory test scores were significantly correlated with the right or left HCvol or HCT2 measures. However, stepwise multiple regression analyses indicated that up to a third of the variation in specific test scores could be explained by the quantitative MRI hippocampal measures in conjunction with chronological age, and age at onset of habitual epilepsy. Left hippocampal measures explained 24% of the variance in the story-recall tasks, while right hippocampal measures explained 18% of the variance in a design-learning task and 32% of the variance in a figure-recall task. Conclusions: Our results provide some support for the lateralised model of material specific memory deficits, but suggest that a number of demographic and epilepsy-related factors may interact with the extent and laterality of hippocampal pathology in shaping the nature of the associated neuropsychological deficit.  相似文献   
994.
Replication-defective retroviruses expressing the t- neu oncogene, or a hybrid protein with the neu tyrosine kinase linked to the external region of the human epidermal growth factor receptor ( egfr-neu ), were used to establish lines of murine oligodendroglial precursor cells. Differentiation of the t- neu lines into myelin-associated glycoprotein (MAG)-positive oligodendrocytes was induced by dibutyryl cAMP, and the egfr-neu line showed limited differentiation in vitro upon withdrawal of epidermal growth factor. Cerebellar granule cell neurons expressed mitogens for the cell lines. Upon transplantation into demyelinated lesions, t- neu line cells engaged with the demyelinated axons whereas the egfr-neu line cells differentiated further and ensheathed the axons. These cell lines thus interact with neurons in vitro and in vivo and can be used as tools to define the molecules involved in different stages of neuron-glia interaction.  相似文献   
995.
996.
α-Methylene-γ-butyrolactones with Molluscicidal Activity The α-methylene-γ-butyrolactones 1-28 were tested in vitro for molluscicidal activity against Biomphalaria glabrata. The racemic compound 25 shows the best activity. The synthesis was carried out by modified Reformatzky reaction of the corresponding carbonyl compounds and bromomethylacrylic acid ethyl ester. 7-10, 17 and 22-27 have been synthesized for the first time.  相似文献   
997.
998.
Introduction: Suramin is a synthetic polysulfonated naphthylurea which has been used for the treatment of African trypanosomiasis and onchocerciasis, but since the mid-1980s has received attention as a possible antiretroviral and antineoplastic agent. Objective: This clinical trial of suramin was undertaken as a phase I/II study in patients with hormone-refractory prostate cancer, with the hypothesis that the intensity of therapy with suramin could be increased significantly if measures were undertaken to maintain the plasma concentrations of the drug under 300 μg/ml. Methods: We report the clinical results of this trial, wherein patients were treated at three different targeted plasma suramin concentrations (275, 215 and 175 μg/ml) for varying periods of time (2, 4 or 8 weeks), with delivery of the drug by continuous intravenous infusion. Results: The major toxicity observed in this trial was neurologic, consisting of a motor and sensory peripheral neuropathy that resulted in both paresis and paralysis of the limbs. Nearly all of this severe (CTEP grade III, IV) neurologic toxicity was observed in the patients treated at a plasma suramin concentration of 275 μg/ml for 4 or more weeks. A single patient treated at 215 μg/ml for 8 weeks developed moderate (CTEP grade III) proximal lower extremity weakness, and no patient treated at 175 μg/ml developed this toxicity. The second most common toxicity observed was infection of the central venous catheter. The overall response rate for all of the evaluable patients was 17% (13 of 75 patients). In addition, prostate-specific antigen (PSA)-defined responses were observed in six patients receiving therapy at 175 μg/ml, but these responses were confounded by cessation of therapy with flutamide during suramin treatment. Conclusions: In summary, although plasma suramin concentrations were maintained below 300 μg/ml, neurologic toxicity nonetheless occurred with high frequency in patients treated at 275 μg/ml for 4 or more weeks. Therapy at 215 and 175 μg/ml was in general well tolerated, but central venous catheter-related infection, as well as the inconvenience and expense of continuous infusional therapy, make this method of drug delivery impractical. Only moderate antitumor activity was observed during this trial, but it is possible that both continuation of flutamide and flutamide withdrawal during suramin therapy confounded the assessment of suramin’s activity in hormone-refractory prostate cancer. Received: 9 June 1995/Accepted: 18 March 1996  相似文献   
999.
A series of tylosins and acyl derivatives of 23-O-demycinosyltylosin (DMT) were initially tested for in vitro antibacterial activity and serum levels in squirrel monkeys (po) and mice (iv). Overall, the DMT compounds were more active in vitro than the tylosins. Two tetraacylated DMTs, Sch 37644 and Sch 38646, were selected from the initial studies for further evaluation and compared to erythromycin and A-56268 (6-O-methyl erythromycin). Sch 37644 and Sch 38646 were 2 to 8-fold less potent in vitro against Gram-positive bacteria than erythromycin and A-56268. In squirrel monkeys, Sch 37644 (AUC, 19.7 micrograms.hour ml) and A-56268 (21.6 micrograms.hour/ml) had similar serum levels following po administration of 20 mg/kg, while Sch 38646 (11.8 micrograms.hour/ml) and erythromycin (1.5 micrograms.hour/ml) had lower levels. In mice administered 200 mg/kg orally, Sch 37644 (AUC, 19.4 micrograms.hour/ml) and Sch 38646 (15.4 micrograms.hour/ml) had higher serum levels than erythromycin (5.7 micrograms.hour/ml). A-56268 was the most active po macrolide in mouse protection studies (PD50S) against Staphylococci and Streptococci, while Sch 37644 and Sch 38646 were similar to erythromycin.  相似文献   
1000.
1. The effects of acute or chronic morphine treatment on the changes in blood pressure and pulse rate in response to ganglionic stimulation or blockade and to vagal stimulation, and of isolated atria to field stimulation or noradrenaline, were studied. 2. In pithed rats, intravenously injected hexamethonium significantly depressed the blood pressure responses to sympathetic nerve stimulation. The ganglionic blocking effects of hexamethonium were significantly greater in chronically morphine-treated rats, but were not significantly affected by acute morphine administration in naive animals. 3. Intravenous administration of nicotine dose-dependently increased blood pressure and pulse rate. The magnitudes of these changes were not significantly affected by acute or chronic morphine pretreatment. 4. Studies with rat isolated atrial preparations revealed that the changes in atrial contractile rate and force in response to noradrenaline or field stimulation were not influenced by either acute or chronic morphine treatment. 5. Cervical vagal stimulation produced voltage- or frequency-dependent decreases in pulse rate and blood pressure. The responses were not significantly affected by chronic morphine treatment. 6. These findings suggest that the site of the changes in sympathetic function following prolonged exposure to the opiate appears to be on the preganglionic nerve fibres.  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