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   48207篇
  免费   2584篇
  国内免费   132篇
耳鼻咽喉   763篇
儿科学   2014篇
妇产科学   846篇
基础医学   6176篇
口腔科学   1160篇
临床医学   3120篇
内科学   11358篇
皮肤病学   1574篇
神经病学   4118篇
特种医学   1333篇
外科学   7163篇
综合类   388篇
一般理论   16篇
预防医学   3933篇
眼科学   1302篇
药学   2989篇
中国医学   224篇
肿瘤学   2446篇
  2023年   348篇
  2022年   317篇
  2021年   1196篇
  2020年   597篇
  2019年   1319篇
  2018年   2108篇
  2017年   1285篇
  2016年   1163篇
  2015年   1033篇
  2014年   1266篇
  2013年   2166篇
  2012年   3580篇
  2011年   4061篇
  2010年   1974篇
  2009年   1190篇
  2008年   2951篇
  2007年   3035篇
  2006年   2787篇
  2005年   2834篇
  2004年   2659篇
  2003年   2609篇
  2002年   2291篇
  2001年   1604篇
  2000年   2102篇
  1999年   1109篇
  1998年   321篇
  1997年   235篇
  1996年   200篇
  1995年   183篇
  1994年   126篇
  1993年   117篇
  1992年   172篇
  1991年   129篇
  1990年   124篇
  1989年   125篇
  1988年   134篇
  1987年   94篇
  1986年   77篇
  1985年   114篇
  1984年   97篇
  1983年   95篇
  1982年   73篇
  1981年   62篇
  1980年   65篇
  1979年   79篇
  1978年   81篇
  1977年   64篇
  1976年   58篇
  1975年   61篇
  1973年   60篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
In this study, an examination was made of the sites in the brain of the rat at which the injection of cholecystokinin octapeptide (CCK-8) would alter food intake. Rats fasted for 24 hr received intracerebral injections of CCK-8 (1 nmol) or an equal volume of saline (0.5 microliters), into various sites in the brain through permanently implanted stainless steel cannulae. After prior acclimatisation to individual plexiglass compartments, latency to feed, as well as consumption of food and water during 0-20, 20-40 and 40-60 min after the injection, were recorded. The available food was the standard rat pellets, to which the animal otherwise had constant daily access. With this paradigm, active sites at which CCK-8 suppressed feeding were defined as sites at which consumption of food for 0-20 min was reduced by 25% or more, or the latency to feed was increased by 3 min or more after the injection of CCK-8, as compared to the effect of the injection of saline, made at the same site. Such active sites were most densely distributed in the rostral diencephalon, e.g. hypothalamus, the medial pontine area and lateral medulla, in the vicinity of the nucleus tractus solitarii (NTS). By grouping data for injections according to histologically identified sites, statistical analysis of groups of injections confirmed that these three major areas of the brain were active with regard to the suppression of feeding by CCK-8. These data suggest that CCK may not only initiate satiety messages, as a circulating hormone at peripheral sites, but also participate in the conduction of such information to the target in the brain by serving as a neurotransmitter in the lateral medulla (e.g. NTS), medial pontine area (e.g. relay station between the NTS and hypothalamus) and the lateral hypothalamus, where local release of CCK-8 after stomach loading has been observed.  相似文献   
72.
Summary Genes involved in cancer generation are usually tumor suppressors and oncogenes. Progressive genetic alterations in these genes are involved in the mechanisms of tumorigenesis. In prostate cancer, additionally several chromosomal loci that should harbor mutated genes have been proposed. Some genes have been found altered in prostate cancer, such as PTEN, TP53, AR, RNASEL (HPC1), ELAC2 (HPC2), CDKN2A and MSR1 and those can be natural targets for new strategies of treatment. Besides, gene therapy has been suggested to be suitable for prostate cancer treatment. This approach includesex vivo corrective therapy, suicide, and antisense therapy.  相似文献   
73.
Abstract: Background: The laryngeal mask airway (LMA) can be used in general anaesthesia without neuromuscular block. The laryngeal tube (LT) is a new airway device with similar airway features as LMA. LT is provided with a distal cuff to prevent regurgitation. In this study we compared the LMA and LT concerning patient and user aspects. Methods: Sixty patients with ASA (American Society of Anestesiologists) score 1–2 scheduled for minor surgery were randomized to be ventilated either through LMA or LT. After insertion, the number of insertion attempts, and “positioning” and “airway-assessment” was evaluated. The patients reported on “sore throat” after 30 and 60 minutes and the day after anaesthesia. Results: Gender and mean age were equal in both groups. The first insertion attempt was successful in 25 of 28 patients randomised to LMA and in 23 of 27 patients randomised to LT. LMA was evaluated to be easier in “positioning” whereas no difference in “sore throat” was reported. Conclusion: We found no difference between the LMA and the LT in terms user and patient friendliness and safety.  相似文献   
74.
AIM: To evaluate the effects of oral continuous 17beta-estradiol plus norethisterone acetate (E2/NETA) replacement therapy on abdominal subcutaneous fat, serum leptin level (SLL) and body composition in postmenopausal women. MATERIALS AND METHODS: A 6-month, prospective, randomized, double-blind and placebo-controlled study was conducted. Forty-three healthy naturally postmenopausal women aged 43-65 years were randomly assigned to receive E2/NETA (2 mg E2 plus 1 mg NETA, n = 22) or placebo (n = 21). Fasting SLL by enzyme-linked immunosorbent assay, subcutaneous abdominal fat thickness (STh) by ultrasound and the anthropometric indices of body weight (BW), body mass index (BMI), waist and hip circumference (WC, HC) and waist-to-hip ratio (WHR) were recorded at the beginning and the end of the study. RESULTS: After 6 months of therapy, BW and SLL increased in the placebo group (p = 0.043 and 0.033, respectively). WC, HC and STh decreased significantly in the E2/NETA group (p = 0.002, 0.006 and 0.000, respectively) and they were also significantly lower in women receiving E2/NETA than in women taking placebo (p = 0.000, 0.034 and 0.000, respectively). At baseline, SLL and STh were positively correlated with all anthropometric indices except WHR. CONCLUSION: Oral continuous combined regimen of E2/NETA significantly reduced central fat accumulation as assessed by WC and STh, and attenuated the increase in SLL. The observed changes in SLL were highly and positively related to changes in STh. The oral continuous combined E2/NETA regimen appears to have protective effects on cardiovascular function and probably on metabolic diseases by its slimming effect upon WC in postmenopausal women.  相似文献   
75.
Objective The purpose of this study is to analyze clinical aspects and disease-free survival (DFS) in children less than 3 years of age diagnosed with low-grade astrocytoma. Methods In a period of 24 years (1980–2004), a total of 43 (5.4%) children were registered with these characteristics. Twenty-three patients had pilocytic astrocytoma, 18 diffused, and 2 mixed. Thirty-one (72.1%) children had incomplete surgical tumor resection and 12 (27.9%) had a complete tumor resection. Twelve (27.9%) patients had cranial radiotherapy and 17 (39.5%) received chemotherapy. Overall survival was recorded in 23 (53%). DFS was 50% at 250 months of follow-up for the whole group. DFS for the supratentorial group was 60% at 250 months, whereas, for the infratentorial, it was 22% at 120 months (p = 0.008). Conclusion The only favorable prognostic pattern was the supratentorial presentation. Radiotherapy and chemotherapy did not alter the outcome.  相似文献   
76.
复合珊瑚羟基磷灰石人工骨的研制及其成骨效应   总被引:12,自引:1,他引:11  
目的 自行研制复合珊瑚羟基磷灰石人工骨并评估其成骨效应。方法 取南海澄黄滨珊瑚碳酸钙在特定条件下经过“热液交换反应”,制成单纯珊瑚羟基磷灰石(coralline Hydroxyapatite,CHA)人工骨,并将其与基因重组骨形态发生蛋白(rhBMP2)和几丁糖复合制成了三种复合珊瑚羟基磷灰石(composite Coralline Hydroxyapatite,CCHA)人工骨,将此三种不同配型的复合人工骨和单纯CHA人工骨分别植入四组24只SD大白鼠肌肉内。手术后2、4、6、8周取材进行组织学观察,计数高倍单位视野内的成骨细胞数量和炎性细胞数量。采用SPSS8.0统计软件处理系统分析。结果 术后各时期取材结果显示:B组(CHA rhBMP2)和D组(CHA rhBM2P 几丁糖)的单位视野内成骨细胞数量明显多于A组(单纯CHA)和C组(CHA 几丁糖):而C组和D组的单位视野内炎性细胞数量明显少于A组和B组。即D组人工骨的单位视野内的成骨细胞数量多、炎性细胞少。结论 rhBMP2-几丁糖/CHA复合人工骨不但具有显著的成骨诱导作用,还具有炎症反应轻及持续的诱导成骨作用,是一良好的骨移植替代物。  相似文献   
77.
MUC-1基因在胃癌和外周血中的表达及临床意义   总被引:1,自引:0,他引:1  
目的:检测胃癌MUC-1的表达情况及其与临床分期和转移的相关性。方法:应用逆转录聚合酶链反应(RT-PCR)和免疫组化方法检测胃癌活检标本和外周血中MUC-1基因和蛋白的表达水平。结果:在56例胃癌病例中MUC-1 mRNA阳性表达率为48.2%,MUC-1蛋白阳性表达率为53.6%,临床分期中I和II期病人阳性表达率MUC-1 RNA为33.3%,MUC-1蛋白为40%,而-Ⅲ期病人则分别高达65.4%和69.2%,二者差异有显著性意义(P<0.05),在淋巴结转移的患者中外周血的癌细胞MUC-1高表达,阳性率为73%,结论:MUC-1是一种较好反映胃癌恶性程度和转移性的肿瘤标志物。  相似文献   
78.
Ganciclovir (GCV) prophylaxis or pre-emptive therapy significantly reduce the rate of cytomegalovirus (CMV) disease and viremia, but increase the potential for emergence of ganciclovir-resistant CMV strains. The inhibitor concentration at 50% (IC(50)) of GCV from 156 CMV isolates from 59 renal or heart transplant recipients was calculated by means of a rapid phenotypic susceptibility assay. Twenty-seven strains were from 14 patients undergoing GCV therapy. The IC(50) was higher in patients under the prophylaxis regimen. One CMV strain, from a heart transplant recipient, became GCV-resistant after 1 month of therapy (IC(50)=13.7 micromol/l). These data, together with clinical and virological markers, suggested that a switch to foscarnet was necessary, and good evolution was observed. Thus, assay of CMV susceptibility to GCV could be helpful in clinical management.  相似文献   
79.
Computerized information systems, especially decision support systems, have become an increasingly important role in medical applications, particularly in those where important decision must be made effectively and reliably. But the possibility of using computers in medical decision making is limited by many difficulties, including the complexity of conventional computer languages, methodologies and tools. Thus a conceptual simple decision making model with the possibility of automating learning should be used. In this paper we introduce a cardiological knowledge-based system based on the decision tree approach supporting the mitral valve prolapse determination. Prolapse is defined as the displacement of a bodily part from its normal position. The term mitral valve prolaps (PMV), therefore, implies that the mitral leaflets are displaced relative to some structure, generally taken to be the mitral annulus. The implications of the PMV are the following: disturbed normal laminar blood flow, turbulence of the blood flow, injury of the chordae tendinae, the possibility of thrombus's composition, bacterial endocarditis, and finally hemodynamic changes defined as mitral insufficiency and mitral regurgitation. Uncertainty persists about how it should be diagnosed and about its clinical importance. It is our deep belief that the echocardiography enables properly trained experts armed with proper criteria to evaluate PMV almost 100%. But unfortunately, there are some problems concerned with the use of echocardiography. In that manner we have decided to start a research project aimed at finding new criteria and enabling the general practitioner to evaluate PMV using conventional methods and to select potential patients from the general population. To empower one to perform needed activities we have developed a computer tool called ROSE (computeRised prOlaps Syndrom dEtermination) based on algorithms of automatic learning. This tool supports the definition of new criteria and the selection of potential PMV-patients.  相似文献   
80.
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