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   13678篇
  免费   679篇
  国内免费   122篇
耳鼻咽喉   352篇
儿科学   677篇
妇产科学   599篇
基础医学   1022篇
口腔科学   440篇
临床医学   1103篇
内科学   3444篇
皮肤病学   211篇
神经病学   828篇
特种医学   590篇
外科学   3215篇
综合类   191篇
一般理论   1篇
预防医学   325篇
眼科学   464篇
药学   492篇
中国医学   26篇
肿瘤学   499篇
  2024年   11篇
  2023年   109篇
  2022年   205篇
  2021年   402篇
  2020年   261篇
  2019年   321篇
  2018年   403篇
  2017年   329篇
  2016年   565篇
  2015年   635篇
  2014年   695篇
  2013年   846篇
  2012年   1087篇
  2011年   1000篇
  2010年   624篇
  2009年   529篇
  2008年   916篇
  2007年   1073篇
  2006年   981篇
  2005年   970篇
  2004年   848篇
  2003年   633篇
  2002年   561篇
  2001年   98篇
  2000年   58篇
  1999年   65篇
  1998年   66篇
  1997年   45篇
  1996年   33篇
  1995年   27篇
  1994年   18篇
  1993年   10篇
  1992年   11篇
  1991年   10篇
  1990年   12篇
  1989年   4篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1975年   1篇
  1973年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Asthma and allergic rhinitis are common problems in children and the causative pollen allergens vary according to the geographical area. The aim of this study was to investigate patterns of sensitization to common inhalant allergens, especially pollens, in Turkish children living in the Trakya region and to determine differences between rural and urban areas. Allergen skin testing was prospectively performed on 539 children aged between 4 and 17 years with respiratory allergy. The reaction was considered to be positive if the mean wheal diameter was at least 3 mm greater than that of the negative controls. We detected positive skin reactions in 420 (77.9%) children. Two hundred and eighty-one (52.1%) mite, 277 (51.4%) pollen, 174 (32.3%) mold, 65 (12.1%) animal dander, 12 (2.2%) cockroach and 6 (1.1%) latex skin sensitivities were detected. Among the pollen allergies 173 were cereal pollen (32.1%), 170 grass pollen (31.5%) and 144 tree pollen allergies (26.7%). The most common positive skin test among the pollens was to cultivated wheat (Titicum vulgare) (n = 116, 21,5%), followed by rye grass (Lolium perenne) and orchard grass (Dactylis glomerata). Positive skin reactions to Alternaria, to Candida albicans, and to all pollens except Ulmus competris, Pinus sylvetris, Platanus vulgaris and Tilia platyphyllos, were higher in children with allergic rhinitis than in those with asthma. In children from rural areas, allergic skin reactivity was found to be more common against Candida albicans, sheep dander and all pollens except Corylus avellana, Fraxinus excelsior, Populus alba, Pinus sylvetris, Platanus vulgaris and Chenopodium album, than in urban children. Although Trakya is close to Greece and other Mediterranean countries, this study suggests that the pollens, which sensitize children, are not similar.  相似文献   
52.
Physical training is known to induce oxidative stress in individuals subjected to intense exercise. In this study, we investigated plasma malondialdehyde (MDA) levels and erythrocyte superoxide dismutase (SOD) activity of 25 young male footballers and a control group of similar age. Red blood cell (RBC) count, haemoglobin (Hb) and haematocrit (Hct) values, and copper (Cu) and zinc (Zn) levels were also examined. The maximal oxygen uptake (VO2max) of all subjects was determined in order to establish their functional capacity. The main finding of the present study was that plasma MDA levels, one of the most commonly used markers of lipid peroxidation, of this group of footballers aged under 21 decreased slightly when compared with those of the control group (p < 0.001). In contrast, erythrocyte SOD activity was higher in the footballer group than in the controls (p < 0.001). Footballers who are under regular training showed an improved antioxidant activity in comparison to sedentary controls. Plasma copper concentration, RBC count and Hb concentration of the footballer group were all significantly lower than those of the control group, (p < 0.001, p < 0.01, p < 0.01, respectively). Investigating the footballers' data with Spearman's correlation analyses, the correlation coefficients (r) between Zn/Cu ratio and SOD was positive (r=0.44; p < 0.05); and between VO2max and SOD (r=0.42; p < 0.05) were both positive. On the basis of statistical analysis, we suggest that regular exercise may be beneficial in cases of oxidative damage by reducing the amount of lipid peroxidation and increasing the activity of the antioxidant enzyme SOD.  相似文献   
53.
Self-etching dentin adhesive systems, a new generation of dental-bonding agents, were investigated for their ability to block nerve conductance in the rat sciatic nerve model. Clearfil SE Bond, Mac Bond and FL Bond were used as test materials. Isolated rat sciatic nerves obtained from female albino rats were placed between two electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials were recorded versus time before and after contact with the materials. Statistical analysis was performed using the Friedman and Wilcoxon Signed-Ranks tests (P = 0.01) to compare the mean percentage of inhibition between test materials versus time. All test materials were able to block nerve transmission rapidly (3.3 +/- 0.5, 5.1 +/- 2.3 and 8.0 +/- 1.9 min for SE Bond, Mac Bond and FL Bond, respectively). Significant differences were found between FL Bond and SE and Mac Bond (P < 0.01). These results indicated that the bonded systems tested, intended primarily as dentinal tubule occluders, may also exert some direct desensitizing effect on intratubular or pulpal nerve terminals in extremely deep cavities or pulpal microexposures, contributing to decreased postoperative pain.  相似文献   
54.
Influence of a self-etching primer on compound nerve action potentials   总被引:1,自引:0,他引:1  
The aim of this study was to evaluate the effect of self-etching primers on nerve conductance. A self-etching primer (One Up Bond F) which combines etching and bonding in one step, and a fifth-generation bonding agent (Prime&Bond NT ) were tested. Isolated rat sciatic nerves were placed between two platinum electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials (CAP) were recorded before and after contact with the materials. One Up Bond F caused total inhibition of the CAP within an average time of 7 min. All CAPs in this group were blocked irreversibly. As with Prime&Bond NT, the reduction in CAP was 45.9% after an application time of 15 min, after which readings were terminated. Recovery of the CAP in this group were maintained after rinsing with fresh tyrode solution. One Up Bond F elicited faster blocking of nerve conductance under the conditions of this model. In the context of dentin desensitization with bonding agents, the self-etching primer may be more effective, clinically.  相似文献   
55.
The aim of this study was to record sacral bone morphometry that may help in selection of the implant type and proper size in sacroiliac separation. For this reason, sacral lengths and width, the length of each sacral vertebrae, distances between cranial and caudal articular processes, vertical and transversal diameters of the cranial endplate, sacral tuberositas and articular surface areas were obtained from 11 dogs. Additionally, the transverse and vertical diameters of the bony structure and sacral canal were measured from six cross-sections. The data of the study were determined to be representative of the sacral values for average-sized dogs, which was confirmed statistically. The highest value was the sacral width among the linear measurements. The ventral sacral length was longer than the dorsal sacral length. The total lateral area of the sacral wing was measured as 677.46 (142.1)mm2. The transverse diameters of the first sacral vertebra important for screw implantation were 46.02 (4.33)mm and 44.18 (5.29)mm in the first and second cross-sections, respectively.  相似文献   
56.
BACKGROUND: Our main aim was to investigate the effects of melatonin (ME), possibly the most powerful free-radical scavenger, on the prevention of i.p. adhesion formation in rat uterine horn. Our secondary aim was to determine whether different methods of administration of ME were beneficial. METHODS: Animals were randomly assigned into seven groups, each consisting of 13 rats. Measured serosal injury was created using a standard technique. While control and two sham groups were not given ME, two of the remaining four groups were given a single dose of 10 mg/kg (2 mg) of ME i.p. immediately after injury and 30 min prior to injury respectively. In the two other groups, ME treatment was continued daily for 5 days. All animals were killed 2 weeks after surgery and adhesions were determined and scored by a examiner blinded to the test. RESULTS: The extent, severity and total scores of adhesion were found to be significantly reduced in all of the ME treatment groups when compared with control and sham groups. There were no statistically significant differences between the treatment groups. CONCLUSIONS: This study showed that even single dose ME therapy was effective in the prevention of post- operative i.p. adhesion formation.  相似文献   
57.
Based on direct sequencing information from 5UTR and NS5B regions, we identified subtype 1b as a predominant hepatitis C virus genome in Turkey, which affected more than 91% of 79 patients studied. Next, the full genome sequence of a Turkish 1b isolate was obtained by the cloning of polypeptide-encoding region into 7 overlapping fragments. Turkish 1b isolate, which was named HCV-TR1, comprises 9361 nucleotides, including 306 nucleotides of 5UTR, a single long open reading frame of 9033 nucleotides, and 22 nucleotides of 3UTR. When compared to HCV 1b polypeptide sequences available at GenBank, the predicted polypeptide displayed a total of 36 amino acid substitutions, of which 16 was specific for HCV-TR1 isolate. Despite these changes, major structural and functional motifs of HCV proteins were maintained in HCV-TR1. In contrast, HCV-TR1 displayed amino acid substitutions in 6 out of 9 major cytotoxic T-cell epitopes. These data suggest that HCV-TR1 encodes functionally intact viral proteins, but it also encodes altered viral epitopes, which may affect host immune-response.  相似文献   
58.
Left ventricular assist device (LVAD) implantation is frequently complicated by B-cell activation and allosensitization, posing a significant risk to successful transplant outcome. This study investigated whether B-cell hyperreactivity and alloantibody production in LVAD recipients involves T-cell dependent pathways. T-cell calcium flux and nuclear translocation of NFATc were used to determine states of T-cell activation. Flow cytometry was used to assess human T- and B-cell activation after culture with LVAD-derived biomaterial particles. Sera from LVAD recipients and controls were tested for the presence of anti-HLA antibodies, and for soluble CD40 ligand. LVAD-derived biomaterial induced rapid and sustained calcium flux into normal T cells, resulting in calcineurin-dependent nuclear translocation of NFATc. This resulted in increased T-cell expression of CD40 ligand and subsequent B-cell activation, which was reduced by inhibitors of T-cell activation (CsA or anti-CD25 mAb) or by anti-CD40 ligand mAb. LVAD recipients demonstrated higher frequencies of anti-HLA antibodies and serum levels of soluble CD40 ligand compared with heart failure controls. The results indicate that exposure of human mononuclear cells to LVAD-derived biomaterial leads to T-cell dependent B-cell activation via CD40--CD40 ligand interaction, and suggest that treatment with calcineurin inhibitors or monoclonal antibodies against either CD25 or CD40 ligand could be effective at preventing B-cell hyperreactivity and allosensitization after LVAD implantation.  相似文献   
59.
Congenital epulis is a very rare lesion found only in newborn infants. This tumor is multiple in about 10% of reported cases, rarely with the simultaneous involvement of the maxilla and mandibula, as in this article. In the presented case, light microscopy demonstrated large eosinophilic granular cells arranged in solid nests that are separated by thin fibrovascular areas. The tumors In the maxilla and mandibula were investigated with a panel of polyclonal and monoclonal antibodies, and using immunoperoxidase methods on formalin-fixed, paraffin-embedded sections. Immunohistochemical studies revealed strong and diffuse cytoplasmic staining for neuron specific enolase and vimentin. However, all other reactions were negative. These results suggest that the congenital epulis may be derived from uncommitted nerve-related mesenchymal cells.  相似文献   
60.
OBJECTIVE: To evaluate the expression of HSP70 and pS2 and to determine whether it may be an additional prognostic variable in the prediction of recurrence and survival in rectal adenocarcinomas. METHODS: The paraffin sections of 45 patients with rectal carcinoma who were treated with surgical resection were stained with HSP70 and pS2 antibodies by using the standard biotin immunoperoxidase method. Cytoplasmic staining for both antibodies was scored semiquantitatively. RESULTS: Only 16 (35.6%) tumors showed a positive cytoplasmic reaction with HSP70 antibody, while pS2 expression was observed in 26 (57.8%) tumors. There was an association between HSP70 and pS2 expression (P=0.002). No correlations were found between HSP70 and pS2 expression and tumor recurrence or overall survival and other prognostic factors. However, the type of surgical resection was significantly associated with pS2 expression status (P=0.013). Significant correlations were detected between tumor recurrence and other clinicopathologic parameters, such as clinical stage, lymph node involvement, and resection type (P=0.015, P=0.015, and P=0.03, respectively). Resection type was significantly associated with clinical outcome, recurrence, and metastasis (P=0.009, P=0.03, P<0.01, respectively). In addition, there was a statistically significant relationship between clinical stage and final outcome (P=0.005). CONCLUSIONS: The strong correlation between pS2 expression and incomplete surgical resection suggests that pS2 may be related to invasive tumor behavior and may also play a role in tumor recurrence, although this latter association did not reach statistical significance in this study. HSP70 expression does not appear to be related to tumor invasiveness or tumor recurrence.  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