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   2375篇
  免费   164篇
  国内免费   9篇
耳鼻咽喉   43篇
儿科学   67篇
妇产科学   37篇
基础医学   361篇
口腔科学   191篇
临床医学   132篇
内科学   560篇
皮肤病学   115篇
神经病学   114篇
特种医学   84篇
外科学   304篇
综合类   20篇
一般理论   1篇
预防医学   240篇
眼科学   59篇
药学   131篇
中国医学   22篇
肿瘤学   67篇
  2023年   9篇
  2022年   64篇
  2021年   105篇
  2020年   67篇
  2019年   63篇
  2018年   94篇
  2017年   75篇
  2016年   72篇
  2015年   106篇
  2014年   84篇
  2013年   122篇
  2012年   185篇
  2011年   212篇
  2010年   112篇
  2009年   101篇
  2008年   131篇
  2007年   161篇
  2006年   98篇
  2005年   92篇
  2004年   72篇
  2003年   78篇
  2002年   56篇
  2001年   42篇
  2000年   46篇
  1999年   41篇
  1998年   20篇
  1997年   11篇
  1996年   8篇
  1995年   6篇
  1993年   5篇
  1992年   22篇
  1991年   15篇
  1990年   25篇
  1989年   14篇
  1988年   15篇
  1987年   10篇
  1986年   7篇
  1985年   16篇
  1984年   10篇
  1982年   5篇
  1980年   4篇
  1979年   5篇
  1978年   3篇
  1974年   8篇
  1973年   6篇
  1971年   5篇
  1969年   7篇
  1968年   4篇
  1965年   4篇
  1960年   3篇
排序方式: 共有2548条查询结果,搜索用时 31 毫秒
101.
102.

Purpose

To describe the morphofunctional characteristics of elite mixed martial arts athletes.

Methods

Eight male Brazilian athletes (aged: 31 ± 5 years; training experience: 5 ± 1 years; height: 1.77 ± 0.05 m; body mass: 82.1 ± 9.6 kg) with national training experience were subjected to anthropometric evaluation to estimate body composition and somatotype, and maximal strength (1 RM) in squat and bench press, abdominal and upper limb endurance, and lower limb power were determined.

Results

Body fat levels of 13.4 ± 5.6 %, lean mass levels of 69.6 ± 4.6 %, and mesomorphic component (6.4 ± 0.8) were observed. Athletes performed 42 ± 14 sit-ups and 37 ± 9 push-ups, and remained for 35 ± 10 s in the flexed-arm hang test. Athletes reached 2.19 ± 0.31 m in the horizontal jump test, and obtained absolute 1-RM values of 80 ± 15 kg and 68.5 ± 6.0 kg and relative values of 1.00 ± 0.2 kg/kg and 0.84 ± 0.10 kg/kg in bench press and squat tests, respectively.

Conclusion

Results indicate body fat levels in accordance with other studies, high lean body mass, and a predominantly mesomorphic component. Abdominal and upper limb endurance were classified as excellent, while results of the flexed-arm hang test were similar to previous data. Mixed martial arts athletes’ lower limb performance in the horizontal jump was classified as weak. Lower levels of maximal strength were obtained in squat and bench press tests.
  相似文献   
103.
104.
PURPOSE: The aim of this study was to evaluate the effectiveness of previous dental substrate treatments on the bond strength of two self-etching adhesives. MATERIALS AND METHODS: One hundred bovine incisors were sectioned at the cementoenamel junction. The labial tooth surface was ground to obtain flat superficial dentin. Teeth were randomly divided into two groups (n = 50): Clearfil Protect Bond and One Up Bond F. The specimens of each group were subdivided into five groups, according the dental substrate treatment, and then the adhesive system was applied as follows (n = 10): C: control, without previous treatment; TA: 37% phosphoric acid etching on enamel and dentin for 15 s; PA: 37% phosphoric acid etching only on enamel for 15 s; SB: Al2O3 sandblasting on dental surface; EDTA: enamel and dentin conditioning with 24% EDTA gel, pH 7.0. Resin composite blocks were fixed to the dental surfaces with dual-polymerized resin cement. Samples were sectioned in the mesiodistal direction and were trimmed to reduce the cross-sectional area to approximately 1.2 mm2. They were tested at a crosshead speed of 0.5 mm/min on a testing machine. Microtensile bond strength values from enamel, superficial dentin, and deep dentin were compared. Mean microtensile bond strength values were expressed in MPa and were analyzed by two-way ANOVA (2 x 3 x 5) and Tukey's tests. RESULTS: A significant difference was observed for interaction (p = 0.00001) among the factors. The highest mean bond strength to enamel was found with previous phosphoric acid etching, and to dentin when EDTA was previously applied. CONCLUSION: The most indicated previous treatment for increasing the bond strength to enamel and dentin simultaneously is EDTA for both self-etching adhesive systems used.  相似文献   
105.
Regional odontodysplasia (RO), also known as ghost teeth, is an unusual nonhereditary developmental anomaly of tooth formation that characteristically affects enamel and dentin formation of the primary and/or permanent dentition. In the present paper, we report a case of RO affecting a 7-year-old boy, with 9 years of follow-up. During this time, progressive development of dental tissue was observed, including complete root formation. However, delayed dental eruption was evident. In view of these findings, we discuss the clinical presentation, pathogenesis, differential diagnosis, and treatment of RO.  相似文献   
106.
PURPOSE: To evaluate a square-thread design implant and compare the bone-implant contact percentage between immediate-loaded and nonloaded implants (controls) in nonhuman primates. MATERIALS: Five nonhuman primates each received 3 implants, with a total of 5 control implants and 10 immediate-loaded implants in posterior regions of the mouth. Ninety days after surgery (and function was appropriate), block sections of the implants were removed and sectioned in 200-mum thick pieces. The block sections were stained with modified Masson for evaluation of the bone-implant contact percentage. RESULTS: One of the immediate-loaded implants failed. The bone-implant contact percentage of control implants ranged from 50.34% to 64.13% and averaged 56.3%. The bone-implant contact percentage of immediate-loaded implants ranged from 43.23% to 75.72%, with an average of 62.4%. Two implants had lower bone-implant contact percentage than the others, and when these are not included in the evaluation, the bone-implant contact percentage average increased to 67.6%. CONCLUSIONS: Immediate-loaded implants in the nonhuman primates often have a higher bone-implant contact percentage at 90 days than unloaded implants. The bone remodeling is different for loaded implant-bone interfaces than for unloaded conditions. However, 1 immediate-loaded implant failed, and 2 implants had lower bone-implant contact percentage than controls. Therefore, although there are benefits of immediate loading, there appear to also be some risks.  相似文献   
107.
BACKGROUND: Irritable bowel syndrome (IBS) is a symptom-based disorder characterized by abdominal pain related to altered bowel habit. We evaluated the predictive power of 2 genetic markers of hypolactasia, C/T_13910 and G/A_22018, in IBS patients with and without lactose intolerance in order to gain insight into the role of lactose intolerance in IBS. METHODS: Seventy five patients (59F/16M, mean age: 49.6+/-14.2 years) with an IBS diagnosis based on Rome II criteria and 272 healthy individuals, where 74 (58F/16M, 54.1+/-10.9 years) were matched-controls, were evaluated. IBS and healthy individuals were genotyped for the C/T_13910 and G/A_22018 polymorphisms nearby the lactase-phlorizin hydrolase gene. Hydrogen breath test (HBT) with gas chromatography was performed in IBS patients to assess for lactose intolerance. RESULTS: Of the 75 IBS patients, 28 (37%) were defined as lactose intolerants. The grade/severity of symptoms after an oral lactose load were positively correlated to the expiratory H2 excretion (P<0.001). Alleles and genotypes frequencies from C/T_13910 and G/A_22018 were not significantly different between IBS patients and control individuals (P>0.05;NS). Presence of the C and G allele were positively associated with a higher expiratory hydrogen excretion and more intense gastrointestinal symptoms (P<0.001). Considering these polymorphisms as a diagnostic test for lactose intolerance in IBS patients, presence of the CC and GG genotypes were estimated to have, a sensitivity of 100% and 96%, respectively; and a specificity of 83% and 79%, positive predictive value of 76% and 73%, and negative predictive value of 100% and 97%. CONCLUSIONS: In IBS patients, genotyping of C/T_13910 and G/A_22018 polymorphisms predicts gastrointestinal symptoms after lactose ingestion and are a diagnostic tool for lactose intolerance.  相似文献   
108.
A significant percentage of patients with failed renal graft are candidates for retransplantation. The outcomes of retransplantation are poorer than those of primary transplantation and sensitization is documented to be a major reason. The management of a failed allograft that is not immediately symptomatic is still very controversial. The aim of this study was to determine the impact of the failed allograft nephrectomy on a subsequent transplantation and its importance in the sensitization. We performed a retrospective analysis of the local prospective transplantation registry of the outcome of 126 second kidney transplantations among 2438 transplantations performed in our unit between June 1980 and March 2013, comparing those who underwent allograft nephrectomy prior to retransplantation with those who retained the failed graft. Primary endpoints were graft and patient survival. The levels of panel-reactive antibodies (PRA) and rate of acute rejections on retransplantation outcomes were also studied. Among the 126 patients who underwent a second renal transplantation, 76 (60.3%) had a prior graft nephrectomy (Group A), whereas 50 (39.7%) kept their failed graft (Group B). Group A showed significantly more positive PRA levels when compared with the other group (38% vs 10%; P < .001), as measured before the most recent transplantation, and a higher rate of acute rejection (19% vs 5.6%; P = .016). There were 28 (36%) renal allograft losses for Group A and 18 (36%) for those who had not had transplantectomy (P = not significant [NS]). One-, 3-, and 5-year graft survival rates were 96.6%, 90.7%, and 83.4%, respectively, in Group A and 95%, 82%, and 68.4%, respectively, in Group B, with no statistical differences (P = .19). Five-year actuarial patient survival rates in the 2 groups was 89.3% and 82.8%, respectively (P = .55). Multivariate analysis showed that PRA level and delayed graft function (DGF) had a statistically significant influence on graft survival (P = .028; odds ratio [OR] = 1.029; and P = .024; OR = 8.6), irrespective of whether the patient had graft nephrectomy or not. The allosensitization indicated by PRA increases after transplantectomy and leads to a higher incidence of acute rejection after retransplantation. Nephrectomy of failed allograft does not seem to significantly influence the survival of a subsequent graft. The decision to remove or retain a failed graft in the context of retransplantation should thus be based on known clinical indications for the procedure.  相似文献   
109.

Purpose

Patients undergoing hemodialysis (HD) present persistent inflammation and protein-energy wasting (PEW), which contributes to high rates of mortality. This study aimed to assess the effects of a resistance exercise training program (RETP) on inflammation and PEW in HD patients.

Methods

Thirty-seven patients (56.7 % men, 45.9 ± 14.1 years, 23.5 ± 3.9 kg/m2) performed 6 months of intradialytic RETP. Plasma adhesion molecules levels (ICAM-1 and VCAM-1) were measured using the enzyme immunometric assay, and interleukin-6 (IL-6), C-reactive protein, and tumor necrosis factor-alpha by ELISA. Anthropometric, physical capacity, and PEW (simultaneously presence of: BMI <23 kg/m2, serum albumin <3.8 g/dL, and reduced arm muscle area) were analyzed.

Results

There was a reduction of ICAM-1 [(1,934.1 pg/mL (1,031.8–2,875.0) vs. 1,571.1 pg/mL (447.1–2,985.5), p < 0.05], VCAM-1 [5,259.51 pg/mL (3,967.4–6,682.4) vs. 3,062.11 pg/mL (2,034.0–5,034.4), p < 0.05], and CRP levels (2.3 ± 0.9 to 1.6 ± 0.6 pg/mL, p < 0.001) after 6 months of RETP. Body composition improved, albumin increased (3.7 ± 0.3 to 3.9 ± 0.2, p < 0.05), and the number of patients presenting PEW was decreased (p = 0.005).

Conclusions

Resistance exercise program for 6 months seems to be effective in reducing inflammation and PEW of HD patients. The universal trial number of this study is U1111-1139-1326.  相似文献   
110.
Dengue virus (DENV) is the most widespread arthropod-borne virus, with the number and severity of outbreaks increasing worldwide in recent decades. Dengue is caused by genetically distinct serotypes, DENV-1–4. Here, we present data on DENV-1, isolated from patients with dengue fever during an outbreak in Senegal and Mali (Western Africa) in 2015–2019, that were analyzed by sequencing the envelope (E) gene. The emergence and the dynamics of DENV-1 in Western Africa were inferred by using maximum likelihood and Bayesian methods. The DENV-1 grouped into a monophyletic cluster that was closely related to those from Southeast Asia. The virus appears to have been introduced directly into Medina Gounass (Suburb of Dakar), Senegal (location probability = 0.301, posterior = 0.76). The introduction of the virus in Senegal occurred around 2014 (95% HPD = 2012.88–2014.84), and subsequently, the virus moved to regions within Senegal (e.g., Louga and Fatick), causing intense outbreaks in the subsequent years. The virus appears to have been introduced in Mali (a neighboring country) after its introduction in Senegal. In conclusion, we present evidence that the outbreak caused by DENV-1 in urban environments in Senegal and Mali after 2015 was caused by a single viral introduction from Asia.  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