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   42208篇
  免费   2392篇
  国内免费   101篇
耳鼻咽喉   657篇
儿科学   1879篇
妇产科学   1002篇
基础医学   5015篇
口腔科学   2045篇
临床医学   3762篇
内科学   8732篇
皮肤病学   1148篇
神经病学   3373篇
特种医学   1520篇
外科学   6549篇
综合类   155篇
一般理论   17篇
预防医学   2701篇
眼科学   1126篇
药学   2705篇
中国医学   194篇
肿瘤学   2121篇
  2024年   44篇
  2023年   361篇
  2022年   317篇
  2021年   810篇
  2020年   505篇
  2019年   827篇
  2018年   1381篇
  2017年   978篇
  2016年   1076篇
  2015年   1020篇
  2014年   1176篇
  2013年   1897篇
  2012年   3002篇
  2011年   3502篇
  2010年   1611篇
  2009年   1009篇
  2008年   2960篇
  2007年   3170篇
  2006年   3064篇
  2005年   3074篇
  2004年   2900篇
  2003年   2696篇
  2002年   2533篇
  2001年   850篇
  2000年   974篇
  1999年   575篇
  1998年   269篇
  1997年   236篇
  1996年   213篇
  1995年   170篇
  1994年   161篇
  1993年   139篇
  1992年   107篇
  1991年   87篇
  1990年   95篇
  1989年   90篇
  1988年   103篇
  1987年   63篇
  1986年   57篇
  1985年   71篇
  1984年   53篇
  1983年   40篇
  1982年   54篇
  1981年   46篇
  1980年   45篇
  1979年   38篇
  1978年   30篇
  1977年   38篇
  1976年   29篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background: The timely diagnosis of adhesive small bowel obstruction (SBO) can frequently be a clinical dilemma. The objective of this study was to evaluate the predictive factors for the necessity of operative treatment in adhesive SBO cases.

Method: The records of hospitalized adhesive SBO patients at Dicle University Hospital (DUH) between January 1998 and December 2001 were prospectively reviewed. The patients divided into two groups as a non-operative group (NOG) and an operative group (OG). The epidemiological, clinical, and laboratory features were evaluated as probable predictive factors for the timing of the surgical treatment. Predictive factors associated with the timing of the surgical treatment were determined using logistic regression models.

Results: A total of 180 patients [131(72.8%) male, 49(27.2%) female] with SBO were included in this study. One hundred and twenty patients (66.7%) were diagnosed with SBO and treated medically at the hospital. Sixty patients (33.3%) were diagnosed with SBO and underwent surgery. In univariate analyses, age (P = 0.008), length of period of symptoms (P < 0.001), high fever (P < 0.001), tachicardia (P < 0.001), tachypnea (P < 0.001), intractable pain (P < 0.001), hypo-active bowel sounds (P < 0.001), presence of rebound tenderness (P < 0.001), the persisting air-fluid levels in serial the plain abdominal radiographs (P < 0.001), leukocytosis (P < 0.001) and elevated CRP (P < 0.001) were found to be significantly associated with the predictive factors for the timing of operative treatment. In multivariate analyses, the presence of rebound tenderness [Odds Ratio (OR) = 57, 95% Confidence Interval (CI) = 3.5–922.4, p = 0.004], the persisting air-fluid levels (OR = 29, CI = 1.8–466.4, p = 0.018) were found significantly important as the predictive factors for the timing of operation.

Conclusion: Presence of rebound tenderness and the persisting air-fluid levels at admission or in hospital should be considered as predictive factors for the timing of an operation in adhesive SBO cases.  相似文献   
992.

Background

Nodding Syndrome is a seizure disorder of children in Mundri County, Western Equatoria, South Sudan. The disorder is reported to be spreading in South Sudan and northern Uganda.

Objective

To describe environmental, nutritional, infectious, and other factors that existed before and during the de novo 1991 appearance and subsequent increase in cases through 2001.

Methods

Household surveys, informant interviews, and case-control studies conducted in Lui town and Amadi village in 2001–2002 were supplemented in 2012 by informant interviews in Lui and Juba, South Sudan.

Results

Nodding Syndrome was associated with Onchocerca volvulus and Mansonella perstans infections, with food use of a variety of sorghum (serena) introduced as part of an emergency relief program, and was inversely associated with a history of measles infection. There was no evidence to suggest exposure to a manmade neurotoxic pollutant or chemical agent, other than chemically dressed seed intended for planting but used for food. Food use of cyanogenic plants was documented, and exposure to fungal contaminants could not be excluded.

Conclusion

Nodding Syndrome in South Sudan has an unknown etiology. Further research is recommended on the association of Nodding Syndrome with onchocerciasis/mansonelliasis and neurotoxins in plant materials used for food.  相似文献   
993.
BackgroundSevere hearing loss is a global problem affecting particularly developing countries. There is scarcity of recent published data on the epidemiology of childhood deafness in sub-Saharan Africa.ObjectiveTo determine the etiological profile of severe childhood deafness in Cameroon.MethodsProspective cross-sectional study of patients with a severe hearing loss that started before the age of 15 years. Detailed family and medical history was obtained; careful clinical, otological and audiological examinations were performed.ResultsA total of 582 patients with a severe hearing loss were examined. Prelingual deafness accounted for 75.1% (n = 437), with a mean age at medical diagnosis of 3.3 ± 1.2 years. This late presentation may be explained by limited parental awareness of signs raising suspicion of hearing loss, poor access to health care and the absence of neonatal screening for hearing loss in Cameroon. Identified genetic causes accounted for 14.8% (n = 86), putative environmental causes for 52.6% (n = 306) and unknown causes for 32.6% (n = 190). Amongst Genetic causes, the syndromic hearing loss accounted for 13.1% (n = 12) of cases, the rest being non syndromic (n = 74). Consanguineous families accounted for 5.7% (n = 33) of the whole sample, and 15.1% (n = 13) of genetic cases. No union between deaf parents was observed.ConclusionThese data highlight the possible predominance of putative environmental causes of childhood deafness in Cameroon, and emphasize the need for improved policies for prevention of infectious diseases and for neonatal hearing screening. However, further molecular analyses and targeted CT scan investigations are required to more accurately gauge the contribution of genetics etiologies.  相似文献   
994.
Brain abnormalities in Williams syndrome (WS) have been consistently reported, despite few studies have devoted attention to connectivity between different brain regions in WS. In this study, we evaluated corpus callosum (CC) morphometry: bending angle, length, thickness and curvature of CC using a new shape analysis method in a group of 17 individuals with WS matched with a typically developing group. We used this multimethod approach because we hypothesized that neurodevelopmental abnormalities might result in both volume changes and structure deformation. Overall, we found reduced absolute CC cross-sectional area and volume in WS (mean CC and subsections). In parallel, we observed group differences regarding CC shape and thickness. Specifically, CC of WS is morphologically different, characterized by a larger bending angle and being more curved in the posterior part. Moreover, although CC in WS is shorter, a larger relative thickness of CC was found in all callosal sections. Finally, groups differed regarding the association between CC measures, age, white matter volume and cognitive performance. In conclusions, abnormal patterns of CC morphology and shape may be implicated in WS cognitive and behavioural phenotype.  相似文献   
995.
Obesity is a major threat to public health worldwide, and there is now mounting evidence favoring a role for the central nervous system (CNS) in weight control. A causal relationship has been recognized in both monogenic (e.g., BDNF, TRKB, and SIM1 deficiencies) and syndromic forms of obesity [e.g., Prader–Willi syndrome (PWS)]. Syndromic obesity arising from chromosomal abnormalities, that typically also affect learning and development, are often associated with congenital malformations and behavioral characteristics. We report on nine unrelated patients with a diagnosis of learning disability and/or developmental delay (DD) in addition to obesity that were found to have copy number variants (CNVs) by single nucleotide polymorphism array‐based analysis. Each patient also had a distinct and complex phenotype, and most had hypotonia and other neuroendocrine issues, such as hyperphagia and hypogonadism. Molecular and clinical characterization of these patients enabled us to determine with confidence that the CNVs we observed were pathogenic or likely to be pathogenic. Overall, the CNVs reported here encompassed a candidate gene or region (e.g., SIM1) that has been reported in patients associating obesity and DD and/or intellectual disability (ID) and novel candidate genes and regions. © 2013 Wiley Periodicals, Inc.  相似文献   
996.
Behçet's disease (BD) is a chronic immune‐mediated systemic disease, characterized by oral and genital lesions and ocular inflammation. Several cytokine genes may play crucial roles in host susceptibility to BD, because the cytokine production capacity varies among individuals and depends on the cytokine gene polymorphisms. The association of the interleukin (IL)‐2 gene polymorphisms with the susceptibility to BD was investigated in this study. DNA samples were obtained from a Turkish population of 97 patients with BD and 76 healthy control subjects. Polymorphisms of IL‐2 gene at position ?330 and +166 were determined using the polymerase chain reaction with sequence‐specific primers. In the patients with BD, there was a significantly increased frequency of IL‐2 ?330 GT genotype. Interestingly, we demonstrated that the frequencies of IL‐2 ?330 GT and IL‐2 + 166 GG genotypes were increased in BD patients with ocular involvement, whilst IL‐2 ?330 TT genotype was significantly decreased. Also, analysis of allele frequency demonstrated that the presence of G allele at position +166 of IL‐2 seems to be a risk factor for ocular involvement. These results reveal that IL‐2 ?330 GT genotype may be a susceptibility factor for BD, whereas IL‐2 ?330 TT genotype seems to display a protective association with BD. Additionally, IL‐2 gene polymorphisms might be associated with ocular involvement in BD.  相似文献   
997.
Background: The aim of this study is to evaluate the effects of caffeine and/or estrogen deficiency on ligature‐induced bone loss (BL), trabecular bone area (TBA), and postextraction bone healing (BH). Methods: Rats were assigned into one of the following groups (15 each): 1) control = non‐ingestion of caffeine/sham surgery; 2) caffeine = ingestion of caffeine/sham surgery); 3) ovariectomized (OVX) = non‐ingestion of caffeine/ovariectomy; or 4) caffeine/OVX = ingestion of caffeine/ovariectomy. The rats were under caffeine administration for 65 days and/or estrogen deficiency for 51 days. On day 21 after ovariectomy, one first mandibular molar received a ligature and the contralateral tooth was not ligated. The first maxillary molars were extracted 8 days before sacrifice. BL, TBA, the positive cells for tartrate‐resistant acid phosphatase (TRAP), receptor activator of nuclear factor‐κB ligand (RANKL), and osteoprotegerin (OPG) were analyzed in the furcation area of mandibular molars. Histometric BH and gene expression of bone morphogenetic protein (BMP)‐2, BMP‐7, osteopontin, and bone sialoprotein were evaluated in alveolar sockets. Results: The caffeine group presented the greatest BL and the OVX group the highest number of TRAP‐positive (TRAP+) cells around ligated teeth (P <0.05). The control group presented higher TBA and BH than the other groups (P <0.05). All test groups presented higher RANKL/OPG+ cells than the control group around ligated/unligated teeth. The OVX and caffeine/OVX groups presented a greater number of TRAP+ cells around unligated teeth than the control group (P <0.05). There were no differences among groups for gene expression (P >0.05). Conclusions: Caffeine increased BL in ligated teeth. Caffeine and/or estrogen deficiency decreased TBA in the unligated teeth and reduced BH after tooth extraction.  相似文献   
998.
Background: Polycystic ovarian syndrome (PCOS) is a hormonal disorder of females of reproductive age that impacts their oral and systemic health. The aim of this study is to evaluate interleukin‐17A (IL‐17A), IL‐17F, IL‐17A/F, and IL‐17E (IL‐25) levels in gingival crevicular fluid (GCF), saliva, and serum of non‐obese females with PCOS and with either a clinically healthy periodontium or gingivitis. Methods: Thirty‐one females with PCOS, 30 females with PCOS and gingivitis, and 12 systemically and periodontally healthy females participated in the study. Clinical periodontal measurements, body mass index, and Ferriman‐Gallwey score (FGS) (a measure of hirsutism in females) were recorded. Circulating levels of sex hormones, cortisol, and insulin were also determined. Levels of IL‐17 cytokines were measured by enzyme‐linked immunosorbent assay. Results: The general linear model multivariate analysis, adjusting for age or plaque index, showed that the two groups with PCOS had higher concentrations of IL‐17A, IL‐17F, and IL‐17A/F in serum and higher levels of IL‐17A and IL‐17F in GCF and saliva but lower serum IL‐17E than systemically healthy females. Levels of IL‐17E were lowest in females with PCOS and gingivitis who also had the highest FGS. Serum IL‐17A and IL‐17F levels correlated positively with FGS and periodontal probing depth (all ρ >0.33; P <0.005). Serum IL‐17E showed the reverse relationship and also correlated negatively with IL‐17A (ρ >?0.28; P <0.05). Conclusions: IL‐17 levels are altered in non‐obese females with PCOS and may influence gingival inflammation. Additional studies are warranted to clarify the relationship between PCOS and gingivitis.  相似文献   
999.
Taurodontism is a morpho‐anatomical abnormality in the shape of a tooth. An enlarged pulp chamber, apical displacement of the pulpal floor and no constriction at the level of the cemento‐enamel junction are the characteristic features. Special care is required in all aspects of endodontic treatment of a taurodontal tooth, including identifying the orifice, canal exploration, cleaning, shaping and obturation of the root canal. This case report describes the successful endodontic treatment of a taurodontic mandibular second premolar with five root canals.  相似文献   
1000.
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