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   3628篇
  免费   208篇
  国内免费   2篇
耳鼻咽喉   138篇
儿科学   214篇
妇产科学   35篇
基础医学   361篇
口腔科学   153篇
临床医学   331篇
内科学   635篇
皮肤病学   43篇
神经病学   522篇
特种医学   55篇
外科学   474篇
综合类   19篇
一般理论   4篇
预防医学   276篇
眼科学   73篇
药学   171篇
中国医学   1篇
肿瘤学   333篇
  2023年   17篇
  2022年   35篇
  2021年   56篇
  2020年   40篇
  2019年   48篇
  2018年   73篇
  2017年   49篇
  2016年   88篇
  2015年   70篇
  2014年   88篇
  2013年   195篇
  2012年   201篇
  2011年   215篇
  2010年   123篇
  2009年   142篇
  2008年   221篇
  2007年   237篇
  2006年   205篇
  2005年   253篇
  2004年   249篇
  2003年   221篇
  2002年   214篇
  2001年   30篇
  2000年   27篇
  1999年   40篇
  1998年   58篇
  1997年   46篇
  1996年   34篇
  1995年   42篇
  1994年   37篇
  1993年   41篇
  1992年   36篇
  1991年   25篇
  1990年   25篇
  1989年   15篇
  1988年   15篇
  1987年   9篇
  1986年   24篇
  1985年   20篇
  1984年   18篇
  1983年   34篇
  1982年   40篇
  1981年   15篇
  1980年   26篇
  1979年   15篇
  1978年   19篇
  1977年   15篇
  1976年   15篇
  1975年   12篇
  1974年   10篇
排序方式: 共有3838条查询结果,搜索用时 15 毫秒
71.
We report an illustrative case of presurgical evaluation for epilepsy surgery, where the three-dimensional reconstructed magnetic resonance imaging played a pivotal role in determining the exact location of the subdural strip electrodes in temporomesial area. The tip of one the frontal strip electrodes was actually recording the temporopolar ictal activity. This contributed conclusively to the decision for surgical treatment and to the excellent outcome.  相似文献   
72.
We investigated regional cerebral glucose metabolic rates (rCMRgluc) with positron emission tomography using 2-[18F]fluoro-2-deoxy-D-glucose (FDG) in 7 monozygotic twin pairs discordant for Alzheimer's disease (AD). Ten healthy volunteers with comparable mean age and educational level served as controls. In the hippocampus, the mean +/- SD rCMRgluc were 0.20 +/- 0.03 micromol/ml/min for the demented twins, 0.21 +/- 0.03 micromol/ml/min for their non-demented co-twins, and 0.23 +/- 0.02 micromol/ml/min for the controls. The mean hippocampal rCMRgluc was reduced in the demented twins (p = 0.006), compared with the controls. In the lateral temporal cortex, the mean +/- SD rCMRgluc were 0.27 +/- 0.05, 0.28 +/- 0.04, and 0.32 +/- 0.02 micromol/ml/min, respectively. These mean rates were reduced both in the demented (p = 0.02) and the non-demented (p = 0.01) twins, compared with the controls. In conclusion, in the demented twins, the reduction of rCMRgluc was detected in the hippocampus and lateral temporal cortex, i.e. the 2 brain areas which show early changes in pathological and imaging studies in AD. Their non-demented co-twins showed milder reductions, which may be an indication of genetic susceptibility for dementia, and an early sign of a dementing illness in them.  相似文献   
73.
Rationale Serotonin (5-HT) is involved in the control of eating behaviour by inhibiting food intake. Obese women with binge-eating disorder (OB-BED) were recently found to have reduced 5-HT transporter binding. Objectives The aim of this study was to investigate the effect of a successful treatment on 5-HT transporters in OB-BED. Methods The 5-HT transporter binding of seven OB-BED was measured by single-photon emission computed tomography (SPECT), by using iodine-123-labelled nor-β-CIT as a tracer, before treatment and after successful treatment, when the OB-BED were asymptomatic. Treatment consisted of group psychotherapy and fluoxetine medication. The control subjects, six obese women without eating disorders, were also studied twice by using SPECT. Results The 5-HT transporter binding of the symptomatically recovered OB-BED increased significantly (24±22%) after treatment, whereas in the control group, binding remained unchanged. Conclusions The results tentatively suggest that 5-HT transporter binding in OB-BED is an adaptive mechanism, which can be affected by treatment. Furthermore, there seems to be a link between improved 5-HT transporter binding and reduced binge eating.  相似文献   
74.
PurposeIn female individuals 15–25-years of age, the AS04-containing human papillomavirus (HPV)–16/18 vaccine is highly immunogenic and provides up to 100% protection against HPV-16/18 persistent infection and associated cervical lesions up to 4.5 years. Optimal cervical cancer prevention will require prophylactic vaccination against oncogenic HPV 16 and 18 before the onset of sexual activity in early adolescent girls. To establish the feasibility of vaccination in girls 10–14 years of age, we compared the immunogenicity and safety in early adolescent female individuals to those 15–25 years in whom vaccine efficacy has been demonstrated.MethodsWe enrolled 773 female participants aged 10–14 years and 15–25 years to receive the HPV-16/18 L1 VLP AS04 vaccine, which was administered at months 0, 1, and 6. Serum samples were collected at months 0 and 7; antibodies to HPV 16 and 18 VLPs were measured by enzyme-linked immunosorbent assay. Vaccine safety was assessed at 7 or 30 days after each dose; serious adverse events were recorded during the entire study period.ResultsBoth age groups achieved 100% seroconversion for HPV 16 and 18. Participants in the group aged 10–14 years were not only noninferior to those 15–25 years in terms of HPV 16 and 18 seroconversion rates but also had approximately twice as high geometric mean titers. The vaccine was generally safe and well tolerated.ConclusionsThese findings suggest that HPV vaccination during early adolescence is generally safe, well tolerated, and highly immunogenic. The observed higher antibody titers in the group 10–14 years of age are likely to result in longer antibody persistence. Overall, these data support the implementation of prophylactic HPV vaccination in this age group.  相似文献   
75.
OBJECTIVE: To investigate the expression of inducible nitric oxide synthase (iNOS) in oropharyngeal and hypopharyngeal squamous cell carcinoma (SCC) and its relation to p53 expression, histologic differentiation, clinical data, and prognosis. STUDY DESIGN: A retrospective survey. METHODS: Primary tumors for analyses were obtained from 118 patients diagnosed with SCC of the oropharynx or hypopharynx between 1975 and 1998 in eastern Finland. Immunohistochemical analysis was used to evaluate the expression of iNOS and p53. The expression pattern of iNOS was related to p53 expression, clinical data, and survival. RESULTS: High iNOS score was associated significantly with high nuclear p53 expression index (P = .006) and positive cytoplasmic p53 expression (P = .025). The score for iNOS expression was significantly lower in the largest (T4) tumors (P = .043). No association was seen between iNOS score and N or M class, tumor stage, or histologic differentiation. The score for iNOS expression was not related to overall survival. CONCLUSIONS: The expressions of iNOS and p53 seem to be inter-related in pharyngeal SCC, although the causality remains to be clarified. The expression of iNOS shows no prognostic value in pharyngeal SCC.  相似文献   
76.
2,6-Dichlorophenyl methylsulfone (2,6-diClPh-MeSO2) is a potent olfactory toxicant reported to induce endoplasmic reticulum (ER) stress, caspase activation, and extensive cell death in mice. The aim of the present study was to examine cytochrome P450 (P450)-dependent bioactivation, nonprotein sulfhydryl (NP-SH) levels, and early ultrastructural changes in mouse olfactory mucosa following an i.p. injection of 2,6-diClPh-MeSO2 (32 mg/kg). A high covalent binding of 2,6-diClPh-14C-MeSO2 in olfactory mucosa S9 fraction was observed, and the CYP2A5/CYP2G1 substrates coumarin and dichlobenil significantly decreased the binding, whereas the CYP2E1 substrate chlorzoxazone had no effects. An increased bioactivation was detected in liver microsomes of mice pretreated with pyrazole, known to induce CYP2A4, 2A5, 2E1, and 2J, and addition of chlorzoxazone reduced this binding. 2,6-DiClPh-14C-MeSO2 showed a marked covalent binding to microsomes of recombinant yeast cells expressing mouse CYP2A5 or human CYP2A6 compared with wild type. One and 4 h after a single injection of 2,6-diClPh-MeSO2, the NP-SH levels in the olfactory mucosa were significantly reduced compared with control, whereas there was no change in the liver. Ultrastructural studies revealed that ER, mitochondria, and secretory granules in nonneuronal cells were early targets 1 h after injection. We propose that lesions induced by 2,6-diClPh-MeSO2 in the mouse olfactory mucosa were initiated by a P450-mediated bioactivation in the Bowman's glands and depletion of NP-SH levels, leading to disruption of ion homeostasis, organelle swelling, and cell death. The high expression of CYP2A5 in the olfactory mucosa is suggested to play a key role for the tissue-specific toxicity induced by 2,6-diClPh-MeSO2.  相似文献   
77.
Lymphotoxin-α (LTA) is a cytokine involved in inflammatory reactions. NFKBIL1 is a regulator of the NF-κB complex. The study investigated the associations of LTA 804 C>A and NFKBIL1-63 T>A polymorphisms with the use of statin and acetylsalicylic acid (ASA) treatment in relation to myocardial infarction (MI). The study population comprised of 600 Finnish individuals who underwent coronary angiography volunteering for the Angiography and Genes Study. Genotypes were detected by the TaqMan 5′ nuclease assay. We found a interaction between the LTA genotype (p=0.002) and the NFKBIL1 genotype (p=0.012) and statin treatment in relation to MI. Subjects with the LTA AA or the NFKBIL1 AA genotype were at a 2.77 (95% CI:1.22-6.24) and 2.85 (95% CI:1.22-6.66) times higher risk, respectively, of suffering an MI when compared to other genotypes among statin non-users. ASA treatment also modulated associations between LTA and NFKBIL1 genotypes and MI (p=0.015 and p=0.028 respectively). The NFKBIL1-A-LTA-A haplotype showed a 61% increase in the risk of MI compared to the NFKBIL1-T-LTA-C haplotype among statin non-users. Anti-inflammatory medication modifies the genotype-related risk of MI, suggesting that subjects with LTA and NFKBIL1 AA haplotype might especially benefit from the treatment.  相似文献   
78.
Objectives and Study Design: The advent of the rigid endonasal endoscope and the development of functional endoscopic sinus surgery (FESS) technique have awakened interest in an endonasal endoscopic dacryocystorhinostomy (EESC-DCR) in treating nasolacrimal obstruction. This prospective, randomized study compares EESC-DCR with traditional external dacryocystorhinostomy (EXT-DCR) for their success rates, surgical duration, and postoperative symptoms. Patients and Methods: Sixty-four cases in 60 patients with primary acquired nasolacrimal sac or duct obstruction were divided into two subgroups by symptoms (simple epiphora/ chronic dacryocystitis). These patients were randomized within both subgroups into two operation groups. Altogether 32 EESC-DCRs and 32 EXT-DCRs were performed. The final follow-up visit was at 1 year. The patency of the lacrimal passage was investigated by irrigation and patients were questioned about their symptoms. Results: The success rate at 1 year after surgery was 75% for EESC-DCR and 91% for EXT-DCR after primary surgery. The difference was not statistically significant (P = .18). The success rate after secondary surgery with a follow-up time of 1 year was 97% in both study groups. The average duration for EESC-DCR was 38 minutes, and 78 minutes for EXT-DCR, (P < .001). Conclusions: EXT-DCR, when compared with EESC-DCR, appears to give a higher, although not statistically significant, primary success rate, but the secondary success rates are equal, indicating that these two different DCR techniques are acceptable alternatives.  相似文献   
79.
Objective To evaluate the use of the pre-operative tumour-associated trypsin inhibitor (TATI) level and residual tumour size at primary surgery as a prognostic indicators for patients with Stage III epithelial ovarian cancer.
Design Retrospective cohort study.
Setting Department of Obstetrics and Gynaecology, University Hospital, Helsinki, Finland.
Participants Ninety-eight women with Stage III ovarian cancer.
Methods TATI was measured by radioimmunoassay from serum samples obtained within one week before surgery. A cutoff value of 22 μg/L was used. Multivariate analysis included pre-operative TATI level, age, histologic grade and histologic type. Mantel-Cox test was used for calculating statistical significance of differences in survival between groups.
Main outcome measures Cumulative five-year survival, pre-operative serum TATI level and residual tumour size.
Results Surgery was optimal (residual tumour size ≤ 2 cm) in 55 patients and suboptimal (residual tumour size > 2 cm) in 43. Pre-operative TATI level ≤ 22 μg/L predicted better prognosis both in patients with optimal and suboptimal surgery compared with patients with pre-operative TATI level > 22 μ/L. Patients with optimal surgery and a pre-operative TATI > 22 μg/L had a twofold relative risk of death compared with those with a pre-operative TATI ≤ 22 μg/L. The cumulative survival was less than three years for patients with suboptimal surgery and pre-operative TATI > 22 μg/L.
Conclusions Pre-operative serum TATI in combination with residual tumour size may be useful in stratifying patients with Stage III ovarian cancer into different categories in randomised treatment trials.  相似文献   
80.
Timing of onset of autoimmunity is a prerequisite for unmasking triggers and pathogenesis of type 1 diabetes. We followed 4,590 consecutive newborns with 8 or 3% HLA-DQB1 conferred risk for type 1 diabetes at 3-, 6-, or 12-month intervals up to 5.5 years of age. Islet cell autoantibodies (ICAs) and, in the 137 children with ICAs, insulin autoantibodies (IAAs), GAD65 autoantibodies (GADAs), and IA-2 protein autoantibodies (IA-2As) were measured. Children with high genetic risk developed ICAs more often than those with moderate risk (log-rank P = 0.0015); 85 and 91% remained ICA negative by 5 years of age, respectively. The time of appearance of biochemical autoantibodies was then compared with the appearance of ICAs. IAAs and GADAs emerged usually before ICAs (means -1.8 and -1.5 months, respectively) and IA-2As after ICAs (mean 2.0 months). Ninety-five percent of all IAAs, GADAs, and IA-2As seroconversions occurred in a cluster (-12 to 8 months) around the ICA seroconversion. We conclude that diabetes-associated autoantibodies emerged in children with predisposing HLA-DQB1 alleles after 3 months of age at a constant tempo, determined by the genetic risk level, usually in the order of IAA, GADA, ICA, and IA-2A. Seroconversion to multiple autoantibody positivity usually occurred tightly clustered in time.  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