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   1612篇
  免费   132篇
  国内免费   11篇
耳鼻咽喉   7篇
儿科学   34篇
妇产科学   64篇
基础医学   233篇
口腔科学   40篇
临床医学   170篇
内科学   323篇
皮肤病学   36篇
神经病学   121篇
特种医学   40篇
外科学   256篇
综合类   36篇
预防医学   125篇
眼科学   60篇
药学   118篇
中国医学   21篇
肿瘤学   71篇
  2024年   5篇
  2023年   43篇
  2022年   67篇
  2021年   83篇
  2020年   64篇
  2019年   82篇
  2018年   107篇
  2017年   75篇
  2016年   75篇
  2015年   72篇
  2014年   89篇
  2013年   107篇
  2012年   149篇
  2011年   155篇
  2010年   94篇
  2009年   62篇
  2008年   76篇
  2007年   78篇
  2006年   70篇
  2005年   46篇
  2004年   37篇
  2003年   22篇
  2002年   15篇
  2001年   11篇
  2000年   4篇
  1999年   16篇
  1998年   4篇
  1997年   4篇
  1996年   4篇
  1995年   1篇
  1994年   1篇
  1992年   5篇
  1991年   4篇
  1990年   6篇
  1989年   3篇
  1988年   3篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1979年   1篇
  1978年   2篇
  1971年   1篇
  1969年   1篇
  1968年   1篇
  1963年   1篇
排序方式: 共有1755条查询结果,搜索用时 15 毫秒
61.
Background: Cytomegalovirus (CMV) reinfection in transplant patients has been associated with graft loss and decreased patient survival. In this regard, the HLA-G molecule has the immunomodulatory characteristic and its soluble isoforms have important roles in immunity to viruses. The 14bp insertion/deletion polymorphism impacts HLA-G mRNA stability. Regarding the HLA-E molecule, two nonsynonymous alleles, HLA-E*0101, and HLA-E*0103 are different in their functions including the affinity of the relative peptide. Objective: To explore the possible link between HLA-G and HLA-E polymorphisms with CMV reinfection among liver transplant recipients (LTRs). Methods: In this study, a total of 140 liver transplantations were performed; of which 70 CMV-reactivated LTRs and 70 CMV non-reactivated ones were recruited. The cut-off value of CMV DNA was determined to be 100 copies/mL. PCR evaluated different genotypes for HLA-G and ARMS-PCR for HLA-E*0101 and *0103. Results: Neither the HLA-G genotypes (-14 bp/-14bp and +14bp/+14 bp homozygous genotypes with the p-values: 0.43, and 0.13, respectively +14 bp⁄-14 bp heterozygous genotype with p-value: 0.49) nor the HLA-E genotypes (HLA-E*0101/0103, HLA-E*0101/0101, and HLA-E*0103/0103 with the p-values: 0.152, 0.249, and 0.391, respectively) had any association with CMV reinfection in the LTRs. Conclusion: No difference was observed in the HLA-E and HLA-G genotype frequencies between our studied groups. Further studies are needed to explore other genetic variations and evaluate soluble HLA-G and HLA-E levels in the transplant population.  相似文献   
62.
63.

Background

Dendritic cells (DC) are localized in close proximity to cancer cells in many well-known tumors, and thus maybe a useful target for tumor margin assessment.

Materials and methods

[99mTc]- cyanine 7 (Cy7)-tilmanocept was synthesized and in vitro binding assays to bone marrow-derived DC were performed. Fifteen mice, implanted with either 4T1 mouse mammary or K1735 mouse melanoma tumors, were administered 1.0 nmol of [99mTc]-Cy7-tilmanocept via tail vein injection. After fluorescence imaging 1 or 2 h after injection, the tumor, muscle, and blood were assayed for radioactivity to calculate percent-injected dose. Digital images of the tumors after immunohistochemical staining for DC were analyzed to determine DC density.

Results

In vitro binding demonstrated subnanomolar affinity of [99mTc]-Cy7-tilmanocept to DC (KA = 0.31 ± 0.11 nM). After administration of [99mTc]-Cy7-tilmanocept, fluorescence imaging showed a 5.5-fold increase in tumor signal as compared with preinjection images and a 3.3-fold difference in fluorescence activity when comparing the tumor with the surgical bed after tumor excision. Immunohistochemical staining analysis demonstrated that DC density positively correlated with tumor percent of injected dose per gram (r = 0.672, P = 0.03), and higher DC density was observed at the periphery versus center of the tumor (186 ± 54 K versus 64 ± 16 K arbitrary units, P = 0.001).

Conclusions

[99mTc]-Cy7-tilmanocept exhibits in vitro and in vivo tumor-specific binding to DC and maybe useful as a tumor margin targeting agent.  相似文献   
64.
The aim of the present study was to determine zinc (Zn), chromium (Cr), cadmium (Cd) and lead (Pb) content of benthic fauna in the southeast coast of the Caspian Sea, where the major fish restocking programs are conducted. Seasonal sampling was performed in three sampling sites: north Miankaleh (NM), south Miankaleh (SM) and Gharesoo coast (GC). Results showed that sampling sites, sampling seasons and sampling sites × sampling seasons interaction had a significant effect on the heavy metal levels (p < 0.05). The yearly heavy metal concentration order was as follows: Zn > Pb > Cd > Cr. Yearly Pb levels of the NM site were significantly higher than the other sites. Also, yearly Cr levels of the SM site were significantly higher than site GC. Comparison of the benthos heavy metal levels with the available reference values suggests that the benthos tissues might be highly polluted which can intoxicate the fish feeding on them.  相似文献   
65.
Objective. To quantify the adverse influence of depression and anxiety assessed at the time of myocardial infarction, on the quality of life 5 years after the infarction. Methods. The Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI) were completed in a group of 196 patients admitted in the hospital following non-fatal myocardial infarction, and the SF-12 quality of life questionnaire was administered during the 5- year follow-up. Results. Regression analysis showed a strong association between baseline depression and QoL in both the physical and mental domains; the higher the depression scores, the poorer the QoL. However, anxiety present at the time of myocardial infarction did not predict later QoL. Conclusions. Depression but not anxiety following MI predicts longer-term quality of life in myocardial infarction survivors.  相似文献   
66.
Abstract

Design of an MR-compatible and computer-controlled odour stimuli system is essential in the studies of human olfactory function. Olfactometers are used to deliver odours to the subjects in an objective manner. We present a portable, computer-controlled eight channels olfactometer able to stimulate olfaction by employing liquid odorant stimuli. We used a high-pressure pump to generate medical grade airflow. After passing through solenoid valve-controlled odour reservoirs, odorant stimulus is conveyed to the nasal mask. The odour delivery delay of the device was measured using photo-ionisation detectors. To assess the application of the designed olfactometer, an fMRI experiment was done with 9 healthy subjects. Two odour stimuli (Vanillin and Rose) were presented to each subject in an alternating block design task of odour and non-odour conditions. The response time of each subject was gathered using the response box. Group analysis revealed a significant BOLD signal change in some regions of olfactory and trigeminal networks including the orbitofrontal cortex, insula, inferior frontal gyrus, hippocampus, cingulate gyrus and piriform cortex. The odour delivery delay measured by photo-ionisation detector was 190?ms, and the subjects’ response showed 205?ms for the Vanillin and 243?ms for the Rose odour stimuli. Our portable MR-compatible olfactometer as a stimulation device is capable of creating adequate stimulation suitable for olfactory fMRI experiments.  相似文献   
67.
Background and ObjectiveChronic inflammation is the typical sign of gastritis that may shift into gastric cancer. IL-17A and IL-17F as a novel inflammatory cytokines subset of CD4+Th play the main role in inflammation. A key cytokine receptor in the inflammatory IL-17/IL-23 axis, the interleukin 23 receptor (IL23R), may be related to gastritis. We evaluated the correspondence between IL-17A G197A, IL-17F A7488G and IL23R+2199 A/C polymorphisms with TGF-β1, IL-6, IL-17, IL-21 and IL-23 mucosal mRNAs expression in uninfected H. Pylori (HP) chronic gastritis patients.Materials and MethodsTotal RNA and genomic DNA were separated from gastric biopsies of 44 patients with gastritis. Subsequently, mucosal mRNAs expression of TGF-β1, IL-6, IL-17, IL-21 and IL-23 were assessed by real-time PCR. To polymorphisms determination of IL-17A G197A, IL-17F A7488G and IL-23R +2199A/C the PCR-RFLP was used in gastric biopsies.ResultsResults point that IL-17A G197A, IL-17F A7488G and IL23R +2199A/C polymorphisms did not influence the mucosal expression of TGF-β1, IL-6, IL-17 and IL-21 (p> 0.05). In an opposite result, we don''t find a correspondence between IL-17A G197A, IL-17F A7488G polymorphisms and mucosal expression of IL-23 (p> 0.05). In a contrary, we found a correlation between IL23R +2199A/C polymorphism and mucosal expression of IL-23 in patients with chronic gastritis (p< 0.05).ConclusionThese findings propose that IL23R +2199A/C polymorphism may change the mucosal expression of IL-23 pattern in patients with gastritis disease in the absence of HP, but to support the conclusion, more research may be required.  相似文献   
68.
69.
Rapid and effective diagnosis of brucellosis is a challenge for clinicians. Even when diagnosis is on time and therapy is initiated, meticulous follow-up appointments are crucial for ensuring the efficacy of the treatment. Due to shortcomings of serological methods, molecular diagnosis, especially real-time PCR, is becoming a main approach in laboratory diagnostics. Thus, the development of efficient procedures and standardization of the PCR tests will have a great impact on the precise detection and quantification of bacterial DNA loads, which is valuable for the medical management of brucellosis patients. We developed a new TaqMan real-time PCR directed to bcsp31, a shared gene of the brucellae. The bcsp31 gene fragment was cloned into pJET1.2. Recombinant pJET1.2-bcsp31 was linearized by HindIII digestion, and the product was used for the preparation of a standard curve. A panel of Brucella spp. and non-Brucella pathogens was tested. No bacterial genomes other than those of the brucellae were detected. According to the results, specificity of the method was 100%. In a clinical assessment, the positive-control group comprised 37 patients with microbiologically confirmed brucellosis, and 25 healthy individuals served as the negative-control group. By the end of the treatment period, there was a significant decrease in the DNA load of the 37 brucellosis patients, which persisted for the 4 weeks of monitoring after treatment, suggesting that our proposed method is an efficient monitoring tool. Serum samples prior to any treatment were collected from the 25 serologically suspicious patients and assessed by our method; 72% of these patients tested positive for brucellosis.  相似文献   
70.
In this study, the histamine concentration in the muscle tissue of whole rainbow trout (Oncorhynchus mykiss) was monitored during ice storage for a period of 18 days (0, 3, 6, 9, 12, 15 and 18th day). Results showed that the concentration of histamine increased linearly (P?<?0.05) during ice storage (except the 18th day). Histamine was not detected at the first and third day of storage. The first detection of histamine was in the sixth storage day. Initial concentration of histamine was 1.09 μg/g and finally reached to 4.30 μg/g. The maximum histamine levels was reported to be below the Australian Food Standards Code (2001) safe level (200 mg/kg), and histamine levels were low even after 18 days of storage and remained below the Food and Drug Administration (2001) tolerance level during ice storage. It seems that the levels of histamine could be a suitable freshness indicator of rainbow trout during ice storage.  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