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   4237篇
  免费   309篇
  国内免费   38篇
耳鼻咽喉   42篇
儿科学   76篇
妇产科学   79篇
基础医学   588篇
口腔科学   71篇
临床医学   396篇
内科学   961篇
皮肤病学   82篇
神经病学   276篇
特种医学   143篇
外科学   574篇
综合类   76篇
一般理论   2篇
预防医学   337篇
眼科学   238篇
药学   313篇
中国医学   79篇
肿瘤学   251篇
  2024年   10篇
  2023年   57篇
  2022年   136篇
  2021年   225篇
  2020年   166篇
  2019年   200篇
  2018年   243篇
  2017年   160篇
  2016年   189篇
  2015年   171篇
  2014年   204篇
  2013年   277篇
  2012年   383篇
  2011年   373篇
  2010年   230篇
  2009年   184篇
  2008年   265篇
  2007年   251篇
  2006年   196篇
  2005年   138篇
  2004年   127篇
  2003年   108篇
  2002年   67篇
  2001年   19篇
  2000年   21篇
  1999年   15篇
  1998年   15篇
  1997年   9篇
  1996年   14篇
  1995年   8篇
  1994年   6篇
  1993年   4篇
  1992年   5篇
  1991年   7篇
  1990年   8篇
  1989年   8篇
  1987年   3篇
  1985年   3篇
  1984年   6篇
  1983年   5篇
  1982年   6篇
  1981年   6篇
  1980年   6篇
  1979年   8篇
  1978年   6篇
  1977年   7篇
  1976年   5篇
  1974年   4篇
  1973年   4篇
  1971年   4篇
排序方式: 共有4584条查询结果,搜索用时 0 毫秒
971.

Background

Hepatitis D virus (HDV) is a defective virus dependent on hepatitis B virus (HBV) for its replication. Due to HDV transmission routes, patients undergoing hemodialysis and those with HIV infection are at risk of acquiring HDV.

Objectives

This study was aimed to determine the frequency and genotype of HDV infection among patients with HIV infection and those undergoing hemodialysis.

Patients and Methods

720 cases including 120 patients undergoing hemodialysis, and 600 patients with HIV infection were studied. All cases with positive results for HBsAg were evaluated for the presence of anti-HDV antibodies. Samples with Anti-HDV positive results were subjected to nested PCR for HDV-RNA confirmation, and sequenced for HDV genotype determination.

Results

HBsAg was found in 9 (7.5%) of 120 patients undergoing hemodialysis, and 9 (1.5%) of 600 patients with HIV infection. 3 (33.3%) of patients undergoing hemodialysis with positive results for HBsAg, and 5 (55.5%) of cases with HIV infection and positive results for HBsAg, had positive findings for anti-HDV which were then subjected to nested PCR. The amplification results confirmed that in 3 (37.5%) samples HDV-RNA was detected. Overall 2.5% of patients undergoing hemodialysis, and 0.8% of cases infected with HIV had positive results for anti-HDV and 1.7% and 0.2% of cases undergoing hemodialysis and patients infected with HIV had positive findings for HDV-RNA respectively. All of the HDV isolates were clustered in clade 1.

Conclusions

The survey showed that overall HDV frequency was not high in our high risk cases. Therefore, practitioners and health care managers should become aware of the risk of dual infection with HBV and HDV especially in high risk patients.  相似文献   
972.
OBJECTIVE: Juvenile rheumatoid arthritis (JRA) represents a heterogeneous group of disorders with a complex genetic component. A genome scan was performed to detect linkage to JRA in 121 families containing 247 affected children in North America (the JRA Affected Sibpair [ASP] Registry). METHODS: Genotype data collected for HLA-DR and 386 microsatellite markers were subjected to multipoint nonparametric linkage analysis. Following analysis of the entire set of families, additional analyses were performed after a priori stratification by disease onset type, age at onset, disease course, and selected HLA-DRB1 alleles. RESULTS: Linkage of JRA to the HLA region was confirmed (logarithm of odds [LOD] score 2.26). Additional evidence supporting linkage of JRA was observed at 1p36 (D1S214; LOD 1.65), 19p13 (D19S216; LOD 1.72), and 20q13 (D20S100; LOD 1.75). For early-onset polyarticular disease, evidence of linkage was found at chromosome 7q11 (D7S502; LOD 3.47). For pauciarticular disease, evidence supporting linkage was observed on chromosome 19p13 (D19S216; LOD 2.98), the same marker that supported linkage to the "JRA" phenotype. Other regions supporting linkage with JRA disease subtype included 20q13, 4q24, 12q24, and Xp11. Stratification of families based on the presence of the HLA-DR8 allele in affected siblings resulted in significant linkage observed at 2p25 (D2S162/D2S305; LOD 6.0). CONCLUSION: These data support the hypothesis that multiple genes, including at least 1 in the HLA region, influence susceptibility to JRA. These findings for JRA are consistent with findings for other autoimmune diseases and support the notion that common genetic regions contribute to an autoimmune phenotype.  相似文献   
973.
The use of low-frequency stimulation (LFS) as a therapy for epilepsy is currently being studied in experimental animals and patients with epilepsy. In the present study, the role of serine/threonine protein phosphatases in the inhibitory effects of LFS on perforant path kindling acquisition was investigated in rats. Animals were kindled by stimulation of perforant path in a stimulation using rapid kindling procedure (six stimulations per day). LFS (1 Hz) was applied immediately after termination of each kindling stimulation. FK506 (1 μM; i.c.v.), a serine/threonine protein phosphatase PP2B inhibitor and okadaic acid (1 μM; i.c.v.), a serine/threonine protein phosphatases PP1/2A inhibitor, were daily microinjected into the left ventricle 10 min before starting the stimulation protocol. Application of LFS retarded the kindling acquisition and delayed the expression of different kindled seizure stages significantly. In addition, LFS reduced the increment of daily afterdischarge duration during kindling development. Neither FK506 nor okadaic acid microinjection interfere with the antiepileptogenic effect of LFS on kindling parameters. Obtained results showed that activation of PP1/2A and PP2B, which play a critical role in LFS induced down-regulation of synaptic strength, had no role in mediating the inhibitory effects of LFS on perforant path kindling acquisition.  相似文献   
974.
This study investigated loop-mediated isothermal amplification (LAMP) detection of Plasmodium falciparum and Plasmodium vivax in urine and saliva of malaria patients. From May to November 2011, 108 febrile patients referred to health centers in Sistan and Baluchestan Province of south-eastern Iran participated in the study. Saliva, urine, and blood samples were analyzed with nested PCR and LAMP targeting the species-specific nucleotide sequence of small subunit ribosomal RNA gene (18S rRNA) of P. falciparum and P. vivax and evaluated for diagnostic accuracy by comparison to blood nested PCR assay. When nested PCR of blood is used as standard, microscopy and nested PCR of saliva and urine samples showed sensitivity of 97.2%, 89.4% and 71% and specificity of 100%, 97.3% and 100%, respectively. LAMP sensitivity of blood, saliva, and urine was 95.8%, 47% and 29%, respectively, whereas LAMP specificity of these samples was 100%. Microscopy and nested PCR of saliva and LAMP of blood were comparable to nested PCR of blood (к = 0.95, 0.83, and 0.94, respectively), but agreement for nested PCR of urine was moderate (к = 0.64) and poor to fair for saliva LAMP and urine LAMP (к = 0.38 and 0.23, respectively). LAMP assay showed low sensitivity for detection of Plasmodium DNA in human saliva and urine compared to results with blood and to nested PCR of blood, saliva, and urine. However, considering the advantages of LAMP technology and of saliva and urine sampling, further research into the method is worthwhile. LAMP protocol and precise preparation protocols need to be defined and optimized for template DNA of saliva and urine.  相似文献   
975.
The influence of carbon on the phase transformation behavior of stainless steels with the base chemical composition Fe–13Cr (wt.%), and carbon concentrations in the range of 0–0.7 wt.%, was studied at temperatures between −196 °C and liquidus temperature. Based on differential scanning calorimetry (DSC) measurements, the solidification mode changed from ferritic to ferritic–austenitic as the carbon concentration increased. The DSC results were in fair agreement with the thermodynamic equilibrium calculation results. In contrast to alloys containing nearly 0% C and 0.1% C, alloys containing 0.2–0.7% C exhibited a fully austenitic phase stability range without delta ferrite at high temperatures. Quenching to room temperature (RT) after heat treatment in the austenite range resulted in the partial transformation to martensite. Due to the decrease in the martensite start temperature, the fraction of retained austenite increased with the carbon concentration. The austenite fraction was reduced by cooling to −196 °C. The variation in hardness with carbon concentration for as-quenched steels with martensitic–austenitic microstructures indicated a maximum at intermediate carbon concentrations. Given the steady increase in the tetragonality of martensite at higher carbon concentrations, as confirmed by X-ray diffraction measurements, the variation in hardness with carbon concentration is governed by the amount and stability of austenite.  相似文献   
976.
Chimerism, a rare human disorder, is assumed to be the result of an amalgamation of two separate zygotes in a single embryo. Studies have shown that the phenotypic spectrum of chimerism is variable and there is no definite genotype–phenotype correlation in patients with chimerism, therefore a majority of cases might remain undiagnosed. This study aims to investigate the possible mechanism of the chimerism in a 46,XX/46,XY infertile and phenotypically normal male, with 46,XX blood karyotype and normal spermatogenesis. We have used Interphase‐FISH analysis to study the CEPX and CEPY regions on buccal and urine samples as well as molecular analysis of polymorphic short tandem repeats (STR) markers from 34 loci in order to discover the origin of 46,XX/46,XY. Analysis of X‐linked and autosomal STR markers on blood, buccal tissue, urine, fibroblast and testis biopsy samples of the proband along with the blood sample of the patient's parents and siblings, showed divergent karyotypes in different tissues and tetragametic chimerism was diagnosed.  相似文献   
977.
978.

Introduction

Renal cell carcinoma (RCC) brain metastasis is generally viewed as poor prognostic features and often excludes patients from cytoreductive nephrectomy or participation in clinical trials. We aim to evaluate patients presenting with brain metastasis and their outcomes.

Methods

Surveillance Epidemiology and End Results-18 registries database was queried for all patients with metastatic RCC from 2010 to 2014. Patients with renal cancer as their only malignancy were included. Information was available for metastatic disease to bone, liver, lung, and brain. Patients were then further stratified into those with isolated brain metastases and those with additional metastasis to other sites as well. Overall survival was compared between groups using logrank analysis.

Results

A total of 6,667 patients were identified with metastatic RCC. Among them, 775 (12.1%) had brain metastasis at time of diagnosis. Of these patients with brain metastasis, 152 (20.4%) had isolated brain metastasis. Only 23.8% of all patients with brain metastasis underwent cytoreductive nephrectomy, compared to 40.8% of patients with isolated brain metastasis. Patients with brain and other metastasis and brain metastasis only treated by cytoreductive nephrectomy exhibited a median survival of 11 and 33 months, respectively. Those patients who did not undergo cytoreductive nephrectomy experienced a median survival of 4 and 5 months, respectively.

Conclusion

It appears that selected patients with brain metastasis may experience durable long-term survival. This information may be beneficial for patient counseling, surgical planning, and consideration for inclusion in clinical trials.  相似文献   
979.
980.
Congenital sternal foramen is an anomaly whose occurrence is rare in human but is especially unusual in animals. This defect was formed when fusion of multiple ossification centers was incomplete. It may be associated with other lesions in body organs especially cardiac anomalies. In the present study, we report a very rare case of congenital sternal foramen in a Holstein calf. The oval defect was like a gunshot wound and located at the lower third of the sternum. Apparently, the rest of skeleton system seems normal. The awareness of the anomaly is important for better diagnosis and treatment of diseases.  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