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   605篇
  免费   21篇
  国内免费   1篇
儿科学   1篇
妇产科学   13篇
基础医学   309篇
口腔科学   2篇
临床医学   23篇
内科学   62篇
皮肤病学   6篇
神经病学   43篇
特种医学   17篇
外科学   65篇
综合类   1篇
预防医学   8篇
眼科学   14篇
药学   32篇
肿瘤学   31篇
  2023年   3篇
  2022年   11篇
  2021年   22篇
  2020年   5篇
  2019年   12篇
  2018年   9篇
  2017年   12篇
  2016年   22篇
  2015年   23篇
  2014年   15篇
  2013年   20篇
  2012年   41篇
  2011年   44篇
  2010年   16篇
  2009年   22篇
  2008年   32篇
  2007年   33篇
  2006年   32篇
  2005年   30篇
  2004年   32篇
  2003年   22篇
  2002年   19篇
  2001年   12篇
  2000年   8篇
  1999年   7篇
  1998年   12篇
  1997年   9篇
  1996年   11篇
  1995年   14篇
  1994年   23篇
  1993年   5篇
  1992年   7篇
  1991年   3篇
  1990年   4篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   6篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
排序方式: 共有627条查询结果,搜索用时 15 毫秒
71.
This article reports the first preparation of miniantibodies to Azospirillum brasilense Sp245 surface antigens by using a combinatorial phage library of sheep antibodies. The prepared phage antibodies were used for the first time for lipopolysaccharide and flagellin detection by dot assay, electro-optical analysis of cell suspensions, and transmission electron microscopy. Interaction of A. brasilense Sp245 with antilipopolysaccharide and antiflagellin phage-displayed miniantibodies caused the magnitude of the electro-optical signal to change considerably. The electro-optical results were in good agreement with the electron microscopic data. This is the first reported possibility of employing phage-displayed miniantibodies in bacterial detection aided by electro-optical analysis of cell suspensions.  相似文献   
72.
73.
Kidney cancer is a heterogeneous disease comprised of a number of histologic subtypes, each associated with unique genetic mutations, clinical features, and sensitivity to treatment. By examining families affected with the hereditary kidney cancer syndromes von Hippel-Lindau, hereditary papillary renal cell carcinoma, hereditary leiomyomatosis and renal cell carcinoma, and Birt-Hogg-Dubé, researchers have been able to identify the genes responsible for these syndromes. This work has revealed that kidney cancer is fundamentally a metabolic disorder, and as such, novel targeted therapies specific to their molecular biology have been developed and employed in both the hereditary and sporadic forms of renal cell carcinoma.  相似文献   
74.
Ewing sarcoma, also referred to as primitive neuroectodermal tumor (PNET), is a malignancy, histologically characterized by Homer-Wright rosettes and small round cells, that presents most commonly in bone or soft tissue in the pediatric and adolescent populations. We report the case of a patient that presents with intermittent gross hematuria, abdominal mass and elevated blood pressure. After surgical excision of the renal mass, the rare finding of a primary renal Ewing's sarcoma was discovered. After surgery the patient was additionally treated with chemotherapy. After presenting this case, we briefly discuss the unique case of isolated renal Ewing's sarcoma, including incidence and treatment.  相似文献   
75.
The Chernobyl accident (April 26, 1986) exposed a large part of the Belarus population to ionizing radiation. We analyzed the time trends of Down syndrome (DS) in Belarus to evaluate whether either brief exposure at high dose rates during the plume passage or continuous exposure at low doses and dose rates of the residents of contaminated areas had any detectable impact on DS prevalence at birth. DS data came from the Belarus National Registry of Congenital Malformations (1981–2001). We observed a significant peak of DS in January 1987 (26 cases observed and 9.84 expected; observed/expected ratio = 2.64; 95% CI = 1.72–3.76), but found no positive long-term time trends in contaminated or control areas. The time occurrence of the January peak, high dose rates during the plume passage and experimental data showing a radiosensitive phase of oogenesis around conception time in mammals suggest that the January peak may be linked to the Chernobyl plume.  相似文献   
76.
The aim of the present study was to assess the ability of a novel bone imaging technique to diagnose accurately the cause for back pain as an isolated and presenting complaint in adolescents. An integrated 18F-fluoride positron-emission tomography-computed tomography (PET-CT) study was performed at the same setting without changing the patients' position, followed by generation of fused images of functional and anatomical data. Fifteen subjects were included in the study. The interpretation of PET-CT fused images was based on increased 18F-fluoride uptake and the corresponding CT-located abnormality. Ten patients had positive findings that included 4 cases of spondylolysis (3 of them active), 3 frank fractures (2 of the transverse process and 1 of the facet), 2 osteoid osteomas, 1 osteitis pubis, 1 sacroiliitis, and 2 herniated disks. Three patients presented 2 coexisting pathologies. Treatment was tailored based on final diagnosis. In 5 patients, in whom no abnormality was identified, the back pain resolved spontaneously. The 18F-fluoride PET-CT can detect spinal lesions with high diagnostic accuracy in adolescents with back pain. Considering the associated costs and radiation exposure, it should be used at present only in cases of long-standing and disabling back pain in which other imaging modalities were inconclusive.  相似文献   
77.
Summary: The number of active centers (CP) and propagation rate constants (kP) for polymerization of ethylene with supported catalysts LFeCl2/SiO2, LFeCl2/Al2O3 and LFeCl2/MgCl2 (L = 2,6‐(2,6‐(Me)2C6H3NCMe)2C5H3N), activated by an Al(i‐Bu)3 co‐catalyst, were determined by a method of polymerization inhibition with radioactive 14CO. In contrast to homogeneous systems based on LFeCl2, the supported catalysts are highly active and stable in ethylene polymerization at 70–80 °C. In the presence of hydrogen, the activity of the supported catalysts substantially increases (2–4 fold). The data obtained on the effect of hydrogen on the calculated CP and kP values suggests that for ethylene polymerization without hydrogen, the “dormant” active centers are formed in the catalytic systems. A scheme for the formation of these “dormant” centers and their reactivation in presence of hydrogen is suggested. For the investigated supported catalysts the CP values were found to be only 2 to 4% of the total iron complex content in the catalysts. The kP value for the catalysts prepared using different supports (SiO2, Al2O3 and MgCl2) were close (3.2 × 104 to 4.5 × 104 L · (mol · s)−1 at 70 °C). The support composition affects neither the molecular mass (MM) nor the molecular mass distribution (MMD) of the polymers produced. The obtained CP and kP values and data on the polymer MM and MMD lead to conclusion that the nature of the support has almost no effect on the structure of the active centers and the distribution of their reactivity.

Effect of support on the MMD of PE produced over supported LFeCl2 catalysts.  相似文献   

78.
We describe a rare combination of multiple multiple branch retinal arteriolar occlusions (BRAO) and encephalopathy, which developed in an adult male 10 days after smallpox vaccination. A 53-year-old physician presented with sudden temporal visual field loss in the left eye. Ten days earlier he had received a smallpox vaccination. Hyperbaric oxygen was administered because of suspected BRAO. Examination on day 3 revealed a decrease in visual acuity and loss of visual field. Fundoscopy of the left eye disclosed a retinal infarct in the inferior macula and multiple cotton wool spots over the entire posterior pole. Fluorescein angiography showed delayed arterial filling and multiple non-perfused areas. Magnetic resonance imaging of the brain disclosed white matter focal lesions. Neurological examination was normal. Audiological examination revealed mild hearing loss caused by an old phonic trauma. A combination of intravenous methylprednisolone and immunoglobulins, recommended for the treatment of Susac syndrome, was administered. At the follow-up visit 3 months later, visual acuity in the left eye improved, fundoscopy showed resolution of the cotton wool spots and temporal disc pallor, and the visual field was substantially restored.  相似文献   
79.
The role of energy deregulation and altered/adapted metabolism in tumor cells is an increasingly important issue in understanding cancer. Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an aggressive form of RCC characterized by germline mutation of fumarate hydratase (FH), followed by somatic loss of the remaining wild-type allele and known to be a highly metastatic and lethal malignancy compared to other RCCs. The intrinsic loss of normal tricarboxylic acid (TCA) cycle presumably aids tumorigenesis due to the necessary metabolic alterations required and the enforced dependence on glycolysis derived energy, mimicking the Warburg effect. Thus, there is considerable utility in establishing a preclinical cell model from these tumors to study energy metabolism deregulation, as well as developing new targeted therapeutic approaches for TCA cycle enzyme-deficient cancers. Here, we describe a new immortalized cell line, UOK268, derived from a patient's primary HLRCC-associated kidney cancer. This represents the first primary renal cell line to model TCA cycle gene loss and provides a perfect partner cell line to our previously described metastasis-derived HLRCC-associated cell line, UOK262. We identified a novel germline FH missense mutation, p.His192Asp, and the subsequent loss of heterozygosity in UOK268. The UOK268 cell line expressed mutant FH protein, which localized to the mitochondria, but with loss of almost all catalytic activity. The UOK268 cells had severely compromised oxidative phosphorylation and increased glycolytic flux. Ingenuity pathways analysis of human mitochondria-focused cDNA microarray (hMitChip3) gene chip data confirmed the altered mRNA expression patterns of genes involved in several important pathways, such as lipid metabolism, apoptosis, and energy production/glycolysis. UOK268 provides a unique model of a primary cell line demonstrating an enforced, irreversible Warburg effect and, combined with UOK262, provides a unique in?vitro preclinical model for studying the bioenergetics of the Warburg effect in human cancer.  相似文献   
80.

Purpose

[18F]Fluciclatide is an integrin-targeted PET radiopharmaceutical. αvβ3 and αvβ5 are upregulated in tumor angiogenesis as well as on some tumor cell surfaces. Our aim was to use [18F]fluciclatide (formerly known as [18F]AH111585) for PET imaging of angiogenesis in melanoma and renal tumors and compare with tumor integrin expression.

Methods

Eighteen evaluable patients with solid tumors ≥2.0 cm underwent [18F]fluciclatide PET/CT. All patients underwent surgery and tumor tissue samples were obtained. Immunohistochemical (IHC) staining with mouse monoclonal antibodies and diaminobenzidine (DAB) was applied to snap-frozen tumor specimens, and additional IHC was done on formalin-fixed paraffin-embedded samples. DAB optical density (OD) data from digitized whole-tissue sections were compared with PET SUV80% max, and Patlak influx rate constant (K i) data, tumor by tumor.

Results

Tumors from all 18 patients demonstrated measurable [18F]fluciclatide uptake. At the final dynamic time-point (55 min after injection), renal malignancies (in 11 patients) demonstrated an average SUV80% max of 6.4?±?2.0 (range 3.8 – 10.0), while the average SUV80% max for metastatic melanoma lesions (in 6 patients) was 3.0?±?2.0 (range 0.7 – 6.5). There was a statistically significant difference in [18F]fluciclatide uptake between chromophobe and nonchromophobe renal cell carcinoma (RCCs, with SUV80% max of 8.2?±?1.8 and 5.4?±?1.4 (P?=?0.020) and tumor-to-normal kidney (T/N) ratios of 1.5?±?0.4 and 0.9?±?0.2, respectively (P?=?0.029). The highest Pearson's correlation coefficients were obtained when comparing Patlak K i and αvβ5 OD when segregating the patient population between melanoma and RCC (r?=?0.83 for K i vs. melanoma and r?=?0.91 for K i vs. RCC). SUV80% max showed a moderate correlation with αvβ5 and αvβ3 OD.

Conclusion

[18F]Fluciclatide PET imaging was well tolerated and demonstrated favorable characteristics for imaging αvβ3 and αvβ5 expression in melanoma and RCC. Higher uptake was observed in chromophobe than in nonchromophobe RCC. [18F]Fluciclatide may be a useful radiotracer to improve knowledge of integrin expression.  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