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   624篇
  免费   29篇
  国内免费   3篇
耳鼻咽喉   12篇
儿科学   12篇
妇产科学   9篇
基础医学   97篇
口腔科学   15篇
临床医学   49篇
内科学   107篇
皮肤病学   28篇
神经病学   36篇
特种医学   26篇
外科学   79篇
预防医学   85篇
眼科学   16篇
药学   11篇
中国医学   1篇
肿瘤学   73篇
  2024年   1篇
  2023年   4篇
  2022年   23篇
  2021年   16篇
  2020年   8篇
  2019年   18篇
  2018年   13篇
  2017年   15篇
  2016年   14篇
  2015年   6篇
  2014年   26篇
  2013年   26篇
  2012年   52篇
  2011年   47篇
  2010年   27篇
  2009年   30篇
  2008年   43篇
  2007年   37篇
  2006年   58篇
  2005年   34篇
  2004年   28篇
  2003年   23篇
  2002年   26篇
  2001年   10篇
  2000年   9篇
  1999年   6篇
  1998年   3篇
  1997年   5篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1993年   2篇
  1992年   3篇
  1991年   5篇
  1990年   5篇
  1989年   2篇
  1988年   5篇
  1987年   6篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1979年   2篇
  1978年   1篇
  1973年   2篇
  1972年   1篇
  1971年   1篇
排序方式: 共有656条查询结果,搜索用时 31 毫秒
1.
The authors report a rare case of regional portal hypertension secondary to splenic vein obstruction by left adrenal carcinoma metastasis. They review the principal literature data concerning regional portal hypertension and adrenal cortical carcinoma.  相似文献   
2.
3.
Duchenne and Becker muscular dystrophy (DMD and BMD) are X-linked diseases resulting from a defect in the dystrophin gene located on Xp21. DMD is the most frequent neuromuscular disease in humans (1/3500 male newborn). Deletions in the dystrophin gene represent 65% of mutations in DMD/BMD patients. We have analyzed DNA from 72 Moroccan patients with DMD/BMD using the multiplex polymerase chain reaction (PCR) to screen for exon deletions within the dystrophin gene, and to estimate the frequency of these abnormalities. We found dystrophin gene deletions in 37 cases. Therefore the frequency in Moroccan DMD/BMD patients is about 51.3%. All deletions were clustered in the two known hot-spots regions, and in 81% of cases deletions were detected in the region from exon 43 to exon 52. These findings are comparable to those reported in other studies. It is important to note that in our population, we can first search for deletions of DMD gene in the most frequently deleted exons determined by this study. This may facilitate the molecular diagnosis of DMD and BMD in our country.  相似文献   
4.
Porphyromonas gingivalis, the major etiologic agent of chronic periodontitis, produces a broad spectrum of virulence factors, including outer membrane vesicles. In this study, we investigated the capacity of P. gingivalis vesicles to promote the shedding or cleavage of the lipopolysaccharide (LPS) receptor CD14 from the surface of human U937 macrophage-like cells. SDS-PAGE/Western immunoblotting analysis of gingival crevicular fluid samples from patients affected by moderate or advanced periodontitis revealed the presence of soluble CD14 and CD14 fragments, thus supporting the hypothesis of an in vivo shedding and cleavage of CD14 receptors. Flow cytometry analysis of macrophage-like cells treated with a vesicle-containing culture supernatant of P. gingivalis showed a significant decrease in the binding of anti-human CD14 to the cell surface. However, no accumulation of soluble CD14 or immunoreactive CD14 fragments in the assay supernatant could be demonstrated by ELISA. Treatment of macrophage-like cells with various concentrations of P. gingivalis vesicles substantially suppressed TNF-alpha production triggered by Escherichia coli LPS. This suppressive effect was much less important using heat-treated vesicles or in the presence of leupeptin, a gingipain inhibitor, during the treatment. Recombinant human CD14 receptors were found to be susceptible to proteolytic degradation by P. gingivalis vesicles. A purified Arg-gingipain preparation produced much more degradation than a Lys-gingipain preparation. This study provides evidence that P. gingivalis outer membrane vesicles contribute to the loss of membrane-bound CD14 receptors and that gingipains degrade this LPS receptor. Such a phenomenon, which results in an hyporesponsiveness of macrophages to LPS stimulation, may contribute to an increased capacity of P. gingivalis, and other periodontopathogens, to evade the host immune system mechanisms.  相似文献   
5.
The majority of intracranial teratoma are localized in pineal and sellar regions. In cerebellum, the teratoma is quite rare, the association with medulloblastoma is exceptional and was differentiated from medullomyoblastoma. We report one case of 5 years old boy with intracranial hypertension for 3 months. The cerebral computed tomography showed a tumor in the fourth ventricle. The histologic study of surgical specimens found a proliferation of component of medulloblastoma adjacent to mature teratoma with smooth and striated muscles, chondroid component, adipose tissue and epithelial elements. Our objective is to discuss the diagnosis, the hitogenesis and the prognosis of this tumor.  相似文献   
6.
BackgroundIschemia-driven islet isolation procedure is one of the limiting causes of pancreatic islet transplantation. Ischemia-reperfusion process is associated with endothelium dysfunction and the release of pro-senescent microvesicles. We investigated whether pro-senescent endothelial microvesicles prompt islet senescence and dysfunction in vitro.Material and methodsPancreatic islets were isolated from male young rats. Replicative endothelial senescence was induced by serial passaging of primary porcine coronary artery endothelial cells, and microvesicles were isolated either from young passage 1 (P1) or senescent passage 3 (P3) endothelial cells. Islet viability was assessed by fluorescence microscopy, apoptosis by flow cytometry, and Western blot. Function was assessed by insulin secretion and islet senescence markers p53, p21, and p16 by Western blot. Microvesicles were stained by the PKH26 lipid fluorescent probe and their islet integration assessed by microscopy and flow cytometry.ResultsRegardless of the passage, half microvesicles were integrated in target islets after 24 hours incubation. Insulin secretion significantly decreased after treatment by senescent microvesicles (P3: 1.7 ± 0.2 vs untreated islet: 2.7 ± 0.2, P < .05) without altering the islet viability (89.47% ± 1.69 vs 93.15% ± 0.97) and with no significant apoptosis. Senescent microvesicles significantly doubled the expression of p53, p21, and p16 (P < .05), whereas young microvesicles had no significant effect.ConclusionPro-senescent endothelial microvesicles specifically accelerate the senescence of islets and alter their function. These data suggest that islet isolation contributes to endothelial driven islet senescence.  相似文献   
7.
BACKGROUND: We report a case of non-Hodgkin's malignant lymphoma of the cervicofacial region revealed by unilateral exophthalmos and blindness, an unusual mode of expression. CASE REPORT: A 40-year-old man with a 4-month history of diabetes mellitus had suffered from exophthalmos and blindness of the right eye for 20 years. Physical examination showed a homolateral hemifacial tumefaction and ophthalmoplegia. The right ocular fundus showed papillar edema and non-proliferative diabetic retinopathy. The left eye was normal. The otolaryngology explorations revealed a voluminous tumor in the anterior nasal cavity and in the cavum. Two biopsies were performed. Histology reported non-Hodgkin's T-cell lymphoma. Orbitocerebral and cervicofacial computed tomography visualized the aggressive ethmoidomaxillary extension with intraorbital and intracranial involvement. Chemotherapy (CHOP) combined with radiotherapy led to tumor regression and involution of the exophthalmos. Diagnostic difficulties, management and prognosis are discussed.  相似文献   
8.
Donor–acceptor (D–A) small molecules are regarded as promising hole-transporting materials for perovskite solar cells (PSCs) due to their tunable optoelectronic properties. This paper reports the design, synthesis and characterization of three novel isomeric D-π-A small molecules PY1, PY2 and PY3. The chemical structures of the molecules consist of a pyrazolo[1,5-a]pyrimidine acceptor core functionalized with one 3,6-bis(4,4′-dimethoxydiphenylamino)carbazole (3,6-CzDMPA) donor moiety via a phenyl π-spacer at the 3, 5 and 7 positions, respectively. The isolated compounds possess suitable energy levels, sufficient thermal stability (Td > 400 °C), molecular glass behavior with Tg values in the range of 127–136 °C slightly higher than that of the reference material Spiro-OMeTAD (126 °C) and acceptable hydrophobicity. Undoped PY1 demonstrates the highest hole mobility (3 × 10−6 cm2 V−1 s−1) compared to PY2 and PY3 (1.3 × 10−6 cm2 V−1 s−1). The whole isomers were incorporated as doped HTMs in planar n-i-p PSCs based on double cation perovskite FA0.85Cs0.15Pb(I0.85Br0.15)3. The non-optimized device fabricated using PY1 exhibited a power conversion efficiency (PCE) of 12.41%, similar to that obtained using the reference, Spiro-OMeTAD, which demonstrated a maximum PCE of 12.58% under the same conditions. The PY2 and PY3 materials demonstrated slightly lower performance in device configuration, with relatively moderate PCEs of 10.21% and 10.82%, respectively, and slight hysteresis behavior (−0.01 and 0.02). The preliminary stability testing of PSCs is also described. The PY1-based device exhibited better stability than the device using Spiro-OMeTAD, which could be related to its slightly superior hydrophobic character preventing water diffusion into the perovskite layer.  相似文献   
9.
This paper reports a case of testicular synovial sarcoma with molecular genetic analysis.A 24-year-old male presented with painless scrotal mass.Ultrasonography showed a heterogeneous mass of 66 mm×34 mm in size involving the inguinal region.Histological examination of a surgical biopsy showed a gradeⅢmonophasic growth pattern of spindle cell proliferation.Immunohistochemical analyses indicated positive staining for pancytokeratine and epithelial membrane antigen.Cytogenetic analysis showed the presence of CYT-SSX1 mutation,and CT scan showed non-specific pleural micro-nodules with a size of 7.5 mm.The patient had an extended left orchidectomy but was lost to follow-up for 1 year.A local recurrent scrotal mass of 32 mm×25 mm,multiple inguinal lymph nodes,and increased pleural nodules,which were confirmed by histological examination,were treated with three cycles of adriamycine and ifosfamide chemotherapy,surgical resection,and radiotherapy with complete response.After 3 months,the patient developed local recurrence and pulmonary metastases that did not respond to second-line chemotherapy based on gemcitabine and paclitaxel.The patient had dyspnea at the time of this writing and chest pain,and is under third-line chemotherapy based on Deticene after 30 months of following up.This patient died on November 16,2012 after a resperatory failure and malignant plural effusion. Synovial sarcoma should be considered in the differential diagnosis of soft tissue tumor and it should be aggressively treated to improve prognosis.Although our patient has shown numerous factors of bad prognosis,he has had a relatively long survival time.  相似文献   
10.
1. Laboratory experiments were carried out to assess uptake and metabolism of the epilepsy drug, carbamazepine and its consequent biological responses in marine clam (Ruditapes decussatus) a model non-target organism in ecotoxicology.

2. Clams were exposed to two nominal concentrations (C1?=?30?μg/L and C2?=?50?μg/L) of CBZ for a maximum period of 14 days. Analysis of CBZ and their metabolites in clam and water after exposure to two nominal concentrations of the pharmaceutical drug were performed using UPLC-HRMS analysis. CBZ accumulation reached an average tissue concentration of 1241.59 ng/g dw and 1664.33 ng/g dw at low and high nominal concentration, respectively.

3. Furthermore, a metabolite (3-hydroxy-CBZ) was detected in tissues indicating carbamazepine translocation and metabolism inside clam, suspect screening of CBZ glucuronides was also performed by accurate mass extraction but it could not be detected.

4. Activities of antioxidant enzymes superoxide dismutase, catalase and gluthatione-S-transferase generally increased. Change in the contents of glutathione, malondialdehyde and protein carbonyl were also studied.

5. Results indicated that the bioaccumulation of CBZ resulted in the changes of the antioxidant defense system and the production of ROS with the oxidative stress, ultimately induced alteration in lipid peroxidation and protein carbonyl.  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