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   936篇
  免费   28篇
  国内免费   10篇
耳鼻咽喉   36篇
儿科学   16篇
妇产科学   8篇
基础医学   178篇
口腔科学   8篇
临床医学   39篇
内科学   111篇
皮肤病学   6篇
神经病学   105篇
特种医学   75篇
外科学   147篇
综合类   2篇
预防医学   13篇
眼科学   2篇
药学   35篇
肿瘤学   193篇
  2022年   5篇
  2021年   5篇
  2018年   4篇
  2017年   9篇
  2016年   7篇
  2015年   9篇
  2014年   14篇
  2013年   24篇
  2012年   30篇
  2011年   33篇
  2010年   32篇
  2009年   23篇
  2008年   35篇
  2007年   46篇
  2006年   28篇
  2005年   37篇
  2004年   27篇
  2003年   47篇
  2002年   51篇
  2001年   46篇
  2000年   37篇
  1999年   47篇
  1998年   25篇
  1997年   22篇
  1996年   22篇
  1995年   23篇
  1994年   14篇
  1993年   12篇
  1992年   27篇
  1991年   23篇
  1990年   21篇
  1989年   29篇
  1988年   29篇
  1987年   33篇
  1986年   26篇
  1985年   21篇
  1984年   7篇
  1983年   10篇
  1982年   7篇
  1981年   5篇
  1980年   1篇
  1979年   1篇
  1978年   6篇
  1977年   2篇
  1976年   3篇
  1975年   2篇
  1973年   2篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
排序方式: 共有974条查询结果,搜索用时 15 毫秒
1.
Epidermal growth factor receptor plays an important role in the pathogenesis of many malignancies. Various growth factors, including epidermal growth factor receptor, have been shown to influence pituitary tumor growth and differentiation. To analyze the role of epidermal growth factor receptor in pituitary tumor development, we examined normal pituitaries (n=8), pituitary adenomas (n=158), and pituitary carcinomas (n=7) for expression of epidermal growth factor receptor protein and messenger RNA using tissue microarrays and RT-PCR. We also examined (a) the expression of phospho-epidermal growth factor receptor, the activated form of epidermal growth factor receptor, in pituitary tumors and normal pituitaries by immunohistochemistry and (b) the effects on epidermal growth factor receptor expression of treating pituitary cells (HP75 cell line) with epidermal growth factor. Epidermal growth factor receptor and the phosphorylated variant expression were present in normal pituitary cells. Epidermal growth factor receptor messenger RNA was also detected in normal pituitaries, pituitary adenomas, and carcinomas by in situ hybridization and RT-PCR. Most pituitary adenomas showed expression of epidermal growth factor receptor and the phosphorylated variant. Nonfunctional adenomas showed higher levels of expression of epidermal growth factor receptor (76 vs 34%) and of phospho-epidermal growth factor receptor (26 vs 8%) as compared to functional adenomas. Five of seven pituitary carcinomas showed strong expression of both epidermal growth factor receptor and phospho-epidermal growth factor receptor. When a human pituitary cell line (HP75) was cultured in the presence of epidermal growth factor receptor, there was an increase in the levels of both epidermal growth factor receptor and phospho-epidermal growth factor receptor after 5 h of treatment, thus confirming that epidermal growth factor receptor signaling was active in pituitary tumors. These results indicate that activated epidermal growth factor receptor is expressed in pituitary adenomas and carcinomas. Higher levels in pituitary carcinomas suggest a role in pituitary tumor progression.  相似文献   
2.
3.
PURPOSETo describe the spectrum of MR and CT findings in clinically symptomatic pineal cysts and to determine whether there are certain diagnostic imaging features that allow one to distinguish a benign pineal cyst from other neoplasms of the pineal region.METHODSMR and CT scans of 19 patients with clinically symptomatic pineal cysts were retrospectively reviewed. Age range was 15 to 46 years with a mean age of 28 years. There were five male and 14 female patients.RESULTSPresenting features included headache (15 patients), diplopia (four), nausea and vomiting (four), papilledema (four), seizure (three), Parinaud syndrome (two), ataxia (one), and hemiparesis (one). All cysts were resected or biopsied to provide histopathologic confirmation of the diagnosis. Preoperative diagnoses included pineal neoplasm (14 of 19), pineal cyst (3 of 19), and dermoid cyst (2 of 19). The lesions ranged from 0.8 to 3.0 cm, with a mean diameter of 1.6 cm. Three cysts showed fluid/fluid levels consistent with hemorrhage. Slightly less than half (9 of 19) had evidence of hydrocephalus. The MR signal changes were variable but typically demonstrated low signal on T1-weighted images and high signal on T2-weighted images. More than half (7 of 12) demonstrated enhancement with gadolinium. Calcification of the cyst wall was observed in only four of nine patients who had CT studies but identified histologically in all cases.CONCLUSIONThe MR appearance of benign pineal cysts is variable, ranging from that of an uncomplicated cystic mass to a mass associated with hemorrhage, enhancement, or hydrocephalus. This variability may make them indistinguishable from other pineal-region tumors.  相似文献   
4.
Based on in vitro studies that have demonstrated synergy between 5-fluorouracil (5-FU), leucovorin (LV), and cisplatin (CDDP) against human colon cancer cell lines, a clinical trial was initiated to determine the effects of this combination in patients with advanced unresectable colorectal carcinoma. Fifty-nine patients were enrolled in the study and 12 of them had received prior conventional 5-FU chemotherapy. Treatment consisted of 4 weekly courses of high-dose LV (200 mg/m2) administered by intravenous (IV) bolus, followed by 5-FU (550 mg/m2) and CDDP (20 mg/m2) each administered as a 2-hour infusion on 4 consecutive days. After a median of 5.5 treatment cycles, objective tumor response was seen in 20 of 59 patients (34%) (this included 3 complete remissions). The response rate in the 47 previously untreated patients was 38% (95% confidence limits, 26% to 53%). Stable disease occurred in 16 (27%) patients, whereas the tumor progressed in 23 (39%) patients. The median survival time was 11.5 months, with 15% of the patients alive at 2 years. The regimen was well tolerated and the primary side effects were mild and reversible gastrointestinal symptoms and myelosuppression. There was no episode of life-threatening toxicity. Eastern Cooperative Oncology Group (ECOG) Grade III adverse reactions that required 25% dose reductions occurred in only 14% of the patients. The results of this trial suggest that 5-FU, LV, and CDDP is an active, safe, and well-tolerated combination regimen in patients with advanced colorectal cancer.  相似文献   
5.
We used immunohistochemical techniques to study the distribution of transforming growth factor-beta 1 (TGF-beta 1) and infiltrating lymphocytes and macrophages in human astrocytomas. Thirteen of 15 grade 4 astrocytomas (glioblastomas) showed staining with anti-TGF-beta 1 antibody, predominantly in proliferating endothelial complexes and surrounding small and medium-sized blood vessels. Brain tissue microscopically free of tumor cells (n = 8) and more differentiated astrocytomas of varying grade (1 to 3; n = 6) devoid of endothelial proliferation did not stain with anti-TGF-beta 1. Normal brain contained only rare lymphoreticular cells. The majority of astrocytomas studied, however, contained T lymphocytes and macrophages with smaller numbers of B lymphocytes. The lymphoreticular infiltrates were concentrated primarily in close proximity to blood vessels. Within an individual tumor perivascular regions staining for TGF-beta 1 never contained more than occasional T lymphocytes. Perivascular regions not staining for TGF-beta 1 frequently contained low to high numbers of T lymphocytes. The inverse relationship in the distribution of TGF-beta 1 and lymphocyte infiltrates is compatible with a functional relationship between this cytokine and an immune effector cell response to glioblastomas.  相似文献   
6.
Congenital hypoplasia of the adrenal glands (CHA) is a rare condition, particularly in the absence of a central nervous system (CNS) anomaly. Two major types of CHA have been described in the setting of an apparently normal CNS and pituitary: a cytomegalic type usually with X-linked recessive inheritance and a miniature adult type that, when hereditary, is an autosomal recessive trait. Glycerol kinase deficiency (GKD) is an X-linked recessive trait, and it may be associated with CHA and adrenal insufficiency, presumably because of deletion of adjacent X-linked loci. We report on three sibling infants, one male and two females, with normal CNS and lethal CHA of the miniature adult type, selective absence of pituitary LH; two of the infants also had glycerol kinase (GK) activity that was decreased but not in the GKD range. Restriction fragment length polymorphism (RFLP) analysis of X chromosome markers located at Xp21-p22 was carried out on the maternal grandfather, both parents, two of three affected infants, and a living normal brother. The results excluded the X-linked type of this disorder associated with GKD in this family. Autosomal recessive inheritance is most likely.  相似文献   
7.
8.
1. The pharmacokinetics and toxicity of racemic 5-methyltetrahydrofolic (rac-5-MTHF) acid after i.v. infusion were investigated in 18 patients with advanced colorectal cancer. Doses of 100-600 mg rac-5-MTHF/m2 were administered over 2 h together with a bolus of 500 mg/m2 5-fluorouracil (5-FU) as a midpoint injection. 2. The pharmacokinetics of both diastereoisomers were linear in the range from 100-600 mg 5-MTFH/m2. Independent of the administered dose, the maximal plasma concentration of [R]-5-MTHF was nearly twice that of [S]-5-MTHF. The elimination of [S]-5-MTHF from plasma was considerably faster than that of the [R]-isomer (elimination half-life: 3.1 +/- 1.0 h vs 8.3 +/- 3.2 h). No metabolites were detected in plasma and in urine samples. 3. The plasma protein binding was stereoselective ([R]-5-MTHF bound: 88.2 +/- 2.7%; [S]-5-MTHF bound: 59.9 +/- 6.8%; P < 0.001), causing a significantly higher renal clearance for [S]-5-MTHF when compared with the [R]-isomer (37.5 +/- 23.7 ml min-1 vs 12.7 +/- 11.2 ml min-1, P < 0.001). There was no dose dependence, but gender influenced renal clearance (CLren[R]-5-MTHF: male vs female: 20.5 +/- 14.5 ml min-1 vs 7.8 +/- 4.7 min-1, P = 0.03; CLren [S]-5-MTHF: male vs female: 57.2 +/- 21.7 ml min-1 vs 25.7 +/- 16.2 ml min-1, P = 0.006). 4. Toxic side effects of the combination 5-FU/5-MTHF were rare and generally mild, and included stomatitis, nausea/emesis, diarrhoea, anaemia, leukopenia, and thrombocytopenia. 5. In combination with 500 mg 5-FU/m2 a single dose of 600 mg rac-5-MTHF/m2 can safely be administered to patients with colorectal cancer. A similar therapeutic benefit of 5-MTHF to folinic acid in the biochemical modulation of 5-FU is supported by the comparison of in vitro and in vivo data.  相似文献   
9.
Mixed dysembryoplastic neuroepithelial tumor and ganglioglioma   总被引:3,自引:0,他引:3  
We report a case of a 15-year-old girl with new onset seizures, who had a mixed dysembryoplastic neuroepithelial tumor (DNT) and ganglioglioma of the right parieto-occipital lobe. The tumor appeared well demarcated and exhibited a low T1 and a high T2 signal on magnetic resonance imaging. Architecturally it was in large part intracortical and multinodular, but also featured a leptomeningeal component. The former corresponded to DNT, a proliferation of oligodendroglia-like cells (OLCs) arranged in nodules, as well as comprising a diffuse internodular element featuring “floating neurons” in a mucoid matrix. The leptomeningeal portion of the lesion was a ganglioglioma consisting of large neurons and astrocytes in association with marked desmoplasia. Spacially, the two components abutted one another but appeared distinct. Immunohistochemistry showed the neurons of the ganglioglioma to be positive for class III β-tubulin, synaptophysin, and chromogranin A, whereas the astrocytic cells stained only for glial fibrillary acidic protein. Most OLCs in the DNT were positive for S-100 protein. This apparently mixed lesion suggests that a close histogenetic relationship exists between DNT and ganglioglioma. We postulate that the pluripotential progenitor cells residing in the subpial granular layer may have given rise to the cortical DNT and to the leptomeningeal ganglioglioma. To our knowledge, this is the first detailed histological, immunochemical and ultrastructural report of a mixed DNT and ganglioglioma. Received: 11 August 1997 / Revised, accepted: 24 November 1997  相似文献   
10.
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