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   3966篇
  免费   189篇
  国内免费   28篇
耳鼻咽喉   21篇
儿科学   87篇
妇产科学   35篇
基础医学   397篇
口腔科学   87篇
临床医学   337篇
内科学   1098篇
皮肤病学   92篇
神经病学   306篇
特种医学   179篇
外科学   651篇
综合类   26篇
预防医学   81篇
眼科学   45篇
药学   242篇
中国医学   24篇
肿瘤学   475篇
  2023年   26篇
  2022年   37篇
  2021年   70篇
  2020年   52篇
  2019年   41篇
  2018年   61篇
  2017年   43篇
  2016年   62篇
  2015年   76篇
  2014年   107篇
  2013年   124篇
  2012年   174篇
  2011年   205篇
  2010年   122篇
  2009年   95篇
  2008年   187篇
  2007年   196篇
  2006年   185篇
  2005年   200篇
  2004年   190篇
  2003年   223篇
  2002年   209篇
  2001年   150篇
  2000年   112篇
  1999年   109篇
  1998年   59篇
  1997年   55篇
  1996年   52篇
  1995年   38篇
  1994年   28篇
  1993年   31篇
  1992年   83篇
  1991年   60篇
  1990年   75篇
  1989年   84篇
  1988年   63篇
  1987年   51篇
  1986年   40篇
  1985年   56篇
  1984年   41篇
  1983年   33篇
  1981年   14篇
  1980年   19篇
  1979年   28篇
  1978年   26篇
  1977年   16篇
  1974年   25篇
  1973年   15篇
  1970年   20篇
  1967年   13篇
排序方式: 共有4183条查询结果,搜索用时 15 毫秒
11.
To determine the prognostic factors for patients with pathological T1 (pT1) carcinoma of the ampulla of Vater, 36 consecutive patients with carcinoma of the ampulla of Vater who underwent surgery were retrospectively analyzed in terms of clinicopathological features. The overall 5-year Kaplan-Meier survival in all patients was 50.2%, and the median survival of all patients was 64.0 months. Factors favorably influencing a long-term outcome were the absence of lymph node metastasis (P<0.0001), the absence of ulcer formation of the tumor (P=0.0062), and the absence of tumor invasion into the duodenum (P = 0.0025) and the pancreas (P=0.0098). In a multivariate analysis, lymph node metastasis was the only predictor of survival (P=0.0023). In the pT1 stage patients, 20% of the patients had lymph node metastasis, and their survival was statistically poor compared to the pT1 patients without lymph node metastasis (P=0.017). As for survival after the operation, there was no significant difference between pancreatoduodenectomy and pylorus-preserving pancreatoduodenectomy.  相似文献   
12.
US findings of 81 patients with breast cancer were analyzed respectively to evaluate the usefulness of US in the preoperative diagnosis of internal mammary mode metastases. The internal mammary area (I.M.A.) in which internal mammary nodes lie was shown as a hypoechoic stripe in a sagittal scan along the sternum and as a triangular or spindle-shaped hypoechoic area in a transverse scan in the intercostal space. The US features of each I.M.A. in the first three intercostal spaces were divided into three patterns: Pattern-A wad defined as widening of the ipsilateral side of the I.M.A. compared with the contralateral side; Pattern-C was defined as normal at both sides of the I.M.A. Pathological examination confirmed the node metastases in 85.7% of intercostal scans showing Pattern-A and in 35% of intercostal scans showing Pattern-B. Only one of 189 intercostal scans showing Pattern-C had nodal metastases. The overall accuracy was 88.1% in 243 intercostal scans and 90.1% in 81 patients. We conclude that US is useful in the detection of internal mammary node metastases in patients with breast cancer.  相似文献   
13.
N Uemura  K Ozawa  A Tojo  K Takahashi  A Okano  H Karasuyama  K Tani  S Asano 《Blood》1992,80(12):3198-3204
Since the ras family of proto-oncogenes is supposed to be involved in leukemogenesis by point-mutational activation, we studied the effect of the activated ras gene on the growth of a murine interleukin-3 (IL-3)-dependent cell line, FDC-P2. The human activated c-H-ras gene was transfected into FDC-P2 cells by electroporation using a high-level expression vector, BMGhph, which contains a partial DNA sequence from bovine papillomavirus (BPV) and a hygromycin B (hmB)-resistant gene as a selectable marker. The transformed FDC-P2 cells showed a high incidence of IL-3-independent growth and tumorigenicity in nude mice. These clones did not express or secrete IL-3, suggesting the acquisition of IL-3 independence by a nonautocrine mechanism. The high incidence of autonomous growth may be due to the use of the BMG vector, because (1) the activated ras gene in pBR322 vector (pHs-49) was not so efficient in the induction of IL-3 independence, (2) the c-H-ras genome copies per cell increased in number up to about 50 copies by using the BMG vector, and (3) cotransfection with the activated ras gene and the BPV gene in separate plasmids partly enhanced the incidence of autonomous growth without increasing the copy number of the ras gene compared with transfection with the activated ras gene alone. The present study supports the idea that the activation of ras gene is an important step in malignant transformation of hematopoietic cells and suggests that the BPV gene products may cooperate with ras gene activation probably by affecting the cellular genes that may be involved in multistep leukemogenesis. The BMG vector may be useful to test the transforming ability of oncogenes whose oncogenic potential is relatively low.  相似文献   
14.
We present a case of lung cancer that showed false positive accumulation in an 18F fluorodeoxyglucose positron emission tomography (FDG-PET) scan following induction chemotherapy for suspected metastasis and progression of malignancy. A 66-year-old man was diagnosed with squamous cell carcinoma in the lung, classified as clinical stage IIIA (T2N2M0), and underwent induction chemotherapy. An FDG-PET scan prior to chemotherapy demonstrated accumulation only in the tumor, whereas following treatment it revealed a strong accumulation not only in the tumor, but also in the supraclavicular lymph nodes, which indicated lymph node metastasis. The patient underwent a biopsy of the right supraclavicular lymph node and mediastinoscopy, after which all dissected lymph nodes showed sarcoid reactions and no tumor cells were found pathologically. We concluded that when evaluating the effect of induction chemotherapy for malignancy, a sarcoid reaction might lead to the false positive accumulation of FDG.  相似文献   
15.
16.
Perceptual dysfunction in hemiplegia and automobile driving.   总被引:1,自引:0,他引:1  
Sixteen post-stroke, hemiplegic patients, who requested that they be allowed to return to driving, were extensively evaluated by a physiatrist, psychologist, occupational therapist, and driver training specialist. After they completed a driver training program, the patients were divided into three groups based on their driving program success and follow-ups. Significant differences in the psychological test results were found between Group I (those who drove without any difficulty) and Groups II and III (those who drove limited distance or who failed driver training). Results suggest that patients with significant cognitive and perceptual problems who take training and limit their driving can be safe drivers when they return to driving.  相似文献   
17.
Flavobacterium meningosepticum IFO 12535, a menaquinone (MK) producer, was mutagenized to improve productivity. A mutant, which was resistant to 1-hydroxy-2-naphthoate (HNA), was found to produce MK more abundantly: 34 mg/liter of culture broth and 5.5 mg/g of dry cells. The mutant was less sensitive to inhibition by HNA on MK biosynthesis than the wild-type strain. MK was isolated from cells of the mutant and identified as MK-6 based on its physicochemical characteristics. Mutants, which were given each KCN resistance, aromatic amino acid auxotrophy and no carotenoid productivity, did not show further increase of productivity.  相似文献   
18.
Six solitary gastric polyps in the acid-secreting fundic mucosa were histo-chemically investigated using the mucin histochemistry, immunoperoxidase method, and silver methods for endocrine cells. Histologically, the polyps were grouped into three types : they largely consisted of either hyperplastic foveolar cells (group 1), normal-appearing fundic gland cells with mild cystic changes (group 2) or hyperplastic fundic gland cells with cystic dilatation (group 3). The presence of parietal cells and mucous neck cells was confirmed in all polyps by the immunoperoxidase method using parietal cell autoantibody and the paradoxical Concanavalin A staining, respectively. Regarding the endocrine component, somatostatin-containing cells, Grimelius-positive argyrophil cells, and Fontana-Masson-positive enterochromaffin cells were scattered in the fundic gland area of the polyps as well as in the surrounding normal-appearing fundic mucosa. Gastrin-containing cells were absent. In one of the group 2 polyps and both group 3 polyps, a varying number of glicentin-containing cells were found among the fundic gland components : In one polyp in group 3, glucagon immunoreactivity was detected in the glicentin-containing cells. These findings suggest that some of the polyps express characteristics of the fetal fundic mucosa, since glicentin and glucagon immunoreactivities in normal human stomach have been detected exclusively in the fetal fundus. ACTA PATHOL. JPN. 35: 831–840, 1985.  相似文献   
19.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) affects the thyroid morphologically and/or functionally in adult animals. Recently, the National Toxicology Program conducted a 2-year gavage study of TCDD in female Harlan Sprague-Dawley rats. The only treatment-related alterations found in thyroid follicles were decreased luminal size and increased height of the follicular epithelial cells, without prominent protrusion into the lumen. The present study elucidated the nature of these follicular lesions. Thyroid glands of 10 rats each from the control, high (100 ng/kg/day)-dose, and stop-study (100 ng/kg/day, 30 weeks; vehicle to study termination) groups in the 2-year study were evaluated microscopically. Twenty randomly selected follicles were measured morphometrically in each animal. TCDD treatment significantly decreased the mean ratio of luminal/epithelial areas and increased the mean sectional epithelial height of the high-dose group compared to controls. Thyroid sections were immunostained with antibody against minichromosome maintenance (MCM) proteins, a novel cell-cycle biomarker. The MCM labeling index of the high-dose group was significantly higher than that of the control; however, the TUNEL labeling index was also higher in the high-dose group than the control. All data from the stop group were comparable to those from controls. These results indicate that the follicular cell response was hypertrophic and reversible. This information should contribute to diagnosis of nonneoplastic thyroid follicular lesions in rats.  相似文献   
20.
T-helper-1 (Th1) cytokines play an important role in Crohn's disease, and interleukin-12 (IL-12), which is composed of two subunits, p40 and p35, drives Th1 differentiation. In previous reports, IL-12 p40 was shown to prevent IL-12 from binding to the receptor. We demonstrate here the effect of IL-12 p40 overexpression in intestinal epithelia on enterocolitis mediated by Th1 cells in IL-10-deficient (IL-10(-/-)) mice on a C57BL/6J background. IL-10 deficient (IL-10(-/-))/T3b-IL-12 p40+ (IL-12 p40+) mice and IL-10(-/-)/T3b-IL-12 p40- (IL-12 p40-) mice were generated by crossing T3b-IL-12 p40 transgenic mice and IL-10(-/-) mice. At 8 weeks of age, IL-12 p40+ mice did not show any clinical manifestations of colitis. The colon length of IL-12 p40- mice became shorter than that of IL-12 p40+ mice. The histological score of IL-12 p40+ mice was lower. Interferon-gamma (IFN-gamma) production was suppressed in both the mesenteric lymph node cell culture and colon tissue culture of IL-12 p40+ mice. There was no significant difference in IL-4 production and tumor necrosis factor-alpha (TNF-alpha) production between the two groups. These results show that overexpression of IL-12 p40 in intestinal epithelia prevents enterocolitis in IL-10(-/-) mice by suppressing IFN-gamma production, and suggest a potential clinical application of IL-12 p40 for Crohn's disease. Furthermore, these results also suggest that local gene transduction in the intestinal epithelium may be a potent therapeutic approach for Crohn's disease.  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