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   16820篇
  免费   605篇
  国内免费   165篇
耳鼻咽喉   133篇
儿科学   313篇
妇产科学   144篇
基础医学   1842篇
口腔科学   258篇
临床医学   979篇
内科学   5416篇
皮肤病学   377篇
神经病学   1016篇
特种医学   604篇
外科学   2757篇
综合类   67篇
一般理论   3篇
预防医学   326篇
眼科学   433篇
药学   905篇
  3篇
中国医学   35篇
肿瘤学   1979篇
  2024年   82篇
  2023年   188篇
  2022年   296篇
  2021年   556篇
  2020年   339篇
  2019年   449篇
  2018年   435篇
  2017年   350篇
  2016年   426篇
  2015年   449篇
  2014年   600篇
  2013年   711篇
  2012年   1187篇
  2011年   1316篇
  2010年   766篇
  2009年   580篇
  2008年   996篇
  2007年   1158篇
  2006年   1073篇
  2005年   1057篇
  2004年   969篇
  2003年   900篇
  2002年   928篇
  2001年   156篇
  2000年   122篇
  1999年   144篇
  1998年   186篇
  1997年   179篇
  1996年   152篇
  1995年   119篇
  1994年   100篇
  1993年   93篇
  1992年   71篇
  1991年   57篇
  1990年   56篇
  1989年   52篇
  1988年   33篇
  1987年   31篇
  1986年   33篇
  1985年   23篇
  1984年   25篇
  1983年   16篇
  1982年   22篇
  1981年   22篇
  1980年   16篇
  1979年   15篇
  1978年   9篇
  1977年   9篇
  1976年   7篇
  1974年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Tumor invasion-inhibiting factors were purified from bovine liver using an in vitro system for estimating the tumor invasion ability. The acid-ethanol extract of liver was subjected to ultrafiltration (Amicon PM10 membrane), and the fraction corresponding to the molecular weight range below 10,000 was further fractionated by ion-exchange (DEAE-Toyopearl), gel filtration (Bio-Gel P6), and reverse-phase (C18) chromatographies. Two types of active polypeptides with molecular weights of about 5,000 and 2,000 were purified and named IIF-1 and IIF-2, respectively. Both peptides inhibited tumor invasion with half-maximum concentrations of 2–6 ng/ml in vitro . The amino acid compositions of both peptides were determined.  相似文献   
102.
103.
We have sometimes encountered invasive ductal carcinomas (IDCs) of the pancreas containing intraductal carcinoma components in the intra- and / or extra-tumor area. The purpose of this study was to investigate whether intraductal carcinoma components would be useful for predicting the outcome of IDC patients. Forty-seven surgically treated IDCs were examined, and all histological tumor sections were stained with Elastica to accurately confirm intraductal carcinoma components. Well-known clinicopathological parameters that exhibited a significant correlation in the univariate analyses for predicting disease-free survival (DFS) and overall survival (OS) were entered into the Cox proportional hazard multivariate analysis. Since the lowest P-value predicting DFS or OS periods was observed in IDCs with more than 10% intraductal carcinoma components and those with 10% or less intraductal carcinoma components (P = 0.028 and P = 0.019), we established the cutoff value of intraductal carcinoma components at 10%. In the multivariate analyses for DFS and OS, the presence of more than 10% intraductal carcinoma components showed a marginally significant increase in the hazard rate (HR) of tumor recurrence (P = 0.067) and significantly increased the HR of mortality (P = 0.040). The present study demonstrated that IDCs with more than 10% intraductal carcinoma components were associated with a significantly better patient outcome than those with 10% or less intraductal carcinoma components.  相似文献   
104.
105.
Appendicitis can rarely occur in association with carcinoma of the caecum, particularly in elderly patients. We report a case of acute appendicitis provoked by an adenocarcinoma of the caecum which obstructs the lumen of the appendix in a 58-year-old man. The patient underwent an ileocaecal resection with lymph node dissection. The difficulties of identifying a small tumor at laparotomy and the implication for optimal treatment are emphasized.  相似文献   
106.
Background. About 2% of patients who undergo partial distal gastrectomy for gastroduodenal diseases develop gastric remnant cancer 10 to 30 years after the gastrectomy. It is important in clinical practice to determine a molecular marker to identify patients susceptible to gastric remnant cancer. Methods. We investigated nine gastric remnant cancers (from nine individuals who had gastrectomies for primary gastric cancer or gastroduodenal ulcer) for microsatellite instability (MSI) at six loci, using the polymerase chain reaction (PCR). A control group of ten patients with sporadic gastric cancers in the upper third of the stomach was also similarly analyzed. Results. MSI was demonstrated in eight of nine cancers from the individuals who had had primary gastric cancer or gastroduodenal ulcer (88.9%) compared with two of ten cancers from the individuals with sporadic gastric cancer in the upper third of the stomach (20%). Conclusion. These results suggest that one or more MSI is associated with remnant gastric cancer after gastrectomy. Received on Sept. 6, 1999; accepted on Dec. 20, 1999  相似文献   
107.
Background. The prognosis of scirrhous gastric cancer remains poor when it is treated with surgical resection alone or chemotherapy alone. A phase II study of sequential high-dose methotrexate and fluorouracil, combined with doxorubicin, as a neoadjuvant chemotherapy was conducted in an attempt to evaluate the efficacy of this regimen in improving the survival of patients with scirrhous gastric cancer. Methods. Patients were eligible if they had potentially resectable scirrhous gastric cancer with adequate organ functions and no prior treatment. The treatment schedule consisted of methotrexate (1 g/m2, day 1) fluorouracil (1.5 g/m2, day 1), leucovorin (15 mg/m2, days 2–4), and doxorubicin (30 mg/m2, day 15), repeated at a 28-day interval, and followed by radical surgery. Results. A total of 20 eligible patients were registered. Objective responses in the neoadjuvant chemotherapy segment were observed in 3 of the 20 (15%) patients. No complete remission was observed. The neoadjuvant chemotherapy was associated with grade 3 or 4 neutropenia in 14 of the 20 (70%) patients. The median time from the initial therapy to the operative day was 82 days. Thirteen of the 20 (65%) patients underwent curative resection. No treatment-related deaths occurred. However, the 2-year survival rate in this treatment program (25%) did not show any superiority over that in historical controls. Conclusions. Sequential high-dose methotrexate and fluorouracil, combined, with doxorubicin, as a neoadjuvant chemotherapy for scirrhous gastric cancer did not improve the survival rate in spite of improving the curative resection rate. Received: August 2, 2001 / Accepted: September 27, 2001  相似文献   
108.
International Journal of Clinical Oncology - Lymph node metastasis is a critical prognostic factor in cervical cancer. Considering the potential complications of lymphadenectomy and desirability of...  相似文献   
109.
110.
In a cross-sectional study, we examined age-related differences in visuo-spatial ability associated with image rotation, using two variants of Piaget's 'Three-Mountain Task.' The object-mental rotation (OMR) task detects the ability to mentally rotate an image, whereas the subject-mental rotation (SMR) task reveals the ability to mentally change one's perspective. A group of 33 young adults, 26 middle-aged adults, and 31 elderly normal adults were studied. Both tasks revealed age-related differences in performance but a larger difference between middle-aged and elderly group was observed for SMR than OMR performance. Age-related increases in the 'egocentric' type of error were found only on the SMR task. The results suggest that the ability to mentally change one's perspective declines with age, perhaps more than the ability to mentally rotate objects.  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