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   12827篇
  免费   787篇
  国内免费   103篇
耳鼻咽喉   131篇
儿科学   292篇
妇产科学   233篇
基础医学   1881篇
口腔科学   249篇
临床医学   801篇
内科学   3242篇
皮肤病学   319篇
神经病学   778篇
特种医学   471篇
外科学   2291篇
综合类   43篇
预防医学   440篇
眼科学   186篇
药学   777篇
中国医学   25篇
肿瘤学   1558篇
  2023年   114篇
  2022年   163篇
  2021年   355篇
  2020年   196篇
  2019年   271篇
  2018年   326篇
  2017年   281篇
  2016年   336篇
  2015年   324篇
  2014年   393篇
  2013年   457篇
  2012年   721篇
  2011年   809篇
  2010年   417篇
  2009年   408篇
  2008年   721篇
  2007年   684篇
  2006年   654篇
  2005年   629篇
  2004年   567篇
  2003年   530篇
  2002年   514篇
  2001年   361篇
  2000年   359篇
  1999年   319篇
  1998年   141篇
  1997年   123篇
  1996年   80篇
  1995年   64篇
  1994年   46篇
  1993年   55篇
  1992年   199篇
  1991年   170篇
  1990年   189篇
  1989年   209篇
  1988年   204篇
  1987年   163篇
  1986年   151篇
  1985年   132篇
  1984年   108篇
  1983年   84篇
  1982年   38篇
  1979年   57篇
  1978年   40篇
  1977年   45篇
  1974年   44篇
  1973年   50篇
  1972年   43篇
  1970年   49篇
  1968年   37篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
A 67-year-old man with gallbladder cancer was treated by cholecystectomy and extrahepatic bile duct resection with regional lymph node dissection. At 10 months after surgery, CT demonstrated para-aortic lymph node recurrence. Single drug chemotherapy of UFT at 400 mg was started. After one month, the lymph node recurrence could not be detected by CT. UFT may be the primary candidate for chemotherapy for lymph node recurrence of gallbladder cancer.  相似文献   
992.
We often observe pulmonary metastases in patients following advanced colorectal cancer, especially rectal cancer. The prognoses of LM3 patients and patients with histological v2 factor in the primary site were unfavorable. Surgery was not indicated in these cases. Some patients experienced rapid progression during the standby period for surgery. For the surgery group, we recommend systemic reexaminations after several months. Pulmonary resections for metastatic colorectal cancer are beneficial to the selected patients and 5-year survival rate was 52.6%. New pulmonary relapses were also encountered which were the cause of death among the surgical patients. Close follow-up and multimodal therapy including surgery contributed to longer survival for postoperative pulmonary metastatectomy patients with colorectal cancer.  相似文献   
993.
ErbB2 and alpha6 integrin have been implicated in malignancy of breast cancer cells. Here we have determined the influence of alpha6beta1 integrin on erbB2 signaling in anchorage-independent growth, using MDA-MB435 breast cancer cells. Firstly, we transfected the cells with erbB2 cDNA, and isolated cells with high or low levels of alpha6beta1 integrin by cell sorting (alpha6H-ErbB and alpha6L-ErbB). We found that an erbB ligand, heregulin beta1, enhanced growth activity of alpha6L-ErbB cells, but not alpha6H-ErbB cells. Secondly, we established cells expressing a beta4 integrin deletion mutant (beta4-deltacyt), which selectively inhibited alpha6beta1 integrin expression and adhesion to laminin-1. Again, heregulin beta1 enhanced the growth of erbB2 cDNA-transfected beta4-deltacyt cells, but not mock cells. Western blot analysis revealed that heregulin beta1 stimulated phosphorylation of Akt and its downstream molecules, GSK3beta and p70S6kinase, and that the extent of phosphorylation was greater in ErbB2/beta4-deltacyt cells than ErbB2/mock cells. Furthermore, we found that the erbB2 cytoplasmic domain was truncated in ErbB2/mock cells, which was independent of ligand stimulation and adhesion, and was suppressed by proteasome inhibitors. These results suggest that alpha6beta1 integrin inhibits erbB2 signals by inducing proteasome-dependent proteolytic cleavage of the erbB2 cytoplasmic domain, and may thereby contribute to the regulation of tumor growth.  相似文献   
994.
In this study, we examined antitumor activity of a mouse CC chemokine ILC/CCL27 and a mouse CX(3)C chemokine fractalkine/CX(3)CL1 in vivo. We generated recombinant adenovirus vectors with a fiber mutation, encoding mILC (Ad-RGD-mILC) and mFKN (Ad-RGD-mFKN). We confirmed tumor cells infected with Ad-RGD-mILC and Ad-RGD-mFKN to express and release these chemokines. Tumor rejection experiments in vivo were carried out by inoculating OV-HM cells infected with Ad-RGD-mILC or Ad-RGD-mFKN into immunocompetent mice. mILC significantly suppressed the tumor growth, whereas no such significant effect was observed by mFKN. The antitumor activity induced by mILC was T cell dependent, involving both CD4(+) and CD8(+) T cells. Immunohistochemical analysis revealed accumulation of both CD3(+) lymphocytes and NK cells in the tumor tissue transduced with mILC and mFKN. However, there was a significant difference in the distribution of infiltrating cells. Furthermore, mFKN appeared to have an angiogenic activity, which might have masked its tumor suppressive activity. Collectively, ILC/CCL27 may be a good candidate molecule for cancer gene therapy.  相似文献   
995.
Alterations of the HER-2 (erbB-2/neu) proto-oncogene have been associated with carcinogenesis and poor prognosis of certain cancers. A single nucleotide polymorphism (Ile/Val, A/G) in the transmembrane domain was reported to be associated with a risk of breast cancer. In our study, we examined the association between the HER-2 polymorphism and gastric carcinoma. The Ile/Ile, Ile/Val and Val/Val genotypes were found in 146 (68.9%), 56 (26.4%) and 10 (4.7%) of 212 gastric cancer patients and in 234 (81.5%), 48 (16.7%) and 5 (1.8%) of 287 control subjects, respectively. The Ile/Val or Val/Val genotype was significantly more frequent in patients than in controls (p = 0.005 and 0.033, respectively). The OR of Val/Val genotype then revealed a significantly enhanced risk of 3.25 (95% CI 1.09-9.70) compared to Ile/Ile genotype; heterozygous Ile/Val genotype showed an intermediate risk of 1.97 (1.27-3.06). In patients, carcinomas of advanced stage were significantly more frequent in patients with Ile/Val or Val/Val genotype than those with Ile/Ile genotype (p < 0.001). The logistic regression analysis for tumor invasion, lymph node metastasis and distant metastasis revealed that lymph node metastasis was most closely associated with the HER-2 genotype. These results suggest that this nucleotide polymorphism in the transmembrane domain-coding region of HER-2 could be associated with development of gastric carcinoma and may serve as a predictor of risk for a malignant phenotype of gastric cancer. The association of HER-2 genotype with clinicopathologic characteristics of gastric cancer was also suggested, which has to be confirmed with a larger sample size.  相似文献   
996.
BACKGROUND: To identify antigens specifically recognized by the immune surveillance system in patients with hepatocellular carcinoma (HCC), the authors examined two complementary DNA (cDNA) libraries of moderately differentiated HCC by serologic analysis of recombinant cDNA expression libraries (SEREX). METHODS: The libraries were screened with autologous patients' sera, and sequences of the reacted clones were determined. To study the immunoreactivity of the antigens, sera from 20 patients with HCC, from 20 healthy volunteers, and from 16 patients with chronic viral hepatitis were examined. RESULTS: Twenty-seven antigens were identified. They included SART1, p57Kip2, ROCK-1, gamma-catenin, and heat shock proteins, which are classified as tumor-associated genes. Three of 27 antigens-Tat-binding protein-1 (TBP-1), beta4 integrin-binding protein (p27[BBP]), and ribosomal protein L30 (rpL30)-were reacted predominantly with sera from patients with HCC (55% of patients, 45% of patients, and 20% of patients, respectively). Patients in the control group had no antibodies against these three antigens. Seventy percent of patients with HCC had the antibody against at least one of these antigens. CONCLUSIONS: Disease specific humoral immune response against TBP-1, p27(BBP), and rpL30 was induced in patients with HCC, and the antibodies against these antigens also may be used as tumor markers.  相似文献   
997.
Prostate cancer is one of the most common age-related malignancies. The occurrence frequency of prostate cancer is very different according to prostate zones. The prostate stroma is an important element in growth and differentiation of the normal prostate and also has a close relationship to the occurrence of benign prostatic hypertrophy and cancer. We examined 14 cases of normal prostate tissues obtained at autopsy and 11 cases of prostate cancer tissues at radical prostatectomy specimens with cancers for clarifying the characteristics of stromal components in the normal prostate and the correlation between the stroma and the occurrence of prostate cancers. Stromal cells, such as smooth muscle cells, myofibroblasts and fibroblasts were identified by immunohistochemistry (IHC). Connective tissue fibers were detected by Elastica van Gieson and also IHC stain. Quantitative analysis of the smooth muscle tissue and connective tissue fibers were performed using a computer image analyzer system. In the normal prostate, stromal components varied in each zone. Every zone of the prostate contained smooth muscle cells, myofibroblasts, fibroblasts and collagen fibers. Elastic fibers were clearly visible in the transition zone. Smooth muscle cells were the main stromal component but less numerous in the frequent occurrence zone (peripheral zone) of prostate cancer (p<0.05). Myofibroblasts and fibroblasts were found either in normal or cancer tissues, although a few in number. The increase of collagen fibers accompanied decrease of smooth muscle cells as prostate cancer grade increased (p<0.05). The characteristics of stromal components and their amounts in the normal prostate appear to correlate with a distinct predilection for cancer occurrence in the peripheral zone and a weak stromal reaction in prostate cancers.  相似文献   
998.
The vasorelaxant activities of chicoric acid (Compound 1) from Cichorium intybus and dicaffeoyl-meso-tartaric acid (Compound 2) from Equisetum arvense L. in isolated rat aorta strips were studied. Compound 1 is a diester composed of (S,S)-tartaric acid and caffeic acid, and 2 is composed of its meso type. Both 1 and 2 showed slow relaxation activity against norepinephrine (NE)-induced contraction of rat aorta with/without endothelium. These compounds did not affect contraction induced by a high concentration of potassium (60 mM K+), while they inhibited NE-induced vasocontraction in the presence of nicardipine. These results show that the inhibition by 1 and 2 of NE-induced vasocontraction is due to a decrease in calcium influx from the extracellular space caused by NE. In addition, dicaffeoyl tartaric acids showed vasorelaxant activity, regardless of their stereochemistry.  相似文献   
999.
To investigate the phenotypes of stromal cells in primary lung carcinomas, we examined the distribution of CD34-positive stromal cells in primary lung carcinomas, with special reference to histological types. In total 26 surgically resected primary lung carcinomas (13 adenocarcinomas, 10 squamous cell carcinomas, 2 large cell carcinomas, and 1 small cell carcinoma and their normal tissues were examined. CD34-positive stromal cells were observed in connective tissue adjacent to the bronchiolar and bronchial epithelium in normal lung tissues. Nine of the 13 adenocarcinomas had CD34-positive stromal cells in the tumor stroma, whereas none of the other histological type tumors examined had CD34-positive stromal cells. These results suggest that CD34-positive stromal cells are specific in the stroma of primary lung adenocarcinomas, and there is a possibility that CD34-positive stromal cells may play a supportive role in primary lung adenocarcinomas.  相似文献   
1000.
In addition to natural killer (NK) cells, T cells expressing natural killer cell markers, CD56 or CD57 (NK type T cells), have been considered to play an important role in antitumor immunity. We examined the proportion of NK cell and NK type T cell subsets in the peripheral blood from patients with gastric cancer. The IFN-gamma production capacity and population of cytoplasmic perforin positive cells in peripheral blood mononuclear cells (PBMC) were evaluated. Peripheral blood samples were obtained from 56 patients with gastric cancer and 21 healthy volunteers. The proportion of CD56- CD57+ T cells (CD57+ T cells) was significantly higher in advanced gastric cancer patients than those in healthy volunteers and patients with early stage gastric cancer, whereas no correlation was observed between the proportion of CD56+ T cells or NK cells and tumor progression. Furthermore, a significant decrease of CD8+ CD57+ T cells was found in patients with advanced gastric cancer. The proportion of CD57+ T cells did not correlate with interferon-gamma (IFN-gamma) production from PBMC in gastric cancer patients, although a significant correlation was found between them in healthy volunteers. The proportion of perforin positive CD57+ T cells, especially CD8+ CD57+ T cells, in patients with gastric cancer was markedly lower than that in healthy volunteers. Collectively, although the proportion of CD57+ T cells in PBMC was found to increase with tumor progression, their function in antitumor immunity is impaired in patients with gastric cancer.  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