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   7522篇
  免费   339篇
  国内免费   73篇
耳鼻咽喉   72篇
儿科学   128篇
妇产科学   158篇
基础医学   830篇
口腔科学   134篇
临床医学   466篇
内科学   2008篇
皮肤病学   154篇
神经病学   450篇
特种医学   266篇
外科学   1498篇
综合类   18篇
一般理论   1篇
预防医学   189篇
眼科学   187篇
药学   355篇
中国医学   14篇
肿瘤学   1006篇
  2024年   9篇
  2023年   65篇
  2022年   130篇
  2021年   198篇
  2020年   116篇
  2019年   137篇
  2018年   211篇
  2017年   146篇
  2016年   166篇
  2015年   198篇
  2014年   249篇
  2013年   313篇
  2012年   534篇
  2011年   615篇
  2010年   344篇
  2009年   301篇
  2008年   552篇
  2007年   566篇
  2006年   500篇
  2005年   490篇
  2004年   448篇
  2003年   448篇
  2002年   387篇
  2001年   66篇
  2000年   48篇
  1999年   65篇
  1998年   101篇
  1997年   63篇
  1996年   64篇
  1995年   43篇
  1994年   55篇
  1993年   38篇
  1992年   32篇
  1991年   22篇
  1990年   17篇
  1989年   21篇
  1988年   29篇
  1987年   19篇
  1986年   10篇
  1985年   8篇
  1984年   15篇
  1983年   12篇
  1982年   14篇
  1981年   12篇
  1980年   8篇
  1978年   13篇
  1977年   10篇
  1976年   3篇
  1975年   7篇
  1974年   3篇
排序方式: 共有7934条查询结果,搜索用时 15 毫秒
31.
32.
Infantile hemangioendothelioma of the thymus is a rare disease. We describe a patient who developed a large anterior mediastinal mass, severe thrombocytopenia and massive pleural effusion at 1 month of age. Glucocorticosteroid and irradiation therapy had no effect on either the tumor size or clinical symptoms and the tumor was resected subtotally. Three months after the subtotal resection, the remaining tumor had almost disappeared and the symptoms had resolved. The patient has now been well for 1 year after surgery without evidence of recurrence. The tumor tissue was characterized by prominent vascular endothelial proliferation intermixed with a normal thymic structure, producing a picture consistent with that of an infantile hemangioendothelioma in the thymus, lmmunohistochemically, the tumor cells showed positive staining for vimentin, factor VIII and CD34. The DNA stemline and proliferative activity were examined by flow cytometry, which revealed a diploid stemline with a low growth fraction. DNA content and cell cycle analyses of the tumor tissue may be useful for predicting the biological behavior of the tumor.  相似文献   
33.
34.
BACKGROUND/OBJECTIVESOocyte lipid droplets play a crucial role in meiosis and embryo development. Biotin is associated with fatty acid synthesis and is the coenzyme for acetyl-CoA carboxylase (ACC). The effects of a biotin deficiency on the oocyte lipid metabolism remain unknown. This study examined the effects of a biotin deficiency and its replenishment on murine 1) oocyte lipid droplet levels, 2) ovary lipid metabolism, and 3) oocyte meiosis.MATERIALS/METHODSMice were divided into 3 groups: control, biotin deficient (BD), and recovery groups. The control and BD groups were fed a control diet or BD diet (0.004 or 0 g biotin/kg), respectively. The recovery group mice were fed a BD diet until day 21, and were then fed the control diet from days 22 to 64. This study then quantified the oocyte lipid droplet levels, assessed the oocyte mitochondrial function, and examined the ability of oocytes to undergo meiosis. Ovarian phosphorylated ACC (p-ACC), lipogenesis, β-oxidation, and ATP production-related genes were evaluated.RESULTSThe BD group showed a decrease in lipid droplets and mitochondrial membrane potential and increased p-ACC levels. In the recovery group, the hepatic biotin concentration, ovarian p-ACC levels, and mitochondrial membrane potential were restored to the control group levels. On the other hand, the quantity of lipid droplets in the recovery group was not restored to the control levels. Furthermore, the percentage of oocytes with meiotic abnormalities was higher in the recovery group than in the control group.CONCLUSIONSA biotin deficiency reduced the oocyte lipid droplet levels by downregulating lipogenesis. The decreased lipid droplets and increased oocyte meiosis failure were not fully restored, even though the biotin nutrition status and gene expression of lipid metabolism was resumed. These results suggest that a biotin deficiency remains robust and can be long-lasting. Biotin might play a crucial role in maintaining the oocyte quality.  相似文献   
35.
A 28-year-old Japanese woman had an invasive hydatidiform mole which was diagnosed by means of transvaginal ultrasonography. After the two initial courses of systemic methotrexate (MTX) therapy given over a period of weeks, the tumor was 14 mm in diameter and the surrounding blood supply remained rich. In addition to the two initial courses of systemic MTX therapy, local ultrasound-guided injection of MTX therapy was given three times, once per week. After the local MTX treatment, the betahCG level, which had been as high as 240 ng/mL, dropped to less than 0.1 ng/mL. We then gave two additional courses of systemic MTX therapy (once per week). More than 3 years have passed since the final systemic MTX therapy, and the patient's serum betahCG levels continue to be less than 0.1 ng/mL. An invasive mole can be treated with an ultrasound-guided local injection of MTX in addition to the established systemic MTX treatment.  相似文献   
36.

Objectives

A combination of platinum-based chemotherapy and radiotherapy is the standard treatment for nasopharyngeal carcinoma (NPC). However, the efficacy of chemotherapy has reached a plateau. Many autophagy studies suggest that autophagy can either promote or suppress to cancer progression. Thus, a role of autophagy in the acquisition of chemoradioresistance has recently been a notable event. Therefore, we examined the relationship between autophagy and chemotherapy in NPC.

Methods

The expression of Beclin 1 and microtubule-associated protein light chain 3 (LC3), a marker of autophagy, was determined by immunohistochemistry in the biopsy samples of patients with NPC before and after the first course of chemotherapy. Additionally, to investigate in the effect of autophagy suppression in chemotherapy, NPC cell line C666-1 cells were treated with cisplatin and/or chloroquine, an inhibitor of autophagy.

Results

The expression of Beclin 1 increased after chemotherapy in all patients. In NPC cell line C666-1, compared to cisplatin alone, combination therapy (cisplatin and chloroquine) reduced cell viability, and promoted cell apoptosis.

Conclusions

These results suggest that autophagy, represented by Beclin 1, is upregulated after chemotherapy in both in vitro and in vivo NPC studies. Inhibition of autophagy could therefore be new strategy for NPC treatment.  相似文献   
37.
38.
Progestin inhibits the growth of normal and cancerous endometria via the progesterone receptor (PR), but the distinct functions and signalings of PR subtypes have not been fully understood. The aim of the present study was to dissect the key pathways of progestin to inhibit endometrial epithelial growth. Immortalized endometrial epithelial cells (EM-E6/E7/TERT) with stable PRA or PRB expression were established and used for the experiments. In vitro growth inhibition by progestin was mainly observed in EM-E6/E7/TERT cells with PRB rather than those with PRA. RT-PCR assay confirmed that FOXO1, a key gene for progestin action, was up-regulated by progestin in a PRB-dependent manner. cDNA microarray analysis identified IGFBP-1, which contains FOXO1 binding sites on its promoter, to be induced by medroxyprogesterone acetate (MPA) in EM-E6/E7/TERT cells with PRB but not with PRA. siRNA knockdown of FOXO1 disturbed the induction of IGFBP-1 by MPA, while IGFBP-1 knockdown showed no effect on MPA-induced FOXO1 expression, indicating that FOXO1 is an upstream regulator of IGFBP-1. Luciferase reporter assays showed that MPA activated the IGFBP-1 promoter, which was cancelled by FOXO1 knockdown. Chromatin immunoprecipitation assay confirmed the in vivo binding of FOXO1 to the core promoter of IGFBP-1. IGFBP-1 knockdown significantly attenuated the growth inhibitory effects of MPA. The FOXO1/IGFBP-1 axis is essential for PRB-dependent growth inhibition of endometrial epithelial cells, offering a potential therapeutic clue to enhance the progestin effect.  相似文献   
39.
40.
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