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   590篇
  免费   52篇
  国内免费   8篇
耳鼻咽喉   1篇
儿科学   23篇
妇产科学   18篇
基础医学   81篇
口腔科学   10篇
临床医学   53篇
内科学   131篇
皮肤病学   38篇
神经病学   40篇
特种医学   12篇
外科学   47篇
综合类   17篇
预防医学   52篇
眼科学   8篇
药学   63篇
中国医学   7篇
肿瘤学   49篇
  2024年   1篇
  2023年   21篇
  2022年   42篇
  2021年   45篇
  2020年   31篇
  2019年   30篇
  2018年   53篇
  2017年   46篇
  2016年   31篇
  2015年   21篇
  2014年   24篇
  2013年   45篇
  2012年   41篇
  2011年   44篇
  2010年   19篇
  2009年   25篇
  2008年   26篇
  2007年   14篇
  2006年   19篇
  2005年   21篇
  2004年   12篇
  2003年   8篇
  2002年   6篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1998年   2篇
  1997年   4篇
  1996年   1篇
  1993年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有650条查询结果,搜索用时 15 毫秒
61.
The distribution of natural nuclide gamma-ray activities and their respective annual effective dose rates, produced by potassium-40 (40K), uranium-238 (238U), thorium-232 (232Th), and radium-226 (226Ra), were determined for 14 oilfield scale samples from the Middle East. Accumulated radioactive materials concentrate in tubing and surface equipment, and workers at equipment-cleaning facilities and naturally occurring radioactive materials (NORMs) disposal facilities are the population most at risk for exposure to NORM radiation. Gamma-spectra analysis indicated that photo-gamma lines represent the parents of 10 radioactive nuclides: 234Th, plutonium-239, actinium-228, 226Ra, lead-212 (212Pb), 214Pb, thallium-238 (208Tl), bismuth-212 (212Bi), 214Bi, and 40K. These nuclides represent the daughters of the natural radioactive series 238U and 232Th with 40K as well. The mean activity concentration of 238U, 232Th, and 40K were found to be 25.8 ± 11.6, 18.3 ± 8.1, and 4487.2 ± 2.5% Bq kg−1 (average values for 14 samples), respectively. The annual effective dose rates and the absorbed doses in air, both indoor and outdoor, for the samples were obtained as well. The results can be used to assess the respective hazard on workers in the field and represent a basis for revisiting current engineering practices.  相似文献   
62.
63.

Objectives

Gestational diabetes mellitus (GDM) is recognized as an imbalance between insulin resistance and insulin secretion, leading to maternal hyperglycemia. Previous studies in a Saudi population indicated a high frequency of Paraoxonase 1 glutamine 192 to arginine (PON1 Q192R) polymorphism, suggesting this polymorphism as an additional risk factor. The present study was designed to explore the possible association between the PON1 Q192R polymorphism and GDM in a Saudi population.

Methods

This case–control study was carried out in 500 pregnant women, including 200 GDM cases and 300 non-GDM women. Genotyping for PON1 Q192R (rs662) variants was performed by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP).

Results

The results of the present study indicates that Q192R polymorphism was significantly associated with GDM in a Saudi population with the minor allele frequency (MAF) (p = 0.0007). Q192R genotypes and alleles showed a strong association with GDM (p = 0.009 and p = 0.0007, respectively).

Conclusion

In conclusion, these findings suggest that the PON1 Q192R polymorphism has high MAF in GDM in the studied Saudi population.  相似文献   
64.
Background and study aimsHepatitis C virus (HCV) is considered the most common aetiology of chronic liver disease (CLD) in Egypt. The disease severity ranges from mild illness to cirrhosis and hepatocellular carcinoma. A role for apoptosis in liver damage caused by HCV chronic infection has been suggested. Cytokeratin 18 (CK-18) is the major intermediate filament protein in the liver and is a known caspase substrate in hepatocyte apoptosis. Therefore, we analysed the serum and tissue levels of CK-18 in patients with chronic HCV infection to evaluate its role in hepatocyte apoptosis. We also correlated CK-18 expression with the severity of hepatic pathology.Patients and methodsThis study examined 80 Egyptian patients with liver disease. There were 69 patients with chronic hepatitis C and 11 patients with hepatitis C-induced cirrhotic changes. Fifteen healthy controls were also included in the study. The levels of CK-18 fragment were quantified in paired serum and liver biopsy samples.ResultsThe serum and tissue CK-18 levels were reduced in chronic HCV patients compared to early cirrhosis patients. This result indicates that serum levels of CK-18 and the hepatic expression of CK-18 might play an important role in disease progression. The serum and tissue levels of CK-18 were significantly increased and directly correlated with inflammation severity, stage of fibrosis, and ALT levels in the chronic HCV group and the cirrhotic liver group. There was no significant difference in viral load between patient cohorts.ConclusionThe serum level and the hepatic expression of CK-18 are related to disease activity and are directly correlated with METAVIR scoring. This result suggests that serum CK-18 levels may be useful for monitoring disease activity in chronic HCV and liver cirrhosis patients.  相似文献   
65.
66.
There are adverse physiologic effects of pain in neonates, and effective pain management must be an essential aspect of neonatal care. In this study we assessed the effect of a nonmaternal familiar scent on the neonatal pain responses. This study included 135 neonates randomly assigned to one of three groups. During arterial puncture, one group was exposed to a vanillin scent on a gauze pad held next to their nose. They were familiarized with it the night before blood sampling by a scented gauze pad placed in the incubator next to their head for an average duration of 8.65 hours. The second group was not familiarized with the scent but was exposed to it during the procedure. The third group was neither familiarized nor exposed to the scent. The duration of crying in the familiar scent group was significantly lower than in the two other groups. Comparison of the physiologic parameters showed less variation in oxygen saturation level during arterial puncture in the familiar scent group. In this study, a familiar scent could reduce crying and oxygen consumption during arterial puncture.  相似文献   
67.
Background: Recent studies have demonstrated the usefulness of gene-modified tumor cells for immunotherapy. Using the tumorigenic murine fibrosarcoma, MCA 106, we investigated the effects of localized interferon-γ (IFNg) secretion on tumorigenicity and on long-term memory. Methods: The murine IFNg (MuIFNg) gene was introduced into tumor cells. High and low IFNg-secreting clones were isolated. C57BL/6 mice were injected subcutaneously (s.c.) with either parental (P), high or low IFNg-secreting (H- or L-IFNg) cells, and tumor growth was assessed weekly. Spleens were harvested on different days postinjection (p.i.) to assess in vitro cytolytic activity. In parallel, tissues from injection sites were stained with macrophage-, CD4-, and CD8-detecting antibodies. Mice were injected s.c. with H-IFNg MCA106 tumor. After 150 days the animals were rechallenged s.c. with MCA106P in one leg and with irrelevant syngeneic tumor in the other. Results: Both P- and L-IFNg cells had similar growth, whereas the H-IFNg cells never grew. Only splenocytes from the H-IFNg animals showed in vitro CTL activity persisting until day 30 p.i. Histological data revealed a macrophage and CD4+ infiltrate much earlier in the H-IFNg group compared with the P group. Only the irrelevant, syngeneic tumor grew in animals previously injected with H-IFNg cells, whereas both P and irrelevant syngeneic tumors grew in controls. Conclusions: Transduction of MCA106 cells with the MuIFNg gene diminished in vivo tumorigenicity in proportion to the amount of IFNg secreted. Immunization with H-IFNg cells elicited a host response characterized by macrophages and CD4+ cells. Long-term tumor-specific memory was seen after immunization with H-IFNg cells.  相似文献   
68.
69.
70.
Nephrotoxicity is a dose-limiting factor in clinical use of cisplatin. The changes in renal haemodynamics were suggested to play a role in cisplatin-induced nephrotoxicity. The aim of the present study was to investigate the effect of modulation of nitric oxide on the severity of cisplatin-induced nephrotoxicity using an experimental rat model. A nitric oxide precursor, L-arginine and an inhibitor of nitric oxide synthase, L-NAME were used. After six days of cisplatin injection, acute nephrotoxicity was demonstrated by a marked increase in serum creatinine and blood urea nitrogen. Histological examination of the kidneys confirmed the occurrence of renal damage. Moreover, cisplatin induced an increase in the level of lipid peroxides and oxidized glutathione and a depletion of reduced glutathione. The activities of the antioxidant enzymes glutathione peroxidase and superoxide dismutase were also lowered. Besides, there was a reduction in the kidney total nitrate/nitrite levels. L-arginine significantly attenuated the oxidative stress and nephrotoxic effect of cisplatin. On the other hand, L-NAME was found to aggravate cisplatin nephrotoxicity. In conclusion, the decrease in the kidney nitric oxide level contributes, at least in part, in the mechanism underlying the nephrotoxicity of cisplatin. Furthermore, L-arginine shows nephroprotective effects and might be useful in improving the therapeutic index of cisplatin.  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