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   12377篇
  免费   1151篇
  国内免费   8篇
  2022年   73篇
  2021年   159篇
  2020年   93篇
  2019年   124篇
  2018年   169篇
  2017年   136篇
  2016年   244篇
  2015年   420篇
  2014年   454篇
  2013年   560篇
  2012年   753篇
  2011年   735篇
  2010年   513篇
  2009年   444篇
  2008年   713篇
  2007年   676篇
  2006年   655篇
  2005年   702篇
  2004年   685篇
  2003年   657篇
  2002年   659篇
  2001年   115篇
  2000年   93篇
  1999年   153篇
  1998年   198篇
  1997年   123篇
  1996年   132篇
  1995年   126篇
  1994年   123篇
  1993年   116篇
  1992年   105篇
  1991年   89篇
  1990年   101篇
  1989年   87篇
  1988年   87篇
  1987年   89篇
  1986年   86篇
  1985年   119篇
  1984年   141篇
  1983年   118篇
  1982年   139篇
  1981年   145篇
  1980年   147篇
  1979年   80篇
  1978年   93篇
  1977年   84篇
  1976年   72篇
  1975年   77篇
  1974年   94篇
  1973年   84篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
Stress-responsive genes play critical roles in many biological functions that includes apoptosis, survival, differentiation and regeneration. We have identified a novel stress-responsive gene called BRE which interacts with TNF-receptor-1 and blocks the apoptotic effect of TNF-α. BRE enhances tumor growth in vivo and is up-regulated in hepatocellular and esophageal carcinomas. BRE also regulates the ubiquitination of the DNA repair complex BRCC, and the synthesis of steroid hormones. Here, we examined BRE-mRNA in cells after treatments with UV and ionizing radiation (IR). UV and IR treatment alone suppressed BRE-mRNA levels by more than 90% at 24 h, while hydroxyurea, fluorodeoxyuridine, aphidicolin, known inhibitors of S-phase DNA synthesis, had no significant effect. BRE protein expression was unaltered in cells treated with TNF-α, Interleukin-1 and Dexamethasone, while a threefold increase was observed following chorionic gonadotropin exposure. Although BRE plays a regulatory role in many different pathways, yet its expression is apparently under very stringent control.  相似文献   
983.
984.
985.
In seawater fishes, osmotic homeostasis requires uptake of ions and water in the intestine and these processes are governed by the combined trans- and paracellular pathways. The current study examined mRNA expression of two tight junction proteins (claudin-15 and -25b) predominantly expressed in the intestine of Atlantic salmon. We examined the response in pyloric caecae, middle and posterior intestine to seawater challenge, during smoltification and after injection with osmoregulatory hormones. Seawater (SW) transfer elevated levels of claudin-15 and -25b while no change was induced throughout the smolt stage. In freshwater, cortisol and growth hormone inhibited claudin-15 expression in the two anterior segments. Claudin-25b was elevated in all intestinal segments by growth hormone, while cortisol had an inhibitory effect. In seawater, prolactin and cortisol inhibited claudin expression. The data suggest that claudin expression is involved in the reorganisation of intestinal epithelium and possibly change paracellular permeability during SW acclimation. The lack of preparatory change during smoltification suggests that this process is not completed during smolt development. The effects of the tested hormones cannot explain the sum of changes induced by salinity, which, like the smoltification data, suggests the importance of additional factors and possibly contact with the imbibed SW per se.  相似文献   
986.

Background

Vaccination against herpes zoster is being considered in many countries. We conducted a multicentre prospective study to describe the impact of herpes zoster and postherpetic neuralgia on health-related quality of life.

Methods

From October 2005 to July 2006, 261 outpatients aged 50 years or older with herpes zoster were recruited from the clinical practices of 83 physicians within 14 days after rash onset. The Zoster Brief Pain Inventory was used to measure severity of pain and interference with activities of daily living because of pain. The EuroQol EQ-5D assessment tool was used to measure quality of life. These outcomes were assessed at recruitment and on days 7, 14, 21, 30, 60, 90, 120, 150 and 180 following recruitment.

Results

Acute herpes zoster interfered in all health domains, especially sleep (64% of participants), enjoyment of life (58%) and general activities (53%). The median duration of pain was 32.5 days. The median duration of interference with activities of daily living because of pain varied between 27 and 30 days. Overall, 24% of the participants had postherpetic neuralgia (pain for more than 90 days after rash onset). Anxiety and depression, enjoyment of life, mood and sleep were most frequently affected during the postherpetic neuralgia period. The mean EQ-5D score was 0.59 at enrolment and remained at 0.67 at all follow-up points among participants who reported clinically significant pain.

Interpretation

These data support the need for preventive strategies and additional early intervention to reduce the burden of herpes zoster and postherpetic neuralgia.Herpes zoster, which is characterized by dermatomal pain and vesicular rash,1,2 results from reactivation of the varicella-zoster virus.3,4 The average lifetime risk of herpes zoster in developed countries is estimated to be about 30%57 and increases with increasing life expectancy. The most common complication of herpes zoster, and one of the most challenging to treat, is postherpetic neuralgia, a painful condition often defined as pain persisting for more than 90 days after rash onset.8 According to this definition, postherpetic neuralgia is estimated to occur in 8%–27% of people with herpes zoster overall.914 The risk of postherpetic neuralgia increases markedly with age.15The Shingles Prevention Study, a randomized double-blind placebo-controlled trial, showed that a live-attenuated varicella-zoster virus vaccine was safe and effective in preventing herpes zoster and postherpetic neuralgia among people 60 years of age and older.13 Given these promising results, policy-makers and clinicians are being asked to make recommendations regarding the use and funding of the herpes zoster vaccine. To do this, evidence on the burden of herpes zoster from the patient’s perspective is required. The only data available on the impact of herpes zoster on health-related quality of life comes from two short-term studies.16,17 Clinical reports and cross-sectional surveys1820 have also suggested that postherpetic neuralgia can profoundly impair quality of life. However, no study followed a cohort of patients with newly diagnosed herpes zoster for a sufficient period to assess postherpetic neuralgia and describe the associated impact on quality of life.We undertook a multicentre prospective study to describe the impact of herpes zoster and postherpetic neuralgia on health-related quality of life.  相似文献   
987.
988.
989.
Both local and landscape-scale habitat variables influence the abundance of wetland breeding birds. Few studies, however, simultaneously assess the effects of habitat variables at multiple spatial scales or consider effects on reproductive success. Therefore, we examined the effects of wetland and landscape-scale habitat variables on the abundance of nine breeding bird species and the effects of nest, wetland, or landscape-scale habitat variables on the nest success, clutch size, or number of fledglings of four species at 15 cattail (Typha sp.)-dominated wetlands in an agricultural region around Peterborough, Ontario, Canada. The abundance of Least Bittern (Ixobrychus exilis), Common Moorhen (Gallinula chloropus), and Marsh Wren (Cistothorus palustris) increased as wetland water depth increased; the abundance of Common Moorhen and Marsh Wren increased as wetland size increased; and the abundance of Marsh Wren increased as the amount of wetland in the surrounding landscape increased. Red-winged Blackbird (Agelaius phoeniceus) nest success decreased as nest cover increased. Clutch sizes were uninfluenced by the habitat variables that we considered. The number of Red-winged Blackbird fledglings per successful nest increased as wetland size increased and as the amount of wetland in the surrounding landscape increased. We speculate that food limitation in small wetlands may be responsible for the pattern in Red-winged Blackbird fledging success. The abundance and nest success of Virginia Rail (Rallus limicola) and Sora (Porzana carolina) were uninfluenced by the habitat variables we considered. Future research should consider mate attraction and productivity in relation to local and landscape-scale habitat variables for these and other secretive species. Our study suggests that wetland conservation will be most effective if it considers habitat variables at multiple spatial scales.  相似文献   
990.
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