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   5911篇
  免费   520篇
  国内免费   47篇
耳鼻咽喉   105篇
儿科学   288篇
妇产科学   225篇
基础医学   696篇
口腔科学   81篇
临床医学   604篇
内科学   1050篇
皮肤病学   125篇
神经病学   418篇
特种医学   304篇
外科学   612篇
综合类   372篇
一般理论   2篇
预防医学   485篇
眼科学   109篇
药学   401篇
中国医学   79篇
肿瘤学   522篇
  2021年   72篇
  2020年   60篇
  2019年   72篇
  2018年   91篇
  2017年   81篇
  2016年   112篇
  2015年   123篇
  2014年   164篇
  2013年   231篇
  2012年   311篇
  2011年   350篇
  2010年   227篇
  2009年   201篇
  2008年   346篇
  2007年   372篇
  2006年   305篇
  2005年   305篇
  2004年   257篇
  2003年   262篇
  2002年   229篇
  2001年   190篇
  2000年   162篇
  1999年   157篇
  1998年   79篇
  1997年   84篇
  1996年   61篇
  1995年   70篇
  1994年   52篇
  1993年   57篇
  1992年   100篇
  1991年   146篇
  1990年   99篇
  1989年   88篇
  1988年   89篇
  1987年   81篇
  1986年   61篇
  1985年   67篇
  1984年   58篇
  1983年   44篇
  1982年   40篇
  1981年   43篇
  1980年   34篇
  1979年   45篇
  1978年   41篇
  1977年   31篇
  1976年   20篇
  1975年   29篇
  1974年   21篇
  1973年   30篇
  1972年   39篇
排序方式: 共有6478条查询结果,搜索用时 20 毫秒
1.
2.
Interleukin (IL)-13 plays a central role in asthma pathogenesis by binding to the IL-13 receptor, which is a heterodimer composed of the IL-13 receptor alpha1 subunit (IL-13Ralpha1) and IL-4Ralpha. The genetic diversity at the IL-13Ralpha1 gene (IL13RA1) locus on chromosome Xq24 was characterised and the association of identified polymorphisms with asthma and atopy phenotypes examined. The promoter and coding region of IL13RA1 were screened for common genetic variants, and polymorphisms found were genotyped in a large cohort of 341 asthmatic Caucasian families (each containing at least two asthmatic siblings) and 182 nonasthmatic control subjects. Genetic association was determined using case-control and transmission disequilibrium test analyses. Two common polymorphisms were identified, a newly found thymidine (T) to guanine (G) transition of nucleotide -281 (-281T>G) single nucleotide polymorphism in the IL13RA1 promoter and the previously described 1365A>G variant in the IL13RA1 proximal 3' untranslated region. No significant association of either -281T>G or 1365A>G with risk of asthma or atopy phenotypes was found, apart from a suggestive association between the IL13RA1 -281T/1365A haplotype and raised total serum immunoglobulin E levels in adult female asthmatics. These findings indicate that the interleukin-13 receptor alpha1 subunit gene -281T>G and 1365A>G polymorphisms do not contribute to asthma susceptibility or severity, although the interleukin-13 receptor alpha1 subunit gene locus might be involved in the control of immunoglobulin E production.  相似文献   
3.
Metabolism is one of the major determinants for age-related changes in susceptibility to chemicals. Aldehydes are highly reactive molecules present in the environment that also can be produced during biotransformation of xenobiotics and endogenous metabolism. Although the lung is a major target for aldehyde toxicity, early development of aldehyde dehydrogenases (ALDHs) in lung has been poorly studied. The expression of ALDH in liver and lung across ages (postnatal day 1, 8, 22, and 60) was investigated in Wistar-Han rats. In adult, the majority of hepatic ALDH activity was found in mitochondria, while cytosolic ALDH activity was the highest contributor in lung. Total aldehyde oxidation capability in liver increases with age, but stays constant in lung. These overall developmental profiles of ALDH expression in a tissue appear to be determined by the different composition of ALDH isoforms within the tissue and their independent temporal and tissue-specific development. ALDH2 showed the most notable tissue-specific development. Hepatic ALDH2 was increased with age, while the pulmonary form did not. ALDH1 was at its maximum value at postnatal day 1 (PND1) and decreased thereafter both in liver and lung. ALDH3 increased with age in liver and lung, although ALDH3A1 was only detectible in lung. Collectively, the present study indicates that, in the case of aldehyde exposure, the in vivo responses would be tissue and age dependent.  相似文献   
4.
In an open, randomized cross-over study in 124 patients, we compared the efficacy, safety and patient preference of oral and subcutaneous sum triptan in the acute treatment of migraine. Patients were treated for 3 attacks or 3 months and then crossed over. Primary clinical efficacy was defined as a reduction in headache severity on a four-point self-rating scale from severe (3) or moderate (2) to mild (1) or none (0), or mild (1) to none (0). Efficacy was evaluated 2 h after the administration of subcutaneous and 4h after the administration of oral sumatriptan. Subcutaneous sumatriptan was significantly more effective than oral sumatriptan in relieving headache (over all three attacks 78% vs 61% improvement), improving clinical disability (55% vs 41 % improvement) and relieving nausea (69% vs 53%), vomiting (72% vs 32%) and phono- or photophobia (67% vs 49%). Median time to recurrence was shorter after subcutaneous (12.5 h) than after oral sumatriptan (18 h); the number of patients experiencing a recurrence was similar Patients reported more adverse events after subcutaneous sumatriptan (1.32 per attack) than after the oral form (0.85 per attack), but all adverse events were mild to moderate in intensity and of short duration. Patient opinion was more often positive after subcutaneous sumatriptan. These results may be useful in counselling patients to choose between the available marketed formulations of sumatriptan.  相似文献   
5.
6.
Non-union of the scaphoid: Russe graft vs Herbert screw   总被引:2,自引:0,他引:2  
The results of treatment in 50 consecutive patients with established non-union of the scaphoid are presented. All patients were treated under the care of a single consultant, for the same indications. Russe bone graft is compared with wedge bone graft plus Herbert screw fixation, in terms of union and function. Overall, a higher success rate was obtained by wedge graft plus Herbert screw, and a significantly better range of movement. However, Russe bone graft appears equally satisfactory for fibrous non-union.  相似文献   
7.
8.
Summary We enrolled children with acute lymphoblastic leukemia (ALL) in a Pediatric Oncology Group (POG) pilot study to monitor erythrocyte (RBC) methotrexate (MTX) and folate (F) levels before and during treatment. The mean value for RBCF at diagnosis was 0.86±0.46 nmol/ml RBC in the 214 patients who achieved remission and 1.21±0.74 nmol/ml RBC in the 10 patients who did not (P=0.020). Folate levels tended to increase during remission induction, but they dropped following an intensive consolidation with methotrexate to levels that were sustained throughout chemotherapy treatment. Methotrexate levels reached mean values of approximately 0.15 nmol/ml RBC at the end of an intensive methotrexate consolidation, then fell to levels that were sustained throughout maintenance therapy. There was a weak correlation between improved event-free survival and higher RBCMTX levels after consolidation, but no correlation was found between improved survival and the level of RBCMTX or RBCF during maintenance therapy. A larger study with more complete data is needed to determine whether RBCMTX or RBCF might be useful in predicting event-free survival in patients with ALL.This work was supported in part by grants from the National Cancer Institute and the National Institute of Health (CA-30969, CA-28476, CA29139, CA-159-89, and CA-33587)  相似文献   
9.
NFS60, a murine leukemia cell line, responds to both interleukin 3 and 6 by proliferating, apparently by different signal transduction pathways. Although stimulation by both cytokines increases the uptake of 3H-arachidonic acid, the response to IL-6 was much faster. Furthermore, the effect of various arachidonic acid metabolites on the response to cytokine was different. PGE2 inhibited IL-6-induced proliferation and potentiated the response to IL-3. Additionally the G proteins which coupled the IL-3 and IL-6 receptor to the proliferative response are probably different, based on the ability of cholera toxin to inhibit the IL-3 but not the IL-6 response. These data are evidence of two pathways of signal transduction.  相似文献   
10.
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