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   2262篇
  免费   142篇
  国内免费   6篇
耳鼻咽喉   40篇
儿科学   72篇
妇产科学   52篇
基础医学   429篇
口腔科学   16篇
临床医学   246篇
内科学   484篇
皮肤病学   54篇
神经病学   203篇
特种医学   86篇
外科学   234篇
综合类   8篇
一般理论   2篇
预防医学   158篇
眼科学   22篇
药学   129篇
中国医学   8篇
肿瘤学   167篇
  2023年   10篇
  2022年   28篇
  2021年   30篇
  2020年   27篇
  2019年   50篇
  2018年   65篇
  2017年   33篇
  2016年   42篇
  2015年   37篇
  2014年   67篇
  2013年   82篇
  2012年   149篇
  2011年   186篇
  2010年   92篇
  2009年   98篇
  2008年   177篇
  2007年   148篇
  2006年   145篇
  2005年   150篇
  2004年   132篇
  2003年   126篇
  2002年   149篇
  2001年   46篇
  2000年   49篇
  1999年   45篇
  1998年   29篇
  1997年   19篇
  1996年   15篇
  1995年   15篇
  1994年   12篇
  1993年   14篇
  1992年   15篇
  1991年   24篇
  1989年   12篇
  1988年   9篇
  1987年   6篇
  1986年   6篇
  1985年   7篇
  1984年   3篇
  1983年   4篇
  1982年   5篇
  1980年   3篇
  1979年   9篇
  1978年   4篇
  1974年   7篇
  1973年   3篇
  1972年   3篇
  1971年   3篇
  1969年   4篇
  1968年   5篇
排序方式: 共有2410条查询结果,搜索用时 15 毫秒
1.
2.
3.
Evaluative composite measurement scales (CMS) are increasingly used in medicine to measure complex constructs in the absence of a reference criterion or ‘gold standard’. However, the level of measurement provided by these instruments has usually been given little attention. This paper explores the influence of the characteristics of the item set and weighting on the level of measurment of an evaluative CMS. The approach is illustrated with an application to the scoring system of the Nottingham Health Profile. Simulations are provided to indicate when the composite score of item responses, on an ordinal or pass—fail scale, could be considered to achieve the properties of an interval scale.  相似文献   
4.
Lipopolysaccharide (LPS) preconditioning provides neuroprotection against subsequent cerebral ischemic injury. Tumor necrosis factor-alpha (TNFalpha) is protective in LPS-induced preconditioning yet exacerbates neuronal injury in ischemia. Here, we define dual roles of TNFalpha in LPS-induced ischemic tolerance in a murine model of stroke and in primary neuronal cultures in vitro, and show that the cytotoxic effects of TNFalpha are attenuated by LPS preconditioning. We show that LPS preconditioning significantly increases circulating levels of TNFalpha before middle cerebral artery occlusion in mice and show that TNFalpha is required to establish subsequent neuroprotection against ischemia, as mice lacking TNFalpha are not protected from ischemic injury by LPS preconditioning. After stroke, LPS preconditioned mice have a significant reduction in the levels of TNFalpha (approximately threefold) and the proximal TNFalpha signaling molecules, neuronal TNF-receptor 1 (TNFR1), and TNFR-associated death domain (TRADD). Soluble TNFR1 (s-TNFR1) levels were significantly increased after stroke in LPS-preconditioned mice (approximately 2.5-fold), which may neutralize the effect of TNFalpha and reduce TNFalpha-mediated injury in ischemia. Importantly, LPS-preconditioned mice show marked resistance to brain injury caused by intracerebral administration of exogenous TNFalpha after stroke. We establish an in vitro model of LPS preconditioning in primary cortical neuronal cultures and show that LPS preconditioning causes significant protection against injurious TNFalpha in the setting of ischemia. Our studies suggest that TNFalpha is a twin-edged sword in the setting of stroke: TNFalpha upregulation is needed to establish LPS-induced tolerance before ischemia, whereas suppression of TNFalpha signaling during ischemia confers neuroprotection after LPS preconditioning.  相似文献   
5.
Both celiac disease and inflammatory bowel disease (IBD) are characterized by chronic diarrhea and the presence of distinct (auto)antibodies. In the present study we wanted to determine the prevalence of serological markers for inflammatory bowel disease, i.e., perinuclear antineutrophil cytoplasmic antibodies (pANCA) and/or anti-Saccharomyces cerevisiae antibodies (ASCA), in 37 patients with biopsy-confirmed celiac disease (Marsh IIIb/c). The majority of the patients was positive for IgA (auto)antibodies typically associated with celiac disease, i.e., antiendomysium antibodies (EMA) (86.5%), antigliadin antibodies (AGA) (73%), and antirecombinant human tissue transglutaminase antibodies (rh-tTGA) (86.5%). Four patients with selective IgA deficiency could be identified by analyzing EMA, AGA, and rh-tTGA for the IgG isotype. The prevalence of pANCA and ASCA, markers that are used for IBD, was unexpectedly high in our cohort of patients with celiac disease: 8 patients were positive for pANCA (IgG) and 16 patients were positive for ASCA (IgG and/or IgA). These results indicate that the presence of pANCA or ASCA in the serum of patients with chronic diarrhea does not exclude celiac disease. A prospective study is required to determine whether pANCA and/or ASCA identify patients at risk for developing secondary autoimmune disease.  相似文献   
6.
The Rho proteins are Ras-related guanosine triphosphatases (GTPases) that function in cytoskeletal reorganization, cell migration, and stress fiber and focal adhesion formation. Overexpression of RhoC enhances the ability of melanoma cells to exit the blood and colonize the lungs. However, in vivo confirmation of RhoC's role in metastasis has awaited a RhoC-deficient mouse model. Here we report the generation of RhoC-deficient mice and show that RhoC is dispensable for embryonic and post-natal development. We demonstrate that loss of RhoC does not affect tumor development but decreases tumor cell motility and metastatic cell survival leading to a drastic inhibition of metastasis.  相似文献   
7.
BACKGROUND: Up to 20 million persons are infected with the human retroviruses human T-lymphotropic virus (HTLV)-I and HTLV-II globally. Most data on the seroprevalence of HTLV-I and HTLV-II in Europe are from studies of low-risk blood donors or high-risk injection drug users (IDUs). Little is known about the general population. METHODS: A prospective anonymous study of HTLV-I and HTLV-II seroprevalence among 234,078 pregnant women in Belgium, France, Germany, Italy, Portugal, Spain, and the United Kingdom was conducted. Maternal antibody status was determined by standard methods using sera obtained for routine antenatal infection screens or eluted from infant heel prick dried blood spots obtained for routine neonatal metabolic screens. RESULTS: Anti-HTLV-I/II antibodies were detected and confirmed in 96 pregnant women (4.4 per 10,000, 95% confidence interval [CI]: 3.5-5.2). Of these, 73 were anti-HTLV-I, 17 were anti-HTLV-II, and 6 were specifically anti-HTLV but untyped. The seroprevalence ranged from 0.7 per 10,000 in Germany to 11.5 per 10,000 in France. CONCLUSIONS: Pregnant women better reflect the general population than blood donors or IDUs. The seroprevalence of HTLV-I and HTLV-II in Western Europe is 6-fold higher among pregnant women (4.4 per 10,000) than among blood donors (0.07 per 10,000). These data provide a robust baseline against which changes in HTLV-I and HTLV-II seroprevalence in Europe can be measured.  相似文献   
8.
9.
The increasing number of mucocele cases treated by the authors during the past ten years coincide with the expansion of functional endoscopic sinus surgery (FESS). The aim of this study is to evaluate the iatrogenic characteristics of this surgery by analysing the locations, time of development and the potential pathogenic factors of sinus mucoceles. Forty-two sinus mucoceles were operated in our department. These mucoceles were most frequently found in the anterior ethmoido-frontal system. Eleven patients had a history of endonasal ethmoidectomy mainly due to nasal polyposis. The time of mucocele formation after initial FESS (< 22 months) seems to be shorter than after exonasal sinus surgery or trauma (< 10 years). Endoscopic and CT-scan revealed different types of sinus obstruction findings: nasofrontal duct occlusion due to a fibrosis and osteogenic scar tissue process, or anterior ethmoid synechia in the case of ethmoido-frontal sinus mucocele, uncinate process fragment or scar tissue duct occlusion as far as maxillary sinus mucocele were concerned. We conclude that there seems to be a correlation between the expansion of FESS and the increasing number of mucocele cases. However, in this context it has to taken into consideration, that our department treats a considerable number of sinus pathology. Anterior ethmoid seems to be a favourable area for sinus mucocele formation. In order to prevent mucocele, it is essential to carry out FESS with great precaution. If endonasal surgery is performed, particularly in the anterior ethmoid, a close endoscopic follow-up, completed by radiological examinations, where necessary, must be ensured.  相似文献   
10.
PURPOSE: Arsenic trioxide (ATO) is capable of inducing a high hematologic response rate in patients with relapsed acute promyelocytic leukemia (APL). Preclinical observations have indicated that all-trans-retinoic acid (ATRA) may strongly enhance the response to ATO. PATIENTS AND METHODS: Between 1998 and 2001, we conducted a randomized study of ATO alone versus ATO plus ATRA in 20 patients with relapsed APL, all previously treated with ATRA-containing chemotherapy. The primary objective was to demonstrate a significant reduction in the time necessary to obtain a complete remission (CR) in the ATO/ATRA group compared with the ATO group. Secondary objectives were safety and molecular response. RESULTS: The CR rate after one ATO with or without ATRA induction cycle was 80%. Clinical and pharmacokinetic observations indicated that the main mechanism of action of ATO in vivo was the induction of APL cell differentiation. Hematologic and molecular response, time necessary to reach CR, and outcome were comparable in both treatment groups. Of 16 CR patients, three patients who reached a molecular remission after one induction cycle had all received chemotherapy for a treatment-induced hyperleukocytosis. Three additional patients who received further additional ATO with or without ATRA cycles converted later to molecular negativity. CONCLUSION: ATRA did not seem to significantly improve the response to ATO in patients relapsing from APL. Other potential combinations, including ATO plus chemotherapy, have to be tested.  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