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   2374803篇
  免费   195103篇
  国内免费   4210篇
耳鼻咽喉   34264篇
儿科学   72752篇
妇产科学   62934篇
基础医学   334882篇
口腔科学   67523篇
临床医学   215530篇
内科学   468593篇
皮肤病学   47936篇
神经病学   200787篇
特种医学   95966篇
外国民族医学   886篇
外科学   360407篇
综合类   56263篇
现状与发展   1篇
一般理论   978篇
预防医学   190616篇
眼科学   55491篇
药学   177541篇
  4篇
中国医学   4366篇
肿瘤学   126396篇
  2018年   24209篇
  2016年   20578篇
  2015年   23279篇
  2014年   33541篇
  2013年   50837篇
  2012年   68746篇
  2011年   72288篇
  2010年   42476篇
  2009年   40867篇
  2008年   68764篇
  2007年   73101篇
  2006年   74002篇
  2005年   72044篇
  2004年   69343篇
  2003年   67020篇
  2002年   66268篇
  2001年   112452篇
  2000年   116526篇
  1999年   98334篇
  1998年   27860篇
  1997年   25523篇
  1996年   25448篇
  1995年   24611篇
  1994年   23161篇
  1993年   21555篇
  1992年   79389篇
  1991年   76397篇
  1990年   73576篇
  1989年   70844篇
  1988年   65849篇
  1987年   64806篇
  1986年   61338篇
  1985年   58406篇
  1984年   44235篇
  1983年   37666篇
  1982年   22895篇
  1981年   20336篇
  1980年   19034篇
  1979年   41303篇
  1978年   28988篇
  1977年   24348篇
  1976年   22832篇
  1975年   23966篇
  1974年   29640篇
  1973年   28044篇
  1972年   26228篇
  1971年   24153篇
  1970年   22752篇
  1969年   21087篇
  1968年   19135篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Our research was aimed at establishing if and how selenium (Se) ion, N-acetylcysteine (NAC), sodium salt of monoketocholic acid (MKH) and superoxide-dismutase (SOD), administered in the experimental animal model, could affect the possible cytotoxicity associated with anthracycline-based combined chemotherapy with doxorubicin, vincristine and prednisolone (DVP). The following biochemical parameters were investigated: the extent of lipid peroxidation (LPx), and the activity of peroxidase (Px), catalase (CAT), glutathione-peroxidase (GSHPx), and xanthine-oxidase (XOD). A statistical increase in LPx activity was obtained by SOD, MKH, DVPSe and DVPMKH. All chemotherapeutic agents reduced Px activity in a statistically significant manner. There was no statistical significance for the results regarding the effects of the administered substances on GSHPx activity. The results for DVP, SOD, MKH, DVPSOD, DVPSe and DVPMKH showed reduced XOD activity which was statistically significant, which was lowest in the case of MKH, while NAC and Se reduced the activity of this enzyme but statistically non significant. NAC, Se, DVP, MKH and DVPMKH caused a reduction in CAT activity, while DVPSOD and DVPSe caused an increase of the latter.  相似文献   
962.
Because of the wide inter individual variability between patients and their marked differences in drug response, one of the major issues that arises is adapting the therapy in question to the particular patient. In hospital, it is possible to vary the conditions of intravenous (i.v.) drug delivery by means of short infusions repeated at certain intervals. In this study, review of this process has been presented, and a therapeutic method described. It essentially consists of two stages. The first concerns the time of the first infusion, and the course of drug elimination: from two analyses of the drug concentrations in the blood made at two different times, the pharmacokinetic parameters of the patient are determined. Stage 2 consists of repeated short infusions and the therapy is adapted to the particular patient by varying the conditions involved. Thus, either the amount of the dose based on the rate of infusion or the time interval between the repeated infusions are varied. In order to reach a general solution, master curves are built by using dimensionless numbers as co-ordinates, such as time expressed in terms of the half-life t0.5 of the drug, and the drug concentration at the peaks defined as a fraction of the first unchanged peak concentration.  相似文献   
963.
964.
965.
966.
We targeted the MVNP gene to the OCL lineage in transgenic mice. These mice developed abnormal OCLs and bone lesions similar to those found in Paget's patients. These results show that persistent expression of MVNP in OCLs can induce pagetic-like bone lesions in vivo. INTRODUCTION: Paget's disease (PD) of bone is the second most common bone disease. Both genetic and viral factors have been implicated in its pathogenesis, but their exact roles in vivo are unclear. We previously reported that transfection of normal human osteoclast (OCL) precursors with the measles virus nucleocapsid (MVNP) or measles virus (MV) infection of bone marrow cells from transgenic mice expressing a MV receptor results in formation of pagetic-like OCLs. MATERIALS AND METHODS: Based on these in vitro studies, we determined if the MVNP gene from either an Edmonston-related strain of MV or a MVNP gene sequence derived from a patient with PD (P-MVNP), when targeted to cells in the OCL lineage of transgenic mice with the TRACP promoter (TRACP/MVNP mice), induced changes in bone similar to those found in PD. RESULTS: Bone marrow culture studies and histomorphometric analysis of bones from these mice showed that their OCLs displayed many of the features of pagetic OCLs and that they developed bone lesions that were similar to those in patients with PD. Furthermore, IL-6 seemed to be required for the development of the pagetic phenotype in OCLs from TRACP/MVNP mice. CONCLUSIONS: These results show that persistent expression of the MVNP gene in cells of the OCL lineage can induce pagetic-like bone lesions in vivo.  相似文献   
967.
968.
969.
970.
BACKGROUND: Exposure to a high level of house dust mite allergens (HDMAs) is considered as a risk factor for HDM sensitization and development of asthma in genetically disposed people. Mattresses are one of the most important sources of HDMA in people's living environment. OBJECTIVE: The aim of this study was to evaluate the association between mattress characteristics and HDMA concentrations on mattresses. METHODS: Dust samples of mattress surfaces were taken to evaluate the level of Der p 1 allergen. All participants filled in a questionnaire about the type of mattress, the type of covering (upper layer) of the mattress, dwelling characteristics and cleaning habits. Humidity and temperature of the bedroom were measured at the time of dust sampling. RESULTS: One hundred and sixty-eight questionnaires were filled in. Synthetic upper layer of the mattress was associated with a higher level of Der p 1 compared with cotton upper layer (2.6 vs. 0.8 microg/g Der p 1). Moreover, higher relative humidity (RH) was associated with significant higher concentrations and density of Der p 1. CONCLUSIONS: Two factors were associated with lower levels of Der p 1 found on mattresses, namely: a cotton upper layer of the mattress compared with a layer of synthetic material and lower RH at the time of sampling. As far as we know, the association between type of upper layer and concentration of Der p 1 has not been described before and could lead to the formulation of practical advices in order to reduce HDMA concentrations on mattresses.  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