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   1797篇
  免费   131篇
  国内免费   6篇
耳鼻咽喉   10篇
儿科学   48篇
妇产科学   37篇
基础医学   241篇
口腔科学   38篇
临床医学   187篇
内科学   290篇
皮肤病学   28篇
神经病学   156篇
特种医学   102篇
外科学   320篇
综合类   32篇
一般理论   2篇
预防医学   180篇
眼科学   2篇
药学   121篇
中国医学   5篇
肿瘤学   135篇
  2023年   4篇
  2022年   11篇
  2021年   28篇
  2020年   30篇
  2019年   37篇
  2018年   39篇
  2017年   37篇
  2016年   29篇
  2015年   36篇
  2014年   37篇
  2013年   80篇
  2012年   88篇
  2011年   83篇
  2010年   73篇
  2009年   70篇
  2008年   90篇
  2007年   73篇
  2006年   85篇
  2005年   86篇
  2004年   98篇
  2003年   64篇
  2002年   44篇
  2001年   45篇
  2000年   48篇
  1999年   56篇
  1998年   42篇
  1997年   24篇
  1996年   35篇
  1995年   20篇
  1994年   26篇
  1993年   25篇
  1992年   28篇
  1991年   38篇
  1990年   33篇
  1989年   34篇
  1988年   43篇
  1987年   44篇
  1986年   27篇
  1985年   27篇
  1984年   22篇
  1983年   17篇
  1982年   13篇
  1981年   10篇
  1980年   9篇
  1979年   7篇
  1978年   5篇
  1977年   4篇
  1976年   9篇
  1975年   4篇
  1968年   3篇
排序方式: 共有1934条查询结果,搜索用时 15 毫秒
1.
Whereas there is evidence that interpersonal communication, or conversation, influences predictors of alcohol consumption, the role of involvement in conversation effects remains unclear. This study explored how three aspects of involvement (topical relevance, or how relevant the topic of alcohol is; conversational relevance, or how relevant a conversation about alcohol is; and conversational effort, or how much effort people put into such a conversation), influence conversation effects. After assessing topical relevance, 46 same-sex dyads were requested to talk about the negative consequences of heavy drinking. Within each dyad, one participant was asked to take on an active talking role and the other participant a passive listening role. Next, conversational relevance, effort, and predictors of heavy drinking were measured. Results showed that participants who drank more alcohol found the topic of heavy drinking more relevant. This topical relevance increased conversational relevance and conversational effort. Conversational effort further increased when a talking role was assigned. Furthermore, participants who put more effort in the conversation and found it more relevant had more positive norms, identified more strongly with alcohol, and had higher intentions to drink. These findings suggest that more involvement in an alcohol-related conversation does not always lead to desirable outcomes.  相似文献   
2.
3.
In May 2017, the Health and Environmental Sciences Institute's Genetic Toxicology Technical Committee hosted a workshop to discuss whether mode of action (MOA) investigation is enhanced through the application of the adverse outcome pathway (AOP) framework. As AOPs are a relatively new approach in genetic toxicology, this report describes how AOPs could be harnessed to advance MOA analysis of genotoxicity pathways using five example case studies. Each of these genetic toxicology AOPs proposed for further development includes the relevant molecular initiating events, key events, and adverse outcomes (AOs), identification and/or further development of the appropriate assays to link an agent to these events, and discussion regarding the biological plausibility of the proposed AOP. A key difference between these proposed genetic toxicology AOPs versus traditional AOPs is that the AO is a genetic toxicology endpoint of potential significance in risk characterization, in contrast to an adverse state of an organism or a population. The first two detailed case studies describe provisional AOPs for aurora kinase inhibition and tubulin binding, leading to the common AO of aneuploidy. The remaining three case studies highlight provisional AOPs that lead to chromosome breakage or mutation via indirect DNA interaction (inhibition of topoisomerase II, production of cellular reactive oxygen species, and inhibition of DNA synthesis). These case studies serve as starting points for genotoxicity AOPs that could ultimately be published and utilized by the broader toxicology community and illustrate the practical considerations and evidence required to formalize such AOPs so that they may be applied to genetic toxicity evaluation schemes. Environ. Mol. Mutagen. 61:114–134, 2020. © 2019 Wiley Periodicals, Inc.  相似文献   
4.
Multidisciplinary evaluation of rat renal cell carcinoma   总被引:1,自引:0,他引:1  
The rat renal cell carcinoma system as described by deVere White and Olsson in 1980 is used widely as a model for its human counterpart. The tumor arose spontaneously in a male Wistar Lewis rat and its behaviour has been shown to be stable during multiple passages. We have compared this tumor with the human renal cell carcinoma using a multidisciplinary approach. Light microscopy and electron microscopy showed a great resemblance of this rat tumor to a human renal cell carcinoma of the clear cell type with the ultrastructural presence of desmosomes. With the use of tissue specific antibodies against intermediate filament proteins, it could be shown that their expression is comparable to human renal cell carcinoma, i.e. coexpression of vimentin and different cytokeratins in the tumor cells. The cells could also be shown to contain cytokeratin 18. An aneuploid cell population in the tumor, expressing both vimentin and keratin, could be characterized by DNA flow cytometry in double labeling experiments. Comparison of normal and malignant rat kidney tissue by Northern blot analysis revealed increased levels of vimentin mRNA. In conclusion, this tumor model seems to have several histological and biological properties in common with the human renal tumor.  相似文献   
5.
BACKGROUND: Neovascularisation at the sapheno-femoral junction (SFJ) ligation site in the groin may occur within one year after great saphenous vein (GSV) surgery. Several anatomical and prosthetic barrier techniques have been proposed to prevent this evolution. OBJECTIVE: A prospective study examined whether closing the cribriform fascia could reduce the incidence of postoperative neovascularisation in the groin. PATIENTS AND METHODS: Patients with primary varicose veins and incompetence at the level of the SFJ were included. After SFJ ligation in 235 limbs of 193 patients an anatomical barrier was constructed by closing the cribriform fascia. Postoperative duplex scanning was performed after 2 and 12 months. Results were compared with historical control groups in which either a silicone patch saphenoplasty or no barrier technique had been performed. RESULTS: After one year, 10 limbs had developed recurrent thigh varicose veins and duplex scan showed neovascularisation at the SFJ ligation site in 15 of 223 re-examined limbs (6.7%). This was comparable to the group of 191 limbs with silicone patch saphenoplasty (5.2%) (P=0.526) and superior to the group of 189 limbs without barrier (14.8%) (P<0.01). CONCLUSION: Interposition of an anatomical barrier by closing the cribriform fascia after SFJ ligation reduced ultrasound detected neovascularisation at the SFJ after one year. In primary varicose vein operations application of an anatomical barrier technique (without prosthetic patch) is an alternative option to prevent postoperative neovascularisation.  相似文献   
6.
Summary This paper reports a case of fatal meningitis caused byFusobacterium necrophorum subsp.necrophorum in a previously healthy five-year-old child. The organism was isolated in pure culture from the cerebrospinal fluid and from intracranial pus obtained at autopsy. The role ofF. necrophorum in the development of meningitis is reaffirmed and its isolation and identification are discussed. The clinical presentation of the present case resembles the previously published reports and highlights the poor prognosis in spite of appropriate antibiotic treatment.
Meningitis durch Fusobacterium necrophorum Subspecies necrophorum. Fallbeschreibung und Literaturübersicht
Zusammenfassung In der vorliegenden Arbeit wird der Fall eines vorher gesunden fünfjährigen Kindes beschrieben, das an einer Meningitis, verursacht durchFusobacterium necrophorum Subspeciesnecrophorum, verstorben ist. Der Keim wurde aus Liquor und autoptisch entnommenem intrakranialem Eiter in Reinkultur isoliert. Die Rolle vonFusobacterium necrophorum als Meningitiserreger und die Techniken zur Isolierung und Identifikation des Keimes werden diskutiert. Der vorgestellte Fall ähnelt früher publizierten Beschreibungen und verdeutlicht die schlechte Prognose der Infektion auch bei adäquater Antibiotika-Therapie.
  相似文献   
7.
8.
9.
In activated murine B lymphocytes, immunoglobulin class switch recombination occurs as a highly regulated process which is targeted to distinct switch regions. Here we present first evidence that in human B lymphocytes, switch recombination is targeted to distinct switch regions as well. In a panel of clonally unrelated IgG1-expressing human B cells, immortalized by Epstein-Barr virus (EBV) transformation, seven out of nine cells show switch recombination between Sμ and Sγ1 on both alleles, the active and inactive one. The remaining cells show no switch recombination on the inactive IgH locus. The very strong correlation of switch recombination on both alleles of IgG1-expressing cells proves that class switch recombination to IgG1 is not random but directed in human B lymphocytes.  相似文献   
10.
AIMS: The degradation of the extracellular matrix is intrinsic to the invasion and progression of cancer. Matrix metalloproteinase (MMP)-2 and -9 and their natural inhibitors are involved in this process. The study aims to investigate if plasma MMP-2, -9 and tissue inhibitor of metalloproteinase-1 (TIMP-1) can be useful markers in the diagnosis and prognosis of colorectal cancer (CRC) metastatic liver disease. METHODS: Fifty-seven patients undergoing liver metastasis operation were followed prospectively. ProMMP-2, -9 and TIMP-1 plasma levels were determined by zymography and ELISA, before and after the resection of liver metastases. Data were compared with those of healthy controls (n=51) and primary CRC patients (n=94). The diagnostic and prognostic potential was investigated with ROC-curves and Kaplan-Meier survival analysis. RESULTS: Plasma proMMP-2 levels were lower (P<0.001), and TIMP-1 levels higher (P<0.001) in CRC metastatic liver disease than in healthy controls. If compared to those in primary CRC patients, no differences were found. In ROC-curves, the area under the curve was 0.48 and 0.61 for proMMP-2 and -9, respectively. Plasma proMMP-2, -9 and TIMP-1 levels were unsuitable to predict survival. In both diagnostic and prognostic examinations, CEA proved to be a better marker. In the postoperative follow-up, protracted low levels of proMMP-2 seemed related to disease recurrence. CONCLUSION: The preoperative plasma proMMP-2, -9 and TIMP-1 levels have no potential value as diagnostic or prognostic markers in CRC liver metastatic disease.  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