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   261篇
  免费   15篇
  276篇
  2023年   1篇
  2022年   8篇
  2021年   6篇
  2020年   5篇
  2019年   6篇
  2018年   1篇
  2017年   4篇
  2016年   8篇
  2015年   17篇
  2014年   11篇
  2013年   22篇
  2012年   17篇
  2011年   19篇
  2010年   13篇
  2009年   6篇
  2008年   12篇
  2007年   14篇
  2006年   11篇
  2005年   9篇
  2004年   15篇
  2003年   13篇
  2002年   8篇
  2001年   5篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1992年   5篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1982年   2篇
  1981年   2篇
  1980年   3篇
  1979年   1篇
  1975年   6篇
  1974年   1篇
  1972年   2篇
  1971年   2篇
  1970年   1篇
  1966年   1篇
  1961年   1篇
排序方式: 共有276条查询结果,搜索用时 0 毫秒
41.
42.
Elaborate cognitive skills arose independently in different taxonomic groups. Self-recognition is conventionally identified by the understanding that one’s own mirror reflection does not represent another individual but oneself, which has never been proven in any elasmobranch species to date. Manta rays have a high encephalization quotient, similar to those species that have passed the mirror self-recognition test, and possess the largest brain of all fish species. In this study, mirror exposure experiments were conducted on two captive giant manta rays to document their response to their mirror image. The manta rays did not show signs of social interaction with their mirror image. However, frequent unusual and repetitive movements in front of the mirror suggested contingency checking; in addition, unusual self-directed behaviors could be identified when the manta rays were exposed to the mirror. The present study shows evidence for behavioral responses to a mirror that are prerequisite of self-awareness and which has been used to confirm self-recognition in apes.  相似文献   
43.
The antibody crystallizable fragment (Fc) is recognized by effector proteins as part of the immune system. Pathogens produce proteins that bind Fc in order to subvert or evade the immune response. The structural characterization of the determinants of Fc–protein association is essential to improve our understanding of the immune system at the molecular level and to develop new therapeutic agents. Furthermore, Fc‐binding peptides and proteins are frequently used to purify therapeutic antibodies. Although several structures of Fc–protein complexes are available, numerous others have not yet been determined. Protein–protein docking could be used to investigate Fc–protein complexes; however, improved approaches are necessary to efficiently model such cases. In this study, a docking‐based structural bioinformatics approach is developed for predicting the structures of Fc–protein complexes. Based on the available set of X‐ray structures of Fc–protein complexes, three regions of the Fc, loosely corresponding to three turns within the structure, were defined as containing the essential features for protein recognition and used as restraints to filter the initial docking search. Rescoring the filtered poses with an optimal scoring strategy provided a success rate of approximately 80% of the test cases examined within the top ranked 20 poses, compared to approximately 20% by the initial unrestrained docking. The developed docking protocol provides a significant improvement over the initial unrestrained docking and will be valuable for predicting the structures of currently undetermined Fc–protein complexes, as well as in the design of peptides and proteins that target Fc.  相似文献   
44.
45.
46.
Mouse embryo imaging is conventionally carried out on ex vivo embryos excised from the amniotic sac, omitting vital structures and abnormalities external to the body. Here, we present an in amnio MR imaging methodology in which the mouse embryo is retained in the amniotic sac and demonstrate how important embryonic structures can be visualised in 3D with high spatial resolution (100 µm/px). To illustrate the utility of in amnio imaging, we subsequently apply the technique to examine abnormal mouse embryos with abdominal wall defects. Mouse embryos at E17.5 were imaged and compared, including three normal phenotype embryos, an abnormal embryo with a clear exomphalos defect, and one with a suspected gastroschisis phenotype. Embryos were excised from the mother ensuring the amnion remained intact and stereo microscopy was performed. Embryos were next embedded in agarose for 3D, high resolution MRI on a 9.4T scanner. Identification of the abnormal embryo phenotypes was not possible using stereo microscopy or conventional ex vivo MRI. Using in amnio MRI, we determined that the abnormal embryos had an exomphalos phenotype with varying severities. In amnio MRI is ideally suited to investigate the complex relationship between embryo and amnion, together with screening for other abnormalities located outside of the mouse embryo, providing a valuable complement to histology and existing imaging methods available to the phenotyping community.  相似文献   
47.
48.
49.
Sur les genres keratella,synchaeta, polyarthra et filinia d'un lac italien   总被引:2,自引:2,他引:0  
Agostino Parise 《Hydrobiologia》1961,18(1-2):121-134
Résumé On a considéré ici quelques formes des genres Keratella, Polyarthra, Synchaeta et Filinia. On a relevé, dans le lac de Nemi, deux races écologiques chez Keratella cochlearis, et une écologiques chez K. quadrata. Chez le gen. Polyarthra on a observé que l'on trouve, suivant l'hypothèse de l'introgression par Pejler (1956), bien plus fréquemment des formes hybrides que des formes typiques. Chez le gen. Synchaeta on a décrit en detail les mastax type tremula et type pectinata; on a exprimé l'opinion qu'il n'est pas possible de distinguer entre elles, par la structure du mastax, les formes S. tremula (ou truncata), S. kiting; S. oblonga et S. lakowitziana. Chez le gen. Filinia on pense qu'il soit possible de distinguer morphologiquement F. longiseta et F. terminalis, mais il est possible qu'à ces deux formes correspondent plusieures espèces.  相似文献   
50.
BackgroundType 2 diabetes mellitus T2DM has a huge and growing burden on public health, whereas new care models are not implemented into clinical practice; in fact the purpose of this study was to test the effectiveness of a program of integrated care for T2DM, compared with ordinary diligence.Methods"Progetto Diabete Calabria" is a new organizational model for the management of patients with diabetes mellitus, based on General Practitioners (GPs) empowerment and the use of a web-based electronic health record, shared in remote consultations among GPs and Hospital Consultants. One-year change in glucose and main cardiovascular risk factors control in 104 patients (Cases) following this integrated care program has been evaluated and compared with that of 208 control patients (Controls) matched for age, gender, and cardiometabolic profile, and followed in an ordinary outpatient medical management by the Consultants only. Both patient groups had Day Hospitals before and after the study period.ResultsThe mean number of accesses to the Consultants during the study was 0.6±0.9 for Cases, and 1.3±1.5 for Controls (p<0.0001). At follow-up, glycated hemoglobin (HbA1c) significantly decreased from 58±6 to 54±8 mmol/mol in Cases only (p=0.01); LDL cholesterol decreased in both groups; body mass index decreased in Cases only, from 31.0±4.8 to 30.5±4.6 kg/m2 (p=0.03).ConclusionsThe present study demonstrates that a health care program based on GPs empowerment and taking care plus remote consultation with Consultants is at least as effective as standard outpatient management, in order to improve the control of T2DM.  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