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   108篇
  免费   10篇
  国内免费   5篇
  2023年   3篇
  2022年   2篇
  2021年   7篇
  2020年   5篇
  2019年   4篇
  2018年   4篇
  2017年   1篇
  2016年   7篇
  2015年   3篇
  2014年   7篇
  2013年   4篇
  2012年   4篇
  2011年   4篇
  2010年   4篇
  2009年   10篇
  2008年   4篇
  2007年   10篇
  2006年   3篇
  2005年   2篇
  2004年   2篇
  2003年   3篇
  2002年   5篇
  2001年   3篇
  1999年   3篇
  1997年   1篇
  1994年   1篇
  1993年   2篇
  1992年   2篇
  1991年   3篇
  1990年   3篇
  1989年   2篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1980年   1篇
排序方式: 共有123条查询结果,搜索用时 15 毫秒
91.
为了考核新生儿接种国产重组(酵母)乙型肝炎(乙肝)疫苗后的免疫效果,并与血源乙肝疫苗效果比较。对1997年出生并接种重组(酵母)乙肝疫苗的新生儿隔年随访一次,采血检测乙肝病毒表面抗原(HBsAg),乙肝病毒表面抗体(抗-HBs)和乙肝病毒核心抗体(抗-HBc),1998年以后对乙肝免疫人群开展急性乙肝发病监测。显示五年期间3次随访检测HBsAg阳性率平均为1.5%,较免前本底的HBsAg阳性率呈较大幅度下降,疫苗保护率为83%(95%可信区间为76.97%~89.02%),无论母亲HBsAg阳性或阴性,使用不同乙肝疫苗的儿童HBsAg阳性率没有统计学差异。接受重组(酵母)乙肝疫苗免疫的对象中,无一例急性乙肝病例报告。重组(酵母)乙肝疫苗有较好的近期保护效果和免疫原性,与以前使用血源乙肝疫苗效果相当。  相似文献   
92.
In order to assess their accuracy for the determination of glucose during the enzymatic hydrolysis of pretreated lignocellulosic biomass, four different blood glucose monitors (BGMs), each utilizing a different enzymatic mechanism for the determination of glucose, were utilized in an experimental setup, which compares the efficiency of ionic liquid pretreatment with dilute acid and alkaline pretreatments applied on corncob. Among the tested devices, Optium Xceed was found to be the most accurate device for the determination of glucose where Accu-Chek Active was the least accurate BGM, yielding similar results to those obtained with DNS method. Based on the HPLC results, the % error values for Optium Xceed ranged between 3.9-10.5% for the determination of glucose concentration. Upon enzymatic hydrolysis, ionic liquid and alkaline pretreatments gave similar glucose yields, which were slightly higher than the dilute acid pretreatment, which were 31.9%, 31.0% and 27.8%, respectively, based on untreated corncob.  相似文献   
93.
光钳捕获,操纵,分离和模拟提取酵母细胞   总被引:1,自引:0,他引:1  
李银妹  鲁润龙 《激光生物学报》1993,2(1):193-195,198
运用光陷阱技术进行对酵母细胞的捕获、操纵、分离和模拟提取。  相似文献   
94.
By means of immunocytochemical demonstration of vasoactive intestinal peptide (VIP) an accumulation of cerebrospinal fluid (CSF)-contacting neurons was found in a circumscribed region of the nucleus accumbens/lateral septum of eleven reptilian (chelonian, lacertilian, ophidian, crocodilian) species. Basal processes of these cells contribute to a subependymal plexus whose density displays considerable interspecific variation. VIP-immunoreactive nerve fibers occur also in the lateral septum and the nucleus accumbens where they encompass immunonegative cells in a basket-like pattern. The CSF-contacting neurons are surrounded by columnar ependymocytes frequently arranged in a pseudostratified manner. These specialized arrays of ependymal cells, however, occupy a more extended area than the VIP-immunoreactive CSF-contacting neurons and can be traced from the rostro-ventral pole of the lateral ventricle to the interventricular foramen. These observations suggest the existence of a telencephalic site of CSF-contacting neurons which may be more widespread than hitherto thought and which may participate in a circumventricular system of the lateral ventricle. Previous studies mainly performed with birds indicate that the VIP-immunoreactive CSF-contacting neurons of the nucleus accumbens might form a part of the encephalic (extraretinal and extrapineal) photoreceptor. However, further experiments are required to test this supposition since the VIP-immunoreactive neurons of the nucleus accumbens remained unlabeled by antibodies against bovine rodopsin and chicken cone-opsin in all eleven species analysed in this investigation.  相似文献   
95.
A study was made of general ecology and metal accumulation in the widespread aquatic moss Rhynchostegium riparioides, (Hedw.) C. Jens. with a view to developing the use of this species as a monitor of heavy metal pollution. In order to establish a data bank for statistical analysis, samples of water and moss were taken within a 6-week period from 105 sites (10-m reaches) in Northern England from streams and rivers of diverse physical and chemical types. Analyses were made of 14 metals (Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba, Pb) in both 2-cm tips and whole plants. The same 14 metals were also measured in both total and filtrable water, together with 12 other variables. Samples of tips were easier to prepare for analysis, but had significantly (p < 0.001) lower concentrations of all metals except Na and K. Significant correlations (p < 0.001) between metal in moss and aqueous metal were found for ten metals (Na, K, Mg, Ca, Mn, Cu, Zn, Cd, Ba, Pb). Correlations between metals in moss and in water were in general similar for tips and whole plants, but much higher for tips with Na, Zn and Cd; the relationship was quite similar whether total or filtrable water was considered, with the exception of Ba where the correlation was much higher with the latter. A multiple regression was used to suggest which variables in water and/ or moss may influence accumulation of Co, Ni, Cu, Zn, Cd, Ba and Pb in the moss. For instance, the variables which had a very highly significant effect on Pb in tips were Pb, filtrable reactive phosphate and Zn in the water. A discussion is included of how the data may be used for monitoring purposes.  相似文献   
96.
随着现代生物技术的快速发展,生物发酵过程在工业生产中的重要性日益增加。为获得质量稳定的发酵产品,通常需要对发酵过程进行监测与调控。生物量可以直接反映生物反应器中细胞代谢的主体——细胞的生长状况,因此实现生物量的在线监测对发酵过程的调控具有重要意义。原位显微镜是一项非侵入式的、基于图像分析的技术,可以实时监测生物过程中的细胞量。文中就原位显微镜的发展及其在细胞生物量实时监测中的应用进行了综述。  相似文献   
97.
该文介绍了飞利浦M1167A监护仪的干扰与无波形显示故障现象,故障原因寻找方法及排除故障的经验。  相似文献   
98.
Feeding behavior of biotype E greenbugs from populations maintained either on corn or sorghum was studied on four corn germplasm entries and two sorghums using a computerized electronic insect feeding monitor. Greenbug fecundity and weight were also measured. Both populations showed differences in time to committed phloem ingestion and time spent ingesting phloem among plant entries, but the two populations did not respond similarly to each entry. Corn-reared greenbugs fed more readily on resistant sorghum than did sorghum-reared greenbugs, whereas sorghum-reared greenbugs fed more readily on some corn. Feeding behavior was not correlated with fecundity. Corn-reared greenbugs were equally or more fecund than sorghum-reared greenbugs on all entries. Time to committed phloem ingestion was negatively correlated with adult weight in the corn-reared population. Offspring of corn-reared greenbugs attained equal or greater weight than those of sorghum-reared ones, even though corn-reared greenbugs weighed less on their colony host (OH45) than did sorghum-reared greenbugs on their colony host (NC + 630X). Weight and fecundity were positively correlated across both populations and all entries, but both greenbug populations were more fecund and weighed more on sorghum and Antigua corn than on the other corn entries. The results confirm that biotype E greenbugs can colonize and use corn as a host, although they are more fecund on sorghum. The results also suggest that corn-reared greenbugs are different from sorghum-reared greenbugs because of either genetic or physiological adaptation, with a corresponding change in fecundity and adult weight. The implications of these results for biotype development are discussed.
Résumé Le comportement alimentaire du biotype E de S. graminum, provenant de souches maintenues soit sur maïs (OH45), soit sur sorgho (NC + 630X) a été examiné sur 4 cultivars de maïs (Antigua, AP670, OH45 et 2570), un sorgho sensible (NC + 630X) et un résistant (PI264453), à l'aide d'un enregistreur électronique à programme d'analyse. La fécondité et la poids ont été analysés séparément. Les résultats des souches on été comparés en fonction des cultivars, et les relations entre comportement alimentaire, fécondité et poids analysées.Le comportement alimentaire des différentes souches sur sorghos résistants et sur 2 cultivars de maïs (2570 OH45) ont divergé, mais pas toujours dans la même direction. Par exemple, les insectes élevés sur maïs ont consommé plus facilement le sorgho résistant que ne l'ont fait les insectes élevés sur sorgho, tandis que le contraire a été observé avec le maïs OH45. Les 2 souches ont montré le même comportement alimentaire sur les différents cultivars. Le maximum de temps à été consacré à s'alimenter sur sorgho résistant et le moins sur le maïs AP6.70.Bien qu'il n'y ait eu aucune différence entre les comportements alimentaires des souches élevées sur maïs et sur sorgho, elles ont présenté des différences de poids et de fécondité. Ces résultats ont montré l'absence de corrélation entre l'ingestion de phloème (PI) et le moment de la première consommation de phloème (CPI) d'une part, et la fécondité d'autre part. Sur tous les cultivars, les insectes élevés sur maïs ont toujours été au moins aussi féconds que ceux élevés sur sorgho. Il en est de même pour le poids de leurs descendants, bien que les insectes élevés sur maïs pèsent moins sur leur hôte propre (OH45) que les insectes élevés sur sorgho sur leur hôte propre (NC + 630X). Les corrélations entre poids et fécondité ont été positives dans les 2 souches et pour tous les cultivars, mais les 2 souches ont été plus fécondes et ont gagné plus de poids sur sorgho et sur le cultivar Antigua de maïs que sur les autres cultivars de maïs. Or, les sorghos et le maïs Antigua sont considérés comme manquant de DIMBOA, qui doit être vraisemblablement présent dans les autres cultivars de maïs. DIMBOA est undacide hydoxamique commun dans le maïs connu pour réduire la fécondité, la survie et la prise de nourriture des hétéroptères.Ces résultats confirment les possibilités de colonisation du maïs par le biotype E de S. graminum, bien qu'il ait été plus fécond sur sorgho. Ces résultats suggèrent aussi que les insectes élevés sur maïs sont différents des insectes élevés sur sorgho, par adaptation génétique ou physiologique, avec modification concomitante du poids des adultes et de la fécondité. Par suite de ces différences, les insectes élevés sur maïs sont plus aptes à utiliser le maïs et le sorgho résistant que les insectes élevés sur sorgho. Tout ceci suggère les possibilités de développement d'un biotype dangereux pour le maïs.
  相似文献   
99.
目的:评估动态心电图对睡眠呼吸暂停综合征(SAS)的诊断价值并分析其与心律失常的关系。方法:选取2017年2月~2019年2月我院收治的SAS患者80例记为病变组,另取同期于我院进行体检的健康人员80例记为对照组。两组均进行动态心电图检查,并以多导睡眠监测仪检查结果为金标准,分析动态心电图诊断SAS的灵敏度、特异度以及准确度。比较两组动态心电图监测结果,心律失常以及ST-T缺血性改变发生情况。结果:动态心电图诊断SAS的灵敏度、特异度、准确度分别为92.31%、75.00%、90.00%。病变组最高心率、房性早搏次数、室性早搏次数均高于对照组,而最低心率低于对照组(均P0.05)。病变组心律失常及ST-T缺血性改变发生率均高于对照组(均P0.05)。结论:动态心电图对SAS的诊断价值较高,具有良好的灵敏度、特异度。临床工作中可通过动态心电图监测,从而及时检出心律失常及ST-T缺血性改变,进一步有效预防猝死的发生。  相似文献   
100.
A beam profile monitor based on a supersonic gas-curtain is currently under development for transverse profile diagnostics of electron and proton beams in the High Luminosity LHC. This monitor uses a thin supersonic gas curtain that crosses the primary beam to be characterized under an angle of 45 degrees. The fluorescence caused by the interaction between the beam and gas-curtain is detected using a specially designed imaging system to determine the 2D transverse profile of the primary beam. Another prototype monitor based on beam induced ionization is installed at The Cockcroft Institute. This paper presents the design features of both the monitors, the gas-jet curtain formation and various experimental tests, including profile measurements of an electron beam, using helium, nitrogen and neon as gases. Such a non-invasive online beam profile monitor would be highly desirable also for medical LINAC’s and storage rings as it can characterize the beam without stopping machine operation. The paper discusses opportunities for simplifying the monitor design for integration into a medical accelerator and expected monitor performance.  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