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   118篇
  免费   3篇
  国内免费   19篇
系统科学   4篇
现状及发展   39篇
研究方法   11篇
综合类   79篇
自然研究   7篇
  2021年   4篇
  2019年   4篇
  2018年   3篇
  2017年   3篇
  2016年   3篇
  2015年   5篇
  2014年   3篇
  2013年   10篇
  2012年   7篇
  2011年   9篇
  2010年   1篇
  2009年   2篇
  2008年   3篇
  2007年   3篇
  2006年   5篇
  2005年   4篇
  2004年   3篇
  2003年   2篇
  2002年   4篇
  2001年   3篇
  2000年   2篇
  1999年   5篇
  1992年   3篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1986年   1篇
  1980年   2篇
  1979年   6篇
  1978年   9篇
  1977年   2篇
  1976年   1篇
  1972年   5篇
  1971年   8篇
  1970年   1篇
  1969年   1篇
  1968年   3篇
  1967年   2篇
  1966年   2篇
  1965年   1篇
排序方式: 共有140条查询结果,搜索用时 15 毫秒
131.
Summary The NCA 2 is dilated in about the middle of its length. Neurosecretory material is stored in this dilation. It serves as a secondary neurohaemal organ for lateral neurosecretion.  相似文献   
132.
Evidence for a modulation of the stress response by the pineal gland   总被引:2,自引:0,他引:2  
R Khan  S Daya  B Potgieter 《Experientia》1990,46(8):860-862
Wistar rats show a circadian variation in their response to stress. Pinealectomy exacerbates stress-induced gastric ulceration in rats. This effect is counteracted by melatonin administration.  相似文献   
133.
Résumé La persistance de la radioactivité incorporée dans le cholesterol et les lipides totaux de la myeline cérébrale a été mesurée pendant 200 jours après un injection i.p. de glucose U-14C chez des rats de 6 semaines ayant donc précisément dépassé la période de myelinisation active et également chez des animaux de 6 mois. La radioactivité spécifique relativement faible incorporée dans le cholesterol de la myeline des animaux les plus jeunes a décru lentement tandis que chez les animaux adultes elle est restée pratiquement constante. L'incorporation de carbone de glucose dans le cholesterol de la myeline des animaux adultes ne reflète probablement pas le «turnover» du cholesterol mais pourrait indiquer plutôt que la myeline continue à être formée lentement tout au long de la vie de l'animal.  相似文献   
134.
Zusammenfassung Die Zusammensetzung von in wässeriger Lösung gebildeten Ionenpaaren des Anions [W(CN)4(OH)4]4- mit Cr3+ bzw. Fe3+ wird amperometrisch ermittelt.

Acknowledgment. The authors are grateful to Dr.S. M. F. Rahman for providing necessary facilities and C.S.I.R. (India) for awarding a Junior Fellowship to one of them (K. U.).  相似文献   
135.
136.
研究了任意半环上正则元的广义逆的存在性.给出了任意半环上正则元的{1,2}-逆存在的一些充分条件,同时给出了{1,2}-逆存在时的表达式.作为{1,2}-逆的特殊情形,刻画了任意半环上正则元的Moore-Penrose逆和群逆的存在性.  相似文献   
137.
DC reactive magnetron sputtering technique has been used for the preparation of Al N thin fi lms. The deposition temperature and the fl ow ratio of N2/Ar were varied and subsequent dependency of the fi lms crystallites orientation/texture has been addressed. In general, deposited fi lms were found hexagonal polycrystalline with a(002) preferred orientation. The X-ray diffraction(XRD) data revealed that the fi lm crystallinity improves,with the increase of substrate temperature from 300 ℃to 500℃. The dropped in full width half maximum(FWHM) of the XRD rocking curve value further con fi rmed it. However, increasing substrate temperature above 500 ℃or reducing the nitrogen condition(from 60 to 30% in the environment) induced the growth of crystallites with(102) and(103) orientations. The rise of rocking curve FWHM for the corresponding conditions depicted that the fi lms texture quality deteriorated. A further con fi rmation of the variation in fi lm texture/orentation with the growth conditions has been obtained from the variation in FWHM values of a dominant E1(TO) mode in the Fourier transform infrared(FTIR) spectra and the E2(high) mode in Raman spectra. We have correlated the columnar structure in AFM surface analyses with the(002) or c-axis orientation as well. Spectroscopic ellipsometry of the samples have shown a higher refractive index at 500 ℃growth temperature.  相似文献   
138.
The syndrome of congenital hypoparathyroidism, mental retardation, facial dysmorphism and extreme growth failure (HRD or Sanjad-Sakati syndrome; OMIM 241410) is an autosomal recessive disorder reported almost exclusively in Middle Eastern populations. A similar syndrome with the additional features of osteosclerosis and recurrent bacterial infections has been classified as autosomal recessive Kenny-Caffey syndrome (AR-KCS; OMIM 244460). Both traits have previously been mapped to chromosome 1q43-44 (refs 5,6) and, despite the observed clinical variability, share an ancestral haplotype, suggesting a common founder mutation. We describe refinement of the critical region to an interval of roughly 230 kb and identification of deletion and truncation mutations of TBCE in affected individuals. The gene TBCE encodes one of several chaperone proteins required for the proper folding of alpha-tubulin subunits and the formation of alpha-beta-tubulin heterodimers. Analysis of diseased fibroblasts and lymphoblastoid cells showed lower microtubule density at the microtubule-organizing center (MTOC) and perturbed microtubule polarity in diseased cells. Immunofluorescence and ultrastructural studies showed disturbances in subcellular organelles that require microtubules for membrane trafficking, such as the Golgi and late endosomal compartments. These findings demonstrate that HRD and AR-KCS are chaperone diseases caused by a genetic defect in the tubulin assembly pathway, and establish a potential connection between tubulin physiology and the development of the parathyroid.  相似文献   
139.
Human chromosome 12 contains more than 1,400 coding genes and 487 loci that have been directly implicated in human disease. The q arm of chromosome 12 contains one of the largest blocks of linkage disequilibrium found in the human genome. Here we present the finished sequence of human chromosome 12, which has been finished to high quality and spans approximately 132 megabases, representing approximately 4.5% of the human genome. Alignment of the human chromosome 12 sequence across vertebrates reveals the origin of individual segments in chicken, and a unique history of rearrangement through rodent and primate lineages. The rate of base substitutions in recent evolutionary history shows an overall slowing in hominids compared with primates and rodents.  相似文献   
140.
Atmospheric pressure MOCVD was used to deposit ZnO layers on sapphire and homoepitaxial template under different oxygen flow rates.Oxygen content affects the lattice constant value and texture coefficient of the films as evidenced by the θ-2θ peaks position and their intensity.Films deposited at lower oxygen flow rate possess higher value of strain and stresses.ZnO films deposited at high oxygen flow rates show intense UV emissions while samples prepared under oxygen deficient conditions exhibited defect related emission along with UV luminescence.The results are compared to the ZnO films deposited homoepitaxially on annealed ZnO samples.The data obtained suggest that ZnO stoichiometry is responsible for the structural and optical quality of ZnO films.  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