全文获取类型
收费全文 | 286篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 2篇 |
丛书文集 | 1篇 |
教育与普及 | 1篇 |
理论与方法论 | 2篇 |
现状及发展 | 57篇 |
研究方法 | 32篇 |
综合类 | 193篇 |
出版年
2020年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2012年 | 13篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 8篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有288条查询结果,搜索用时 62 毫秒
111.
YAO YingMing SHEN Qi WONG Wing Tak 《科学通报(英文版)》2007,52(4):467-470
The lanthanide coordination polymers bearing a 13-membered macrocycle, [(13-EDTA-pnOH)H2] were synthesized. The products [Ln(13-EDTA-pnOH)(H2O)2·NO3]n (Ln = Eu(1), Tb(2), Dy(3)) have been obtained by MS, IR and element analyses. The solid-state structure of 1 was established by single-crystal X-ray analysis. The coordination geometry around the central metal atom in complex 1 is a nine-coor-dinated, tricapped-trigonal prism having six donor atoms (two amine nitrogen atoms, two amide oxygen atoms and two carboxymethyl oxygen atoms) from one ligand, one oxygen atom from a neighboring ligand, and two more oxygen atoms from two water molecules. The europium atoms are linked by―Eu―O―C―O―Eu―bridges to form an infinite chain. 相似文献
112.
113.
114.
Zusammenfassung Nachweis adrenerger Synapsen an Zellkörpern der duodenalen submukösen Ganglien von Ratten nach 6-Hydroxydopamin-Behandlung.
Part of this work was done while I was on sabbatical leave in the Department of Anatomy, Monash University, in 1972, and I thank ProfessorG. C. Schofield for his kindness and encouragement during my stay there. Mr.H. L. Chan rendered invaluable technical assistance. 相似文献
Part of this work was done while I was on sabbatical leave in the Department of Anatomy, Monash University, in 1972, and I thank ProfessorG. C. Schofield for his kindness and encouragement during my stay there. Mr.H. L. Chan rendered invaluable technical assistance. 相似文献
115.
The dramatic progress in the understanding of the dynamics of biomolecules has been largely fuelled by computer simulations based on the law of classical mechanics. However in some respects biomolecules are at the borders of the domain of applicability of classical mechanics. The role of quantum mechanical effects in biomolecular structure and function is therefore worth investigating. Here we present preliminary results from a quantum simulation of a protein and contrast them with results from full classical simulations. The most significant differences are found in motions of high frequency, such as bond stretching or the torsional oscillation of groups that bear hydrogen atoms. The amplitudes of such motions are significantly increased by the penetration of atoms into classically forbidden regions. These differences will directly influence the rates of such processes as proton and electron transfer. 相似文献
116.
I. H. Hall R. A. Izydore R. Simlot O. T. Wong 《Cellular and molecular life sciences : CMLS》1992,48(4):383-386
1,2,4-Triazolidine-3,5-diones and the 3,5-isoxazolidinedione were, observed to be, potent inhibitors of rat lens aldose reductase activity. In vivo in streptozotocin-diabetic rats, selected agents at 20 mg/kg/day, orally for 21 days reduced significantly the sorbitol levels of rbc, lens and sciatic nerves, suggesting that these derivatives may have some usefulness to treat clinical complications of diabetes mellitus. 相似文献
117.
118.
M. Anthony Wong 《Journal of Classification》1984,1(1):255-270
A random sample of sizeN is divided intok clusters that minimize the within clusters sum of squares locally. Some large sample properties of this k-means clustering method (ask approaches withN) are obtained. In one dimension, it is established that the sample k-means clusters are such that the within-cluster sums of squares are asymptotically equal, and that the sizes of the cluster intervals are inversely proportional to the one-third power of the underlying density at the midpoints of the intervals. The difficulty involved in generalizing the results to the multivariate case is mentioned.This research was supported in part by the National Science Foundation under Grant MCS75-08374. The author would like to thank John Hartigan and David Pollard for helpful discussions and comments. 相似文献
119.
Summary Nicotine, in concentrations of 5 and 25 g/ml drinking water, given ad libitum for 10 days, dose-dependently increased lesion formation and worsened ethanol-induced ulceration in rat stomachs. Daily fluid intake and b.wt gain were not adversely affected by nicotine pretreatment.The authors are grateful to Mr C.T. Luk for his skilled technical assistance. 相似文献
120.
Sánchez-Lavega A Orton GS Hueso R García-Melendo E Pérez-Hoyos S Simon-Miller A Rojas JF Gómez JM Yanamandra-Fisher P Fletcher L Joels J Kemerer J Hora J Karkoschka E de Pater I Wong MH Marcus PS Pinilla-Alonso N Carvalho F Go C Parker D Salway M Valimberti M Wesley A Pujic Z 《Nature》2008,451(7177):437-440
The atmospheres of the gas giant planets (Jupiter and Saturn) contain jets that dominate the circulation at visible levels. The power source for these jets (solar radiation, internal heat, or both) and their vertical structure below the upper cloud are major open questions in the atmospheric circulation and meteorology of giant planets. Several observations and in situ measurements found intense winds at a depth of 24 bar, and have been interpreted as supporting an internal heat source. This issue remains controversial, in part because of effects from the local meteorology. Here we report observations and modelling of two plumes in Jupiter's atmosphere that erupted at the same latitude as the strongest jet (23 degrees N). The plumes reached a height of 30 km above the surrounding clouds, moved faster than any other feature (169 m s(-1)), and left in their wake a turbulent planetary-scale disturbance containing red aerosols. On the basis of dynamical modelling, we conclude that the data are consistent only with a wind that extends well below the level where solar radiation is deposited. 相似文献