全文获取类型
收费全文 | 220篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
理论与方法论 | 1篇 |
现状及发展 | 96篇 |
研究方法 | 30篇 |
综合类 | 93篇 |
自然研究 | 4篇 |
出版年
2018年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2012年 | 14篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2008年 | 18篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1975年 | 5篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1968年 | 6篇 |
1967年 | 4篇 |
1966年 | 7篇 |
1965年 | 5篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1961年 | 3篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1954年 | 3篇 |
1948年 | 1篇 |
1947年 | 5篇 |
1946年 | 3篇 |
排序方式: 共有225条查询结果,搜索用时 272 毫秒
121.
High-resolution record of Northern Hemisphere climate extending into the last interglacial period 总被引:4,自引:0,他引:4
Andersen KK Azuma N Barnola JM Bigler M Biscaye P Caillon N Chappellaz J Clausen HB Dahl-Jensen D Fischer H Flückiger J Fritzsche D Fujii Y Goto-Azuma K Grønvold K Gundestrup NS Hansson M Huber C Hvidberg CS Johnsen SJ Jonsell U Jouzel J Kipfstuhl S Landais A Leuenberger M Lorrain R Masson-Delmotte V Miller H Motoyama H Narita H Popp T Rasmussen SO Raynaud D Rothlisberger R Ruth U Samyn D Schwander J Shoji H Siggard-Andersen ML Steffensen JP Stocker T Sveinbjörnsdóttir AE Svensson A Takata M 《Nature》2004,431(7005):147-151
Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degrees C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time. 相似文献
122.
Sharp ZD Barnes JD Brearley AJ Chaussidon M Fischer TP Kamenetsky VS 《Nature》2007,446(7139):1062-1065
Chlorine in the Earth is highly depleted relative to carbonaceous chondrites and solar abundances. Knowledge of the Cl concentrations and distribution on Earth is essential for understanding the origin of these depletions. Large differences in the stable chlorine isotope ratios of meteoritic, mantle and crustal materials have been used as evidence for distinct reservoirs in the solar nebula and to calculate the relative proportions of Cl in the mantle and crust. Here we report that large isotopic differences do not exist, and that carbonaceous chondrites, mantle and crust all have the same 37Cl/35Cl ratios. We have further analysed crustal sediments from the early Archaean era to the Recent epoch and find no systematic isotopic variations with age, demonstrating that the mantle and crust have always had the same delta37Cl value. The similarity of mantle, crust and carbonaceous chondrites establishes that there were no nebular reservoirs with distinct isotopic compositions, no isotopic fractionation during differentiation of the Earth and no late (post-core formation) Cl-bearing volatile additions to the crustal veneer with a unique isotopic composition. 相似文献
123.
Charlotte Froese Fischer 《复旦学报(自然科学版)》2007,46(1)
1IntroductionThe error in a non-relativistic Hartree-Fock(HF)wavefunctionis due to correlationinthe motion of theelectrons.For this reason,the error in the energy is referred to as the correlation energy.For fewelectronsystems,this correlation can beinclu… 相似文献
124.
Defective planar cell polarity in polycystic kidney disease 总被引:15,自引:0,他引:15
Fischer E Legue E Doyen A Nato F Nicolas JF Torres V Yaniv M Pontoglio M 《Nature genetics》2006,38(1):21-23
Morphogenesis involves coordinated proliferation, differentiation and spatial distribution of cells. We show that lengthening of renal tubules is associated with mitotic orientation of cells along the tubule axis, demonstrating intrinsic planar cell polarization, and we demonstrate that mitotic orientations are significantly distorted in rodent polycystic kidney models. These results suggest that oriented cell division dictates the maintenance of constant tubule diameter during tubular lengthening and that defects in this process trigger renal tubular enlargement and cyst formation. 相似文献
125.
Kornak U Reynders E Dimopoulou A van Reeuwijk J Fischer B Rajab A Budde B Nürnberg P Foulquier F;ARCL Debré-type Study Group Lefeber D Urban Z Gruenewald S Annaert W Brunner HG van Bokhoven H Wevers R Morava E Matthijs G Van Maldergem L Mundlos S 《Nature genetics》2008,40(1):32-34
We identified loss-of-function mutations in ATP6V0A2, encoding the a2 subunit of the V-type H+ ATPase, in several families with autosomal recessive cutis laxa type II or wrinkly skin syndrome. The mutations result in abnormal glycosylation of serum proteins (CDG-II) and cause an impairment of Golgi trafficking in fibroblasts from affected individuals. These results indicate that the a2 subunit of the proton pump has an important role in Golgi function. 相似文献
126.
127.
Cia Ramström Hugh Chapman Tero Viitanen Emad Afrasiabi Heli Fox Johanna Kivelä Sanna Soini Laura Korhonen Dan Lindholm Michael Pasternack Kid Törnquist 《Cellular and molecular life sciences : CMLS》2010,67(1):157-169
The HERG (KCNH2) channel is a voltage-sensitive potassium channel mainly expressed in cardiac tissue, but has also been identified in other tissues like neuronal and smooth muscle tissue, and in various tumours and tumour cell lines. The function of HERG has been extensively studied, but it is still not clear what mechanisms regulate the surface expression of the channel. In the present report, using human embryonic kidney cells stably expressing HERG, we show that diacylglycerol potently inhibits the HERG current. This is mediated by a protein kinase C-evoked endocytosis of the channel protein, and is dependent on the dynein–dynamin complex. The HERG protein was found to be located only in early endosomes and not lysosomes. Thus, diacylglycerol is an important lipid participating in the regulation of HERG surface expression and function. 相似文献
128.
Günther FISCHER 《系统科学与系统工程学报(英文版)》2006,15(4):399-418
1. Introduction The world food economy is increasingly being driven by a shift of diets towards livestock products. In the developing countries, consumption of meat has been growing at 5-6 percent p.a., and that of milk and dairy products at 3.3-3.5 percent p.a. in the last few decades. Much of the growth is taking place in China (Huang and Zhang et al. 2003a, Huang and Liu 2003b, Keyzer and van Veen 2004, Ma and Huang et al. 2004, Simpson and Cheng et al.1994, USDA Economic Research Se… 相似文献
129.
130.