全文获取类型
收费全文 | 25054篇 |
免费 | 79篇 |
国内免费 | 115篇 |
专业分类
系统科学 | 102篇 |
丛书文集 | 168篇 |
教育与普及 | 70篇 |
理论与方法论 | 66篇 |
现状及发展 | 10530篇 |
研究方法 | 1150篇 |
综合类 | 12817篇 |
自然研究 | 345篇 |
出版年
2013年 | 164篇 |
2012年 | 361篇 |
2011年 | 702篇 |
2009年 | 157篇 |
2008年 | 458篇 |
2007年 | 539篇 |
2006年 | 507篇 |
2005年 | 531篇 |
2004年 | 481篇 |
2003年 | 490篇 |
2002年 | 458篇 |
2001年 | 930篇 |
2000年 | 923篇 |
1999年 | 594篇 |
1994年 | 338篇 |
1992年 | 556篇 |
1991年 | 425篇 |
1990年 | 484篇 |
1989年 | 429篇 |
1988年 | 390篇 |
1987年 | 441篇 |
1986年 | 455篇 |
1985年 | 586篇 |
1984年 | 427篇 |
1983年 | 383篇 |
1982年 | 344篇 |
1981年 | 332篇 |
1980年 | 330篇 |
1979年 | 841篇 |
1978年 | 632篇 |
1977年 | 583篇 |
1976年 | 502篇 |
1975年 | 515篇 |
1974年 | 602篇 |
1973年 | 532篇 |
1972年 | 529篇 |
1971年 | 624篇 |
1970年 | 831篇 |
1969年 | 625篇 |
1968年 | 632篇 |
1967年 | 578篇 |
1966年 | 575篇 |
1965年 | 410篇 |
1959年 | 212篇 |
1958年 | 348篇 |
1957年 | 225篇 |
1956年 | 207篇 |
1955年 | 178篇 |
1954年 | 194篇 |
1948年 | 169篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
831.
Long-term in vivo imaging of experience-dependent synaptic plasticity in adult cortex 总被引:36,自引:0,他引:36
Do new synapses form in the adult cortex to support experience-dependent plasticity? To address this question, we repeatedly imaged individual pyramidal neurons in the mouse barrel cortex over periods of weeks. We found that, although dendritic structure is stable, some spines appear and disappear. Spine lifetimes vary greatly: stable spines, about 50% of the population, persist for at least a month, whereas the remainder are present for a few days or less. Serial-section electron microscopy of imaged dendritic segments revealed retrospectively that spine sprouting and retraction are associated with synapse formation and elimination. Experience-dependent plasticity of cortical receptive fields was accompanied by increased synapse turnover. Our measurements suggest that sensory experience drives the formation and elimination of synapses and that these changes might underlie adaptive remodelling of neural circuits. 相似文献
832.
Navigating the signalling network in mouse cardiac myocytes 总被引:6,自引:0,他引:6
Cardiac myocytes have a complex network of signals that regulates their essential role in the rhythmic pumping of the heart. This network is an appealing model system in which to study the basic principles underlying cellular signalling mechanisms. Progress in this effort has come through the establishment of standardized myocyte isolation and culture procedures and characterization of important signalling responses. 相似文献
833.
834.
Analysis of the mouse transcriptome based on functional annotation of 60,770 full-length cDNAs 总被引:6,自引:0,他引:6
Okazaki Y Furuno M Kasukawa T Adachi J Bono H Kondo S Nikaido I Osato N Saito R Suzuki H Yamanaka I Kiyosawa H Yagi K Tomaru Y Hasegawa Y Nogami A Schönbach C Gojobori T Baldarelli R Hill DP Bult C Hume DA Quackenbush J Schriml LM Kanapin A Matsuda H Batalov S Beisel KW Blake JA Bradt D Brusic V Chothia C Corbani LE Cousins S Dalla E Dragani TA Fletcher CF Forrest A Frazer KS Gaasterland T Gariboldi M Gissi C Godzik A Gough J Grimmond S Gustincich S Hirokawa N Jackson IJ Jarvis ED Kanai A 《Nature》2002,420(6915):563-573
835.
836.
Gardner MJ Shallom SJ Carlton JM Salzberg SL Nene V Shoaibi A Ciecko A Lynn J Rizzo M Weaver B Jarrahi B Brenner M Parvizi B Tallon L Moazzez A Granger D Fujii C Hansen C Pederson J Feldblyum T Peterson J Suh B Angiuoli S Pertea M Allen J Selengut J White O Cummings LM Smith HO Adams MD Venter JC Carucci DJ Hoffman SL Fraser CM 《Nature》2002,419(6906):531-534
The mosquito-borne malaria parasite Plasmodium falciparum kills an estimated 0.7-2.7 million people every year, primarily children in sub-Saharan Africa. Without effective interventions, a variety of factors-including the spread of parasites resistant to antimalarial drugs and the increasing insecticide resistance of mosquitoes-may cause the number of malaria cases to double over the next two decades. To stimulate basic research and facilitate the development of new drugs and vaccines, the genome of Plasmodium falciparum clone 3D7 has been sequenced using a chromosome-by-chromosome shotgun strategy. We report here the nucleotide sequences of chromosomes 10, 11 and 14, and a re-analysis of the chromosome 2 sequence. These chromosomes represent about 35% of the 23-megabase P. falciparum genome. 相似文献
837.
838.
839.
Porous inorganic solids can be synthesized in complex forms, and here we describe a simple method to create an ultralight, macroporous, crystalline vanadium oxide foam by bubbling oxygen gas produced in situ through a viscous vanadium oxide gel. This foaming process could be extended to other metal oxides. 相似文献
840.