全文获取类型
收费全文 | 31603篇 |
免费 | 86篇 |
国内免费 | 152篇 |
专业分类
系统科学 | 132篇 |
丛书文集 | 289篇 |
教育与普及 | 101篇 |
理论与方法论 | 92篇 |
现状及发展 | 14142篇 |
研究方法 | 1271篇 |
综合类 | 15425篇 |
自然研究 | 389篇 |
出版年
2013年 | 224篇 |
2012年 | 424篇 |
2011年 | 771篇 |
2008年 | 540篇 |
2007年 | 617篇 |
2006年 | 600篇 |
2005年 | 611篇 |
2004年 | 634篇 |
2003年 | 598篇 |
2002年 | 557篇 |
2001年 | 973篇 |
2000年 | 982篇 |
1999年 | 622篇 |
1994年 | 367篇 |
1992年 | 574篇 |
1991年 | 443篇 |
1990年 | 543篇 |
1989年 | 481篇 |
1988年 | 469篇 |
1987年 | 528篇 |
1986年 | 540篇 |
1985年 | 663篇 |
1984年 | 461篇 |
1983年 | 461篇 |
1982年 | 412篇 |
1981年 | 403篇 |
1980年 | 427篇 |
1979年 | 1014篇 |
1978年 | 804篇 |
1977年 | 742篇 |
1976年 | 625篇 |
1975年 | 695篇 |
1974年 | 860篇 |
1973年 | 758篇 |
1972年 | 737篇 |
1971年 | 925篇 |
1970年 | 1125篇 |
1969年 | 912篇 |
1968年 | 941篇 |
1967年 | 819篇 |
1966年 | 742篇 |
1965年 | 543篇 |
1964年 | 205篇 |
1959年 | 294篇 |
1958年 | 531篇 |
1957年 | 383篇 |
1956年 | 336篇 |
1955年 | 321篇 |
1954年 | 322篇 |
1948年 | 272篇 |
排序方式: 共有10000条查询结果,搜索用时 333 毫秒
971.
Wabnitz H Bittner L de Castro AR Döhrmann R Gürtler P Laarmann T Laasch W Schulz J Swiderski A von Haeften K Möller T Faatz B Fateev A Feldhaus J Gerth C Hahn U Saldin E Schneidmiller E Sytchev K Tiedtke K Treusch R Yurkov M 《Nature》2002,420(6915):482-485
Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength, a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion. 相似文献
972.
973.
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
974.
975.
976.
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
977.
978.
979.
980.
A cat cloned by nuclear transplantation 总被引:1,自引:0,他引:1
Shin T Kraemer D Pryor J Liu L Rugila J Howe L Buck S Murphy K Lyons L Westhusin M 《Nature》2002,415(6874):859
Sheep, mice, cattle, goats and pigs have all been cloned by transfer of a donor cell nucleus into an enucleated ovum, and now we add the successful cloning of a cat (Felis domesticus) to this list. However, this cloning technology may not be readily extendable to other mammalian species if our understanding of their reproductive processes is limited or if there are species-specific obstacles. 相似文献