全文获取类型
收费全文 | 488篇 |
免费 | 1篇 |
国内免费 | 3篇 |
专业分类
系统科学 | 2篇 |
理论与方法论 | 2篇 |
现状及发展 | 112篇 |
研究方法 | 38篇 |
综合类 | 332篇 |
自然研究 | 6篇 |
出版年
2018年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 20篇 |
2011年 | 25篇 |
2010年 | 12篇 |
2009年 | 1篇 |
2008年 | 17篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 24篇 |
2004年 | 32篇 |
2003年 | 19篇 |
2002年 | 11篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1994年 | 1篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1972年 | 12篇 |
1971年 | 12篇 |
1970年 | 18篇 |
1969年 | 8篇 |
1968年 | 14篇 |
1967年 | 14篇 |
1966年 | 11篇 |
1965年 | 8篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有492条查询结果,搜索用时 0 毫秒
441.
P. C. T. Jones 《Cellular and molecular life sciences : CMLS》1971,27(9):1014-1015
Zusammenfassung Feststellung, dass schlafende Goldhamster einen höheren ATP-Gehalt in Gehirn und Leber besitzen als wache Tiere und dass Zeitgeber, wie Licht und Temperatur, sowohl Zellviskosität als auch ATP-Niveau verändern. 相似文献
442.
Dietary cholesterol, sex and scurvy in guinea-pigs 总被引:1,自引:0,他引:1
443.
444.
445.
446.
Replacing the complementarity-determining regions in a human antibody with those from a mouse 总被引:26,自引:0,他引:26
The variable domains of an antibody consist of a beta-sheet framework with hypervariable regions (or complementarity-determining regions--CDRs) which fashion the antigen-binding site. Here we attempted to determine whether the antigen-binding site could be transplanted from one framework to another by grafting the CDRs. We substituted the CDRs from the heavy-chain variable region of mouse antibody B1-8, which binds the hapten NP-cap (4-hydroxy-3-nitrophenacetyl caproic acid; KNP-cap = 1.2 microM), for the corresponding CDRs of a human myeloma protein. We report that in combination with the B1-8 mouse light chain, the new antibody has acquired the hapten affinity of the B1-8 antibody (KNP-cap = 1.9 microM). Such 'CDR replacement' may offer a means of constructing human monoclonal antibodies from the corresponding mouse monoclonal antibodies. 相似文献
447.
A continuous-wave Raman silicon laser 总被引:2,自引:0,他引:2
Achieving optical gain and/or lasing in silicon has been one of the most challenging goals in silicon-based photonics because bulk silicon is an indirect bandgap semiconductor and therefore has a very low light emission efficiency. Recently, stimulated Raman scattering has been used to demonstrate light amplification and lasing in silicon. However, because of the nonlinear optical loss associated with two-photon absorption (TPA)-induced free carrier absorption (FCA), until now lasing has been limited to pulsed operation. Here we demonstrate a continuous-wave silicon Raman laser. Specifically, we show that TPA-induced FCA in silicon can be significantly reduced by introducing a reverse-biased p-i-n diode embedded in a silicon waveguide. The laser cavity is formed by coating the facets of the silicon waveguide with multilayer dielectric films. We have demonstrated stable single mode laser output with side-mode suppression of over 55 dB and linewidth of less than 80 MHz. The lasing threshold depends on the p-i-n reverse bias voltage and the laser wavelength can be tuned by adjusting the wavelength of the pump laser. The demonstration of a continuous-wave silicon laser represents a significant milestone for silicon-based optoelectronic devices. 相似文献
448.
449.
Humphray SJ Oliver K Hunt AR Plumb RW Loveland JE Howe KL Andrews TD Searle S Hunt SE Scott CE Jones MC Ainscough R Almeida JP Ambrose KD Ashwell RI Babbage AK Babbage S Bagguley CL Bailey J Banerjee R Barker DJ Barlow KF Bates K Beasley H Beasley O Bird CP Bray-Allen S Brown AJ Brown JY Burford D Burrill W Burton J Carder C Carter NP Chapman JC Chen Y Clarke G Clark SY Clee CM Clegg S Collier RE Corby N Crosier M Cummings AT Davies J Dhami P Dunn M Dutta I Dyer LW Earthrowl ME Faulkner L 《Nature》2004,429(6990):369-374
Chromosome 9 is highly structurally polymorphic. It contains the largest autosomal block of heterochromatin, which is heteromorphic in 6-8% of humans, whereas pericentric inversions occur in more than 1% of the population. The finished euchromatic sequence of chromosome 9 comprises 109,044,351 base pairs and represents >99.6% of the region. Analysis of the sequence reveals many intra- and interchromosomal duplications, including segmental duplications adjacent to both the centromere and the large heterochromatic block. We have annotated 1,149 genes, including genes implicated in male-to-female sex reversal, cancer and neurodegenerative disease, and 426 pseudogenes. The chromosome contains the largest interferon gene cluster in the human genome. There is also a region of exceptionally high gene and G + C content including genes paralogous to those in the major histocompatibility complex. We have also detected recently duplicated genes that exhibit different rates of sequence divergence, presumably reflecting natural selection. 相似文献
450.
A previously unidentified MECP2 open reading frame defines a new protein isoform relevant to Rett syndrome 总被引:17,自引:0,他引:17
Mnatzakanian GN Lohi H Munteanu I Alfred SE Yamada T MacLeod PJ Jones JR Scherer SW Schanen NC Friez MJ Vincent JB Minassian BA 《Nature genetics》2004,36(4):339-341
Rett syndrome is caused by mutations in the gene MECP2 in approximately 80% of affected individuals. We describe a previously unknown MeCP2 isoform. Mutations unique to this isoform and the absence, until now, of identified mutations specific to the previously recognized protein indicate an important role for the newly discovered molecule in the pathogenesis of Rett syndrome. 相似文献