全文获取类型
收费全文 | 10203篇 |
免费 | 23篇 |
国内免费 | 37篇 |
专业分类
系统科学 | 30篇 |
丛书文集 | 48篇 |
教育与普及 | 30篇 |
理论与方法论 | 24篇 |
现状及发展 | 3961篇 |
研究方法 | 522篇 |
综合类 | 5480篇 |
自然研究 | 168篇 |
出版年
2012年 | 151篇 |
2011年 | 325篇 |
2010年 | 60篇 |
2009年 | 54篇 |
2008年 | 168篇 |
2007年 | 208篇 |
2006年 | 192篇 |
2005年 | 214篇 |
2004年 | 210篇 |
2003年 | 190篇 |
2002年 | 205篇 |
2001年 | 429篇 |
2000年 | 437篇 |
1999年 | 294篇 |
1996年 | 52篇 |
1994年 | 269篇 |
1992年 | 252篇 |
1991年 | 201篇 |
1990年 | 230篇 |
1989年 | 192篇 |
1988年 | 185篇 |
1987年 | 190篇 |
1986年 | 201篇 |
1985年 | 264篇 |
1984年 | 201篇 |
1983年 | 163篇 |
1982年 | 135篇 |
1981年 | 140篇 |
1980年 | 144篇 |
1979年 | 325篇 |
1978年 | 263篇 |
1977年 | 215篇 |
1976年 | 191篇 |
1975年 | 195篇 |
1974年 | 206篇 |
1973年 | 176篇 |
1972年 | 206篇 |
1971年 | 245篇 |
1970年 | 303篇 |
1969年 | 229篇 |
1968年 | 226篇 |
1967年 | 194篇 |
1966年 | 223篇 |
1965年 | 149篇 |
1959年 | 75篇 |
1958年 | 123篇 |
1957年 | 81篇 |
1956年 | 58篇 |
1954年 | 62篇 |
1948年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
953.
A. A. Rokosu T. O. Akunnaezili P. A. Ikhile 《Cellular and molecular life sciences : CMLS》1982,38(1):78-79
Summary Alkaline phosphatases (ALP I and ALP II), isolated and purified fromAspergillus niger exhibited broad specificity towards a wide variety of substrates, and consistently ALP II was more active than ALP I. It is possible that the difference in levels of activity of the 2 enzymes may be of physiological importance in the mycelia ofA. niger. 相似文献
954.
I. Kubo T. Matsumoto F. J. Hanke M. Taniguchi Y. Hayashi 《Cellular and molecular life sciences : CMLS》1985,41(11):1462-1463
Summary A possible new role for the flavonoid (–)-epicatechin (II) is described. It has no growth effects on its own, but when it is added to lettuce and rice seeds together with the known seedling growth inhibitor nagilactone E (I), the growth inhibitor activity ofI can cease and growth stimulation can be observed. 相似文献
955.
Summary Bilateral lesions of the suprachiasmatic nucleus of the hypothalamus of rats abolished circadian rhythms of oxygen consumption and of the respiratory quotient (RQ). The RQ remained constant at a level intermediate between the maximum (about 1.0) and minimum (about 0.9) values in control animals. 相似文献
956.
Summary Incubation of calf rib cartilage slices with antiproteoglycan serum elevates CO2-production, but inhibits biosynthesis of proteochondroitinsulfate and of total protein. Absorbing antiserum with proteoglycan abolishes these effects.Acknowledgment. This work was supported by grant K1 193/9 and 10 from the Deutsche Forschungsgemeinschaft. 相似文献
957.
M. Saragea T. Negru N. Rotaru A. Vladutiu 《Cellular and molecular life sciences : CMLS》1965,21(4):196-197
Résumé Chez 19 chiens présentant des symptomes de EAE, on a trouvé des anticorps sériques anticerveaux pendant divers laps de temps. 相似文献
958.
Lj. T. Mihailović Lj. Kržalić D. Čupić 《Cellular and molecular life sciences : CMLS》1965,21(12):709-710
Résumé On étudie ici la teneur en glutamine, en acide glutamique et en GABA dans des différentes parties du cerveau chez le Spermophile en sommeil hivernal profond et après le réveil de l'hibernation. Les changements les plus remarquables de l'acide glutamique et du GABA ont été constatés dans les structures sous-corticales regardées comme essentielles pour la régulation de ces processus physiologiques coordonnés. 相似文献
959.
Deposition of amyloid β-protein (Aβ) in the brain is an early and invariant neuropathological feature of Alzheimer’s disease
(AD). The current search for anti-AD drugs is mainly focused on modification of the process of accumulation of Aβ in the brain.
Here, we review four anti-amyloidogenic strategies: (i) reduction of Aβ production, which has mainly been approached with
secretase inhibition, (ii) promotion of the Aβ degrading catabolic pathway, including an Aβ degrading enzyme, neprilysin,
(iii) immunotherapy for Aβ and (iv) inhibition of Aβ aggregation. We have reported that AD patients have a favorable molecular
environment for Aβ aggregation and that various compounds, such as polyphenols, interfere with Aβ aggregation and destabilize
preformed Aβ fibrils.
Received 21 December 2005; received after revision 14 February 2006; accepted 29 March 2006 相似文献
960.
Climate-driven trends in contemporary ocean productivity 总被引:6,自引:0,他引:6
Behrenfeld MJ O'Malley RT Siegel DA McClain CR Sarmiento JL Feldman GC Milligan AJ Falkowski PG Letelier RM Boss ES 《Nature》2006,444(7120):752-755
Contributing roughly half of the biosphere's net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks. Each day, more than a hundred million tons of carbon in the form of CO2 are fixed into organic material by these ubiquitous, microscopic plants of the upper ocean, and each day a similar amount of organic carbon is transferred into marine ecosystems by sinking and grazing. The distribution of phytoplankton biomass and NPP is defined by the availability of light and nutrients (nitrogen, phosphate, iron). These growth-limiting factors are in turn regulated by physical processes of ocean circulation, mixed-layer dynamics, upwelling, atmospheric dust deposition, and the solar cycle. Satellite measurements of ocean colour provide a means of quantifying ocean productivity on a global scale and linking its variability to environmental factors. Here we describe global ocean NPP changes detected from space over the past decade. The period is dominated by an initial increase in NPP of 1,930 teragrams of carbon a year (Tg C yr(-1)), followed by a prolonged decrease averaging 190 Tg C yr(-1). These trends are driven by changes occurring in the expansive stratified low-latitude oceans and are tightly coupled to coincident climate variability. This link between the physical environment and ocean biology functions through changes in upper-ocean temperature and stratification, which influence the availability of nutrients for phytoplankton growth. The observed reductions in ocean productivity during the recent post-1999 warming period provide insight on how future climate change can alter marine food webs. 相似文献