全文获取类型
收费全文 | 329808篇 |
免费 | 33595篇 |
国内免费 | 254篇 |
出版年
2018年 | 4000篇 |
2017年 | 3789篇 |
2016年 | 5203篇 |
2015年 | 7048篇 |
2014年 | 7600篇 |
2013年 | 11083篇 |
2012年 | 12353篇 |
2011年 | 12159篇 |
2010年 | 7930篇 |
2009年 | 6961篇 |
2008年 | 10481篇 |
2007年 | 10404篇 |
2006年 | 9892篇 |
2005年 | 9249篇 |
2004年 | 9078篇 |
2003年 | 8610篇 |
2002年 | 8216篇 |
2001年 | 12796篇 |
2000年 | 12864篇 |
1999年 | 10103篇 |
1998年 | 3662篇 |
1997年 | 3800篇 |
1996年 | 3682篇 |
1995年 | 3416篇 |
1994年 | 3318篇 |
1993年 | 3304篇 |
1992年 | 8288篇 |
1991年 | 8203篇 |
1990年 | 7827篇 |
1989年 | 7791篇 |
1988年 | 7172篇 |
1987年 | 6886篇 |
1986年 | 6291篇 |
1985年 | 6473篇 |
1984年 | 5426篇 |
1983年 | 4540篇 |
1982年 | 3549篇 |
1981年 | 3281篇 |
1980年 | 3087篇 |
1979年 | 5126篇 |
1978年 | 3996篇 |
1977年 | 3851篇 |
1976年 | 3538篇 |
1975年 | 3958篇 |
1974年 | 4366篇 |
1973年 | 4293篇 |
1972年 | 3839篇 |
1971年 | 3565篇 |
1970年 | 3237篇 |
1969年 | 3154篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
Ana Rodríguez Takehiko Shimada Magdalena Cervera Ana Redondo Berta Alquézar María Jesús Rodrigo Lorenzo Zacarías Lluís Palou María M López Leandro Pe?a 《Plant signaling & behavior》2015,10(6)
Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores. 相似文献
4.
5.
N. Cappetti A. Naddeo G. F. Solitro 《Computer methods in biomechanics and biomedical engineering》2016,19(12):1278-1285
The aim of this work is to show a quick and simple procedure able to identify the geometrical parameters of the intervertebral disc that strongly affect the behavior of the FEM model. First, we allocated a selection criterion for the minimum number of geometrical parameters that describe, with a good degree of approximation, a healthy human vertebra. Next, we carried out a sensitivity analysis using the ‘Taguchi orthogonal array’ to arrive at a quick identification of the parameters that strongly affect the behavior of the Fem model. 相似文献
6.
Joyce S. F. D. de Almeida Teobaldo R. Cuya Guizado Ana P. Guimarães Teodorico C. Ramalho Arlan S. Gonçalves Martijn C. de Koning 《Journal of biomolecular structure & dynamics》2016,34(12):2632-2642
In the present work, we performed docking and molecular dynamics simulations studies on two groups of long-tailored oximes designed as peripheral site binders of acetylcholinesterase (AChE) and potential penetrators on the blood brain barrier. Our studies permitted to determine how the tails anchor in the peripheral site of sarin-inhibited human AChE, and which aminoacids are important to their stabilization. Also the energy values obtained in the docking studies corroborated quite well with the experimental results obtained before for these oximes. 相似文献
7.
David Dubbeldam Sofía Calero Donald E. Ellis Randall Q. Snurr 《Molecular simulation》2016,42(2):81-101
A new software package, RASPA, for simulating adsorption and diffusion of molecules in flexible nanoporous materials is presented. The code implements the latest state-of-the-art algorithms for molecular dynamics and Monte Carlo (MC) in various ensembles including symplectic/measure-preserving integrators, Ewald summation, configurational-bias MC, continuous fractional component MC, reactive MC and Baker's minimisation. We show example applications of RASPA in computing coexistence properties, adsorption isotherms for single and multiple components, self- and collective diffusivities, reaction systems and visualisation. The software is released under the GNU General Public License. 相似文献
8.
9.
Thomas Arn Hansen Helena Fridholm Tobias Guldberg Fr?slev Kristín Rós Kjartansdóttir Eske Willerslev Lars Peter Nielsen Anders Johannes Hansen 《PloS one》2015,10(11)
Rattus norvegicus (R. norvegicus) are ubiquitous and their presence has several effects on the human populations in our urban areas on a global scale. Both historically and presently, this close interaction has facilitated the dissemination of many pathogens to humans, making screening for potentially zoonotic and emerging viruses in rats highly relevant. We have investigated faecal samples from R. norvegicus collected from urban areas using a protocol based on metagenomic enrichment of circular DNA genomes and subsequent sequencing. We found a new type of papillomavirus, with a L1 region 82% identical to that of the known R. norvegicus Papillomavirus 2. Additionally, we found 20 different circular replication associated protein (Rep)-encoding single stranded DNA (CRESS-DNA) virus-like genomes, one of which has homology to the replication-associated gene of Beak and feather disease virus. Papillomaviruses are a group of viruses known for their carcinogenic potential, and although they are known to infect several different vertebrates, they are mainly studied and characterised in humans. CRESS-DNA viruses are found in many different environments and tissue types. Both papillomaviruses and CRESS-DNA viruses are known to have pathogenic potential and screening for novel and known viruses in R. norvegicus could help identify viruses with pathogenic potential. 相似文献
10.