全文获取类型
收费全文 | 46640篇 |
免费 | 3413篇 |
国内免费 | 19篇 |
出版年
2023年 | 145篇 |
2022年 | 124篇 |
2021年 | 751篇 |
2020年 | 568篇 |
2019年 | 682篇 |
2018年 | 1027篇 |
2017年 | 906篇 |
2016年 | 1477篇 |
2015年 | 2321篇 |
2014年 | 2668篇 |
2013年 | 2980篇 |
2012年 | 3942篇 |
2011年 | 3780篇 |
2010年 | 2392篇 |
2009年 | 2189篇 |
2008年 | 3030篇 |
2007年 | 2912篇 |
2006年 | 2542篇 |
2005年 | 2357篇 |
2004年 | 2162篇 |
2003年 | 1864篇 |
2002年 | 1611篇 |
2001年 | 1296篇 |
2000年 | 1226篇 |
1999年 | 985篇 |
1998年 | 378篇 |
1997年 | 326篇 |
1996年 | 229篇 |
1995年 | 211篇 |
1994年 | 209篇 |
1993年 | 173篇 |
1992年 | 326篇 |
1991年 | 296篇 |
1990年 | 266篇 |
1989年 | 228篇 |
1988年 | 173篇 |
1987年 | 163篇 |
1986年 | 132篇 |
1985年 | 105篇 |
1984年 | 77篇 |
1983年 | 84篇 |
1982年 | 63篇 |
1981年 | 55篇 |
1980年 | 54篇 |
1979年 | 69篇 |
1978年 | 51篇 |
1977年 | 53篇 |
1976年 | 43篇 |
1975年 | 44篇 |
1974年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Menyanthes trifoliata is a threatened and endangered species in Korea and USA. To assess the important ecological characteristics for its conservation
and restoration, we measured the level of soluble reactive phosphorus (SRP) in the water, total N and C contents in the plants,
and the water-holding capacity of the surrounding floating peat mat. These factors, which limit the success of aquatic macrophytes,
were examined for their effects on the growth of this species. Leaflet areas and petiole lengths ranged from 6.1 cm2 and 12.4 cm, respectively, at a water depth of 5 cm, to 22.7 cm2 and 33.0 cm, respectively, at 40 cm. The peat mat was able to retain water at a depth of 5 to 45 cm. SRPs ranged from 10
to 46 ppb, while total C and N contents were between 0.62% (petiole) and 2.76% (leaf), and between 39.7% (petiole) and 43.8%
(stem), respectively. The water-holding level was not correlated with SRP, and neither phosphorus nor nitrogen content affected
plant growth. However, the capacity of the floating mat to hold water as the depth subsided was positively related to growth.
This suggests that such mats are good tools for restoring populations ofM. trifoliata when materials with high water-holding capacities are used. 相似文献
33.
34.
Surface Plasmon Resonance Imaging-Based Protein Array Chip System for Monitoring a Hexahistidine-Tagged Protein during Expression and Purification 下载免费PDF全文
Hyeon-Su Ro Sun Ok Jung Byung Hoon Kho Hyung Pyo Hong Jae Sung Lee Yong-Beom Shin Min Gon Kim Bong Hyun Chung 《Applied microbiology》2005,71(2):1089-1092
A surface plasmon resonance imaging-based Ni2+-iminodiacetic acid-coated gold chip system was developed to enable specific detection of a hexahistidine-tagged recombinant protein in crude extracts or in column chromatography fractions. This system is especially advantageous for high-throughput analysis of multiple proteins. 相似文献
35.
Cao Dinh Hung Chang-Hee Hong Seon-Ki Kim Kyu-Han Lee Jea-Young Park Min-Woo Nam Dae-Ho Choi Hye-In Lee 《Acta Physiologiae Plantarum》2016,38(6):152
Light-emitting diodes (LEDs) are useful for the growth of many plants, but not known for blueberry species. This study examined the effects of fluorescent lamps and 100 % red, 80 % red plus 20 % blue, 50 % red plus 50 % blue, and 100 % blue LEDs on the growth and development of highbush blueberry shoots under aseptic and non-aseptic conditions. Results revealed that monochromatic blue LEDs accumulated the highest contents of leaf chlorophylls. In contrast, monochromatic red LEDs inhibited chlorophyll accumulation, but produced the longest shoots and roots and provided high percentages of side shoot formation from ex vitro plants. Mixed LEDs, particularly 50 % red plus 50 % blue light, improved plant growth with respect to notably increased shoot and root biomass. Direct rooting of in vitro shoots under non-aseptic conditions was readily achieved using a commercial mixture of perlite and peat moss with high humidity controls. These findings obviously suggest the efficient use of LEDs to replace traditional fluorescent lamps in large-scale propagation of the highbush blueberry, and also pave the way for future studies on LEDs for standardizing micropropagation protocols to shrub crops and woody plants. 相似文献
36.
37.
Boian S. Alexandrov Vladimir Gelev Yevgeniya Monisova Ludmil B. Alexandrov Alan R. Bishop Kim
. Rasmussen Anny Usheva 《Nucleic acids research》2009,37(7):2405-2410
No simple model exists that accurately describes the melting behavior and breathing dynamics of double-stranded DNA as a function of nucleotide sequence. This is especially true for homogenous and periodic DNA sequences, which exhibit large deviations in melting temperature from predictions made by additive thermodynamic contributions. Currently, no method exists for analysis of the DNA breathing dynamics of repeats and of highly G/C- or A/T-rich regions, even though such sequences are widespread in vertebrate genomes. Here, we extend the nonlinear Peyrard–Bishop–Dauxois (PBD) model of DNA to include a sequence-dependent stacking term, resulting in a model that can accurately describe the melting behavior of homogenous and periodic sequences. We collect melting data for several DNA oligos, and apply Monte Carlo simulations to establish force constants for the 10 dinucleotide steps (CG, CA, GC, AT, AG, AA, AC, TA, GG, TC). The experiments and numerical simulations confirm that the GG/CC dinucleotide stacking is remarkably unstable, compared with the stacking in GC/CG and CG/GC dinucleotide steps. The extended PBD model will facilitate thermodynamic and dynamic simulations of important genomic regions such as CpG islands and disease-related repeats. 相似文献
38.
39.
40.
Se-Chan Kim Alexander Ghanem Heidi Stapel Klaus Tiemann Pascal Knuefermann Andreas Hoeft Rainer Meyer Christian Grohé Anne A Knowlton Georg Baumgarten 《BMC physiology》2007,7(1):5