全文获取类型
收费全文 | 1473篇 |
免费 | 88篇 |
国内免费 | 8篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 31篇 |
2021年 | 43篇 |
2020年 | 25篇 |
2019年 | 32篇 |
2018年 | 49篇 |
2017年 | 42篇 |
2016年 | 52篇 |
2015年 | 83篇 |
2014年 | 103篇 |
2013年 | 92篇 |
2012年 | 137篇 |
2011年 | 120篇 |
2010年 | 94篇 |
2009年 | 62篇 |
2008年 | 76篇 |
2007年 | 81篇 |
2006年 | 70篇 |
2005年 | 64篇 |
2004年 | 40篇 |
2003年 | 38篇 |
2002年 | 35篇 |
2001年 | 29篇 |
2000年 | 36篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 2篇 |
1922年 | 1篇 |
1899年 | 1篇 |
排序方式: 共有1569条查询结果,搜索用时 15 毫秒
131.
Hye-Jin Kim You-Jung Lee Wa Gao Chung-Han Chung Chang-Woo Son Jin-Woo Lee 《Biotechnology and Bioprocess Engineering》2011,16(3):542-548
The optimal conditions for the production of cellulases by a marine bacterium, Psychrobacter aquimaris LBH-10, were established and their effects were compared using orthogonal array experiments based on the Taguchi method.
The optimal conditions of rice bran, peptone and initial pH for the production of avicelase and CMCase by P. aquimaris LBH-10 were 50.0, 3.0, and 8.0 g/L, respectively, whereas those for filter paperase (FPase) were 100.0, 3.0, and 8.0 g/L,
respectively. Rice bran was found to be the most important factor for the production of cellulases based on the calculated
percentage of participation P (%) from an analysis of the variance (ANOVA). The optimal temperature for the cell growth of P. aquimaris LBH-10 was 25°C, whereas that for the production of avicelase, CMCase and FPase was 30°C. The optimal agitation speed and
aeration rate for cell growth was 400 rpm and 1.5 vvm, respectively, whereas those for the production of CMCase were 300 rpm
and 1.0 vvm, respectively. Aeration was found to be more important for cell growth and CMCase production than agitation. The
maximum production of avicelase, CMCase and FPase in a 100 L bioreactor for 72 h under optimized conditions was 83.2, 388.7,
and 75.4 U/mL, respectively. 相似文献
132.
Xiaodong Li Myong Jong Yi Yowhan Son Pil Sun Park Kyeong Hak Lee Yeong Mo Son Rae Hyun Kim Mi Jeong Jeong 《Journal of Plant Biology》2011,54(1):33-42
This study examined the biomass and carbon pools of the main ecosystem components in an age sequence of five Korean pine plantation
forest stands in central Korea. The C contents in the tree and ground vegetation biomass, coarse woody debris, forest floor,
and mineral soil were estimated by analyzing the C concentration of each component. The aboveground and total tree biomass
increased with increasing stand age. The highest C concentration across this chronosequence was found in the tree branch while
the lowest C concentration was found in the ground vegetation. The observed C contents for tree components, ground vegetation,
and coarse woody debris were generally lower than the predicted C contents estimated from a biomass C factor of 0.5. Forest
floor C content was age-independent. Total mineral soil C content appeared to decline initially after establishing Korean
pine plantations and recover by the stand age of 35 years. Although aboveground tree biomass C content showed considerable
accumulation with increasing age, the relative contribution of below ground C to total ecosystem C content varied substantially.
These results suggest that successional development as temporal factor has a key role in estimating the C storage in Korean
pine plantation forests. 相似文献
133.
Hind limb muscles of rodents, such as gastrocnemius and tibialis anterior, are frequently used for in vivo pharmacological studies of the signals essential for the formation and maintenance of mammalian NMJs. However, drug penetration into these muscles after subcutaneous or intramuscular administration is often incomplete or uneven and many NMJs can remain unaffected. Although systemic administration with devices such as mini-pumps can improve the spatiotemporal effects, the invasive nature of this approach can cause confounding inflammatory responses and/or direct muscle damage. Moreover, complete analysis of the NMJs in a hind limb muscle is challenging because it requires time-consuming serial sectioning and extensive immunostaining. The mouse LAL is a thin, flat sheet of muscle located superficially on the dorsum of the neck. It is a fast-twitch muscle that functions to move the pinna. It contains rostral and caudal portions that originate from the midline of the cranium and extend laterally to the cartilaginous portion of each pinna. The muscle is supplied by a branch of the facial nerve that projects caudally as it exits the stylomastoid foramen. We and others have found LAL to be a convenient preparation that offers advantages for the investigation of both short and long-term in vivo effects of drugs on NMJs and muscles. First, its superficial location facilitates multiple local applications of drugs under light anesthesia. Second, its thinness (2-3 layers of muscle fibers) permits visualization and analysis of almost all the NMJs within the muscle. Third, the ease of dissecting it with its nerve intact together with the pattern of its innervation permits supplementary electrophysiological analysis in vitro9,5. Last, and perhaps most importantly, a small applied volume (˜50μl) easily covers the entire muscle surface, provides a uniform and prolonged exposure of all its NMJs to the drug and eliminates the need for a systemic approach1,8.Download video file.(45M, mov) 相似文献
134.
135.
Do Young Kim Han‐Young Cho Hyo Jeong Kim Yi‐Joon Kim Dong‐Ha Shin Kwang‐Hee Son Ho‐Yong Park 《Entomological Research》2011,41(6):297-297
Invertebrates including insects are heterotrophic organisms and widely distributed in ecosystems. Due to their superior ability to digest various types of plant biomass taken as foods, some herbivorous invertebrates have attracted a great deal of industrial attention because such organisms include diverse cellulolytic and hemicellulolytic symbionts in their gut. Recent studies have shown that some of gut microorganisms of herbivores possess one or more extracellular fibrolytic enzymes with unique functions, which can be exploited as useful biocatalysts in various bioindustrial fields. Specifically, microbial hemicellulases with favorable biocatalytic activities are expected to be used for the development of excellent animal feed additives, production of prebiotics such as xylo‐ and mannooligosaccharides, and pretreatment of lignocellulosic biomass for the preparation of fermentable sugars. Here, we review our recent studies accomplished on several hemicellulolytic bacteria isolated from the guts of invertebrates and their glycoside hydrolases such as endo‐β‐1,4‐xylanases and endo‐β‐1,4‐mannanases. 相似文献
136.
Kyung Won Seo Su Jin Heo Yowhan Son Nam Jin Noh Sue Kyoung Lee Chun Gyeong Yoon 《Landscape and Ecological Engineering》2011,7(1):93-99
This study was conducted to examine the influences of soil-moisture conditions on soil nitrogen (N) dynamics, including in
situ soil N mineralization, N availability, and denitrification in a pure Alnus japonica forest located in Seoul, central Korea. The soil N mineralization, N availability, and denitrification were determined using
the buried bag incubation method, ion exchange resin bag method, and acetylene block method, respectively. The annual net
N mineralization rate (kg N ha−1 year−1) and annual N availability (mg N bag−1) were 40.26 and 80.65 in the relatively dry site, −5.43 and 45.39 in the moist site, and 7.09 and 39.17 in the wet site,
respectively. The annual net N mineralization rate and annual N availability in the dry site were significantly higher than
those in the moist and wet sites, whereas there was no significant difference between the moist and wet sites. The annual
mean denitrification rate (kg N ha−1 year−1) in the dry, moist, and wet sites was 2.37, 2.76, and 1.59, respectively. However, there was no significant difference among
sites due to the high spatial and temporal variations. Our results indicate that soil-moisture condition influenced the in
situ N mineralization and resin bag N availability in an A. japonica forest, and treatments of proper drainage for poorly drained sites would increase soil N mineralization and N availability
and consequently be useful to conserve and manage the A. japonica forest. 相似文献
137.
Eun-Jae Lee Woo-Shin Lee Seung Hun Son Shin-Jae Rhim 《Landscape and Ecological Engineering》2011,7(1):137-143
We examined differences in bird communities in relation to characteristics of habitat structure in a pine forest, Samcheok,
South Korea. An unburned stand, a stand burned 7 years earlier and then naturally restored, and a stand where Japanese red
pine Pinus densiflora seedlings were planted after the fire were used for the survey. Habitat structure was dramatically changed by postfire silvicultural
practices. Number of stand trees, shrubs, seedlings, snags, and vegetation coverage were significantly different among study
stands. We made 1,421 detections of 46 bird species during 23 separate line transect surveys per stand between February 2007
and December 2008. The mean number of observed bird species and individuals, bird species diversity index (H′), and Simpson’s diversity index (D
s) were highest in the unburned stand and lowest in the pine seedling stand. There were more species and individuals of forest-dwelling
birds in the unburned stand than both burned stands. Canopy and cavity nesters, foliage searchers, bark gleaners, and timber
drillers were significantly higher in the unburned stand. In the pine seedling stand, densities of birds that prefer open
field and shrub cover were higher. Stand structure was simplified in the pine seedling stand by postfire practices. Because
of differences in habitat structure and bird communities, postfire practices in the burned stand should be re-evaluated. Also,
management strategies for pine forest after forest fires are needed based on results of long-term experiments. 相似文献
138.
Transmission of Fusarium boothii mycovirus via protoplast fusion causes hypovirulence in other phytopathogenic fungi 总被引:1,自引:0,他引:1
There is increasing concern regarding the use of fungicides to control plant diseases, whereby interest has increased in the biological control of phytopathogenic fungi by the application of hypovirulent mycoviruses as a possible alternative to fungicides. Transmission of hypovirulence-associated double-stranded RNA (dsRNA) viruses between mycelia, however, is prevented by the vegetative incompatibility barrier that often exists between different species or strains of filamentous fungi. We determined whether protoplast fusion could be used to transmit FgV1-DK21 virus, which is associated with hypovirulence on F. boothii (formerly F. graminearum strain DK21), to F. graminearum, F. asiaticum, F. oxysporum f. sp. lycopersici, and Cryphonectria parasitica. Relative to virus-free strains, the FgV1-DK21 recipient strains had reduced growth rates, altered pigmentation, and reduced virulence. These results indicate that protoplast fusion can be used to introduce FgV1-DK21 dsRNA into other Fusarium species and into C. parasitica and that FgV1-DK21 can be used as a hypovirulence factor and thus as a biological control agent. 相似文献
139.
140.
Lactoferrin (Lf) has been implicated in the regulation of cell growth. However, the molecular mechanism underlying this effect remains to be elucidated. In this study, we show that Lf is involved in the cell cycle control system in a variety of cell lines, through retinoblastoma protein (Rb)--mediated growth arrest. We observed that Lf induces the expression of Rb, a signal mediator of cell cycle control, and that a majority of this Lf-induced Rb persists in a hypophosphorylated form. In addition, we determined that Lf specifically augments the level of a cyclin-dependent kinase inhibitor, p21, but not p27. Upon treatment with Lf, H1299 cells expressing defective p53 effected an augmentation of endogenous p21 levels, which may contribute to the accumulation of hypophosphorylated Rb. A substantial quantity of active Rb binds more efficiently to E2F1 in cells that express Lf and consequently blocks the expression of an E2F1-responsive gene, thereby suggesting that Lf plays a crucial role in the inhibition of tumor cell growth. Therefore, we conclude that the antiproliferative effects of Lf can likely be attributed to the elevated levels of hypophosphorylated Rb. 相似文献