全文获取类型
收费全文 | 1238篇 |
免费 | 83篇 |
国内免费 | 91篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 21篇 |
2021年 | 40篇 |
2020年 | 40篇 |
2019年 | 48篇 |
2018年 | 36篇 |
2017年 | 41篇 |
2016年 | 39篇 |
2015年 | 26篇 |
2014年 | 54篇 |
2013年 | 68篇 |
2012年 | 42篇 |
2011年 | 66篇 |
2010年 | 34篇 |
2009年 | 60篇 |
2008年 | 67篇 |
2007年 | 56篇 |
2006年 | 52篇 |
2005年 | 45篇 |
2004年 | 58篇 |
2003年 | 46篇 |
2002年 | 38篇 |
2001年 | 38篇 |
2000年 | 33篇 |
1999年 | 25篇 |
1998年 | 25篇 |
1997年 | 35篇 |
1996年 | 29篇 |
1995年 | 9篇 |
1994年 | 21篇 |
1993年 | 19篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 15篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有1412条查询结果,搜索用时 437 毫秒
991.
《Animal : an international journal of animal bioscience》2019,13(2):301-308
Cereal grains treated with organic acids were proved to increase ruminal resistant starch and can relieve the risk of ruminal acidosis. However, previous study mainly focussed on acid-treated barley, the effects of organic acid-treated corn is still unknown. The objectives of this study were to evaluate whether feeding ground corn steeped in citric acid (CA) would affect ruminal pH and fermentation patterns, milk production and innate immunity responses in dairy goats. Eight ruminally cannulated Saanen dairy goats were used in a crossover designed experiment. Each experimental period was 21 day long including 14 days for adaption to new diet and 7 days for sampling and data collection. The goats were fed high-grain diet contained 30% hay and 70% corn-based concentrate. The corn was steeped either in water (control) or in 0.5% (wt/vol) CA solution for 48 h. Goats fed CA diet showed improved ruminal pH status with greater mean and minimum ruminal pH, and shorter (P<0.05) duration of ruminal pH<5.6 and less area of ruminal pH<5.6, 5.8 and 6.0. Concentration of total volatile fatty acid and molar proportion of propionate were less but the molar proportion of acetate was greater (P<0.05) in goats fed the CA diet than the control diet. Concentration of ruminal lipopolysaccharide (LPS) was lower (P<0.05) and that of lactic acid also tended (P<0.10) to be lower in goats fed CA than the control. Although dry matter intake, actual milk yield, yield and content of milk protein and lactose were not affected, the milk fat content and 4% fat-corrected milk tended (P<0.10) to be greater in goats fed CA diet. For the inflammatory responses, peripheral LPS did not differ, whereas the concentration of LPS binding protein and serum amyloid A tended (P<0.10) to be less in goats fed CA diet. Similarly, goats fed CA diet had less (P<0.05) concentration of haptoglobin and tumour necrosis factor. These results indicated that feeding ground corn treated with CA effectively improved ruminal pH status, thus alleviated the risk of ruminal acidosis, reduced inflammatory response, and tend to improve milk yield and milk fat test. 相似文献
992.
SYNOPSIS. The phototactic orientation of the dinoflagellate Gyrodinium dorsum was examined using photomicrographic, cinematographic, and closed-circuit television technics. Particular emphasis was placed on examining the movements and possible roles of the flagella during orientation. The data suggest that the longitudinal flagellum is primarily responsible for phototactic orientation, while the lateral flagellum is involved in forward propulsion and cell rotation. A possible receptor mechanism is proposed by which light direction sensing is accomplished. 相似文献
993.
S. Huda 《Biometrical journal. Biometrische Zeitschrift》1989,31(7):827-832
Minimization of the variance of the difference between estimated responses at two points maximized over pairs of points in the region of interest is taken as the design criterion. Optimal third-order designs are derived for spherical co-centric regions of experimentation and interest with some restrictions imposed on the pairs of points under consideration. 相似文献
994.
995.
996.
Aline B.M. Vaz Andre G.F.C. da Costa Lucélia V.V. Raad Aristóteles Góes-Neto 《Fungal biology》2014,118(3):277-286
Fungal endophytes associated with Myrtaceae from Brazil and Argentina were isolated at three levels of nesting: leaf, individual host trees, and site collection. The alternating logistic regression (ALR) was used to model the data because it offers a computationally convenient method for fitting regression structures involving large clusters. The objectives of this study were to determine: (i) whether the colonization pattern is influenced by environmental variables, (ii) if there is some leaf part they prefer to colonize; (iii) if there is some fungal endophyte aggregation between hierarchical levels; (iv) what the distance effect is on the fungal association. The environmental variables were statistically significant only for Xylaria, i.e., when the elevation and water precipitation increase and the temperature decreases, the odds ratio of finding another fungal endophyte of that genus previously found increases. Sordariomycetes, Xylariales, and Xylaria exhibited leaf fragment preference to petiole and tip. Fungal endophytes showed association within leaf. The horizontal transmission mode and the dispersal limitation may explain this association at the leaf level. Moreover, our results suggest that when a fungal endophyte infects a leaf or host tree individual, the odds ratio of dispersal inside them is greater. 相似文献
997.
This study describes humoral and cell mediated immune (CMI) responses detected in cyclophosphamide (CY) treated animals who were vaccinated with Candida albicans ribosomes and were protected against systemic candidiasis (previous study).Mice treated with CY and vaccinated with C. albicans ribosomes revealed CMI responses towards the ribosomes as measured in vivo by the foot pad swelling test and in vitro by the lymphocyte transformation assay. Both reactions were higher in CY treated and ribosome vaccinated mice than in controls (mice that were only vaccinated). Humoral immune responses were measured by the enzyme linked immunosorbent assay (ELISA). Anti ribosomal antibody titer contrary to the CMI responses was lower in CY treated animals than in non treated controls.These data point to a possible explanation of the mechanisms underlying the ribosomal vaccinations in CY treated hosts, and show the potential of such vaccinations in compromised individuals. 相似文献
998.
Orius species are important biological control agents of thrips in protected crops. Rearing conditions in mass production facilities may affect their performance in the crop when searching for the target prey. The aim of this study was to evaluate and compare the search behaviour and orientation towards prey of two Orius species, O. laevigatus (Fieber) and O. insidiosus (Say) that have been reared in the laboratory under different conditions, with wild (field‐collected) individuals. Adult predator females were placed in a Y‐tube olfactometer and offered a choice between the odours released by plants of different species (cotton, common bean, sweet pepper and cucumber), which were either non‐infested or infested with Frankliniella occidentalis (Pergande) adults.O. laevigatus and O. insidiosus responded to odours from thrips‐infested plants and these responses were influenced by the origin of the colonies. A larger percentage of laboratory‐reared O. laevigatus females (42%) did not made a choice between thrips‐infested or clean plants, compared with wild individuals (17%). Of those females that did respond to plant odours, a smaller percentage of laboratory‐reared O. laevigatus females (34%) responded to the odours from thrips‐infested plants compared with wild insects (76%). No significant differences were found inO. insidiosus females that did not make a choice between thrips‐infested or clean plants (14% for wild vs. 17% for lab individuals). Also, no significant differences were found between O. insidiosus females that selected thrips‐infested plants at the corresponding proportion of wild (75%) and laboratory‐reared (70%) individuals. We propose that the olfactometer test could be a complementary evaluation aspect to the already developed quality criteria for performance of mass‐reared Orius predators. 相似文献
999.
Lipid Replacement Therapy, the use of functional oral supplements containing cell membrane phospholipids and antioxidants, has been used to replace damaged, usually oxidized, membrane glycerophospholipids that accumulate during aging and in various clinical conditions in order to restore cellular function. This approach differs from other dietary and intravenous phospholipid interventions in the composition of phospholipids and their defense against oxidation during storage, ingestion, digestion and uptake as well as the use of protective molecules that noncovalently complex with phospholipid micelles and prevent their enzymatic and bile disruption. Once the phospholipids have been taken in by transport processes, they are protected by several natural mechanisms involving lipid receptors, transport and carrier molecules and circulating cells and lipoproteins until their delivery to tissues and cells where they can again be transferred to intracellular membranes by specific and nonspecific transport systems. Once delivered to membrane sites, they naturally replace and stimulate removal of damaged membrane lipids. Various chronic clinical conditions are characterized by membrane damage, mainly oxidative but also enzymatic, resulting in loss of cellular function. This is readily apparent in mitochondrial inner membranes where oxidative damage to phospholipids like cardiolipin and other molecules results in loss of trans-membrane potential, electron transport function and generation of high-energy molecules. Recent clinical trials have shown the benefits of Lipid Replacement Therapy in restoring mitochondrial function and reducing fatigue in aged subjects and patients with a variety of clinical diagnoses that are characterized by loss of mitochondrial function and include fatigue as a major symptom. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy. 相似文献
1000.
Suzy Y. Rogiers Dennis H. Greer Ron J. Hutton Simon J. Clarke 《The Annals of applied biology》2011,158(1):106-114
Water‐use efficiency in grapevines is dependent on the aerial and below‐ground environment of the plant. Specifically, transpiration efficiency, the ratio of net carbon fixation to water loss, may be influenced by soil moisture and the leaf‐to‐air vapour pressure deficit (VPD) in the soil–plant–atmosphere continuum. The interactive effect of these abiotic parameters, however, has not been suitably investigated in field‐grown grapevines. Accordingly, gas exchange of an anisohydric variety, Semillon, was assessed across a number of vineyards in two warm grape‐growing regions of New South Wales (NSW) to ascertain how soil moisture and VPD interact to affect transpiration efficiency at the leaf level. Leaf gas exchange measurements demonstrated that the rate of transpiration (E) was driven by VPD, particularly under high soil moisture. Both high VPD and low soil moisture decreased photosynthesis (A) and instantaneous leaf transpiration efficiency (A/E). Increased intrinsic leaf transpiration efficiency (A/g) in response to drying soil was limited to vines growing in a non‐irrigated vineyard. In this site, A/g was negatively related to vine water status. VPD did not have a substantial influence on A/g in any vineyard. While VPD is the main driver for A/E, soil moisture is an important determinant of A/g. Under high VPD, stomatal closure in Semillon leaves was not substantial enough to suitably curtail transpiration, and as a consequence A/E declined. These data indicate that in warm climates, irrigation scheduling of anisohydric varieties must take into account both VPD and soil moisture so that vine water status can be maintained. 相似文献