全文获取类型
收费全文 | 15276篇 |
免费 | 3683篇 |
国内免费 | 14篇 |
专业分类
林业 | 735篇 |
农学 | 643篇 |
基础科学 | 84篇 |
2805篇 | |
综合类 | 1610篇 |
农作物 | 443篇 |
水产渔业 | 3233篇 |
畜牧兽医 | 7180篇 |
园艺 | 278篇 |
植物保护 | 1962篇 |
出版年
2024年 | 19篇 |
2023年 | 59篇 |
2022年 | 92篇 |
2021年 | 269篇 |
2020年 | 647篇 |
2019年 | 1182篇 |
2018年 | 1074篇 |
2017年 | 1123篇 |
2016年 | 1105篇 |
2015年 | 963篇 |
2014年 | 1023篇 |
2013年 | 1381篇 |
2012年 | 971篇 |
2011年 | 1151篇 |
2010年 | 936篇 |
2009年 | 585篇 |
2008年 | 842篇 |
2007年 | 677篇 |
2006年 | 676篇 |
2005年 | 650篇 |
2004年 | 691篇 |
2003年 | 651篇 |
2002年 | 598篇 |
2001年 | 163篇 |
2000年 | 188篇 |
1999年 | 99篇 |
1998年 | 81篇 |
1997年 | 81篇 |
1996年 | 71篇 |
1995年 | 66篇 |
1994年 | 66篇 |
1993年 | 56篇 |
1992年 | 57篇 |
1991年 | 50篇 |
1990年 | 62篇 |
1989年 | 51篇 |
1988年 | 42篇 |
1987年 | 44篇 |
1986年 | 35篇 |
1985年 | 33篇 |
1984年 | 35篇 |
1983年 | 42篇 |
1982年 | 29篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 24篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 21篇 |
1975年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Marie Antonette Juinio‐Meñez Julissah C Evangelio Sasa James A Miralao 《Aquaculture Research》2014,45(8):1332-1340
Field trials were conducted to determine the effects of size, grow‐out period and site on the growth and survival of Holothuria scabra. Juveniles were reared in sea cages in two sites for 2 months during two different times of the year. Juveniles from Experiment 1 were subsequently grown in sea pens for 8 months in one site. The significantly lower survival particularly of the small‐sized group (<0.1 g) in Pilar is likely due to reduced water and sediment quality because of proximity to fish‐farming activities. The importance of grow‐out period was evident in the significant differences in weight increments in all size groups and biomass in the small‐sized group (P < 0.10) in Lucero during Experiment 2 when water temperature range and incidence of rainfall were higher. The decrease in the average weight of adults during the second half of the grow‐out period may be due to the interplay of the reduction in salinity, onset of sexual maturity and biomass exceeding carrying capacity in the pens. The estimated biomass threshold in the sea cages and pens in Lucero were 300 g m?2 and 380 g m?2 respectively. Implications of the results on the viability of small‐scale pen grow‐out culture are discussed. 相似文献
62.
Isabelle Vahirua‐Lechat Frédéric Laure Jean René LeCoz Jean Pierre Bianchini Mereani Bellais Gilles Le Moullac 《Aquaculture Research》2008,39(16):1739-1746
The fatty acid and sterol composition of the oyster Pinctada margaritifera during oogenesis and in eggs was analysed. No major differences were observed during oogenesis, but the egg composition was significantly different from that of gonads. The amount of saturated fatty acids was the highest in eggs and the C16:0 predominant (P<5%); by contrast, the amount of 22:6(n‐3) was significantly lower (P<5%) than in gonads. No major differences were observed for the polar lipid (PL) composition during oogenesis. The main free sterols in gonads and eggs were cholesterol and brassicasterol. Among free sterols, the proportion of cholesterol diminished continuously from the beginning to the end of gonad maturation, and this decrease persisted in eggs after spawning. Cholesterol represented 40% to 55% of the sterol ester encountered in gonad and eggs. This study allowed us to investigate the fatty acid and sterol composition during oogenesis of the pearl oyster P. margaritifera, leading to a clearer understanding of the nutritional requirements of pearl oyster during the reproduction process. 相似文献
63.
Clinical application of multidetector computed tomography and magnetic resonance imaging for evaluation of cranial nerves in horses in comparison with high resolution imaging standards 下载免费PDF全文
J. Dixon R. Lam R. Weller G. Manso‐Díaz M. Smith R. J. Piercy 《Equine Veterinary Education》2017,29(7):376-384
Although horses are affected by cranial nerve disease, our understanding of these structures' imaging anatomy is limited, and the optimal modality for imaging of each of these nerves is unclear. The aim of this study was to describe the imaging appearance of the equine cranial nerves on high‐resolution 1.5T magnetic resonance imaging (MRI) and computed tomography (CT) scans of a cadaver head, and with these as standards, examine the utility of MRI and CT performed in clinical cases. High‐resolution MRI and CT images were prospectively acquired of the head of a normal Thoroughbred gelding following euthanasia. Ten clinical cases undergoing high‐field MRI under general anaesthesia and 10 clinical cases undergoing CT in the standing horse under sedation were retrospectively evaluated by three reviewers to assess cranial nerve visibility. On high‐resolution, thin‐slice, MRI scans of the normal cadaver head, each of the 12 cranial nerves and their topographic location could be appreciated. On high‐resolution cadaver CT, cranial nerves II, V and VII were clearly visible, but others were less easily identified; osseous structures were clearly visualised. Clinical MRI and CT allowed for variable visualisation of the cranial nerves, dependent on the sequence and the orientation of scan planes. High‐field MRI allowed excellent visualisation of equine cranial nerves, whereas CT allowed for more detailed visualisation of the osseous canals and foramina. In live horses, the ability to identify all 12 nerves is challenging with either MRI or CT; however, high‐field MRI enables better visualisation of the nerve bundles than CT. 相似文献
64.
TA Abdulkareem SAM Al‐Sharifi MA Ishak SM Eidan MA Alnimr CW Passavant JR Branen RG Sasser 《Reproduction in domestic animals》2011,46(3):455-462
This study was undertaken to detect pregnancy in Iraqi riverine buffalo (Bubalus bubalis) using three different methods (rectal palpation, plasma progesterone concentration and detection of the presence of pregnancy‐specific protein B (PSPB) with the BioPRYN® enzyme‐linked immunosorbent assay (ELISA) test. The aim of the study was to identify the most sensitive, early and accurate method for detecting pregnancy. Twenty‐two female riverine buffalo that were 6.0 ± 0.93 years old were used. Four blood samples per buffalo were taken via jugular venipuncture at days 22–24, 32–34, 42–44 and 58–61 post‐mating (PM) to measure the progesterone concentration (ng/ml) and to detect the presence of plasma PSPB. The rectal palpation method was employed to evaluate all buffalo on days 42–44 and 58–61 PM. The BioPRYN® test differed (p < 0.01) from the other tests with earlier accuracy for detecting pregnant and non‐pregnant buffalo. Eighty‐eight percent of pregnant and 76.9% of non‐pregnant buffalo were distinguished early (days 22–24 PM) using BioPRYN® and plasma PSPB‐ELISA level (2.09 ± 0.12 ng/ml) in relation to 66.7% and 53.9% detected using the progesterone assay at similar days (4.30 ± 0.40 ng/ml). In conclusion, these results described, for the first time, the early and accurate pregnancy detection of water riverine buffalo using BioPRYN® technology and provided the plasma levels of PSPB using an ELISA test. These findings will improve the reproductive and productive efficiency of Iraqi riverine buffalo by adapting the recent management and reproductive strategies in Iraq and in the world. 相似文献
65.
H.‐H. HUANG L. FENG Y. LIU J. JIANG W.‐D. JIANG K. HU S.‐H. LI X.‐Q. ZHOU 《Aquaculture Nutrition》2011,17(2):e233-e240
A total of 1050 juvenile Jian carp (Cyprinus carpio var. Jian) (8.20 ± 0.02 g) were fed diets containing seven graded levels of thiamin (0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg kg?1) for 60 days to investigate the effects of thiamin on growth, body composition and digestive enzyme activities. Percent weight gain (PWG), feed intake and feed efficiency (FE) were the lowest in fish fed the basal diet (P < 0.05). Protein productive value and lipid productive value increased with increasing dietary thiamin levels up to 1.06 and 0.79 mg kg?1 diet, respectively (P < 0.05). Body protein and lipid increased with increasing dietary thiamin levels (P < 0.05), while moisture and ash of fish carcasses decreased with the increase in dietary thiamin supplementation (P < 0.05). Intestinal folds height had a similar trend to PWG (P < 0.05). Activities of α‐amylase, lipase, trypsin, Na+, K+‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase in intestine were all affected by the dietary thiamin (P < 0.05). In conclusion, thiamin could improve growth and intestinal enzyme activities of juvenile Jian carp. The dietary thiamin requirement of juvenile Jian carp (8.0–60.2 g) based on PWG was 1.02 mg kg?1 diet. 相似文献
66.
67.
Sandra Villagmez-Estrada Jos F Prez Sandra van Kuijk Diego Melo-Durn Asal Forouzandeh Francesc Gonzalez-Sol Matilde DAngelo Francisco J Prez-Cano David Sol-Oriol 《Journal of animal science》2021,99(7)
The aim of the present study was to evaluate the effect of trace mineral nutrition on sow performance, mineral content, and intestinal gene expression of neonate piglets when inorganic mineral sources (ITM) were partially replaced by their organic mineral (OTM) counterparts. At 35 d postmating, under commercial conditions, a total of 240 hyperprolific multiparous sows were allocated into three experimental diets: 1) ITM: with Zn, Cu, and Mn at 80, 15, and 60 mg/kg, respectively; 2) partial replacement trace mineral source (Replace): with a 30 % replacement of ITM by OTM, resulting in ITM + OTM supplementation of Zn (56 + 24 mg/kg), Cu (10.5 + 4.5 mg/kg), and Mn (42 + 18 mg/kg); and 3) Reduce and replace mineral source (R&R): reducing a 50% of the ITM source of Zn (40 + 24 mg/kg), Cu (7.5 + 4.5 mg/kg), and Mn (30 + 18 mg/kg). At farrowing, 40 piglets were selected, based on birth weight (light: <800 g, and average: >1,200 g), for sampling. Since the present study aimed to reflect results under commercial conditions, it was difficult to get an equal parity number between the experimental diets. Overall, no differences between experimental diets on sow reproductive performance were observed. Light piglets had a lower mineral content (P < 0.05) and a downregulation of several genes (P < 0.10) involved in physiological functions compared with their average littermates. Neonate piglets born from Replace sows had an upregulation of genes involved in functions like immunity and gut barrier, compared with those born from ITM sows (P < 0.10), particularly in light piglets. In conclusion, the partial replacement of ITM by their OTM counterparts represents an alternative to the totally inorganic supplementation with improvements on neonate piglet gene expression, particularly in the smallest piglets of the litter. The lower trace mineral storage together with the greater downregulation of gut health genes exposed the immaturity and vulnerability of small piglets. 相似文献
68.
T. D. Procter D. L. Pearl R. L. Finley E. K. Leonard N. Janecko R. J. Reid‐Smith J. S. Weese A. S. Peregrine J. M. Sargeant 《Zoonoses and public health》2014,61(3):208-218
An estimated 6 million pet dogs live in Canadian households with the potential to transmit zoonotic pathogens to humans. Dogs have been identified as carriers of Salmonella, Giardia and Campylobacter spp., particularly Campylobacter upsaliensis, but little is known about the prevalence and risk factors for these pathogens in pet dogs that visit dog parks. This study examined the prevalence of these organisms in the faeces of dogs visiting dog parks in three cities in south‐western Ontario, as well as risk factors for shedding Campylobacter spp. and C. upsaliensis. From May to August 2009, canine faecal samples were collected at ten dog parks in the cities of Guelph and Kitchener‐Waterloo, Ontario, Canada. Owners were asked to complete a questionnaire related to pet characteristics and management factors including age, diet and activities in which the dog participates. Faecal samples were collected from 251 dogs, and 189 questionnaires were completed. Salmonella, Giardia and Campylobacter spp. were present in 1.2%, 6.4% and 43.0% of faecal samples, respectively. Of the Campylobacter spp. detected, 86.1% were C. upsaliensis, 13% were C. jejuni and 0.9% were C. coli. Statistically significant sparing factors associated with the shedding of Campylobacter spp. included the feeding of a commercial dry diet and the dog's exposure to compost. Age of dog had a quadratic effect, with young dogs and senior dogs having an increased probability of shedding Campylobacter spp. compared with adult dogs. The only statistically significant risk factor for shedding C. upsaliensis was outdoor water access including lakes and ditches, while dogs >1 year old were at a lower risk than young dogs. Understanding the pet‐related risk factors for Campylobacter spp. and C. upsaliensis shedding in dogs may help in the development of awareness and management strategies to potentially reduce the risk of transmitting this pathogen from dogs to humans. 相似文献
69.
70.