全文获取类型
收费全文 | 3101篇 |
免费 | 208篇 |
国内免费 | 2篇 |
专业分类
林业 | 160篇 |
农学 | 56篇 |
基础科学 | 27篇 |
496篇 | |
综合类 | 601篇 |
农作物 | 102篇 |
水产渔业 | 185篇 |
畜牧兽医 | 1408篇 |
园艺 | 76篇 |
植物保护 | 200篇 |
出版年
2023年 | 22篇 |
2022年 | 22篇 |
2021年 | 56篇 |
2020年 | 80篇 |
2019年 | 76篇 |
2018年 | 59篇 |
2017年 | 59篇 |
2016年 | 73篇 |
2015年 | 51篇 |
2014年 | 71篇 |
2013年 | 133篇 |
2012年 | 183篇 |
2011年 | 224篇 |
2010年 | 136篇 |
2009年 | 90篇 |
2008年 | 221篇 |
2007年 | 196篇 |
2006年 | 195篇 |
2005年 | 163篇 |
2004年 | 142篇 |
2003年 | 152篇 |
2002年 | 173篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 29篇 |
1998年 | 25篇 |
1997年 | 19篇 |
1996年 | 30篇 |
1995年 | 13篇 |
1994年 | 21篇 |
1993年 | 21篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 21篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1971年 | 16篇 |
1969年 | 14篇 |
1967年 | 13篇 |
排序方式: 共有3311条查询结果,搜索用时 421 毫秒
91.
Todd SE Mellor DJ Stafford KJ Gregory NG Bruce RA Ward RN 《Research in veterinary science》2000,68(2):125-134
The effects of food withdrawal for 30 hours and transport for up to 12 hours on 5- to 10-day-old calves were determined by monitoring plasma concentrations of glucose, beta-hydroxybutyrate, urea, lactate and creatine phosphokinase. In addition gamma-glutamyl transferase activity, packed cell volume, total plasma protein concentration, bodyweight and rectal temperature were recorded. Food withdrawal for 30 hours caused hypoglycemia but calves maintained normothermia and although their beta-hydroxybutyrate level increased indicating lipid mobilisation, the changes in blood urea level were minimal indicating low amino acid catabolism. When calves were transported for 12 hours in addition to having food withdrawn for 30 hours, they remained normoglycemic for six hours longer than non-transported calves, probably due to an effect of muscular activity during bracing against truck movements. Stocking calves at a lower density during transport apparently had a beneficial effect, as calves were able to lie down throughout the journey and therefore produced a similar metabolic profile to resting, non-transported animals. Transport and food withdrawal had no obvious effects on calf hydration. The results of this study suggest that food withdrawal for up to 30 hours and transport for up to 12 hours had no detrimental effects on the metabolism of healthy and clinically normal calves. With correct feeding regimes and transport protocols, welfare compromise in young, healthy calves being transported for up to 12 hours can be minimised when they are slaughtered within 30 hours of the start of transport. 相似文献
92.
Jessica D Lightsey Sentiel A Rommel Alexander M Costidis Thomas D Pitchford 《Journal of zoo and wildlife medicine》2006,37(3):262-275
Between 1993 and 2003, 713 (24%) of 2,940 dead Florida manatees (Trichechus manatus latirostris) recovered from Florida waters and examined were killed by watercraft-induced trauma. It was determined that this mortality was the result of watercraft trauma because the external wound patterns and the internal lesions seen during gross necropsy are recognizable and diagnostic. This study documents the methods used in determining watercraft-related mortality during gross necropsy and explains why these findings are diagnostic. Watercraft can inflict sharp- and blunt-force trauma to manatees, and both types of trauma can lead to mortality. This mortality may be a direct result of the sharp and blunt forces or from the chronic effects resulting from either force. In cases in which death is caused by a chronic wound-related complication, the original incident is usually considered to be the cause of death. Once a cause of death is determined, it is recorded in an extensive database and is used by Federal and state managers in developing strategies for the conservation of the manatee. Common sequelae to watercraft-induced trauma include skin lesions, torn muscles, fractured and luxated bones, lacerated internal organs, hemothorax, pneumothorax, pyothorax, hydrothorax, abdominal hemorrhage and ascites, and pyoperitoneum. 相似文献
93.
94.
Bruce K Wobeser Beverly A Kidney Barbara E Powers Stephen J Withrow Monique N Mayer Maria T Spinato Andrew L Allen 《Journal of veterinary diagnostic investigation》2007,19(4):439-443
Agreement among pathologists interpreting histologic specimens is an area of interest within human pathology, but little work in this area has been reported in the veterinary literature. Agreement among pathologists evaluating routine histologic sections of amputated digits from cats and dogs submitted to multiple diagnostic centers was examined. Histologic sections from surgical specimens were reviewed in a blinded fashion by two pathologists, and a comparison to the original diagnosis, as stated in the diagnostic report, was recorded. A total of 513 cases were reviewed, and complete agreement was reached in 409 (79.7%). Of the 104 instances of disagreement, 77 (74.0%) were considered to be of clinical significance. The diagnosis of keratoacanthoma was disagreed with in 19 of 21 diagnoses (90.4%). No other individual diagnosis was similarly disputed. The overall level of disagreement is large and is similar to that reported in human pathology and suggests that further study of this issue would be useful in veterinary pathology. 相似文献
95.
John M Sykes Michael M Garner Leah L Greer Nancy P Lung Rob L Coke Frank Ridgley Mitch Bush Richard J Montali Ben Okimoto Robert Schmidt Jack L Allen Bruce A Rideout Patricia A Pesavento Edward C Ramsay 《Journal of zoo and wildlife medicine》2007,38(2):300-308
Oral eosinophilic granulomas were diagnosed in 16 tigers (Panthera tigris). All lesions were located on the hard or soft palate and typically consisted of flat or slightly raised circular ulcers. Histologic features of these lesions were essentially identical to those seen in oral eosinophilic granulomas of domestic cats and dogs. No clinical signs were noted in eight cases, though various degrees of inappetence, excessive salivation, and dysphagia were noted in the other eight tigers. Six cases were not treated. Treatment for the remaining 10 cases centered on corticosteroids and additional treatments included surgical removal, cryotherapy, antibiotics, and chlorpheniramine. Treatment with corticosteroids did appear to be effective in some cases, though lesions would worsen after cessation of therapy and no cases were cured. In addition, three cases developed complications possibly related to this corticosteroid therapy. The etiology of these lesions remains unknown, though an underlying allergic condition is likely. 相似文献
96.
97.
A.Bruce Webster 《中国家禽》2007,29(19):48-49
当发生禽流感时,对规定范围内家禽必须进行扑杀清群.目前使用比较普遍的清群方法有:颈椎脱臼、水基泡沫、投毒、气体致死等.…… 相似文献
98.
Ariena H. C. van Bruggen Alexander M. Semenov Anne D. van Diepeningen Oscar J. de Vos Wim J. Blok 《European journal of plant pathology / European Foundation for Plant Pathology》2006,115(1):105-122
A healthy soil is often defined as a stable soil system with high levels of biological diversity and activity, internal nutrient
cycling, and resilience to disturbance. This implies that microbial fluctuations after a disturbance would dampen more quickly
in a healthy than in a chronically damaged and biologically impoverished soil. Soil could be disturbed by various processes,
for example addition of a nutrient source, tillage, or drying-rewetting. As a result of any disturbance, the numbers of heterotrophic
bacteria and of individual species start to oscillate, both in time and space. The oscillations appear as moving waves along
the path of a moving nutrient source such as a root tip. The phase and period for different trophic groups and species of
bacteria may be shifted indicating that succession occurs. DGGE, Biolog and FAME analysis of subsequent populations in oscillation
have confirmed that there is a cyclic succession in microbial communities. Microbial diversity oscillates in opposite direction
from oscillations in microbial populations. In a healthy soil, the amplitudes of these oscillations will be small, but the
background levels of microbial diversity and activity are high, so that soil-borne diseases will face more competitors and
antagonists. However, soil-borne pathogens and antagonists alike will fluctuate in time and space as a result of growing plant
roots and other disturbances, and the periods and phases of the oscillations may vary. As a consequence, biological control
by members of a single trophic group or species may never be complete, as pathogens will encounter varying populations of
the biocontrol agent on the root surface. A mixture of different trophic groups may provide more complete biological control
because peaks of different trophic groups occur at subsequent locations along a root. Alternatively, regular addition of soil
organic matter may increase background levels of microbial activity, increase nutrient cycling, lower the concentrations of
easily available nutrient sources, increase microbial diversity, and enhance natural disease suppression. 相似文献
99.
Background
The pH is an important parameter controlling many metabolic and signalling pathways in living cells. Recombinant fluorescent pH indicators (pHluorins) have come into vogue for monitoring cellular pH. They are derived from the most popular Aequorea victoria GFP (Av-GFP). Here, we present a novel fluorescent pH reporter protein from the orange seapen Ptilosarcus gurneyi (Pt-GFP) and compare its properties with pHluorins for expression and use in plants. 相似文献100.
Wolfgang R Engelsberger Alexander Erban Joachim Kopka Waltraud X Schulze 《Plant methods》2006,2(1):14-11
Strategies for robust quantitative comparison between different biological samples are of high importance in experiments that
address biological questions beyond the establishment of protein lists. Here, we propose the use of 15N-KNO3 as the only nitrogen source in Arabidopsis cell cultures in order to achieve a metabolically fully labeled cell population.
Proteins from such metabolically labeled culture are distinguishable from unlabeled protein populations by a characteristic
mass shift that depends on the amino acid composition of the tryptic peptide analyzed. In addition, the metabolically labeled
cell extracts are also suitable for comparative quantitative analysis of nitrogen-containing cellular metabolic complement.
Protein extracts from unlabeled and from standardized 15N-labeled cells were combined into one sample for joined analytical processing. This has the advantage of (i) reduced experimental
variability and (ii) immediate relative quantitation at the level of single extracted peptide and metabolite spectra. Together
ease and accuracy of relative quantitation for profiling experiments is substantially improved. The metabolic labeling strategy
has been validated by mixtures of protein extracts and metabolite extracts from the same cell cultures in known ratios of
labeled to unlabeled extracts (1:1, 1:4, and 4:1). We conclude that saturating metabolic 15N-labeling provides a robust and affordable integrative strategy to answer questions in quantitative proteomics and nitrogen
focused metabolomics. 相似文献