全文获取类型
收费全文 | 1238篇 |
免费 | 62篇 |
国内免费 | 1篇 |
专业分类
林业 | 81篇 |
农学 | 62篇 |
基础科学 | 4篇 |
163篇 | |
综合类 | 82篇 |
农作物 | 59篇 |
水产渔业 | 129篇 |
畜牧兽医 | 607篇 |
园艺 | 13篇 |
植物保护 | 101篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 21篇 |
2020年 | 18篇 |
2019年 | 31篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 35篇 |
2015年 | 35篇 |
2014年 | 44篇 |
2013年 | 78篇 |
2012年 | 60篇 |
2011年 | 82篇 |
2010年 | 39篇 |
2009年 | 35篇 |
2008年 | 69篇 |
2007年 | 72篇 |
2006年 | 79篇 |
2005年 | 66篇 |
2004年 | 64篇 |
2003年 | 64篇 |
2002年 | 47篇 |
2001年 | 35篇 |
2000年 | 46篇 |
1999年 | 35篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 5篇 |
排序方式: 共有1301条查询结果,搜索用时 718 毫秒
71.
Application of an airborne laser scanner to forest road design with accurate earthwork volumes 总被引:1,自引:0,他引:1
In this study we developed a forest road design program based on a high-resolution digital elevation model (DEM) from a light detection and ranging (LIDAR) system. After a designer has located the intersection points on a horizontal plane, the model first generates the horizontal alignment and the ground profile. The model precisely generates cross-sections and accurately calculates earthwork volumes using a high-resolution DEM. The model then optimizes the vertical alignment based on construction and maintenance costs using a heuristic technique known as tabu search. As the distance between cross-sections affects the accuracy of earthwork volume calculations, the results were examined by comparing them with the exact earthwork volume calculated by the probabilistic Monte Carlo simulation method. The earthwork volumes calculated by the Pappus-based method were similar to those calculated by the Monte Carlo simulation when the distance between cross-sections was within 10m. The model was applied to a high-resolution DEM from the LIDAR of Capitol Forest in Washington State, USA. The model generated a horizontal alignment, length 827m, composed of five horizontal curves. We examined the number of grade change points. The results indicated that tabu search found the best solution ($61.42/m) with five grade change points. This was composed of two vertical curves that almost followed the ground profile. As the accuracy of a high-resolution DEM from LIDAR increases, the model would become a useful tool for a forest road designer because it eliminates or at least reduces the time-consuming process of road surveys. 相似文献
72.
Sujan KC Yamamoto Hiroyuki Matsuo Miyuki Yoshida Masato Naito Kazuhiro Shirai Tatsuya 《Wood Science and Technology》2015,49(6):1157-1169
Wood Science and Technology - Tension wood, when kiln-dried, is likely to deform hugely, which is probably caused by a gelatinous layer of the gelatinous fiber. To elucidate the mechanism behind... 相似文献
73.
Surgical correction of gastro‐oesophageal intussusception with bilateral incisional gastropexy in three dogs
下载免费PDF全文
![点击此处可从《The Journal of small animal practice》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Three dogs presented for evaluation of acute onset tachypnoea and dyspnoea following episodes of vomiting and/or regurgitation. Thoracic radiographs were suggestive of a gastro‐oesophageal intussusception in all three dogs; one dog also showed evidence of aspiration pneumonia. All three dogs underwent surgical correction with a bilateral incisional gastropexy. All dogs recovered from anaesthesia uneventfully and were discharged from the hospital 3 days after presentation. Persistent megaoesophagus was evident in all three dogs, and they are being chronically managed with a strict feeding regime and pro‐motility agents. 相似文献
74.
Vitamin D Status in Different Stages of Disease Severity in Dogs with Chronic Valvular Heart Disease
下载免费PDF全文
![点击此处可从《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
T. Osuga K. Nakamura T. Morita S.Y. Lim K. Nisa N. Yokoyama N. Sasaki K. Morishita H. Ohta M. Takiguchi 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2015,29(6):1518-1523
Background
In humans with heart disease, vitamin D deficiency is associated with disease progression and a poor prognosis. A recent study showed that serum 25‐hydroxyvitamin D [25(OH)D] concentration, the hallmark of vitamin D status, was lower in dogs with heart failure than in normal dogs, and a low concentration was associated with poor outcome in dogs with heart failure.Objectives
To elucidate the vitamin D status of dogs with chronic valvular heart disease (CVHD) at different stages of disease severity.Animals
Forty‐three client‐owned dogs with CVHD.Methods
In this cross‐sectional study, dogs were divided into 3 groups (14 dogs in Stage B1, 17 dogs in Stage B2, and 12 dogs in Stage C/D) according to ACVIM guidelines. Dogs underwent clinical examination including echocardiography. Serum 25(OH)D concentrations were measured in each dog.Results
Serum 25(OH)D concentration was significantly lower in Stage B2 (median, 33.2 nmol/L; range, 4.9–171.7 nmol/L) and C/D (13.1 nmol/L; 4.9–58.1 nmol/L) than in Stage B1 (52.5 nmol/L; 33.5–178.0 nmol/L) and was not significantly different between Stage B2 and Stage C/D. Among clinical variables, there were significant negative correlations between 25(OH)D concentration and both left atrial‐to‐aortic root ratio and left ventricular end‐diastolic diameter normalized for body weight.Conclusions and Clinical Importance
These results indicate that vitamin D status is associated with the degree of cardiac remodeling, and the serum 25(OH)D concentration begins to decrease before the onset of heart failure in dogs with CVHD. 相似文献75.
Kazuhiro WATANABE Kotaro HAYASHI Saku KIJIMA Chie NONAKA Kazuaki YAMAZOE 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(10):1323-1325
In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle
dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs
were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily
brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were
collected from the buccal surface of the maxillary fourth premolars of the dogs
immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the
study, the number of bacteria was significantly lower in the SB and SPB groups compared
with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial
growth in the dogs. 相似文献
76.
77.
78.
79.
As the cultivars of rice markedly affect eating quality, processing suitability, and price, identification or differentiation of rice cultivar is very important. We developed suitable 14 STS (sequence-tagged site) primers for PCR (polymerase chain reaction), and it became possible to differentiate 60 Japanese dominant rice cultivars from each other using template DNA extracted and purified from rice grains. A multiplex primer set was shown to be useful to effectively differentiate rice cultivars produced in various countries by PCR. A novel multiplex primer set for PCR has been developed to differentiate KoshihikariBL, which is closely related with the premium cultivar, Koshihikari, in Japan. The application of the cultivar identification method by PCR method to commercially processed rice products was investigated. We developed an enzyme treatment method, in which the gelatinized starch is decomposed by the heat-stable alpha-amylase at 80 degrees C, followed by the hydrolysis of proteins by proteinase K with sodium dodecyl sulfate and purification of extracted DNAs by phenol/chloroform/iso-amyl alcohol. It became possible to identify the material rice cultivars of the commercially processed rice products, such as cooked rice, rice cake, or rice cracker, by a PCR method using template DNA prepared by the enzyme treatment method and novel multiplex primer sets. 相似文献
80.
Nakamura T Yoshida A Komatsuzaki N Kawasumi T Shima J 《Journal of agricultural and food chemistry》2007,55(12):4871-4876
To investigate a sourdough-specific peptide, low molecular weight peptides were extracted from sourdough. The peptide fraction was subjected to two kinds of chromatography to separate the peptides. Reverse-phase chromatography of the peptide fraction in the sourdough showed certain specific peptides. The specific peptide fraction was further separated by gel filtration chromatography. Liquid chromatography tandem mass spectrometry analysis identified one of the peptides as VPFGVG (six-mer). This sequence was estimated to occur at the 287-292 position of a low molecular weight glutenin subunit. The peptide (designed as SDP1) was produced by proteases derived from wheat flour. SDP1 showed angiotensin-converting enzyme (ACE) inhibitory activity, and the 50% inhibitory peptide concentration (IC50) was 336 microM. It is possible that the SDP1 peptide partially confers ACE inhibitory activity in sourdough. 相似文献