全文获取类型
收费全文 | 1830篇 |
免费 | 82篇 |
国内免费 | 3篇 |
专业分类
林业 | 160篇 |
农学 | 271篇 |
基础科学 | 27篇 |
369篇 | |
综合类 | 63篇 |
农作物 | 118篇 |
水产渔业 | 79篇 |
畜牧兽医 | 596篇 |
园艺 | 75篇 |
植物保护 | 157篇 |
出版年
2023年 | 13篇 |
2022年 | 30篇 |
2021年 | 44篇 |
2020年 | 49篇 |
2019年 | 34篇 |
2018年 | 81篇 |
2017年 | 74篇 |
2016年 | 79篇 |
2015年 | 45篇 |
2014年 | 50篇 |
2013年 | 142篇 |
2012年 | 67篇 |
2011年 | 88篇 |
2010年 | 78篇 |
2009年 | 60篇 |
2008年 | 90篇 |
2007年 | 75篇 |
2006年 | 59篇 |
2005年 | 48篇 |
2004年 | 39篇 |
2003年 | 43篇 |
2002年 | 49篇 |
2001年 | 33篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 20篇 |
1991年 | 20篇 |
1990年 | 38篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 12篇 |
1970年 | 8篇 |
1969年 | 16篇 |
1968年 | 12篇 |
排序方式: 共有1915条查询结果,搜索用时 15 毫秒
1.
2.
3.
Madhu Aneja Thomas J. Gianfagna Prakash K. Hebbar 《Physiological and Molecular Plant Pathology》2005,67(6):1647
An isolate of Trichoderma harzianum Rifai from an infected cacao pod produces and secretes nonanoic (pelargonic) acid into a liquid culture medium. Nonanoic acid (NA) was very inhibitory to spore germination and mycelial growth of two cacao pathogens, Crinipellis perniciosa Stahel and Moniliophthora roreri Cif. H.C. Evans. It was highly active causing 75% inhibition of spore germination in an in vitro assay at a rate as low as 0.09 μM for M. roreri and 0.92 μM for C. perniciosa. Mycelial growth was comparatively less sensitive to inhibition, but still there was a 75% reduction in growth with 0.62 μM in M. roreri and 151 μM NA in C. perniciosa. In contrast, NA did not affect Trichoderma mycelial growth or spore germination at concentrations that were inhibitory to the pathogens. 6-pentyl-α-pyrone was also produced and secreted into the medium by T. harzianum, however; it was not antagonistic to the cacao pathogens. Although a number of metabolites produced by Trichoderma spp. have been identified in the past, this is the first report of NA production and secretion by any Trichoderma. The results suggest that NA may play a role in the successful use of some Trichoderma spp. isolates in the biocontrol of fungal diseases of plants. 相似文献
4.
5.
Computed Tomographic Angiography of the Pancreas in Cats with Chronic Diabetes Mellitus Compared to Normal Cats 下载免费PDF全文
S. Secrest A. Sharma A. Bugbee 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2018,32(3):962-966
Background
Diabetes mellitus (DM) is a common endocrinopathy in cats. No known diagnostic test or patient characteristic at the time of diagnosis can predict likely disease course, unlike in people in whom computed tomographic angiography (CTA) is used. No published data exist regarding the CTA appearance of the pancreas in cats with DM, and thus, it is unknown what if any CTA variables should be further assessed for associations with pancreatic endocrine function.Hypothesis/Objectives
A significant difference in pancreatic attenuation, volume, and size will be identified between normal cats and those with chronic DM on CTA.Animals
Ten healthy control cats and 15 cats with naturally occurring DM present for >12 months.Methods
Prospective cross‐sectional study comparing pancreatic attenuation, enhancement pattern, size, volume, pancreatic volume‐to‐body weight ratio (V:BW), pancreatic arterial: portal phase ratio (A:P), time‐to‐arterial enhancement, and time‐to‐peak portal enhancement on CTA between sedated healthy control cats and those with chronic DM.Results
The pancreas in cats with chronic DM was significantly larger, had higher volume, higher V:BW, and shorter time‐to‐peak portal enhancement on CTA when compared to normal cats.Conclusions and Clinical Importance
Peak portal enhancement time, pancreatic size, pancreatic volume, and V:BW can be used to differentiate normal sedated cats from those with chronic DM by CTA. These variables warrant further investigation to identify possible associations with endocrine function. 相似文献6.
7.
S. Shanmugam K. H. Kjaer C.‐O. Ottosen E. Rosenqvist D. Kumari Sharma B. Wollenweber 《Journal of Agronomy and Crop Science》2013,199(5):340-350
This study analysed the alleviating effect of elevated CO2 on stress‐induced decreases in photosynthesis and changes in carbohydrate metabolism in two wheat cultivars (Triticum aestivum L.) of different origin. The plants were grown in ambient (400 μl l?1) and elevated (800 μl l?1) CO2 with a day/night temperature of 15/10 °C. At the growth stages of tillering, booting and anthesis, the plants were subjected to heat stress of 40 °C for three continuous days. Photosynthetic parameters, maximum quantum efficiency of photosystem II (PSII) photochemistry (Fv/Fm) and contents of pigments and carbohydrates in leaves were analysed before and during the stress treatments as well as after 1 day of recovery. Heat stress reduced PN and Fv/Fm in both wheat cultivars, but plants grown in elevated CO2 maintained higher PN and Fv/Fm in comparison with plants grown in ambient CO2. Heat stress reduced leaf chlorophyll contents and increased leaf sucrose contents in both cultivars grown at ambient and elevated CO2. The content of hexoses in the leaves increased mainly in the tolerant cultivar in response to the combination of elevated CO2 and heat stress. The results show that heat stress tolerance in wheat is related to cultivar origin, the phenological stage of the plants and can be alleviated by elevated CO2. This confirms the complex interrelation between environmental factors and genotypic traits that influence crop performance under various climatic stresses. 相似文献
8.
Keneisenuo Keneisenuo MVSc Om Prakash Choudhary PhD Pranab Chandra Kalita PhD Priyanka Choudhary PhD Arup Kalita PhD Probal Jyoti Doley MVSc Jitendra Kumar Chaudhary PhD 《Anatomia, histologia, embryologia》2021,50(3):500-511
The present study reports data on the skull bone morphometry of barking and sambar deer. The skulls of adult barking deer (n = 6) and sambar deer (n = 6) of either sex (n = 3 males and n = 3 females) were collected from the Aizawl Zoological Park, Aizawl, Mizoram, India, with official permission from the Government of Mizoram. Anatomically, barking and sambar deer's skulls were elongated, pyramid-like, dolichocephalic and consisted of thirty-two cranial and facial bones. The cranial bones were eleven (three single and four paired), comprising of occipital, sphenoid, ethmoid, frontal, interparietal, parietal and temporal. The facial bones were twenty-one (one single and ten were paired), consisting of the maxilla, premaxilla (incisive), palatine, pterygoid, nasal, lacrimal, zygomatic (malar), vomer, turbinates, mandible and hyoid. In the present study, altogether 41 different measurements were taken morphologically and 6 different indices were applied. The obtained morphometrical parameters were significantly (p < .01, p < .05) higher in males than females of both species. Species wise, all obtained parameters were higher in sambar deer than barking deer. The obtained 41 different skull parameters and 6 indices showed statistically significant differences (p < .01 and p < .05) between both sexes of barking and sambar deer; however, practically these differences were meagre. The present morphometrical study on the skull of both species can help the wildlife professionals and zoo veterinarians determine the sex of these animals and differentiate it from other domestic and wild small ruminants for solving veterolegal cases. This study's findings will also motivate and assist other comparative studies with various domestic and wild small ruminants. 相似文献
9.
Identification of internal control genes in milk‐derived mammary epithelial cells during lactation cycle of Indian zebu cow 下载免费PDF全文
10.
Canine influenza virus is an emerging, highly contagious, respiratory pathogen that has not previously been radiographically described. In this retrospective case series study, we describe the thoracic radiographic appearance of confirmed canine influenza virus in six dogs. Radiographic findings varied, but included abnormal unstructured interstitial (one) and unstructured interstitial and alveolar (five) pulmonary patterns, which were distributed cranioventral (four), diffuse (one), and caudodorsal (one). The right middle (five), left cranial (five), and right cranial (four) lung lobes were most commonly affected. Additionally, mild pleural effusion was present in one dog. Intrathoracic lymphadenopathy and cranial mediastinal widening/fluid accumulation were not detected in any dog. Canine influenza virus should be considered as a differential diagnosis for canine patients with respiratory signs and a cranioventral unstructured interstitial to alveolar pulmonary pattern. 相似文献