全文获取类型
收费全文 | 899篇 |
免费 | 53篇 |
专业分类
林业 | 81篇 |
农学 | 38篇 |
基础科学 | 3篇 |
248篇 | |
综合类 | 56篇 |
农作物 | 102篇 |
水产渔业 | 83篇 |
畜牧兽医 | 231篇 |
园艺 | 18篇 |
植物保护 | 92篇 |
出版年
2023年 | 13篇 |
2022年 | 34篇 |
2021年 | 48篇 |
2020年 | 48篇 |
2019年 | 31篇 |
2018年 | 32篇 |
2017年 | 34篇 |
2016年 | 42篇 |
2015年 | 36篇 |
2014年 | 39篇 |
2013年 | 46篇 |
2012年 | 63篇 |
2011年 | 76篇 |
2010年 | 46篇 |
2009年 | 41篇 |
2008年 | 47篇 |
2007年 | 64篇 |
2006年 | 38篇 |
2005年 | 38篇 |
2004年 | 26篇 |
2003年 | 32篇 |
2002年 | 23篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有952条查询结果,搜索用时 15 毫秒
941.
D'Angelo A Maurella C Bona C Borrelli A Caramelli M Elena Careddu M Jaggy A Ru G 《Veterinary journal (London, England : 1997)》2007,174(1):106-112
A reliable ante-mortem test for the detection of scrapie in all genotypes has not yet been developed and clinical diagnosis remains a useful tool for surveillance purposes. This paper describes the results of a three-year study in which clinical signs consistent with scrapie were recorded according to standardized criteria in 245 sheep from 21 outbreaks in Italy in order to identify helpful criteria for the diagnosis of the disease. Thirty-seven sheep were scrapie-positive at post-mortem rapid testing, 23 showed weight loss, 20 had proprioceptive deficits, 17 demonstrated ataxia and nibble reflex, and some sheep had a combination of signs. Six scrapie-positive sheep were asymptomatic. The clinical protocol was easy to handle and appears to be a useful tool for improving passive surveillance. The data suggested that positive clinical history, nibble, and nibble combined with proprioceptive positioning deficit have a quite high negative predictive value. The protocol will be proposed as a tool for field inspection in passive surveillance in Italy. 相似文献
942.
943.
944.
945.
Matteo Tesi Vincenzo Miragliotta Lorenza Scala Elisa Aronica Giulia Lazzarini Diana Fanelli Alessandra Rota Francesca Abramo 《Reproduction in domestic animals》2021,56(5):691-702
The canine placenta is an underexamined organ. Placental abnormalities can affect foetus development and may be responsible for a low weight of the infant at birth; however, knowledge on their clinical significance in the canine species is limited. We aimed to describe macroscopic and microscopic findings in the canine placenta and amnion at term in clinically uncomplicated pregnancies and to evaluate their relationship with birth weight of healthy puppies. During natural delivery or C-section, the birth weight of 82 puppies was recorded, 72 placentas and 66 amnions were recovered. The foetal and maternal surfaces of the placental girdle, marginal haematoma and amnion were evaluated. Each gross finding was recorded, morphometrically assessed and sampled for histological diagnosis. Furthermore, specimens of placenta and amnion were collected from representative areas and microscopic deviations from normal structure were evaluated in haematoxylin and eosin sections. Gross examination revealed ‘abnormalities’ in the 75.4% of the collected placentas. Necrosis was the gross change most commonly observed in the placental girdle (72.5%). Congestion (17.4%) and clotted blood/fibrinoid material (2.9%) were also observed. No gross changes of either the marginal haematoma or the amnion were recorded. Histologically, placental girdle showed necrosis (62.3%), mineralization (52.2%), congestion (36.2%) and neutrophilic infiltration (27.5%). Marginal haematoma exhibited mineralization (11.6%) and neutrophils (29%), while necrotic foci were rarely observed (4.3%). In the amnion, the most frequent alteration observed was hypertrophy of the epithelium (35.9%) followed by oedema (31.2%), mineralized foci (28.1%), fibrosis (23.4%), congestion (15.6%) and more rarely neutrophils (12.5%). Puppies’ birth weight was not statistically affected by either gross or histological abnormalities. Our study revealed that macroscopic and microscopic ‘abnormalities’ of the placenta and amnion may be common in uncomplicated pregnancies at term; however, no implications on puppies’ birth weight were observed. Deviations from ‘normal’ morphology of canine foetal adnexa warrant further investigation to assess their clinical implications if present. 相似文献
946.
Juliana de Carvalho Delgado Thais Rose dos Santos Hamilton Camilla Mota Mendes Adriano Felipe Perez Siqueira Marcelo Demarchi Goissis José Buratini Mayra Elena Ortiz D’Ávila Assumpção 《Reproduction in domestic animals》2021,56(5):754-763
In vitro embryo production (IVP) efficiency is reduced when compared to in vivo. The basic knowledge of bovine in vitro oocyte maturation (IVM) mechanisms provides support to improve in vitro embryo production yields. The present study assessed the effects of bone morphogenetic protein 15 (BMP15), fibroblast growth factor 16 (FGF16) and their combined action on cumulus cells (CC) expansion, oocyte and CC DNA fragmentation, oocyte nuclear maturation, energetic metabolism and progesterone production in bovine IVM. Cumulus-oocyte complexes (COC) were matured in control or supplemented media containing BMP15 (100 ng/ml), FGF16 (10 ng/ml) or BMP15 combined with FGF16; and assessed at 0 and 22 hr of IVM. BMP15 alone or its association with FGF16 enhanced cumulus expansion. BMP15 decreased DNA fragmentation in both CC and oocytes, and improved oocyte nuclear maturation rate. In addition, BMP15 increased CC progesterone production, an effect not previously reported. The present study reinforces previous data pointing to a beneficial influence of BMP15 during IVM, while providing novel evidence that the underlying mechanisms involve increased progesterone production. 相似文献
947.
Three experiments were conducted to determine the influence of hotplate surface temperature (250, 300, 350, and 400°C), pasta‐to‐water ratio, and beaker material (glass versus stainless steel) on the final quality of cooked spaghetti. In all the experiments, 13, 20, 27, 33, and 48 g of pasta were cooked and its final quality measured as cooking loss, cooked weight, and cooked firmness. Cooking time was greater when cooked at 250 than 400°C, with 48 than 13 g of pasta, and with a glass than with a stainless steel vessel. Cooking loss, cooked weight, and cooked firmness were greater when cooked at 400 than 250°C, with 13 than 48 g of pasta, and with a stainless steel than with a glass vessel. Evidence of the effects of hotplate surface temperature, pasta‐to‐water ratio, and beaker material on pasta cooking time and cooked quality suggests that these parameters should be addressed in AACC International Approved Method 66‐50.01. 相似文献
948.
Sabine Fromm Elena Beißwanger Annemarie Käsbohrer Bernd-Alois Tenhagen 《Preventive veterinary medicine》2014
The importance of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) as an infectious agent for humans has increased in recent years in Germany. Although it is well known that the prevalence of MRSA in pig farms is high, risk factors for the presence of MRSA in herds of fattening pigs are still poorly understood. The aim of this study was to evaluate available data from previous studies on MRSA in fattening pigs in a meta-analysis to answer the question: What are the factors associated with the occurrence of MRSA in fattening pig herds? 相似文献
949.
It has been hypothesised that wheat yields may be increased by lengthening the duration of the stemelongation phase. This
paper reports studies on the effects of chromosomes carrying major photoperiod genes (Ppd-A1, Ppd-B1, Ppd-D1) in different genetic backgrounds, on responses to photoperiod before and after jointing, when the onset of stem elongation
occurs, and on number of grains per spike. A field experiment considered the effects of two photoperiods on Chinese Spring
and 12 substitution lines, in which chromosomes 2A, 2B or 2D had been substituted by those from four contrasting cultivars.
The phase from seedling emergence to jointing (EM-JO) was more responsive than that from jointing to anthesis (JO-ANT), but
no relationship was found between the duration of these phases. EM-JO length affected leaf and spikelet number and consequently
grains per spike, but this component was further influenced by JO-ANT duration. Our results confirmed that the phases are
independent in sensitivity, supporting the hypothesis that genetic manipulation of phase duration could enhance yield, but
no evidence was found of any particular Ppd allele being responsible for major responses to photoperiod during stem elongation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
950.
Interleukin-6 (IL-6) is an immunoregulatory cytokine that activates a cell-surface signaling assembly composed of IL-6, the IL-6 alpha-receptor (IL-6Ralpha), and the shared signaling receptor gp130. The 3.65 angstrom-resolution structure of the extracellular signaling complex reveals a hexameric, interlocking assembly mediated by a total of 10 symmetry-related, thermodynamically coupled interfaces. Assembly of the hexameric complex occurs sequentially: IL-6 is first engaged by IL-6Ralpha and then presented to gp130in the proper geometry to facilitate a cooperative transition into the high-affinity, signaling-competent hexamer. The quaternary structures of other IL-6/IL-12 family signaling complexes are likely constructed by means of a similar topological blueprint. 相似文献