全文获取类型
收费全文 | 856篇 |
免费 | 101篇 |
专业分类
林业 | 50篇 |
农学 | 17篇 |
基础科学 | 4篇 |
124篇 | |
综合类 | 46篇 |
农作物 | 55篇 |
水产渔业 | 91篇 |
畜牧兽医 | 470篇 |
园艺 | 13篇 |
植物保护 | 87篇 |
出版年
2023年 | 15篇 |
2022年 | 22篇 |
2021年 | 47篇 |
2020年 | 47篇 |
2019年 | 69篇 |
2018年 | 51篇 |
2017年 | 60篇 |
2016年 | 54篇 |
2015年 | 35篇 |
2014年 | 36篇 |
2013年 | 63篇 |
2012年 | 44篇 |
2011年 | 69篇 |
2010年 | 38篇 |
2009年 | 54篇 |
2008年 | 40篇 |
2007年 | 30篇 |
2006年 | 30篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 21篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1984年 | 1篇 |
排序方式: 共有957条查询结果,搜索用时 46 毫秒
1.
Do cover crops change the lability of phosphorus in a clayey subtropical soil under different phosphate fertilizers?
下载免费PDF全文
![点击此处可从《Soil Use and Management》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A. P. B. Teles M. Rodrigues W. F. Bejarano Herrera A. Soltangheisi L. R. Sartor P. J. A. Withers P. S. Pavinato 《Soil Use and Management》2017,33(1):34-44
Plants have developed different mechanisms to absorb and solubilize phosphorus (P) in the soil, especially in environments with low P availability. This study evaluated the effects of different winter cover crops on soil P availability in a clayey subtropical (Hapludox) soil receiving soluble P fertilizer and a rock phosphate applied to the summer crop, under no‐tillage. The experiment was carried out over 3 yrs (2009–2011) with five different cover crop species: common vetch, fodder radish, ryegrass, black oat, white clover and fallow as control. The soil was sampled after the third year of cover crop cultivation and analysed for inorganic and organic P forms according to the well‐established Hedley fractionation procedure. Phosphate fertilizers promoted accumulation of both labile and nonlabile P pools in soil in the near surface layer, especially under rock phosphate. Fertilizer applications were not able to change P fractions in deeper layers, emphasizing that the Brazilian clayey soils are a sink of P from fertilizer and its mobility is almost nil. Although the cover crops recycled a great amount of P in tissue, in a short‐term evaluation (3 yrs) they only changed the content of moderately labile P in soil, indicating that long‐term studies are needed for more conclusive results. 相似文献
2.
In mid-September, 1 month before the insertion of intravaginal pessaries to induce sexual activity, blood samples were collected every 4 days from 16 ewe lambs aged 7 months, in order to determine the incidence of ovulations by measurement of plasma progesterone concentrations. It has been studied whether the response to a progestagen treatment of ewe lambs apparently close to puberty could be modified by the onset of the ovarian events preceding puberty. The effect of the presence or absence of ovulations prior to progestagen treatment on the potential reproductive performance (fertility, litter size and fecundity), embryo development [embryo quality and interferon-tau (IFNτ) secretion], luteal function (progesterone secretion in vitro ) and endometrial progesterone content was studied in seven ovulating (Ov+) and nine nonovulating ewe lambs (Ov−) on day 14 after mating. The best potential reproductive results were obtained with Ov+ animals, although these differences could not be initially attributed to either different progesterone secretion in vitro or concentration of endometrial progesterone. Irrespective of the experimental groups, secretion of progesterone by luteal tissue from ewe lambs with normal embryos was significantly greater (p<0.05) than that of animals with abnormal embryos or with no embryos. Normal embryos secreted a higher amount of IFN-τ than those embryos classified as abnormal (p<0.07). In conclusion, ewe lambs which exhibit luteal activity before puberty have the highest levels of reproductive performances after a progestagen treatment. Corpora lutea from ewe lambs with normal embryos had higher rates of progesterone secretion in vitro and their embryos had a higher IFN-τ production by the embryos, indicating greater capacity for subsequent development. 相似文献
3.
4.
Paula de Aguiar Silva Gleidson Giordano Pinto de Carvalho Aureliano José Vieira Pires Stefanie Alvarenga Santos Douglas dos Santos Pina Robério Rodrigues Silva Carlindo Santos Rodrigues Luis Henrique Almeida de Matos Carlos Emanuel Eiras Daiane Novais-Eiras Wilson Souza Nunes 《Tropical animal health and production》2018,50(4):721-726
In this study, we evaluated the effects of including cassava wastewater in the diet on the feeding behavior of feedlot lambs in 35 male uncastrated Santa Inês × Dorper crossbred lambs at an approximate age of 3 months, with an average live weight of 20.0?±?3.4 kg. Diets were formulated with hay of cassava shoots (roughage) and a concentrate based on corn and soybean, with a roughage:concentrate ratio of 50:50, plus inclusion of cassava wastewater at the levels of 0, 12, 24, 36, or 48 g/kg of the total diet. Feeding behavior was evaluated between the 46th and 52nd days of the experiment. Increasing cassava wastewater levels in the diet reduced (P?<?0.05) the intakes (kg/day) of dry matter and neutral detergent fiber as well as the efficiency of rumination (g/cud and g/h) of dry matter and neutral detergent fiber. The other behavioral parameters were not affected by wastewater inclusion in the diet. Therefore, the inclusion of up to 48 g/kg of cassava wastewater on fresh matter of diets is not recommended for feedlot lambs. 相似文献
5.
Interactions between different media and follicle‐stimulating hormone supplementation on in vitro culture of preantral follicles enclosed in ovarian tissue derived from collared peccaries (Pecari tajacu Linneaus, 1758)
下载免费PDF全文
![点击此处可从《Reproduction in domestic animals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
GL Lima VB Luz LF Lima RMP Rocha SV Castro TS Castelo APR Rodrigues JR Figueiredo AR Silva 《Reproduction in domestic animals》2018,53(4):880-888
The aim was to verify the effect of follicle‐stimulating hormone (FSH) supplementation to α‐MEM+ or TCM199+ media on the in vitro development of ovarian preantral follicles (PFs) derived from collared peccaries. Ovaries (n = 5 pairs) were collected and divided into fragments destined to control group (non‐cultured) or treatments that were cultured for 7 days. The PFs morphology, growth and activation were evaluated by classical histology. The immunohistochemistry markers Ag‐NOR and PCNA were used for nuclear proliferation analysis, and the picrosirius red labelling was used for ovarian extracellular matrix (ECM) evaluation. After 7‐day culture, only the TCM199+ treatment maintained the proportion of intact PFs similar to day 1 (63.2%), but no differences were found among treatments (p > .05). In addition, a significant increase in the growing follicles proportion was verified for all the treatments, indicating follicular activation (p > .05). By the Ag‐NOR analysis, only the TCM199+/FSH maintained the nuclear proliferation similar to the first day (p > .05). The picrosirius red staining revealed that the ECM remained intact in all the treatments (p > .05). We suggest the use of TCM199+ medium supplemented of FSH for the in vitro development of peccaries PFs under 7‐day culturing conditions. 相似文献
6.
Objective To establish the prevalence of intussusceptions involving the caecum in a population of horses admitted to a university hospital for colic. Design Retrospective clinical study Methods Medical records of all horses admitted to the Massey University Veterinary Teaching Hospital between 1991 and 2004 were examined for information of those horses diagnosed with an intussusception involving the caecum. Results A total of 135 horses were admitted for colic surgery during the study period and 61 horses had a diagnosis of ileocaecal (37), caecocaecal (5) or caecocolic intussusception (19) made either at surgery or necropsy. Of the horses with ileocaecal intussusception, 32 had an incomplete hand-sewn ileocaecostomy without reduction and 29 survived to discharge. All the horses with caecocaecal intussusceptions were diagnosed preoperatively via rectal examination and/or transabdominal ultrasound: 2 were euthanased at surgery and 3 survived to discharge. In the 19 horses with caecocolic intussusceptions, manually reduction at surgery was performed in 6 and 5 of them survived to discharge. A typhlectomy was performed via a colotomy in 6 horses, 3 of which survived to discharge. Conclusions The high prevalence of intussusceptions involving the caecum seen at this referral centre may indicate a higher prevalence in New Zealand than is reported elsewhere in the world. Clinical relevance Intussusceptions involving the caecum should be considered as a differential diagnosis in horses presenting with chronic low-grade colic. Transabdominal ultrasound is useful for identifying caecocaecal and caecocolic intussusceptions. Hand-sewn side-to-side incomplete ileocaecostomy is a quick, effective and safe method of surgical treatment of ileocaecal intussusceptions. 相似文献
7.
Lucas T. Rodrigues Lorenzo GTM Segabinazzi Sidnei N Oliveira Mariana Frasson Frederico O Papa 《Reproduction in domestic animals》2021,56(11):1470-1474
Pregnancy rates after embryo transfer (ET) are disappointing in donkey species. This study aims to report two successful ET of mini-donkey embryos using Brazilian Northeastern jennies as recipients. Eighteen embryo flushes were performed 9 days post-ovulation in two non-pregnant mini-donkeys jennies (11 and 7 cycles per jenny). Eleven embryos (61%, 11/18) were collected and transferred to Brazilian Northeastern jennies 4–6 days post-ovulation by conventional (n = 6) or an alternative (n = 5) technique. The alternative method consisted of inserting a Polansky equine vaginal speculum smeared with lubricant in the vagina of the recipient jenny. The arms of the speculum were extended to allow the visualization of the cervix. Then, using an adapted crafted, elongated, toothed tissue grasping forceps, the external cervical os was held, and the cervix was gently pulled backward, aiming to straight the cervical canal. The ET gun was inserted through the vagina and cervix by visual inspection, and the embryo was released into the uterine lumen. All embryos collected were Grade 1 and classified as Expanded Blastocysts. No jennies become pregnant after conventional ET (0/6), whereas two recipient jennies (40%, 2/5) become pregnant and delivered offspring in the following year after ET using the alternative technique. In conclusion, Brazilian Northeastern jennies can be used as embryo recipients using the alternative method proposed in the present study. However, further investigations are needed to improve the knowledge and results of ET in donkey species. 相似文献
8.
André Guimarães Maciel e Silva Suely Cristina Gomes de Lima Pedro Danilo de Oliveira Michel dos Santos Moraes Célia Maria Costa Guimarães Jamile Andréa Rodrigues da Silva Alexandre Rossetto Garcia Benjamim de Souza Nahúm Lilaine de Sousa Neres Gerlane Nunes Noronha José de Brito Lourenço Júnior 《Animal Science Journal》2021,92(1):e13576
The objective was to evaluate the effect of concentrate supplementation using by-products of the Amazonian industry on milk production, milk composition, and milk fatty acid profile of dairy buffaloes. Twelve lactating buffaloes (544.5 ± 35.6 kg, 6.4 ± 2.2 years old, 59 ± 6 days in milk) were allotted in a pasture of Mombaça grass and managed under rotational grazing (4 days occupancy/28 days rest). A 3 × 3 Latin square was adopted, and each animal alternately received three supplementary treatments based on corn bran + soybean meal or cupuaçu cake or murumuru cake for 21 days per treatment. Murumuru cake increased the levels of lauric acid and myristic acid in the milk (p < 0.05). Murumuru cake reduced the unsaturated fatty acid contents in the milk compared with animals fed control diet or cupuaçu cake (24.27% vs. 25.24% vs. 25.08%). The n-6/n-3 ratio was 2.6, 1.97, and 2.0 in the control, cupuaçu, and murumuru groups, respectively. Based on this parameter, cakes made from cupuaçu as well as murumuru could be considered to be adequate for inclusion in dairy water buffalo feed. However, the murumuru cake addition requires some caution because its use induces the secretion of higher levels of lauric and myristic fatty acids that are related to human cardiovascular disease. 相似文献
9.
Polymethylmethacrylate orbital implants with interconnecting channels. A retrospective study following enucleation in dogs and cats
下载免费PDF全文
![点击此处可从《Veterinary ophthalmology》网站下载免费的PDF全文](/ch/ext_images/free.gif)