全文获取类型
收费全文 | 10023篇 |
免费 | 706篇 |
国内免费 | 46篇 |
专业分类
林业 | 803篇 |
农学 | 396篇 |
基础科学 | 96篇 |
2617篇 | |
综合类 | 404篇 |
农作物 | 573篇 |
水产渔业 | 1011篇 |
畜牧兽医 | 3857篇 |
园艺 | 218篇 |
植物保护 | 800篇 |
出版年
2023年 | 66篇 |
2022年 | 110篇 |
2021年 | 218篇 |
2020年 | 219篇 |
2019年 | 236篇 |
2018年 | 382篇 |
2017年 | 418篇 |
2016年 | 400篇 |
2015年 | 327篇 |
2014年 | 405篇 |
2013年 | 655篇 |
2012年 | 741篇 |
2011年 | 766篇 |
2010年 | 434篇 |
2009年 | 429篇 |
2008年 | 608篇 |
2007年 | 589篇 |
2006年 | 480篇 |
2005年 | 422篇 |
2004年 | 442篇 |
2003年 | 408篇 |
2002年 | 309篇 |
2001年 | 259篇 |
2000年 | 258篇 |
1999年 | 224篇 |
1998年 | 72篇 |
1997年 | 54篇 |
1996年 | 45篇 |
1995年 | 56篇 |
1994年 | 31篇 |
1993年 | 28篇 |
1992年 | 45篇 |
1991年 | 42篇 |
1990年 | 43篇 |
1989年 | 59篇 |
1988年 | 28篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 36篇 |
1984年 | 23篇 |
1983年 | 26篇 |
1980年 | 15篇 |
1979年 | 26篇 |
1978年 | 18篇 |
1976年 | 18篇 |
1973年 | 18篇 |
1972年 | 14篇 |
1968年 | 14篇 |
1967年 | 15篇 |
1966年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
M. Muoz‐Rojas A. Jordn L. M. Zavala D. De la Rosa S. K. Abd‐Elmabod M. Anaya‐Romero 《Land Degradation \u0026amp; Development》2015,26(2):168-179
During the last few decades, land use changes have largely affected the global warming process through emissions of CO2. However, C sequestration in terrestrial ecosystems could contribute to the decrease of atmospheric CO2 rates. Although Mediterranean areas show a high potential for C sequestration, only a few studies have been carried out in these systems. In this study, we propose a methodology to assess the impact of land use and land cover change dynamics on soil organic C stocks at different depths. Soil C sequestration rates are provided for different land cover changes and soil types in Andalusia (southern Spain). Our research is based on the analysis of detailed soil databases containing data from 1357 soil profiles, the Soil Map of Andalusia and the Land Use and Land Cover Map of Andalusia. Land use and land cover changes between 1956 and 2007 implied soil organic C losses in all soil groups, resulting in a total loss of 16·8 Tg (approximately 0·33 Tg y−1). Afforestation increased soil organic C mostly in the topsoil, and forest contributed to sequestration of 8·62 Mg ha−1 of soil organic C (25·4 per cent). Deforestation processes implied important C losses, particularly in Cambisols, Luvisols and Vertisols. The information generated in this study will be a useful basis for designing management strategies for stabilizing the increasing atmospheric CO2 concentrations by preservation of C stocks and C sequestration. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
52.
David Santiago‐Ramos Juan de Dios Figueroa‐Crdenas Jos Juan Vles‐Medina Rosalía Reynoso‐Camacho Minerva Ramos‐Gmez Marcela Gaytn‐Martínez Eduardo Morales‐Snchez 《Cereal Chemistry》2015,92(5):475-480
The objective of the present work was to study the effect of annealing and concentration of Ca(OH)2 (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (To, Tp, and Tf) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl2 > CaSO4 > Ca(OH)2 ≈ CaCO3. This behavior was because of the dissociation of each salt or lime in water. Anions (OH−) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose‐lipid complexes were formed during the nixtamalization processes, as indicated by an increasing peak at 4.5 Å in X‐ray diffraction patterns. 相似文献
53.
54.
Analgesic efficacy of an oral transmucosal spray formulation of meloxicam alone or in combination with tramadol in cats with naturally occurring osteoarthritis
下载免费PDF全文
![点击此处可从《Veterinary anaesthesia and analgesia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
55.
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)
56.
57.
58.
C. Ekstrand C. Ingvast‐Larsson L. Olsén M. Hedeland U. Bondesson J. Gabrielsson 《Journal of veterinary pharmacology and therapeutics》2016,39(3):255-263
The cortisol response to glucocorticoid intervention has, in spite of several studies in horses, not been fully characterized with regard to the determinants of onset, intensity and duration of response. Therefore, dexamethasone and cortisol response data were collected in a study applying a constant rate infusion regimen of dexamethasone (0.17, 1.7 and 17 μg/kg) to six Standardbreds. Plasma was analysed for dexamethasone and cortisol concentrations using UHPLC‐MS/MS. Dexamethasone displayed linear kinetics within the concentration range studied. A turnover model of oscillatory behaviour accurately mimicked cortisol data. The mean baseline concentration range was 34–57 μg/L, the fractional turnover rate 0.47–1.5 1/h, the amplitude parameter 6.8–24 μg/L, the maximum inhibitory capacity 0.77–0.97, the drug potency 6–65 ng/L and the sigmoidicity factor 0.7–30. This analysis provided a better understanding of the time course of the cortisol response in horses. This includes baseline variability within and between horses and determinants of the equilibrium concentration–response relationship. The analysis also challenged a protocol for a dexamethasone suppression test design and indicated future improvement to increase the predictability of the test. 相似文献
59.
Anatomical Variations of the Blood Vascular System in Veterinary Medicine. The Internal Iliac Artery of the Dog. Part Two
下载免费PDF全文
![点击此处可从《Anatomia, histologia, embryologia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The aim of this study was to investigate the variability of the internal pudendal artery. Two hundred and thirty‐two pelvic halves from 116 adult dogs were examined. Twenty‐six anatomical variations were found, thirteen occurring in more than 5% of the dogs. Anatomical variations were grouped in relation to the origin of the prostatic/vaginal arteries, middle rectal artery, urethral artery, ventral perineal and caudal rectal arteries. The chi‐squared test was used to analyse differences in sex, side of the body, profile and size, and the results were considered statistically significant when P ≤ 0.05. An identical vascular pattern in both hemipelvises was found for most of the anatomical variations described. 相似文献
60.
Anatomical Variations of the Blood Vascular System in Veterinary Medicine: The Internal Iliac Artery of the Dog — Part Three
下载免费PDF全文
![点击此处可从《Anatomia, histologia, embryologia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The aim of this study was to analyse and describe the variability of the umbilical artery. Two hundred and thirty‐two pelvic halves from 116 adult dogs were examined. To study the permeability of the umbilical artery, ten adult dogs, nine newborns and thirteen foetuses between 35 and 50 days of gestation were also used. In relation to the origin of the umbilical artery, six anatomical variations were found. From which five involved a cranial (n = 4) or caudal (n = 1) relocation of its origin, and in one case (n = 1), the umbilical artery arose from the median sacral artery. In eight cases, the umbilical artery gave off the prostatic (n = 1) or vaginal (n = 7) arteries. The permeability of the umbilical artery was the most significant anatomical variation: permeability was detected in 45% (106 of 232 pelvic halves) of all cases, from which 36 were males and 70 females. Interestingly, an equal vascular permeability in both hemipelvises was found for 82% of the dogs, thus additional data related to such feature of the umbilical artery was also recorded. In accordance with the statistical study, the main anatomical variations described showed significant values for gender, side of the body, size and profile variables. 相似文献