全文获取类型
收费全文 | 441篇 |
免费 | 23篇 |
专业分类
林业 | 17篇 |
农学 | 11篇 |
基础科学 | 1篇 |
94篇 | |
综合类 | 38篇 |
农作物 | 26篇 |
水产渔业 | 34篇 |
畜牧兽医 | 169篇 |
园艺 | 32篇 |
植物保护 | 42篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 12篇 |
2017年 | 13篇 |
2016年 | 22篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 20篇 |
2012年 | 29篇 |
2011年 | 37篇 |
2010年 | 26篇 |
2009年 | 15篇 |
2008年 | 29篇 |
2007年 | 35篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 18篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有464条查询结果,搜索用时 31 毫秒
61.
Keller LP Bajt S Baratta GA Borg J Bradley JP Brownlee DE Busemann H Brucato JR Burchell M Colangeli L d'Hendecourt L Djouadi Z Ferrini G Flynn G Franchi IA Fries M Grady MM Graham GA Grossemy F Kearsley A Matrajt G Nakamura-Messenger K Mennella V Nittler L Palumbo ME Stadermann FJ Tsou P Rotundi A Sandford SA Snead C Steele A Wooden D Zolensky M 《Science (New York, N.Y.)》2006,314(5806):1728-1731
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust. 相似文献
62.
63.
Chiocchetti R Bombardi C Grandis A Mazzuoli G Gentile A Pisoni L Joechler M Lucchi ML 《American journal of veterinary research》2006,67(10):1662-1669
OBJECTIVE: To analyze the morphology, cytoarchitecture, and lumbosacral spinal cord projections of the red nucleus (RN) in cattle. ANIMALS: 8 healthy Friesian male calves. PROCEDURES: Anesthetized calves underwent a dorsal laminectomy at L5. Eight bilateral injections (lateral to the midline) of the neuronal retrograde fluorescent tracer fast blue (FB) were administered into the exposed lumbosacral portion of the spinal cord. A postsurgical calf survival time of 38 to 55 days was used. Following euthanasia, the midbrain and the L5-S2 spinal cord segments were removed. Nissl's method of staining was applied on paraffin-embedded and frozen sections of the midbrain. RESULTS: The mean length of the RN from the caudal to cranial end ranged from 6,680 to 8,640 microm. The magnocellular and parvicellular components of the RN were intermixed throughout the nucleus, but the former predominate at the caudal portion of the nucleus and the latter at the cranial portion with a gradual transitional zone. The FB-labeled neurons were found along the entire craniocaudal extension of the nucleus, mainly in its ventrolateral part. The number of FB-labeled neurons was determined in 4 calves, ranging from 191 to 1,469 (mean, 465). The mean cross-sectional area of the FB-labeled neurons was approximately 1,680 microm2. CONCLUSIONS AND CLINICAL RELEVANCE: In cattle, small, medium, and large RN neurons, located along the entire craniocaudal extension of the RN, contribute to the rubrospinal tract reaching the L6-S1 spinal cord segments. Thus, in cattle, as has been shown in cats, the RN parvicellular population also projects to the spinal cord. 相似文献
64.
65.
Zannoni A Giunti M Bernardini C Gentilini F Zaniboni A Bacci ML Forni M 《Research in veterinary science》2012,93(2):921-927
Procalcitonin (PCT), recognised as a marker of sepsis, was investigated in a porcine model of endotoxic shock. The results showed that continuous IV infusion (1-4 h) of LPS (40 μg/kg) in pigs was able to induce a generalised increase of PCT expression in lung, heart, kidney and liver. The increase in PCT was significant only in kidney and was accompanied by an increase in IL-6 gene expression. In vitro results demonstrated that peripheral blood mononuclear cells (PBMCs), as well as endothelial cells, were potentially capable of contributing to in vivo extrathyroidal PCT production. These findings support previous data from pigs concerning the occurrence of widespread activation of PCT extrathyroidal gene expression during endotoxic shock in pigs. Nevertheless, the levels of PCT detected were very low, suggesting the need for additional studies to validate the pig as a reliable animal model for investigating the role of PCT in sepsis. 相似文献
66.
Background
Piglets are born with eight sharp teeth that during nursing can cause facial lesions on littermates and teat lesions on the sow. Teeth grinding in piglets is therefore often practiced to reduce these lesions. The aim of this study was to assess the consequences of grinding piglet teeth in regard to the occurrence of lesions.In this study the piglets'' teeth were grinded in 28 litters, and in 36 litters the piglets'' teeth were kept intact. Twice, one time during the first week and one time during the second week after birth facial lesions of the piglets were scored and the teats of the sows were examined for lesions. The facial lesion score accounted for the amount and severity of lesions. The individual observations on piglets in the litter were synthesized in a litter facial lesion score.Findings
69.8% and 43.5% of the piglets had facial lesions in week 1 and week 2 respectively. The effect of treatment was not significant on litter facial lesion score. The litter facial lesion score was higher in week 1 than in week 2 (p < 0.001) and higher in large litters (p = 0.003) than in small litters. Mortality between week 1 and week 2 was higher in litters with intact teeth (p = 0.02). Sow teat lesions only occurred if litters had intact teeth.Conclusions
According to our results teeth grinding is only justifiable in large litters. 相似文献67.
68.
Damian Gianina Elena Micle Valer Sur Ioana Monica 《Journal of Soils and Sediments》2019,19(7):2869-2881
Journal of Soils and Sediments - The aim of the research was to determine the potential of dissolved humic substances extracted from leonardite to mobilize Cu and Pb from multi-metal contaminated... 相似文献
69.
A protein-binding technique was employed to visualize, using scanning electron microscopy, the soy protein as well as the association between HMP and soy protein fractions. Image analysis indicated that at pH 7.5 and 3.5 soy protein isolate showed a bimodal distribution of sizes with an average [ d(0.5)] of about 0.05 microm, but at pH 3.8 the proteins formed larger aggregates than at high pH. Addition of HMP at pH 3.8 changed the surface charge of the particles from +20 to -15 mV. A small addition of HMP caused bridging of the pectin between soy protein aggregates and destabilization. With sufficient HMP, the suspensions showed improved stability to precipitation. The microscopy images are the first direct evidence of the interactions between soy proteins with high-methoxyl pectin (HMP). 相似文献
70.
Venner M Markus RG Strutzberg-Minder K Nogai K Beyerbach M Klug E 《Berliner und Münchener tier?rztliche Wochenschrift》2008,121(1-2):66-72
In 360 samples of colostrum and 36 samples of blood of warmblood mares, the concentration of immunoglobulin G (IgG) was evaluated in the post partal period with an ELISA and the results were compared to values obtained with 2 field methods--refractometry and colostrometry. A significant correlation (p < 0.0001) was determined between ELISA and colostrometry (r = +0.88) and between ELISA and refractometry (r = +0.93). So both field-methods seem suitable for evaluation of the colostral IgG-concentration in mares. Further the kinetic of the IgG concentration in colostrum, the volume of colostrum and the total amount of IgG was measured in the 12 hours post partum (p.p.) in each half udder of 36 mares of different parity. Immediately p.p. primiparous mares have a greater mean concentration of IgG (68 mg/ml) than multiparous mares (51 mg/ml). However, multiparous mares have a mean colostral volume of 1020 ml whereas, in primiparous mares, a mean volume of 527 ml was determined within the first three hours p.p. As a result of this the total amount of IgG was lower in primiparous (31.5 g) than in multiparous mares (48.5 g). A significant decrease of IgG concentration was measured in multiparous mares in the 1.5 hours following partum versus 3 hours in primiparous mares. The mean IgG concentration in the blood serum of the 36 mares immediately p.p. was 13.4 +/- 3.6 mg/ml. No significant correlation was observed between values of IgG concentration in the blood and in the colostrum of the mares. 相似文献