全文获取类型
收费全文 | 455篇 |
免费 | 23篇 |
专业分类
林业 | 37篇 |
农学 | 18篇 |
基础科学 | 2篇 |
98篇 | |
综合类 | 49篇 |
农作物 | 29篇 |
水产渔业 | 32篇 |
畜牧兽医 | 146篇 |
园艺 | 13篇 |
植物保护 | 54篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 21篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 22篇 |
2011年 | 44篇 |
2010年 | 21篇 |
2009年 | 22篇 |
2008年 | 29篇 |
2007年 | 38篇 |
2006年 | 23篇 |
2005年 | 17篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1951年 | 1篇 |
1942年 | 1篇 |
1941年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有478条查询结果,搜索用时 296 毫秒
91.
Farrah R. Fatemi Ivan J. Fernandez Johanna Szillery Stephen A. Norton Lindsey E. Rustad 《Water, air, and soil pollution》2012,223(9):6171-6186
We examined long-term changes in soil solution chemistry associated with experimental, whole watershed-acidification at the Bear Brook Watershed in Maine (BBWM). At BBWM, the West Bear (WB) watershed has been treated with bimonthly additions of ((NH4)2 SO4) since 1989. The adjacent East Bear (EB) watershed serves as a biogeochemical reference. Soil solution chemistry in the EB watershed was relatively stable from 1989?C2007, with the exception of declining SO4?CS concentrations associated with a progressive decline in SO4?CS deposition during this period. Soil solution chemistry in WB reflected a progressive change in acid-neutralization mechanisms from base cation buffering to Al buffering associated with treatment during this period. Total dissolved Al concentrations progressively increased over time and were ~4× higher in 2007 than in 1989. Treatment of WB was also associated with long-term increases in soil solution H+, SO4?CS, and NO3?CN, whereas soil solution dissolved organic carbon (DOC) was unresponsive to treatment. For solutes such as Ca, H+, and SO4?CS, changes in stream chemistry were generally parallel to changes in soil solution chemistry, indicating a close coupling of terrestrial and aquatic processes that regulate the chemistry of solutions in this first-order stream watershed. For other solutes such as Al and DOC, solute concentrations were higher in soil solutions compared with streams, suggesting that sorption and transformation processes along hydrologic flow-paths were important in regulating the chemistry of solutions and the transport of these solutes. 相似文献
92.
Daniel P. Fogarty Benjamin Reinhart Tochko Tzvetkov Ivan Nesch Cooper Williams 《Journal of Equine Veterinary Science》2011,31(7):365-369
We describe and demonstrate the first application of a laboratory-based diffraction-enhanced X-ray imaging instrument for noninvasive equine imaging. A formalin-preserved disarticulated forelimb from a near-term aborted miniature horse fetus was imaged with diffraction-enhanced X-ray imaging. The resultant calculated images—absorption, extinction, refraction, and scattering—are presented, and soft-tissues such as the dorsal digital extensor tendon, articular cartilage, as well as various joint, tendon sheath, and bursa recesses are observed in simultaneous registration with the adjacent dense bone tissue. Radiation dose calculations were performed and a calculated surface dose of 0.6 mGy for the soft muscular tissue was determined for the imaging experiment. 相似文献
93.
Stefanov I Baeten V Abbas O Colman E Vlaeminck B De Baets B Fievez V 《Journal of agricultural and food chemistry》2011,59(24):12771-12783
The feasibility of Raman spectroscopy in combination with partial least-squares (PLS) regression for the determination of individual or grouped trans-monounsaturated fatty acids (trans-MUFA) and conjugated linoleic acids (CLA) in milk fat is demonstrated using spectra obtained at two temperature conditions: room temperature and after freezing at -80 °C. The PLS results displayed capability for direct semiroutine quantification of several individual CLA (cis-9,trans-11 and trans-10,cis-12 C18:2) and trans-MUFA (trans-4-15 C18:1) in minor concentrations (below 1.0 g/100 g of milk fat). Calibration models were based on reference data cross-correlation or determined by specific scattering signals in the Raman spectra. Distinct bands for trans-MUFA (1674 cm(-1)) and CLA (1653 cm(-1)) from the trans isolated and cis,trans conjugated C ═ C bonds were identified, as well as original evidence for the temperature effect (new bands, peak shifts, and higher intensities) on the Raman spectra of fatty acid methyl ester and triacylglyceride standards, are supplied. 相似文献
94.
Genetic and immunobiological diversities of porcine reproductive and respiratory syndrome genotype I strains 总被引:1,自引:0,他引:1
Darwich L Gimeno M Sibila M Diaz I de la Torre E Dotti S Kuzemtseva L Martin M Pujols J Mateu E 《Veterinary microbiology》2011,150(1-2):49-62
Genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) has been based on ORF5/GP5 and ORF7/N protein variations. Complete viral genome studies are limited and focused on a single or a few set of strains. Moreover, there is a general tendency to extrapolate results obtained from a single isolate to the overall PRRSV population. In the present study, six genotype-I isolates of PRRSV were sequenced from ORF1a to ORF7. Phylogenetic comparisons and the variability degree of known linear B-epitopes were done considering other available full-length genotype-I sequences. Cytokine induction of all strains was also evaluated in different cellular systems. Non structural protein 2 (nsp2) was the most variable part of the virus with 2 out of 6 strains harboring a 74 aa deletion. Deletions were also found in ORF3 and ORF4. Phylogenetic analyses showed that isolates could be grouped differently depending on the ORF examined and the highest similarity with the full genome cluster was found for the nsp9. Interestingly, most of predicted linear B-epitopes in the literature, particularly in nsp2 and GP4 regions, were found deleted or varied in some of our isolates. Moreover, 4 strains, those with deletions in nsp2, induced TNF-α and 3 induced IL-10. These results underline the high genetic diversity of PRRSV mainly in nsp1, nsp2 and ORFs 3 and 4. This variability also affects most of the known linear B-epitopes of the virus. Accordingly, different PRRSV strains might have substantially different immunobiological properties. These data can contribute to the understanding of PRRSV complexity. 相似文献
95.
Scott A. Parsons Ivan R. Lawler Robert A. Congdon Stephen E. Williams 《植物养料与土壤学杂志》2011,174(5):710-720
Plant‐litter chemical quality is an important driver of many ecosystem processes, however, what actually constitutes high‐ or low‐quality litter (chemical potential for fast and slow decomposition, respectively) is often interpreted by the indices available. Here, near‐infrared spectroscopy (NIRS) was used to explore leaf‐litter chemical quality and the controls on decomposition in the tropical rainforest region of north Queensland Australia. Leaf‐litter samples from litterfall collections and litterbag studies were used. NIRS was used to calibrate the chemical compositions of the material (N, P, C, Mg, Ca, acid detergent fiber, acid detergent lignin, α‐cellulose, and total phenolics) from a smaller sample set covering the spectral range in the full set of samples. Calibrations were compared for both separate (local) and combined models, for litterbags, and litterfall. Coefficients of determination (r2) in the local models ranged from 0.88 (litterbag Mg) to 0.99 (litterfall N), with residual prediction deviation ratios > 3 for all constituents except Mg (≈ 2.5). Mass loss in the litterbags was strongly related to the NIR spectra, with model r2's of 0.75 (in situ leaves) and 0.76 (common control leaf). In situ decomposability was determined from modeling the initial NIR spectra prior to decomposition with litterbag exponential‐decay rates (model r2 of 0.81, n = 85 initial samples). A best subset model including litter‐quality, climate, and soil variables predicted decay better than the NIR decomposability model (r2 = 0.87). For litter quality alone the NIR model predicted decay rate better than all of the best predictive litter–chemical quality indices. The decomposability model was used to predict in situ decomposability in the litterfall samples. The chemical variables explaining NIR decomposability for litterfall were initial P, C, and phenolics (linear model r2 = 0.80, n = 2471). NIRS is a holistic technique that is just as, if not more accurate, than litter–chemical quality indices, when predicting decomposition and decomposability, shown here in a regional field study. 相似文献
96.
Sociodemographic, health and lifestyle predictors of poor diets 总被引:1,自引:0,他引:1
Harrington J Fitzgerald AP Layte R Lutomski J Molcho M Perry IJ 《Public health nutrition》2011,14(12):2166-2175
97.
Ivan Carvalho Filho Daniele Botelho Diniz Marques Carolina Filardi de Campos José Domingos Guimarães Simone Eliza Facioni Guimarães Paulo Sávio Lopes Fabyano Fonseca e Silva Renata Veroneze 《Reproduction in domestic animals》2020,55(1):38-43
Nellore is the main cattle breed used in Brazil, being the largest commercial herd in the world. Beyond the importance of male reproductive efficiency for farm profit, the use of reproductive techniques, mainly artificial insemination, turns the evaluation of male reproductive traits even more important. Estimation of genetic parameters increases the knowledge on traits variances and allows envisaging the possibility of the inclusion of new traits as selection criterion. Genetic parameters for fifteen traits that can be classified as testicular biometry or physical and morphological semen traits were estimated for a Nellore bull population ranging from 18 to 36 months. Single-trait and bi-trait animal models were used for (co)variance components estimation. The contemporary group was considered as fixed effect and age at measurement as covariable. Scrotal circumference presented heritability of 0.47 ± 0.12. This value is similar to the heritabilities found for all testicular biometry traits (0.34–0.48). Sperm progressive motility, which has a direct effect on bull fertility, presented low heritability (0.07 ± 0.08). Major and total sperm defects presented moderate to high heritabilities (0.49 ± 0.18 and 0.39 ± 0.15, respectively), indicating that great genetic gain can be obtained through selection against sperm defects. High and positive genetic correlations were observed among testicular biometry traits, which also presented favourable genetic correlations with physical and morphological traits of the semen with magnitude ranging from high to low. Scrotal circumference presented moderate to high and favourable genetic correlations with sperm progressive motility, sperm turbulence, major sperm defects and total sperm defects. Thus, the selection for scrotal circumference results in favourable correlated genetic response for semen quality. The results show that the use of scrotal circumference as reference trait for bull fertility is appropriate, since it presents high heritability and favourable genetic correlation with semen quality. 相似文献
98.
Costa Olmar Antônio Denardin Ferreira Otoniel Geter Lauz Henrique Douglas Sampaio Vaz Ricardo Zambarda Fluck Ana Carolina Paris Wagner Kröning Alexsandro Bahr Griffith Luis Alberto Alonzo Matos Oscar Ivan Tuz 《Tropical animal health and production》2020,52(2):547-554
Tropical Animal Health and Production - The aim was to monitor the growth, the dry mass accumulation curve, and the structural photosynthetic components of forage peanut pasture, in different... 相似文献
99.
Blessing Mabate Chantal Dsire Daub Samkelo Malgas Adrienne Lesley Edkins Brett Ivan Pletschke 《Marine drugs》2021,19(1)
Fucoidans are complex polysaccharides derived from brown seaweeds which consist of considerable proportions of L-fucose and other monosaccharides, and sulphated ester residues. The search for novel and natural bioproduct drugs (due to toxicity issues associated with chemotherapeutics) has led to the extensive study of fucoidan due to reports of it having several bioactive characteristics. Among other fucoidan bioactivities, antidiabetic and anticancer properties have received the most research attention in the past decade. However, the elucidation of the fucoidan structure and its biological activity is still vague. In addition, research has suggested that there is a link between diabetes and cancer; however, limited data exist where dual chemotherapeutic efforts are elucidated. This review provides an overview of glucose metabolism, which is the central process involved in the progression of both diseases. We also highlight potential therapeutic targets and show the relevance of fucoidan and its derivatives as a candidate for both cancer and diabetes therapy. 相似文献
100.
Ivan ARROYO-HERRERA Brenda ROMN-PONCE Rafael BUSTAMANTE-BRITO Joseph GUEVARA-LUNA Erika Yanet TAPIA-GARCA Violeta LARIOS-SERRATO Nannan ZHANG Paulina ESTRADA-DE LOS SANTOS En Tao WANG Mara Soledad VSQUEZ-MURRIETA 《土壤圈》2023,33(4):600-611
High arsenic (As) and chromium (Cr) concentrations are currently receiving attention because of their negative effects on the environment and human health. Microorganisms inhabiting contaminated environments have developed resistance mechanisms against the toxicity of these pollutants. Indeed, members of the bacterial genus Micrococcus have been isolated from different toxic metal-contaminated environments; however, knowledge concerning its resistance mechanisms to As and Cr toxicity remains lim... 相似文献