全文获取类型
收费全文 | 24865篇 |
免费 | 1285篇 |
国内免费 | 10篇 |
专业分类
林业 | 876篇 |
农学 | 753篇 |
基础科学 | 154篇 |
3613篇 | |
综合类 | 3528篇 |
农作物 | 909篇 |
水产渔业 | 1338篇 |
畜牧兽医 | 13165篇 |
园艺 | 268篇 |
植物保护 | 1556篇 |
出版年
2019年 | 249篇 |
2018年 | 415篇 |
2017年 | 507篇 |
2016年 | 470篇 |
2015年 | 337篇 |
2014年 | 457篇 |
2013年 | 959篇 |
2012年 | 794篇 |
2011年 | 949篇 |
2010年 | 686篇 |
2009年 | 669篇 |
2008年 | 966篇 |
2007年 | 916篇 |
2006年 | 808篇 |
2005年 | 735篇 |
2004年 | 643篇 |
2003年 | 705篇 |
2002年 | 605篇 |
2001年 | 803篇 |
2000年 | 799篇 |
1999年 | 633篇 |
1998年 | 275篇 |
1997年 | 282篇 |
1995年 | 259篇 |
1994年 | 227篇 |
1993年 | 232篇 |
1992年 | 424篇 |
1991年 | 516篇 |
1990年 | 434篇 |
1989年 | 411篇 |
1988年 | 400篇 |
1987年 | 409篇 |
1986年 | 363篇 |
1985年 | 388篇 |
1984年 | 339篇 |
1983年 | 287篇 |
1982年 | 243篇 |
1979年 | 383篇 |
1978年 | 289篇 |
1977年 | 290篇 |
1976年 | 299篇 |
1975年 | 317篇 |
1974年 | 332篇 |
1973年 | 302篇 |
1972年 | 290篇 |
1971年 | 245篇 |
1969年 | 289篇 |
1968年 | 269篇 |
1967年 | 326篇 |
1966年 | 304篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Changes in soil nutrient content and bacterial community after 12 years of organic amendment application to a vineyard 下载免费PDF全文
M. E. Calleja‐Cervantes A. J. Fernández‐González I. Irigoyen J. F. Cibriáin‐Sabalza N. Toro P. M. Aparicio‐Tejo M. Fernández‐López 《European Journal of Soil Science》2015,66(4):802-812
An interesting alternative to landfills for disposing of organic residues is their addition to soil as composted organic residues. There is little information available about the long‐term benefits following prolonged periods of application. After 12 years of annual incorporation of organic amendments to the soil of a vineyard, three soil characteristics were analysed: mineral content, bacterial community and soil greenhouse gas (GHG) emissions. The organic amendments were (i) a pelletized organic compost (PEL) made from plant, animal and sewage sludge residues, (ii) a compost made from the organic fraction of municipal solid waste (OF‐MSW) and (iii) a stabilized sheep manure compost (SMC). Mineral fertilizer (NPK) and an unaltered control treatment were also included. Our results showed that long‐term application of treated residues as compost changed soil nutrient content, bacterial community and gas emission rates. For instance, SMC increased nutrients and soil organic matter (OM) throughout the experiment. There was a change in bacterial community structure, with an increase in the phylum Proteobacteria observed for all four treated soils, and an increase in the phylum Bacteroidetes for PEL, OF‐MSW and SMC treatments. Among the organically‐amended soils, the amount of Adhaeribacter increased by a factor of 2.5 times more than the control, which reported a total of 2.0% of the bacterial community compared with 5.6% for PEL, 5.2% for OF‐MSW and 5.0% for SMC. Adhaeribacter may be a genus that specializes in the degradation of residues in the different composts. The SMC treatment had the largest Chao1 estimator and was the most biodiverse of all treatments. These changes in bacterial community structure did not correlate with the observed GHG fluxes from the sampling day. The application of amendments did not affect N2O fluxes. However, the application of treatments slightly reduced the capacity for CH4 sequestration by soil with respect to the untreated soils. Compost is an effective method to increase soil fertility. Soil GHG emissions should be further evaluated. 相似文献
992.
Growth trials were conducted outdoors in the UK to determine the yield, yield components and plant architectural differences
between determinate and indeterminate Phaseolus vulgaris bean plants. F3 lines derived from crosses between ‘Prelude’, a determinate cultivar and ‘V8’, an indeterminate landrace,
were grown together with the parents and ‘Carioca’, an indeterminate landrace from Brazil. Data were recorded on flowering
date, number of nodes on main stem at flowering, plant height at maturity, number of pods/plant, number of seeds/pod, number
of seeds/plant, 100-seed weight, seed mass/plant, percentages of diseased and healthy seeds/plant. Determinate F3 lines had
significantly lower (P < 0.05) seed mass/plant, fewer pods/plant, fewer seeds/pod, fewer seeds/plant, lower harvest index, shorter stems, earlier
date of flowering, fewer nodes at flowering and fewer healthy seeds/plant than indeterminate F3 lines. However, determinate
genotypes had significantly larger (P < 0.05) pods to accommodate their larger seeds compared with indeterminate lines. A similar situation was found when the
yield and yield components of ‘V8’, ‘Prelude’ and ‘Carioca’ were evaluated; the highest seed mass/plant was given by ‘V8’
and the lowest by ‘Prelude’. Furthermore, some indeterminate genotypes with Type IV growth habit yielded significantly higher
(P < 0.05) than the high-yielding parent, ‘V8’, indicating a positive influence on seed yield by crossing different genotypes. 相似文献
993.
J. W. Hanna N. B. Klopfenstein M.‐S. Kim G. I. McDonald J. A. Moore 《Forest Pathology》2007,37(3):192-216
Nuclear ribosomal DNA regions (i.e. large subunit, internal transcribed spacer, 5.8S and intergenic spacer) were sequenced using a direct‐polymerase chain reaction method from Armillaria ostoyae genets collected from the western USA. Many of the A. ostoyae genets contained heterogeneity among rDNA repeats, indicating intragenomic variation and likely intraspecific hybridization. Intragenomic variation was verified by visually editing base‐sequence offsets in regions with insertions/deletions, and using sequence‐specific internal primers to resequence heterogeneous regions. Phylogenetic analyses with Bayesian Inference methods were used to define groups within A. ostoyae. Analysis of A. ostoyae from outside the western USA indicated the presence of a Circumboreal group of A. ostoyae that also occurs in Utah; two other phylogeographic groups were associated with the Rocky Mountain and Pacific Northwest regions of the USA. Mixed sequence types, an indication of intraspecific hybrids, were common in some geographic regions. Hybridization events may have influenced species evolution, contributing to variation in pathogenicity and virulence. The occurrence of these groups and intraspecific hybrids also indicates that paleogeography and paleoclimate may have influenced the phylogeography of A. ostoyae. In addition, other Armillaria species were examined for evolutionary relationships with the groups of A. ostoyae. These findings will provide a basis for future research relating ecological function to genetic diversity within A. ostoyae. 相似文献
994.
Farooqi IS Bullmore E Keogh J Gillard J O'Rahilly S Fletcher PC 《Science (New York, N.Y.)》2007,317(5843):1355
Studies of the fat-derived hormone leptin have provided key insights into the molecular and neural components of feeding behavior and body weight regulation. An important challenge lies in understanding how the rewarding properties of food interact with, and can override, physiological satiety signals and promote overeating. We used functional magnetic resonance imaging to measure brain responses in two human patients with congenital leptin deficiency who were shown images of food before and after 7 days of leptin replacement therapy. Leptin was found to modulate neural activation in key striatal regions, suggesting that the hormone acts on neural circuits governing food intake to diminish the perception of food reward while enhancing the response to satiety signals generated during food consumption. 相似文献
995.
Combined effects of temperature and light quality on plants have received little attention. We investigated the single and interactive effects of temperature and light quality on growth and physiological characteristics of four canola (Brassica napus) cultivars – Clearfield 46A76 (cv1), Clearfield 45H72 (cv2), Roundup Ready 45H24 (cv3) and Roundup Ready 45H21 (cv4). Plants were grown under lower (24°/20 °C) and higher (30°/26 °C) temperature regimes at low red/far‐red (R/FR), normal R/FR and high R/FR light ratios in environment‐controlled growth chambers (16 h light/8 h dark). Higher temperature reduced stem height and diameter; leaf number and area; dry matter of all plant parts; and specific leaf weight, but increased leaf area ratio; and chlorophyll (Chl) fluorescence (Y). Low R/FR increased stem height; Y; and ethylene, but decreased stem diameter; Fv/Fm; Chl a; Chl b; and carotenoids. Among cultivars, plants from cv4 were tallest with thickest stems and greatest dry matter. None of the main factors affected gas exchange. Higher temperature at high R/FR caused cv3 to be shortest, whereas lower temperature at low R/FR caused cv4 to be tallest. We conclude that heat and other stress factors will adversely affect sensitive crops, but tolerant genotypes should perform well under future climate. 相似文献
996.
Sorghum [(Sorghum bicolor L.) Moench] is a highly productive crop plant, which can be used for alternative energy resource, human food, livestock feed or industrial purposes. The biomass of sorghum can be utilized as solid fuel via thermochemical routes or as a carbohydrate substrate via fermentation processes. The plant has a great adaptation potential to drought, high salinity and high temperature, which are important characteristics of genotypes growing in extreme environments. However, the climate change in the 21st century may bring about new challenges in the cultivated areas. In this review, we summarize the most recent literature about the responses of sorghum to the most important abiotic stresses: nutrient deficiency, aluminium stress, drought, high salinity, waterlogging or temperature stress the plants have to cope with during cultivation. The advanced molecular and system biological tools provide new opportunities for breeders to select stress‐tolerant and high‐yielding cultivars. 相似文献
997.
998.
Van Overbeke I Chiers K Ducatelle R Haesebrouck F 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2001,48(1):15-20
The efficacy of a subunit vaccine containing the Apx toxins of Actinobacillus pleuropneumoniae and transferrin-binding proteins was determined. Ten pigs were vaccinated twice with the vaccine. Eight control animals were injected twice with a saline solution. Three weeks after the second vaccination, all pigs were endobronchially inoculated with 10(6.5) colony-forming units (CFU) of an A. pleuropneumoniae serotype 9 strain. In the vaccine group, none of the pigs died after inoculation. Only one pig of the control group survived challenge. Surviving pigs were killed at 7 days after challenge. The mean percentage of affected lung tissue was 64% in the control group and 17% in the vaccine group. Actinobacillus pleuropneumoniae was isolated from the lungs of all animals. The mean bacterial titres of the caudal lung lobes were 5.0 x 10(8) CFU/g in the control group and 3.0 x 10(6) CFU/g in the vaccine group. It was concluded that the vaccine induced partial protection against severe challenge. 相似文献
999.
Bras ID Colitz CM Saville WJ Gemensky-Metzler AJ Wilkie DA 《Veterinary ophthalmology》2006,9(5):317-327
Posterior capsular opacification (PCO) is the most common postoperative complication of contemporary cataract surgery. Limited information is available regarding PCO formation and factors that influence PCO development in the dog. Two hundred sixty-five eyes (144 from diabetic dogs and 121 from dogs with breed-related cataracts) were prospectively evaluated for PCO formation for up to 12 months postoperatively. The mean age of all dogs in the study was 7.77 years and diabetic dogs were significantly older than dogs with breed-related cataracts. There were 73 males (61 neutered, 12 intact) and 74 females (70 neutered, 4 intact) in the study. Statistical analysis was performed based on age, breed/size, gender, stage of cataract at the time of surgery, PCO score at each time point, breed-related vs. diabetic cataract, right eyes compared to left eyes, and presence/absence of uveitis. Age and gender did not significantly influence PCO formation. Small and medium-sized breeds developed significantly more PCO in comparison to the large/giant breeds at 2 weeks and 2-4 months postoperatively, but the differences were not significant at later time points. There was an overall significant increase in PCO formation in eyes with early immature cataracts when compared to other stages of cataract up to 4 months postoperatively but not at later time points. There were no statistical differences in PCO score at 6 months or at 1 year postoperatively in eyes with breed-related and diabetic cataracts. Right eyes did not differ from left eyes in PCO score. PCO score significantly increased over time in breed-related and diabetic groups and in the overall population. No difference was found in the degree of PCO formation in eyes with inflammation prior to or after surgery compared with those without inflammation. In summary, age, gender, presence of inflammation, and cause of cataract (breed-related vs. diabetes mellitus) do not influence the development of PCO in canine cataract dogs. Small and medium-sized breeds develop significant PCO earlier than larger breeds. It is important to note that all eyes from all dogs in this study developed PCO in a time dependent manner. 相似文献
1000.