全文获取类型
收费全文 | 159356篇 |
免费 | 8385篇 |
国内免费 | 79篇 |
专业分类
林业 | 6821篇 |
农学 | 4899篇 |
基础科学 | 1099篇 |
18385篇 | |
综合类 | 29697篇 |
农作物 | 6308篇 |
水产渔业 | 7266篇 |
畜牧兽医 | 81562篇 |
园艺 | 1886篇 |
植物保护 | 9897篇 |
出版年
2018年 | 1922篇 |
2017年 | 2130篇 |
2016年 | 2035篇 |
2015年 | 1723篇 |
2014年 | 2074篇 |
2013年 | 5989篇 |
2012年 | 4001篇 |
2011年 | 4832篇 |
2010年 | 3244篇 |
2009年 | 3214篇 |
2008年 | 4915篇 |
2007年 | 4570篇 |
2006年 | 4321篇 |
2005年 | 4098篇 |
2004年 | 4096篇 |
2003年 | 4164篇 |
2002年 | 3908篇 |
2001年 | 4799篇 |
2000年 | 4749篇 |
1999年 | 3648篇 |
1998年 | 1567篇 |
1997年 | 1647篇 |
1995年 | 1874篇 |
1994年 | 1688篇 |
1993年 | 1639篇 |
1992年 | 3362篇 |
1991年 | 3622篇 |
1990年 | 3556篇 |
1989年 | 3609篇 |
1988年 | 3333篇 |
1987年 | 3318篇 |
1986年 | 3534篇 |
1985年 | 3387篇 |
1984年 | 2789篇 |
1983年 | 2513篇 |
1982年 | 1709篇 |
1981年 | 1565篇 |
1979年 | 2578篇 |
1978年 | 2077篇 |
1977年 | 1763篇 |
1976年 | 1717篇 |
1975年 | 1786篇 |
1974年 | 2255篇 |
1973年 | 2366篇 |
1972年 | 2312篇 |
1971年 | 2204篇 |
1970年 | 2076篇 |
1969年 | 1969篇 |
1968年 | 1612篇 |
1967年 | 1736篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
71.
H Ano S Makimura R Harasawa 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(5):561-562
Nucleotide sequences of ribosomal DNA (rDNA) of Babesia (B.) gibsoni occurring in Miyazaki, western Japan, were examined using blood samples obtained from seven dogs suffering from natural canine babesiosis. DNA isolated from these blood samples was subjected to the polymerase chain reaction (PCR). The nucleotide sequences of the PCR products were determined and compared with other rDNA sequences of B. gibsoni isolated from Asia, Europe and U.S.A. Although homology values between our isolates and those isolated from Europe and U.S.A. were both 84.0%, respectively, our isolates were identical to the Asian types. In conclusion, B. gibsoni occurring in Miyazaki was revealed to have the genotype Asia 1 or Asia 2 from a comparison of the partial rDNA sequences. 相似文献
72.
The dietary lysine requirement of juvenile red drum Sciaenops ocellatus was reevaluated in two separate experiments. In the first experiment, lyophilized red drum muscle was combined with an L-form crystalline amino acid premix to yield diets containing approximately 35% protein on a dry-matter basis. Gradations (0.25%) of L-lysine HCl were added to the basal diet containing approximately 1.0% lysine. Each diet was fed to triplicate groups of juvenile red drum initially weighing 6–7 g for 8 weeks. Based on growth and feed efficiency data, the lysine requirement (±SE) was determined to be 1.55% (±0.079%) of dry diet or 4.430% of dietary protein. In a second experiment, the lysine requirement of red drum was investigated with diets containing 35% intact protein from zein and red drum muscle. Each of the zein-based diets containing incremental levels of lysine was fed to triplicate groups of juvenile red drum initially weighing 1–2 g for 8 weeks. A crystalline amino acid test diet serving as a control in this experiment significantly outperformed the zein-based diets, and palatability of those diets was questionable due to an obvious change in feeding behavior of the fish. Due to the inferior performance of the fish fed the zein-based diets, the authors were not successful in determining a requirement with these diets. Thus, a lysine requirement of 1.55% of dry diet (4.43% of dietary protein) as determined in the first experiment is recommended for juvenile red drum. 相似文献
73.
G Schorr 《Tier?rztliche Praxis》1988,16(2):163-165
Serum iron concentration and iron-binding capacity were determined in 34 respectively 35 clinically healthy horses of different sex, with the age of 3 to 21 years. In the Warm blooded horse, the Half bred, the Haflinger horse, the Heavy horse and the Arabian Haflinger the mean serum iron concentration amounted to 253 +/- 66 micrograms/dl, 202 +/- 87 micrograms/dl, 166 +/- 67 micrograms/dl, 183 micrograms/dl and 366 micrograms/dl, while the iron-binding capacity in the Warm blooded horse, the Half bred, the Haflinger horse, the Thoroughbred, the Heavy horse and the Arabian Haflinger ran up to 427 +/- 55 micrograms/dl, 530 +/- 162 micrograms/dl, 422 +/- 63 micrograms/dl, 447 micrograms/dl, 467 micrograms/dl and 394 micrograms/dl. Regarding serum iron concentration no age or sex differences were ascertained, whereas they were obvious when observing the iron-binding capacity. Diurnal variations in serum iron concentration are pointed out. The quotient of the two examined parameters showed race-related differences. The results are presented in tables. 相似文献
74.
75.
Meat regulations also involve game inspection. This publication deals with the regulations concerning furred game intended for slaughter and furred game hunted for food. 相似文献
76.
G. J. Glova 《Ecology of Freshwater Fish》2003,12(4):247-253
Abstract – The interaction between brown trout ( Salmo trutta ; fork length (FL) range 255–390 mm) and inanga ( Galaxias maculatus ; FL range 55–115 mm) was tested during summer through autumn in an artificial stream consisting of a single run-riffle-pool sequence with a natural food supply. Each experimental trial lasted for 15 days, and consisted of two brown trout and 50 inanga collected fresh from a nearby stream, with each species given prior residence in four replicate tests, totalling eight trials in all. In addition, two control trials (each 10 days), with 50 inanga in each, were run. Brown trout almost exclusively occupied the pool, whereas inanga occupied all habitat types, although in different proportions, when tested with and without brown trout. The proportion of inanga in the pool was appreciably lower in the experimental trials with brown trout than in the control trials with no brown trout; prior residence had no significant effect on inanga habitat use. Mortality of inanga attributable to predation by brown trout ranged from 0 to 40% with a mean of 14.5 ± 4.7%. The results suggest that habitat use and survival of inanga populations in small streams can be adversely affected by brown trout. 相似文献
77.
Abstract. Experiments were conducted for one year on two different soil types. On a clay soil straw was either (a) burnt, (b) baled leaving the stubble, or (c) chopped and spread. The soil was tine cultivated to depths of 5, 10 or 15 cm or ploughed to 20 or 30 cm before winter wheat was sown conventionally. In addition, a direct-drilled crop was sown after each straw treatment. On a silt loam soil the direct-drilled, tine cultivated to 15 cm and ploughed to 30 cm treatments following burning or chopping and spreading straw were repeated.
Tine cultivation incorporated less straw than ploughing, decreased plant establishment and early growth but did not decrease yield. Direct-drilling through chopped straw decreased yield on the silt loam but not on the clay soil. Short straw (< 5 cm) was easier to incorporate than longer straw. Ploughing was the most efficient method of straw incorporation because it inverts soil. Early effects on crop growth and nutrient uptake following straw incorporation were transient and associated with large amounts of straw in the seeded layer of soil. 相似文献
Tine cultivation incorporated less straw than ploughing, decreased plant establishment and early growth but did not decrease yield. Direct-drilling through chopped straw decreased yield on the silt loam but not on the clay soil. Short straw (< 5 cm) was easier to incorporate than longer straw. Ploughing was the most efficient method of straw incorporation because it inverts soil. Early effects on crop growth and nutrient uptake following straw incorporation were transient and associated with large amounts of straw in the seeded layer of soil. 相似文献
78.
R D Park 《Veterinary Clinics of North America: Equine Practice》1989,5(1):47-66
A complete radiographic examination of the equine foot consists of properly exposed, processed, and positioned radiographs. For radiographic interpretation, in addition to knowing radiographic signs of disease, a knowledge of normal radiographic anatomy and possible insignificant anatomic variations is necessary. 相似文献
79.
Efficacy of ivermectin treatment (0.2 mg/kg) against 28-day experimental infections of Parascaris equorum was determined in 18 pony foals6–17.5 weeks old. There were 6 foals in each group: nontreated control, ivermectin injectable or oral paste. In comparison with larvae found in the nontreated controls, ivermectin injectable or paste was 96.0% and 99.9% efficacious. There was a distinct difference in drug effect against the larger (ca 26mm.) vs the smaller (13–19mm) larvae by the 2 formulations of ivermectin. There were no adverse signs related to treatment of the young foals. 相似文献
80.
T R Thedford L W Johnson 《Veterinary Clinics of North America: Food Animal Practice》1989,5(1):145-157
Although there are notable infectious conditions that are capable of producing clinical disease in the NWC, overall, these species are quite healthy. Of the bacterial diseases, enterotoxemia caused by Clostridium perfringens types C and D would be deemed the most significant in North America, while type A also would be regarded as important in South America. Other important bacterial infections of potential concern are tuberculosis, Johne's disease, anthrax, malignant edema, actinomycosis, tetanus, and the South American condition referred to as alpaca fever, which, to date, has not been observed in North America. Fungal infections include classical ringworm, principally caused by Trichophyton spp., and the cases of coccidioidomycosis that are associated with the arid desert lands of the southwestern United States. Most notable of naturally occurring viral infections in the NWC would be rabies, ecthyma, and a recently described blindness neuropathy that has been associated with the equine herpesvirus I. NWC can be infected experimentally with agents causing hoof-and-mouth disease and vesicular stomatitis, but naturally occurring cases do not seem to occur. Serological evidence of exposure to many viral agents, including blue tongue, parainfluenza 3, bovine respiratory syncytial virus, bovine herpesvirus I, bovine viral diarrhea, influenza A, and rotavirus, has been demonstrated; however, no clinical disease associated with these agents, as yet, is apparent. 相似文献