全文获取类型
收费全文 | 2015篇 |
免费 | 168篇 |
国内免费 | 3篇 |
专业分类
林业 | 73篇 |
农学 | 22篇 |
基础科学 | 35篇 |
273篇 | |
综合类 | 362篇 |
农作物 | 81篇 |
水产渔业 | 159篇 |
畜牧兽医 | 1077篇 |
园艺 | 37篇 |
植物保护 | 67篇 |
出版年
2022年 | 21篇 |
2021年 | 39篇 |
2020年 | 41篇 |
2019年 | 49篇 |
2018年 | 39篇 |
2017年 | 38篇 |
2016年 | 28篇 |
2015年 | 41篇 |
2014年 | 48篇 |
2013年 | 94篇 |
2012年 | 91篇 |
2011年 | 131篇 |
2010年 | 65篇 |
2009年 | 53篇 |
2008年 | 87篇 |
2007年 | 88篇 |
2006年 | 67篇 |
2005年 | 86篇 |
2004年 | 55篇 |
2003年 | 73篇 |
2002年 | 48篇 |
2001年 | 41篇 |
2000年 | 40篇 |
1999年 | 29篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 31篇 |
1991年 | 38篇 |
1990年 | 29篇 |
1989年 | 35篇 |
1988年 | 44篇 |
1987年 | 31篇 |
1986年 | 31篇 |
1985年 | 38篇 |
1984年 | 29篇 |
1983年 | 29篇 |
1982年 | 15篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1976年 | 11篇 |
1975年 | 14篇 |
1974年 | 23篇 |
1973年 | 15篇 |
1972年 | 11篇 |
1971年 | 12篇 |
1970年 | 16篇 |
排序方式: 共有2186条查询结果,搜索用时 15 毫秒
91.
B K Knudson M G Hogberg R A Merkel R E Allen W T Magee 《Journal of animal science》1985,61(4):797-801
Differences in total carcass bone, muscle and fat, and linear measurements of the tibia and radius were evaluated in barrows at 105 kg and boars at 105, 118, 132 and 145 kg live body weight. The carcasses of five replicates were physically separated into skin, bone and soft tissues, and the linear measurements of the tibia and radius were obtained on seven replicates. At live weight of 105 kg, boars did not differ significantly in fat-free muscle, but they had 33.2% less fat, 11% greater bone weight and 14% greater skin weight than barrows. At 145 kg, boars had total carcass fat weight comparable with 105-kg barrows. Fat-free muscle, bone and skin weight of boars increased at linear rates of .41, .083 and .104 kg/kg of body weight increase from 105 to 145 kg, respectively. At 105 kg, density and length of the tibia and radius did not differ between boars and barrows. The tibia of boars were heavier than those of barrows at 105 kg, resulting in a greater ratio of tibia weight to length (indirect measure of bone thickness). As boars increased in live weight from 105 to 145 kg, total weight and length of the tibia and radius increased linearly. The ratio of weight to length of the tibia and radius increased during this 40-kg weight gain, indicating that weight of both bones increased at a greater rate than length. These results indicate that boars and barrows have the same weight of total carcass fat when boars are 40 kg heavier than the barrows. The greater bone weight of boar carcasses compared with barrows is due to greater bone thickness. 相似文献
92.
J N Chambers P T Purinton S W Allen J L Moore 《American journal of veterinary research》1990,51(2):305-313
The vascular patterns to pelvic limb muscles were studied in 6 dogs (12 limbs) to identify muscles most suitable for transposition in the treatment of large wounds. Gross dissection of injected specimens and angiography were used to identify the vascular pedicles. The vascular pedicles to several muscles were generally consistent, and any variations would not interfere with most muscle transfers. The cranial part of the sartorius, gracillis, semitendinosus, and rectus femoris muscles were identified as suitable candidates for transfer. The caudal part of the sartorius, cranial tibial, and long digital extensor muscles have segmentalized vascular patterns that would limit its arc of rotation. 相似文献
93.
The effects of aspirin (75 mg orally/average-size cat) and propranolol (5 mg orally every 8 hours/average-size cat) alone and in combination on hemostatic determinants in healthy cats were studied. In cats, aspirin alone did not cause a significant effect in platelet numbers, plasma fibrinogen, activated partial thromboblastin time, prothrombin time, thrombin time, or platelet aggregation response to adenosine diphosphate. Aspirin did, however, significantly reduce the degree of aggregation induced by acid soluble collagen. Propranolol alone or in combination with aspirin did not cause a significant effect on platelet numbers, plasma fibrinogen, activated partial thromboblastin time, prothrombin time, thrombin time, or platelet aggregation in response to acid soluble collagen, adenosine diphosphate, or adrenaline. It was concluded that aspirin alone at the recommended dosage of one-quarter of a 5-grain tablet (1.25 grains or 75 mg) every other day will significantly affect platelet function and may be of value in the prevention of thromboembolic disease in the cat. 相似文献
94.
95.
Antimicrobial supplementation of growing pigs: the effect of porcine sera fractions on in vitro muscle cell proliferation 总被引:1,自引:0,他引:1
M R Hathaway M S Pampusch S G Cornelius C E Allen W R Dayton 《Journal of animal science》1990,68(11):3642-3648
Sera obtained from pigs before and after subtherapeutic levels of ASP250 supplementation (pre and post serum pools) have been subjected to comparative fractionation by using gel filtration and affinity chromatography on immobilized Cibacron Blue F3G-A. Comparable serum fractions obtained from pre- and post-ASP250 blood sera were assayed in muscle cell culture bioassays designed to measure their effect on proliferation. Pre- and post-ASP250 sera were subjected to gel filtration and divided into the following fractions: fraction 1, Kav less than .17; fraction 2, Kav = .17 to .41; fraction 3, Kav = .41 to .59. Post-ASP250 fractions 2 and 3 increased proliferation rate in cultured muscle cells to a greater extent than comparable pre-ASP250 fractions (P less than .001). Chromatography of fraction 3 on immobilized Cibacron Blue F3G-A showed that both pre- and post-ASP250 fraction 3 contained a putative inhibitor of myogenic cell proliferation as well as mitogenic factors. However, negative growth factor activity was greater in pre-ASP250 fraction 3 than in post-ASP250 fraction 3 (P less than .05). Additionally, positive growth factor activity was lower in pre-ASP250 fraction 3 than in post-ASP250 fraction 3 (P less than .05). These data suggest that levels and(or) activities of both positive and negative muscle growth factors in serum may be altered by the addition of antimicrobials to the diets of growing pigs. 相似文献
96.
A 15-month-old Quarter Horse filly presented for evaluation of hard swellings over the left temporomandibular joint (TMJ) and the right metatarsophalangeal joint (MTPJ). The TMJ swelling had been noted since she was weaned at 4 months of age and had slowly enlarged since then. Radiographs of both TMJs and the right MTPJ were performed, which revealed severe osteoarthrosis associated with osteochondrosis-like lesions. The filly was subjected to euthanasia due to the poor prognosis for performance. Computed tomography and post-mortem examination, including histopathology of the left TMJ, revealed early osteoarthritis (OA) associated with osteochondrosis-like lesions of the left TMJ and the right MTPJ, while the right hind proximal interphalangeal joint (PIPJ) was diagnosed with early OA. 相似文献
97.
98.
Interactions between scarification treatments and seedling types of Norway spruce were examined at two different locations in southern Sweden. The scarification treatments were not scarified control, mounding and soil inversion and the seedling types were a 10 week-old containerized seedling (mini seedling), a 2 year-old containerized seedling and a 2 year-old hybrid seedling, grown as a containerized seedling the first year and as a bare-root seedling the second year. Site preparation intensity had a greater effect on the mini seedlings. The results indicated that mini seedlings established faster in the soil inversion treatment compared to the larger seedling types. At the same seedling age, the mini seedlings had faster or similar growth rate as the containerized and the hybrid seedlings regardless of scarification treatment. Although mini seedlings grew as well as or even better than larger seedlings if they were successfully established, they were more sensitive to their planting environment and proper handling was critical. Problems with frost heaving and competing vegetation have to be taken into consideration when choosing site preparation method and seedling type. 相似文献
99.
A field trial was conducted investigating the single season growth response of 1+0 313 PSB Engelmann spruce (Picea engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. ex Loud.) seedlings planted into two different soil thermal regimes at three high-elevation locations spanning 200 km in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in the Cariboo Mountains of central British Columbia. Temperature treatments represented the extremes of soil temperature commonly found in high-elevation clear-cuts. A warm soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 18 to 25 °C at –10 cm) consisting of a bare mineral soil hummock (average dimensions of 100 cm × 100 cm × 40 cm) was contrasted with a cool soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 10 to 13 °C at –10 cm) comprised of organic forest floor overlying mineral soil. By the end of the growing season, seedlings of both species planted into the warm treatment generally exhibited greater root, stem, foliage, and total seedling biomass than cool treatment seedlings. Measurements of root growth at 30, 60, and 90 days after planting showed that total root number and total root length were consistently greater for warm treatment seedlings than for cool treatment seedlings. Root growth was greater from the bottom rather than from the side of the root plug for all seedlings. These results suggest that the effect of low soil temperatures on outplanted styroblock conifer seedlings is pronounced and may be limiting growth performance in high-elevation plantations in British Columbia. We recommend silvicultural treatments that secure natural regeneration, ensure that warmer microsites are always planted, and utilize seedling stocktypes able to make rapid lateral root growth into warmer surface organic horizons. 相似文献
100.
Lana A. Gyan Chad D. Paetsch Murray D. Jelinski Andrew L. Allen 《The Canadian veterinary journal. La revue veterinaire canadienne》2015,56(11):1134-1139
Gross and histologic postmortem studies were performed on the hind feet of feedlot cattle that had, or were free from, lesions of toe tip necrosis. The hind feet of feedlot cattle were collected by 3 veterinary feedlot practices in southern Alberta, Canada. Three studies of these feet were conducted: i) prediction of disease based on the presence or absence of apical white line separation, ii) gross assessment of the distribution and severity of lesions within affected claws, and iii) microscopic evaluation of the distal phalanx and surrounding soft tissues of affected claws. Prediction of toe tip necrosis based on the presence of apical white line separation was statistically significant (P < 0.0001). This, combined with a pattern of lesions indicative of an ascending infection of the distal phalanx and the absence of other lesions, suggests that the pathogenesis involves bacterial infection originating from the most distal aspect of the toe, at the apical white line. 相似文献