全文获取类型
收费全文 | 145143篇 |
免费 | 7564篇 |
国内免费 | 103篇 |
专业分类
林业 | 6116篇 |
农学 | 4223篇 |
基础科学 | 884篇 |
15852篇 | |
综合类 | 27927篇 |
农作物 | 5574篇 |
水产渔业 | 6619篇 |
畜牧兽医 | 75159篇 |
园艺 | 1652篇 |
植物保护 | 8804篇 |
出版年
2018年 | 1724篇 |
2017年 | 1888篇 |
2016年 | 1762篇 |
2015年 | 1576篇 |
2014年 | 1910篇 |
2013年 | 5161篇 |
2012年 | 3390篇 |
2011年 | 4311篇 |
2010年 | 2755篇 |
2009年 | 2774篇 |
2008年 | 4182篇 |
2007年 | 4052篇 |
2006年 | 3907篇 |
2005年 | 3570篇 |
2004年 | 3448篇 |
2003年 | 3495篇 |
2002年 | 3313篇 |
2001年 | 4394篇 |
2000年 | 4510篇 |
1999年 | 3571篇 |
1998年 | 1366篇 |
1997年 | 1395篇 |
1995年 | 1651篇 |
1994年 | 1410篇 |
1993年 | 1382篇 |
1992年 | 3064篇 |
1991年 | 3235篇 |
1990年 | 3201篇 |
1989年 | 3212篇 |
1988年 | 3000篇 |
1987年 | 3042篇 |
1986年 | 3105篇 |
1985年 | 3021篇 |
1984年 | 2451篇 |
1983年 | 2181篇 |
1982年 | 1484篇 |
1979年 | 2359篇 |
1978年 | 1884篇 |
1977年 | 1656篇 |
1976年 | 1586篇 |
1975年 | 1727篇 |
1974年 | 2228篇 |
1973年 | 2295篇 |
1972年 | 2244篇 |
1971年 | 2093篇 |
1970年 | 1996篇 |
1969年 | 1786篇 |
1968年 | 1546篇 |
1967年 | 1609篇 |
1966年 | 1442篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
A 14-month-old spayed female domestic short-haired cat was presented for evaluation of a rostral mandibular mass diagnosed from biopsy as an ameloblastic fibroma. Radiographs of the mandible demonstrated marked osteolysis and cortical expansion. A rostral mandibulectomy was performed extending from the caudal edge of the second premolar on the right side to the caudal edge of the canine tooth on the left side. Histological evaluation of the excised mass confirmed the diagnosis of ameloblastic fibroma. Follow-up evaluation at eight months revealed normal oral function with the exception of occasional saliva soiling of the chin. The owner was satisfied with the cosmetic result. 相似文献
932.
933.
Syringomyelia in cavalier King Charles spaniels: the relationship between syrinx dimensions and pain 总被引:1,自引:0,他引:1
Rusbridge C Carruthers H Dubé MP Holmes M Jeffery ND 《The Journal of small animal practice》2007,48(8):432-436
OBJECTIVES: This study was designed to test the hypothesis that pain associated with syringomyelia in dogs is dependent upon size and involvement of the dorsal part of the spinal cord. METHODS: Masked observers determined syrinx dimensions and precise location within the spinal cord on magnetic resonance images of 55 cavalier King Charles spaniels with syringomyelia. After removal of masking, syrinx size and location were compared between the cohorts of dogs that exhibited pain with those that did not. RESULTS: Maximum syrinx width was the strongest predictor of pain, scratching behaviour and scoliosis in dogs with syringomyelia. Both pain and syrinx size were positively correlated with syrinxes located in the dorsal half of the spinal cord. CLINICAL SIGNIFICANCE: Large syrinxes associated with damage to the dorsal part of the spinal cord are associated with persistent pain suggesting that the pain behaviour expressed by this group of patients is likely to be "neuropathic pain," resulting from disordered neural processing in the damaged dorsal horn. As such it is likely that conventional analgesic medication may be ineffective. 相似文献
934.
Genetic correlations between phenotypically similar or related traits tested at young horse performance tests for Danish Warmblood (DWB) and Swedish Warmblood (SWB) horses were calculated using Multi-trait Across Country Evaluation (MACE). Data comprised stallions with an estimated breeding value (EBV) from the national genetic evaluations (NGE) based on at least 10 progeny tested in performance tests, and the ancestors of those stallions in two generations. The DWB data included 349 stallions and the SWB data 426 stallions. Of these, 28 had EBVs in both DWB and SWB. Additionally 151 pedigree animals were common between DWB and SWB. The dependent variables used were NGE results of stallions born 1980 and later, which reduced the number of common stallions with EBVs to 23. The genetic correlations were very high for jumping traits (0.99) and dressage related traits (0.89–0.97). For conformation traits correlations varied between 0.10 and 0.98. Because of the high genetic correlations and frequent use of same or closely related foreign stallions, breeders of both DWB and SWB would benefit from using the NGEs for performance traits across countries, although the genetic correlations do not consider differences in genetic merit levels between the populations. It would be feasible to perform a joint genetic evaluation using MACE, which would improve the reliability of estimated breeding values, and enable ranking of all stallions according to the national scale of each country. 相似文献
935.
To determine the effects of blends of high-moisture harvested sorghum grain (HMS) and dry-rolled corn (DRC) on site and extent of digestion, high-grain diets were fed to Angus-Hereford heifers (315 kg) in a 5 x 5 latin square. The grain portion consisted of ratios (HMS:DRC) of 0:100, 25:75, 50:50, 75:25 and 100:0. Heifers were equipped with ruminal, duodenal and ileal T-type cannulas. Digestibilities of OM (P less than .05) and non-ammonia nitrogen (NAN; P less than .01) in the total tract declined linearly as HMS replaced DRC. Chyme flow (liters/d) through the duodenum increased linearly (P less than .01), and true ruminal OM disappearance tended to decline linearly (P less than .10) as HMS replaced DRC. A quadratic response (P less than .05) in extent of starch disappearance (g/d) in the rumen was noted; blends were lower than either individual grain. Ruminal escape of feed N tended to be quadratic (P less than .10); values for individual grain types were greater than blends. Microbial efficiency increased linearly (P less than .05) as HMS replaced DRC. Extent of starch digestion in the rumen averaged 82.7% compared to only 2.9% in the small intestine and 5.7% in the large intestine. Altering the ratio of HMS to DRC appeared to have more effect on ruminal fermentation than on digestion in the small intestine; most starch and nitrogen responses were quadratic. Increases in ruminal pH and chyme flow, potentially caused by increased salivary flow, may cause non-linear changes in the solubility of proteins in HMS and DRC, when fed as blends, altering the digestibility of protein and starch from values predicted from the individual grains. 相似文献
936.
Ruppanner R Behymer DE Paul S Miller JM Theilen GH 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(6):192-195
Test and corrective management was applied in one dairy herd (130 milking cows) to control bovine leukemia virus infection. It consisted of: raising uninfected calves in order to establish a pool of uninfected replacement heifers, preventing transmission of bovine leukemia virus through transfer of blood from animal to animal and closing the herd. Regular herd testing was combined with selected changes in herd management. These procedures have been followed since January 1979. Prevalence of antibodies (as determined by gel-immunodiffusion) has declined markedly since the program was implemented. 相似文献
937.
B.A.N. Silva R.F.M. Oliveira J.L. Donzele H.C. Fernandes M.L.T. Abreu J. Noblet C.G.V. Nunes 《Livestock Science》2006,105(1-3):176-184
Forty Landrace × Large White lactating sows were used to evaluate the effects of cooling of the floor when maintained under high temperature conditions during summer on their productive and reproductive performance. The sows were allocated in a completely randomized design with two treatments with 20 replicates according to parity number and body weight, with each animal being considered an experimental unit. The treatments consisted of cooling of the floor under the sow with water circulation at about 17 °C and no cooling. The resulting temperatures of the floor were 27.6 and 35.8 °C for the cooled and the control treatments, respectively. The sows from both treatments were exposed to average maximum and minimum environmental temperatures of 26.9 and 20.8 °C, respectively. Sows maintained on a cooled floor had a higher feed intake (6.47 vs. 5.61 kg/day; P < 0.01). Despite this higher intake, sows maintained on a cooled floor had higher body weight and body protein losses during the lactation period (P < 0.01) in connection with a higher milk yield and subsequent growth of the litter (2280 vs. 1798 g/day; P < 0.01). There was an effect of treatment on rectal temperature, surface temperatures and respiratory rate (P < 0.01) with lower values in sows submitted to floor cooling. It is concluded that floor cooling under the lactating sow improves its productive and reproductive performance, as well as the performance of its litter. 相似文献
938.
ABSTRACT Monilinia vaccinii-corymbosi infects open blueberry flowers via the gynoecial pathway, leading to mummification of the developing fruit. To determine the effect of flower age on infection, stigmata were inoculated with conidia of M. vaccinii-corymbosi between 0 and 5 days after anthesis, fungal growth rates through the stylar canal were measured in detached flowers in the laboratory, and fruit disease incidence was determined in plants grown in the greenhouse. Hyphal growth rates were greatest in flowers inoculated on the day of anthesis, declined linearly with increasing flower age at inoculation (r = 0.921; P < 0.0001; n = 12), and were unaffected by the presence or absence of pollen applied at the time of inoculation. In greenhouse-grown plants, the percentage of infected fruit decreased exponentially with increasing flower age at inoculation (R = 0.878; P = 0.0057; n = 10), with disease incidence ranging from 76.4% for flowers inoculated on the day of anthesis to 15.5% for those inoculated 4 days later. Fruit disease incidence in the greenhouse was linearly correlated with hyphal growth rates in detached flowers (r = 0.985; P < 0.0001; n = 9), justifying the use of detached flowers when investigating gynoecial infection by M. vaccinii-corymbosi. In separate experiments, the effects of timing and sequence of pollination and inoculation on hyphal growth rates through the stylar canal and on disease incidence were investigated. Application of pollen to detached flowers 1 or 2 days before inoculation reduced hyphal growth rates by between 14.0 and 42.9% compared with flowers that received pollen and conidia simultaneously. Similarly, reductions in fruit disease incidence by between 9.5 and 18.3% were observed on greenhouse-grown plants for pollination-to-inoculation intervals ranging from 1 to 4 days. These results document that newly opened flowers are most susceptible to infection by M. vaccinii-corymbosi and that fruit disease incidence is reduced if pollination occurs at least 1 day before inoculation. Strategies that lead to early pollination of newly opened flowers may be useful for managing mummy berry disease in the field. 相似文献
939.
An investigation was conducted near the industrial areas of West Bengal, Indian subtropics to study the effect of emissions through various factories and thermal power plants on the quality of water in lakes, tanks, ponds, even well waters in relation to its use in the welfare of the society (agricultural use, psciculture and other domestic uses). The results showed that intensity of acidity (water pH) as well as concentration of various soluble salts and BOD and COD in the vicinity of an industrial area (i.e. within 100 metres) were very low. A substantially higher acidity and ion concentration were recorded up to 1 km away from industry, where the growth of aquatic plants, organisms and the production of fish (in lakes and tanks) were severely affected. The results further indicated that the acidity of water gradually increases up to pH 5.4 and concentration of sulphates and chlorides (880 and 570 mg 1?1 respectively) between 1–2 km from the industriy, suggesting that aquatic ecosystems and domestic, agricultural and fish production are less affected with increasing distance from industry. 相似文献
940.