全文获取类型
收费全文 | 145150篇 |
免费 | 7711篇 |
国内免费 | 102篇 |
专业分类
林业 | 6121篇 |
农学 | 4228篇 |
基础科学 | 884篇 |
15878篇 | |
综合类 | 27965篇 |
农作物 | 5574篇 |
水产渔业 | 6622篇 |
畜牧兽医 | 75209篇 |
园艺 | 1660篇 |
植物保护 | 8822篇 |
出版年
2018年 | 1722篇 |
2017年 | 1894篇 |
2016年 | 1768篇 |
2015年 | 1576篇 |
2014年 | 1914篇 |
2013年 | 5171篇 |
2012年 | 3393篇 |
2011年 | 4325篇 |
2010年 | 2759篇 |
2009年 | 2778篇 |
2008年 | 4185篇 |
2007年 | 4063篇 |
2006年 | 3911篇 |
2005年 | 3579篇 |
2004年 | 3453篇 |
2003年 | 3504篇 |
2002年 | 3319篇 |
2001年 | 4399篇 |
2000年 | 4509篇 |
1999年 | 3571篇 |
1997年 | 1397篇 |
1995年 | 1652篇 |
1994年 | 1413篇 |
1993年 | 1384篇 |
1992年 | 3063篇 |
1991年 | 3240篇 |
1990年 | 3199篇 |
1989年 | 3218篇 |
1988年 | 3001篇 |
1987年 | 3045篇 |
1986年 | 3108篇 |
1985年 | 3022篇 |
1984年 | 2455篇 |
1983年 | 2184篇 |
1982年 | 1488篇 |
1981年 | 1368篇 |
1979年 | 2360篇 |
1978年 | 1887篇 |
1977年 | 1656篇 |
1976年 | 1586篇 |
1975年 | 1727篇 |
1974年 | 2229篇 |
1973年 | 2296篇 |
1972年 | 2247篇 |
1971年 | 2092篇 |
1970年 | 1997篇 |
1969年 | 1787篇 |
1968年 | 1548篇 |
1967年 | 1611篇 |
1966年 | 1442篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
181.
182.
Histopathological and hematological findings in myeloid leukemia induced by a new feline leukemia virus isolate 总被引:2,自引:0,他引:2
Myeloid leukemia was induced by a new feline leukemia virus isolate FeLV-AB/GM-1 in a high proportion of cats. The latency period was short. Three to 5 weeks after infection early changes were detectable in the bone marrow, and cats developed leukemia 5 to 8 weeks after infection. The results of the present histological and cytological studies suggested that there were two stages in the development of leukemia. The first stage appeared to be equivalent to the syndrome of bone marrow dysplasia or preleukemia which, however, converted rapidly to leukemia. Cytopenia(s) were the main hematological findings in all preleukemic and leukemic cats. White blood cell counts were low or normal, but the number of leukemic and abnormal cells increased in the peripheral blood with the progression of the disease. This reliable model system lends itself to further studies to elucidate the pathogenesis of myeloproliferative disorders. 相似文献
183.
Canine distal renal tubular acidosis and urolithiasis 总被引:1,自引:0,他引:1
D J Polzin C A Osborne F W Bell 《Veterinary Clinics of North America: Small Animal Practice》1986,16(2):241-250
Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure. 相似文献
184.
The survival of Leptosphaeria maculans , which causes phoma stem canker (blackleg), on oilseed rape residues ( Brassica napus ) in South Australia was investigated. Using a quantitative polymerase chain reaction (PCR) assay for L. maculans DNA, the pathogen was mainly detected in the upper 5 cm of the soil profile, including residues on the soil surface. As the size of organic matter particles in the soil decreased, so did the quantity of L. maculans detected in them. To obtain representative data for a field, at least 30 subsamples needed to be collected over the 0·81 ha area studied. In a survey of 49 commercial fields in South Australia, most L. maculans was detected in fields 1 year after oilseed rape had been grown, with less detected after 2 years and negligible amounts 3 years or more after cropping. The diagnostic DNA-based assay for L. maculans reduced the time and cost of studying L. maculans survival in soil and increased the sensitivity and accuracy of results compared with estimates of propagule number of colony-forming units on a semiselective medium. 相似文献
185.
ANTHONY W. P. BASHER BVetMed mrcvs MARY C. WALTER dvm CHARLES D. NEWTON dvm ms Diplomateacvs 《Veterinary surgery : VS》1986,15(5):356-362
The medical records from 95 cases of coxofemoral luxation in dogs and cats were reviewed. Unilateral craniodorsal luxation was most common, (78.1% of dogs, 72.7% of cats). Trauma from being struck by an automobile was the most frequent cause (59.0%). Treatment was closed (manual) or open (surgical) reduction. The failure rate following single closed reduction was 64.8%. The surgical reduction procedure included capsular repair (capsulorrhaphy) via a craniolateral approach to the hip or via trochanteric osteotomy or gluteal tenotomy. The success rate following reduction via the craniolateral approach was 82%; no failure was recorded with trochanteric transposition, but reluxa-tion followed the single gluteal tenotomy. The Ehmer sling was the most common external fixation and was kept in place an average of 12.5 days. Thirty-three animals were available for follow-up, and no difference was recorded in limb function between the two groups of animals treated by closed vs surgical reduction. Patients with degenerative joint disease at the time of luxation were less likely to be successfully reduced; 64.3% of these animals were eventually treated by femoral head and neck excision. Thirty-eight patients had associated major injuries. Long-term follow-up results were better in those patients with concomitant orthopedic injuries than in those without other injuries. 相似文献
186.
At a site in Kent, perennial ryegrass (Lolium perenne) variety S24 and Italian ryegrass (L. multiflorum) variety RVP, wheat varieties Armada and Norman, and the original mixed grass ley were grown in small plots during 1982–84. Two toxic pesticides (phorate and aldicarb) were applied to half the total number of plots three times each year to eliminate soil invertebrate populations. Fertilizer was also applied to most plots. The yields of the crops, grown with and without pesticide, and the effects of the fertilizer were compared. Grass herbage yield was measured on three occasions during the summers of 1983 and 1984. Wheat grain yields were also determined in 1983. During the first year significant differences were not apparent in grass dry matter yield between pesticide-treated and non-treated plots, but significant differences were found in the second year. The perennial ryegrass was more susceptible to pest damage than the Italian ryegrass or the grass ley. Grass yields varied between cuts and in relation to variety and pesticide treatment, yields tending to be greater in untreated plots. Fertilizer treatment greatly increased grass dry matter yields, particularly with the Italian ryegrass. The effects of pesticide treatment on both wheat varieties varied although some yield enhancement was evident. Invertebrate animal populations in pesticide and fertilizer-treated plots were also assessed in autumn 1982, spring and autumn 1983 and spring 1984. In contrast to pesticide treatment, fertilizer treatment had little effect on soil invertebrate populations. Nematode populations were reduced at each sampling occasion by the pesticide treatment. Slug populations were initially unaffected but were subsequently reduced. Leatherjackets, by far the most abundant pest in both grass and wheat plots, were markedly affected by pesticides on all sampling occasions. Generally, fewer soil-dwelling dipterous larvae were recovered in spring than in autumn. Stem-boring dipterous larvae were virtually absent. 相似文献
187.
188.
189.
190.