全文获取类型
收费全文 | 189192篇 |
免费 | 10299篇 |
国内免费 | 118篇 |
专业分类
林业 | 8475篇 |
农学 | 6227篇 |
基础科学 | 1133篇 |
22965篇 | |
综合类 | 31332篇 |
农作物 | 7345篇 |
水产渔业 | 9425篇 |
畜牧兽医 | 98106篇 |
园艺 | 2467篇 |
植物保护 | 12134篇 |
出版年
2019年 | 1702篇 |
2018年 | 2720篇 |
2017年 | 2970篇 |
2016年 | 2799篇 |
2015年 | 2437篇 |
2014年 | 3014篇 |
2013年 | 7470篇 |
2012年 | 5344篇 |
2011年 | 6427篇 |
2010年 | 4347篇 |
2009年 | 4320篇 |
2008年 | 6392篇 |
2007年 | 6290篇 |
2006年 | 5856篇 |
2005年 | 5401篇 |
2004年 | 5223篇 |
2003年 | 5281篇 |
2002年 | 4894篇 |
2001年 | 6044篇 |
2000年 | 5951篇 |
1999年 | 4852篇 |
1998年 | 1913篇 |
1997年 | 1909篇 |
1996年 | 1751篇 |
1995年 | 2150篇 |
1994年 | 1765篇 |
1993年 | 1821篇 |
1992年 | 3736篇 |
1991年 | 3909篇 |
1990年 | 3983篇 |
1989年 | 3953篇 |
1988年 | 3664篇 |
1987年 | 3614篇 |
1986年 | 3593篇 |
1985年 | 3481篇 |
1984年 | 2845篇 |
1983年 | 2548篇 |
1982年 | 1741篇 |
1979年 | 2592篇 |
1978年 | 2056篇 |
1977年 | 1789篇 |
1976年 | 1738篇 |
1975年 | 1898篇 |
1974年 | 2298篇 |
1973年 | 2407篇 |
1972年 | 2365篇 |
1971年 | 2149篇 |
1970年 | 2138篇 |
1969年 | 1948篇 |
1967年 | 1740篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
The complement fixation test (CFT), the enzyme labelled immunosorbent assay (ELISA) and the gel diffusion precipitin test (GD) were compared, for the diagnosis of Brucella ovis infection in rams. The sensitivities of the tests in 109 rams which were shedding B. ovis in their semen were: CFT 96.3%; ELISA 97.2%; GD 91.7%. The specificities of the tests in 141 rams from non-infected flocks were: CFI 99.3%; ELISA 98.6%; GD 100%. Predictive values of the three tests were measured in 285 rams from infected flocks. Thirty-eight percent of these rams were shedding B. ovis in their semen. Predictive values of positive tests were: CFT 75.5%; ELISA 66.7%; GD 72.5%. Predictive values of negative tests were: CFI 97.1%; ELISA 97.6%; GD 93.8%. 相似文献
953.
Two lactational intramammary antibiotic preparations (cloxacillin and oxytetracycline) were each used to treat eight goats by intramammary infusion in one half. The rate of release of the antibiotics was monitored by a diffusion assay based on the sensitive organism Bacillus stearothermophilus var. calidolactis. Cloxacillin was still detectable 156 hours after the final treatment while oxytetracycline was undetectable 108 hours following treatment. A small but significant amount of antibiotic was translocated between treated and untreated halves of the udder in both cases. 相似文献
954.
Hirsch VM Mitcham SC Dunn DK 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1984,13(2):16-20
An unusual combination of blood cytopenias and monocytic proliferation was observed in a dog. Initial hematologic findings included severe thrombocytopenia, neutropenia, mild nonregenerative anemia and apparently normal bone marrow. Subsequently, a severe persistent monocytosis developed and the bone marrow became populated with monocytes and cytophagic macrophages. Splenomegaly was due to reticuloendothelial hyperplasia and extramedultary hematopoiesis. Treatment consisted of splenectomy and azathioprine but the response was poor and the dog was euthanized. Postmortem examination revealed a hypocellular bone marrow which contained moderate numbers of monocytes and plasma cells. Neoplastic proliferation was absent in visceral organs. No definite diagnosis was established; chronic blood cell consumption, perhaps immune-mediated, may have been responsible for the extensive reticuloendothelial hyperplasia and cytophagia. 相似文献
955.
Factors affecting somatic cell counts and the association between somatic cell counts and milk production were evaluated. Data were collected from 748 Ontario Dairy Herd Improvement Corporation supervised herds that were on production and somatic cell count programs between April 1981 and March 1983. Two data files were created; one, the lactation summary file, contained one record per cow on each of 9406 Holsteins and the other, the test day file, included results of all tests during the complete lactation on each of the above cows. The latter file contained 85,236 records. Multiple curvilinear least squares regression was used to create five separate models. The dependent variables used in the models were natural logarithms (Loge) of the geometric mean of the somatic cell count for the lactation, 305 day milk production and breed class average for milk from the lactation summary file, and loge of the 24 hour somatic cell count and 24 hour milk production from the test day file. The somatic cell count at both the lactation and test day level increased with age up to approximately ten years and thereafter slowly decreased. The variable "days in milk" was not significantly associated with the lactation average somatic cell count. A curvilinear relationship was found between days in lactation at the time of test and the somatic cell count of 24 hour milk production. The somatic cell count increased until approximately 250 days in lactation and thereafter slowly decreased. It was found that the highest cell counts occurred in summer and the lowest in winter.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
956.
Cysts found in the liver of a horse which had never been out of New Zealand were used to infect two dogs which were slaughtered 35 days after infection. Large numbers of Echinococcus granulosus were recovered. These cestodes were compared with mature dog-sheep cestodes, using light and scanning electron microscopy and identified as the dog-horse strain of E.granulosus. 相似文献
957.
A series of 10 farm trials was conducted in which the lambing performance of ewes immunised against polyandroalbumin was compared with that of untreated ewes in the same flock. The trials show that polyandroalbumin treatment is a reliable method of increasing lambing and tailing percentages in New Zealand flocks. An average of 39 extra lambs born per 100 ewes tupped was achieved on farms where ewes were given two treatments about four weeks apart and rams were introduced 18-26 days after the second dose. On farms where rams were introduced less than 12 days after this booster injection an average of 19 extra lambs born per 100 ewes tupped resulted. On farms where rams were introduced at 18-26 days post booster injection an average of 35 extra lambs were tailed for every 100 ewes tupped. The response for immunization increased in direct relation to the liveweight of the ewes at tupping. 相似文献
958.
The cleistogamous species Collomia grandiflora produces dimorphic cross-incompatible flowers on a single plant. The open or chasmogamous flower has smaller, flask-shaped stigmatic papillae, larger pollen grains, longer styles, and faster pollen tube growth rates down the style than the closed or cleistogamous flower. In intermorph crosses, pollen tube growth rates are greatly decreased and fertilization does not occur. 相似文献
959.
960.