全文获取类型
收费全文 | 1236篇 |
免费 | 73篇 |
专业分类
林业 | 50篇 |
农学 | 24篇 |
基础科学 | 7篇 |
118篇 | |
综合类 | 261篇 |
农作物 | 46篇 |
水产渔业 | 43篇 |
畜牧兽医 | 653篇 |
园艺 | 22篇 |
植物保护 | 85篇 |
出版年
2019年 | 22篇 |
2018年 | 11篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 21篇 |
2013年 | 29篇 |
2012年 | 39篇 |
2011年 | 46篇 |
2010年 | 24篇 |
2009年 | 18篇 |
2008年 | 41篇 |
2007年 | 29篇 |
2006年 | 48篇 |
2005年 | 43篇 |
2004年 | 33篇 |
2003年 | 36篇 |
2002年 | 29篇 |
2001年 | 29篇 |
2000年 | 25篇 |
1999年 | 26篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 25篇 |
1989年 | 29篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1975年 | 15篇 |
1974年 | 16篇 |
1973年 | 12篇 |
1972年 | 18篇 |
1971年 | 10篇 |
1970年 | 14篇 |
1969年 | 12篇 |
1968年 | 10篇 |
1967年 | 11篇 |
1966年 | 10篇 |
排序方式: 共有1309条查询结果,搜索用时 0 毫秒
31.
Nicola M. Hall Bocary Kaya Jan Dick Ute Skiba Amadou Niang Ramadjita Tabo 《Biology and Fertility of Soils》2006,42(3):224-230
The impacts of fallow on soil fertility, crop production and climate-forcing gas emissions were determined in two contrasting
legumes, Gliricidia sepium and Acacia colei, in comparison with traditional unamended fallow and continuous cultivation systems. After 2 years, the amount of foliar
material produced did not differ between the two improved fallow species; however, grain yield was significantly elevated
by 55% in the first and second cropping season after G. sepium compared with traditional fallow. By contrast, relative to the unamended fallow, a drop in grain yield was observed in the
first cropping season after A. colei, followed by no improvement in the second. G. sepium had higher foliar N, K and Mg, while A. colei had lower foliar N but higher lignin and polyphenols. In the third year after fallow improvement, a simulated rainfall experiment
was performed on soils to compare efflux of N2O and CO2. Improved fallow effects on soil nutrient composition and microbial activity were demonstrated through elevated N2O and CO2 efflux from soils in G. sepium fallows compared with other treatments. N2O emissions were around six times higher from this nitrogen-fixing soil treatment, evolving 69.9 ngN2O–N g−1soil h−1 after a simulated rainfall event, compared with only 8.5 and 4.8 ngN2O–N g−1soil h−1 from soil under traditional fallow and continuous cultivation, respectively. The findings indicate that selection of improved
fallows for short-term fertility enhancement has implications for regional N2O emissions for dry land regions. 相似文献
32.
T A Puglisi R W Green C L Hall W K Read R A Green C H Tangner F A Mann H P Hobson 《American journal of veterinary research》1986,47(8):1863-1869
A double-blind study, using metrizamide, iohexol, or Ringer's solution (control) as cisternal myelographic agents, was performed on 25 dogs. Before myelographic examination was done, each dog was subjected to physical, clinical pathologic, and neurologic examinations, as well as examinations by electroencephalography and computerized tomography. These were repeated 24 hours after completion of the myelographic examination. The group of dogs given metrizamide (group II) had a significantly greater occurrence of seizure activity (6 of 10) than did the control dogs (group I; 0 of 5) or dogs given iohexol (group III; 0 of 10; P less than 0.003). In group II, the CSF microprotein concentration was significantly greater 24 hours after myelography was done than were the values in groups I and III (P less than 0.003). Myelograms of the group II dogs (metrizamide) and group III dogs (iohexol) had similar diagnostic qualities. At 24 hours after myelographic examination was done, computerized tomography scan revealed that each dog given metrizamide and iohexol had myelographic contrast material in the brain and cervical spinal cord parenchyma. Seemingly, iohexol has good diagnostic quality, but is less epileptogenic than metrizamide when used in cervical myelographic examinations of dogs. 相似文献
33.
Acetolactate synthase (ALS) from one susceptible and two chlorsulfuronresistant biotypes of Stellaria media(L.) Vill. was assayed in the presence of eight known ALS inhibitors. As expected, ALS from the chlorsulfuronresistant biotypes (R1 and R2) showed reduced sensitivity to chlorsulfuron and other sulfonylurea herbicides. The patterns of cross-resistance varied, however, indicating that the alteration in ALS that confers chlorsulfuron resistance does not confer the same level of resistance to other sulfonylurea herbicides. The resistant biotypes were highly cross-resistant to sulfometuron-methyl and DPX-A7H81, but less cross-resistant to triasulfuron. Both R1 and R2 were highly cross-resistant to DTPS (N-[2,6-dichlorophenyl]-5,7-dimethyl-1,2,4-iriazolo[1,5a]pyrimidine-2-siilfoiiamide), but only slightly cross-resistant to imazamethahenz, an imidazolinone herbicide. The differences in the patterns of cross-resistance observed presumably reflect differences in the binding affinity of the herbicides for the altered ALS. The data presented suggest, but do not confirm, that R1 and R2 contain the same ALS mutation. 相似文献
34.
The properties of the major H+-pumps in higher plant cells are described: these are the H+-ATPase of the plasma membrane and the H+-ATPase and the H+-pyrophosphatase of the tonoplast. They are distinguished by their structure, mechanism of action, kinetic properties, and location within the cell. The uses and value of isolated and purified membrane vesicles in transport studies are discussed. A particular example is given by the use of plasma membrane vesicles, purified by phase partition, to study proton/ sucrose co-transport in Ricinus cotyledons. Current evidence for the interference with these pumps by growth regulators, toxins and xenobiotics is outlined. 相似文献
35.
Effects of dietary change and rotavirus infection on small intestinal structure and function in gnotobiotic piglets 总被引:1,自引:0,他引:1
G A Hall K R Parsons G L Waxler K J Bunch R M Batt 《Research in veterinary science》1989,47(2):219-224
The combined effects of weaning and rotavirus infection on small intestinal structure and function and on growth rate were studied in 28 gnotobiotic piglets. There was little damage by rotavirus to the proximal small intestine, some damage to the mid small intestine and relatively severe damage to the distal small intestine; villi were stunted, crypts lengthened and activities of all brush border enzymes decreased. The damage was short-lived despite the synchronisation of rotavirus infection with simulated weaning. There was no evidence of persistent damage to the small intestine and growth rate was unaffected. 相似文献
36.
Seventeen paragangliomas were identified in a retrospective review of 200 NTP/NCI carcinogenicity studies in F344/N rats that served either as control or treated animals. Most tumors were grossly visible and located in the retroperitoneum adjacent to the vertebrae and aorta near the kidneys. Three microscopically detected paragangliomas were found at the base of the heart. Microscopically, neoplastic cells were in nests separated by reticulin fibers and capillaries. Argyrophil granules were in the cytoplasm of the retroperitoneal and mediastinal paravertebral tumors. Dense granules were found in the one tumor examined ultrastructurally. Some tumors had areas of necrosis and tumor emboli were present in the lumen of the abdominal aorta and vena cava adjacent to the tumor with metastases present in pulmonary vessels. The incidence of retroperitoneal neoplasms was 3 times more frequent in male than in female F344/N rats. 相似文献
37.
38.
39.
40.
S A Hall 《The Veterinary record》1965,77(42):1237-1241