全文获取类型
收费全文 | 1600篇 |
免费 | 69篇 |
专业分类
林业 | 185篇 |
农学 | 52篇 |
基础科学 | 21篇 |
261篇 | |
综合类 | 136篇 |
农作物 | 63篇 |
水产渔业 | 96篇 |
畜牧兽医 | 749篇 |
园艺 | 19篇 |
植物保护 | 87篇 |
出版年
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 34篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 31篇 |
2015年 | 28篇 |
2014年 | 34篇 |
2013年 | 73篇 |
2012年 | 55篇 |
2011年 | 81篇 |
2010年 | 39篇 |
2009年 | 48篇 |
2008年 | 86篇 |
2007年 | 82篇 |
2006年 | 58篇 |
2005年 | 63篇 |
2004年 | 56篇 |
2003年 | 52篇 |
2002年 | 53篇 |
2001年 | 38篇 |
2000年 | 36篇 |
1999年 | 39篇 |
1998年 | 13篇 |
1997年 | 18篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 25篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1975年 | 18篇 |
1974年 | 17篇 |
1973年 | 12篇 |
1972年 | 13篇 |
1971年 | 12篇 |
1969年 | 14篇 |
1967年 | 15篇 |
1932年 | 12篇 |
排序方式: 共有1669条查询结果,搜索用时 15 毫秒
111.
112.
Procollagen type-III aminoterminal peptide in serum and synovial fluid of dogs with hip dysplasia and coxarthrosis 总被引:1,自引:0,他引:1
J S Madsen L T Jensen H Str?m K H?rslev-Petersen E Svalastoga 《American journal of veterinary research》1990,51(10):1544-1546
Hip dysplasia is an affection of the coxofemoral joint that progresses until stabilization is caused by fibrosis and osteoarthritic changes. This stabilization process can be examined by clinical and radiographic methods. The capability of evaluating the procollagen concentrations in liquids, such as serum and synovial fluid, has further offered the basis for an objective biochemical evaluation of the stabilization process. Our study was performed to evaluate whether determination of procollagen concentrations was suitable for the use in practice. The procollagen type-III aminoterminal peptide (P-III-NP) concentration was measured in serum and in synovial fluid from coxofemoral joints in 20 dogs. Dogs were grouped on the basis of evidence of dysplasia and osteoarthritic changes of the hip: (1) a control group of 6 dogs without clinical or radiographic signs of hip dysplasia, and (2) dysplastic group of 14 dogs, which was further grouped with respect to the coxofemoral joint laxity, as determined by the Ortolani test. Synovial fluid concentration of P-III-NP was significantly (P less than 0.05) higher in fluid from dysplastic joints than in fluid from normal joints. Serum concentrations of P-III-NP were significantly (P less than 0.05) higher in dogs in which results of the Ortolani test were positive. 相似文献
113.
Plasma and joint fluids from turkeys experimentally inoculated with Chlamydia psittaci strain TT3 were evaluated by immunoblotting to identify antibodies elicited by chlamydial antigens during the course of infection. Protein antigens from elementary bodies of TT3 were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred electrophoretically to nitrocellulose before being probed with plasma or synovial fluid from TT3-inoculated birds. The major outer-membrane protein (MOMP), the 60,000-molecular-weight proteins, and a 97,400-molecular-weight protein were the predominant antigens recognized by IgG in the plasma and joint fluids. Plasma IgG specific for the 97,400 protein band was first detectable at day 10 postinoculation (PI). Antibodies to the 60,000-molecular-weight protein and MOMP were first detected at days 14-17 PI and at days 7-10 PI, respectively, in some birds, and as late as days 36-42 PI and days 42-70 PI in others. The antibodies were still present at day 142 PI. Immunoblotting techniques indicated that the antigens to which these antibodies were reacting were protein. These observations may have implications for the development of serodiagnostic assays as well as the identification of potential proteins for subunit immunogens in birds. 相似文献
114.
Larry D. Galuppo DVM Diplomate ACVS Susan M. Stover DVM PhD Diplomate ACVS David G. Jensen BS Neil H. Willits PhD 《Veterinary surgery : VS》2001,30(4):332-340
OBJECTIVE: To compare drilling, tapping, and screw-insertion torque, force, and time for the 4.5-mm AO and 6.5-mm Acutrak Plus (AP) bone screws, and to compare the mechanical shear strength and stiffness of a simulated complete lateral condylar fracture of the equine third metacarpal bone (MC3) stabilized with either an AO or AP screw. STUDY DESIGN: In vitro biomechanical assessment of screw-insertion variables, and shear failure tests of a bone-screw-stabilized simulated lateral condylar fracture. SAMPLE POPULATION: Eight pairs of cadaveric equine MC3s METHODS: Metacarpi were placed in a fixture and centered on a biaxial load cell in a materials-testing system to measure torque, compressive force, and time for drilling, tapping, and screw insertion. Standardized simulated lateral condylar fractures were stabilized by either an AO or AP screw and tested in shear until failure. A paired t test was used to assess differences between screws, with significance set at P < .05. RESULTS: Insertion and mechanical shear testing variables were comparable for AO and AP insertion equipment and screws. CONCLUSION: The 6.5-mm tapered AP screw can be inserted in equine third metacarpal condyles and is mechanically comparable with the 4.5-mm AO screw for fixation of a simulated lateral condylar fracture. CLINICAL RELEVANCE: Considering the comparable mechanical behavior, the potential for less-persistent soft-tissue irritation with the headless design, and the ability to achieve interfragmentary compression by inserting the screw in one hole drilled perpendicular to the fracture plane, the 6.5-mm tapered AP screw may be an attractive alternative for repair of incomplete lateral condylar fractures in horses. 相似文献
115.
A nasal, so called ethmoidal, tumor from a fallow deer is described. It appears to be the first reported case of that species. The etiology is discussed. 相似文献
116.
To investigate the microbial and nutritional characteristics of dry feed, liquid feed containing fermented liquid cereal grains, and fermented liquid feed, and their effect on gastrointestinal ecology and growth performance, 120 piglets from 40 litters were used and housed in pens with 5 animals in each. The 3 dietary treatments (all nonheated and nonpelleted diets) were: a dry meal diet (DRY); a fermented, liquid cereal grain feed (FLG); and a fermented liquid feed (FLF). The FLG diet was prepared by storing the dietary cereals (barley and wheat) and water (1:2.5, wt/wt) in a closed tank at 20 degrees C and adding the remaining dietary ingredients immediately before feeding. The FLF diet was prepared by storing compound feed and water (1:2.5, wt/wt) in a closed tank at 20 degrees C. Three times daily, 50% of the fermented cereals or compound feed and water stored in the tanks was removed and replaced with an equal amount of fresh cereals or feed and water. On d 14, 1 piglet from each pen was killed and samples from the gastrointestinal tract were obtained. The pH of the fermented cereals was 3.85 (SD = 0.10), that of the FLG diet was 5.00 (SD = 0.18), and the pH of the FLF diet was 4.45 (SD = 0.11). The dietary concentration of lysine (g/16 g of N) pointed to a decreased concentration in the FLF (5.46, SD = 0.08) compared with the DRY (6.01) and FLG (6.21, SD = 0.27) diets, and the concentration of cadaverine was greater in the FLF diet (890 mg/kg, SD = 151.3) than in the DRY (32 mg/kg) or FLG (153 mg/kg, SD = 18.7) diets. Fermenting only the cereal component of the diet (FLG) promoted the growth of yeasts to a greater extent than fermenting the whole diet (FLF). Terminal RFLP profiles of diets and digesta from the stomach and midcolon showed differences among dietary groups. The number of yeasts able to grow at 37 degrees C in the stomach and caudal small intestine was greatest in the FLG group compared with the other 2 dietary groups (P < 0.01). In the cecum and colon, the differences were only significant between piglets fed the FLG and the FLF diets (P < 0.05). The greatest number of yeasts able to grow at 20 degrees C was detected in the animals fed the FLG diet. However, the values were different from the FLF-fed piglets only in the stomach (P < 0.05) and midcolon (P < 0.05). There was a tendency (P < 0.10) for greater ADG of the piglets fed the FLG compared with the FLF diet. Feeding liquid feed containing fermented, liquid cereal grains as a means of avoiding microbial decarboxylation of free amino acids in the feed and increasing feed intake by improving palatability seems promising but requires further investigation. 相似文献
117.
A 19-year-old horse that was one of a group of six horses infected experimentally with Anaplasma phagocytophilum for a study of the pathogenesis of equine granulocytic ehrlichiosis died suddenly two days after first showing clinical signs of disease. The clinical signs and laboratory findings observed before its death were similar to all those of the other infected horses, and to previous reports of this disease. A postmortem examination revealed widespread haemorrhaging in its internal organs, and vasculitis and thrombosis in the kidneys. These changes are consistent with disseminated intravascular coagulation, which has previously been reported in human beings infected with the presumably identical agent of human granulocytic ehrlichiosis. 相似文献
118.
119.
Two transgenic Bt rice lines, KMD1 and KMD2, both containing a synthetic cry1Ab gene from Bt, were crossed with conventional rice varieties. The inheritance of resistance to SSB of KMD1 and KMD2was investigated
through LSB and field examination of their progenies, e.g. F1, BC1 and F2 populations. In LSBs, 100.0% of newly hatched SSB larvae died on the second day after feeding on leaf tissues of F1 and GUS positive BC1 plants, of which the area of leaf tissues consumed by SSB is also similar to that of transgenic parents. These results imply
that the resistance of Bt rice to SSB is dominantly controlled and could be easily exploited in hybrid rice production. Field
evaluation showed that segregation ratios for SSB resistance to susceptibility in BC1 populations fit the ratio of 1:1, which was also confirmed by LSBs. However, in F2 populations, the ratio was significantly smaller than 3:1 for resistant to susceptible plants in all 6 indica × japonica
(KMD1 and KMD2) crosses, though it fitted 3:1 in all 4 japonica × japonica crosses. The results implied that the resistance
of Bt rice to SSB was controlled by a dominant gene which was present in a homozygous condition in both KMD1 and KMD2, but
the inheritance could be affected by other factors. Assays for Cry1Ab protein showed that, in most crosses, the content of
Cry1Ab is significantly higher in leaves of GUS positive F1, BC1 and F2 plants than that in transgenic Bt parent plants, which accounts for the high resistance observed in these plants to SSB.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
120.
A total of 4,681 accessions of Hordeum vulgare landrace material from Ethiopia, East Mediterranean, Near East, Nepal and China
were sown in the field and subjected to the natural powdery mildew epidemic in Denmark. Apparently resistant accessions were
selected. Selfed progeny from them were retested and reselected in subsequent years at four locations in Denmark. Finally,
16 promising donors of resistance were retained. They were characterized in the field and tested in the seedling stage for
reaction to up to 72 different isolates of the powdery mildew fungus. The absence of the corresponding virulences in the Danish
airborne powdery mildew population was ascertained in five years. The resistances in the 16 donors are apparently mutually
different and from known sources of powdery mildew resistance in barley.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献