全文获取类型
收费全文 | 237388篇 |
免费 | 13103篇 |
国内免费 | 145篇 |
专业分类
林业 | 9748篇 |
农学 | 8247篇 |
基础科学 | 1601篇 |
30091篇 | |
综合类 | 39545篇 |
农作物 | 9393篇 |
水产渔业 | 12262篇 |
畜牧兽医 | 121059篇 |
园艺 | 3249篇 |
植物保护 | 15441篇 |
出版年
2019年 | 2279篇 |
2018年 | 3535篇 |
2017年 | 4004篇 |
2016年 | 3746篇 |
2015年 | 3191篇 |
2014年 | 3965篇 |
2013年 | 9518篇 |
2012年 | 6999篇 |
2011年 | 8579篇 |
2010年 | 5785篇 |
2009年 | 5675篇 |
2008年 | 8311篇 |
2007年 | 7970篇 |
2006年 | 7631篇 |
2005年 | 6912篇 |
2004年 | 6648篇 |
2003年 | 6732篇 |
2002年 | 6266篇 |
2001年 | 7812篇 |
2000年 | 7615篇 |
1999年 | 6088篇 |
1998年 | 2598篇 |
1997年 | 2560篇 |
1996年 | 2306篇 |
1995年 | 2704篇 |
1994年 | 2382篇 |
1993年 | 2408篇 |
1992年 | 4826篇 |
1991年 | 5021篇 |
1990年 | 4906篇 |
1989年 | 4993篇 |
1988年 | 4477篇 |
1987年 | 4563篇 |
1986年 | 4580篇 |
1985年 | 4357篇 |
1984年 | 3531篇 |
1983年 | 3150篇 |
1982年 | 2203篇 |
1979年 | 3036篇 |
1978年 | 2447篇 |
1977年 | 2098篇 |
1976年 | 2046篇 |
1975年 | 2277篇 |
1974年 | 2676篇 |
1973年 | 2725篇 |
1972年 | 2564篇 |
1971年 | 2380篇 |
1970年 | 2422篇 |
1969年 | 2284篇 |
1967年 | 1984篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Christa Horvath-Ungerboeck Keith L. Thoday Darren J. Shaw Adri H. M. van den Broek 《Veterinary dermatology》2009,20(4):233-242
Thirty dogs with atopic dermatitis were given tepoxalin (Zubrin®, Intervet/Schering-Plough Animal Health, Boxmeer, the Netherlands) or placebo once daily for 4 weeks, followed by a wash-out period of 1 week before reversing the treatments. Pruritus was scored by the owners using the Edinburgh Pruritus Scale and one investigator employed a modification of the Canine Atopic Dermatitis Extent and Severity Index-01 (mCADESI-01) to score the physical lesions. After administration of tepoxalin there was a ≥ 50% reduction in pruritus and mCADESI-01 scores in 36% and 25% of the dogs, respectively, whereas following administration of the placebo there was a ≥ 50% reduction in pruritus and mCADESI-01 scores in only 25% and 16% of the dogs, respectively. Analysis of pooled data indicated that tepoxalin resulted in a significant reduction in pruritus ( P = 0.012) and mCADESI-01 ( P = 0.002) scores but there was no significant change after placebo. The median pruritus scores before and after tepoxalin were 2 (range 1–5) and 1 (range 0–5), respectively, and before and after placebo were 2 (range 0–4) and 2 (range 0–4), respectively. The median mCADESI scores before and after tepoxalin were 23 (range 0–68) and 16 (range 0–72), respectively, and before and after placebo were 18 (range 3–79) and 24 (range 0–65), respectively. At the dose used in this study (10.0–19.1 mg kg−1 ), tepoxalin was well-tolerated and no adverse effects were noted. 相似文献
972.
MARCY J. SOUZA JONATHAN S. WALL ALAN STUCKEY GREGORY B. DANIEL 《Veterinary radiology & ultrasound》2011,52(3):340-344
Positron emission tomography (PET) is often used to stage and monitor human cancer and has recently been used in a similar fashion in veterinary medicine. The most commonly used radiopharmaceutical is 2‐Deoxy‐2‐[18F]‐Fluoro‐d ‐glucose (18F‐FDG), which is concentrated and trapped within cells that use glucose as their energy substrate. We characterized the normal distribution of 18F‐FDG in 10 healthy Hispaniolan Amazon parrots (Amazona ventralis) by performing whole body PET scans at steady state, 60 min after injection. Significant variability was found in the intestinal activity. Avian species are known to reflux fluid and electrolytes from their cloaca into their colon. To evaluate reflux as the cause of variability in intestinal distribution of 18F‐FDG, dynamic PET scans were performed on the coelomic cavity of six Hispaniolan Amazon parrots from time 0 to 60 min postinjection of radiotracer. Reflux of radioactive material from the cloaca into the colon occurred in all birds to varying degrees and occurred before 60 min. To evaluate the intestinal tract of clinical avian patients, dynamic scans must be performed starting immediately after injection so that increased radioactivity due to metabolism or hypermetabolic lesions such as cancer can be differentiated from increased radioactivity due to reflux of fluid from the cloaca. 相似文献
973.
C. Ragle C. Baetge S. Yiannikouris C. Dunigan R. Schneider R. Keegan 《Equine Veterinary Education》2011,23(12):630-635
Post anaesthetic myelopathy is a rare but devastating complication of equine anaesthesia and there is a need for better understanding of the condition and to raise veterinary awareness. The aim of this study was to collect data on unreported cases and combine those with reported cases to better identify possible risk factors and early clinical signs and outcomes of horses developing post anaesthetic myelopathy (PAM). A survey was conducted to identify cases of equine PAM. Records were also requested via the American College of Veterinary Anaesthesiologists listserve. Additional cases of PAM were located through review of the literature. Eighteen new cases and 12 published cases were identified. Large‐framed breeds between 6–24 months of age were more commonly affected (23/30). The majority of horses were positioned in dorsal recumbency during anaesthesia. Lack of movement and deep pain of the rear limbs, loss of anal tone and lack of panniculus response from the mid to caudal thorax distally were the most common clinical findings. Reported treatments resulted in no improvement of clinical signs and all horses died or were subjected to euthanasia from a few hours to 8 days post operatively. Poliomyelomalacia of the caudal spinal cord is the most common histopathological finding. Although a rare complication it is a catastrophic risk that can be eliminated by performing a standing operation. Hopefully in the future better understanding of this condition will lead to prevention and treatment strategies. 相似文献
974.
975.
976.
N K Puri K J Gogolin-Ewens M R Brandon 《Veterinary immunology and immunopathology》1987,15(1-2):59-86
The availability of a panel of monoclonal antibodies to sheep MHC class I and class II gene products has allowed for the first time an assessment of the relative complexity of the sheep MHC. By using four monoclonal antibodies to MHC class I, and seven monoclonal antibodies to MHC class II molecules together with one-dimensional SDS-PAGE, sequential immunoprecipitation and 2-dimensional gel analysis, three class I gene products and four distinct subsets of class II molecules have been identified. Sheep class I molecules showed heterogeneity on 2-dimensional gels and as in mouse and man, represented the products of at least three different non-allelic class I genes. Interestingly, the sheep beta 2 microglobulin molecule also displayed heterogeneity, consistent with either two primary gene products or allelic variation. Four sheep class II monoclonal antibodies identified distinct, non-overlapping subsets of sheep class II molecules of Mr 32-36 K (alpha chain) and 25-28 K (beta chain). These class II molecules were co-expressed on sheep B lymphocytes and represented the primary products of different sheep MHC class II genes. The class II molecules within three of these subsets displayed allelic polymorphism essentially restricted to their beta polypeptides, while the fourth subset of class II molecules showed allelic variation in both their alpha and beta polypeptides. The results of this study represent the first evidence for gene duplication and heterogeneity within the sheep MHC. The identification of three primary class I gene products and four distinct subsets of class II molecules suggests three class I loci and up to four distinct class II subregions within the sheep MHC. Potentially large numbers of allelic variants of these different gene products may be expressed in normal sheep. 相似文献
977.
Energy metabolism in canine erythrocytes associated with inherited high Na+- and K+-stimulated adenosine triphosphatase [(Na,K)-ATPase] activity (HK cells) was compared with that in normal canine erythrocytes (LK cells). Activities of some of the glycolytic enzymes in the HK cells were significantly higher than those in LK cells. The concentrations of adenosine triphosphate (ATP) and glycolytic intermediates in HK cells were almost equal to those in LK cells. Glucose utilization and lactate production by HK cells in vitro and incorporation of [32P]orthophosphate or [14C]glucose into 2,3-diphosphoglycerate in HK cells were higher than in LK cells. Radioactivity of [32P]ATP in HK cells was lower than in LK cells, but increased to approximately that of LK cells when (Na,K)-ATPase of HK cells was completely blocked by ouabain. When HK cells and LK cells were incubated in the absence of glucose, the concentration of ATP in HK cells was decreased more than that of LK cells. Although ouabain reduced the rate of decrease in ATP in HK cells, the decrease in ATP in HK cells was still 2-fold that in LK cells. The half-life of HK cells was about one-half that of LK cells. The results indicated that glycolysis is greater in HK cells than in LK cells, and that the increased glycolysis in HK cells was stimulated by an increased rate of ATP breakdown for active cation transport by the (Na,K)-ATPase and by increased degradation of ATP for some other pathway, eg, glutathione synthesis. Thus, the increased demand for ATP in HK cells might result in shortening the lifespan of HK erythrocytes. 相似文献
978.
Gastric cannulas were placed surgically in 5 young male horses. After a 2-week recovery period, horses were studied once a week. Horses were fasted for 24 hours, and gastric fluid output was collected for 5 continuous hours. Volumes were recorded every 15 minutes, and pH and hydrogen ion concentration were determined in an aliquot from each period. In 10 basal experiments, using 5 horses, volume, pH, and hydrogen ion concentration were continuously variable. Mean acid output was 45.1 +/- 2.02 microEq/15 min/kg (mean +/- SEM). In 6 experiments, using 3 horses, 0.5 mg of ranitidine/kg of body weight, given as an IV bolus after a 1-hour basal collection, significantly (P less than 0.02) inhibited hourly total acid output for 4 hours, but did not significantly change pH. The cannulation technique was done without complications, and horses tolerated the cannula for several months. Seemingly, the horse has a continuously variable gastric acid secretion, and histamine type-2 receptors have a role in this process. 相似文献
979.
Bacterial meningitis and diseases caused by bacterial toxins 总被引:1,自引:0,他引:1
Bacterial meningitis most commonly occurs in young calves secondary to septicemia. Clinical signs of hyperirritability are usually seen. Meningitis can be confirmed by cerebrospinal fluid analysis and culture or by necropsy. Intoxications by the exotoxins of Clostridium perfringens types C and D, C. botulinum, and C. tetani are difficult to confirm. The clinical signs of these intoxications vary from flaccid paralysis (botulism) to muscular rigidity (tetanus). Treatment of affected cattle has been unrewarding in botulism and enterotoxemia, whereas early aggressive treatment of tetanus cases can often be successfully resolved. Botulism and enterotoxemia can be proved using mouse inoculation tests, whereas tetanus is diagnosed largely by ruling out other diseases. 相似文献
980.
M I Banton S S Nicholson P L Jowett M B Brantley C L Boudreaux 《Journal of the American Veterinary Medical Association》1987,191(7):827-828
Cattle from 2 herds developed copper toxicosis after the ingestion of chicken litter. The affected animals were adult Holstein cows and crossbred steers that ate 9 to 16 kg of litter/day. These cattle developed a sudden onset of weakness, depression, anorexia, icteric mucous membranes, and dark reddish brown urine. Liver copper concentrations in 2 cattle (1 from each herd) were 436 and 730 ppm. Results of copper analyses of chicken litter ranged from 620 to 920 ppm. Sodium molybdate and sodium thiosulfate were added to the ration of the dairy herd. Two cows with clinical signs of copper toxicosis recovered after being given additional sodium molybdate and thiosulfate supplements, orally. 相似文献