全文获取类型
收费全文 | 129697篇 |
免费 | 6289篇 |
国内免费 | 90篇 |
专业分类
林业 | 6393篇 |
农学 | 3736篇 |
基础科学 | 750篇 |
13804篇 | |
综合类 | 27724篇 |
农作物 | 5061篇 |
水产渔业 | 5407篇 |
畜牧兽医 | 64096篇 |
园艺 | 1534篇 |
植物保护 | 7571篇 |
出版年
2018年 | 1399篇 |
2017年 | 1474篇 |
2016年 | 1373篇 |
2015年 | 1243篇 |
2014年 | 1484篇 |
2013年 | 4347篇 |
2012年 | 2840篇 |
2011年 | 3486篇 |
2010年 | 2223篇 |
2009年 | 2103篇 |
2008年 | 3385篇 |
2007年 | 3418篇 |
2006年 | 3213篇 |
2005年 | 3126篇 |
2004年 | 2964篇 |
2003年 | 3077篇 |
2002年 | 2905篇 |
2001年 | 3425篇 |
2000年 | 3386篇 |
1999年 | 2818篇 |
1997年 | 1150篇 |
1995年 | 1327篇 |
1993年 | 1152篇 |
1992年 | 2528篇 |
1991年 | 2655篇 |
1990年 | 2783篇 |
1989年 | 2807篇 |
1988年 | 2640篇 |
1987年 | 2554篇 |
1986年 | 2613篇 |
1985年 | 2625篇 |
1984年 | 2171篇 |
1983年 | 1941篇 |
1982年 | 1357篇 |
1981年 | 1289篇 |
1980年 | 1212篇 |
1979年 | 2144篇 |
1978年 | 1730篇 |
1977年 | 1539篇 |
1976年 | 1435篇 |
1975年 | 1610篇 |
1974年 | 2086篇 |
1973年 | 2089篇 |
1972年 | 2127篇 |
1971年 | 2048篇 |
1970年 | 1910篇 |
1969年 | 1678篇 |
1968年 | 1437篇 |
1967年 | 1580篇 |
1966年 | 1404篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
151.
The study describes plumage modifications and specific feather malformations, as related to the domestication process of different poultry species. The modifications include naked necks, leg feathering, frizzle feathering, silky feathering, fat quills, and feather abnormalities caused by behavioural hypertrophies. Most of these plumage modifications correspond to the breed standard for exhibition poultry fancy. However, they impair the normal function of these animals. The negative influences comprise disorders in social behaviour, loss of typical plumage functions and disabilities of normal mobility, as well as genetic defects and pathogenic predispositions. 相似文献
152.
H A Waters 《Journal of the American Veterinary Medical Association》1992,201(11):1689-1690
153.
154.
Plasma triglyceride concentration during intravenous infusions of propofol and Intralipid in sheep 总被引:1,自引:0,他引:1
B. M. Q. Weaver D. Raptopoulos † G. E. Staddon W. W. Mapleson‡ 《Veterinary anaesthesia and analgesia》1996,23(1):15-19
Plasma triglyceride concentrations were measured in sheep given Intralipid or propofol, which is carried in a vehicle very similar to 10% Intralipid. A bolus dose was administered followed immediately by an infusion of the same agent for 2 h. In the animals that received propofol, the measured concentration increased by a mean amount of 3.39 mmol/l when the infusion rate was l ml/min (Group Pl) and by 7.13 mmol/l when it was 2 ml/min (Group P2). When 10% Intralipid was administered and infused at 1 ml/min (Group I10), the measured concentration increased only by 0.95 mmol/l. One hour after stopping the infusion, the excess of measured concentration over baseline had decreased in the Pl and I 10 groups to 0.52 and 0.13, respectively, of the corresponding maximum excess. The method adopted for measuring plasma triglycerides is widely used in hospitals; however, an incidental observation revealed that it is inappropriate in the presence of injections of propofol or Intralipid. Despite this, evidence and argument are presented to support the conclusion that, with propofol, plasma triglyceride concentrations increased more rapidly during the infusions and returned to baseline more slowly than with a corresponding amount of Intralipid. 相似文献
155.
Studies on efficacy and stability of a vaccine bait containing ERA strain of rabies virus propagated in a BHK-21 cell line.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
K F Lawson H Chiu M Matson P Bachmann J B Campbell 《Canadian journal of veterinary research》1992,56(2):135-141
In a dose response study in foxes, the median protective dose of ERA BHK21 vaccine in a blister pack bait was 10(6.0) tissue culture infective doses (TCID)/mL, while artificially aged baits with titers of 10(6.3) TCID/mL induced seroconversion in 78% of foxes. There was no significant difference in the development of antibodies in foxes receiving 1, 2 or 3 mL volumes of vaccine in the bait. When baits were exposed to the elements and fed to foxes over a 21 day period, 85% of the animals seroconverted. Age, sex and the way in which the vaccine container was contacted did not appear to be factors in the responses of these animals. Juvenile foxes, approximately six months of age, were marked more readily with the tetracycline bait marker than older animals. Approximately 25% of foxes did not appear to respond well to vaccination and the titer of the vaccine was a critical factor in producing seroconversion in these animals. 相似文献
156.
Root development of sugar beet plants on a sandy loess site with regard to nitrogen nutrition.
Root development of sugar beet plants in a sandy loess soil (Haplic Phaeozem) was observed from the early seedling stage up to harvest by measuring at first the greatest vertical and lateral extension of the root systems of single plants and later the rooting density of the whole plant stands (auger method, profile wall method).
During the seedling stage not only the subsoil, but also large parts of the topsoil between the plants remained unoccupied by the root systems. In this phase the greatest lateral extension of single roots reaches nearly the length of the greatest leaf of the plant. With the closure of the canopy the rooting density in the topsoil accounts to 1–2 cm cm−3 .
In summer roots penetrate to a depth of 100–150 cm with rooting densities of 0.1 to 1 cm - cm−3 . Thus, the plants gain not only access to water reserves, but sometimes meet remarkable amounts of nitrate which under the relatively dry conditions of the region tends to accumulate in 60–120 cm depth and – when taken up by the beet plants in the late stage of growth – affects crop quality negatively. 相似文献
Root development of sugar beet plants in a sandy loess soil (Haplic Phaeozem) was observed from the early seedling stage up to harvest by measuring at first the greatest vertical and lateral extension of the root systems of single plants and later the rooting density of the whole plant stands (auger method, profile wall method).
During the seedling stage not only the subsoil, but also large parts of the topsoil between the plants remained unoccupied by the root systems. In this phase the greatest lateral extension of single roots reaches nearly the length of the greatest leaf of the plant. With the closure of the canopy the rooting density in the topsoil accounts to 1–2 cm cm
In summer roots penetrate to a depth of 100–150 cm with rooting densities of 0.1 to 1 cm - cm
157.
158.
D C Lay T H Friend R D Randel C L Bowers K K Grissom O C Jenkins 《Journal of animal science》1992,70(2):330-336
Twenty-seven crossbred calves (1/2 Simmental, 1/4 Hereford, 1/4 Brahman) averaging 257 +/- 11 d of age were either hot-iron-branded (H), freeze-branded (F), or sham-branded (S). Calves were blocked for temperament, weight, and sex and were randomly assigned to day and order in which treatments were applied. To reduce stress from handling at treatment time, each calf was herded through the squeeze chute daily for 5 d before the experiment. Jugular cannulas were inserted in each calf 1 d before application of treatment. Blood samples and heart rate measures were obtained at -5, -3, 0, .5, 1, 3, 5, 10, 15, and 20 min after application of the treatments. Mean concentrations of plasma epinephrine (EPI) were higher for H calves at time .5 min than for either S or F calves (P = .10). To account for individual differences, prebranding heart rates and hormone concentrations were subtracted from subsequent samples and were also used to calculate a proportion for each subsequent sample. Analyses of subtracted values found that EPI concentrations were greater for H calves than for either S or F calves (P = .007) at .5 min postbranding. No other differences were found for the subtracted analyses. Analyses of proportion data also revealed that H calves had greater EPI than did either S or F calves (P = .027) at .5 min postbranding. Only three animals vocalized during branding, one H calf and two F calves. Despite the 5-d acclimation period, handling and restraint elevated plasma cortisol concentrations and heart rate.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
159.
125I-labelling was used to characterise the surface components of five stocks of Trypanosoma evansi. Two components of 67 and 60.5 kD were labelled in two of the stocks, a single 60.5 kD component in two other stocks and no components in the remaining stock. These differences are probably related to the labelling method and biochemical differences between the stocks. 相似文献
160.
High-resolution computed tomography (HRCT) was performed in 21 isolated animal lungs, from 4 mammalian species (pigs, rabbits, dogs, sheep). Gross and subgross central and peripheral lung morphology was determined by HRCT. Three distinct types of lungs can be identified, principally based on the extent of interlobular septal development; the relationship of major vessels to airways; and the thickness of the visceral pleura. Type-I lung is found in pigs, sheep, and cattle; type-II lung is found in rabbits, dogs, cats, and monkeys; and type-III lung is found in human beings and horses. These mammalian lungs were compared with human lungs. The potential use of HRCT to investigate specific human lung diseases in the aforementioned species also was considered. 相似文献