全文获取类型
收费全文 | 16391篇 |
免费 | 1篇 |
专业分类
林业 | 3621篇 |
农学 | 1293篇 |
基础科学 | 137篇 |
2732篇 | |
综合类 | 709篇 |
农作物 | 2096篇 |
水产渔业 | 1779篇 |
畜牧兽医 | 1053篇 |
园艺 | 1110篇 |
植物保护 | 1862篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2019年 | 1篇 |
2018年 | 2744篇 |
2017年 | 2703篇 |
2016年 | 1179篇 |
2015年 | 63篇 |
2014年 | 14篇 |
2013年 | 6篇 |
2012年 | 789篇 |
2011年 | 2124篇 |
2010年 | 2101篇 |
2009年 | 1252篇 |
2008年 | 1311篇 |
2007年 | 1574篇 |
2006年 | 28篇 |
2005年 | 96篇 |
2004年 | 100篇 |
2003年 | 151篇 |
2002年 | 58篇 |
2001年 | 4篇 |
2000年 | 41篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 1篇 |
1977年 | 4篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
In this study, natural cycling of BoHV-1 infection was investigated in two groups of dairy cattle containing 2120 head. Group
1 comprised 127 animals and they were monitored for BoHV-1 infection virologically and serologically in six consecutive sampling
periods. It consisted of naive heifers between 6 and 8 months of age, while in group 2, age, sex and the BoHV-1 serostatus
of the animals were disregarded. The animals in group 1 were found to have seroconverted at the second sampling. Results of
the serological study showed slight antibody response after natural BoHV-1 infection in the herd and neutralizing titres fell
below protective levels in the 6–8 months after the peak. During the 2-year study period, one recurrence was detected after
primary infection. Virus isolation studies revealed a cytopathic effect indicative of BoHV-1 in two nasal swabs taken during
the fifth sampling period from animals with mild upper respiratory tract symptoms. As the study was carried out under natural
conditions, it is not known whether the viruses isolated were from recurrences or re-infections. Data from cross-neutralization
tests with herd isolates showed higher antibody response than those with the reference virus. The dynamics of BoHV-1 in both
groups were found to be statistically similar. 相似文献
102.
J. A. Mortenson E. H. Haq Khan I. Ali S. Manzoor A. Jamil M. Abubakar M. Afzal M. Hussain 《Tropical animal health and production》2017,49(4):691-695
In northern Pakistan, many farming communities rely on domestic yak (Bos grunniens) as a principle source of income. A 2006 participatory disease surveillance report from this region indicated that foot-and-mouth disease (FMD) is the most prevalent annual disease of yak. Our objectives of this study were to determine exposure levels of yak to FMD virus; implement a vaccination program based on current, regional FMD virus serotypes and subtypes; and quantify immune responses following vaccination. Blood samples were used to determine pre-vaccination exposure of animals to FMD virus by antibody presence to non-structural proteins of FMD virus using a 3-ABC trapping indirect ELISA. Vaccine used consisted of FMD serotypes ‘O’ (PanAsia-2), ‘A’ (Iran-05), and ‘Asia-1’ (Shamir), but changed later during the study to match newly circulating viruses in the country (‘O’-PanAsia-2; ‘A’-Turk-06 and Asia-1-Sindh-08). Three hundred sixty-three blood samples were tested from selected villages to determine pre-vaccination FMD virus exposure in yak with an average of 37.7%. Immune responses from initial vaccination and booster dose 30 days later showed clear protective levels (as mean percent inhibition) of antibodies against structural proteins of serotypes ‘O,’ ‘A,’ and ‘Asia-1.’ These responses remained above threshold positive level even at day 210 following initial vaccination. Results of sero-surveillance and anecdotal information of repeated FMD outbreaks demonstrate the persistence of FMD virus of yak in northern Pakistan. Laboratory results and field observations clearly indicated that yak can be protected against FMD with a good quality vaccine with FMD serotype(s) matching current, regionally circulating FMD virus. 相似文献
103.
Raj Sukhbir Singh B. K. Bansal D. K. Gupta 《Tropical animal health and production》2017,49(8):1623-1629
The present study was aimed to investigate the relationship between selected morphological traits of teat and subclinical mastitis (SCM) in Frieswal crossbred dairy cows. A total of 1040 quarters from 261 lactating cows were evaluated for teat shape (bottle/fleshy/collapsed/conical/normal/pencil and short), teat-end shape (dished/flat/funnel/pocketed/pointed and rounded), teat orientation (aligned/misaligned) and teat position (front and rear; left-sided and right-sided). Each udder quarter was screened with California Mastitis Test (CMT) for the purpose of defining quarter health status. Data were analysed using Chi-square test and multivariable logistic regression procedure. An overall prevalence of SCM (CMT positive) at quarter level was 30.6%. Most of the teats had normal or cylindrical shapes (48%), dished teat-ends (40.7%), and aligned (central or squared) in orientation (65%). At bivariable level, significant association of SCM with teat shape, teat position, teat orientation, parity, and stage of lactation was observed (P < 0.05 to P < 0.001). Teat-end shapes showed some association with SCM (P = 0.07). Results of multivariable analysis showed that pencil-shaped teats were least associated with SCM (P < 0.05) as compared to other teat shapes. Prevalence of SCM was also higher in rear teats (P = 0.015), misaligned teats (P = 0.01), and cows in second or higher parities (P < 0.01) and late stage of lactation (P < 0.001). The results of the present study indicate that selected morphological traits of teat are associated with SCM in Frieswal crossbred cows; therefore, selection towards desirable morphological traits could help reduce mastitis in this breed. 相似文献
104.
Fariba Ahmadi Morteza Zendehdel Vahab Babapour Negar Panahi Shahin Hassanpour Mina Khodadadi 《Veterinary research communications》2017,41(4):241-248
Melanocortin 3 and 4 receptors (MC3R and MC4R) are known as the main receptors for melanocortin-induced hypophagia in mammalian and poultry. Also, central glutamatergic system has mediatory role on function of the melanocortin system in some brain areas. So, the aim of the current study was to determine the role of MC3/MC4 receptors agonist on food intake and its interaction with glutamatergic in 3-h food-deprived (FD3) neonatal broilers. In experiment 1, chickens were intracerebroventricular (ICV) injected with control solution, MTII (MC3/MC4 receptors agonist; 2.45, 4.8 and 9.8 pmol). In experiment 2, control solution, SHU9119 (MC3/MC4 receptors antagonist; 0.5, 1 and 2 nmol) were ICV injected. In experiment 3, birds ICV injected with control solution, SHU9119 (0.5 nmol), MTII (9.8 pmol) and co-injection of the SHU9119 + MTII. Experiments 4–8 were similar to experiment 3, except birds injected with MK-801 (NMDA glutamate receptors antagonist, 15 nmol), CNQX (AMPA glutamate receptors antagonist; 390 nmol), AIDA (mGLUR1 glutamate receptors antagonist; 2 nmol), LY341495 (mGLUR2 glutamate receptors antagonist; 150 nmol) and UBP1112 (mGLUR3 glutamate receptors antagonist; 2 nmol) instead of SHU9119. Then, cumulative food intake was recorded until 120 min after injection. According to the results, dose dependent hypophagia observed after ICV injection of the MTII (p < 0.05). ICV injection of SHU9119 significantly increased food intake in birds (p < 0.05). Co-injection of SHU9119 + MTII significantly inhibited MTII- induced hypophagia in neonatal chicks (p < 0.05). In addition, hypophagia- induced by MTII was significantly attenuated with co-injection of MTII + MK-801(p < 0.05). These results suggested MC3 and MC4 receptors have inhibitory role on food intake and this effect is probably mediated by NMDA glutamate receptors in neonatal chickens. 相似文献
105.
Yongju Zhao Jiahua Zhang Hong Wei Xinming Sun Biao Mu Mingju Yu Lingbing Wang 《Tropical animal health and production》2010,42(6):1257-1262
Two experiments were undertaken to select the efficient method applied for goat estrous synchronization. In experiment 1, a total of 120 does (Capra hircus) were divided into five groups with a randomized block design, and the does of treatment 1 were synchronized by intravaginal sponges impregnated with 30 mg Levonorgestrel inserted for 10 days. Does of treatments 2, 3, and 4 were treated with further injection of 25 IU follicle-stimulating hormone (FSH), 0.05 mg prostaglandin F2 alpha (PGF2α), and 25 IU FSH + 0.05 mg PGF2α at sponge withdrawal, respectively. The does in the control group (n = 40) without estrous synchronization treatment and natural estrous does were observed. In experiment 2, a total of 140 does in five goat farms in breeding and non-breeding seasons were treated with the selective efficient procedure. The results presented that all the employed treatments were capable of inducing and synchronizing estrous goats. According to estrous response and economy, the use of intravaginal sponges impregnated with 30 mg Levonorgestrel and 0.05 mg PGF2α (treatment 3) is the first choice for estrous synchronization, and 95.0% of synchronized does demonstrated estrus, which was significantly higher than that of treatment 1 (P < 0.05) and control group (P < 0.01). The percentages of ovulating of treatments 3 and 4 were the same (95.0%), which were significantly higher than that of treatment 1 (P < 0.01). The ovulation rates among different groups were not significant (P > 0.05). When the selective procedure was applied to five goat farms, 85.7% (120/140) of does demonstrated estrus, and the kidding percentage, litter size, and prolificacy rate were 53.6%, 0.95, and 177%, respectively. 相似文献
106.
Ross G. Cooper Jaroslaw O. Horbańczuk Raul Villegas-Vizcaíno Salwa Kennou Sebei Aisha E. Faki Mohammed Khalid M. A. Mahrose 《Tropical animal health and production》2010,42(3):363-373
This work discusses some of the important considerations of wild ostrich evolution, behaviour and ecology, as items included
in ostrich production. In the process considerable research was conducted by collating information from peer-reviewed papers;
textbooks; manuals; and PubMed and Agricola searches. Selected areas reviewed included activity of ostriches; feeding and
water needs; sexual maturity; egg laying and natural incubation; selected physiological parameters; and predation. There is
an immediate and urgent need to conserve and protect the rapidly declining populations of wild ostriches with the committed
involvement of governments and funding bodies. 相似文献
107.
Purushottam Kaushik Dhirendra K. Singh S. Vinoth Kumar Ashok K. Tiwari Gunjan Shukla Shanker Dayal Pallav Chaudhuri 《Veterinary research communications》2010,34(2):119-132
Brucella abortus, a gram negative, facultative intracellular pathogen causes brucellosis in many animal species and humans. Although live,
attenuated vaccines are available against this infection, they suffer from certain limitations. Therefore, the development
of an effective subunit vaccine against brucellosis is an area of intense research. The outer membrane proteins (OMPs) of
Brucella species have been extensively studied for its immunogenicity and protective ability. We have investigated the potential of
CpG ODN to enhance the immunogenicity and protective efficacy of recombinant 28 kDa outer membrane protein (rOMP28) of Brucella melitensis. The study demonstrated vigorous immunoglobulin G (IgG) response of OMP28. The administration of rOMP28 with CpG caused increased
cell mediated immune response in terms of induced IgG2a, T-cell proliferation and up-regulation of type I cytokine expression.
In contrast, the free antigen suppressed the interferon gamma (type I cytokine) production on in-vitro stimulation of spleenocytes.
The result indicates the role of OMP28 in the down regulation of IFN-γ production. Moreover, the B. abortus S-19 vaccinated mice showed highest production of IL-4 and IFN-γ. The protective ability of the antigen was evaluated by
systemic bacterial clearance after challenging the mouse with B. abortus 544 pathogen. The level of protection was significant in rOMP28+CpG treated mice but was lower than the required level. The
results of the present study indicate that rOMP28 could be an immunogen capable of inducing both humoral and cellular immune
response. The humoral response was biased towards Th1 type when it was co-administered with CpG. 相似文献
108.
Luuk B. Schoonman T. Wilsmore Emmanuel S. Swai 《Tropical animal health and production》2010,42(4):579-587
In view of the worldwide importance of Toxoplasma gondii and the fragmented information on the seroprevalence of the disease in animals in Tanzania, a study, using the modified Eiken
latex agglutination test (LAT), was conducted from May 2003 to January 2004 to determine the prevalence of antibody to T. gondii in 130 randomly selected farms comprising 655 cattle. The overall seroprevalence of T.gondii antibodies in cattle and farms were 3.6% and 13%, respectively. Risk factors for animal and herd-level toxoplasmosis seropositivity
were tested using multivariable logistic regression to control for confounding factors. Cattle managed under traditional husbandry
practises were more likely to be seropositive than those managed under smallholder practises (48% versus 4.7%; p < 0.01). Herd size of ≥ 9 cattle were at greater risk of acquiring infection than herds holding fewer animals [≤ 9 cattle],
(odd ratio [OR] = 3.99; 95% confidence interval [CI], 0.97–16.48; P = 0.001). We concluded that seroprevalence at herd level was high and relatively low at animal level, possibly due to the
reduced susceptibility of cattle to T.gondii infection as compared to goats and sheep. The high seroprevalence in animals managed by traditional husbandry practise suggests
that the parasite is widely distributed in the environment and could pose a public health threat to the people living in those
areas. 相似文献
109.
A study was conducted to evaluate the macro and trace mineral contents of ten enset varieties collected from Sidama zone of
southern Ethiopia. Samples of leaf lamina, leaf midrib, pseudostem and corm were taken from ten enset varieties at the age
of 5 to 6 years during the main rainy season. The dry weight of each variety and fraction were also determined. Mineral contents
in fractions of different enset varieties were analysed and compared with nutrient requirements of ruminants. The contribution
of different enset fractions to the total dry weight was variable (P < 0.05), the highest being from pseudostem and the lowest
from leaf lamina. There were varietal differences (P < 0.05) in macro and trace mineral content in different fractions except
phosphorus (P) content of leaf lamina. Most enset fractions were rich sources of major minerals such as P, potassium (K),
calcium (Ca) (except corm) and magnesium (Mg). Sodium (Na) content was very low. Most fractions were rich in iron (Fe) and
manganese (Mn), but deficient in copper (Cu), except leaf lamina. Zinc (Zn) content was high in corm, but low in other fractions.
This account of the macro and trace mineral content of different enset varieties and fractions could help in strategic supplementation
intended to alleviate mineral deficiencies. 相似文献
110.
An ultrastructural study was performed on chloride cells of euryhaline R.r.Caspicus of south of Caspian Sea. The chloride
cells are distributed in the interlamellar region of filaments. They are oval to elongated form with an apical positioned
nucleus, expanded tubular system and heteromorphic mitochondria. These cells are surrounded by pavement cell and accessory
cell. A small and depressed surface formed by pavement cells is in contact with the aquatic milieu. There is also channel
system in accessory cells. One of the typical features was the important changes in microtubules and mitochondria of chloride
cells in some fishes. Swelling and rupture of cristae and degeneration of microtubules were from these changes. 相似文献