全文获取类型
收费全文 | 16570篇 |
免费 | 8篇 |
专业分类
林业 | 3645篇 |
农学 | 1300篇 |
基础科学 | 146篇 |
2769篇 | |
综合类 | 724篇 |
农作物 | 2099篇 |
水产渔业 | 1790篇 |
畜牧兽医 | 1105篇 |
园艺 | 1116篇 |
植物保护 | 1884篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 2744篇 |
2017年 | 2708篇 |
2016年 | 1183篇 |
2015年 | 67篇 |
2014年 | 25篇 |
2013年 | 15篇 |
2012年 | 807篇 |
2011年 | 2142篇 |
2010年 | 2111篇 |
2009年 | 1259篇 |
2008年 | 1324篇 |
2007年 | 1589篇 |
2006年 | 43篇 |
2005年 | 104篇 |
2004年 | 106篇 |
2003年 | 159篇 |
2002年 | 63篇 |
2001年 | 6篇 |
2000年 | 40篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 1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 0 毫秒
101.
102.
Concepta McManus Helder Louvandini Rosilene Gugel Luiz Cláudio Bastos Sasaki Eliandra Bianchini Francisco Ernesto Moreno Bernal Samuel Rezende Paiva Tiago Prado Paim 《Tropical animal health and production》2011,43(1):121-126
The objective of this study was to evaluate and compare physical parameters in groups of sheep with different phenotypic characteristics
in the Centre-west region of Brazil. Five groups of sheep, with nine animals per group, were selected, three groups of Santa
Inês animals with different coat colours (white, brown and black), one group with crossbred animals (Santa Inês × Bergamasca)
and one group with animals of the Bergamasca breed. The following traits were evaluated: coat thickness, number and length
of hair, pigmentation level in the coat and the skin as well as the percentage area of sweats glands in the skin tissue, carried
out by histological analysis. The number of hairs and the area of sweats glands were not significantly different between the
evaluated groups. The Bergamasca breed showed low pigmentation of the skin and long hairs. The levels of pigmentation of the
hair and of the skin were highly correlated. Between the Santa Inês groups, the group with white hair showed the better parameters
for heat adaptation, while the brown hair group showed the lower heat adaptation when compared with another hair breed groups. 相似文献
103.
The aim of this study was to determine the fattening performance and the slaughter and carcass characteristics of Akkeçi (Saanen × Kilis (B1) crossbred) male kids raised in individual crates (IC) or in group pen housing (GP). In both GP and IC groups, total 13 heads of male kids, whose initial body weights were 21.43 ± 1.03 kg and 20.61 ± 0.98 kg, respectively, evaluated for their fattening performances. After 56 days of the fattening period, the final body weights and average daily weight gains of the GP and IC kids were recorded as 30.84 ± 0.82 kg and 25.84 ± 0.76 kg; 182.42 ± 14.77 g and 92.09 ± 13.76 g, respectively (P < 0.001). Adrenal gland weights of the GP and IC groups were similar as 1.66 ± 0.25 g and 1.77 ± 0.22 g, respectively. Although, the carcass conformation of kids was similar between groups, there were significant differences between GP and IC groups for some slaughter and carcass characteristics. In general, although housing kids reared in individual crates provides opportunity to individually feed and monitor a kid, the results obtained from the individual crates in the present study were not satisfactorily from the ethological and production points of view. 相似文献
104.
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
105.
Felicitat Todolí Laia Solano-Gallego Ana Ojeda Josefina Quintana Albert Lloret Xavier Roura Jordi Alberola Alhelí Rodríguez-Cortés 《Veterinary parasitology》2009
Recently, anti-Leishmania IgG has been detected in urine samples from Leishmania-infected dogs and its concentrations have been correlated with impairment of renal function. The presence and relationship with other anti-Leishmania Ig isotypes in urine have not yet been investigated. The current study analyzed the concentrations of anti-Leishmania IgA and IgG in sera (Ig-S) and urine (Ig-U) samples by ELISA in 64 untreated dogs with clinical leishmaniasis. All 64 serum samples tested were positive for anti-Leishmania IgG. Fifty of them (78.1%) were also positive for anti-Leishmania IgA. The results showed the presence of anti-Leishmania IgA-U in 38% of the 50 dogs that were positive for specific IgA-S. Thirty-eight of the 64 dogs positive for Leishmania-specific IgG-S (59.4%) were also positive for Leishmania-specific IgG in urine (IgG-U). The concentrations of anti-Leishmania IgA-U were significantly correlated with urine protein/creatinine (uP/C) ratio (ρ = 0.542; P < 0.001) and with serum biochemical parameters, such as γ-globulins, urea and creatinine. Goldmann–Witmer coefficient (C value) indicated that detection of specific IgA in urine samples from dogs with leishmaniasis might not only be due to impairment of filtration of the glomerular barrier but also be due to local production of this isotype, which might reflect a local immunological response to the presence of the parasite in the genitourinary tract. Anti-Leishmania IgG-U concentrations were highly correlated with uP/C ratio (ρ = 0.779; P < 0.001) and C value did not support in any case local production of this isotype. IgG isotype might be a more suitable and specific tool to evaluate renal damage due to the lower IgA-U sensitivity and correlation coefficients and evidence of IgA local production. However, dogs found positive for both Ig isotypes in urine presented significantly higher specific IgG-U concentrations and higher uP/C ratios than dogs found positive only for IgG-U, thus suggesting that the first group suffered more severe renal damage. This fact makes it necessary to evaluate the prognosis of dogs showing both anti-Leishmania IgA-U and IgG-U in future studies. 相似文献
106.
Haunshi S Shanmugam M Padhi MK Niranjan M Rajkumar U Reddy MR Panda AK 《Tropical animal health and production》2012,44(5):969-973
The present study was conducted to evaluate two Indian native chicken breeds, namely, Aseel and Kadaknath for fertility, hatchability,
genetic parameters of juvenile growth traits, and semen quality traits at the onset of sexual maturity. The fertility was
similar in Aseel (86.96%) and Kadaknath (85.15%); however, a relatively higher hatchability was observed in Kadaknath (77.94%)
than Aseel (70.74%). Heritability estimates of body weights at 4 weeks of age were almost similar in Aseel (0.37) and Kadaknath
(0.39), while the estimate of body weight at 6 weeks of age was higher in Aseel (0.42) than Kadaknath (0.31). The heritability
estimate of shank length at 6 weeks of age was lower in Aseel (0.16) compared to Kadaknath (0.35). The age at first egg in
the flock was comparable in Aseel (148 days) and Kadaknath (150 days). Aseel breed with significantly (P ≤ 0.001) higher body weight, absolute and relative testes weights had significantly higher semen volume (P ≤ 0.05) and sperm motility (P ≤ 0.01) but had lower seminal plasma cholesterol level (P ≤ 0.05) as compared to Kadaknath. It can be concluded that there is a scope for genetic improvement of these two native breeds
for juvenile growth traits since heritability estimates of these traits were relatively high. 相似文献
107.
Segura-Correa JC Ek-Mex EJ Alzina-López A Magaña-Monforte JG Sarmiento-Franco L Santos-Ricalde RH 《Tropical animal health and production》2011,43(6):1191-1194
The objective of this study was to determine the effect of some factors on the length of productive life (LPL), the number
of parities (NP), and the culling interval (CI) of sows. The information from 2003 to 2009 of 3,746 sows with LPL and NP records
and 5,819 sows with CI records from the four farms of Yucatan, Mexico was used. LPL was defined as the number of days between
the first farrowing and culling or death and CI as the number of days between the last farrowing and culling. To determine
the effects of farm, litter size at first farrowing (LSF1) and age at first farrowing (AF1) on LPL and NP, and of farm, LSF1
and culling reason on CI general linear models were used. Means and standard errors for LPL, NP, and CI were 496.4 ± 8.42 days,
3.35 ± 0.04 parities, and 48.3 ± 0.52 days, respectively. All factors had significant effects (P < 0.05) on LPL, NP, and CI. The sows from farm 2 stayed longer (806.0 days) and had more parities (5.25) than the sows from
the other farms. Sows with the smallest litters (≤8 piglets) at first farrowing stayed the least time in the farm (675.1 days)
and had the fewest parities (4.49). Gilts farrowing the first time before 331 days of age stayed longer time in the farm (726.4 days)
and had more parities (4.81) in comparison with 331–348 and more than 348 days age groups. With respect to CI, the sows in
farm 3 stayed the longest time in the farm. Sows with more than five parities were culled sooner after their last farrowing.
In conclusion, differences between farms for LPL, PN, and CI were found. Females that farrowed at a short age and those with
large litters stayed longer in the herd. Old sows and those culled for reproductive reasons stayed the least time in the herd
after their last farrowing. 相似文献
108.
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
109.
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
110.
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