全文获取类型
收费全文 | 2069篇 |
免费 | 121篇 |
国内免费 | 10篇 |
专业分类
林业 | 159篇 |
农学 | 121篇 |
基础科学 | 39篇 |
471篇 | |
综合类 | 145篇 |
农作物 | 279篇 |
水产渔业 | 193篇 |
畜牧兽医 | 451篇 |
园艺 | 79篇 |
植物保护 | 263篇 |
出版年
2024年 | 3篇 |
2023年 | 20篇 |
2022年 | 69篇 |
2021年 | 86篇 |
2020年 | 98篇 |
2019年 | 126篇 |
2018年 | 145篇 |
2017年 | 131篇 |
2016年 | 138篇 |
2015年 | 74篇 |
2014年 | 92篇 |
2013年 | 218篇 |
2012年 | 116篇 |
2011年 | 134篇 |
2010年 | 107篇 |
2009年 | 71篇 |
2008年 | 121篇 |
2007年 | 57篇 |
2006年 | 46篇 |
2005年 | 38篇 |
2004年 | 33篇 |
2003年 | 32篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 27篇 |
1999年 | 17篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有2200条查询结果,搜索用时 15 毫秒
21.
Aye Nyein Chan Shutu Xu YaQin Shi YaNan Li Ali Farhan DongWei Guo JiQuan Xue 《Euphytica》2017,213(1):12
Association mapping was conducted to explore favorable alleles of the chlorophyll-related non-yellow coloring 1 (NYC1) gene under light and dark using an association panel of 146 maize inbred lines. A total of 14 polymorphic sites were identified to be significantly associated with at least one of the chlorophyll-related traits at the seedling stage. Four single nucleotide polymorphisms (SNPs) (S320, S2951, S3901, and S3355) from the NYC1 gene were respectively strongly associated with chlorophyll b (chlb), the ratio of chlorophyll a to chlorophyll b (chl_ratio), chlorophyll a degradation (chla_deg), and total chlorophyll degradation (total_chl_deg). SNPs S320 (C/A) in exon 1, and S2951 (A/G) in intron 8 was related to chlb, with 6.01 and 8.89% of phenotypic variation under light treatment, respectively. Under dark treatment, SNP S3901 (C/T), located in 3′ untranslated region (3′UTR), was associated with chl_ratio, explaining 7.01% of the observed phenotypic variation, whereas SNP S3355 (C/G) in intron 9 explained 6.48 and 5.18% of phenotypic variations in chla_deg and total_chl_deg, respectively. Taken together, these results indicated that the NYC1 gene plays an important role in chlorophyll content and other related traits, and different sites act on chlorophyll metabolism under different light intensities in maize seedlings. Furthermore, these findings improve our understanding of the genetic basis of chlorophyll metabolism under different light conditions. 相似文献
22.
Dennis N. Lozada R. Esten Mason Md Ali Babar Brett F. Carver Gina-Brown Guedira Keith Merrill Maria Nelly Arguello Andrea Acuna Lucas Vieira Amanda Holder Christopher Addison David E. Moon Randal G. Miller Susanne Dreisigacker 《Euphytica》2017,213(9):222
Genome-wide association studies (GWAS) are useful to facilitate crop improvement via enhanced knowledge of marker-trait associations (MTA). A GWAS for grain yield (GY), yield components, and agronomic traits was conducted using a diverse panel of 239 soft red winter wheat (Triticum aestivum) genotypes evaluated across two growing seasons and eight site-years. Analysis of variance showed significant environment, genotype, and genotype-by-environment effects for GY and yield components. Narrow sense heritability of GY (h 2 = 0.48) was moderate compared to other traits including plant height (h 2 = 0.81) and kernel weight (h 2 = 0.77). There were 112 significant MTA (p < 0.0005) detected for eight measured traits using compressed mixed linear models and 5715 single nucleotide polymorphism markers. MTA for GY and agronomic traits coincided with previously reported QTL for winter and spring wheat. Highly significant MTA for GY showed an overall negative allelic effect for the minor allele, indicating selection against these alleles by breeders. Markers associated with multiple traits observed on chromosomes 1A, 2D, 3B, and 4B with positive minor effects serve as potential targets for marker assisted breeding to select for improvement of GY and related traits. Following marker validation, these multi-trait loci have the potential to be utilized for MAS to improve GY and adaptation of soft red winter wheat. 相似文献
23.
AbstractIncreasing resources use efficiency in intensive cultivation systems of maize (Zea mays L.) can play an important role in increasing the production and sustainability of agricultural systems. The objectives of the present study were to evaluate DM yield and the efficiency of inputs uses under different levels of water, nitrogen (N) and phosphorus (P) in maize. Therefore, three levels of irrigation including 80 (ETc80), 100 (ETc100) and 120% (ETc120) of crop evapotranspiration were considered as the main plots, and the factorial combination of three levels of zero (N0), 200 (N200) and 400 (N400) kg N ha?1 with three levels of zero (P0), 100(P100) and 200 (P200) kg P ha?1 was considered as the sub plots. The results showed that increasing the consumption of water and P was led to the reduction of N and P utilization efficiency, while RUE increased. WUE was also increased in response to application of N and P, but decreased when ETC increased. DM yield under ETc80 treatment reduced by 11 and 12%, respectively, compared to ETc100 and ETc120 which was due to reduction of cumulative absorbed radiation (Rabs(cum)) and RUE. Under these conditions, changes of stomatal conductance (gs) had little effect on DM yield. It was also found that N limitation caused 11 and 20% reduction in DM yield compared to N200 and N400, respectively. This yield reduction was mainly the result of decrease in RUE. By decreasing Rabs(cum), P deficiency also reduced DM yield by 5 and 9%, respectively, relative to P100 and P200 treatments. 相似文献
24.
The effects of fascioliasis on the activities of some drug-metabolizing enzymes in desert sheep liver. 总被引:1,自引:0,他引:1
H A Elsheikh B H Ali A M Homeida A A Lutfi H J Hapke 《The British veterinary journal》1992,148(3):249-257
Desert sheep experimentally or naturally infected with Fasciola gigantica were used to study the influence of infection on the activities of some drug-metabolizing enzymes found in the liver. The enzymes investigated were aminopyrine N-demethylase, aniline 4-hydroxylase and UDP-glucuronyltransferase. The experimental infection was confirmed histologically by detection of Fasciola eggs in faeces and by measuring the activities of sorbitol dehydrogenase (SD), glutamate dehydrogenase (GD) and aspartate aminotransferase (AST) in plasma during the course of the disease. Liver specimens from naturally infected sheep were obtained from the slaughter house. The activities of aminopyrine N-demethylase and aniline 4-hydroxylase were significantly decreased in sheep either naturally infected or during the acute stage of experimental fascioliasis (killed 5 weeks post-infection). The activity of UDP-glucuronyltransferase was decreased in naturally infected sheep and those killed 9 or 13 weeks post-experimental infection. 相似文献
25.
水分胁迫对扁桃砧木干物质和叶绿素含量的影响 总被引:1,自引:0,他引:1
以新疆常用的扁桃砧木石头扁桃和毛桃的1年生实生苗为材料,设置土壤相对含水量分别为田间最大持水量的100%、80%、60%、40%和20%5个处理,研究了不同水分胁迫条件对其干物质和叶绿素含量的影响。水分胁迫处理第10、20、30天后取样,测定其叶绿素含量;在水分胁迫处理第30天取样测定其干物质含量。结果表明:2个供试品种对水分胁迫的反应一致。在土壤相对含水量为80%时,总干物质含量和叶质量比最高,土壤相对含水量较多或较少都会减少干物质的积累,石头扁桃总干物质含量和叶质量比的下降幅度大于毛桃。根质量比和根冠比在土壤相对含水量为80%时最低,随着水分胁迫程度的加剧,根质量比和根冠比升高,石头扁桃的升高幅度大于毛桃。在土壤相对含水量为80%时叶绿素a和叶绿素(a b)的含量最高,随着胁迫程度的加剧和时间的延长,叶绿素a和叶绿素(a b)的含量降低,石头扁桃的降低幅度大于毛桃。 相似文献
26.
Mai H. ElNaggar Ghada M. Abdelwahab Omnia Kutkat Mohamed GabAllah Mohamed A. Ali Mohamed E. A. El-Metwally Ahmed M. Sayed Usama Ramadan Abdelmohsen Ashraf T. Khalil 《Marine drugs》2022,20(3)
Several natural products recovered from a marine-derived Aspergillus niger were tested for their inhibitory activity against SARS CoV-2 in vitro. Aurasperone A (3) was found to inhibit SARS CoV-2 efficiently (IC50 = 12.25 µM) with comparable activity with the positive control remdesivir (IC50 = 10.11 µM). Aurasperone A exerted minimal cytotoxicity on Vero E6 cells (CC50 = 32.36 mM, SI = 2641.5) and it was found to be much safer than remdesivir (CC50 = 415.22 µM, SI = 41.07). To putatively highlight its molecular target, aurasperone A was subjected to molecular docking against several key-viral protein targets followed by a series of molecular dynamics-based in silico experiments that suggested Mpro to be its primary viral protein target. More potent anti-SARS CoV-2 Mpro inhibitors can be developed according to our findings presented in the present investigation. 相似文献
27.
Mahshid Ghavidel Ali Mirshahi Mohammad Azizzadeh Javad Khoshnegah 《Anatomia, histologia, embryologia》2019,48(4):325-333
In the present study, the relationship of normal adrenal dimensions with weight, aortic diameter, age and sex was evaluated. Moreover, a formula for estimating the normal dimensions of adrenal gland was provided. Thirty‐two intact adult dogs that were considered healthy based on history, physical examination, routine blood works and specific adrenal tests as well as absence of any abnormal ultrasonographic findings were included. Adrenal glands and abdominal aorta were imaged in the sagittal plane by ultrasound. Length, maximal height of the cranial and caudal poles, area and circumference of the left and right adrenal glands and also the internal diameter of the abdominal aorta were measured. Analysis showed that there is a positive correlation between the adrenal gland dimensions and weight and aortic diameter. The ratio of adrenal gland dimensions and the aortic diameter was calculated, but this ratio showed a great amount of variability in tandem with a significant correlation to the weight; Meaning that the ratio of the adrenal gland dimensions to the aortic diameter was not a reliable index for evaluating the size of the normal adrenal gland in animals with different weights. Therefore, we used the weight along with adrenal measurements in a linear regression model, and then, we were able to estimate the adrenal gland dimensions in different weights. Knowing the relationship of normal adrenal dimensions with the indices such as weight, age, sex and diameter of abdominal aorta can help the clinicians to diagnose the adrenal gland diseases. 相似文献
28.
ABSTRACT1. Avipoxvirus (APV) infections are one of many threats inflicting economic losses within the poultry industry, particularly in tropical and subtropical countries. A proper and comprehensive study for APVs is needed to increase the knowledge concerning the diversity and evolution of the virus.2. For this purpose, 136 bird flocks of different species and breeding types were examined for APV infection between October 2016 and November 2017. One hundred and thirty samples had visible pocks on the chorioallantoic membrane (CAM) which were designated as fowl pox-like viruses via amplification of 578 bp from the P4b gene and 1800 bp from the fpv140 locus.4. A comprehensive phylogenetic analysis of fpv167 locus (P4b), fpv140 locus (fpv139 and fpv140) and fpv94 (DNA polymerase) revealed that all the analysed strains belong to fowl pox-like viruses (clade A; subclade A1 and A2). Based on the fpv140 locus full nucleotide sequence, three turkey originated strains were seen to be divergent from chicken originated sequences and branched into novel subclade A1.b.5. Trees comparison, within the term of speculation of virus-host specificity, clearly highlighted a high order specific subgrouping among subclades in the case of the fpv140 locus (including fpv139 and fpv140). Hence, the fowl poxvirus, turkey poxvirus and pigeon poxvirus strains clustered into distinct host-specific subclades A1a, A1.b and A2, respectively, which could not be seen in the FWPV-P4b and DNA polymerase phylogeny. 相似文献
29.
A crossbreeding experiment was carried out to determine the sire breed effects on fattening performance of fat-tailed lambs.
Rams from four Iranian fat-tailed sheep breeds, namely Kurdi (K), Afshari (A), Chaal (C) and Sanjabi (S) were mated to Kurdi
ewes producing 454 progeny of four genotype groups (KK, AK, CK and SK). A total of 80 lambs comprising ten female and ten
male lambs from each genotype group were used in a fattening experiment during a period of 88 days. Genotype of the lamb had
significant effect on average dry matter intake (ADMI) (P < 0.05). SK lambs had the lowest ADMI. Average daily gain (ADG) and food conversion ratio (FCR) were not influenced by genotype
of the lamb. Sex of the lamb had significant effect on both ADG and FCR (P < 0.01). Slaughter weight (SLW), hot carcass weight (HCW), cold carcass weight (CCW) and daily carcass gain (DCG) were not
affected by lamb's genotype. However, genotype had significant effect on dressing percentage, carcass loss percentage (P < 0.01), carcass length (CL), leg circumference (LC), carcass compactness (CC) (P < 0.01) and carcass density (CD) (P < 0.05). Carcass width (CW) and leg length (LL) were not affected by lamb's genotype. Sex of the lamb had significant effects
on CL, CW, LC, CC, CD (P < 0.01) and LL (P < 0.05). The results indicated the existence of sire breed difference for daily dry matter intake and carcass conformation
in the fat-tailed sheep. 相似文献
30.
A fusion DNA vaccine co-expressed Eimeria tenella TA4 and chicken IL-2 (chIL-2) was constructed and its efficacy against E. tenella challenge was observed. TA4 gene of E. tenella and chIL-2 gene were cloned into expression vector pcDNA3.1 and pcDNA4.0c in different forms, producing vaccines pcDNA3.1-TA4-IL-2, pcDNA3.1-TA4 and pcDNA4.0c-IL-2. The expression of aim genes in vivo was detected by RT-PCR and western blot. Animal experiment was carried out to evaluate the immune efficacy of the vaccines. Results indicated these DNA vaccines were successfully constructed and the antigen genes could be expressed effectively in vivo. The animal experimental results showed that DNA vaccines could obviously alleviate cecal lesions, body weight loss and increase oocyst decrease ratio. The ACI of pcDNA3.0-TA4-IL-2 group was 192, higher than that of pcDNA3.1-TA4 group. The results suggested that TA4 was an effective candidate antigen for vaccine and co-expression of cytokine with antigen was an alternative method to enhance DNA vaccine immunity. 相似文献