全文获取类型
收费全文 | 2635篇 |
免费 | 142篇 |
专业分类
林业 | 221篇 |
农学 | 306篇 |
基础科学 | 32篇 |
603篇 | |
综合类 | 125篇 |
农作物 | 204篇 |
水产渔业 | 315篇 |
畜牧兽医 | 679篇 |
园艺 | 77篇 |
植物保护 | 215篇 |
出版年
2023年 | 36篇 |
2022年 | 77篇 |
2021年 | 86篇 |
2020年 | 107篇 |
2019年 | 126篇 |
2018年 | 156篇 |
2017年 | 157篇 |
2016年 | 122篇 |
2015年 | 90篇 |
2014年 | 126篇 |
2013年 | 232篇 |
2012年 | 181篇 |
2011年 | 162篇 |
2010年 | 142篇 |
2009年 | 103篇 |
2008年 | 110篇 |
2007年 | 101篇 |
2006年 | 90篇 |
2005年 | 63篇 |
2004年 | 54篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 42篇 |
2000年 | 34篇 |
1999年 | 26篇 |
1998年 | 18篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 14篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1971年 | 7篇 |
1969年 | 6篇 |
1967年 | 5篇 |
排序方式: 共有2777条查询结果,搜索用时 625 毫秒
931.
Kumar N Jadhao SB Jha AK Kumar K Chandan NK Akhtar MS Aklakur M Kumar S Rana RS 《Fish physiology and biochemistry》2012,38(5):1343-1353
A 2-month preliminary study was conducted to delineate the effect of dietary methyl donors (choline, betaine, and lecithin) on the growth performance and metabolic status of Labeo rohita fingerlings subjected to endosulfan alone and in combination with elevated temperature. Four iso-caloric and iso-nitrogenous diets viz. basal diet, betaine-supplemented diet, choline-supplemented diet and lecithin-supplemented diet were prepared and fed to the different experimental groups throughout the experimental period as per the design. Two hundred and seventy fingerlings (average weight 7.95?±?0.04?g) were randomly distributed in six treatment groups each having three replicates. The experimental groups were as follows: fish subjected to normal water (without endosulfan) and fed with control diet (control group T(0)), fish subjected to endosulfan-treated water and fed with control diet (T(1)), fish subjected to concurrent exposure of endosulfan and elevated temperature and fed with control diet (T(2)), fish subjected to endosulfan and elevated temperature and fed with choline-supplemented diet (T(3)), fish subjected to endosulfan and temperature and fed with betaine-supplemented feed (T(4)), and fish subjected to endosulfan and temperature and fed with lecithin-supplemented feed (T(5)). The result shows that in both the groups, that is, endosulfan exposed and concurrent exposure to endosulfan and elevated temperature group of L. rohita the growth performance like percentage weight gain, feed conversion ratio and specific growth rates were significantly different (P?0.01) when fed with supplemented diet compared with control fed group. The liver LDH and MDH activity were significantly lower in lecithin, betaine, and choline fed groups. The muscle AST as well as G6PDH, AST, and ALT did not vary but liver ALT, gill and liver ATPase, intestine ALP, muscle and liver glycogen varied significantly with dietary supplementation. The liver and gill glutathione-S-transferase (GST) activities were significantly lower in methyl donors-supplemented groups and brain AChE activity showed lower inhibition in supplemented groups in both endosulfan alone and concurrently exposed endosulfan and temperature groups. The result obtained in this study concludes that inclusion of methyl donors, particularly lecithin and betaine in feed as nutritional supplements have potential to improve growth and stress mitigating effect in L. rohita fingerlings. 相似文献
932.
Dabas A Nagpure NS Kumar R Kushwaha B Kumar P Lakra WS 《Fish physiology and biochemistry》2012,38(2):469-482
The effects of different concentrations of cadmium chloride on the extent of lipid peroxidation (LPO) and alterations in the
antioxidant enzyme activities were studied in liver, kidney and gill tissues of freshwater murrel, Channa punctatus. The fish specimens were exposed to 6.7, 13.4 and 20.1 mg l−1 sublethal concentrations of cadmium chloride and the oxidative stress was assessed after 24, 48, 72 and 96 h post-exposure.
The biomarkers selected for the study were thiobarbituric acid reactive substances for assessing the extent of lipid peroxidation
and antioxidant defense system such as reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPX), glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) activities. In general, the cadmium exposure
elevated the LPO in subject tissues of treated group and modulated the activities of GPx, GST, SOD, CAT, GR and level of GSH
after given exposure as compared to the control. All enzymes activities, except CAT (in kidney and gills), and amount of LPO
elevated significantly (P < 0.05) in treated group with respect to control in all tissues, while significant difference was not observed between the
exposed concentrations and within exposure duration. The results indicated that increase in LPO level and the fluctuation
in antioxidant defense system in fish could be due to cadmium-induced increase in the production of reactive oxygen species
(ROS). The potential role of these parameters as biomarkers of heavy metal pollution in aquatic system is discussed. 相似文献
933.
P. Saritha D. Samuel Suman Raj C. Aparna P. Nalini Vijaya Laxmi V. Himabindu Y. Anjaneyulu 《Water, air, and soil pollution》2009,200(1-4):169-179
In the present study, a comparative assessment of 2,4,6-T (2,4,6-Trichlorophenol) degradation by different AOPs (Advanced Oxidation Processes – UV, UV/ H2O2, Fenton, UV/Fenton and UV/TiO2) in the laboratory scale is performed. The effects of different reactant concentrations and pH are assessed. 2,4,6-T removal, Total Organic Carbon mineralization (TOC) and dechlorination are monitored. Of all the AOPs, UV/Fenton process is more effective in degrading 2,4,6-T. The optimum conditions obtained for the best degradation with UV/Fenton are: pH?=?3, Fe+2 concentration of about 5 ppm, and peroxide concentration of 100 ppm for an initial 100 ppm of 2,4,6 T concentration at room temperature. In these conditions, a pseudo first-order rate constant is evaluated. The degradation rate of 2,4,6 T followed the order: $$ {{{\text{UV}}} \mathord{\left/ {\vphantom {{{\text{UV}}} {{\text{Feton}}}}} \right. \kern-\nulldelimiterspace} {{\text{Feton}}}} > {{{\text{UV}}} \mathord{\left/ {\vphantom {{{\text{UV}}} {{\text{TiO}}_{\text{2}} > {{{\text{UV}}} \mathord{\left/ {\vphantom {{{\text{UV}}} {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} > {\text{Feton}}}}} \right. \kern-\nulldelimiterspace} {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} > {\text{Feton}}}}}}} \right. \kern-\nulldelimiterspace} {{\text{TiO}}_{\text{2}} > {{{\text{UV}}} \mathord{\left/ {\vphantom {{{\text{UV}}} {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} > {\text{Feton}}}}} \right. \kern-\nulldelimiterspace} {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} > {\text{Feton}}}}}} > {\text{UV}} $$ 相似文献
934.
N. Sunil N. Sivaraj K. Anitha Babu Abraham Vinod Kumar E. Sudhir M. Vanaja K. S. Varaprasad 《Genetic Resources and Crop Evolution》2009,56(1):115-119
Jatropha curcas L., an important biodiesel plant, has been studied for its distribution and diversity in south east coastal zone of India
using DIVA-GIS. The Grid maps were generated on the distribution pattern, plant height, number of primary branches, collar
length, number of fruits per cluster and oil content. Flowering in the collected accessions were grouped in to very early
(35%), early (29%), medium duration (10%), late (20%), and very late (6%) types. Analysis for richness using rarefaction method
of DIVA-GIS showed that Ranga Reddy district of Andhra Pradesh is the potential area for germplasm with high oil content.
The present study revealed that diverse germplasm accessions of J. curcas are distributed all over the south east coastal zone and enabled us to find out gaps in collection and diversity richness
from SEC zone of India for conservation. 相似文献
935.
水分胁迫下外源ABA对甘蔗叶绿素荧光特性的影响(英文) 总被引:2,自引:0,他引:2
以抗旱甘蔗品种ROC 22与不抗旱品种ROC 16为材料,研究水分胁迫条件下外源ABA对2个甘蔗品种叶片叶绿素含量及叶绿素荧光特性的影响。结果表明,水分胁迫下,ROC 16的叶绿素降解程度高于ROC 22,而外源ABA能够缓解这种降解作用;随着水分胁迫的加剧,两个甘蔗品种叶片的基础荧光(Fo)显著升高,PSⅡ原初光能转化效率(Fv/Fm)和PSⅡ的潜在活性(Fv/Fo)显著下降,光适应下PSⅡ最大光化学效率(Fv’/Fm’)、PSⅡ实际光化学效率(ΦPS2)、光化学猝灭系数(qP)显著下降,表明水分胁迫使甘蔗叶片PSⅡ反应中心受到伤害,施加外源ABA能部分减轻这种伤害,以对ROC 22作用尤为显著。 相似文献
936.
937.
938.
In the present study, the in vivo effects of λ-cyhalothrin and cypermethrin on the activity of acetylcholinesterase (AChE, EC 3.1.1.7) were evaluated for 96 h in brain, muscle and gills of Channa punctatus. Both compounds exhibited tissue specific as well as dose dependent decrease in the activity of AChE. The treated fish showed a significant decrease in the activity of AChE in brain and a lesser inhibition in muscle and gills in response to the increasing concentrations of λ-cyhalothrin as well as cypermethrin. Our results indicated that the brain was the main target organ for both insecticides, followed by muscle and gills, as determined by AChE inhibition study. However, these organs showed variations in the degree of AChE inhibition for separate treatments of both insecticides. The λ-cyhalothrin was a more potent AChE inhibitor as compared to cypermethrin. These findings indicated that apart from the established mechanism of delayed closure of sodium ion channels, these pyrethroids inhibit the activity of AChE in C. punctatus which could further aggravate their neurotoxic effects. 相似文献
939.
Keyath Nisar Jitendra Kumar MB Arun Kumar Suresh Walia Najam A Shakil Rajender Parsad Balraj S Parmar 《Pest management science》2009,65(2):175-182
BACKGROUND: Infestation of seeds by pests during storage leads to deterioration in quality. Seed coating is an effective option to overcome the menace. Unlike synthetic fungicidal seed coats, little is known of those based on botanicals. This study aims at developing azadirachtin‐A‐based pesticidal seed coats to maintain seed quality during storage. RESULTS: Polymer‐ and clay‐based coats containing azadirachtin‐A were prepared and evaluated for quality maintenance of soybean seed during storage. Gum acacia, gum tragacanth, rosin, ethyl cellulose, hydroxyethyl cellulose, polyethyl methacrylate, methyl cellulose, polyethylene glycol, polyvinyl chloride, polyvinyl acetate, polyvinyl pyrrolidone and Agrimer VA 6 polymers and the clay bentonite were used as carriers. The time for 50% release (t1/2) of azadirachtin‐A into water from the seeds coated with the different coats ranged from 8.02 to 21.36 h. The half‐life (T1/2) of azadirachtin‐A in the coats on seed ranged from 4.37 to 11.22 months, as compared with 3.45 months in azadirachtin‐A WP, showing an increase by a factor of nearly 1.3–3.3 over the latter. The coats apparently acted as a barrier to moisture to reduce azadirachtin‐A degradation and prevented proliferation of storage fungi. Polyethyl methacrylate, polyvinyl acetate and polyvinyl pyrrolidone were significantly superior to the other polymers. Azadirachtin‐A showed a significant positive correlation with seed germination and vigour, and negative correlation with moisture content. CONCLUSION: Effective polymeric carriers for seed coats based on azadirachtin‐A are reported. These checked seed deterioration during storage by acting as a barrier to moisture and reduced the degradation of azadirachtin‐A. Copyright © 2008 Society of Chemical Industry 相似文献
940.
Arjunan?JeevalathaEmail author Priyanka?Kaundal Ravinder?Kumar Baswaraj?Raigond Mohit?Gupta Ashwani?Kumar Sanjeev?Sharma Vinay?Sagar Mandadi?Nagesh Bir?Pal?Singh 《European journal of plant pathology / European Foundation for Plant Pathology》2016,145(2):447-458
Complete coat protein (CP) gene sequences of 66 Potato virus X (PVX) isolates were sequenced and compared with other PVX isolates. The CP gene of these isolates shared 93.9–100.0 % and 97.0–100.0 % identities among them at nucleotide and amino acid sequence level, respectively. Phylogenetic analysis with isolates of known PVX strain groups showed that all 66 isolates were found in clade I (strain groups 1, 3 and 4) and none of them in Clade II (strain groups 2 and 4). The Indian isolates had the 714 bp coat protein gene and were closer to clade I isolates with 92.9–99.5 % identities and distantly related to Clade II isolates (74.2 to 80.0 % identities). Hence, these isolates may belong to either of the strain groups 1, 3 and 4. A threonine residue at position 122 and glutamine residue at position 78 were found conserved in all the Indian isolates suggesting that these isolates cannot overcome Rx1gene and Nx gene mediated resistance, characteristic of group 1 and 3. However, unique amino acid substitutions were observed in Indian isolates and further studies are required to ascertain their role in symptom expression, virulence and host range. In addition, whole genome sequences of two isolates one each from Jalandhar (Punjab) and Kufri (Himachal Pradesh) were also determined. They were 6435 nts long with five ORFs and shared 81.4–97.2 % identities to clade I isolates from USA, Russia, India, Iran, China, Japan, Taiwan and 77.0 to 77.5 % identities with clade II isolates from Peru. 相似文献