全文获取类型
收费全文 | 867篇 |
免费 | 39篇 |
国内免费 | 1篇 |
专业分类
林业 | 61篇 |
农学 | 55篇 |
基础科学 | 8篇 |
225篇 | |
综合类 | 42篇 |
农作物 | 165篇 |
水产渔业 | 110篇 |
畜牧兽医 | 165篇 |
园艺 | 20篇 |
植物保护 | 56篇 |
出版年
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 37篇 |
2020年 | 34篇 |
2019年 | 46篇 |
2018年 | 51篇 |
2017年 | 64篇 |
2016年 | 69篇 |
2015年 | 38篇 |
2014年 | 55篇 |
2013年 | 99篇 |
2012年 | 69篇 |
2011年 | 77篇 |
2010年 | 46篇 |
2009年 | 35篇 |
2008年 | 68篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2000年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有907条查询结果,搜索用时 78 毫秒
1.
Retracted: Study of testis histology and sperm morphology in the Bunnei,Barbus sharpeyi (Gunther, 1874) induced by luteinizing hormone‐releasing hormone analogue and carp pituitary extract 下载免费PDF全文
This study was conducted to determine the effects of hormone treatment on testis structure in Barbus sharpeyi, as well as the morphology of sperm examined by scanning electronic microscopy (SEM). Male B. sharpeyi were divided into three groups (three fish per group) and injected with luteinizing hormone – releasing hormone analogue (LHRH–A2) or carp pituitary extract (CPE). The first and second groups were treated with 10 μg kg?1 LHRH–A2 and metoclopramide (MET), and their testis were sampled pre‐ and Poststripping respectively. The third group received 2 mg kg?1 CPE and were killed pre‐stripping. Based on the histological results obtained, the testicular connective tissue of the lumen was thicker, and seminal vesicles were of a lower volume, in fish injected with CPE in comparison to the other groups. After treatment with LHRH–A2 and MET, not all spermatozoa within the testis were ejaculated, and only a small amount of sperm was obtained by abdominal stripping. The highest and lowest diameters of connective tissue within lobules were observed in fish receiving CPE and LHRH–A2 treatments respectively. There was a significant difference (P < 0.05) in lobule space between the fish injected with the CPE and the fish injected with the LHRH–A2 and MET. The SEM results revealed that the spermatozoa of B. sharpeyi were composed of a spherical to elliptical head, a cylindrical midpiece, and a lengthy flagellum. In conclusion, it was found that injection with LHRH–A2 and MET improved the spermatogenic process in comparison to injection with CPE. 相似文献
2.
Saeid Mobini Hamid Khazaei Thomas D. Warkentin Albert Vandenberg 《Plant Breeding》2020,139(6):1181-1189
The aim of this study was to reduce the length of the breeding cycle for faba bean by accelerating seed setting. We examined the mode and time of exogenous 6-benzylaminopurine (BAP) (cytokinin) application, and cold treatments and their combinations in two faba bean genotypes. Acropetal node number of pod and seed set and pollen viability were recorded during the experiments. Application of BAP improved pollen germination. The application of 10–5 M BAP 4 days after flowering increased seed set at the lower nodes. Cold treatment (8/4°C day/night for 2 days) after the onset of flowering induced the formation of more pods and faster pod set compared to the non-cold treatment. The time to first seed was significantly reduced, and pollen viability was increased in plants exposed to cold treatment. Increased pollen viability also showed a significant positive correlation with seed setting. The combinations of 10–5 BAP and cold treatment together had similar and independent effects. These results will accelerate plant breeding in faba bean by providing additional tools for reducing generation time. 相似文献
3.
Anaesthetic efficacy of eugenol on Flowerhorn (Amphilophus labiatus × Amphilophus trimaculatus) 下载免费PDF全文
Reza Tarkhani Ahmad Imani Hadi Jamali Kourosh Sarvi Moghanlou 《Aquaculture Research》2017,48(6):3207-3215
Anaesthetic efficacy of eugenol was investigated on Flowerhorn (Amphilophus labiatus × Amphilophus trimaculatus). A total of 104 fish with average weights of 12 ± 2.5, 28 ± 5 and 53 ±5.1 g were subjected to 25–200 mg L?1 eugenol and behavioural responses as well as induction and recovery times were recorded. Induction and recovery times were significantly affected by eugenol concentration as well as fish weight (P < 0.05). Generally, 49.9–127.3 s after exposure to 50–200 mg L?1 eugenol, fish reached stage 3 anaesthesia (suitable for general handling). Fish entered stage 4 anaesthesia (suitable for surgery and blood sampling) over 57.3–140.4 s post exposure to such concentrations. Recovery time was 91.7–312 s in all weight classes for all eugenol concentrations. Mortality (23%) was only observed in 12‐g fish when were subjected to 200 mg L?1 eugenol. This study showed the behavioural response of Flowerhorn to anaesthesia and eugenol efficacy as an anaesthetic in this important ornamental species. The general quadratic equation revealed that concentrations of eugenol and fish size along with their interactive effects have significantly contributed to the model, with concentration recording the highest beta value in all models (β = ?0.809, ?0.818 and ?0.909, P = 0.000). According to the results, minimum eugenol concentration to induce anaesthesia in less than 3 min was 50 mg L?1. 相似文献
4.
Mohammad Navid Forsatkar Gholamreza Rafiee Hamid Farahmand Gonzalo Martínez-Rodríguez 《Journal Of Applied Aquaculture》2017,29(2):183-196
A study was designed to investigate the possible positive prebiotic effects of mannan oligosaccharides (MOS) on growth and reduction of anxiety behaviors in zebrafish (Danio rerio). The experimental diets were supplemented with 0, 2, 4, 6, or 8 g MOS kg?1 and were fed to juvenile fish (0.47 ± 0.017 g) in triplicates for six weeks. Significant differences were found in the final body weight, body weight intake, percent body weight intake, and specific growth rate among treatments. The regression analyses showed that the optimum MOS level was 4–4.1 g MOS kg?1 diet. Fish fed 4 g MOS kg?1 feed showed higher survival than the other treatments. Also, using the novel tank test, fish fed with 4 g MOS kg?1 diet showed lower anxiety by swimming in the upper portion of the tank. The other behavior parameters remained unaffected by the prebiotic. The results indicated the beneficial effect of the prebiotic MOS on growth and partly on welfare of zebrafish juveniles. 相似文献
5.
Reza Saghafi 《Fibers and Polymers》2017,18(1):41-49
The application of post treatments in preparation of high flux membranes is expanding rapidly. In this work, several hybrid post treatments have been introduced and used for change in the water flux of polysulfone (PSf) hollow fiber membranes. Dry wet spinning method was employed for fabrication of PSf hollow fiber membrane from spinning dope in mass ratio of 15:5:80 of PSf/PVP-K90/NMP. The simultaneous effects of single and hybrid post treatments containing traditional hypochlorite; high pressure injection technique (HPI) of hypochlorite, hot air and hot water treatments on the morphology and water flux of fabricated hollow fibers has been investigated. AFM analysis and image processing of SEM microphotographs of hollow fibers were used for structural studies. The mechanical properties of hollow fibers as well as strain at break and strength also were studied. It was found that the pores size and surface roughness parameter of hollow fiber membranes have been increased after traditional hypochlorite, HPI technique and hot water treatments while decreased when heat treated in air. In general all the employed hybrid post treatments caused to increase in the pores size of hollow fibers although the pores size increase rate in the membranes treated by the hybrid post treatments involving hot air was much lower than the others. The mechanical properties of hollow fibers have been decreased after hybrid and single post treatments containing traditional hypochlorite, HPI technique and hot water treatment while slightly increased after post treatments containing hot air. It was stated that the fabricated PSf hollow fibers were considerably affected by the employed hybrid post treatments. This can be attributed to the combine effects of used post treatments. 相似文献
6.
7.
Mohamed M’BAYE Guohua HUA Hamid Ali KHAN Liguo YANG 《The Journal of reproduction and development》2015,61(5):391-397
Inhibins are members of the TGFβ superfamily and act as suppressors
of follicle stimulating hormone (FSH) secretion from pituitary glands
via a negative feedback mechanism to regulate folliculogenesis. In
this study, the INHBB gene was knocked down by three
RNAi-Ready pSIREN-RetroQ-ZsGreen vector- mediated recombinant plasmids
to explore the effects of INHBB silencing on
granulosa cell (GC) cell cycle, apoptosis and steroid production
in vitro. Quantitative real-time polymerase chain
reaction, Western blot, flow cytometry and ELISA were performed to
evaluate the role of INHBB in the mouse GC cell
cycle, apoptosis and steroid production in vitro. The
results showed that the relative mRNA and protein expression of
INHBB in mouse GCs can be significantly reduced by
RNAi with pshRNA-B1, pshRNA-B2 and pshRNA-B3 plasmids, with pshRNA-B3
having the best knockdown efficiency. Downregulation of the expression
of INHBB significantly arrests cells in the G1 phase
of the cell cycle and increases the apoptosis rate in GCs. This was
further confirmed by downregulation of the protein expressions of
Cyclin D1, Cyclin E and Bcl2, while the protein expression of Bax was
upregulated. In addition, specific downregulation of
INHBB markedly decreased the concentration of
estradiol and progesterone, which was further validated by the
decrease in the mRNA levels of CYP19A1and
CYP11A1. These findings suggest that inhibin βB is
important in the regulation of apoptosis and cell cycle progression in
granulosa cells. Furthermore, the inhibin βB subunit has a role in the
regulation of steroid hormone biosynthesis. Evidence is accumulating
to support the concept that inhibin βB is physiologically essential
for early folliculogenesis in the mouse. 相似文献
8.
Farnaz Kordbacheh Charles L. Mohler Alan G. Taylor Anna S. Westbrook Hamid Rahimian-Mashhadi Hassan M. Alizadeh Antonio DiTommaso 《Weed Research》2023,63(1):34-44
Abutilon theophrasti (velvetleaf) is a widespread and problematic annual weed. Greenhouse and field experiments were conducted to investigate the effects of different cutting methods on the viability of A. theophrasti seeds. Three cutting methods were assessed: (1) Entire plant cut and dried (EPD)—plants were cut at soil level and dried with capsules attached on the greenhouse bench or soil surface for 4 weeks; (2) capsules detached and dried (CD)—capsules were removed from plants and dried for 4 weeks; and (3) capsules detached and tested while fresh (CF)—a control treatment. Before drying, the developmental stage (stage one, dark green; stage two, light green; stage three, yellowish-green; or stage four, black with the slightly open capsule) and age (days after flowering, DAF) of each capsule was recorded. Seed viability was measured immediately in the CF treatment and after the 4-week drying period in the EPD and CD treatments. No seeds in the EPD and CD treatments were viable when harvested at the first developmental stage (1–8 DAF) in either experiment, but 100% of seeds in the CF treatment in the field were viable when harvested at 8 DAF. In both greenhouse and field experiments, seeds attained full viability at earlier harvest ages in CF than in EPD or CD treatments, suggesting that seeds might become viable relatively early in development but lose viability if allowed to dry. These findings could be applied to optimise late-season mechanical control of A. theophrasti. 相似文献
9.
Desertification is one of the main environmental and also social and economic problems facing Iran. Seventeen out of 31 Iranian provinces, which are home to approximately 70% of the total population, are affected by desertification. This study aimed to use geographic information system (GIS) and fuzzy logic for mapping environmentally sensitive areas to desertification based on Mediterranean Desertification and Land Use approach in Isfahan province, central Iran. Six desertification indicators including climate, soil, vegetation, soil erosion, groundwater, and management and policy quality were used to determine various types of environmentally sensitive areas to desertification. Seventeen desertification indices affecting the quality of each indicator were spatially mapped and assigned a value between 0 and 1 using a fuzzy logic option of ArcSDM3 software in GIS environment. Results showed that a 21·7% of the study area was classified as critical, 70% as fragile and 5·5% as potential, and 2·9% of the area was not affected by desertification. In the town of Borkhar, 64·2% of the area was classified as critical, followed by the towns of Isfahan and Nayin with 40·2% and 31·8%, respectively. Results at provincial scale indicated that the climate indicator and humidity index with a weighting mean of 0·71 and 0·77 were the most affective factors in the desertification of the study area. The developed model in this study can be used for mapping desertification status in other 16 provinces that contain desert areas. These assessments provide a GIS‐based desertification database that Iran as a member of the United Nation Convention to Combat Desertification can use to report the condition of desertification at national scale. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
10.
Alleviation of dormancy in walnut kernels by moist chilling is independent from storage protein mobilization 总被引:1,自引:0,他引:1
We studied the effects of moist chilling and warming on storage protein mobilization in walnut (Juglans regia L.) kernels to assess the metabolic inhibition theory, which states that dormant seeds are unable to utilize their own food reserves and that cold conditions allow germination by activating hydrolases involved in reserve mobilization. Stratifying kernels at 5 degrees C for 40 days enhanced their germination. During both cold stratification and warm incubation of kernels, storage protein mobilization occurred in cotyledons rather than axes. Kernel amino acid concentration increased during protein mobilization, with axes of warm-incubated kernels having particularly high amino acid concentrations. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) of the soluble protein fractions from both cold-stratified and warm-incubated cotyledons revealed increased band intensities of putative glutelins (19-22 and 32-35 kDa). A very high molecular weight protease was detected by gelatin SDS-PAGE that was most active at acid to neutral pHs in imbibed, cold stratified and germinated kernels suggesting the protease(s) was synthesized earlier in the mature seeds. Thus, in dormant walnut kernels there is no block to protein mobilization, and imbibition alone is sufficient to initiate proteolysis. Catalase activity was higher in warm-incubated kernels than in cold-stratified kernels, suggesting that seed aging is hastened under warm conditions and that cold stratification in walnut kernels might involve activation of cellular repair mechanisms. 相似文献