全文获取类型
收费全文 | 481篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
林业 | 58篇 |
农学 | 50篇 |
基础科学 | 7篇 |
114篇 | |
综合类 | 25篇 |
农作物 | 44篇 |
水产渔业 | 48篇 |
畜牧兽医 | 91篇 |
园艺 | 5篇 |
植物保护 | 57篇 |
出版年
2023年 | 14篇 |
2022年 | 12篇 |
2021年 | 12篇 |
2020年 | 14篇 |
2019年 | 20篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 5篇 |
2014年 | 18篇 |
2013年 | 50篇 |
2012年 | 28篇 |
2011年 | 27篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 18篇 |
2006年 | 17篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 4篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1966年 | 3篇 |
排序方式: 共有499条查询结果,搜索用时 15 毫秒
491.
A series of half-diallel crosses involving early, medium and late maturity desi and kabuli type chickpea (Cicer arietinum L.) genotypes with stable resistance to Helicoverpa pod borer, along with the parents, were evaluated at two locations in India to understand the inheritance of pod borer resistance
and grain yield. Inheritance of resistance to pod borer and grain yield was different in desi and kabuli types. In desi type chickpea, the additive component of genetic variance was important in early maturity and dominance component was predominant
in medium maturity group, while in the late maturity group, additive as well as dominance components were equally important
in the inheritance of pod borer resistance. Both dominant and recessive genes conferring pod borer resistance seemed equally
frequent in the desi type parental lines of medium maturity group. However, dominant genes were in overall excess in the parents of early and
late maturity groups. In the kabuli medium maturity group, parents appeared to be genetically similar, possibly due to dispersion of genes conferring pod borer
resistance and susceptibility, while their F1s were significantly different for pod borer damage. The association of genes conferring pod borer resistance and susceptibility
in the parents could be attributed to the similarity of parents as well as their F1s for pod borer damage in kabuli early and late maturity groups. Grain yield was predominantly under the control of dominant gene action irrespective of the
maturity groups in desi chickpea. In all the maturity groups, dominant and recessive genes were in equal frequency among the desi parental lines. Dominant genes, which tend to increase or decrease grain yield are more or less present in equal frequency
in parents of the early maturity group, while in medium and late maturity groups, they were comparatively in unequal frequency
in desi type. Unlike in desi chickpea, differential patterns of genetic components were observed in kabuli chickpea. While the dominant genetic component was important in early and late maturity group, additive gene action was involved
in the inheritance of grain yield in medium duration group in kabuli chickpea. The dominant and recessive genes controlling grain yield are asymmetrically distributed in early and medium maturity
groups in kabuli chickpea. The implications of the inheritance pattern of pod borer resistance and grain yield are discussed in the context
of strategies to enhance pod borer resistance and grain yield in desi and kabuli chickpea cultivars. 相似文献
492.
Feeding stimulants (phagostimulants) increase the food uptake by the host insect larvae and thereby play a vital role in enhancing overall activity of insect viruses formulated as biopesticides. A local strain of granulovirus of Pieris brassicae (PbGV), a serious pest of cole crops worldwide, has shown potential as a biopesticide against this pest and with slight increase in its efficacy can be used successfully as a promising biocontrol agent in integrated pest management (IPM) programs of the pest. The addition of phagostimulants may enhance the efficacy but so far no specific phagostimulant for PbGV has been reported. In the present studies, some reported phagostimulants for insect viruses were tested for their impact on food utilization by host larvae and efficacy of the virus. The specified concentration of virus isolate was mixed with phagostimulants and laboratory studies were conducted to uncover their effect on consumption index (CI) and larval mortality. The studies revealed that phagostimulants, viz. boric acid and crude sugar, when mixed with PbGV, showed highest CI and larval mortality. Consumption index of 1.34, 1.49 and 1.43 mg/mg/day and corresponding larval mortality of 32.9%, 45.8% and 34.2% were recorded with the addition of 0.5% and 1% boric acid and 2% crude sugar, respectively, in PbGV. The leaf extracts of cabbage, cauliflower and broccoli at both the concentrations (1% and 2%) also enhanced the CI but were comparatively less effective than the boric acid and crude sugar. Field evaluation of PbGV alone and in combination with phagostimulants carried out at two geographically isolated locations, viz. Palampur (subtropical) and Sangla (temperate) on three cole crops (cabbage, cauliflower and broccoli) showed that boric acid was the most promising candidate for enhancing the PbGV efficacy under field conditions, followed by crude sugar. 相似文献
493.
Tiwari Rahul Kumar Bashyal Bishnu Maya Shanmugam V. Lal Milan Kumar Kumar Ravinder Sharma Sanjeev Naga Kailash Chandra Chourasia Kumar Nishant Aggarwal Rashmi 《植物病害和植物保护杂志》2022,129(1):173-179
Journal of Plant Diseases and Protection - Potato stands first as a non-cereal food crop for global consumption purposes. During the year 2019–20, dry rot disease symptoms were observed on... 相似文献
494.
Both engineering and evolution are constrained by trade-offs between efficiency and robustness, but theory that formalizes this fact is limited. For a simple two-state model of glycolysis, we explicitly derive analytic equations for hard trade-offs between robustness and efficiency with oscillations as an inevitable side effect. The model describes how the trade-offs arise from individual parameters, including the interplay of feedback control with autocatalysis of network products necessary to power and catalyze intermediate reactions. We then use control theory to prove that the essential features of these hard trade-off "laws" are universal and fundamental, in that they depend minimally on the details of this system and generalize to the robust efficiency of any autocatalytic network. The theory also suggests worst-case conditions that are consistent with initial experiments. 相似文献
495.
Krkosek M Ford JS Morton A Lele S Myers RA Lewis MA 《Science (New York, N.Y.)》2007,318(5857):1772-1775
Rather than benefiting wild fish, industrial aquaculture may contribute to declines in ocean fisheries and ecosystems. Farm salmon are commonly infected with salmon lice (Lepeophtheirus salmonis), which are native ectoparasitic copepods. We show that recurrent louse infestations of wild juvenile pink salmon (Oncorhynchus gorbuscha), all associated with salmon farms, have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction. The louse-induced mortality of pink salmon is commonly over 80% and exceeds previous fishing mortality. If outbreaks continue, then local extinction is certain, and a 99% collapse in pink salmon population abundance is expected in four salmon generations. These results suggest that salmon farms can cause parasite outbreaks that erode the capacity of a coastal ecosystem to support wild salmon populations. 相似文献
496.
The ultrastructure of Katahdin tubers infected with potato virus X (PVX) is compared with PVX-free tubers by electron microscopy. Electron-dense globules surrounding the inner periphery of the tonoplast were observed in PVX-infected tubers, while PVX-free tubers did not show such bodies. Other organelles were comparable in PVX-infected and PVX-free tubers 相似文献
497.
Patil SB Ghadyale VA Taklikar SS Kulkarni CR Arvindekar AU 《Plant foods for human nutrition (Dordrecht, Netherlands)》2011,66(1):85-90
Spices are extensively used to enhance the taste and flavor of foods and are known to possess several medicinal properties.
Myristica fragrans, Parmelia perlata, Illicium verum, Trachyspermum copticum and Myristica malabarica, the commonly used spices in India were assessed for antidiabetic activity in streptozotocin induced diabetic rats. In the
in vitro insulin secretion studies on isolated islets of Langerhans, M. fragrans, T. copticum and M. malabarica showed dose dependent insulin secretion. At 1 mg/ml, P. perlata showed significant in vitro alpha-glucosidase inhibitory activity with IC50 value of 0.14 mg/ml followed by M. malabarica (0.64 mg/ml), I. verum (0.67 mg/ml), M. fragrans (0.85 mg/ml) and T. copticum (0.92 mg/ml). The DPPH free radical scavenging activity of the extracts at a concentration of 1 mg/ml was as M. malabarica (90.45%), M. fragrans (89.89%), I. verum (87.22%), P. perlata (76.70%) and T. copticum (38.14%). P. perlata showed the highest phenolic content (i.e., 118.5 mg gallic acid equivalents/g) followed by M. malabarica (84.13 mg gallic acid equivalents/g). M. malabarica showed the highest flavonoid content (i.e., 38.35 mg quercetin equivalents/g). Regular use of these spices may prevent postprandial
rise in glucose levels through inhibition of intestinal alpha-glucosidase and may maintain blood glucose level through insulin
secretagogue action. 相似文献
498.
The effect of freezing on the turgor, ascorbic acid content and enzymatic discoloration of Katahdin and Atlantic potatoes was studied. Tubers were exposed to a temperature of ?20°C for 24 hrs. then thawed for 1 hr. at 20°C before analysis. Frozen tubers were then compared with unfrozen controls. Both varieties lost turgor following freezing and exuded a sticky liquid with increased thawing time. At the end of 3 hrs. thawing, a sponge-like texture was observed in both varieties. In both varieties freezing resulted in a significant reduction (p<.01) in ascorbic acid and phenolic content (p<.01). Enzymatic discoloration was also significantly reduced (p<.01) in both varieties. 相似文献
499.
ABSTRACT An experiment was conducted to evaluate the spawning performance and egg quality of Clarias batrachus at variable latency periods (11, 14, 17, 20, and 23 h) and doses of carp pituitary extract (10, 20, 30, 40, and 50 mg/kg). The fish could not be stripped at 11 h latency with 10 or 20 mg carp pituitary extract (CPE). The highest quantity of eggs was obtained at 14 to 23 h latency with 30–40 mg CPE or 50 mg CPE with 14 to 17 h latency, which did not vary significantly (P < 0.05) at a water temperature of 27°C–28.5°C. The eggs did not fertilize and hatch when stripped at 11-h latency period. Over 80% of total eggs stripped from females injected with 30 and 40–50 mg CPE per kg body weight, and stripped at 14 to 23 h and 14- to 17-h latency, respectively, were fertilized. However, the highest (P < 0.05) number of larvae was obtained from females injected with 40 mg CPE and stripped at 14 or 17 h latency periods. Therefore, this CPE dose and 17 h latency period combination was regarded as the best for obtaining the highest number of larvae during induced spawning of C. batrachus. 相似文献