首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1229篇
  免费   56篇
  国内免费   6篇
林业   56篇
农学   63篇
基础科学   2篇
  162篇
综合类   62篇
农作物   36篇
水产渔业   83篇
畜牧兽医   741篇
园艺   11篇
植物保护   75篇
  2022年   4篇
  2021年   19篇
  2020年   18篇
  2019年   21篇
  2018年   23篇
  2017年   34篇
  2016年   31篇
  2015年   33篇
  2014年   40篇
  2013年   89篇
  2012年   73篇
  2011年   74篇
  2010年   29篇
  2009年   36篇
  2008年   53篇
  2007年   57篇
  2006年   74篇
  2005年   77篇
  2004年   61篇
  2003年   57篇
  2002年   32篇
  2001年   42篇
  2000年   49篇
  1999年   41篇
  1998年   5篇
  1997年   9篇
  1996年   7篇
  1995年   4篇
  1994年   4篇
  1992年   14篇
  1991年   15篇
  1990年   16篇
  1989年   15篇
  1988年   16篇
  1987年   18篇
  1986年   9篇
  1985年   7篇
  1984年   5篇
  1983年   8篇
  1982年   4篇
  1981年   4篇
  1979年   9篇
  1977年   7篇
  1974年   5篇
  1972年   7篇
  1970年   3篇
  1968年   3篇
  1967年   3篇
  1966年   3篇
  1965年   3篇
排序方式: 共有1291条查询结果,搜索用时 93 毫秒
991.
A simplified and rapid procedure for the determination of pyroglutamic acid in peptides was developed. The method involves the enzymatic cleavage of an N-terminal pyroglutamate residue using a thermostable pyroglutamate aminopeptidase and isocratic HPLC separation of the resulting enzymatic hydrolysate using a column switching technique. Pyroglutamate aminopeptidase from a thermophilic archaebacteria, Pyrococcus furiosus, cleaves N-terminal pyroglutamic acid residue independent of the molecular weight of the substrate. It cleaves more than 85% of pyroglutamate from peptides whose molecular weight ranges from 362.4 to 4599.4 Da. Thus, a new method is presented that quantitatively estimates N-terminal pyroglutamic acid residue in peptides.  相似文献   
992.
Carbaryl is one of the carbamate insecticides widely used in agricultural fields and forests. To restore the environment contaminated with carbaryl application, it is suggested that microbial degradation of carbaryl could be an effective method. Two novel bacterial strains degrading rapidly carbaryl were isolated from forest soil. These strains designated as 19B and 19C were identified as novel species ofArthrobacter, respectively based on main bacterial properties including GC-content, major fatty acid composition, major menaquinone isoprenologue and 16S rRNA gene sequence analysis. Strain 19B started to degrade carbaryl within several hours and completely degraded 50μg/ml carbaryl in a mineral salt medium within a day. Similarly, strain 19C showed a high degradation ability. Gas chromatography-mass spectrometry analysis showed that the major degradation metabolite is 1-naphthol (M=144) and minor metabolites are 1,4-naphthalenedione (M=158) and 1,4-naphthalenediol (M=160), suggesting a pathway of carbaryl degradation by both strains. This research was supported by a Grant-in-Aid from the Ministry of Agriculture, Forestry and Fisheries, Japan.  相似文献   
993.
Salmonella typhimurium infection occurred in a children's zoo where 11 fowl and 85 mammals were kept. Initially, the guinea pigs were infected and transmitted the infection to the fowl and rabbits. These mammals responded to medication and cleared of the infection; however, the birds were judged to contain excreters despite four regimens of treatment with antibiotics. Cloacal swabs were taken from all the birds. One turkey was positive for Salmonella and was destroyed. Pooled fecal samples from the birds were again positive. All the birds were tested serologically, and two birds, a goose and a turkey, were positive with Salmonella pullorum-gallinarum antigen, which was assumed to be a cross reaction with S. typhimurium antigen. The two birds were destroyed and the goose yielded Salmonella. The infection was finally eradicated, and the serologic examination was considered to be the most useful procedure for detection of the excreters.  相似文献   
994.
Twenty epidemiologically unrelated Listeria monocytogenes strains isolated from different animals, locations and on different dates in Japan were classified into 18 types by the random amplified polymorphic DNA (RAPD) fingerprinting technique with four primers. Further, seven epidemiologically related L. monocytogenes strains isolated from raw milk and a bulk tank on a dairy farm represented the same RAPD type suggesting that they were all of the same origin. Therefore, RAPD-polymerase chain reaction (PCR) analysis, which is rapid, simple and inexpensive to perform, can be used in surveys as a convenient epidemiological technique.  相似文献   
995.
The inbreeding coefficient (F) is used as a central parameter inferring a proportion of alleles identical by descent within an individual and by genetic variability within a population. The actual inbreeding coefficient varies around a central value, the inbreeding coefficient. C ockerham and W eir (1983) derived the method for computing the variance of inbreeding while reviewing several other methods. The variance of inbreeding in their report was considered to be of two components: one within population and the other between population of varied pedigrees. If pedigree is fixed, F is easily computed for an individual by the standard method (F alconer 1989). For domestic animals, pedigree information is usually available because it is requisite for a programme of genetic improvement. In this study, the variance of inbreeding coefficient was derived for an individual with a pedigree having a single path to a foundation animal.  相似文献   
996.
This report first describes the morphological and habitat characteristics of larval and juvenile Roughscale Sole Clidoderma asperrimum. Five metamorphosing larvae (22.1–31.7 mm standard length, SL) and 12 juveniles (23.7–46.4 mm SL) were collected from two locations in coastal waters of northeastern Japan, Shizugawa Bay (rocky habitats, 6–12 m depth) and Iwaki (sandy habitats, 10–50 m depth), respectively, using a hand net while SCUBA diving and a small trawl net during May–August in 2008 and 2010. Underwater observation in Shizugawa Bay revealed that metamorphosing larvae and juveniles that had settled on rocks or stones showed transparent and variegated body coloration, which is cryptic to a rocky habitat. Juveniles in Iwaki showed monotonic coloration. The settlement would occur during metamorphosis because the same larva observed on a stone subsequently swam with a left-lateralized body posture. The larval morphology was characterized by a dense covering of fine spines on the whole body surface. Spines on the ocular side developed steadily, gradually forming bony tubercles with growth, whereas those on the blind side regressed with development and finally disappeared in metamorphosed juveniles. Our results indicate that Roughscale Sole can settle and adapt to rocky and sandy habitats in coastal waters with wide depth range.  相似文献   
997.
Some species belonging to Ostreopsis, a benthic dinoflagellate genus, are known to produce palytoxin analogues. Around the coastal regions of Japan, the toxic Ostreopsis sp. 1 and Ostreopsis sp. 6 which are genetically divergent from other species of Ostreopsis are present from the southern to northern regions and in the southern region, respectively. The present study examined the growth responses of these strains to seven temperatures (15–35 °C) in combination with five salinities (20–40) and discusses the effects of temperature and salinity on their distribution and bloom dynamics in Japan. Tolerable temperatures and salinities ranged 15–30 °C and 25–40 for Ostreopsis sp. 1, and 17.5–30 °C and 20–40 for Ostreopsis sp. 6. The optimal temperature ranges which gave growth rates of >90 % of maximal growth rate of each strain were 22–25 °C for Ostreopsis sp. 1 and 24–30 °C for Ostreopsis sp. 6. Therefore, Ostreopsis sp. 1 is putatively tolerant to lower temperatures and thus possesses adaptability to colder waters of relatively higher latitude regions of Japan, whereas Ostreopsis sp. 6 presumably possesses adaptability to warmer waters of the southern region. We conclude that growth responses of Japanese toxic Ostreopsis sp. 1 and Ostreopsis sp. 6 to temperature-salinity affect their distribution and bloom dynamics in Japan.  相似文献   
998.
Two soil-borne fungal endophytes almost completely suppressed the effects of a post-inoculated and virulent strain of Fusarium oxysporum f. sp. melonis when inoculated to axenically reared melon seedlings in Petri dishes. They were identified as Cadophora sp. on the basis of ITS 1–5.8S rDNA–ITS 2 sequences and morphological characters and obtained from the roots of Chinese cabbage grown as bait plants in a mixed soil made up of samples from different forest soils from Alberta and British Columbia, Canada. Hyphae of Cadophora sp. grew along the surface of the root and colonized root cells of the cortex and reduced the ingress of the Fusarium pathogen into adjacent cells. Melon seedlings pre-inoculated with Cadophora sp. were also grown in soil amended with the different N sources, nitrate or the amino acids leucine and valine, and glucose (final C:N ratio?=?10:1). After 4 weeks, these seedlings were transplanted into the field and disease symptoms were assessed. Only the endophyte-inoculated seedlings treated with valine could effectively inhibit the development of Fusarium wilt in two plots and reduced disease symptom development by 43 and 62 %.  相似文献   
999.
A passive acoustic telemetry survey was conducted to determine occurrence patterns of commercially important fishes on a steep reef slope along a marine protected area (MPA) in the southern Philippines, where the outer reef edge is often set as an offshore MPA boundary. Based on 4–61 days of tracking data from 21 detected individuals of five species (Lutjanus argentimaculatus, Lutjanus monostigma, Lethrinus atkinsoni, Lethrinus obsoletus, and Siganus guttatus; 20.7–69.2 cm fork length) caught near the reef slope of the MPA, S. guttatus occurred most frequently on the reef flat of the MPA, whereas all individuals of the four lutjanid and lethrinid species were primarily (99.4–100%) detected near the reef slope, and nine individuals (56.3% of these four species) of three of these species (not L. obsoletus) most likely used the shallow (≤10 m) and deep (≥20 m) layers, and thus, middle layers of the slope. These findings indicate that commercially important lutjanid and lethrinid species predominantly and vertically used the areas near the reef slope, suggesting the importance of fully including reef slopes in MPAs to enhance their effectiveness for the conservation of such fishes.  相似文献   
1000.
The influence of sodium fluoride (NaF) on calcium metabolism was examined in nibbler fish (marine teleosts). Two days after the administration of NaF (5 μg/g of body weight) (around 10?4 M in fish), we showed that plasma calcium levels significantly decreased in NaF-treated nibbler fish. In addition, we detected fluoride in the treated scales by use of a scanning electron microscope with an energy-dispersive X-ray microanalysis, indicating that NaF directly affects their scales. Therefore, the influence of NaF on osteoblasts and osteoclasts in the scales was examined. In the scales of NaF-injected nibbler fish, tartrate-resistant acid phosphatase (TRAP) (osteoclastic marker enzyme) decreased, although alkaline phosphatase (osteoblastic marker enzyme) was activated. To confirm the effect of NaF on osteoclasts, furthermore, the mRNA expressions of osteoclastic markers (matrix metalloproteinase-9 and TRAP) were decreased significantly 2 days after incubation. In barred knifejaws, plasma calcium levels decreased as they did in nibbler fish. Therefore, NaF functions in both osteoblasts and osteoclasts and then influences calcium metabolism in marine fish. In the marine environment, high levels of fluoride (1.2–1.5 mg F?/l) (around 10?5–10?4 M) are present in seawater. It is probable that teleosts living in seawater efficiently use fluoride to regulate their blood calcium levels.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号