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   823篇
  免费   35篇
  国内免费   3篇
林业   36篇
农学   66篇
基础科学   2篇
  127篇
综合类   48篇
农作物   174篇
水产渔业   38篇
畜牧兽医   301篇
园艺   12篇
植物保护   57篇
  2023年   3篇
  2022年   13篇
  2021年   28篇
  2020年   9篇
  2019年   15篇
  2018年   24篇
  2017年   25篇
  2016年   26篇
  2015年   25篇
  2014年   35篇
  2013年   57篇
  2012年   46篇
  2011年   61篇
  2010年   37篇
  2009年   27篇
  2008年   64篇
  2007年   35篇
  2006年   38篇
  2005年   39篇
  2004年   31篇
  2003年   26篇
  2002年   15篇
  2001年   26篇
  2000年   19篇
  1999年   11篇
  1998年   3篇
  1996年   5篇
  1995年   11篇
  1994年   2篇
  1993年   2篇
  1992年   7篇
  1991年   7篇
  1990年   5篇
  1989年   6篇
  1988年   7篇
  1987年   8篇
  1986年   4篇
  1985年   4篇
  1984年   7篇
  1983年   2篇
  1982年   5篇
  1981年   6篇
  1978年   3篇
  1977年   2篇
  1968年   2篇
  1965年   3篇
  1963年   2篇
  1961年   2篇
  1958年   3篇
  1923年   2篇
排序方式: 共有861条查询结果,搜索用时 343 毫秒
121.
Genic male sterility (GMS) has long been used as a tool for hybrid seed production in chili pepper (Capsicum annuum L.). We developed DNA markers linked to the GMS ms 3 gene in a segregating population using bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) techniques. The segregating population was subjected to BSA-AFLP with 512 primer combinations. Three AFLP markers (Eagg/Mccc276, Eagc/Mctt178, and Ecag/Mtgc204) were identified as tightly linked to the ms 3 locus. Among them, we converted the AFLP marker Ecag/Mtgc204 to the cleavage amplified polymorphic sequence (CAPS) marker, named GMS3-CAPS, based on sequencing analysis of internal and flanking regions for the markers between male-fertile and sterile plants. This marker will be useful for pepper breeding using the GMS system.  相似文献   
122.
Micropigs are the most likely source animals for xenotransplantation. However, an appropriate method for evaluating the lung of micropigs had not been established. Therefore, this study was performed to evaluate the feasibility of 64-channel multi-detector row computed tomography (MDCT) to measure the diameter of the pulmonary arteries and the lung volume in micropigs. The mean diameters of the trachea, and left and right bronchi were 1.6 ± 0.17, 1.18 ± 0.14, and 1.1 ± 0.11 cm, respectively. The mean diameters of the main, right, and left pulmonary arteries were 1.38 ± 0.09, 1.07 ± 0.26, and 0.98 ± 0.13 cm and the diameters of right, left, and common inferior pulmonary veins were 0.97 ± 0.20, 0.76 ± 0.20, and 1.99 ± 0.26 cm, respectively. The mean lung volume was 820.3 ± 77.11 mL. The data presented in this study suggest that the MDCT may be a noninvasive, rapid, and accurate investigational method for pulmonary anatomy in living lung donors.  相似文献   
123.
A comparative study among Korean native cow (Hanwoo), Holstein dairy cow, Korean native goat and crossbred sheep on the population and marker concentration of ruminal microbes, the activities of carboxymethylcellulase (CMCase), xylanase and amylase, and in situ dry matter (DM) degradability were conducted. Twelve ruminally cannulated animals, three of each species, were used. Animals were fed the same diet containing 40% formula feed and 60% rice straw at the level of 2.5% of body weight. Total viable microbial populations in the rumen fluid were significantly (P < 0.01) greater for bacteria and fungi in goat than those of Holstein. The protozoan population among ruminant species was the reverse from that of bacteria. The concentrations of 2,6‐diaminopimelic acid and chitin as markers for bacteria and fungi in the rumen fluid, respectively, were highest in goat, which is in accordance with the above population data. The concentration of aminoethylphosphonic acid as marker of protozoa was highest in Hanwoo and lowest in sheep (P < 0.01). Goat had the highest (P < 0.01) activities of all the enzymes investigated among ruminants. In situ effective degradation of the DM of rice straw was approximately 19% higher in the rumen of goat compared with other animals.  相似文献   
124.
Objective – To determine whether older dogs will have a more pronounced pro‐inflammatory response and blunted anti‐inflammatory response to pathogen‐associated molecular patterns (PAMPs) compared with younger dogs. Design – Prospective. Setting – University teaching hospital. Animals – Thirty‐eight privately owned sexually altered dogs of various ages. Interventions – Blood was collected for HCT, WBC count, plasma biochemical analysis, and whole blood culture. Whole blood was stimulated with lipopolysaccharide (LPS) or, lipoteichoic acid or, peptidoglycan or, addition of phosphate‐buffered saline. Tumor necrosis factor (TNF), interleukin (IL)‐6, and IL‐10 production from whole blood were compared among young, middle aged, and geriatric dogs. Measurements and Main Results – LPS, lipoteichoic acid, and peptidoglycan stimulated significant TNF, IL‐6, and IL‐10 production from canine whole blood compared with phosphate‐buffered saline. Whole blood from geriatric dogs had a blunted IL‐10 response to LPS stimulation and middle‐aged dogs had increased LPS‐induced TNF production compared with the other groups. Conclusion – PAMPs from gram‐positive and gram‐negative bacteria stimulate TNF, IL‐6, and IL‐10 production from canine whole blood. The inflammatory mediator response to PAMPs from gram‐negative bacteria alters with age and may be one factor contributing to mortality in geriatric dogs with sepsis.  相似文献   
125.
In this paper we present the Mexican inventory of greenhouse gas (GHG) emissions from the land-use sector. It involved integration of forest inventory, land-use and soil data in a GIS to estimate the net flux of GHG between 1993 and 2002.  相似文献   
126.
The ‘Genome database for Rosaceae (GDR)’ provides a large collection of expressed sequence tags (ESTs) harboring simple sequence repeats (SSRs) from several Rosaceae genera, including Rosa (rose). Primer pairs flanking SSR were designed for 312 unique Rosa ESTs based on GDR database. Eight rose (Rosa hybrida L.) genotypes were tested for PCR amplification, and 287 (92%) of the primer pairs generated allele-specific PCR bands that were readily scored. From 183 (63.7%) primer pairs that evidenced polymorphic alleles among the eight rose cultivars, 20 pairs evidencing EST sequence homology to known gene functions and high levels of polymorphism were selected and utilized for DNA fingerprinting and genetic diversity assessments of 47 rose hybrids. A total of 202 polymorphic bands were scored and generated unique fingerprints for each rose hybrid. The Nei–Li genetic similarity coefficients among 1081 pair-wise comparisons of 47 cultivars exhibited a broad range of genetic variations from 0.30 (‘Grand King’ and ‘Carnival’) to 0.99 (‘First Red’ and ‘Red Champ’). UPGMA cluster analysis divided 47 hybrids into five major groups and two sub-groups. The cross-species transferability of 273 EST-SSR primer pairs was evaluated using four genotypes of the strawberry, a genus member of the Rosaceae family. PCRs on the DNA samples of strawberry were successful for 165 primer pairs; among these, 123 pairs amplified 243 polymorphic bands. As surrogates of the marker transfer, the phenetic relationship among the four strawberry genotypes was evaluated. Genetic similarity coefficients varied from 0.78 (‘Maehyang’ and ‘Janghyee’) to 0.64 (‘Janghyee’ and ‘Pragana’). The results of cluster analysis showed that the three octaploid strawberry cultivars were quite similar, whereas the diploid ‘Pragana’ was related distantly at the genomic DNA level. The EST-SSR markers developed in the present study can be efficiently utilized for genetic diversity studies in Rosaceae.  相似文献   
127.
Chicken egg yolk immunoglobulin Y (IgY) is a promising alternative for the prevention of enteric gliadin absorption, the predisposing factor of celiac disease (CD). IgY antibody was produced from the egg yolk of Single Comb White Leghorn chickens during the immunization period for the development of an oral immunotherapeutic agent. Here, we report the potential use of spray dried IgY antibody formulation using sugar protectants (mannitol, sorbitol, or microcrystalline cellulose powder (MCCP)). The long-term stability of the spray dried egg yolk powder formulated with 37.5% mannitol (EYP-M) preserved IgY antibody activity at 99.9%, which was significantly higher than that with other protectants (p < 0.05). In a dissolution test, the EYP-M shows 82.4% IgY activity after 2 h in simulated gastric fluid (SGF). A competitive ELISA at 50% inhibition (IC(50)) shows that 1.6 mg/mL EYP-M bound to 7.6 mg/mL and 10.5 mg/mL gliadin in SGF without and with food matrix conditions, respectively, whereas in simulated intestinal fluid, the formulation bound to 10 mg/mL gliadin, regardless of a food matrix. In-vivo study: BALB/c mice fed with EYP-M and gliadin at a ratio of 1:5 (w/w) demonstrated that gliadin absorption in the gastrointestinal tract was minimal at <1%. Thus, EYP-M containing IgY antibody may be used in CD patients to eliminate the effects of ingested toxic gliadin.  相似文献   
128.
Rubusoside (R) is a natural sweetener and a solubilizing agent with antiangiogenic and antiallergic properties. However, currently, its production is quite expensive, and therefore, we have investigated nine commercially available glycosidases to optimize an economically viable R-production method. A stevioside (ST)-specific β-glucosidase (SSGase) was selected and purified 7-fold from Aspergillus aculeatus Viscozyme L by a two-step column chromatography procedure. The 79 kDa protein was stable from pH 3.0 to pH 7.0 at 50-60 °C. Hydrolysis of ST by SSGase produced R and steviol monoglucosyl ester as determined by (1)H and (13)C nuclear magnetic resonance (NMR). Importantly, SSGase showed higher activity toward ST than other β-linked glucobioses. The optimal conditions for R production were 280 mM ST and 16.6 μL of SSGase at pH 5.1 and 63 °C. This is the first discussion detailing the production of R by enzymatic hydrolysis of ST and is useful for the food additive and pharmaceutical industries.  相似文献   
129.
Cultivation of green manure plants during the fallow season in rice paddy soil has been strongly recommended to improve soil properties. However, green manuring may impact greenhouse gas emission, methane (hereafter, CH4) in particular, under the flooded rice cultivation and thus, application of chemical amendments being electron acceptors can be an effective mitigation strategy to reduce CH4 emissions in irrigated rice (Oryza sativa L.) field amended with green manure. To investigate the effect of iron (Fe) slag silicate fertilizer (hereafter, silicate fertilizer), which was effective in reducing CH4 emission and increasing rice productivity, in green manure-amended paddy soil, the aboveground biomass of Chinese milk vetch (hereafter, vetch) was added at rates of 0, 10, 20, and 40 Mg (fresh weight) ha−1 before the application of silicate fertilizer, which was added at rates of 0 and 2.3 Mg ha−1. Silicate fertilization reduced the seasonal CH4 flux by ca. 14.5% and increased rice yield by ca. 15.7% in the control (no vetch application) treatment. However, CH4 production was increased by silicate fertilization in vetch-treated soil particularly at the initial rice growing stage, which was probably due to the enhanced decomposition of added organic matters by the silicate liming effect. In conclusion, silicate fertilization is not effective in reducing CH4 production in green manure-amended rice paddy soils and its use should be properly controlled.  相似文献   
130.
Soybean seed includes various bioactive substances. Also, they contain a variety of antinutritional factors including lipoxygenase, Kunitz trypsin inhibitor (KTI), lectin, and 7S α' subunit proteins. The genetic removal of these proteins will improve the nutritional value of soybean seed. The objective of this research was to breed new soybean with tetra recessive alleles (lox1lox2lox3/lox1lox2lox3ti/tile/lecgy1/cgy1) for lipoxygenase, KTI, lectin, and 7S α' subunit proteins. Seven parents were used to breed tetra null strain. SDS‐PAGE and Western blot analysis were used to determine the presence or absence of lipoxygenase, 7S α' subunit, KTI, and lectin proteins in mature seed. Tetra null soybean line has a purple flower, determinate growth habit, tan pod, and yellow seed coat colour. Stem height of the breeding line was 62.3 cm. The 100‐seed weight of the breeding line was 27.1 g and yield (t/ha) was 2.84. This is the first soybean strain with lox1lox2lox3/lox1lox2lox3ti/tile/lecgy1/cgy1 genotype (absence of lipoxygenase, KTI, lectin, and 7S α' subunit proteins).  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