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   11283篇
  免费   770篇
林业   951篇
农学   416篇
基础科学   56篇
  2335篇
综合类   386篇
农作物   433篇
水产渔业   1001篇
畜牧兽医   5186篇
园艺   189篇
植物保护   1100篇
  2023年   78篇
  2022年   104篇
  2021年   226篇
  2020年   221篇
  2019年   153篇
  2018年   470篇
  2017年   510篇
  2016年   490篇
  2015年   363篇
  2014年   450篇
  2013年   648篇
  2012年   790篇
  2011年   692篇
  2010年   387篇
  2009年   351篇
  2008年   568篇
  2007年   508篇
  2006年   434篇
  2005年   462篇
  2004年   372篇
  2003年   359篇
  2002年   301篇
  2001年   257篇
  2000年   250篇
  1999年   222篇
  1998年   51篇
  1997年   36篇
  1996年   51篇
  1992年   134篇
  1991年   115篇
  1990年   110篇
  1989年   127篇
  1988年   121篇
  1987年   123篇
  1986年   115篇
  1985年   103篇
  1984年   83篇
  1983年   74篇
  1982年   45篇
  1981年   58篇
  1980年   49篇
  1979年   103篇
  1978年   92篇
  1977年   83篇
  1976年   53篇
  1975年   47篇
  1974年   99篇
  1973年   70篇
  1972年   93篇
  1971年   87篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Lupinus albus seeds contain conglutin gamma (Cγ) protein, which exerts a hypoglycemic effect and positively modifies proteins involved in glucose homeostasis. Cγ could potentially be used to manage patients with impaired glucose metabolism, but there remains a need to evaluate its effects on hepatic glucose production. The present study aimed to analyze G6pc, Fbp1, and Pck1 gene expressions in two experimental animal models of impaired glucose metabolism. We also evaluated hepatic and renal tissue integrity following Cγ treatment. To generate an insulin resistance model, male Wistar rats were provided 30% sucrose solution ad libitum for 20 weeks. To generate a type 2 diabetes model (STZ), five-day-old rats were intraperitoneally injected with streptozotocin (150 mg/kg). Each animal model was randomized into three subgroups that received the following oral treatments daily for one week: 0.9% w/v NaCl (vehicle; IR-Ctrl and STZ-Ctrl); metformin 300 mg/kg (IR-Met and STZ-Met); and Cγ 150 mg/kg (IR-Cγ and STZ-Cγ). Biochemical parameters were assessed pre- and post-treatment using colorimetric or enzymatic methods. We also performed histological analysis of hepatic and renal tissue. G6pc, Fbp1, and Pck1 gene expressions were quantified using real-time PCR. No histological changes were observed in any group. Post-treatment G6pc gene expression was decreased in the IR-Cγ and STZ-Cγ groups. Post-treatment Fbp1 and Pck1 gene expressions were reduced in the IR-Cγ group but increased in STZ-Cγ animals. Overall, these findings suggest that Cγ is involved in reducing hepatic glucose production, mainly through G6pc inhibition in impaired glucose metabolism disorders.  相似文献   
2.
Environmental conditions influence phenology and physiological processes of plants. It is common for maize and sorghum to be sown at two different periods: the first cropping (spring/summer) and the second cropping (autumn/winter). The phenological cycle of these crops varies greatly according to the planting season, and it is necessary to characterize the growth and development to facilitate the selection of the species best adapted to the environment. The aim of this study was to characterize phenological phases and physiological parameters in sorghum and maize plants as a function of environmental conditions from the first cropping and second cropping periods. Two parallel experiments were conducted with both crops. The phenological characterization was based on growth analyses (plant height, leaf area and photoassimilate partitioning) and gas exchange evaluations (net assimilation rate, stomatal conductance, transpiration and water-use efficiency). It was found that the vegetative stage (VS) for sorghum and maize plants was 7 and 21 days, respectively, longer when cultivated during the second cropping. In the first cropping, the plants were taller than in the second cropping, regardless of the crop. The stomatal conductance of sorghum plants fluctuated in the second cropping during the development period, while maize plants showed decreasing linear behaviour. Water-use efficiency in sorghum plants was higher during the second cropping compared with the first cropping. In maize plants, in the second cropping, the water-use efficiency showed a slight variation in relation to the first cropping. It was concluded that the environmental conditions as degree-days, temperature, photoperiod and pluvial precipitation influence the phenology and physiology of both crops during the first and the second cropping periods, specifically cycle duration, plant height, leaf area, net assimilation rate, stomatal conductance and water-use efficiency, indicating that both crops respond differentially to environmental changes during the growing season.  相似文献   
3.
New Forests - Adventitious rooting (AR) is an obligatory step for vegetative propagation of commercial woody species. Paper industries have interest in Eucalyptus globulus Labill and its hybrids...  相似文献   
4.
The aim of the work was to study the influence of particle size in the composition, physicochemical, techno-functional and physio-functional properties of two flours obtained from persimmon (Diospyros kaki Trumb. cvs. ‘Rojo Brillante’ (RBF) and ‘Triump’ (THF) coproducts. The cultivar (RBF and THF) and particle size significantly affected all parameters under study, although depending on the evaluated property, only one of these effects predominated. Carbohydrates (38.07–46.98 g/100 g) and total dietary fiber (32.07–43.57 g/100 g) were the main components in both flours (RBF and THF). Furthermore, insoluble dietary fiber represented more than 68% of total dietary fiber content. All color properties studied were influenced by cultivar and particle size. For both cultivars, the lower particle size, the higher lightness and hue values. RBF flours showed high values for emulsifying activity (69.33–74.00 mL/mL), while THF presented high values for water holding capacity (WHC: 9.47–12.19 g water/g sample). The bile holding capacity (BHC) and fat/oil binding values were, in general, higher in RBF (19.61–12.19 g bile/g sample and 11.98–9.07, respectively) than THF (16.12–12.40 g bile/g sample and 9.78–7.96, respectively). The effect of particle size was really evident in both WHC and BHC. Due to their dietary fiber content, techno-functional and physio-functional properties, persimmon flours seem to have a good profile to be used as potential functional ingredient.  相似文献   
5.
Landscape Ecology - Several case studies investigated the role of ecosystem services in participatory planning processes. However, no systematic study exists that cuts across a large number of...  相似文献   
6.
The crossreactivity of mouse monoclonal antibodies (MoAbs) (Tab. I) prepared against human HLA-DR and HLA-DP antigens was studied in various bovine cells: lymphocytes from lymph nodes and peripheral blood, adherent (B) and nonadherent (T) lymphocytes, monocytes, granulocytes and platelets. In the immunofluorescence test, MoAbs Bra13, Bra14, Bra20, Bra22, Bra30, Bra70, HL-38 reacted with bovine B lymphocytes and monocytes, but not with other tested cells (Tab. III, IV). These antibodies, except Bra22, were positive with B lymphocytes in the complement dependent cytotoxic test (Tab. II). The similarity of the bovine antigens and HLA-DR antigens determined by used MoAbs was also proved by immunoblotting. Monoclonal antibodies Bra38 and BraFB6 did not react with the bovine cells and separated antigens. The epitope (HLA-DR) recognized by the antibody Bra38 is probably absent in cattle. The presence of HLA-DP analogue determined by the antibody BraFB6 has not been confirmed. The crossreactive MoAbs could be used for the detection of B lymphocytes and macrophages in veterinary immunology.  相似文献   
7.
The nature of variability of quantitative morphometrical characters was studied in larvae of two local populations of Argas (Argas) polonicus Siuda, Hoogstraal, Clifford et Wassef, 1979 collected in Czechoslovakia and Poland. Statistically significant differences in five quantitative characters studied, in which the larvae of both wild populations differed from one another, disappeared during three generations of laboratory rearing. The variability of these characters was lower in laboratory populations than in field collected ticks. The results of hybridization experiments and analysis of variability of larvae of individual populations and parental pairs suggest that rather adaptive than genetic variation is involved. The genetic component of the variation is inferior and is expressed probably by dominant relations between alleles of the same locus, or by different types of non-allelic interactions.  相似文献   
8.
The indirect fluorescent antibody test (IFAT) was compared with the enzyme-linked immunosorbent assay (ELISA) for the detection of specific antibodies to Sarcocystis sp. A set of 275 ovine blood samples was examined by both reactions. Cystozoites of Sarcocystis gigantea were used as the corpuscular antigen for the IFAT. For the diagnostics of sarcocystosis by the ELISA technique used the sandwich test of the antibody titration with a soluble antigen which was also prepared from S. gigantea macrocysts. Our studies confirmed that this antigen did not cross-react with Toxoplasma gondii. Titre 40 was determined as the limit one for the IFAT and titre 80 for the ELISA; which was confirmed by the direct detection of cysts in the muscles (Svobodová, 1989). The results of both methods are shown in Table I. 76.7% of the blood samples reacted positively in the IFAT and 83.6% in the ELISA. These methods were found to be suitable and can be utilized for the intravital routine diagnostics.  相似文献   
9.
Antibodies to bovine serum albumin were detected in swine sera by use of an immunoblotting technique. Such sera had false-positive reactions, as determined by results of African swine fever virus serodiagnostic techniques when bovine serum albumin was a contaminant in the soluble cytoplasmic antigen obtained from infected cells cultured in the presence of bovine serum. The soluble cytoplasmic antigen obtained from cell cultures infected with African swine fever virus in the presence of porcine serum did not react with the false-positive sera and, therefore, was used for African swine fever virus serodiagnostic methods, with 0% false-positive results.  相似文献   
10.
1. HG and LG quail lines selected for high and low relative weight gain between 11 and 28 d of age (RG11-28), respectively, and an unselected C line were compared. Mature body weight of both selected lines was held at that of the C line. Progeny of generation 6 were used for analysis. 2. Divergent selection for RG11-28 brought about opposite changes in the growth rates shortly after hatching. 3. Parameters of the Richards function were used to describe the growth curve. The largest differences between HG and LG lines occurred in age (t+) and body weight (y+) at the inflection point of the growth curve (on average for both sexes 28% and 20%, respectively). For HG quail, the parameter t+ was 5 d later than that for LG quail (18.6 vs 14.1 d for males and 20.6 vs 15.6 d for females, respectively), and consequently the parameter y+ was greater (90.3 vs 84.0 g for males and 104.5 vs 96.1 g for females, respectively). The shape of the growth curve expressed by the y+/A ratio was substantialy different for HG and LG quail (44.8% vs 39.6% for males and 43.5% vs 36.8% for females, respectively). 4. The food/gain ratios for the fattening period (3 to 35 d of age) were 3.21, 3.47 and 3.34 for the HG, LG and C lines, respectively. The HG quail started to utilise food more efficiently than the LG quail as early as 10 to 14 d, that is, at the age when their relative growth rate first became greater. 5. The relative deviations of the HG and LG lines from the C line are discussed.  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