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   607篇
  免费   24篇
林业   62篇
农学   65篇
基础科学   1篇
  107篇
综合类   41篇
农作物   32篇
水产渔业   41篇
畜牧兽医   225篇
园艺   10篇
植物保护   47篇
  2022年   2篇
  2021年   10篇
  2020年   9篇
  2019年   11篇
  2018年   11篇
  2017年   15篇
  2016年   17篇
  2015年   13篇
  2014年   17篇
  2013年   44篇
  2012年   44篇
  2011年   38篇
  2010年   16篇
  2009年   14篇
  2008年   30篇
  2007年   38篇
  2006年   34篇
  2005年   39篇
  2004年   33篇
  2003年   29篇
  2002年   23篇
  2001年   22篇
  2000年   22篇
  1999年   14篇
  1998年   6篇
  1997年   2篇
  1995年   7篇
  1994年   4篇
  1993年   2篇
  1992年   4篇
  1991年   4篇
  1990年   8篇
  1989年   6篇
  1988年   4篇
  1987年   6篇
  1985年   4篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1980年   1篇
  1979年   6篇
  1978年   3篇
  1977年   2篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
  1972年   1篇
  1967年   1篇
  1956年   1篇
  1952年   2篇
排序方式: 共有631条查询结果,搜索用时 31 毫秒
121.
The factors involved in the successful escape of overwintered larvae of Epinotia granitalis from host oleoresin in the phloem of Cryptomeria japonica were studied. The mortality, period, and body weight of E. granitalis overwintered larvae while feeding on the phloem of C. japonica were compared with the same parameters for Semanotus japonicus larvae. The seasonal fluctuation in the ability of C. japonica to form traumatic resin canals in the phloem was also assessed. The oleoresin mortality of E. granitalis was low compared with that of S. japonicus. Although both species started feeding on approximately the same date in spring, the feeding period of E. granitalis was only about 24 days, showing that E. granitalis faced the danger of host oleoresin for a shorter period than S. japonicus. The larval weight of E. granitalis was consistently greater than that of S. japonicus through the phloem-feeding period of E. granitalis, and the growth rate was also higher in E. granitalis, suggesting that E. granitalis had a better ability to avoid host oleoresin. These results demonstrated that not only the feeding habits, that is, the tendency of a single larva to feed at several sites, but also the shorter feeding period and larger body size were probably the important factors facilitating escape of E. granitalis from host oleoresin mortality. Furthermore, the ability of C. japonica to form traumatic resin canals increased after the starting date of larval feeding in spring. Because E. granitalis finished feeding before the culmination of the ability of C. japonica to form traumatic resin canals, it was likely that the shorter feeding period was the most important factor in enabling E. granitalis to escape from mortality by host oleoresin.  相似文献   
122.
A technique for screening immune-enhancing polysaccharides in food using the phagocytotic activity of 1,25-dihydroxyvitamin D3 (VD3)-differentiated HL60 cells is presented. HL60 cells, a human acute promyelocytic cell line, can differentiate along the monocytic lineage following exposure to VD3 or phorbol-12-myristate-13-acetate (PMA). For differentiated cells along the monocytic pathway, HL60 cells were maintained in RPMI 1640 medium supplemented with 10% FBS and 120 nM VD3 for more than 1 week. VD3-differentiated HL60 cells were seeded into 48-well plates, YG-labeled microspheres and polysaccharides were added and mixed using a plate shaker at 1100 rpm for 30 s, and then the mixture was incubated overnight at 37 degrees C in 5% CO2. The cells were fixed with 2% formaldehyde and resuspended in phosphate-buffered saline. The rate of phagocytosis was measured with a flow cytometer. VD3-differentiated cells but not non- and PMA-differentiated cells resulted in an elevation of phagocytic activity by various immune-enhancing polysaccharides in foods.  相似文献   
123.
The incidence of primary and secondary glaucoma in dogs was investigated. A total of 1244 dogs received ophthalmologic examinations, including tonometry and gonioscopy. Goniophotographs were taken using a goniolens to evaluate the iridocorneal angle (ICA) as well as pectinate ligament (PL). The anterior width of the ciliary cleft and the total distance from the origin of the PL to the anterior corneal surface were measured from the goniophotographs. Glaucoma was diagnosed based on the cupping of the optic nerve head, clinical signs, ocular changes, and high IOP, and it was synchronized with gonioscopic grades to differentiate between primary and secondary glaucoma. We investigated 1244 dogs of 29 breeds, including the mixed breed; among these, glaucoma was diagnosed in 127 dogs (162 eyes). Of 162 eyes, primary glaucoma was diagnosed in 129 eyes and secondary glaucoma in 33 eyes. Shiba Inu dogs (42 dogs, 33%) showed the highest incidence of glaucoma, followed by Shih-Tzu (21 dogs, 16.5%). Furthermore, all the glaucomatous Shiba Inu dogs had primary glaucoma with abnormal ICA grades and dysplastic PLs. The findings of our study reveal that the Shiba Inu breed in Japan may have a hereditary predisposition to glaucoma.  相似文献   
124.
Interleukin 2 (IL-2) is a T cell proliferation factor released by Th0- and Th1-type helper T cells and is an essential cytokine for immune responses. In the present study, recombinant glutathione S-transferase (GST)-guinea pig IL-2 (GPIL-2) fusion protein was prepared by Escherichia coli (E. coli) and by using this protein as an immunogen, monoclonal antibodies (mAbs) against GPIL-2 were produced to establish a basis for a research on immune responses in guinea pigs. Three stable hybridoma cell lines were established, and specific binding of each mAb to recombinant GPIL-2 produced by E. coli and insect cells infected with recombinant baculovirus was shown by enzyme linked immunosorbent assay (ELISA) and/or immunoblot analysis. Isotype analyses of these mAbs revealed that all three mAbs were IgG1 and had kappa chain. Furthermore, assessment of their epitopes by competition binding assay indicated that the mAbs obtained in this study bound to three different epitopes. Thus, a sandwich ELISA based on the two mAbs specific to different GPIL-2 epitopes was developed for detection of GPIL-2, which had a sensitivity threshold of about 0.3 ng/ml of GPIL-2.  相似文献   
125.
The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.  相似文献   
126.
127.
We examined the use of external measurements and relative fat deposition of adult feral raccoons (Procyon lotor) to develop relative indices of body fat deposition in post-growth feral raccoons. From March 2006 to March 2010, 288 adult raccoon carcasses (110 males, 178 females) collected in Kanagawa Prefecture, Japan, which were determined to be 24 months old, were subjected to external measurements of body weight (BW), girth measurement (GM), and body mass index (BMI). To assess relative body fat deposition, we visually classified abdominal subcutaneous fat into three grades (Visible Fat Index [VFI]: I-III). Significant differences in the means of BW (both sexes:P<0.01), GM (females: P<0.05, males: P<0.01), and BMI (both sexes: P<0.01) were detected between seasons. Notably, the means of BW, GM, and BMI (all, both sexes: P<0.01) differed significantly between VFI grades. However, by discriminant analysis with BW, GM, and BMI as independent variables, we obtained a significant discriminant function (both sexes: P<0.01) for distinguishing VFI I from higher VFI grades, but no significant equation was obtained for distinguishing between VFI II and VFI III. Based on the obtained structure matrix of discriminant analysis, BMI was the most valuable component for the discrimination of VFI grades. Thus, we conclude that BMI is a suitable complementary index for assessing relative body fat deposition of adult feral raccoons in Kanagawa Prefecture and may be generalizable to populations in other areas.  相似文献   
128.
To assess the relationship between pH and temperature in the ruminal bottom fluid, circadian changes were monitored using cows fed a control diet (C diet) or a rumen acidosis-inducing diet (RAI diet) by using a wireless radio-transmission pH- measurement system. These two parameters were measured simultaneously at 10-min intervals on day 14 after commencement of feeding. Compared to the mean ruminal pH for 60 min immediately after the morning feeding (0 hr), significantly lower pH was noted 3-13 hr later (P<0.05) and 4-19 hr later (P<0.01) in cows fed the C and RAI diets, respectively, although the reduction in the latter was much higher than that in the former. In contrast, significantly higher ruminal temperature was found at 8 and 12-14 hr later (P<0.05) and 6, 8, and 10-19 hr later (P<0.01) in cows fed the C and RAI diets, respectively. A significant negative correlation was observed between the lowest ruminal pH and its corresponding ruminal temperature in cows fed the C and RAI diets (r=-0.722 and -0.650, P<0.01, respectively), suggesting active fermentation and volatile fatty acid production in the rumen. However, ruminal pH profiles may not be predictable by measuring only ruminal temperature because decreases in ruminal pH were preceded by increases in ruminal temperature, and circadian changes in pH and temperature were associated with ruminal fermentation.  相似文献   
129.
Spontaneous progressive nephropathy dominated by glomerular lesions in common marmosets has been reported. However, the histopathologic characteristics, including the relationship between glomerular and tubulointerstitial lesions, have not been described in detail. In the present study, the authors examined the histopathologic characteristics of the background renal lesions in common marmosets (3 males and 9 females, 3 to 8 years old). The severity of glomerular lesions was graded into 3 classes: grade I, no alteration; grade II, hilar/focal increase of mesangial matrix; grade III, global/diffuse increase of mesangial matrix. Tubulointerstitial lesions (tubular regeneration and hyperplasia and interstitial inflammation and fibrosis) were scored according to the area of each lesion. The renal lesions were characterized by enlargement of glomeruli, expanded mesangial area with increase of periodic acid-Schiff reaction-positive matrix, tubular regeneration and hyperplasia, and interstitial inflammation and fibrosis. Glomerular lesions progressed with increasing mesangial matrix and aging. Additionally, the tubulointerstitial lesions became exacerbated with progressing glomerular lesions. Tubular hyperplasia was divided into 4 types according to the structure of the cell layer (simple or stratified-like), the area of increased lining cells (partial or entire), cytoplasmic staining (eosinophilic or basophilic), brush border and thickness of basement membrane, and the activity of cell proliferation. In conclusion, the background renal lesions in common marmosets were characterized by glomerular lesions with increase of mesangial matrix, which progressed with aging, and secondary tubulointerstitial lesions, including tubular hyperplasia. Those lesions were thus diagnosed as progressive glomerulonephropathy in common marmosets.  相似文献   
130.
The objectives of this study were to evaluate the effects of a diet (CALM CANINE) supplemented with alpha-casozepine and L-tryptophan on the stress response of anxious dogs with a focus on anxiety-related behavioral parameters and physiological parameters. Forty-four privately owned dogs were first fed with the control diet, followed by the study diet, each for an 8-week period, with a transitional period of 1 week between the diets. After 7 weeks on a particular diet, owners reported their dogs' behavior by filling out a questionnaire. Using the Canine Behavioral Assessment and Research Questionnaire, the effect of the study diet was found to be significant for 4 anxiety-related behavioral parameters, possibly mirroring a placebo effect. After 7 weeks on each diet, the urine cortisol-to-creatinine ratio (UCCR) was measured to assess the stress response to a visit to a veterinary practice for toenail clipping. UCCR was measured to complement the interpretation of behavioral data with regard to the stress susceptibility of the dogs. A positive correlation was found between baseline UCCR, as measured in the home situations, and poststressor UCCR. The stressor-induced increase was significantly lower in the dogs when they were fed the study diet than earlier when they were fed the control diet. The supplementation of casozepine or the proportion of protein in a given diet could have been a determining factor. The study diet seems to improve the ability of an individual to cope with stress and may reduce anxiety-related behavior in anxious dogs.  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