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   637篇
  免费   16篇
  国内免费   1篇
林业   57篇
农学   11篇
  105篇
综合类   38篇
农作物   22篇
水产渔业   59篇
畜牧兽医   324篇
园艺   9篇
植物保护   29篇
  2022年   6篇
  2021年   24篇
  2020年   9篇
  2019年   13篇
  2018年   14篇
  2017年   10篇
  2016年   13篇
  2015年   31篇
  2014年   24篇
  2013年   45篇
  2012年   36篇
  2011年   42篇
  2010年   20篇
  2009年   19篇
  2008年   30篇
  2007年   29篇
  2006年   36篇
  2005年   28篇
  2004年   20篇
  2003年   21篇
  2002年   20篇
  2001年   25篇
  2000年   16篇
  1999年   7篇
  1998年   2篇
  1997年   3篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   6篇
  1991年   14篇
  1990年   8篇
  1989年   13篇
  1988年   15篇
  1987年   8篇
  1986年   7篇
  1985年   1篇
  1984年   10篇
  1983年   8篇
  1982年   3篇
  1981年   1篇
  1979年   4篇
  1978年   1篇
  1977年   1篇
  1971年   1篇
  1969年   1篇
  1968年   1篇
  1963年   1篇
  1961年   1篇
  1927年   1篇
排序方式: 共有654条查询结果,搜索用时 125 毫秒
31.
Bovine milk contains various immunoreactive components, and the activation of polymorphonuclear leukocytes (PMNLs) function in breast-fed infants has been reported. In this study, the effect of milk on the oxidative burst of bovine PMNLs was investigated in vitro. When PMNLs were incubated with 0.1% colostrum or normal milk, the oxidative burst induced by serum-opsonized Staphylococcus aureus was enhanced, and the enhancement declined dose-dependently. The enhancement of the oxidative burst by milk was not due to opsonins but the priming activities. Also, the phorbol 12-myristate 13-acetate (PMA)-induced oxidative burst increased after incubation with 0.1% colostrum, but the colostral enhancement of the oxidative burst was unaffected by the incubation time. These results suggest that bovine milk contains oxidative burst promoting factor(s).  相似文献   
32.
Primary cultures and cryopreservation procedure of bovine brain cells were established as in vitro experimental systems to study the responses of bovine brain cells to neuropathogenic agents. Brain cells were dissociated by papain from the cerebellum of a bovine fetus at 90 to 120 days old, and were cultured in different media. In a medium containing 1 per cent fetal bovine serum (FBS), neuronal cells were maintained and they formed clusters on glial and fibroblastic cell sheets. In a medium containing 10 per cent FBS, the proportion of neurones decreased, and fibroblastic and microglial cells dominated. In a serum-free medium containing epidermal growth factor, the highest neuronal proportion was obtained. Optimal cryopreservation condition for the brain tissues was investigated by changing the concentrations of DMSO and FBS. Brain cells could be cultured from cryopreserved tissue with only slightly reduced growth profiles and varying cell proportions in comparison to those prepared from fresh tissue.  相似文献   
33.
MRL/lpr mouse is an established animal model which develops autoimmune diseases including glomerulonephritis, sialoadenitis, hepatitis and inflammatory lung disease. Additionally, it has been reported that lpr strains uniquely accumulate CD3+ CD4- CD8- B220+ (double negative, DN) T cells in lymphoid organs leading to lymphadenopathy and splenomegaly. To investigate the role of CD28/CTLA4-B7 pathway in the development of lymphadenopathy and splenomegaly, MRL/lpr mice were treated with soluble form of CTLA4 molecules, CTLA4IgG, which efficiently blocks this pathway. It was demonstrated that (i) the development of DN T cells was independent of the CD28/CTLA4-B7 pathway, (ii) the CD28/CTLA4-B7 pathway was required for the development of lymphadenopathy and splenomegaly, (iii) the CD28/CTLA4-B7 pathway was important for the accumulation of various cell populations in the lymph node and spleen, (iv) composition of the accumulating cell populations was not altered by CTLA4IgG treatment, and (v) activation of conventional T cells and IL-4 production from conventional T cells were the CD28/CTLA4-B7 pathway dependent. Thus, we concluded that the CD28/CTLA4-B7 pathway was required for the development of full-blown lymphadenopathy and splenomegaly in MRL/lpr mice.  相似文献   
34.
To characterize factors affecting the number of bovine oocytes recovered transvaginally, a regression analysis was performed between the responsiveness to multiple-ovulation treatment and the number of oocytes recovered transvaginally. The number of embryos recovered following multiple-ovulation treatment and the number of oocytes recovered transvaginally increased when the number of follicles to be aspirated transvaginally increased (P<0.05. P<0.01). The number of cumulus-oocyte complexes recovered transvaginally also increased when the number of oocytes to be aspirated transvaginally increased (P<0.001). However, the number of viable embryos that recovered following multiple-ovulation treatment had no relation to the number of cumulus-oocyte complexes recovered transvaginally. These results suggested that more oocytes can be recovered from donors that have a high responsiveness to multiple-ovulation treatment.  相似文献   
35.
A soil drench of soluble silicon (liquid potassium silicate) was tested for the control of powdery mildew of strawberry in soil for 2 years in a vinyl house under growers' conditions on two cultivars: very susceptible Toyonoka and slightly susceptible Sachinoka. Soluble silicon suppressed the disease more effectively as a preventive control than as a control to reduce initial incidence. The suppressive effect against this disease was more effective for Toyonoka than for Sachinoka. The control value of soluble potassium silicate was 85.6% for Toyonoka in the first year and 60.2% in the second year, while for Sachinoka it was 58% in the first year and 40.6% in the second year. Strawberry leaf hardness was measured for the control and silicate-treated leaves. Although silicate-treated leaves seemed to be harder than control leaves, leaf hardness did not vary significantly between controls and silicate-treated leaves in either of the 2 years, and the mode of preventive action of liquid potassium silicate remains unknown. A factor other than a physical action may be involved.  相似文献   
36.
Effect of ethephon (2-chloroethylphosphonic acid) application on rabbiteye blueberry fruit quality during the growth period was investigated. Ethephon treatment stimulated the decrement of titratable acidity, anthocyanin accumulation and fruit softening 4 days after treatment and the promoting effects continued through the investigation period. The ripening promotion effect of ethephon on total soluble solids content was observed only 8 days after treatment. Ethephon treatment did not affect the fruit enlargement during the investigation period. From these results, it is concluded that ethephon application for rabbiteye blueberry promote the fruit ripening, but the stimulatory effects of ethephon on fruit ripening were different in degree on each ripening characters.  相似文献   
37.
A new monocyclic triterpene ester (1) was isolated from the rhizomes of Iris germanica from Turkey. Structure elucidation of compound (1) was carried out by the combined application of HMQC, HMBC, DEPT, COSY and NOESY experiments and named as iristectorone K.  相似文献   
38.
The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37–0.46) of the variation in dbh growth during a 5–11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09–0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50–0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.  相似文献   
39.
The technique of image analysis has been used to assess the quality of model oriented strand board panels by investigating the relationships between shape and size of strands, the distribution of strands and bending properties. A batch of commercial strands was analysed by image analysis and the distribution of the shape and size of strands was quantified. The strands were categorised into five strand types as a function of size and aspect ratio. In general, strand shapes were observed to be mostly rectangular and there was also a wide variation in strand dimensions in commercial material. Bigger area strands had low aspect ratios and small strands had high aspect ratios. Half of the commercial strands were longer than 100 mm.Model OSB panels were manufactured in the laboratory by hot pressing strand mats formed from each of the five strand types. Strands were laid up by hand into the forming mat and following pressing the orientation and shape of strands was evaluated by image analysis and the panels were tested in a three point bending. Large area (type 3) strands with high aspect ratios produced model panels with optimum strand orientation and mechanical properties.Type 3 panels were also fabricated from strands dropped through a slotted forming device in order to simulate the delivery of strands to the forming line under factory conditions. As the height of strand delivery increased from 0 to 100 to 200 mm the disorientation of strands in the pressed panels progressively increased and as a result mechanical properties in bending were reduced.Image analysis is therefore a powerful tool for evaluating the distribution of commercial strand shapes and the relationship between strand geometry, strand orientation and the mechanical properties of oriented strand board.  相似文献   
40.
Canine melanoma is one of the most important diseases in small animal medicine. Protein phosphatase 2A (PP2A), a well conserved serine/threonine phosphatase, plays a critical role as a tumor suppressor. SET/I2PP2A is an endogenous inhibitor for PP2A, which directly binds to PP2A and suppresses its phosphatase activity. Elevated SET protein levels have been reported to exacerbate human tumor progression. The role of SET in canine melanoma, however, has not been understood. Here, we investigated the potential therapeutic role for SET inhibitors in canine melanoma. The expression of SET protein was observed in 6 canine melanoma cell lines. We used CMeC-1 cells (primary origin) and CMeC-2 cells (metastatic origin) to generate cell lines stably expressing SET-targeting shRNAs. Knockdown of SET expression in CMeC-2, but not in CMeC-1, leads to decreased cell proliferation, invasion and colony formation. Phosphorylation level of p70 S6 kinase was decreased by SET knockdown in CMeC-2, suggesting the involvement of mTOR (mammalian target of rapamycin)/p70 S6 kinase signaling. The SET inhibitors, OP449 and FTY720, more effectively killed CMeC-2 than CMeC-1. We observed PP2A activation in CMeC-2 treated with OP449 and FTY720. These results demonstrated the potential therapeutic application of SET inhibitors for canine melanoma.  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