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   355篇
  免费   12篇
  国内免费   16篇
林业   12篇
农学   15篇
基础科学   5篇
  109篇
综合类   78篇
农作物   59篇
水产渔业   35篇
畜牧兽医   40篇
园艺   6篇
植物保护   24篇
  2024年   3篇
  2023年   4篇
  2022年   3篇
  2021年   7篇
  2020年   8篇
  2019年   12篇
  2018年   6篇
  2017年   12篇
  2016年   9篇
  2015年   13篇
  2014年   21篇
  2013年   17篇
  2012年   27篇
  2011年   46篇
  2010年   12篇
  2009年   13篇
  2008年   25篇
  2007年   25篇
  2006年   16篇
  2005年   14篇
  2004年   9篇
  2003年   14篇
  2002年   5篇
  2001年   5篇
  2000年   7篇
  1999年   4篇
  1998年   1篇
  1997年   1篇
  1996年   4篇
  1995年   1篇
  1991年   3篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1985年   4篇
  1981年   1篇
  1979年   3篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1974年   3篇
  1971年   1篇
  1970年   2篇
  1969年   3篇
  1968年   1篇
  1965年   1篇
  1963年   4篇
排序方式: 共有383条查询结果,搜索用时 15 毫秒
1.
2.
Huang  B.  Kuo  S.  Bembenek  R. 《Water, air, and soil pollution》2004,158(1):37-51
Although evaluations of the availability of cadmium (Cd) contaminants in phosphate fertilizers have been made, few have examined the transfer efficiency of Cd from fertilizers to plants, especially under field conditions. This 2-year field study determined the transfer of added Cd to lettuce (Lactuca sativa L.) (Royal Green) from a western phosphate rock (PR) and a triple superphosphate (TSP) as affected by liming and rate of fertilizer (or Cd) input. A readily soluble Cd salt, CdCl2, was included in the study for comparison. The cumulative amounts of Cd added from the fertilizers and CdCl2 over the 2-year period ranged from 0 to 1440 g ha–1. Lettuce yield increased with increasing TSP rates, but was unaffected by PR. Significant (P < 0.01) effects of Cd source and rate, lime, and year were found on Cd accumulation by lettuce. The transfer of the added Cd was consistently higher for CdCl2 than for the fertilizers regardless of lime rate. A contrasting year effect was also found between the two P fertilizers. In the second year of application, the Cd transfer efficiency increased in the soil treated with the PR, but decreased in the soil treated with the TSP. The Cd transfer efficiency for the plant was better measured with DTPA–Cd (r 2= 0.78 – 0.80) or CaCl2–Cd (r 2= 0.57 – 0.76) than with soil total Cd (r 2= 0.39 to 0.54) across all Cd sources and lime rates. This is because DTPA–Cd or CaCl2–Cd reflected the influences of the amount of Cd added, Cd source, and lime rate on Cd accumulation by the plant better than did the soil total Cd. Of the amount of Cd added from the fertilizers an average of 1.0% or less was accumulated in the harvested lettuce tissue. Applications of the fertilizers at high rates could result in increased Cd accumulation in the soil over time.  相似文献   
3.
 Taiwania (Taiwania cryptomerioides Hayata), native to Taiwan, is one of the most economically important tree species grown there. In this article we summarize the current results of phytochemistry and bioactivity of Taiwania extracts, including antifungal, antitermite, antibacterial, and antimite activities as well as cytotoxicity against three tumor cells. The resources of Taiwania are also addressed. Received: January 23, 2002 / Accepted: March 8, 2002 Acknowledgment The authors thank the National Science Council of R.O.C. for financial support (NSC-90-2313-B-002-344). Correspondence to:S.-T. Chang  相似文献   
4.
3个单倍体诱导系的初步评价   总被引:2,自引:0,他引:2  
为了评价3个诱导系,将诱导系与6个玉米组合杂交,分析了初步诱导率。结果表明:诱导系间的初步诱导率存在显著差异;美诱系的初步诱导率(6.52%)显著高于日诱系(3.89%)和高诱1号(3.21%);基础组合间的初步诱导率差异不显著。  相似文献   
5.
6.
The CpG motif within bacterial DNA is a potent immuno-stimulatory moiety. Here, using a 2-D electrophoretic approach, we investigated the effect of synthetic oligodeoxynucleotide containing a B type CpG motif (CpG-B ODN) on the protein expression profile of swine peripheral blood mononuclear cells (PBMC). We found that several proteins including spondin 1, N-acetolactate alpha linked acidic dipeptidase; V kappa light chain, T cell receptor variable alpha chain, heat shock protein (Hsp) 60, Hsp70, KIAA0857 protein, and PNAS-146 were up-regulated in PBMC by CpG-B ODN stimulation. Further studies showed that CpG-B ODN-mediated Hsp60, Hsp70 and Hsp90 expressions were closely associated with the TLR9 signalling pathway. Pretreatment with inhibitors of Hsp70, Hsp90 and TLR9 all blocked the CpG-B ODN-mediated anti-apoptotic effect in swine PBMC. These results suggest that CpG-B ODN treatment of swine PBMC may enhance the expression of biologically active proteins, notably spondin 1, V kappa light chain, T cell receptor variable alpha chain and Hsps, which may play an important role in CpG-B ODN-mediated activation of immune responses and enhancement of swine PBMC survival.  相似文献   
7.
鲈鱼与养生     
在广泛文献检索基础上,对鲈鱼的种属、营养成分、养生价值、代表性膳食及食用注意事项进行了概述,以期为全民养生保健提供科学资料。  相似文献   
8.
以水解度和α-葡萄糖苷酶抑制率为评价指标,确定双酶复合水解罗非鱼下脚料的方案,并通过单因素试验和正交试验进行优化,最后得到最适酶解工艺参数为先在碱性蛋白酶在温度50℃,加酶量10000 U/g,pH值9.5,底物质量分数6%条件下水解;再在胰蛋白酶在温度37℃,加酶量10000 U/g,pH值8条件下水解100 min。此工艺条件下罗非鱼下脚料水解度、水解产物的α-葡萄糖苷酶抑制率分别为48.26%和41.46%。  相似文献   
9.
The orphan G protein-coupled receptor (GPCR) GPR124/tumor endothelial marker 5 is highly expressed in central nervous system (CNS) endothelium. Here, we show that complete null or endothelial-specific GPR124 deletion resulted in embryonic lethality from CNS-specific angiogenesis arrest in forebrain and neural tube. Conversely, GPR124 overexpression throughout all adult vascular beds produced CNS-specific hyperproliferative vascular malformations. In vivo, GPR124 functioned cell-autonomously in endothelium to regulate sprouting, migration, and developmental expression of the blood-brain barrier marker Glut1, whereas in vitro, GPR124 mediated Cdc42-dependent directional migration to forebrain-derived, vascular endothelial growth factor-independent cues. Our results demonstrate CNS-specific angiogenesis regulation by an endothelial receptor and illuminate functions of the poorly understood adhesion GPCR subfamily. Further, the functional tropism of GPR124 marks this receptor as a therapeutic target for CNS-related vascular pathologies.  相似文献   
10.
Most multi-purpose water resources have been planned and constructed by governments in Taiwan to meet the water demands of different users. However, economic and solvency differences among parties using water create conflicts regarding the reasonable and equitable allocation of investment and operational costs. The Chi-Chi Weir in Nantou County, which was completed in 2002, meets the high water demand of residents and the needs of industrial growth in central Taiwan. Thus, multi-purpose water reservoirs are designed to serve agriculture, the public and industry. Three analytical methods, the quantity-based method, marginal cost method, and separable cost remaining benefit method (SCRB), are employed to compare the cost allocation for different parties using water. The quantity-based method indicates that proportional costs allocated to agriculture, the public, industry and new irrigated areas are 88.02, 3.63, 7.86, and 0.49%, respectively. Via the marginal cost method, the proportional costs allocated to agriculture, the public, hydropower, industry and new irrigated areas are 68.44, 2.51, 28.71, and 0.34%, respectively. The marginal cost price of water is NT$ 2.97 ton−1; industrial use has the highest price. Based on the SCRB method, the proportional costs allocated to agriculture, the public, hydropower, and new irrigated areas are 18.2, 22.2, 51.8, 4.8, and 2.9%, respectively.  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