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   1485篇
  免费   125篇
  国内免费   2篇
林业   242篇
农学   71篇
基础科学   13篇
  358篇
综合类   93篇
农作物   111篇
水产渔业   117篇
畜牧兽医   417篇
园艺   48篇
植物保护   142篇
  2023年   15篇
  2022年   12篇
  2021年   27篇
  2020年   34篇
  2019年   38篇
  2018年   93篇
  2017年   84篇
  2016年   98篇
  2015年   49篇
  2014年   76篇
  2013年   85篇
  2012年   121篇
  2011年   123篇
  2010年   75篇
  2009年   69篇
  2008年   67篇
  2007年   62篇
  2006年   58篇
  2005年   59篇
  2004年   39篇
  2003年   47篇
  2002年   27篇
  2001年   26篇
  2000年   26篇
  1999年   22篇
  1998年   16篇
  1997年   7篇
  1996年   7篇
  1995年   6篇
  1994年   6篇
  1993年   5篇
  1990年   4篇
  1989年   6篇
  1988年   5篇
  1987年   5篇
  1986年   5篇
  1985年   6篇
  1984年   6篇
  1983年   6篇
  1982年   4篇
  1980年   6篇
  1979年   4篇
  1977年   4篇
  1974年   3篇
  1973年   4篇
  1972年   3篇
  1970年   3篇
  1969年   4篇
  1968年   5篇
  1966年   5篇
排序方式: 共有1612条查询结果,搜索用时 187 毫秒
11.
Inductively coupled plasma optical emission spectroscopy, in combination with calculation of various biological factors, was used in this study not only for a simple illustration of the present status of some essential and non-essential metals such as copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), arsenic (As), and cadmium (Cd) in the grapevine cultivar Rkatsiteli and wild blackberry from East Serbia but also for the estimation of plant bioaccumulation potentials. Great majority of detected metal concentrations were in normal ranges except in few cases: Zn concentrations were at the level of deficiency in almost all plant parts, and some Cu and As concentrations were at the levels that could be considered phytotoxic. Biological accumulation factors provided very informative data on metal accumulation and translocation in both plants and pointed to low accumulation rates of metals except in the case of Cu, Zn, and As in some wild blackberry tissues.  相似文献   
12.
本研究,我们以6个花生品种为亲本配置杂交组合,田间调查发现亲本间形态表型差异大的杂交F1容易鉴别真伪,而形态表型差异小的则难于鉴别,甚至无法鉴别。为此,我们通过改良Thomson一步法制备DNA模板,建立了一套花生SSR-PCR快速检测体系,并在此基础上利用SSR鉴别花生杂交F1真伪。结果表明,采用Thomson一步法和改良后的一步法提取的DNA模版均能扩展出清晰条带,但改良后制备的DNA模板在4℃下可保存约1个月,未改良的仅能保存一天。利用SSR检测上述群体表明,F1真杂种率为38%~56%,不同亲本间杂交成功率存在差异,同一亲本正反交成功率也存在一定差异。可见,SSR标记用于杂种真伪鉴定具有一定的应用潜力。  相似文献   
13.
Curcumin, a plant-derived polyphenolic compound, naturally present in turmeric (Curcuma longa), has been the subject of intensive investigations on account of its various activities. The implementation of safe, beneficial and highly functional compounds from natural sources in human nutrition/prevention/therapy requires some modifications in order to achieve their multi-functionality, improve their bioavailability and delivery strategies, with the main aim to enhance their effectiveness. The low aqueous solubility of curcumin, its rapid metabolism and elimination from the body, and consequently, poor bioavailability, constitute major obstacles to its application. The main objectives of this review are related to reported strategies to overcome these limitations and, thereby, improve the solubility, stability and bioavailability of curcumin. The effectiveness of curcumin could be greatly improved by using nanoparticle-based carriers. The significance of the quality of a substance delivery system is reflected in the fact that carrying curcumin as a food additive/nutrition also means carrying the active biological product/drug. This review summarizes the state of the art, and highlights some examples and the most significant advances in the field of curcumin research.  相似文献   
14.
Maize is arguably the most widely grown crop in the world, but it is often associated with one of its major insect pests, the European corn borer (ECB). The damage caused by this species to maize production is generally variable, but in many cases it is economically significant. This review paper provides an overview of the research findings on the natural plant defence mechanisms against ECB larvae published till now. What is resistance and how it is achieved, what is the chemical response of maize plants to insect feeding and how tolerance can be increased. A short introduction in breeding for resistance and a discussion if the mentioned traits can be used in conventional breeding in order to create maize hybrids less affected by ECB are given.  相似文献   
15.
Journal of Plant Diseases and Protection - The study assessed the genetic variability among Macrophomina phaseolina (Tassi) Goid. isolates originating from six different countries (Turkey,...  相似文献   
16.
Journal of Plant Diseases and Protection - Prior to the first occurrence of chestnut blight in 1976, leaf spot caused by Cylindrosporium castaneae was one of the most important diseases of European...  相似文献   
17.
The removal of the cyanobacterial peptide toxin microcystin-LR at 4 and 37 degrees C by six commercial probiotic strains and Lactobacillus plantarum strains IS-10506 and IS-20506 isolated from dadih, Indonesian traditional fermented milk, was assessed in this study. The aim was to evaluate the main factors influencing the viability and metabolic activity of the probiotic strains, as well as their capacity to remove microcystin-LR. Both L. plantarum strains isolated from dadih, as well as Bifidobacterium lactis strains Bb12 and 420, were shown to be more resistant, and >85% remained viable in phosphate-buffered saline (PBS) solution for 48 h of incubation at either temperature, while the viability of the other four commercial bacteria decreased markedly over time. The effect of glucose on viability and removal of toxin was shown to be a strain-specific and strain-dependent property, but in general, the efficiency of microcystin-LR removal increased when glucose was added to the solution. A maximum removal of 95% was observed for L. plantarum strain IS-20506 (37 degrees C, 10 (11) colony-forming units mL(-1)) with 1-2% glucose supplementation and 75% in PBS alone.  相似文献   
18.
Plant Foods for Human Nutrition - The purpose of this study was to compare the yield, chemical composition, antimicrobial and antioxidant properties of essential oils isolated from leaves of Laurus...  相似文献   
19.
Plant Foods for Human Nutrition - St. John’s wort has been used for centuries in traditional medicine of many cultures, and nowadays it is well-known as a clinically important antidepressant...  相似文献   
20.
Short basal internodes are important for lodging resistance of rice(Oryza sativa L.).Several canopy indices affect the elongation of basal internodes,but uncertainty as to the key factors determining elongation of basal internodes persists.The objectives of this study were(1)to identify key factors affecting the elongation of basal internodes and(2)to establish a quantitative relationship between basal internode length and canopy indices.An inbred rice cultivar,Yinjingruanzhan,was grown in two split-plot field experiments with three N rates(0,75,and 150 kg N ha−1 in early season and 0,90,and 180 kg N ha−1 in late season)as main plots,three seedling densities(16.7,75.0,and 187.5 seedlings m−2)as subplots,and three replications in the 2015 early and late seasons in Guangzhou,China.Light intensity at base of canopy(Lb),light quality as determined from red/far-red light ratio(R/FR),light transmission ratio(LTR),leaf area index(LAI),leaf N concentration(NLV)and final length of second internode(counted from soil surface upward)(FIL)were recorded.Higher N rate and seedling density resulted in significantly longer FIL.FIL was negatively correlated with Lb,LTR,and R/FR(P<0.01)and positively correlated with LAI(P<0.01),but not correlated with NLV(P>0.05).Stepwise linear regression analysis showed that FIL was strongly associated with Lb and LAI(R2=0.82).Heavy N application to pot-grown rice at the beginning of first internode elongation did not change FIL.We conclude that FIL is determined mainly by Lb and LAI at jointing stage.NLV has no direct effect on the elongation of basal internodes.N application indirectly affects FIL by changing LAI and light conditions in the rice canopy.Reducing LAI and improving canopy light transmission at jointing stage can shorten the basal internodes and increase the lodging resistance of rice.  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