全文获取类型
收费全文 | 5321篇 |
免费 | 309篇 |
国内免费 | 4篇 |
专业分类
林业 | 269篇 |
农学 | 244篇 |
基础科学 | 9篇 |
1003篇 | |
综合类 | 613篇 |
农作物 | 587篇 |
水产渔业 | 424篇 |
畜牧兽医 | 2080篇 |
园艺 | 74篇 |
植物保护 | 331篇 |
出版年
2023年 | 29篇 |
2022年 | 89篇 |
2021年 | 116篇 |
2020年 | 97篇 |
2019年 | 107篇 |
2018年 | 139篇 |
2017年 | 160篇 |
2016年 | 184篇 |
2015年 | 165篇 |
2014年 | 199篇 |
2013年 | 290篇 |
2012年 | 350篇 |
2011年 | 418篇 |
2010年 | 224篇 |
2009年 | 221篇 |
2008年 | 314篇 |
2007年 | 301篇 |
2006年 | 269篇 |
2005年 | 248篇 |
2004年 | 232篇 |
2003年 | 189篇 |
2002年 | 203篇 |
2001年 | 144篇 |
2000年 | 119篇 |
1999年 | 77篇 |
1998年 | 35篇 |
1997年 | 18篇 |
1996年 | 21篇 |
1995年 | 21篇 |
1993年 | 22篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 38篇 |
1988年 | 31篇 |
1987年 | 40篇 |
1986年 | 18篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1978年 | 21篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1975年 | 14篇 |
1974年 | 20篇 |
1973年 | 22篇 |
1972年 | 22篇 |
1971年 | 15篇 |
排序方式: 共有5634条查询结果,搜索用时 15 毫秒
31.
Pedro ?M.?DominguesEmail author Paul?F. ?Dimarco Jose? P.?Andrade Phillip?G.?Lee 《Aquaculture International》2005,13(5):423-440
The effects of artificial diets on growth and body condition of adult cuttlefish, Sepia officinalis were tested in two experiments. Supplemented prepared diets (fish myofibrillar protein concentrate) were fed during a 30-day and a 21-day experiments. Growth, feeding rate and food conversion of group-reared cuttlefish were analyzed. The first of these experiments tested four artificial diets, made with increasing levels of lysine, on adult cuttlefish. According to the chemical analysis, diets 1–3 had limiting concentrations of lysine and other essential amino acids (compared to mantle composition of the cuttlefish), while diet 4 was the only one where almost all essential amino acids were present in concentrations similar or higher than the ones present in cuttlefish mantle. A second experiment was conducted by isolating 16 adult cuttlefish individually, and feeding them the same four artificial diets, in order to obtain individual data. During Experiment 1, only the diet with the best chemical score (diet 4) produced growth (p < 0.05), with a mean instantaneous growth rate (MIGR) of 0.30% wet body weight (BW) d−1. Similarly, individually reared cuttlefish fed diet 4 produced the highest IGR’s (0.26, 0.38 and 0.48% BW d−1) and grew larger (p < 0.01). Comparison of cuttlefish fed the artificial diets vs. thawed shrimp and unfed cuttlefish indicated that cuttlefish fed the artificial diets were in an intermediate state. Growth rates obtained with the artificial diets (<0.4% BW d−1) were considerably lower compared to natural prey, live or frozen, reported by other authors. 相似文献
32.
2020年2月份山西某大型规模猪场育肥猪突发呼吸困难,无过多症状表现,即突然死亡,发病率为2%,死亡率1.5%左右。实验室以病死猪为研究对象,综合死亡猪只脏器病变状况观察,无菌采集病死猪的肺脏、肝脏、脾脏病料,进行RT-PCR检测猪蓝耳病原;用含1%NAD和5%胎牛血清的TSA琼脂培养基进行细菌分离培养和纯化,经形态学鉴定、PCR鉴定、16Sr RNA基因序列进化树构建等方法,结果显示:该发病猪群为猪繁殖与呼吸障碍综合征并发猪胸膜肺炎放线杆菌感染。药敏试验结果显示:该猪胸膜肺炎放线杆菌对安普霉素、硫酸黏菌素、替米考星+氟苯尼考、替米考星+阿莫西林、氟苯尼考、头孢噻呋钠+硫酸黏菌素、头孢喹肟、头孢噻呋钠+新霉素、替米考星+头孢噻呋钠、多西环素+氟苯尼考、头孢噻呋钠+阿莫西林、阿莫西林+克拉维酸钾、头孢噻呋钠+恩诺沙星、新霉素、头孢噻呋钠、安普霉素+头孢噻呋钠敏感。对恩诺沙星耐药。本实验室根据临床及检测结果制定治疗方案,为该猪场的猪繁殖与呼吸障碍综合征并发猪胸膜肺炎的临床诊断及用药提供了理论依据。 相似文献
33.
Hillenmeyer ME Fung E Wildenhain J Pierce SE Hoon S Lee W Proctor M St Onge RP Tyers M Koller D Altman RB Davis RW Nislow C Giaever G 《Science (New York, N.Y.)》2008,320(5874):362-365
Genetics aims to understand the relation between genotype and phenotype. However, because complete deletion of most yeast genes ( approximately 80%) has no obvious phenotypic consequence in rich medium, it is difficult to study their functions. To uncover phenotypes for this nonessential fraction of the genome, we performed 1144 chemical genomic assays on the yeast whole-genome heterozygous and homozygous deletion collections and quantified the growth fitness of each deletion strain in the presence of chemical or environmental stress conditions. We found that 97% of gene deletions exhibited a measurable growth phenotype, suggesting that nearly all genes are essential for optimal growth in at least one condition. 相似文献
34.
Food safety is one of the major concerns in every country regardless of the economic and social development. The frequent occurrence of food scandals in the world has led the Chinese government to implement several strategies to fortify the food supply system to a high food safety standard. This relies heavily on laboratory testing services but conventional methods for detection of food contaminants and toxicants are limited by sophisticated sample preparation procedures,long analysis time,large instruments and professional personnel to meet the increasing demands. In this review,we have incorporated most of the current and potential rapid detection methods for many notorious food contaminants and toxicants including microbial agents,toxic ions,pesticides,veterinary drugs and preservatives,as well as detection of genetically modified food genes and adulterated edible oil. Development of rapid,accurate,easy-to-use and affordable testing methods could urge food handlers and the public to actively screen for food contaminants and toxicants instead of passively relying on monitoring by the government examination facility. This review also provides several recommendations including how to encourage the public to engage in the food safety management system and provide optimal education and financial assistance that may improve the current Chinese food safety control system. 相似文献
35.
Canopy cover (CC) is a good predictor variable for plant growth parameters such as leaf area index and aboveground biomass.
A nondestructive, low-cost, and convenient method is presented for estimating CC using digital camera image analysis. CC was
estimated by the ratio of plant pixels to total pixels of digital camera image of rice field. To determine the criteria for
segmenting the rice plant from variable soil background, three mosaic images for rice plant, flooded/bare soil, and algae-infested
background were prepared from digital camera images that were taken in various field conditions. An image analysis program
was developed in Visual Basic to extract red, green, and blue (RGB) features from the mosaic images, calculate RGB-based color
indices, and compute the minimum segmentation error for separating rice plant from background. When judged by the segmentation
error, modified excessive green index (MEGI) showed the highest potential for segmenting rice plant from flooded/bare soil
background, followed by normalized green (g) and excessive green index (EGI). At the threshold MEGI value of 0.03, the segmentation
error was the lowest as 0.13%. Any single index considered was not satisfactory in segmenting rice plant from algae-infested
background. However, a discriminant function of 1.2553EGI + 0.01735G − 0.01474B was successful in segmenting rice plant from
flooded/bare soil and algaeinfested background with segmentation errors of 0.34 and 1.17%, respectively. CC for four rice
varieties from tillering to booting stage was estimated based on the threshold value of MEGI and discriminant function and
also manually using commercial software. Both estimates of CC showed good relationship of r2 = 0.94, suggesting that a digital camera could be used efficiently for measuring the CC of rice field. 相似文献
36.
Narongrit Sombatsompop Nongyao Premkamolnetr Teerasak Markpin Santi Ittiritmeechai Chatree Wongkaew Wutthisit Yochai Preeyanuch Ratchatahirun Lee Inn Beng 《Asia Pacific viewpoint》2011,52(2):207-218
This opinion article expresses two key viewpoints regarding the options for Association of South‐East Asian Nations (ASEAN) universities in pursuit of fulfilling the demand for greater research visibility and academic reputation. The first viewpoint outlines the importance of promoting research collaboration among ASEAN researchers and their international peers in increasing the visibility and impact of ASEAN research. The second viewpoint examines the ASEAN research characteristics, the challenges and existing best practices of its journal publishing landscape, the potential role of non‐ASEAN international journals in improving the profile of ASEAN research and explores the needs and benefits of establishing an ASEAN Integrated Journal Publishing Network (IJPN). It is through these combined approaches, we believe, that effective policy change, the standardisation of publishing structure, procedures, and systems to drive journal development, improvement of journal quality, and establishment of a consistent framework for measuring researcher performance will result. This article also includes a proposal for the IJPN structure and implementation plan, and highlights the key benefits of taking a collaborative approach to achieving this common goal. 相似文献
37.
Weng AP Ferrando AA Lee W Morris JP Silverman LB Sanchez-Irizarry C Blacklow SC Look AT Aster JC 《Science (New York, N.Y.)》2004,306(5694):269-271
Very rare cases of human T cell acute lymphoblastic leukemia (T-ALL) harbor chromosomal translocations that involve NOTCH1, a gene encoding a transmembrane receptor that regulates normal T cell development. Here, we report that more than 50% of human T-ALLs, including tumors from all major molecular oncogenic subtypes, have activating mutations that involve the extracellular heterodimerization domain and/or the C-terminal PEST domain of NOTCH1. These findings greatly expand the role of activated NOTCH1 in the molecular pathogenesis of human T-ALL and provide a strong rationale for targeted therapies that interfere with NOTCH signaling. 相似文献
38.
39.
40.
Jundae Lee Jae Bok Yoon Jung-Heon Han Won Phil Lee Sang Hoon Kim Hyo Guen Park 《Euphytica》2010,173(1):55-61
Genic male sterility (GMS) has long been used as a tool for hybrid seed production in chili pepper (Capsicum annuum L.). We developed DNA markers linked to the GMS ms
3
gene in a segregating population using bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP)
techniques. The segregating population was subjected to BSA-AFLP with 512 primer combinations. Three AFLP markers (Eagg/Mccc276, Eagc/Mctt178, and Ecag/Mtgc204) were identified as tightly linked to the ms
3
locus. Among them, we converted the AFLP marker Ecag/Mtgc204 to the cleavage amplified polymorphic sequence (CAPS) marker, named GMS3-CAPS, based on sequencing analysis of internal and
flanking regions for the markers between male-fertile and sterile plants. This marker will be useful for pepper breeding using
the GMS system. 相似文献