全文获取类型
收费全文 | 6940篇 |
免费 | 317篇 |
国内免费 | 828篇 |
专业分类
林业 | 909篇 |
农学 | 1143篇 |
基础科学 | 534篇 |
1227篇 | |
综合类 | 1950篇 |
农作物 | 429篇 |
水产渔业 | 312篇 |
畜牧兽医 | 846篇 |
园艺 | 216篇 |
植物保护 | 519篇 |
出版年
2024年 | 18篇 |
2023年 | 40篇 |
2022年 | 180篇 |
2021年 | 269篇 |
2020年 | 251篇 |
2019年 | 267篇 |
2018年 | 180篇 |
2017年 | 232篇 |
2016年 | 212篇 |
2015年 | 297篇 |
2014年 | 274篇 |
2013年 | 348篇 |
2012年 | 427篇 |
2011年 | 446篇 |
2010年 | 416篇 |
2009年 | 421篇 |
2008年 | 369篇 |
2007年 | 361篇 |
2006年 | 421篇 |
2005年 | 411篇 |
2004年 | 201篇 |
2003年 | 145篇 |
2002年 | 116篇 |
2001年 | 132篇 |
2000年 | 153篇 |
1999年 | 212篇 |
1998年 | 171篇 |
1997年 | 158篇 |
1996年 | 128篇 |
1995年 | 114篇 |
1994年 | 106篇 |
1993年 | 107篇 |
1992年 | 102篇 |
1991年 | 72篇 |
1990年 | 82篇 |
1989年 | 75篇 |
1988年 | 54篇 |
1987年 | 38篇 |
1986年 | 24篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
排序方式: 共有8085条查询结果,搜索用时 15 毫秒
111.
Huijuan Zhang Congxin Xie Dapeng Li Dongmei Xiong Haiping Liu Sizhu Suolang Peng Shang 《Fish physiology and biochemistry》2010,36(3):797-801
This study investigated the haematological and blood biochemical characteristics of Glyptosternum maculatum. The haematological and biochemical parameters were measured in 30 adult fish collected from Nyingchi Reach of Yarlung Zangbo
River in Tibet. The red blood cell count (RBC), haemoglobin concentration (Hb), haematocrit (Hct), erythrocyte osmotic fragility
(maxEof and minEof), the erythrocyte sedimentation rate, mean cell volume (MCV), mean cellular haemoglobin content (MCH),
and mean cell haemoglobin concentration (MCHC) were determined. Compared with other Siluriformes fishes, G. maculatum showed similar mean values for Hct, Hb, MCH, and MCHC and had slightly lower RBC and higher MCV. The biochemical parameters
were assayed including alanine aminotransferase, aspartate aminotransferase (AST), alkaline phosphatase, total protein, albumin,
globulin, albumin/globulin ratio, total bilirubin, direct bilirubin, urea, creatinine, glucose, total cholesterol, and triglyceride.
The result showed that the value of AST in G. maculatum was obviously higher than that in Rhamdia quelen as well as in Silurus merdionalis. 相似文献
112.
The present study was conducted to investigate the effects of sodium butyrate (SB) on the physical barrier function, pro‐inflammatory response and possible underlying mechanisms in the distal intestine (DI) of yellow drum when fed a high‐SBM diet. Three iso‐proteic and iso‐lipidic diets were formulated with fish meal (FM, the control), 45% fish meal protein replaced by SBM (SBM) and 45% fish meal protein replaced by SBM but supplemented with 0.15% SB (SBM + SB). Fish were fed twice daily for 10 weeks. Results indicated that SB supplementation significantly increased the specific growth rate (SGR) and feed efficiency ratio (FER) and methionine content of muscle when compared with those of fish fed the SBM diet (p < .05). The morphologic histology results showed that SB dramatically improved the physical barrier structure, characterized as increases of fold height (FH) and muscular thickness (MT) (p < .05). RT‐qPCR data were accordant with morphologic histology results, in which claudin 3, claudin 4 and occludin were increased while claudin 7 and myosin light chain kinase (MLCK) mRNA expression levels were decreased (p < .05). Sodium butyrate also exerted anti‐inflammatory function, which may be attributed to the suppression of nucleus p65 protein expression. Results suggest SB can be incorporated in high‐SBM diets to ameliorate the negative consequences of alternative dietary ingredients on yellow drum physiology. 相似文献
113.
为研究励珂健喷剂(主要成分:杨树花提取物)对10日龄内仔猪腹泻和免疫力的影响,将18头PIC母猪随机分成3组,每组6头,分别为蒸馏水组、土霉素组和励珂健喷剂组,蒸馏水组仔猪1、3、5日龄时皮肤喷洒蒸馏水1 m L/头/d,土霉素组仔猪3、7日龄时分别肌肉注射20%长效土霉素注射液0.2 m L/头/d、0.5m L/头/d,励珂健喷剂组仔猪1、3、5日龄时皮肤喷洒励珂健喷剂1 m L/头/d。结果表明,励珂健喷剂可有效降低10日龄内仔猪的腹泻率和发病率,且励珂健喷剂组腹泻仔猪的治愈速度快于土霉素组和蒸馏水组。由此证明:励珂健喷剂对10日龄内仔猪腹泻有防治作用,并且还可以增强仔猪的免疫力。 相似文献
114.
利用ISSR技术对香蕉30个品种的遗传多态性进行了分析。从60个随机引物中筛选出8个多态性引物,共扩增出54条DNA带,其中44条为多态性带,占81.5%,平均每个引物扩增的DNA带数为6.75条。按照相同迁移位上有扩增带记为1、无带为0的方法构建ISSR表型数据矩阵,用MEGA2.0软件对香蕉30个品种进行UPGMA聚类分析,计算出30个品种间的平均距离系数为0.313,并在此基础上建立了聚类分析树状图,将香蕉30个品种划分为A、B、C、D4大聚类组。 相似文献
115.
Effects of stocking density, diet, and water exchange on growth and survival of pearl oyster Pinctada maxima larvae 总被引:1,自引:0,他引:1
Three experiments were carried out to separately investigate the effects of stocking density (1.0, 2.0, 4.0 and 8.0 larvae ml?1), diet (Isochrysis zhanjiangensis, Chlorella spp., Nannochloropsis oculata, 50 % I. zhanjiangensis/50 % Chlorella spp. and 50 % I. zhanjiangensis/50 % N. oculata), and water exchange (25 % once every other day and 25, 50 and 100 % once daily) on growth and survival of pearl oyster Pinctada maxima larvae. Results showed that there existed significant effects of stocking density, diet, and water exchange on the growth of pearl oyster larvae (P < 0.05). Larval survival was significantly affected by stocking density and diet (P < 0.05), but not by water exchange (P > 0.05). Larval growth decreased significantly with increasing stocking density (P < 0.05). A density of 1.0–4.0 larvae ml?1 was optimal for larval growth of pearl oyster. Chlorella spp. and N. oculata could replace 50 % of I. zhanjiangensis as a food source for the pearl oyster larvae without affecting growth and survival. A water exchange of 25 % once daily provided optimum larval growth and survival. 相似文献
116.
117.
118.
Changsheng Chen Chaotian Xie Dehua Ji Yan Liang Lingmin Zhao 《Aquaculture International》2010,18(6):1045-1060
To select a reliable and sensitive method for discriminating strains of Porphyra haitanensis, the nucleotide sequence of the internal transcribed spacer 1 to internal transcribed spacer 2 regions (ITS-5.8S) of nuclear ribosomal DNA and the intergenic spacer region of RUBISCO were compared in five wild and five cultivated Porphyra haitanensis strains. Based on molecular analyses, sequences of ITS-5.8S (about 1,210 bp) could be divided into three regions: ITS1, 5.8S, and ITS2. The ITS1 and ITS2 sequences of each strain differed, even between individuals collected from the same site. In contrast, 5.8S rDNA and RUBISCO spacer sequences were identical among the ten P. haitanensis strains, although differences were found among different Porphyra species. Phylogenetic analysis also supported these conclusions. These sequence features of highly conserved regions and diversified regions that occurred repeatedly in ITS-5.8S could be useful in discriminating germplasm of P. haitanensis strains or Porphyra species. In contrast, the RUBISCO spacer is only suitable for identifying Porphyra species. New coupled primers were designed to amplify only the 5.8S rDNA and ITS2 region of Porphyra. The sequences of these amplified fragments can be readily used to identify germplasm or to perform phylogenetic analysis of Porphyra spp. 相似文献
119.
选用巴斯德毕赤酵母(Pichia pastoris)系统表达特异性抗速灭威单链抗体(scFv)基因,以为速灭威特异性抗体的大量制备奠定基础。设计引物扩增阳性克隆scFv基因,亚克隆至表达载体pPICZαC,获得重组酵母表达质粒pPICZαC-scFv,线性化pPICZαC-scFv并高效电转P.pastoris(X-33),对转化子进行抗性梯度筛选得到一株高效表达的X-33-Pp-SMW-12-6菌株。对获得的菌株先后进行表达条件的优化、优化条件下的诱导表达及单链抗体性质研究。结果表明:P.pastoris-scFv的质量接近其亲本E.coli-scFv的质量,X-33-Pp-SMW12-6在优化条件下的表达产量达28mg/L,比未优化前的产量提高了约8mg/L,经纯化后抗体纯度可达85%以上。因此,利用P.pastoris表达系统制备抗速灭威单链抗体比细菌表达系统更有效、更经济。 相似文献
120.