全文获取类型
收费全文 | 34792篇 |
免费 | 3056篇 |
国内免费 | 2968篇 |
专业分类
林业 | 4052篇 |
农学 | 4316篇 |
基础科学 | 2514篇 |
5685篇 | |
综合类 | 11675篇 |
农作物 | 2122篇 |
水产渔业 | 1434篇 |
畜牧兽医 | 5075篇 |
园艺 | 1599篇 |
植物保护 | 2344篇 |
出版年
2025年 | 8篇 |
2024年 | 500篇 |
2023年 | 605篇 |
2022年 | 1060篇 |
2021年 | 1490篇 |
2020年 | 1368篇 |
2019年 | 1281篇 |
2018年 | 942篇 |
2017年 | 1341篇 |
2016年 | 1194篇 |
2015年 | 1586篇 |
2014年 | 1519篇 |
2013年 | 1839篇 |
2012年 | 2357篇 |
2011年 | 2473篇 |
2010年 | 2365篇 |
2009年 | 2094篇 |
2008年 | 2071篇 |
2007年 | 2112篇 |
2006年 | 1920篇 |
2005年 | 1560篇 |
2004年 | 825篇 |
2003年 | 673篇 |
2002年 | 628篇 |
2001年 | 574篇 |
2000年 | 680篇 |
1999年 | 779篇 |
1998年 | 657篇 |
1997年 | 560篇 |
1996年 | 555篇 |
1995年 | 538篇 |
1994年 | 479篇 |
1993年 | 437篇 |
1992年 | 402篇 |
1991年 | 309篇 |
1990年 | 257篇 |
1989年 | 213篇 |
1988年 | 165篇 |
1987年 | 100篇 |
1986年 | 67篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1983年 | 37篇 |
1982年 | 18篇 |
1981年 | 28篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1974年 | 11篇 |
1963年 | 8篇 |
1956年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
W W Chan K Y Chen H Liu L S Wu J H Lin 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(10):1057-1062
Since the International Society of Veterinary Acupuncture (IVAS) was founded in 1974, acupuncture (AP) has received greater acceptance by veterinary professionals throughout the world. This article introduces some important animal diseases that respond well to AP therapy. These include resuscitation of small animals, treatment of anoestrous gilts and sows, bovine reproductive disease, canine vertebral problems and equine backpain, etc. Conventional medicine considers these to be difficult cases to treat. Veterinarians have become more aware of the benefits of AP especially for those diseases, thanks to the efforts of experienced practitioners and scientists, and the many published reports on veterinary AP that have introduced some good indications for AP therapy in veterinary practice. Possible mechanisms behind the effectiveness of AP are discussed. This article aims to introduce veterinarians to good indications for AP to initiate their interest in the practice of AP. Although this is a rapidly expanding field, a long march must begin with one step. We wish this article to be the shoes for such a march. For more information on veterinary AP, contact IVAS , P.O. Box 1478, Longmont, CO.. 80502, USA (http://www.ivas.org), or your national veterinary acupuncture society (http://www.komvet.at/ ivadkom/vapsocs.htm). 相似文献
2.
对N×特青示范田中试区与肥料试验田各处理小区稻株分析结果表明:抽穗后,亚种间杂交稻N×特青比常规稻特青干物质生产能力强,灌浆速度快;地上部各器官占植株干重比例,前者叶片比重大于茎,后者茎比重大于叶。亚种间杂交稻对肥料反应敏感,抽穗后,干物质累积,植株高度,每穗总粒数和粒重均随施肥量增加而增加,在高肥区有利于进一步提高产量,但增施氮肥后,灌浆速度明显滞后。 相似文献
3.
1,6-Hexamethylenediamine (HMDA) is utilized to synthesize copolyimides based on bisphenol-A dianhydride and 4,4-oxydianiline or 1,4-bis(4-aminophenoxy) benzene. The purpose of this study is to modify the processability of aromatic polyimides for textile processing and melt property requirements. Polyimides containing an aliphatic HMDA are synthesized via random and block copolymerizations. Variations in the aliphatic content produce a series of polyimides that have different thermal stability, mechanical properties, and processing characteristics. Based on the results, polyimides synthesized with 25 % HMDA have better mechanical properties compared to other contents of HMDA, and block copolyimides have better processability with higher melt index than random copolymers. 相似文献
4.
5.
6.
Yong Yu Yunwei Pang Haichao Zhao Xiaoling Xu ZhonghongWu Lei An Jianhui Tian 《畜牧与生物技术杂志(英文版)》2012,3(4):188-192
Background: Upon binding luteinizing hormone in the ovary, the luteinizing hormone/choriogonadotropin receptor (LHCGR) is necessary for follicular maturation and ovulation, as well as luteal function. We detected mutations in the LHCGR gene and evaluated their association with superovulation. Methods: Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing, we examined polymorphisms in LHCGR and the genotypes associated with superovulation traits in 127 Chinese Holstein heifers. Results: A G/T polymorphism (ss52050737) in exon 11 was significantly associated with the total number of ova and the number of transferable embryos. Conclusions: LHCGR may be a new predictor for superovulation in Chinese Holstein heifers. 相似文献
7.
乳牛口服过量维生素A对维生素D3及钙磷代谢的影响 总被引:9,自引:0,他引:9
从北京郊区某农场选取10头健康成年黑白花乳牛,随机分为试验(5头,每周每头口服维生素A100万单位)和对照(5头,不作任何处理)两组。8周以后检测发现,试验组血清钙和无机磷水平呈下降趋势;尾椎骨皮质变薄,密度下降,呈现骨质吸收现象;血清碱性磷酸酶显著下降(P<0.05);其活性代谢产物25-羟维生素D3(25-OH-D3)极显著下降(P<0.01);1,25-二羟维生素D3[1,25-(OH)2- 相似文献
8.
9.
J Kwang S Yang F A Osorio S Christian J G Wheeler K M Lager S Low L Chang A R Doster A White C C Wu 《Journal of veterinary diagnostic investigation》1999,11(5):391-395
The sensitivity and specificity of recombinant open reading frame 5 products used in the Western blotting assay for confirmation of porcine reproductive and respiratory syndrome virus (PRRSV) serologic status were evaluated. The recombinant antigen-based assays were specifically compared with a commercial enzyme-linked immunosorbent assay (ELISA) for PRRSV antibodies using 1) PRRSV antibody-negative reference sera (n = 30), 2) naturally infected pig sera (n = 40), 3) sequential sera obtained from 24 experimentally infected pigs, and 4) sera submitted to 3 state diagnostic laboratories (n = 200). The recombinant antigen assay yielded an average increased sensitivity of 10% over the commercial PRRSV ELISA. The negative controls (group 1 sera) showed no difference between the 2 assays. This comparison confirmed that the recombinant antigen-specific assay was more sensitive than the commercial ELISA and is well suited for routine confirmation of the presence of PRRSV antibodies. 相似文献
10.
达乌尔黄鼠肛腺组织解剖 总被引:1,自引:0,他引:1
达乌尔黄鼠Citellus dauricus具有三个肛腺,位于肛门与直肠之间的粘膜下层,肛腺深约6-7mm,三个肛腺的圆形开口呈倒三角形排列于肛周内侧,平时不现,在受外界剌激时。肛门外翻露出三个肛腺的开口。腺体由两种腺泡群组成:一种由大量的皮脂聚合而成,排列在肛囊底产;一种由大量的顶浆分泌型汗腺聚合而成,分布于皮脂腺群的外围。 相似文献