全文获取类型
收费全文 | 9610篇 |
免费 | 626篇 |
国内免费 | 937篇 |
学科分类
农业科学 | 11173篇 |
出版年
2024年 | 12篇 |
2023年 | 117篇 |
2022年 | 146篇 |
2021年 | 224篇 |
2020年 | 211篇 |
2019年 | 253篇 |
2018年 | 198篇 |
2017年 | 337篇 |
2016年 | 444篇 |
2015年 | 381篇 |
2014年 | 333篇 |
2013年 | 492篇 |
2012年 | 763篇 |
2011年 | 539篇 |
2010年 | 518篇 |
2009年 | 532篇 |
2008年 | 558篇 |
2007年 | 713篇 |
2006年 | 656篇 |
2005年 | 551篇 |
2004年 | 464篇 |
2003年 | 334篇 |
2002年 | 290篇 |
2001年 | 252篇 |
2000年 | 217篇 |
1999年 | 176篇 |
1998年 | 177篇 |
1997年 | 176篇 |
1996年 | 139篇 |
1995年 | 145篇 |
1994年 | 94篇 |
1993年 | 136篇 |
1992年 | 129篇 |
1991年 | 91篇 |
1990年 | 82篇 |
1989年 | 70篇 |
1988年 | 56篇 |
1987年 | 30篇 |
1986年 | 68篇 |
1985年 | 30篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1956年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
52.
Bhuminad DEVKOTA Masahiro TAKAHASHI Saori SATO Kouya SASAKI Atsushi UEKI Takeshi OSAWA Masahiro TAKAHASHI Norio YAMAGISHI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(7):875-878
Blood samples were obtained sequentially from 10 dairy cows around the time of
parturition to assess plasma fluctuations in estradiol-17β (E2) levels in
association with those of several bone resorption markers. Plasma E2
concentration increased sharply a few days prepartum and decreased quickly after
parturition. In terms of bone resorption markers, the plasma level of tartrate-resistant
acid phosphatase isoform 5b (TRAP5b) rose significantly, commencing 1 week prepartum, and
was maintained at this level to a few days postpartum. The plasma concentration of
carboxyterminal collagen cross-links of type-I collagen (CTx) increased significantly
after parturition. These observations suggest that osteoclast-mediated bone resorption was
activated after parturition when plasma E2 concentrations decreased. 相似文献
53.
H. Titmarsh A.G. Gow S. Kilpatrick J. Sinclair T. Hill E. Milne A. Philbey J. Berry I. Handel R.J. Mellanby 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2015,29(6):1473-1478
Background
Dogs with a chronic enteropathy (CE) have a lower vitamin D status, than do healthy dogs. Vitamin D status has been associated with a negative clinical outcome in humans with inflammatory bowel disease.Objectives
To examine the relationship between serum 25 hydroxyvitamin D (25(OH)D) concentrations at diagnosis and clinical outcome in dogs with a CE.Animals
Forty‐one dogs diagnosed with CE admitted to the Royal Dick School of Veterinary Studies, Hospital for Small Animals between 2007 and 2013.Methods
Retrospective review. Serum 25(OH)D concentrations were compared between dogs which were alive at follow up or had died because of non‐CE‐related reasons (survivors) and dogs which died or were euthanized due to their CE (non‐survivors). A binary logistic regression analysis was performed to determine significant predictors of death in dogs with CE.Results
Serum concentrations of 25(OH)D at the time a CE was diagnosed were significantly lower in nonsurvivors (n = 15) (median nonsurvivors 4.36 ng/mL, interquartile range 1.6–17.0 ng/mL), median survivors (n = 26) (24.9 ng/mL interquartile range 15.63–39.45 ng/mL, P < .001). Serum 25(OH)D concentration was a significant predictor of death in dogs with CE (odds ratio 1.08 [95% CI 1.02–1.18)]).Conclusions
Serum 25(OH)D concentrations at diagnosis are predictive of outcome in dogs with CE. The role of vitamin D in the initiation and outcome of chronic enteropathies in dogs is deserving of further study. 相似文献54.
Jin-Gu NO Mi-Kyung CHOI Dae-Jin KWON Jae Gyu YOO Byoung-Chul YANG Jin-Ki PARK Dong-Hoon KIM 《The Journal of reproduction and development》2015,61(2):90-98
Pretreatment of somatic cells with undifferentiated cell extracts, such as embryonic stem cells and mammalian oocytes, is an attractive alternative method for reprogramming control. The properties of induced pluripotent stem cells (iPSCs) are similar to those of embryonic stem cells; however, no studies have reported somatic cell nuclear reprogramming using iPSC extracts. Therefore, this study aimed to evaluate the effects of porcine iPSC extracts treatment on porcine ear fibroblasts and early development of porcine cloned embryos produced from porcine ear skin fibroblasts pretreated with the porcine iPSC extracts. The ChariotTM reagent system was used to deliver the iPSC extracts into cultured porcine ear skin fibroblasts. The iPSC extracts-treated cells (iPSC-treated cells) were cultured for 3 days and used for analyzing histone modification and somatic cell nuclear transfer. Compared to the results for nontreated cells, the trimethylation status of histone H3
lysine residue 9 (H3K9) in the iPSC-treated cells significantly decreased. The expression of Jmjd2b, the H3K9 trimethylation-specific demethylase gene, significantly increased in the iPSC-treated cells; conversely, the expression of the proapoptotic genes, Bax and p53, significantly decreased. When the iPSC-treated cells were transferred into enucleated porcine oocytes, no differences were observed in blastocyst development and total cell number in blastocysts compared with the results for control cells. However, H3K9 trimethylation of pronuclear-stage-cloned embryos significantly decreased in the iPSC-treated cells. Additionally, Bax and p53 gene expression in the blastocysts was significantly lower in iPSC-treated cells than in control cells. To our knowledge, this study is the first to show that an extracts of porcine iPSCs can affect histone modification and gene expression in porcine ear
skin fibroblasts and cloned embryos. 相似文献
55.
Weak activity of UDP-glucuronosyltransferase toward Bisphenol analogs in
mouse perinatal development
Risa YABUSAKI Hidetomo IWANO Sumito TSUSHIMA Nanako KOIKE Naoko OHTANI Kentaro TANEMURA Hiroki INOUE Hiroshi YOKOTA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(11):1479-1484
Bisphenol A (BPA) is a widely used industrial chemical that disrupts endocrine function.
BPA is an endocrine disrupting chemical (EDC) that has been demonstrated to affect
reproductive organ development, brain development, metabolic disease and post-natal
behavior. Accordingly, Bisphenol analogs, Bisphenol F (BPF, bis (4-hydroxyphenyl) methane)
and Bisphenol AF (BPAF, 4,4-hexafluoroisopropylidene) diphenol) are used as replacements
for BPA. BPA is mainly metabolized by UDP-glucuronosyltransferase (UGT), UGT2B1, but this
effective metabolizing system is weak in the fetus. In the present study, we demonstrated
that hepatic UGT activity toward BPAF was very weak, in comparison with BPA and BPF, in
the fetus, pups and dams. Conversely, hepatic UGT activity toward BPF was very weak in the
fetus and newborn pups, and was increased to the same level as BPA post-partum. In
conclusion, BPAF possibly tends to accumulate in the fetus, because of weak metabolism
during the perinatal period, suggesting that the metabolism of individual Bisphenol
analogs requires assessment to properly gauge their risks. 相似文献
56.
Weidong SUN Xu YANG Hengbin QIU Di ZHANG Huanan WANG Jian HUANG Degui LIN 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(11):1541-1543
The BRCA1 gene plays an important role in the development of human breast
cancer, and recent research indicated that genetic variations of BRCA1 are also related to
canine mammary tumors (CMTs). Here, using rapid amplification of cDNA ends (RACE), we
cloned the 5′- and 3′-UTRs of BRCA1. By direct sequencing of the flanking sequences of the
5′- and 3′-UTRs of BRCA1, three previously unreported single-nucleotide polymorphisms
(SNPs) were identified, two (−1228T >C, −1173C >T) in the putative promoter regions
and one non-synonymous SNP (63449G >A) in exon 23. Compared with 16 normal samples, the
sequences from 34 CMTs suggested that SNP (−1173C >T) was associated with the
development of CMTs (odds ratio (OR)=2.57, 95% confidence interval (CI): 1.07–6.15). 相似文献
57.
Kosei SAKAI Tomohiro YONEZAWA Hideyuki YAMAWAKI Toshifumi OYAMADA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(10):1319-1322
Somatostatin receptor 2 (SSTR2) is a negative regulator of cell proliferation in human
breast cancer. Since there is little information about SSTR2 in canine mammary gland tumor
(MGT), we clarified its distribution and expression level in normal mammary gland, benign
MGT and malignant MGT. SSTR2 expression determined by immunohistochemical staining was
observed in the cytoplasm of luminal epithelial cells. The intensity was negatively
correlated with malignancy: normal tissues and some of the benign tumors had the highest
levels, while the malignant tumors had little or no SSTR2 expression. As for the Western
blotting, SSTR2 protein level in benign tumors was significantly lower than the normal
mammary gland. On the other hand, SSTR2 protein levels in two of three malignant tumors
were higher than the other groups. These results suggest that SSTR2 expression alters
according to the malignancy of canine MGT. 相似文献
58.
为实现对玉米黄花叶病毒(maize yellow mosaic virus,MaYMV)的血清学检测,丰富该病毒的检测方法,将编码MaYMV运动蛋白(movement protein,MP)的基因连接到原核表达载体pDBHis-MBP上,将构建成功的原核表达质粒转化到大肠杆菌Escherichia coli中诱导表达融合蛋白,将纯化后的融合蛋白对新西兰大白兔Oryctolagus cuniculus进行免疫并制备MaYMV MP多克隆抗血清,并采用Western blot对抗血清的效价、灵敏度和特异性进行检测。结果显示,利用成功构建的原核表达载体经诱导表达获得分子量大小约为62 kD的融合蛋白,纯化后对新西兰大白兔进行免疫获得MaYMV MP抗血清,该抗血清的效价为1∶128 000,灵敏度为1∶32,且该抗血清能够特异性地检测到本氏烟Nicotiana benthamiana中瞬时表达的MaYMV MP,而不与马铃薯卷叶病毒属Polerovirus及黄症病毒属Luteovirus的其他病毒发生血清学交叉反应,证明该抗血清具有良好的特异性。表明本研究制备的MaYMV MP抗血清能特异性... 相似文献
59.
中黑盲蝽Adelphocoris suturalis是一种重要的农业害虫,主要为害棉花、果树和牧草等作物。昆虫保幼激素(juvenile hormone, JH)与蜕皮激素(molting hormone, 20E)是调控昆虫生殖的主要因素。本研究运用基因克隆、基因沉默(RNAi)、实时荧光定量PCR(qPCR)等技术研究蜕皮激素受体(ecdysone receptor, EcR)、超气门蛋白(ultraspiracle protein, USP)在中黑盲蝽生殖调控中的作用。结果表明,中黑盲蝽EcR基因的ORF全长1 413 bp,编码470个氨基酸。预测蛋白质分子量为53.65 kD,pI值为7.79。中黑盲蝽USP基因ORF全长1 209 bp,编码402个氨基酸。预测蛋白质分子量为44.99 kD, pI值为7.94。与对照相比,注射dsEcR、dsUSP后6~18 d的中黑盲蝽体内EcR基因、USP基因在转录水平分别被显著抑制;卵巢的挂卵量分别仅有对照组的31.5%、86.6%;单雌产卵量减少36.0%~80.4%,显著低于对照。EcR和USP基因沉默后,产卵前期与对照相比无显... 相似文献