全文获取类型
收费全文 | 14059篇 |
免费 | 750篇 |
国内免费 | 1014篇 |
专业分类
林业 | 804篇 |
农学 | 1001篇 |
基础科学 | 549篇 |
1607篇 | |
综合类 | 5070篇 |
农作物 | 892篇 |
水产渔业 | 917篇 |
畜牧兽医 | 3027篇 |
园艺 | 1085篇 |
植物保护 | 871篇 |
出版年
2024年 | 64篇 |
2023年 | 182篇 |
2022年 | 382篇 |
2021年 | 455篇 |
2020年 | 477篇 |
2019年 | 626篇 |
2018年 | 398篇 |
2017年 | 577篇 |
2016年 | 663篇 |
2015年 | 636篇 |
2014年 | 696篇 |
2013年 | 777篇 |
2012年 | 1063篇 |
2011年 | 1249篇 |
2010年 | 1003篇 |
2009年 | 904篇 |
2008年 | 865篇 |
2007年 | 905篇 |
2006年 | 755篇 |
2005年 | 547篇 |
2004年 | 413篇 |
2003年 | 334篇 |
2002年 | 266篇 |
2001年 | 235篇 |
2000年 | 228篇 |
1999年 | 187篇 |
1998年 | 121篇 |
1997年 | 115篇 |
1996年 | 97篇 |
1995年 | 102篇 |
1994年 | 71篇 |
1993年 | 68篇 |
1992年 | 68篇 |
1991年 | 54篇 |
1990年 | 42篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 24篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1977年 | 6篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1956年 | 8篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Tidholm A Falk T Gundler S Svensson H Ablad B Sylvén C 《Research in veterinary science》2003,75(3):195-201
Nineteen euthyroid dogs of 12 breeds with echocardiographic signs of dilated cardiomyopathy (DCM) and radiographic and clinical signs of congestive heart failure (CHF) were evaluated in a randomised, double-blind, and placebo-controlled study. The dogs received either thyroxine or placebo as an adjunct to digoxin, furosemide and propranolol. The group assignment of individual dogs and serum concentrations of thyroid hormones remained unknown to owners and investigators during the entire study period. Dogs were evaluated clinically and with electrocardiography (ECG), thoracic radiography, echocardiography and measurement of total thyroxine (tT4) and thyroid stimulating hormone (TSH) before beginning of the trial, and then one week, 2 months, 6 months and yearly after initial examination, and, when applicable, at the time of euthanasia. End-point of the study was euthanasia (n = 17) due to severe congestive heart failure or sudden death (n = 2). Survival times ranged from 17 to 1030 days (median 187 days) in the placebo group, and from 18 to 1000 days (median 73 days) in the treatment group. There was no statistically significant difference in survival times between the treatment group and the placebo group (p = 0.46). Post mortem and histopathologic examinations revealed the attenuated wavy fiber type of DCM in 11 dogs, and myocardial infarcts, arteriosclerosis and chronic valvular disease in one dog. In conclusion, there was a wide range in survival times of dogs treated with digoxin, furosemide and propranolol. Adding thyroid hormones to the treatment did not significantly influence survival. 相似文献
912.
913.
914.
To investigate the action of dinotefuran (MTI-446, 1-methyl-2-nitro-3-(tetrahydro-3-furylmethyl)guanidine), a recently developed insecticide, on insect nicotinic acetylcholine receptors (nAChRs), we determined the potencies of the compound and 15 analogues in inhibiting the specific binding of [3H]epibatidine (EPI), a nAChR agonist, and [3H]alpha-bungarotoxin (alpha-BGT), a competitive nAChR antagonist, to the nerve cord membranes of American cockroaches (Periplaneta americana). Racemic dinotefuran inhibited [3H]EPI binding with an IC50 of 890 nM and [3H]alpha-BGT binding with an IC50 of 36.1 microM. Scatchard analysis indicated that the dinotefuran inhibition of [3H]EPI binding was a competitive one. Slight structural modification caused a drastic reduction in potency; only four analogues were found to be equipotent to or more potent than dinotefuran. Chloropyridinyl and chlorothiazolyl neonicotinoid insecticides displayed two or three orders of magnitude higher potency than dinotefuran. There was a good correlation between the IC50 values of tested compounds obtained with [3H]EPI and those obtained with [3H]alpha-BGT. A better correlation was observed between 3-h knockdown activities (KD50) against German cockroaches (Blattella germanica) and IC50 values obtained from [3H]EPI assays than between 24-h lethal activities (LD50) and IC50 values. While the results indicate that dinotefuran and its analogues interact with the ACh-binding site in cockroach nAChRs, it remains to be elucidated why they displayed lower potencies than those expected based on their insecticidal activities. 相似文献
915.
Samartino LE 《Veterinary microbiology》2002,90(1-4):71-80
Brucellosis has been recognized in Argentina since the 19th century. Several studies demonstrated the presence of the disease in most of the domestic species. Actually, the estimate of prevalence is that between 10 and 13% of the farm animals are infected with bovine brucellosis with an individual rate of 4–5%. The annual economical losses have been estimated at US$ 60,000,000. The control of bovine brucellosis began in 1932 and successive resolutions have been issued since then. The current resolution indicates that B. abortus S19 is mandatory in female calves between 3 and 8 months of age. The vaccine strain B. abortus RB51 was provisionally approved but only for cattle older than 10 months of age. The brucellosis control program consists principally of test and slaughter. This methodology has been successful mainly in the dairy farms that have the incentive due to increased pricing because of obtaining a low prevalence of the disease. Brucellosis has been found in porcine, caprine, ovine and canine species. All Brucella species have been found in the country. Human brucellosis is an important disease and a national coordinated diagnostic net has been formed to better control the disease in man. 相似文献
916.
The pharmacokinetics of furathiocarb were studied in vivo in male Sprague-Dawley rats following dermal treatment. HPLC and post-column derivatization were used for the analysis of furathiocarb and its metabolites (carbofuran, 3-hydroxycarbofuran and 3-ketocarbofuran). Carbofuran and 3-hydroxycarbofuran were detected in plasma and urine rather than furathiocarb. 3-Ketocarbofuran, another potential metabolite, was not observed in any sample. The concentration of carbofuran was higher than that of 3-hydroxycarbofuran in plasma, but the reverse was the case in urine. The corresponding area under the plasma concentration-time curve, Tmax, and Cmax values of carbofuran and 3-hydroxycarbofuran for 1500 mg kg-1 doses were 2.4-8.0 mg equiv hml-1, 12 h and 0.1-0.4 mg equiv ml-1, respectively. T1/2 was calculated only for 3-hydroxycarbofuran (28 h). Two metabolites were excreted in a dose-dependent manner without saturation. 相似文献
917.
Interactions between Plasmopara helianthi, Glomus mosseae and Two Plant Activators in Sunflower Plants 总被引:1,自引:0,他引:1
Laura Tosi Antonio Zazzerini 《European journal of plant pathology / European Foundation for Plant Pathology》2000,106(8):735-744
Interactions between Plasmopara helianthi, Glomus mosseae and two plant activators DL--amino-n-butyric acid (BABA) and CGA 245704 (acibenzolar-S-methyl (BTH)) in sunflower plants susceptible to downy mildew were studied in four experiments using different methods of treatment and pathogen inoculation. Both chemicals were applied as soil drenches and foliar sprays, whereas P. helianthi infection was obtained by root and cotyledon inoculations of the seedlings. Soil drenches at the rates of 50 and 100mgkg–1 soil of BABA and BTH given 1 and 3 days before P. helianthi inoculation, respectively to mycorrhizal plants, provided moderate protection against the pathogen (about 50–55%). Morphological changes and decrease in mycorrhizal colonization in roots of BTH-treated plants and in BTH-treated mycorrhizal plants were also observed. Delay in the emergence and reduction of the root systems were more evident at the highest concentration but decreased with time. These effects were absent with the BABA treatment.Foliar spray treatment of BABA and BTH, applied at 4000 and 200µgml–1, respectively (1 day post-inoculation) to mycorrhizal plants provided good protection (about 80%) against P. helianthi foliar infections. No effects on mycorrhizal colonization or on root systems were observed.
In vitro tests on the effect of the compounds on the mycorrhizal fungus showed that the germination of G. mosseae sporocarps increased with BABA treatment whereas it was greatly inhibited by BTH treatment. 相似文献
918.
弓形虫微线体蛋白MIC3基因的克隆及原核表达 总被引:11,自引:1,他引:11
根据编码MIC3的已知基因序列设计并合成一对引物,应用PCR技术从弓形虫RH株的基因组DNA中扩增编码MIC3的全长基因,克隆入pGEX-KG表达载体,转化入E.coli DH5α感受态细胞,经含氨苄青霉素琼脂平板筛选,小量抽提质粒进行酶切、PCR及DNA测序鉴定.然后阳性重组质粒转化入E.coli BL21-CodonPlus,IPTG诱导,表达产物经SDS-PAGE和Western-blot分析鉴定.结果显示,扩增的MIC3基因与GenBank中相应基因序列(AJ132530)的同源性达99.6 %,表达的MIC3融合蛋白表观分子量约为66 ku,且可被兔抗弓形虫免疫血清识别.说明所获得的表达蛋白质具有一定的反应原性,为下一步利用重组蛋白建立弓形虫的诊断方法和研制弓形虫的亚单位疫苗奠定了基础. 相似文献
919.
提取鸡病毒性关节炎病毒(AVAV)内蒙古分离株(C-98株)总RNA,参考GenBank中禽呼肠孤病毒(ARV)S1133株S1基因序列设计了2对引物,应用RT—PCR技术扩增了病毒S1基因,将S1基因cDNA克隆到pGEM—T Easy载体后测序。将测定序列拼接后与参考毒株ARV-176、ARV-138、ARV-S1133、MDRV—YJL的S1基因序列进行了比较。结果显示,AVAV C-98分离株的S1基因与强毒株ARV-176株的同源性最高,达99.9%;与MDRV—YJL的同源性为99.3%,与弱毒疫苗株ARV—S1133的同源性也达97.9%;与ARV-138株的同源性最低,为81.2%。表明,AVAVC-98株与参考毒株的差异较小,与疫苗株ARV-S1133有很高的同源性。 相似文献
920.