全文获取类型
收费全文 | 269382篇 |
免费 | 15905篇 |
国内免费 | 2126篇 |
专业分类
林业 | 25049篇 |
农学 | 16024篇 |
基础科学 | 4075篇 |
44970篇 | |
综合类 | 29688篇 |
农作物 | 17986篇 |
水产渔业 | 17204篇 |
畜牧兽医 | 100611篇 |
园艺 | 6835篇 |
植物保护 | 24971篇 |
出版年
2021年 | 3068篇 |
2020年 | 3347篇 |
2019年 | 4152篇 |
2018年 | 4273篇 |
2017年 | 4780篇 |
2016年 | 5254篇 |
2015年 | 4952篇 |
2014年 | 6220篇 |
2013年 | 16938篇 |
2012年 | 7210篇 |
2011年 | 9174篇 |
2010年 | 8162篇 |
2009年 | 8695篇 |
2008年 | 8412篇 |
2007年 | 7506篇 |
2006年 | 8074篇 |
2005年 | 7201篇 |
2004年 | 6745篇 |
2003年 | 6490篇 |
2002年 | 5758篇 |
2001年 | 6507篇 |
2000年 | 6118篇 |
1999年 | 5865篇 |
1998年 | 4497篇 |
1997年 | 4485篇 |
1996年 | 4200篇 |
1995年 | 4746篇 |
1994年 | 4101篇 |
1993年 | 3801篇 |
1992年 | 4585篇 |
1991年 | 4638篇 |
1990年 | 4326篇 |
1989年 | 4357篇 |
1988年 | 3791篇 |
1987年 | 3846篇 |
1986年 | 3791篇 |
1985年 | 4026篇 |
1984年 | 3711篇 |
1983年 | 3518篇 |
1982年 | 2900篇 |
1981年 | 2834篇 |
1980年 | 2796篇 |
1979年 | 3141篇 |
1978年 | 2849篇 |
1977年 | 2662篇 |
1976年 | 2494篇 |
1975年 | 2344篇 |
1974年 | 2536篇 |
1973年 | 2523篇 |
1972年 | 2242篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
以盆花月季'仙境'为试材,采用根部浇灌方式,设置0(P0)、10 (P10)、20(P20)、30(P30)g·柱-14个磷供应水平,研究了磷水平对盆花月季'仙境'根系生长、不同器官氮磷养分吸收、叶片SPAD值以及开花品质(花朵数量、花径、花朵干质量等)的影响,以期为月季养分管理提供参考依据.结果 表明:磷不同供应水平明显改变了'仙境'的根系形态,P20和P30处理较P0和P10处理,总根长增加了81%~111%,总根表面积扩大了133%~196%,细根总长度增加了95%~119%.植株不同器官(新生叶片、新生枝条和根系)生物量和氮、磷养分积累量表现出与根系生长类似的趋势.与P0和P10处理相比,P20和P30处理单株花朵数量增加128%~206%,叶片SPAD值增加16%~21%.与对照P0相比,P10、P20和P30花径分别增加12%、19%和24%.植株总根长与总氮和总磷吸收量表现出显著的正相关关系.综上所述,盆花月季'仙境'对不同磷供应水平表现出高度的根形态可塑性,适宜的磷供应水平促进根系生长和养分吸收,提高开花数量和品质. 相似文献
33.
34.
The aerobic bacterial flora of the genital tract was characterized in 15 stud dogs in an 18-month study. The dogs represented 4 breeds and were from 3 kennels. Bacterial samples from the prepuce and semen were collected every month, except in connection with matings, when they were collected weekly (464 samples). The dogs that were included all mated at least once during the study. The mean pregnancy rate, litter size, and pup mortality for the bitches with which they had mated were all within normal limits. The most frequent bacteria isolated from the prepuce and semen were Pasteurella multocida, beta-hemolytic streptococci, and Escherichia coli. There was a tendency for breeds to differ in frequency of the most common bacterial species. Bacterial culture yielded no aerobic growth in 14.2% of the preputial samples and 69.8% of the semen samples. Bacteria were transferred between dog and bitch at mating. In this study of healthy breeding dogs, neither the fertility of the dog nor that of the bitch was affected by the bacteria transferred. 相似文献
35.
K A Hahn D W Knapp R C Richardson C L Matlock 《Journal of the American Veterinary Medical Association》1992,200(3):355-357
In 11 dogs with nasal adenocarcinoma, IV treatment with 2 to 8 cycles of cisplatin at a dosage of 60 mg/m2 of body surface, given at 3-week intervals, resulted in a survival time of 8 to 128 weeks (mean, 32.7 weeks; median, 20 weeks). Radiography revealed complete remission in 2 dogs and partial remission in 1 dog, for an overall response rate of 27%. Clinical problems such as nasal discharge (n = 11), sneezing (n = 6), and epistaxis (n = 4) resolved in 1 to 2 weeks in all dogs after beginning chemotherapy. 相似文献
36.
The influence of extruded oilseeds on total tract digestibility and ruminal digestion in dairy cows was studied in three cows fed a hay-concentrate (60.5/39.5; 3.7% fatty acids in diet on DM basis) control diet (C) or the same diet supplemented with raw (R) or extruded (ER) rapeseeds (8.0% fatty acids in diet DM). The experimental design was a 3 x 3 Latin square design. Compared with diet C, diets containing rapeseed decreased ruminal OM digestibility (9.5%, P less than .10) and increased (P less than .05) the proportion of propionate in ruminal fluid VFA. Extrusion had no effect on DM and OM total tract digestibilities and increased (P less than .10) N digestion. Microbial N flow at the duodenum was calculated taking into account solid-adherent bacteria (SAB) and liquid-associated bacteria (LAB). Duodenal flows of total, SAB, and LAB of OM and N did not change with diet. Extrusion of the rapeseeds did not modify (P less than .10) the proportion of bacterial N at the duodenum and had no effect on crude fiber digestibility. This trial demonstrates that rapeseeds in hay-based diets can be fed at levels of up to 14% of the diet without adversely affecting crude fiber digestibility. 相似文献
37.
Osteomyelitis caused by Cryptococcus neoformans was diagnosed in a three-year-old male Irish wolfhound. The case details and radiological findings of radiolucency and periosteal reaction of the left third metatarsal bone had lead to an initial diagnosis of a malignant bone tumour. Biopsy revealed a fungal granuloma and culture identified the causal organism. A four month course of ketaconazole was instigated and the lameness resolved. Twelve months after the end of treatment there was no recurrence of the problem. 相似文献
38.
Findings are presented on the precision of a clinical biochemistry analyser designed specifically for veterinary use. Twenty biochemical analytes have been examined in detail for variation within and between runs. The results indicate that the analyser can provide high precision for all the analytes with the possible exception of calcium, and suggest that the instrument can be used with confidence in the practice laboratory to aid diagnosis and to monitor biochemical changes in animals receiving treatment. 相似文献
39.
40.
R C Weiss 《American journal of veterinary research》1992,53(5):829-833
The immunomodulatory capacities of N,N-dimethylglycine (DMG) were examined in random-source cats. Blood mononuclear leukocytes of healthy adult cats that had negative results to tests for FeLV and feline immunodeficiency virus were exposed in vitro to various concentrations of DMG (10 to 1,000 micrograms/ml) and were evaluated for proliferative responses to T- or B-cell phytomitogens. Although increased, mean lymphocyte blastogenic responses to phytolectins in DMG-treated cultures did not differ significantly from responses of untreated cultures. For in vivo studies, cats were given a solution containing either 100 mg of DMG or a control solution without DMG orally at 8 AM and 6 PM for 40 consecutive days. On post-treatment day 24 and 25, mean blastogenic responses to phytolectins in DMG-treated and control cats inoculated 10 days earlier with an inactivated feline virus vaccine were similar. Cats given DMG and inoculated twice in a 3-week interval with a commercial vaccine containing inactivated feline herpesvirus-1 and feline calicivirus had significantly (P = 0.045) lower virus neutralizing serum antibody titers against feline herpesvirus-1, compared with titers of control cats, whereas feline calicivirus titers were similar in both groups. On day 25, mean serum interferon activity, induced after IV inoculation of Newcastle disease virus, was significantly (P = 0.021) lower in the DMG-treated cats. Results of this study of DMG in healthy cats failed to demonstrate enhancement of either specific or nonspecific immunity. 相似文献