全文获取类型
收费全文 | 3252篇 |
免费 | 316篇 |
国内免费 | 12篇 |
专业分类
林业 | 259篇 |
农学 | 135篇 |
基础科学 | 16篇 |
549篇 | |
综合类 | 165篇 |
农作物 | 214篇 |
水产渔业 | 453篇 |
畜牧兽医 | 1413篇 |
园艺 | 68篇 |
植物保护 | 308篇 |
出版年
2024年 | 4篇 |
2023年 | 39篇 |
2022年 | 99篇 |
2021年 | 165篇 |
2020年 | 190篇 |
2019年 | 215篇 |
2018年 | 204篇 |
2017年 | 212篇 |
2016年 | 176篇 |
2015年 | 123篇 |
2014年 | 164篇 |
2013年 | 219篇 |
2012年 | 236篇 |
2011年 | 259篇 |
2010年 | 122篇 |
2009年 | 129篇 |
2008年 | 152篇 |
2007年 | 147篇 |
2006年 | 105篇 |
2005年 | 74篇 |
2004年 | 68篇 |
2003年 | 78篇 |
2002年 | 81篇 |
2001年 | 63篇 |
2000年 | 54篇 |
1999年 | 31篇 |
1998年 | 17篇 |
1997年 | 8篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1948年 | 2篇 |
排序方式: 共有3580条查询结果,搜索用时 0 毫秒
41.
Marcelo Luiz Laia Acelino Couto Alfenas Sergio Hermnio Brommonschenkel Shinitiro Oda Eduardo Jose de Melo Inae Marie de Arau jo Silva Janana Fernandes Goncalves Ariadne Marques 《林业研究》2015,(3)
Disease-resistant genes play an important role in defending against a variety of pathogens and insect pests in plants. Most of the disease-resistant genes encode pro-teins with conserved leucine rich r... 相似文献
42.
T Guimarães C Miranda M Pinto E Silva L Damásio AL Costa MJ Correia JC Duarte C Cosinha G Lopes G Thompson A Rocha 《Reproduction in domestic animals》2014,49(6):926-933
A possible role of breeding activities in the composition of the microbial population in stallions' external genitalia (EG) and the relationship between micro‐organisms colonizing the skin of the abdomen and the ones colonizing the EG have not been studied. In experiment 1, EG microbiological samples were collected from 41 stallions used for both natural cover and semen collection (BST) and from 18 non‐breeding stallions (NBST). A higher (p < 0.05) frequency of isolation of potentially pathogenic species was found for BST. Age did not influence number of micro‐organism species isolated both in BST and NBST. In experiment 2, the microbial content of the EG and semen was compared in 23 BST. Most micro‐organisms isolated from the EG were present in semen, albeit with a numerically lower prevalence. In 7 stallions, six microbial species isolated from semen were absent from the EG cultures, suggesting contamination by the operator. In experiment 3, a numerically higher number of micro‐organism species was isolated from the EG of 31 stallions, than from their skin of the ventral abdomen in contact with the penis or from the skin of the thorax. With the sole exception of Escherichia coli, potentially pathogenic bacteria were only isolated from the EG but not from the skin. Results suggest that breeding activity increased the number of species colonizing the EG; most species isolated from the EG were also found in semen even if with a lower frequency, and additional semen contamination seemed to occur during its manipulation. Many micro‐organism species of the skin were also isolated from the penis, but independently of being or not in contact with the penis, skin did not seem to provide an adequate environment for the growth of potentially pathogenic bacteria that were isolated from EG, with the sole exception for E. coli. 相似文献
43.
The influence of Ringer's lactate or HES 130/0.4 administration on the integrity of the small intestinal mucosa in a pig hemorrhagic shock model under general anesthesia 下载免费PDF全文
44.
Characterization of the LH peak after short and long fixed‐time artificial insemination protocols in sheep raised in the tropics 下载免费PDF全文
Gabriela Azenha Milani Soriano Felipe Rydygier de Ruediger Marilice Zundt Marco Aurélio da Cruz Nobre Gomes Lilian Francisco Arantes de Souza Ines Cristina Giometti Guilherme de Paula Nogueira Gustavo Ricci Zanelli Fabiola Cristiane de Almeida Rego Caliê Castilho 《Animal Science Journal》2018,89(9):1245-1252
The aim of this study was to evaluate the peak in luteinizing hormone (LH) and the pregnancy rate of sheep (Texel × Santa Inês) in the tropics using short‐ (6 days) and long‐term (12 days) progesterone protocols followed by artificial insemination (AI) both in and out of the breeding season. Experiment 1 was conducted within (IN) the breeding season (autumn, n = 36), and experiment 2 was conducted outside (OUT) of the breeding season (spring, n = 43). In each experiment, the sheep were divided into two groups (6 or 12 days) according to the duration of treatment with a single‐use progesterone release vaginal device (CIDR®, Pfizer, São Paulo, SP, Brazil), and blood samples were collected from 10 animals per group every 4 hr to measure the LH and progesterone concentrations. In the spring, the characteristics of the LH peak did not differ between groups; but in the autumn, there were differences between groups at the beginning (G‐6 IN: 36.44 ± 5.46 hr; G‐12 IN: 26.57 ± 4.99 hr) and end of the LH peak (G‐6 IN: 46.22 ± 7.51 hr; G‐12 IN: 34.86 ± 8.86 hr). The results showed alterations in the LH peak during the breeding season only in the sheep undergoing the short‐term protocol. 相似文献
45.
Neto JO Azevedo SS Gennari SM Funada MR Pena HF Araújo AR Batista CS Silva ML Gomes AA Piatti RM Alves CJ 《Veterinary parasitology》2008,156(3-4):329-332
The prevalence and risk factors for anti-Toxoplasma gondii antibodies were investigated in goats of the Seridó Oriental microregion, Rio Grande do Norte state, Northeast region of Brazil. Three hundred and sixty-six blood samples from goats collected by jugular venopuncture were used. For the serologic diagnosis of Toxoplasma gondii infection, the indirect fluorescent-antibody test (IFAT) with cut-off value 1:64 was carried out. The prevalence of anti-T. gondii antibodies was 30.6% [95% CI=25.9-35.6%] with titers ranging from 1:64 to 1:16,384. The multivariate logistic regression analysis showed that the risk factors associated to anti-T. gondii antibodies were presence of cats in the herd, extensive/semi-intensive management systems and lack of mineral supplementation. 相似文献
46.
Effect of incubation temperature regimes and culture medium on broccoli microspore culture embryogenesis 总被引:8,自引:0,他引:8
João Carlos da Silva Dias 《Euphytica》2001,119(3):389-394
Conditions for reliable induction of embryogenesis from isolated microspores were studied in ten genotypes of broccoli. Embryo
yields were significantly increased in almost all of the broccoli genotypes by the incubation at 32.5 °C for 1 day, than when the standard incubation at 30 °C for 2 days was used. Treatments of 48 hours at 32.5 °C produced less than optimal results suggesting that broccoli microspores are more sensitive to high temperatures than those
of B. napus. The use of the 1/2 NLN-13 medium yielded greater number of embryos than the standard NLN-13. The magnitude of the response to the redution of
the concentration of major salts by half in the NLN medium varied with the different genotypes. High embryogenic broccoli
cultivars, such as ‘Shogun’, ‘SDB9’, and ‘Green Valiant’, presented a better response to the reduction of the concentration
of major salts by half in NLN-13. Reduction never produced a detrimental effect on embryo yield and seems not to have any
effect in the subsequent development of embryos in plants.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
47.
Samanta A Costa MH Nunes EL Vieira SA Xu L Myneni RB 《Science (New York, N.Y.)》2011,333(6046):1093; author reply 1093
Zhao and Running (Reports, 20 August 2010, p. 940) reported a reduction in global terrestrial net primary production (NPP) from 2000 through 2009. We argue that the small trends, regional patterns, and interannual variations that they describe are artifacts of their NPP model. Satellite observations of vegetation activity show no statistically significant changes in more than 85% of the vegetated lands south of 70°N during the same 2000 to 2009 period. 相似文献
48.
Abias Santos Silva Luiz Gustavo Ribeiro Pereira Márcio dos Santos Pedreira Fernanda Samarini Machado Mariana Magalhães Campos Cristina Simões Cortinhas Tiago Sabella Acedo Rafael Dantas dos Santos João Paulo Pacheco Rodrigues Rogério Martins Maurício Thierry Ribeiro Tomich 《Journal of animal physiology and animal nutrition》2020,104(1):76-87
The effect of exogenous amylase on the in vitro rumen digestion kinetics of whole-crop maize silage made from dent (RB9004) or flint grain type (RB9308) was evaluated at different phenological stages: soft dough (SOD), early dent (EAD), ½ milkline (½M) and ¾ milkline (¾M). Forage was harvested from 70 to 110 days after sowing. Two rumen-cannulated cows receiving or not exogenous amylase (0.7 g/kg dry matter—DM, provided to achieve 396 kilo Novo units of amylase activity/kg of TMR DM) were used as donor of ruminal fluid. The in vitro gas production kinetics was evaluated according to a dual-pool logistic model. The chemical composition and gas production kinetics were affected by the hybrid and phenological stages. The flint hybrid had lower range for chemical analysis among physiological stages. Harvesting at ½M and ¾M improved DM content, bromatological composition and silage quality parameters compared to dent or flint types. Amylase (i) increased methane (CH4) production and in vitro dry matter digestibility (IVDMD) in ½M stage, (ii) improved digestion kinetics by reducing lag time and increasing total gas production and fermentation rates of non-fibrous carbohydrates (NFC) and fibrous carbohydrates (FC), and (iii) increased extent and fermentation rate of NFC and increased fermentation rate of FC fraction in whole-crop maize silages produced from dent or flint types in all phenological stages. Harvesting between ½M and ¾M is the best phenological stage to improve chemical composition and silage quality parameters. Exogenous amylase showed improvements on fibre digestion of silages at ½M and ¾M phenological stages in both grain types of corn. 相似文献
49.
Adens González Alfonso Silva Gonzalo Gajardo Claudio Martínez 《Journal of the World Aquaculture Society》2017,48(2):268-279
The palm ruff, Seriolella violacea (Cojinoba), is a potential new species for Chilean aquaculture. To approach Cojinoba larviculture, an experimental Artemia enrichment emulsion, containing docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) = 2.5, supplemented with vitamin E, astaxanthin, and β‐glucan, was evaluated in both Artemia and Cojinoba larvae, 30–50 d.a.h. This study tested an experimental enrichment emulsion versus a commercial emulsion, with an integral approach of multicompound emulsions. After 23 h enrichment, experimental emulsion (EE)‐enriched nauplii reached DHA and EPA concentrations of 23.8 and 18.7 mg/g dry weight (dwt), respectively, while in Cojinoba larvae they were 18.4 and 19.7 mg/g dwt. Control emulsion (CE)‐enriched nauplii exhibited lower DHA and EPA (6.1 and 7.7 mg/g dwt), while only DHA decreased in the control larvae (12.6 mg/g dwt). Vitamin E was higher in EE‐enriched nauplii (29.2 mg/100 g dwt) than in the control (8.4 mg/100 g dwt). Larvae fed EE‐enriched Artemia exhibited 8% increase in survival and 19% in growth compared with the control. Astaxanthin was detected only in larvae fed EE‐enriched nauplii. The tumor necrosis factor‐α concentration was not significantly different between larvae fed EE‐ and CE‐enriched nauplii. EE looks promising as an Artemia enrichment and experimental diet to assess palm ruff larval requirements, and has a positive impact on fish larvae performance. 相似文献
50.
José Maria Villela Pádua Kaio Olímpio Das Graças Dias Maria Marta Pastina João Cândido de Souza Valéria Aparecida Vieira Queiroz Rodrigo Veras da Costa Maria Beatriz Pereira da Silva Carlos Alexandre Gomes Ribeiro Claudia Teixeira Guimarães Salvador Alejandro Gezan Lauro José Moreira Guimarães 《Euphytica》2016,211(3):277-285