全文获取类型
收费全文 | 102648篇 |
免费 | 19869篇 |
国内免费 | 30026篇 |
专业分类
林业 | 11413篇 |
农学 | 11296篇 |
基础科学 | 10611篇 |
37789篇 | |
综合类 | 41324篇 |
农作物 | 8170篇 |
水产渔业 | 7167篇 |
畜牧兽医 | 12933篇 |
园艺 | 3774篇 |
植物保护 | 8066篇 |
出版年
2024年 | 1024篇 |
2023年 | 1591篇 |
2022年 | 2624篇 |
2021年 | 2864篇 |
2020年 | 4241篇 |
2019年 | 7462篇 |
2018年 | 6756篇 |
2017年 | 8063篇 |
2016年 | 8475篇 |
2015年 | 8866篇 |
2014年 | 8032篇 |
2013年 | 8738篇 |
2012年 | 9049篇 |
2011年 | 8048篇 |
2010年 | 7003篇 |
2009年 | 6340篇 |
2008年 | 5091篇 |
2007年 | 5294篇 |
2006年 | 4695篇 |
2005年 | 4128篇 |
2004年 | 3281篇 |
2003年 | 2948篇 |
2002年 | 2814篇 |
2001年 | 2394篇 |
2000年 | 2085篇 |
1999年 | 2144篇 |
1998年 | 1816篇 |
1997年 | 1784篇 |
1996年 | 1555篇 |
1995年 | 1612篇 |
1994年 | 1525篇 |
1993年 | 1236篇 |
1992年 | 1241篇 |
1991年 | 1043篇 |
1990年 | 810篇 |
1989年 | 778篇 |
1988年 | 671篇 |
1987年 | 471篇 |
1986年 | 443篇 |
1985年 | 220篇 |
1984年 | 220篇 |
1983年 | 202篇 |
1982年 | 204篇 |
1981年 | 243篇 |
1980年 | 197篇 |
1979年 | 160篇 |
1978年 | 132篇 |
1975年 | 111篇 |
1965年 | 138篇 |
1964年 | 141篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
961.
962.
963.
农村作为城市的后花园,承担接受城市经济、工业企业产业转移的作用。对新农村建设的发展模式以及在建设进程中对青山绿水造成的破坏进行了研究分析,并对大跃进时期人类"人定胜天"的论调给予了评伦,期待在新农村建设中更多地尊重自然,尊重农民意愿,给人类留下一片蓝天碧水。 相似文献
964.
965.
用壳聚糖对黄瓜汁进行澄清试验,研究了壳聚糖用量、pH、温度等工艺条件对黄瓜汁澄清效果的影响,并通过正交试验确定壳聚糖澄清黄瓜汁的最适工艺条件为:壳聚糖用量0.5g/L、温度50℃、pH4.0、反应时间1.5 h. 相似文献
966.
本文结合鄂伦春自治旗农牧业的物殊现状分析,指出在推进鄂伦春农牧业产业化过程中存在的主要问题,并有针对性地提出相应的对策和建议. 相似文献
967.
Yamamoto Y Nakamura K Kitagawa K Ikenaga N Yamada M Mase M Narita M 《Avian diseases》2007,51(1):52-57
One-day-old, 2-wk-old, and 4-wk-old call ducks (Anas platyrhyncha var. domestica) inoculated intravenously with the H5N1 highly pathogenic avian influenza virus A/chicken/Yamaguchi/7/2004 isolate (Ck/Yama/7/04) were examined clinically, pathologically, and virologically. Clinically, the birds exhibited mild-to-severe neurologic signs and corneal opacity. All birds in the 1-day-old group and one bird in the 4-wk-old group died within 4 days after the virus inoculation. Histologic changes were characterized by severe nonpurulent encephalitis and necrotic lesions of feather epithelium on day 3 postinoculation (PI) or later. Focal necrosis of myocardial cells, pancreatic acinar cells, skeletal myocytes, and corneal epithelial cells was observed. Viral antigens were detected in association with necrotic changes. Viruses were isolated from all examined organs including the skin with many feathers. Serum antibody against the virus was detected in all surviving birds on day 10 PI by hemagglutination-inhibition tests. These results suggest that Ck/Yama/7/04 has a pathogenicity that causes neurologic sign, nonpurulent encephalitis with mortality, and feather lesions for call ducks. Feather lesions with viral antigens and the virus isolation from the skin suggest that Ck/Yama/ 7/04 has a predilection for feathers in call ducks. 相似文献
968.
An enzyme-linked immunosorbent assays (ELISA) based on recombinant nucleocapsid (N) protein generated in Escherichia coli was evaluated for its sensitivity and specificity for diagnosis of porcine epidemic diarrhea (PEDV) infection. The N gene encoding the N protein was cloned and expressed as a fusion protein with His tag protein in E. coli. The recombinant N protein was migrated at 48 kDa and reacted with six histidine tag specific monoclonal antibody by immunoblotting. Recombinant N protein ELISA (rnELISA) demonstrated 98.7% specificities among (80) PEDV-free individuals, and 98% sensitivity ranging among (103) clinical samples with PEDV. On testing 884 field samples, an overall agreement of 88.3% was generated between the SN and rnELISA. Taken together, these results indicated that nucleocapsid protein may be a useful antigen for the sera-diagnosis of PEDV and it was also suggested that the ELISA is a highly sensitive and specific test for detecting antibodies to PEDV. 相似文献
969.
Seasonal and photoperiodic regulation of secretion of hormones associated with reproduction in Magang goose ganders 总被引:1,自引:0,他引:1
Shi ZD Huang YM Liu Z Liu Y Li XW Proudman JA Yu RC 《Domestic animal endocrinology》2007,32(3):190-200
This study examined the reproductive endocrine profile under natural and artificial photoperiods in Magang goose ganders. Group 1 ganders (n=8) served as non-treated controls and were exposed to natural photoperiod throughout the experiment from 13th January to 17th December 2004. Group 2 ganders (n=8) were exposed to 18 h long daily photoperiod for 60 days from 13 January till 15 March 2004 and again to 16 h photoperiod for 75 days till 10th October 2004, and the 11h short photoperiod in the remainder periods of the experiment. In control ganders, plasma LH concentrations were high in normal breeding seasons (August-March) and decreased to low levels in non-breeding season from April to July. Testosterone concentrations changed similarly to that of LH throughout the seasons. Seasonal pattern of PRL concentrations was opposite to those of LH and testosterone, with low values in breeding season and high values in non-breeding season. In artificial photoperiod treated ganders, increasing photoperiod increased PRL and decreased LH and testosterone concentrations, while decreasing photoperiod reversed these changes. There were no seasonal or photoperiod caused changes in plasma T3 concentrations in both control ganders and artificial photoperiod treated ganders. These results demonstrated that in Magang goose ganders that long photoperiod stimulates PRL secretion and decreases LH secretion, which terminates reproductive season in spring and early summer, and short photoperiod stimulates LH secretion and inhibits PRL secretion rendering ganders enter into reproductive season. 相似文献
970.
Lin CT Hu CK Liu CH Yeh LS 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2007,69(8):847-850
Surgical outcome and complications following evisceration and implantation of intraocular silicone prosthesis (ISP) in 20 canine eyes with end-stage glaucoma were analyzed, including clinical signs, complications, cosmetic appearance, and owners' responses. The mean postoperative follow-up time was 312 days. Major short-term surgical complications were central corneal ulceration (6/20) and infections (3/20), while long-term complication was keratoconjunctivitis sicca (KCS) (2/20). All patient owners (100%) showed satisfied with the surgical outcome and postoperative cosmetic effect including 85% of the owners gave an excellent or good rating of satisfaction. No more medication needed for long term control except the KCS cases. With careful case selection and post-operative care, evisceration with ISP implantation proves a good and safe surgical procedure with minimal complications for end stage glaucoma. 相似文献