全文获取类型
收费全文 | 33682篇 |
免费 | 1676篇 |
国内免费 | 3194篇 |
专业分类
林业 | 2248篇 |
农学 | 2687篇 |
基础科学 | 1057篇 |
4268篇 | |
综合类 | 11825篇 |
农作物 | 2929篇 |
水产渔业 | 1167篇 |
畜牧兽医 | 8345篇 |
园艺 | 2494篇 |
植物保护 | 1532篇 |
出版年
2024年 | 179篇 |
2023年 | 584篇 |
2022年 | 1033篇 |
2021年 | 1266篇 |
2020年 | 1210篇 |
2019年 | 1520篇 |
2018年 | 1111篇 |
2017年 | 1303篇 |
2016年 | 1769篇 |
2015年 | 1930篇 |
2014年 | 2108篇 |
2013年 | 2248篇 |
2012年 | 2546篇 |
2011年 | 2391篇 |
2010年 | 2015篇 |
2009年 | 2105篇 |
2008年 | 1712篇 |
2007年 | 1954篇 |
2006年 | 1783篇 |
2005年 | 1317篇 |
2004年 | 972篇 |
2003年 | 787篇 |
2002年 | 615篇 |
2001年 | 547篇 |
2000年 | 541篇 |
1999年 | 435篇 |
1998年 | 334篇 |
1997年 | 301篇 |
1996年 | 282篇 |
1995年 | 241篇 |
1994年 | 213篇 |
1993年 | 192篇 |
1992年 | 172篇 |
1991年 | 150篇 |
1990年 | 151篇 |
1989年 | 122篇 |
1988年 | 96篇 |
1987年 | 64篇 |
1986年 | 51篇 |
1985年 | 49篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 25篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1962年 | 5篇 |
1956年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
合理确定聚集器的静压、压力平衡基准、聚集器的压力损失、设计流量等参数,对于保证集尘装置工作的可靠性和经济性都有重要意义。 相似文献
102.
0.05MpH9.6碳酸盐缓冲液和0.05MPH13NaOH溶液作为包被液,分别用于间接ELISA检测乙型五号病病毒抗体。结果表明,用0.05MPH13NaOH溶泡包被可完全灭活五号病病毒抗原而用0.05MPH9.6碳酸盐缓冲液却有87%的五号病病毒抗原未被杀灭;用于检测时,以0.05MPH13NaOH溶液为包被液在敏感性及检测结果的梯度方面都优于用0.05MPH9.6碳酸盐缓冲液。 相似文献
103.
2型猪链球菌的血清学鉴定 总被引:41,自引:0,他引:41
本试验首次证实了2型猪链球菌在我国的存在,采用玻片凝集、琼脂扩散及毛细管沉淀等3项试验,对1990年以来广东某猪场断奶仔猪暴发流行的败血症、脑膜炎及关节炎病猪中分离的15株链球菌进行了血清学鉴定。结果表明:15株链球菌均为2型猪链球菌;用高压法提取抗原进行沉淀反应,其结果比酸热法提取抗原具有简便、敏感、特异性强的特点。 相似文献
104.
K. Tagata S. Yokoyama T. Ginbo M. Honda T. Okimura M. Odakura M. Nomura S. Yamamoto 《Veterinary research communications》1996,20(1):21-30
A capillary reversed passive latex agglutination test (capillary RPLA) was developed which allows quantification of serum C-reactive protein (CRP) within approximately 15 min. The logarithmic regression line (calibration curve) obtained after measuring each CRP concentration three times in twofold dilutions of a standard canine serum containing 222 g/ml of CRP was y=6.394+0.030x (r=0.995). Capillary RPLA permitted quantification of CRP in the range 6.9–222 g/ml. The coefficients of variation ranged from 10.28% to 12.40%. The recovery rates (percentage recovery) of CRP by capillary RPLA were within the range 87% to 106%. On measuring the CRP concentrations in sera from 78 dogs by capillary RPLA, single radial immunodiffusion (SRID) and enzyme-linked immunosorbent assay (ELISA), close correlations were demonstrated between SRID and capillary RPLA (y=7.250+1.109x, r=0.978), between SRID and ELISA (y=3.042+1.059x, r=0.967), and between capillary RPLA and ELISA (y=1.778+0.929x, r=0.962). Capillary RPLA may be considered useful as a routine biochemical technique for measurement of serum CRP concentration in the dog.Abbreviations CRP
C-reactive protein
- ELISA
enzyme-linked immunosorbent assay
- RPLA
reversed passive latex agglutination test
- SRID
single radial immunodiffusion 相似文献
105.
INTRODUCTIONIntheworldoftoday,theglobalclimatechangeanditsinfluenceonecologyhavebe-comeaveryimportantproblem,towhichmanyscientists,governnentleadersandordinarypcoplepaycloseattentionI1-'].Inl979,theWorldClimateResearchProgram(WCP)waslaiddowninthefirstworldclimatemeeting.lnl99(),thesecondworldclimatemeetingwasconvcl1edinGencva,andalltl1eexpertsagreedthattheglobalwarmlngwillbeextremelyseriousdisasterthananynatUralcalamityever.Attl1eMectingof"WorldEnvironmentandDevelopment,"holdinBrazil… 相似文献
106.
Land cover data for landscape ecological studies are frequently obtained by field survey. In the United Kingdom, temporally separated field surveys have been used to identify the locations and magnitudes of recent changes in land cover. However, such map data contain errors which may seriously hinder the identification of land cover change and the extent and locations of rare landscape features. This paper investigates the extent of the differences between two sets of maps derived from field surveys within the Northumberland National Park in 1991 and 1992. The method used in each survey was the Phase 1 approach of the Nature Conservancy Council of Great Britain. Differences between maps were greatest for the land cover types with the smallest areas. Overall spatial correspondence between maps was found to be only 44.4%. A maximum of 14.4% of the total area surveyed was found to have undergone genuine land cover change. The remaining discrepancies, equivalent to 41.2% of the total survey area, were attributed primarily to differences of land cover interpretation between surveyors (classification error). Differences in boundary locations (positional error) were also noted, but were found to be a relatively minor source of error. The implications for the detection of land cover change and habitat mapping are discussed. 相似文献
107.
G. Jager H. Velvis 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(4):467-478
The position of plants withRhizoctonia solani sclerotia (black scurf) on progeny tubers was mapped for an experimental field at Haren where potatoes were grown continuously and in rotation with other crops for five successive years, and for another field at Borgercompagnie with a 12 frequency of potatoes during three potato crops. Initially, the distribution of plants with black scurf on both fields was rather dense and homogeneous. In the following years the distribution became heterogeneous and patchy. The local decline ofR. solani AG 3 (the common potato pathogen) in Haren was apparently caused by an unknown factor selectively suppressingR. solani AG 3, while simultaneouslyR. solani AG 5 increased in mass. This AG 5 type proved to be an inferior competitor of AG 3 on the potato plant in a laboratory experiment. The specificR. solani antagonistVerticillium biguttatum did not play a role. A similar factor could have reduced the formation of black scurf in the experimental field at Borgercompagnie, whereV. biguttatum was also too infrequent to account for the decline.R. solani AG 5 was not present here and could not indicate the presence of a selective factor against AG 3. 相似文献
108.
109.
C肉毒杀鼠素在高寒草甸地区灭鼠技术中的应用 总被引:2,自引:0,他引:2
综述C肉毒杀鼠素草原灭鼠应用技术,充分肯定了C肉毒杀鼠素毒力强、适口性好、对非靶动物毒性低、作用缓慢、无二次中毒、易降解和适合规模灭鼠的特点,为鼠害防治提供了新的思路。 相似文献
110.