全文获取类型
收费全文 | 8778篇 |
免费 | 385篇 |
国内免费 | 409篇 |
专业分类
林业 | 1881篇 |
农学 | 731篇 |
基础科学 | 71篇 |
696篇 | |
综合类 | 3679篇 |
农作物 | 424篇 |
水产渔业 | 301篇 |
畜牧兽医 | 752篇 |
园艺 | 576篇 |
植物保护 | 461篇 |
出版年
2024年 | 34篇 |
2023年 | 94篇 |
2022年 | 170篇 |
2021年 | 189篇 |
2020年 | 251篇 |
2019年 | 257篇 |
2018年 | 168篇 |
2017年 | 267篇 |
2016年 | 364篇 |
2015年 | 308篇 |
2014年 | 443篇 |
2013年 | 540篇 |
2012年 | 717篇 |
2011年 | 741篇 |
2010年 | 607篇 |
2009年 | 630篇 |
2008年 | 490篇 |
2007年 | 549篇 |
2006年 | 462篇 |
2005年 | 357篇 |
2004年 | 287篇 |
2003年 | 199篇 |
2002年 | 173篇 |
2001年 | 151篇 |
2000年 | 143篇 |
1999年 | 123篇 |
1998年 | 123篇 |
1997年 | 97篇 |
1996年 | 115篇 |
1995年 | 75篇 |
1994年 | 67篇 |
1993年 | 63篇 |
1992年 | 50篇 |
1991年 | 54篇 |
1990年 | 42篇 |
1989年 | 47篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1977年 | 6篇 |
1975年 | 1篇 |
1963年 | 1篇 |
1956年 | 1篇 |
1955年 | 7篇 |
排序方式: 共有9572条查询结果,搜索用时 0 毫秒
111.
Serological surveillance for Tahyna virus (California encephalitis orthobunyavirus,Peribunyaviridae) neutralizing antibodies in wild ungulates in Austria,Hungary and Romania 下载免费PDF全文
J. V. Camp R. Haider D. Porea L. E. Oslobanu P. Forgách N. Nowotny 《Zoonoses and public health》2018,65(4):459-463
A serosurvey for Tahyna virus (TAHV), a mosquito‐borne California encephalitis orthobunyavirus (Peribunyaviridae) endemic to Europe, was performed to estimate the activity of TAHV on a broad geographic scale. Sera from wild boar (Sus scrofa), roe deer (Capreolus capreolus) and red deer (Cervus elaphus) were collected from Austria, Hungary and Romania. Samples were tested for neutralizing antibodies against TAHV using a virus microneutralization assay. The results demonstrate that TAHV transmission to mammals is widespread in Europe, particularly in the wild boar population where the mean rate of seroconversion is 15.2%. 相似文献
112.
Triston N. Hooks Geno A. Picchioni Brian J. Schutte Manoj K. Shukla David L. Daniel Jamshid Ashigh 《Strength and Conditioning Journal》2018,71(1):106-114
A better understanding of site-specific factors such as soil salinity that regulate plant invasions is needed. We conducted a 3-mo greenhouse study to evaluate the salinity responses of three local maternal sources of Lepidium alyssoides, which is an indigenous species shown to aggressively colonize disturbed shrubland sites in the southwestern United States, including those affected by high salinity and sodicity. Results indicated that there were little or no population effects on plant evapotranspiration (ET), growth, and tissue Na and Cl concentrations. Significant reductions in seedling growth and ET were largely independent of various isosmotic saline irrigation solutions that included NaCl, Na2SO4, and CaCl2, each at ? 0.1 MPa and ? 0.2 MPa, suggesting that ET and growth were controlled by solution osmotic potential. The combined Na and Cl concentrations in leaves were 9–10% of dry weight with no visible sign of injury. However, increasing leaf mortality and abscission as a proportion of total leaf production was observed in the high-salt treatments (? 0.2 MPa), with a combined Na and Cl concentration reaching 16% with high NaCl. Under saline conditions, considerable foliage salt loads of this species could deposit high-salt litter to potentially alter a landscape to its own favor and to the detriment of other salt-sensitive species. Results of this study add to a limited quantitative database on site-specific salinity factors governing plant invasions by showing the potential for these populations to behave invasively under saline conditions and, thus, potential for soil salinity assessment to predict incipient populations. However, due to its halophytic traits and indigenous status, L. alyssoides may alternatively provide ecosystem services to salinized shrublands of the arid and semiarid southwestern United States. 相似文献
113.
黄河三角洲地区野生牧草种质资源的初步研究 总被引:2,自引:0,他引:2
研究牧草种质资源,无论是对野生牧草种质的保存,鉴定,还是对培育利用用牧草建立人工草地,改良天然草地都有很大意义。本文为更好地发掘,利用野生牧草种质资源提供了一定的科学依据。 相似文献
114.
115.
116.
117.
C. Burri F. Vial M.‐P. Ryser‐Degiorgis H. Schwermer K. Darling M. Reist N. Wu O. Beerli J. Schöning M. Cavassini A. Waldvogel 《Zoonoses and public health》2014,61(8):537-544
Hepatitis E is considered an emerging human viral disease in industrialized countries. Studies from Switzerland report a human seroprevalence of hepatitis E virus (HEV) of 2.6–21%, a range lower than in adjacent European countries. The aim of this study was to determine whether HEV seroprevalence in domestic pigs and wild boars is also lower in Switzerland and whether it is increasing and thus indicating that this zoonotic viral infection is emerging. Serum samples collected from 2,001 pigs in 2006 and 2011 and from 303 wild boars from 2008 to 2012 were analysed by ELISA for the presence of HEV‐specific antibodies. Overall HEV seroprevalence was 58.1% in domestic pigs and 12.5% in wild boars. Prevalence in domestic pigs was significantly higher in 2006 than in 2011. In conclusion, HEV seroprevalence in domestic pigs and wild boars in Switzerland is comparable with the seroprevalence in other countries and not increasing. Therefore, prevalence of HEV in humans must be related to other factors than prevalence in pigs or wild boars. 相似文献
118.
119.
以甘肃省境内采集的4种野生早熟禾为材料,设8个pH处理(3、4、5、6、7、8、9、10),探讨土壤pH对其生理特性的影响机制以及适宜生长的土壤pH,以期为早熟禾属草坪的养护管理和野生早熟禾的引种驯化提供依据。结果表明,随pH增大,4种野生早熟禾相对膜透性,游离脯氨酸(F-Pro)、可溶性糖(SS)和丙二醛(MDA)含量及过氧化物酶(POD)活性均呈先减小后增大的趋势,可溶性蛋白(SP)含量和超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性均呈先增大后减小的趋势;草地早熟禾(Poa pratensis)、一年生早熟禾(P.annua)和小药早熟禾(P.micrandra)在pH为7时,硬质早熟禾(P.sphondylodes)在pH为6时受到的伤害最小,是其最适宜生长的pH。 相似文献
120.
Samuel D. Fuhlendorf Torre J. Hovick R. Dwayne Elmore Ashley M. Tanner David M. Engle Craig A. Davis 《Strength and Conditioning Journal》2017,70(1):9-14
Encroachment of Great Plains grasslands by fire-sensitive woody plants is a large-scale, regional process that fragments grassland landscapes. Using prairie grouse (Tympanuchus spp.) of conservation concern, we apply hierarchy theory to demonstrate how regional processes constrain lower-level processes and reduce the success of local management. For example, fire and grazing management may be locally important to conservation, but the application of fire and grazing disturbances rarely cause irreversible fragmentation of grasslands in the Great Plains. These disturbance processes cause short-term alterations in vegetation conditions that can be positive or negative, but from a long-term perspective fire maintains large tracts of continuous rangelands by limiting woody plant encroachment. Conservation efforts for prairie grouse should be focused on landscape processes that contribute to landscape fragmentation, such as increased dominance of trees or conversion to other land uses. In fact, reliance on local management (e.g., maintaining vegetation structure) to alter prairie grouse vital rates is less important to grouse population persistence given contemporary landscape level changes. Changing grass height, litter depth, or increasing the cover of forbs may impact a few remaining prairie-chickens, but it will not create useable space at a scale relevant to the historic conditions that existed before land conversion and fire suppression. 相似文献