全文获取类型
收费全文 | 86849篇 |
免费 | 3987篇 |
国内免费 | 34篇 |
专业分类
林业 | 6725篇 |
农学 | 3743篇 |
基础科学 | 604篇 |
11364篇 | |
综合类 | 12144篇 |
农作物 | 4657篇 |
水产渔业 | 5381篇 |
畜牧兽医 | 37758篇 |
园艺 | 1950篇 |
植物保护 | 6544篇 |
出版年
2018年 | 3662篇 |
2017年 | 3716篇 |
2016年 | 2180篇 |
2015年 | 976篇 |
2014年 | 1163篇 |
2013年 | 2646篇 |
2012年 | 2821篇 |
2011年 | 4517篇 |
2010年 | 3710篇 |
2009年 | 2930篇 |
2008年 | 3842篇 |
2007年 | 3883篇 |
2006年 | 2374篇 |
2005年 | 2230篇 |
2004年 | 2305篇 |
2003年 | 2325篇 |
2002年 | 2102篇 |
2001年 | 2373篇 |
2000年 | 2419篇 |
1999年 | 1932篇 |
1998年 | 915篇 |
1997年 | 822篇 |
1996年 | 782篇 |
1995年 | 862篇 |
1994年 | 845篇 |
1993年 | 781篇 |
1992年 | 1528篇 |
1991年 | 1545篇 |
1990年 | 1665篇 |
1989年 | 1516篇 |
1988年 | 1460篇 |
1987年 | 1345篇 |
1986年 | 1389篇 |
1985年 | 1337篇 |
1984年 | 1133篇 |
1983年 | 1030篇 |
1982年 | 629篇 |
1979年 | 1011篇 |
1978年 | 798篇 |
1977年 | 724篇 |
1976年 | 678篇 |
1975年 | 719篇 |
1974年 | 771篇 |
1973年 | 835篇 |
1972年 | 809篇 |
1971年 | 752篇 |
1970年 | 734篇 |
1969年 | 748篇 |
1967年 | 661篇 |
1966年 | 633篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
Equivalent salt solution series have been previously defined as solutions with combinations of sodium absorption ratio (SAR) and electrolyte concentration (Ec) producing the same extent of clay swelling in a given soil. The present study shows that there is a high (r2>0.96) positive correlation between log Ec and log SAR of equivalent salt solutions series, in the equation: where a1 and b1 are constants for each equivalent salt solution series for a given soil. Log a1 could also be represented as a linear function of b1 resulting in the equation: where a2 and b2 are constants for a given soil. Solving this equation using any given value of b1 yields the combinations of SAR and Ec which make up each equivalent salt solution series for a given soil. The relationship between log a1 and b2 for three soils from western United States, namely Waukena, Pachappa and Grangeville, was similar, with their combined data having a r2 value of 0.96. This indicated that a single set of equivalent salt solution series values could be used for these three soils which have different clay contents and clay mineralogy. Prediction of hydraulic conductivity decreases with Ec reduction at given values of SAR in red-brown and alluvial soils from southern Tasmania, using the equivalent salt solution series values for Waukena soil, showed similar patterns to measured values and also to those predicted using the equivalent salt solution values applicable to the respective Tasmanian soils. Thus, available data indicate that the same set of equivalent salt series could be applied to the five soils studied. If further testing shows that a single set of equivalent salt solutions values could be applied to all or large groups of soils, this would facilitate the application of the equivalent salt solution concept to predict salt solution flow in the field. 相似文献
103.
104.
Vagelos P 《Science (New York, N.Y.)》1991,252(5009):1080-1084
105.
106.
Lavoie JP Couture L Higgins R Laverty S 《The Canadian veterinary journal. La revue veterinaire canadienne》1991,32(5):292-294
Bacterial isolations were reviewed from equine trachea, guttural pouch, uterus, wounds, abscesses, blood, synovial fluid, and abdominal fluid submitted to the Clinical Bacteriology Laboratory of the School of Veterinary Medicine at the University of Montreal for aerobic bacterial culture from 1986 to 1988. Of the 733 samples submitted, 324 (44%) were positive for bacterial growth, and 233 antimicrobial sensitivity tests were performed. Seventy-six percent of all positive samples yielded one bacterial species and two were isolated from 22% of positive samples. Streptococcus zooepidemicus, Escherichia coli, and Actinobacillus spp. were isolated from 39%, 18%, and 15% of the samples, respectively.
Bacterial growth was most common from guttural pouches, wounds and abscesses, and transtracheal washes (TTW), but was less common from uterus, blood, abdominal fluid, and synovial fluids. Streptococcus zooepidemicus was the most common bacterium recovered from guttural pouches, TTW, uterus, and wounds and abscesses. Escherichia coli predominated in abdominal fluids, blood, and synovia. Bacterial sensitivities to common antimicrobials are presented.
相似文献107.
108.
109.
Equine polymorphonuclear (PMN) and mononuclear (MN) leucocytes were separated on Percoll gradients and used to study the chemoattractant properties of the polar ether-linked phospholipid, platelet activating factor (PAF). Six concentrations of PAF ranging from 1 ng/ml to 100 g/ml were studied in each of two in vitro assay systems, the agarose microdroplet and a microfilter technique. Very significant (p<0.01) increases in the movement of both PMN and MN cells were obtained with most concentrations of PAF. In two instances there was no apparent concentration-response relationship, although the action of PAF was approximately bell-shaped in two others. The possible significance of these findings for equine inflammatory conditions is discussed. 相似文献
110.