全文获取类型
收费全文 | 67108篇 |
免费 | 3781篇 |
国内免费 | 811篇 |
专业分类
林业 | 3104篇 |
农学 | 2748篇 |
基础科学 | 825篇 |
7729篇 | |
综合类 | 12617篇 |
农作物 | 2463篇 |
水产渔业 | 3140篇 |
畜牧兽医 | 33969篇 |
园艺 | 963篇 |
植物保护 | 4142篇 |
出版年
2021年 | 718篇 |
2020年 | 682篇 |
2019年 | 834篇 |
2018年 | 1095篇 |
2017年 | 1193篇 |
2016年 | 1056篇 |
2015年 | 1127篇 |
2014年 | 1160篇 |
2013年 | 2960篇 |
2012年 | 2082篇 |
2011年 | 2473篇 |
2010年 | 1686篇 |
2009年 | 1633篇 |
2008年 | 2277篇 |
2007年 | 2160篇 |
2006年 | 2016篇 |
2005年 | 1832篇 |
2004年 | 1643篇 |
2003年 | 1653篇 |
2002年 | 1591篇 |
2001年 | 1947篇 |
2000年 | 1918篇 |
1999年 | 1613篇 |
1998年 | 771篇 |
1997年 | 714篇 |
1995年 | 765篇 |
1994年 | 693篇 |
1993年 | 653篇 |
1992年 | 1289篇 |
1991年 | 1435篇 |
1990年 | 1311篇 |
1989年 | 1302篇 |
1988年 | 1197篇 |
1987年 | 1159篇 |
1986年 | 1202篇 |
1985年 | 1198篇 |
1984年 | 965篇 |
1983年 | 902篇 |
1979年 | 893篇 |
1978年 | 702篇 |
1977年 | 694篇 |
1976年 | 711篇 |
1975年 | 715篇 |
1974年 | 866篇 |
1973年 | 842篇 |
1972年 | 812篇 |
1971年 | 728篇 |
1970年 | 770篇 |
1969年 | 734篇 |
1967年 | 656篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Endogenous ionic currents traverse intact and damaged bone 总被引:1,自引:0,他引:1
R B Borgens 《Science (New York, N.Y.)》1984,225(4661):478-482
Living bone drives an electric current through itself and into sites of damage. Such "fracture currents" consist of two components: an intense, decaying current dependent on bone deformation and a stable, persistent current driven by a cellular battery. The latter is carried by chloride ions and, to a lesser extent, by sodium, magnesium, and calcium ions. Endogenous fracture currents are of the same polarity and similar magnitude as clinically applied currents that are successful in treating chronic nonunions in fractured bones. This suggests that the defect in biological nonunions may reside in the electrophysiology of repair. 相似文献
152.
Borkowska B 《Tree physiology》1986,1(3):303-307
Micropropagation of fruit trees results in the early onset of dormancy in the young plantlets. Prechilling of shoot cultures of sour cherry cvs Schattenmorelle and North Star at 4 degrees C for 6-8 weeks prolonged shoot extension of the plantlets but longer cold treatments adversely affected shoot growth and survival. Chilling of cultures had no affect on rhizogenesis. No significant influence of ABA, GA(3) or ABA + GA(3) was observed on root development. Gibberellic acid A(3) did not stimulate extension of the shoots, but when supplied together with ABA, it significantly decreased both shoot extension and the number of actively growing apices of plantlets of cv Schattenmorelle. The combined hormonal treatment had no effect on plantlets of the North Star cv. 相似文献
153.
B C Flann B A Lodge 《Journal of the Association of Official Analytical Chemists》1986,69(6):1026-1030
The validation of a liquid chromatographic procedure suitable for the determination of calcitriol and alfacalcidol in their respective formulations labeled to contain at least 0.25 micrograms drug per unit is described. The capsule content is diluted and chromatographed in 15-20 min on silica columns (5 micron) with a mobile phase of hexane-tetrahydrofuran-methylene dichloride-isopropanol (72 + 12 + 12 + 4, v/v) with detection at 254 nm. The calibration curve is linear. Recoveries of "spikes" averaged 101% with a standard deviation of 2%. Precision was better than 1.5%. 相似文献
154.
155.
156.
157.
On a property in the Nelson District, blood and urine samples were taken from red deer (Cervus elaphus) from which low (<1:100) antibody titres to serovar copenhageni and suspected leptospiral abortions had previously been reported. A total of 27 hinds were sampled. Microscopic agglutination test (MAT) titres in sera ranging from 1:32 to 1:128 were found in six animals. Thirteen leptospiral isolations were made from nine of the 27 urine samples. Four of these were typed as copenhageni and nine as hardjo. Two cultures were prepared from each urine sample and hardjo and copenhageni were both isolated from single urine samples from two animals. None of the 27 deer had serum MAT titres at 1:32 or above to copenhageni. 相似文献
158.
159.
160.
Bolt BA 《Science (New York, N.Y.)》1985,228(4701):848-849