全文获取类型
收费全文 | 1275篇 |
免费 | 95篇 |
国内免费 | 1篇 |
专业分类
林业 | 57篇 |
农学 | 13篇 |
基础科学 | 13篇 |
130篇 | |
综合类 | 194篇 |
农作物 | 50篇 |
水产渔业 | 53篇 |
畜牧兽医 | 729篇 |
园艺 | 14篇 |
植物保护 | 118篇 |
出版年
2019年 | 22篇 |
2018年 | 13篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 72篇 |
2012年 | 35篇 |
2011年 | 45篇 |
2010年 | 30篇 |
2009年 | 25篇 |
2008年 | 36篇 |
2007年 | 48篇 |
2006年 | 33篇 |
2005年 | 44篇 |
2004年 | 41篇 |
2003年 | 32篇 |
2002年 | 43篇 |
2001年 | 30篇 |
2000年 | 47篇 |
1999年 | 29篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 23篇 |
1994年 | 15篇 |
1993年 | 21篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 28篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1979年 | 22篇 |
1978年 | 13篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 14篇 |
1972年 | 16篇 |
1971年 | 15篇 |
1970年 | 10篇 |
1967年 | 15篇 |
1938年 | 10篇 |
排序方式: 共有1371条查询结果,搜索用时 62 毫秒
151.
A nerve fascicular biopsy technique that preserves the functional integrity of the parent nerve is reported in the dog. Fascicular biopsies from ulnar and peroneal nerves did not produce clinical sensory or motor deficits. Electrodiagnostic testing for the modalities of latency, duration, amplitude, and conduction velocities were not markedly altered after fascicular biopsies. Morphometric analysis of muscle fiber types, delineated by histochemic techniques, revealed no statistical (P greater than 0.05) difference between muscles from biopsied or control limbs. Fascicular biopsies resulted in small neuromas in all dogs. 相似文献
152.
153.
The persistence of the herbicide 2,4,5-T was studied at different controlled temperatures and moisture levels in Regina heavy clay. Degradation approximated to first-order kinetics and the half-life varied from about 4 days at 35°C and 34% soil moisture to about 60 days at 10°C and 20% soil moisture. The laboratory data were used in conjunction with the appropriate measurements of surface soil temperature and moisture content in the field to simulate the degradation pattern for the herbicide in five separate micro-plot experiments. Satisfactory agreement with the observed patterns of loss was obtained in two of the experiments but in the other three, the model over-estimated rates of loss. It is suggested that the reason for this was the difficulty of obtaining a correct measure of soil moisture content to use in the simulation program. 相似文献
154.
Neutrophil mediated and IgA dependent antibacterial immunity against enteropathogenic Escherichia coli in the porcine intestinal mucosa 总被引:1,自引:0,他引:1
The role of polymorphonuclear neutrophils (PMN) in the antibacterial immunity against enteropathogenic Escherichia coli (EEC) 0:149 in the porcine intestine was studied using intestinal Thiry-Vella loop (T-V loop) as a model. Intraluminal immunizations of T-V loops resulted in elevated levels of immunoglobulin A (IgA) anti-EEC 0:149 antibody in the loop secretions, an infiltration of PMN in the lumen of the loops and an increase in the concentrations of lactoferrin (LF), lysozyme (LY), cationic proteins (CP), and a specific bactericidal response in the immunized loops. PMN were observed by electron microscopy (EM) to be actively phagocytic in the lumen of the immune loops. EM observations of loop fluids as well as the abrogating effect of iron on the in vivo bactericidal response strongly suggest that the pMN played an important role in the bactericidal response in the loops against EEC. In addition to phagocytosis by PMN and subsequent intracellular killing, disintegration of PMN in the lumen of the loops and extracellular killing of EEC by the antibacterial products of PMN such as LF, LY and CP, with and/or without synergistic effect of IgA antibodies, also contribute to the bactericidal response of the immunized loops. 相似文献
155.
K Sato T E Carpenter J T Case R L Walker 《Journal of veterinary diagnostic investigation》2001,13(3):206-212
Electronic records from the California Animal Health and Food Safety Laboratory System between January 1, 1991, and June 30, 1998, were reviewed, and data on 593 Salmonella serotypes isolated from feces or intestinal contents of adult dairy cattle with diarrhea were analyzed to determine spatial and temporal clustering. A statistically significant clustering in space was detected with 10 (Typhimurium, Montevideo, Muenster, Anatum, Give, Menhaden, Kentucky, Agona, Derby, and Newport) of the 13 serotypes examined. Significant temporal clustering was also detected with 10 serotypes (Typhimurium, Montevideo, Muenster, Anatum, Give, Newbrunswick, Menhaden, Kentucky, Derby, and Newport). Six serotypes (Anatum, Menhaden, Montevideo, Muenster, Newbrunswick, and Newport) were significantly spatially and temporally clustered. A difference in temporal and spatial distribution patterns of some serotypes associated with diarrhea in adult dairy in California was found. Knowledge of the specific type of clustering, if present, should improve our understanding of the transmission and control of salmonellosis in the field. 相似文献
156.
157.
158.
Intertrochanteric femoral osteotomy 总被引:1,自引:0,他引:1
159.
Heart rate, blood velocity, volumetric blood flow, and arterial diameter for 10 horses given acetylpromazine were determined from measurements of the dorsal metatarsal artery 3 (the great metatarsal artery), using 2-dimensional real-time and gated pulsed Doppler ultrasonography. Acetylpromazine induced significant increases in arterial diameter (P less than 0.01) and volumetric flow rate (P less than 0.05)--all compatible with adrenergic blockade. There was a trend indicating that there was increased blood velocity. Heart rate was unchanged. 相似文献
160.
Nicholas H. Anderson Sarah K. Branch R. S. Thomas Loeffler Brian E. Mann Ian W. Nowell Philip E. Walker 《Pest management science》1984,15(3):310-316
The crystal structures of a number of fungicidal azolylmethanes are compared. In the benzyl compounds [1-aryl-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ones, the corresponding pentan-3-ols, and 1-(4-chlorophenyl)-3-(2-fluorophenyl)-2-(1,2,4-triazol-1-yl)propan-1-one], the benzyl and tert-butyl groups (or 4-chlorophenyl group) are trans, whereas in the analogous phenoxy compounds [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)butan-2-one and the corresponding butan-2-ol], the tert-butyl groups are trans to the triazole and gauche to the phenoxy group. Coupling constants, determined by nuclear magnetic resonance (n.m.r.) spectroscopy, suggest that for some compounds there is one dominant solution conformation. Intramolecular hydrogen bonding, observed by infrared spectroscopy in two of the compounds, supports the findings by n.m.r. For some compounds, the crystal and solution conformations appear to be very similar, whereas in others they are quite different. Published data on the relative activity of the enantiomers of the benzyl- and phenoxy-compounds are discussed, but differences in the relative activity of enantiomers in the two series cannot be readily rationalised. It is concluded that different enantiomers may have different modes of binding at the active site. 相似文献