全文获取类型
收费全文 | 212篇 |
免费 | 18篇 |
专业分类
林业 | 1篇 |
基础科学 | 1篇 |
29篇 | |
综合类 | 83篇 |
农作物 | 2篇 |
水产渔业 | 4篇 |
畜牧兽医 | 105篇 |
园艺 | 1篇 |
植物保护 | 4篇 |
出版年
2021年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 10篇 |
2016年 | 4篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1968年 | 5篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1946年 | 1篇 |
1940年 | 1篇 |
1939年 | 1篇 |
1937年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 15 毫秒
31.
32.
The rates of nucleation of liquid aerosols from the gaseous mixtures H2SO4 + H2O and HNO3 + H2O at 25°C for various relative humidities (10 to 100%) and various activities of acid vapor are calculated using the Flood-Neumann-Döring-Reiss-Doyle theory of binary homogeneous nucleation. The activities of acid vapor needed for nucleation are 25 to 300 times smaller for H2SO4 + H2O than for HNO3 + H2O. This is due to the much larger free energy of mixing in the liquid phase for H2SO4 + H2O. Conversion from activities to actual pressures leads to concentrations of HNO3 which are much too high to be found under normal atmospheric conditions. On the other hand, the concentrations of H2SO4 vapor needed to nucleate droplets in the H2SO4 + H2O system are in the range 4(10?5) to 1.3 (10?2) ppm, a concentration which can result from photo-oxidation of SO2 in the atmosphere. Calculations are made of the growth curves for H2SO4 + H2O droplets (radius vs composition) at various relative humidities from the critical size radius up to a 1000 Å radius, corresponding to nuclei large enough to serve as condensation centers for heterogeneous nucleation. The limitations of binary homogeneous nucleation theory at extremely low concentrations of one of the components are discussed and it is shown that this theory becomes inapplicable if the actual vapor pressure of one component is below 10?6 torr. 相似文献
33.
34.
Nonsteroidal anti-inflammatory drugs impair platelet aggregation and secretion in man, pigs, and rabbits and inhibit platelet thromboxane/prostaglandin synthesis. The present investigation studied the effects of phenylbutazone on platelet aggregation and bleeding times in the horse. Aggregation responses to adenosine diphosphate and collagen were markedly impaired 15 minutes and 2 hours after treatment, but 4 hours after treatment, platelet responses approximated those prior to treatment. The in vivo effect of phenylbutazone correlated with its plasma concentrations. Phenylbutazone, like aspirin, appeared to exert its effect by inhibiting thromboxane/prostaglandin synthesis, because thrombin-induced malondialdehyde formation was inhibited. However, unlike aspirin, free arachidonate-induced malondialdehyde synthesis was reduced but not eliminated, which suggested that phenylbutazone may have more than one site of action. Although collagen-induced platelet aggregation was impaired, a response was still present, and bleeding times were not altered by phenylbutazone treatment. To account for these findings, it is proposed that equine platelets can respond to collagen by thromboxane/prostaglandin independent pathways. The physiologic and pathophysiologic importance of these findings is discussed. 相似文献
35.
36.
An enzyme-linked immunosorbent assay (ELISA) was developed for the serodiagnosis of contagious equine metritis (CEM), a sexually transmitted disease caused by Taylorella equigenitalis. Antigen preparation was simple, and antigens derived from both classical and atypical forms of T. equigenitalis enabled detection of antibody responses elicted in horses experimentally exposed to either form of the bacterium. Sera serially obtained from these horses from 0 to 63 days postexposure were tested by the traditional complement fixation test (CFT) for CEM and with the ELISA, using both antigens separately. There was close agreement between CFT and ELISA methodologies during the postexposure time period used to detect CEM serodiagnostically in regulatory animal health testing programs. Unlike the CFT, which requires an overnight incubation step, the ELISAs are more convenient and can be completed in 3 hours. 相似文献
37.
The objective of this study was to determine the effect of postweaning exposure to females on the subsequent sexual performance of young rams. Twenty-five crossbred rams were reared in a group with ovariectomized females from 4.5 to 9 mo of age. Ewes were brought into estrus every 2 wk during this period. A companion group of 23 crossbred rams was not exposed to females following weaning. Four 30-min sexual performance tests were administered at 10 mo of age. Rams reared with males and females (RMF) exhibited more mounts (P less than .001) and more ejaculations (P less than .002) than rams reared only with males (RM). The frequency of successful matings by the latter group did not increase with experience. Nine rams were sexually inactive in the sexual performance tests. Follow-up tests revealed that two of the RMF rams and one RM ram developed and maintained a sexual preference for males. The six remaining rams eventually mated with females when tested in familiar pens and subsequently exhibited normal levels of sexual performance even when tested in an unfamiliar enclosure. Exposure to ewes during the postweaning prepubertal period enhanced sexual performance. However, early exposure to females did not ensure that all males developed sexual preferences for females. The environmental context in which sexual performance tests are administered may inhibit the expression of heterosexual behavior in a small percentage of animals. After heterosexual behavior was expressed, the rams continued to show normal levels of sexual performance.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
38.
39.
TS Gaggini J Perin LS Arend ML Bernardi I Wentz FP Bortolozzo 《Reproduction in domestic animals》2013,48(3):390-395
This study investigated the effect of altrenogest treatment on the farrowing development of sows, and birth weight (BW) and piglet survival until the third day of life. Three control groups were used: (i) sows that farrowed spontaneously before 114 day of gestation (CONT <114); (ii) sows that spontaneously farrowed at ≥114 day of gestation (CONT ≥114); (iii) sows that farrowed at ≥114 day with cloprostenol treatment (CONTCLOPR). Other sows were treated with altrenogest (Regumate®) for 3 days (days 111, 112 and 113 of gestation): one group gave birth spontaneously (ALT) and the other group received altrenogest until day 113 and cloprostenol on day 114 (ALTCLOPR). There were no differences (p > 0.05) in farrowing duration, BW, coefficient of variation (CV) of BW, stillborn piglets, mummified foetuses, percentage of light piglets and survival until Day 3 between sows with and without cloprostenol treatment, in both control (CONT ≥114 vs CONTCLOPR) and altrenogest‐treated sows (ALT vs ALTCLOPR). Further comparisons were performed taking into account three groups: sows with early delivery (CONT <114 – farrowing before 114 days of gestation; n = 56), sows with longer gestation (CONT ≥114 – with and without cloprostenol treatment sows; n = 103) and ALT sows (with and without cloprostenol treatment; n = 105). Gestation length of CONT ≥114 and ALT sows was similar (p > 0.05), but higher than in CONT <114 sows. There were no differences (p > 0.05) between groups in farrowing duration, CV of BW, and percentages of stillborn piglets and mummified foetuses. Sows of CONT <114 group had a larger litter size and a lower BW than sows of the other two groups (p < 0.05). Sows of CONT <114 group had a higher percentage of lighter piglets and a lower piglet survival rate (p < 0.05) than ALT sows. In conclusion, altrenogest treatment proved to be an efficient method to avoid early parturition in 3–5 parity sows resulting in heavier piglets at birth. 相似文献
40.
Intravaginal impedance (IVI) fluctuates during the goat estrous cycle. To understand which ovarian steroids are responsible for IVI changes and whether IVI variations are associated with precopulatory and copulatory behaviors, 8 ovariectomized females were assigned to 4 treatments in a 4 x 4 Latin square replicated over four 8-d periods. The treatments were as follows: progesterone plus estradiol-17beta (P4 + E2), oil plus estradiol-17beta (E2), progesterone plus oil (P4), or oil (OIL). Daily IVI measurements at the vagino-cervical junction were taken at 1 and 70 KHz. Progesterone was given on d 2 and 3. Estradiol was given in the evening of d 5. On d 1 to 8, goats were group-exposed to a sexually experienced male and observed for the expression of sexual behaviors. On d 6 and 7, IVI was less when goats received P4 + E2 or E2 compared with goats given P4 or OIL (P < 0.05). Impedance measured at 1 kHz tended to remain lower on d 8 in P4 + E2-treated females compared with those given P4 or OIL (P < 0.055). Like previous results, P4 + E2 or E2 treatment induced behavioral estrus; 5 of 8 P4 + E2-treated and 5 of 8 E2-treated females were sexually receptive on d 6. On d 7, although IVI remained low and 2 of 8 P4 + E2-treated goats and 4 of 8 E2-treated goats remained sexually receptive, no additional females were in estrus. No IVI decreases and no estrous behavior were observed in goats given P4 or OIL. This experiment demonstrated that E2 initiates the periestrous drop in IVI, and P4 may delay baseline return. 相似文献