全文获取类型
收费全文 | 2017篇 |
免费 | 104篇 |
专业分类
林业 | 51篇 |
农学 | 56篇 |
基础科学 | 3篇 |
336篇 | |
综合类 | 277篇 |
农作物 | 254篇 |
水产渔业 | 141篇 |
畜牧兽医 | 873篇 |
园艺 | 25篇 |
植物保护 | 105篇 |
出版年
2022年 | 24篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 26篇 |
2018年 | 49篇 |
2017年 | 48篇 |
2016年 | 47篇 |
2015年 | 45篇 |
2014年 | 57篇 |
2013年 | 95篇 |
2012年 | 103篇 |
2011年 | 136篇 |
2010年 | 62篇 |
2009年 | 57篇 |
2008年 | 99篇 |
2007年 | 107篇 |
2006年 | 65篇 |
2005年 | 79篇 |
2004年 | 71篇 |
2003年 | 73篇 |
2002年 | 53篇 |
2001年 | 34篇 |
2000年 | 44篇 |
1999年 | 37篇 |
1997年 | 22篇 |
1996年 | 16篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1992年 | 24篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1974年 | 17篇 |
1973年 | 23篇 |
1972年 | 18篇 |
1971年 | 14篇 |
1970年 | 18篇 |
1969年 | 19篇 |
1968年 | 12篇 |
1966年 | 11篇 |
排序方式: 共有2121条查询结果,搜索用时 46 毫秒
1.
AR RABIEE KL MACMILLAN F SCHWARZENBERGER D THALLER MJ RATHBONE TE TRIGG 《Australian veterinary journal》2001,79(10):690-694
OBJECTIVE: To evaluate the potential of an implant of a GnRH-agonist (deslorelin) to create a progesterone free animal suitable for studying progesterone (P4) metabolism in intact cows by measuring blood P4 and faecal P4 metabolites. METHODS: Experiment 1: Eighteen non-lactating cycling Holstein-Friesian cows, 4 to 7 years old, were allocated to one of three groups to study plasma P4 concentrations preceding an intravaginal insert. These groups comprised: i) a deslorelin group (GnRH-agonist implanted); ii) a PGF group receiving two injections of prostaglandin (PGF2alpha) 12 days apart; and, iii) an ovariectomised (OVX) group. An intravaginal device (CIDR) was inserted into the vagina of each animal and left in place for 11 days. Plasma P4 concentrations were measured during the study period. Experiment 2: Twelve non-lactating cycling Holstein-Friesian cows, 4 to 7 years old, were allocated to two groups: i) a deslorelin group (GnRH-agonist implanted); and ii) an ovariectomised group. Plasma P4 and faecal P4 metabolites (20-oxo-pregnanes, 20alpha-OH and 20beta-OH) were monitored for a period of 5 weeks. RESULTS: Experiment 1: Average plasma P4 concentration did not differ between the three groups (1.28, 1.43 and 1.55 ng/mL for deslorelin, OVX and PGF cows, respectively, P = 0.8) during the period of supplementation. Experiment 2: There was no difference in plasma P4 (mean plasma P4 < 0.02 ng/mL, P = 0.9) and faecal P4 metabolites between deslorelin and OVX cows 2 weeks after the implantation (P = 0.7). CONCLUSIONS: These data showed that a GnRH-agonist (deslorelin) implant may be used as an alternative to ovariectomy to create a progesterone free animal suitable for studying the metabolism of administered P4. 相似文献
2.
Michael J. A. Young Arlo W. Fast Paul G. Olin 《Journal of the World Aquaculture Society》1989,20(1):7-11
Chinese catfish ( Clarias fuscus ) were successfully spawned in Hawaii using human chorionic gonadotropin (HCG) at dosage rates of two and four international units (IU) per gram body weight. Fish not injected with HCG did not produce viable eggs. Successful spawns with HCG occurred between May and October. Hatch rates of up to 80% were obtained during June, July, and August for those fish given either a 2 or 4 IU per gram body weight injection of HCG. Fish spawned in either May or October yielded significantly higher hatch rates when injected with 4 rather than 2 IU per gram body weight. Fish held at elevated temperatures (28 to 30 C) prior to the normal spawning season developed significantly larger oocyte diameters, 60 days earlier than fish held under ambient temperature conditions (21.5 to 24 C). Photoperiod manipulation at ambient temperature conditions was associated with earlier oocyte maturation, but photoperiod effects were much less important than temperature. 相似文献
3.
Hemagglutination and hemagglutination inhibition of turkey red blood cells with Mycoplasma hyopneumoniae 总被引:2,自引:0,他引:2
T F Young B Z Erickson R F Ross Y Wannemuehler 《American journal of veterinary research》1989,50(7):1052-1055
The ability of Mycoplasma hyopneumoniae to agglutinate RBC was evaluated to develop an in vitro cytadsorption assay. Using swine RBC in a microtitration hemagglutination test, no agglutination or partial agglutination was detected. Comparison of RBC from various other species indicated that improved hemagglutination was obtained with RBC from turkeys. This hemagglutination was detected only when mycoplasma cells used in the assay had been frozen and thawed, heated at 50 C for 30 minutes, or treated with trypsin. Treatment of RBC with trypsin or neuraminidase enhanced hemagglutination. Possible surface lectin activity in M hyopneumoniae was evaluated by use of carbohydrates in a blocking assay; hemagglutination was not inhibited by any of 13 carbohydrates evaluated. Mycoplasma hyopneumoniae convalescent porcine serum and monoclonal antibodies against 2 M hyopneumoniae immunogens of molecular weights of 64,000 and 41,000 inhibited hemagglutination. 相似文献
4.
L.E. Young D.H. Bartram M. Diamond A. Gregg R.S. Jones 《Veterinary anaesthesia and analgesia》1991,18(Z1):171-174
5.
Four hundred and ninety horses were anaesthetised with halothane for clinical surgical or diagnostic procedures following induction with either detomidine/keta-mine, detomidine/thiopentone, xylazine/ketamine or guaiphenesin/thiopentone. Routine clinical monitoring was performed during anaesthesia. All horses developed hypotension (mean arterial pressures below 80 mm Hg) and respiratory depression (significant fall in respiratory rate and arterial carbon dioxide tension above 7 kPa (53 mm Hg)) consistent with the recognised effects of halothane. All anaesthetic procedures incorporating xylazine or detomidine resulted in lower pulse rates (28–35 per min) than after guaiphenesin/thiopentone (36–44 per min) and there was greater respiratory depression after techniques employing thiopentone rather than keta-mine. Development of hypotension was delayed after techniques using the α2 adrenoceptor agonist agents (xylazine and detomidine), particularly detomidine. Prernedication with acepromazine did not affect any of the physiological variables measured after techniques employing detomidine. Recovery to standing was fastest after xylazine/ketamine (31±1 min) and slowest after detomidine/thiopentone (53±2 min). Recovery quality was best after detomidine/thiopentone and all techniques employing an α2 adrenoceptor agonist agent resulted in smoother recovery than after guaiphenesin/thiopentone. This study demonstrates that most of the physiological effects of individual induction agents are overridden by the cardiovascular and respiratory depressant effects of halothane. The study also shows that detomidine is an acceptable sedative for use before general anaesthesia with halothane in horses. 相似文献
6.
Clark RG Henderson HV Hoggard GK Ellison RS Young BJ 《New Zealand veterinary journal》1987,35(8):126-133
Blood samples from 433 periparturient recumbent cows submitted by veterinary practitioners to Ruakura Animal Health Laboratory during 1983 and 1984 were analysed and results related to whether cows recovered, died or were euthanased. Generally cows were sampled only once and the time varied from 15 minutes to 20 days after becoming recumbent. During 1983 serum calcium, magnesium, phosphorus, creatine phosphokinase (CK), aspartate amino transferase (AST), glutamate dehydrogenase (GDH), gamma glutamyl transferase (GGT) were analysed. In 1984 serum urea, creatinine, fibrinogen and haematological examination (haemoglobin, haematocrit, total and differential white cell counts) were added to the panel. Overall 39% of cows recovered, 30% died and 32% were destroyed. Precalving cows had 111% more deaths and 7% less survivors than postcalving recumbent cows (P<0.1). There was little difference (3%) in euthanasia prevalence. Tests that were most useful in predicting a lack of recovery were serum urea and muscle enzymes. Using these tests and duration of recumbency when sampled a model was produced to predict the probability of recovery from 254 cases. 相似文献
7.
Fatty acid profiles and sensory and carcass traits of tissues from steers and swine fed an elevated monounsaturated fat diet 总被引:4,自引:0,他引:4
L C St John C R Young D A Knabe L D Thompson G T Schelling S M Grundy S B Smith 《Journal of animal science》1987,64(5):1441-1447
Twelve Angus X Hereford steers were assigned to either a control high-energy diet or a test diet consisting of 20% rapeseed at the expense of 20% corn. Twelve pigs were allotted to a control diet and two test diets containing either 10 or 20% canola oil (CO). Both CO and oil in the rapeseed contained 60 to 64% oleic acid. Cattle fed rapeseed exhibited little effect from the diet due to apparent indigestibility of the rapeseed. Total saturated fatty acids decreased from 40% in adipose tissue of the control pigs to 15% in the 20% CO-fed pigs. The ratio of monounsaturated to saturated fatty acids (M/S) increased from 1.19 in adipose tissue from control pigs to 3.63 with the addition of 20% CO to the diet. In muscle, the M/S ratio increased from 1.21 in control pigs to 2.46 in the 20% CO treatment group. The percentage of the saturated fatty acids in muscle decreased from 42% in the control to 23% in the 20% CO treatment. Significant increases in "oiliness" and decreases in fat firmness were observed when increasing levels of canola oil were fed. Sensory traits, cooking loss and shear-force values of pork chops were similar among treatment groups. In conclusion, monounsaturated fatty acid content can be elevated substantially in pork without adversely influencing the quality of the meat, thus producing a product perceived to be more healthful by the consumer. 相似文献
8.
9.
P Litwak W V Lumb A W Nelson S Young J P Bowman 《American journal of veterinary research》1978,39(9):1519-1524
Removal of the 2nd or 3rd lumbar vertebrae (or both) has been accomplished in the subhuman primate (Macaca mulatta). Variations between this animal and the dog in posture, vertebral column anatomy, and spinal cord blood supply made no apparent difference in the results when compared with those in previous experiments. All macaques were able to clinb and to use their hind legs in a normal manner within 3 days after surgical operation. Once hair had regrown over the surgical incision, persons not familiar with the animals were not able to identify the animals that had undergone surgical operation. If a single vertebra was removed, use of spinous process and a single vertebral body plate was sufficient to stabilize the vertebral column. Except for 1 rhesus macaque whose spinous process plates were removed 20 days after the operation, vertebral columns of macaques (n = 3) that underwent single spondylectomy healed in nearly normal alignment. With the removal of 2 lumbar vertebrae, the previously described stabilization procedure was not sufficient to prevent kyphotic deformity of the vertebral column. Spinous process plates from 1 macaque were removed after 64 days. However, all these macaques (n = 3) could climb and use their legs as well as others in the colony. 相似文献
10.
Scanning electron microscope study of Sendai virus fusion between HeLa cells and chick erythrocytes.
Chick erythrocytes were fused with HeLa cells by Sendai virus and preparations examined by scanning electron microscopy at different times after fusion. Heterokaryons were usually formed by fusion of erythrocyte ghosts with HeLa cells. Occasionally whole erythrocytes were engulfed but there was no evidence that free nuclei fused. Initial inter-cell attachments were usually, and possibly always, made at the site of an attached virus particle. This study helps to correlate topographical findings with previous two-dimensional studies with the transmission electron microscope and may also provide a model system for the fusion of parasitised erythrocytes with eukaryotic cells. 相似文献