全文获取类型
收费全文 | 129663篇 |
免费 | 7033篇 |
国内免费 | 131篇 |
专业分类
林业 | 5442篇 |
农学 | 3712篇 |
基础科学 | 732篇 |
14594篇 | |
综合类 | 23718篇 |
农作物 | 4898篇 |
水产渔业 | 5980篇 |
畜牧兽医 | 68471篇 |
园艺 | 1534篇 |
植物保护 | 7746篇 |
出版年
2018年 | 1841篇 |
2017年 | 1957篇 |
2016年 | 1722篇 |
2015年 | 1586篇 |
2014年 | 1930篇 |
2013年 | 4924篇 |
2012年 | 3529篇 |
2011年 | 4310篇 |
2010年 | 2713篇 |
2009年 | 2818篇 |
2008年 | 4172篇 |
2007年 | 3991篇 |
2006年 | 3761篇 |
2005年 | 3440篇 |
2004年 | 3351篇 |
2003年 | 3454篇 |
2002年 | 3210篇 |
2001年 | 3764篇 |
2000年 | 3818篇 |
1999年 | 3049篇 |
1998年 | 1253篇 |
1997年 | 1221篇 |
1995年 | 1357篇 |
1994年 | 1214篇 |
1993年 | 1239篇 |
1992年 | 2552篇 |
1991年 | 2862篇 |
1990年 | 2690篇 |
1989年 | 2682篇 |
1988年 | 2436篇 |
1987年 | 2459篇 |
1986年 | 2564篇 |
1985年 | 2532篇 |
1984年 | 1984篇 |
1983年 | 1789篇 |
1982年 | 1201篇 |
1979年 | 1910篇 |
1978年 | 1505篇 |
1977年 | 1368篇 |
1976年 | 1285篇 |
1975年 | 1389篇 |
1974年 | 1764篇 |
1973年 | 1747篇 |
1972年 | 1739篇 |
1971年 | 1613篇 |
1970年 | 1632篇 |
1969年 | 1507篇 |
1968年 | 1362篇 |
1967年 | 1355篇 |
1966年 | 1192篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
J B Herrick 《Journal of the American Veterinary Medical Association》1992,201(12):1854-1855
13.
Rostral and caudal rhinoscopy in dogs and cats facilitates the investigation of the nasal cavity and accurate biopsy. Rostral rhinoscopy can be performed by rigid endoscopes; caudal rhinoscopy requires flexible endoscopes. Deep anaesthesia or additional analgesia with local anaesthesia is necessary. The nasal cavity is assessed by its form, colour, surface of the mucous membrane, hyperemia, plaques, lesions, and the secretion is assessed by its quantity, colour and viscosity. Foreign bodies and neoplasia must also be looked for. Case reports with abnormal findings are described. 相似文献
14.
A technique is described for biopsy of the bovine udder, employing sedation and local anaesthesia. Tissue samples of approximately 5 g were obtained by electrocautery from two quarters of the udder of a cow laterally recumbent. Care was taken to ensure complete haemostasis which was achieved by electrocoagulation and ligation. Postoperative recovery was rapid, and loss of yield was no greater in biopsied glands than in control glands of the same cow. Yield from all quarters returned to preoperative levels within 48 h. 相似文献
15.
Abstract. In field and laboratory experiments the conditioner‘Agri-SC’has shown improvements in the structure of loamy sand soils in east Shropshire, UK. It resulted in statistically significant decreases in soil bulk density values and increases in soil porosity and aggregate stability. Further experiments are in progress on both loamy sand and silt loam soils. 相似文献
16.
Nephrogenic diabetes insipidus is characterized by polyuria, hyposthenuria and compensatory polydipsia. With conventional clinical and laboratory examinations the diagnosis can be established and the differential diagnostic diseases excluded. In order to verify the diagnosis, differentiate the condition from central and nephrogenic diabetes insipidus and rule out psychogenic polydipsia, additional laboratory studies are required: of these, the concentration test, modified Carter-Robbins test and AVP stimulation test are described. 相似文献
17.
The horses studied were of the Swiss Warmblood breed and most were ELA-typed to assess a possible association of dermal hypersensitivity to insect bites with the major histocompatibility complex. Firstly, the occurrence of the condition was examined in 304 half-siblings sired by six stallions (A to F). Fourteen cases of dermal hypersensitivity were recognized and all were in the 153 offspring of Stallions C, E and F. Most animals of this group were also investigated for chronic hypersensitivity bronchitis: none of the sires displayed clinical signs of dermal hypersensitivity, but Stallions D, E and F were affected by chronic bronchitis. Among the animals investigated for both conditions only one horse showed coincidence of the two diseases as can be expected when the diseases are not correlated. The frequency of manifest dermal hypersensitivity and/or chronic hypersensitivity bronchitis varied in the half-sibling groups of individual sires. These findings suggest that the allergic conditions are independent entities. Secondly, the occurrence of dermal hypersensitivity was studied in three generations of horses at a stud at which Stallion C had exerted a particularly strong influence. A total of 302 animals, all born and raised at this stud, were surveyed over a period of 12 years. The descendants of Stallion C showed a significantly higher incidence (P less than 0.01) of dermal hypersensitivity (two daughters out of 19; eight second generation offspring out of 103; one third generation offspring out of 85) than did the controls of the same age classes but unrelated to Stallion C at the same stud (0 out of 95).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
18.
Plasma triglyceride concentration during intravenous infusions of propofol and Intralipid in sheep 总被引:1,自引:0,他引:1
B. M. Q. Weaver D. Raptopoulos † G. E. Staddon W. W. Mapleson‡ 《Veterinary anaesthesia and analgesia》1996,23(1):15-19
Plasma triglyceride concentrations were measured in sheep given Intralipid or propofol, which is carried in a vehicle very similar to 10% Intralipid. A bolus dose was administered followed immediately by an infusion of the same agent for 2 h. In the animals that received propofol, the measured concentration increased by a mean amount of 3.39 mmol/l when the infusion rate was l ml/min (Group Pl) and by 7.13 mmol/l when it was 2 ml/min (Group P2). When 10% Intralipid was administered and infused at 1 ml/min (Group I10), the measured concentration increased only by 0.95 mmol/l. One hour after stopping the infusion, the excess of measured concentration over baseline had decreased in the Pl and I 10 groups to 0.52 and 0.13, respectively, of the corresponding maximum excess. The method adopted for measuring plasma triglycerides is widely used in hospitals; however, an incidental observation revealed that it is inappropriate in the presence of injections of propofol or Intralipid. Despite this, evidence and argument are presented to support the conclusion that, with propofol, plasma triglyceride concentrations increased more rapidly during the infusions and returned to baseline more slowly than with a corresponding amount of Intralipid. 相似文献
19.
The anthelmintic efficacy of abamectin (avermectin B1) was evaluated against gastrointestinal nematodes, including Ostertagia ostertagi inhibited larvae and lungworm, in yearling crossbred beef heifers during late spring. The calves were grazed on contaminated pasture for 10 weeks and then held under conditions free of nematode infection for 3 weeks prior to allotment and treatment on 5 June. Thirteen calves were randomly assigned to two groups of six by restricted randomization on body weights; the extra lightest calf was assigned to the non-treated control group. Group 1 calves were treated with abamectin at 200 micrograms kg-1 body weight by s.c. injection and Group 2 calves were not treated; all were killed at 14 days after treatment. Ostertagia ostertagi was present in all controls; arithmetic mean numbers of adults, developing fourth stage larvae (L4) and inhibited EL4 were 7683, 605 and 36,102, respectively. Other nematode genera present in controls in sufficient numbers for the experiment were Haemonchus placei adults, Trichostrongylus axei adults, Cooperia spp. adults, Oesophagostomum radiatum adults, Bunostomum phlebotomum adults, Dictyocaulus viviparus adults and E5 (immature adults). Abamectin was highly effective (consistently greater than 99% efficacy and P less than 0.05) in removing all nematodes present in treated calves as represented in non-treated controls, including the primary target of Ostertagia ostertagi inhibited EL4. The lowest efficacy was 93.8%, against D. viviparus E5. 相似文献
20.
S. Leibovitch B. L. Ma Wanga E. Maloba D. L. Smith 《Journal of Agronomy and Crop Science》1992,169(3):209-215
Aspects of intensive management practices such as high-yielding cultivars, narrow-row spacings and fungicide treatments could potentially increase cereal yields in regions with a short crop-growing season and occasionally dry and hot weather. A field experiment was carried out at McGill University, Canada for three years (1987 to 1989) to test the effects of triadimefon (1-[4-chlorophenoxy]-3,3-dimethyl-1-[1H-1,2,4-triazol-1-yl]-2-butanone, or Bayleton, a trade name) fungicide (0 vs. 140 g a.i. ha−1 ) and row spacing (10 vs. 20 cm) on the yield components, yield and other agronomic traits (spike emergence, days to maturity, leaf disease and plant height) of spring barley ( Hordeum vulgare L.) cv. Cadette, Laurier and Leger. A cultivar by row spacing interaction resulted in a 11 to 13.5 % increase in grain yield due to narrow rows for Laurier in two out of the three years and up to 16 % for Leger in one year. Over the three years grain yields were on average increased 6 to 12 % due to use of the narrower row spacing. Fungicide application to barley at the early heading stage effectively controlled leaf diseases without influence on yield components or grain yield. Our results indicate that some components of intensive management such as narrow row spacing can be applicable in regions with a short crop-growing season. 相似文献