全文获取类型
收费全文 | 135636篇 |
免费 | 7785篇 |
国内免费 | 70篇 |
专业分类
林业 | 5576篇 |
农学 | 4644篇 |
基础科学 | 862篇 |
17483篇 | |
综合类 | 18956篇 |
农作物 | 5087篇 |
水产渔业 | 7090篇 |
畜牧兽医 | 72970篇 |
园艺 | 1798篇 |
植物保护 | 9025篇 |
出版年
2020年 | 1171篇 |
2019年 | 1410篇 |
2018年 | 2229篇 |
2017年 | 2489篇 |
2016年 | 2295篇 |
2015年 | 1999篇 |
2014年 | 2451篇 |
2013年 | 5731篇 |
2012年 | 4350篇 |
2011年 | 5163篇 |
2010年 | 3502篇 |
2009年 | 3548篇 |
2008年 | 5152篇 |
2007年 | 4970篇 |
2006年 | 4641篇 |
2005年 | 4262篇 |
2004年 | 4109篇 |
2003年 | 4174篇 |
2002年 | 3808篇 |
2001年 | 4773篇 |
2000年 | 4641篇 |
1999年 | 3747篇 |
1998年 | 1471篇 |
1997年 | 1452篇 |
1996年 | 1341篇 |
1995年 | 1599篇 |
1994年 | 1327篇 |
1993年 | 1359篇 |
1992年 | 2762篇 |
1991年 | 2901篇 |
1990年 | 2866篇 |
1989年 | 2897篇 |
1988年 | 2610篇 |
1987年 | 2592篇 |
1986年 | 2539篇 |
1985年 | 2400篇 |
1984年 | 1956篇 |
1983年 | 1715篇 |
1982年 | 1154篇 |
1979年 | 1649篇 |
1978年 | 1284篇 |
1977年 | 1135篇 |
1976年 | 1100篇 |
1975年 | 1164篇 |
1974年 | 1357篇 |
1973年 | 1448篇 |
1972年 | 1378篇 |
1971年 | 1195篇 |
1970年 | 1247篇 |
1969年 | 1146篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Cephalosporins form a large group of β-lactam antibiotics which are used extensively in human medicine and to a lesser extent in domestic animals. In veterinary dermatology, the principle use for the cephalosporins is the clinical management of canine pyoderma associated with Staphylococcus intermedius . In practice, the use of orally administered first generation cephalosporin drugs to affected dogs is well tolerated and highly efficacious. Bacterial drug resistance appears to occur rarely. 相似文献
952.
To assess the oral activity of KP102 (also known GHRP-2) on growth hormone (GH) release in ruminant animals, 5 or 10 mg/kg body weight (BW) of KP102 dissolved in saline was orally administered twice at 2 hr-intervals to either 1- or 3-mo-old goats (n = 5-6). Plasma GH concentrations in the 1-mo-old goats were elevated at 15 min after the first administration of both 5 and 10 mg/kg BW of KP102. Significant elevation of GH concentrations continued until 180 min after 10 mg/kg BW of KP102, whereas the elevated GH levels after the administrations of 5 mg/kg BW of KP102 subsided to basal concentrations within 90 min. The second administration of 10 mg/kg BW of KP102 failed to elevate the GH concentration, but 5 mg/kg BW of KP102 abruptly stimulated GH release. Plasma GH concentrations in the 3-mo-old goats were also significantly elevated after the administration of both 5 and 10 mg/kg BW of KP102. The plasma GH responses to 5 and 10 mg/kg BW of KP102 were almost identical. The elevated GH levels after the first administration of KP102 tended to be maintained throughout the experiment, and a transient increase in plasma GH levels was observed after the second administration. However, the stimulatory effect of KP102 on GH release in the 3-mo-old goats was small and less abrupt than that in the 1-mo-old goats. The concentrations of insulin-like growth factor-I were not increased by KP102 during the brief sampling periods used in this experiment. These results show that the oral administration of the peptidergic GH secretogogue KP102 stimulates GH release in a ruminant species, and that the oral activity of KP102 on GH release is modified by the age. 相似文献
953.
Harrus S Klement E Aroch I Stein T Bark H Lavy E Mazaki-Tovi M Baneth G 《The Veterinary record》2002,151(3):82-85
Forty-six cats with clinical haemobartonellosis were studied; 75 per cent of the cats of known age were two-and-a-half years old or younger, 50 per cent were intact males and 19.5 per cent were castrated males. The predominant signs of the disease were tachypnoea, lethargy, depression, anorexia, infestation with fleas, pale mucous membranes, icterus, emaciation, dehydration, splenomegaly, anaemia, leucocytosis, increased activities of alanine aminotransferase and aspartate aminotransferase, and azotaemia. Thirty-eight per cent of the cats that were tested for feline leukaemia virus (FeLV) antigen were positive, and 22 per cent of those tested for feline immunodeficiency virus (FIV) antibodies were positive. The prevalence of both FeLV and FIV was much higher than in the general Israeli cat population. The cats infected with both Haemobartonella felis and FeLV had a significantly lower body temperature, were more anaemic and the mean cell volume of their erythrocytes was greater than in the cats with haemobartonellosis alone. 相似文献
954.
Shade effects on performance,carcass traits,physiology, and behavior of heat-stressed feedlot heifers 总被引:1,自引:0,他引:1
To determine whether shade influences performance, carcass traits, immunology, respiration rate, and behavior of cattle under conditions similar to those in commercial feedlots, we used 168 heifers in 12 soil-surfaced pens. Six pens were shaded with a galvanized steel-roofed shade (approximately 4 m high), allowing for 2.12 m2 of shade/heifer, and six pens served as the unshaded control. Heifers were fed a 90% concentrate diet during the 121-d trial that began in mid-June, performance variables (DMI, BW, ADG, gain:feed) were measured, and dietary concentrations of NEm and NEg calculated from performance data. A blood sample was collected to assess immune measures. Respiration rates and behaviors (feeding, drinking, walking, standing, lying, agonistic, and bulling) also were measured during the study. Carcass data (yield grade, kidney, pelvic, and heart fat, longissimus muscle area, hot carcass weight, quality grade, liver abscess rate, and incidence of dark-cutting beef) were collected at slaughter. Shaded heifers had higher (P < 0.05) DMI, ADG, and final BW than unshaded heifers. The gain:feed ratio and calculated dietary NEm and NEg concentrations did not differ (P > 0.26) between treatments. Most carcass traits did not differ between treatments, but more (P < 0.02) carcasses ofheifers in shaded pens graded USDA Choice than those in unshaded pens, which resulted primarily from the incidence of dark cutters being decreased (P < 0.04) by approximately half in carcasses from shaded compared with unshaded heifers. Respiration rate and percentage of circulating neutrophils were decreased (P < 0.01) for shaded compared with unshaded heifers. The treatment x time of day effect was significant (P < 0.05) for all behavioral measurements. Shaded heifers spent more time laying down (0800, 1200, and 1500, P < 0.05) and less time standing (1200 and 1500, P < 0.05) than unshaded heifers. Agonistic behavior was less (P < 0.05) for shaded than for unshaded heifers at 1900 and 2000, and bulling was less (P < 0.05) for-shaded than unshaded heifers at 2100. Results suggest that shade improved performance and altered behavior by feedlot heifers during the summertime in West Texas. 相似文献
955.
Pericardial tissue was obtained from 14 dogs with idiopathic pericarditis, and from three dogs with pericardial effusion associated with neoplastic disease, for histopathological assessment and characterisation of infiltrating leucocytes by immunohistochemistry. The major pathological change was extensive pericardial fibrosis which was generally accompanied by a mixed inflammatory response that was of greatest intensity at the cardiac surface of the tissue. Perivascular lymphoplasmacytic aggregates were present at the pleural surface and within the fibrosed pericardium. There were no features that clearly distinguished the samples from dogs with neoplastic disease from dogs with idiopathic pericarditis. The pericardial infiltrates were dominated by MAC 387+ monocyte-macrophages and plasma cells expressing immunoglobulin (Ig)A or IgG. CD3+ T lymphocytes and major histocompatibility complex (MHC) class II+ macrophages were less common, although the perivascular aggregates were mixtures of T and B lymphocytes and a proportion of fibroblasts expressed MHC class II. There was no vascular pathology or deposition of immunoglobulin or complement within vessel walls. These findings are consistent with an immune response dominated by humoral effector mechanisms (Th2 immunity) but do not clearly support a primary immune-mediated pathogenesis for idiopathic pericarditis. 相似文献
956.
In a case-control study in colic horses the ability of spectrophotometric measurement of the haemoglobin concentration in the peritoneal fluid supernatant and visual assessment of the colour of peritoneal fluid supernatant to differentiate between surgical and medical treatment of colic was assessed. Based on previous studies, which have found anda association between peritoneal fluid colour and the kind of treatment required, our hypothesis was that the peritoneal fluid haemoglobin concentration would be higher in horses requiring surgical intervention than in horses amenable to medical treatment. Seventy-four horses admitted to a teaching hospital were included. Thirty-five horses were classified as requiring surgery and 39 medical treatment. Logistic regression revealed a significant (P < 0.0001) association between the haemoglobin concentration measured with the spectrophotometer and the need for surgical treatment. Odds ratio for an increase in haemoglobin concentration of 0.01 mmol/l was 6.4, which means that the odds for 'need for surgical treatment' increased when peritoneal fluid haemoglobin concentration increased. When used as a diagnostic test with a threshold of 0.01 mmol/l haemoglobin for selecting surgical vs. medical treatment, sensitivity was 80% and specificity 82%, whereas simple visual assessment had a sensitivity of only 51% and a specificity of 95%. 相似文献
957.
Sandelin BA Brown AH Brown MA Johnson ZB Kellogg DW Stelzleni AM 《Journal of animal science》2002,80(12):3073-3076
Mature weight and rate of maturing were estimated in 177 Angus, Brahman, and reciprocal-cross cows grazing bermudagrass or endophyte-infected tall fescue over a 4-yr period to evaluate genotype x environment interactions. Data were collected every 28 d until cows were approximately 18 mo of age and then at prebreeding, postcalving, and weaning of calf. All cows with weight data to at least 42 mo of age were included in the analysis. Mature weight and rate of maturing were estimated using the three-parameter growth curve model described by Brody (1945). Data were pooled over year and analyzed by the general linear model procedure of SAS. Included in the models for mature weight and rate of maturing were the independent variables of genotype, environment, and genotype x environment interaction. There was a genotype x environment interaction (P < 0.01) for mature body weight (BW) but not for rate of maturing. Angus cows grazing fescue pastures had greater (P < 0.01) mean mature BW than Angus x Brahman cows grazing bermudagrass (611 +/- 17 vs 546 +/- 16 kg). Angus x Brahman cows grazing bermudagrass had lower (P < 0.05) mean mature BW than Brahman x Angus cows grazing bermudagrass or endophyte-infected fescue and Brahman cows grazing bermudagrass (546 +/- 16 vs 624 +/- 19, 614 +/- 22 and 598 +/- 20 kg, respectively). Brahman cows grazing endophyte-infected fescue had smaller (P < 0.05) mean mature BW than all genotype x forage combinations except for Angus x Brahman cows grazing bermudagrass. Angus cows had a smaller (P < 0.05) mean rate of maturing than Angus x Brahman and Brahman x Angus cows (0.039 +/- 0.002 vs 0.054 +/- 0.002 and 0.049 +/- 0.002%/mo, respectively), respectively, and Angus x Brahman cows had a larger (P < 0.05) mean rate of maturing than Brahman x Angus and Brahman cows (0.054 +/- 0.002 vs 0.049 +/- 0.002 and 0.041 +/- 0.002 %/mo, respectively). There was a direct breed x forage interaction (P < 0.05) for mature BW. These data suggest that the choice of breed type is important in maintaining a crossbreeding program, in that mature BW and rate of maturing are critical to the matching of animal requirements to available production resources. 相似文献
958.
A health problem of an animal or a group of animals represents a potential stress situation for the animal keeper. In this article, the transactional stress model, which was developed in social psychology was applied on the animal keeper and shows, how he perceives the influence of animal care. If veterinary help is considered relevant, it may lead to an improved coping, which affects the health of the animal keeper and the animal as well. This viewpoint leads to a cycle, in which cause, success, coping and utility are closely linked together. 相似文献
959.
1. In two separate experiments, the possibility of detecting embryonic development in chicken eggs was assessed using the same spectrophotometric method used to detect blood in Table eggs, using a combination of two wavelengths (577 and 610 nm) of the transmission spectrum. 2. In the first experiment, during the first 10 d of incubation, transmission spectra of 30 Hisex White eggs and 30 Hybro eggs were measured daily. 3. In the second experiment, 292 Hisex White eggs were incubated. Seven groups were randomly assigned. Six received an injection of sodium azide (NaN3) at different times during incubation in order to stop embryonic development, and during the first 12 d of incubation the transmission spectrum was measured daily. The acoustic resonance analysis method was also used on a group of uninjected eggs. 4. In the first experiment, it was possible to detect embryonic development from 120 h of incubation onwards in fertile eggs. In the second experiment changes in light transmission due to embryonic development were detected from 108 h of incubation. Detection of embryonic development using the acoustic resonance analysis method in the second experiment was possible only from 120 h of incubation. 5. It was concluded that the detection of embryonic development using visible light transmission is not directly linked with the formation of blood, but with the formation of sub-embryonic fluid, which takes place from 72 h of incubation onwards. This fluid makes the yolk sac translucent so that absorption of light at 577 nm can be detected. 相似文献
960.
Elsinghorst TA 《The Veterinary quarterly》2002,27(4):183-189
Summary The study concerned 123 Journals of the category "Veterinary Sciences" as defined in the Journal Citation Reports (?, Institute for Scientific Information (ISI), Philadelphia, USA). Using Web of Knowledge (?, ISI, USA), update December 3, 2005, articles published in 2002 and 2003 and cited 20 times or more were selected. The total number of selected articles was 96. They were published in 34 out of the 123 journals. Based on the country of the first author, the articles originated form 24 countries. Forty-nine of the 96 articles (51%) were written in only two countries being England (15) and the USA (34). The articles could be classified in six categories being immunology (21), microbiology and directly related subjects (48), prions and prion-induced diseases (5), reproduction (23), toxicology (3), and miscellanea (11). The category "microbiology" (48) was divided into six subcategories: general (1), bacteriology (17), mycology (3), parasitology (5), protozoology (6), and virology (5). Some articles were classified in more than one (sub)category. 相似文献