全文获取类型
收费全文 | 197419篇 |
免费 | 11274篇 |
国内免费 | 780篇 |
专业分类
林业 | 7762篇 |
农学 | 6067篇 |
基础科学 | 1569篇 |
23549篇 | |
综合类 | 36809篇 |
农作物 | 7457篇 |
水产渔业 | 9612篇 |
畜牧兽医 | 100475篇 |
园艺 | 2640篇 |
植物保护 | 13533篇 |
出版年
2019年 | 1836篇 |
2018年 | 2658篇 |
2017年 | 2990篇 |
2016年 | 2752篇 |
2015年 | 2539篇 |
2014年 | 2950篇 |
2013年 | 7336篇 |
2012年 | 5660篇 |
2011年 | 7011篇 |
2010年 | 4541篇 |
2009年 | 4435篇 |
2008年 | 6618篇 |
2007年 | 6341篇 |
2006年 | 5982篇 |
2005年 | 5617篇 |
2004年 | 5375篇 |
2003年 | 5345篇 |
2002年 | 5182篇 |
2001年 | 5972篇 |
2000年 | 5873篇 |
1999年 | 4736篇 |
1998年 | 1945篇 |
1997年 | 1911篇 |
1995年 | 2192篇 |
1994年 | 1976篇 |
1993年 | 1900篇 |
1992年 | 3936篇 |
1991年 | 4230篇 |
1990年 | 4263篇 |
1989年 | 4196篇 |
1988年 | 3845篇 |
1987年 | 3992篇 |
1986年 | 4114篇 |
1985年 | 3862篇 |
1984年 | 3303篇 |
1983年 | 2918篇 |
1982年 | 1991篇 |
1981年 | 1874篇 |
1979年 | 2944篇 |
1978年 | 2419篇 |
1977年 | 2045篇 |
1976年 | 1913篇 |
1975年 | 2020篇 |
1974年 | 2683篇 |
1973年 | 2695篇 |
1972年 | 2632篇 |
1971年 | 2411篇 |
1970年 | 2254篇 |
1969年 | 2101篇 |
1967年 | 1798篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Kummer M Geyer H Imboden I Auer J Lischer C 《Veterinary journal (London, England : 1997)》2006,172(1):58-66
The understanding of the normal position of the third phalanx (P3) and the distal sesamoid bone in relation to the size and shape of the hoof capsule in sound horses is helpful in the diagnosis of equine foot lameness. Some measurements on radiographs used to define the position of the pedal bone within the hoof capsule are significantly influenced by hoof trimming and the height of the withers. In this study, the front hooves of 40 Warmblood horses were radiographed twice, eight weeks apart, both before and after their hooves were trimmed by an experienced farrier. Using the software programme Metron PX, 22 parameters on the lateromedial view and 16 parameters on the dorsopalmar view were measured and the effect of hoof trimming and height of the withers were calculated, respectively. Some of the hoof parameters showed mild positive correlation with the height of the withers. In 70% of the horses the left hoof capsule and P3 were significantly larger than the right. Hoof trimming had a remarkable influence on hoof conformation, especially for parameters in the toe region. Of all the measurements that describe the position of the third phalanx (P3) in relation to the hoof capsule, the distances between the distal tip of P3 to the solar surface of the foot, P3 to the tip of the toe and P3 to the point of break-over showed the greatest differences before and after trimming. The database of the present study can be used by farriers and veterinarians as a guideline for routine and corrective shoeing of Warmblood horses. 相似文献
992.
Weese JS Kenney DG O'Connor A 《Journal of the American Veterinary Medical Association》2000,217(3):372-5, 340
A 2-week-old Toggenburg kid was evaluated for persistent diarrhea and poor body condition. The herd had high morbidity and mortality associated with diarrhea in neonatal kids. Lactose intolerance was diagnosed on the basis of results of a lactose tolerance test and glucose absorption test. Clinically normal herdmates were used as control animals. The kid responded to lactase supplementation. Cryptosporidium organisms were detected in feces of several affected kids during episodes of acute diarrhea. Lactose intolerance was presumed to have developed secondary to intestinal cryptosporidiosis. 相似文献
993.
Rivera VM Wang X Wardwell S Courage NL Volchuk A Keenan T Holt DA Gilman M Orci L Cerasoli F Rothman JE Clackson T 《Science (New York, N.Y.)》2000,287(5454):826-830
A system for direct pharmacologic control of protein secretion was developed to allow rapid and pulsatile delivery of therapeutic proteins. A protein was engineered so that it accumulated as aggregates in the endoplasmic reticulum. Secretion was then stimulated by a synthetic small-molecule drug that induces protein disaggregation. Rapid and transient secretion of growth hormone and insulin was achieved in vitro and in vivo. A regulated pulse of insulin secretion resulted in a transient correction of serum glucose concentrations in a mouse model of hyperglycemia. This approach may make gene therapy a viable method for delivery of polypeptides that require rapid and regulated delivery. 相似文献
994.
Due to the several advantages expected from growing self-compatible almond cultivars, breeding programmes have recently introduced self-compatibility as an important trait. However, doubts have arisen regarding the capability of the newly obtained self-compatible almonds to produce good yields in monovarietal plantations, and the commercial quality of the fruits from self-pollination. For this reason, in the last years several studies have been conducted to evaluate fruit set and fruit traits following self- and cross-pollination of self-compatible almonds. Their results showed inconsistencies for fruit set and for some of the fruit traits studied. Thus, while some studies showed no differences between both pollination types for any of the fruit traits, others clearly showed important differences with the detriment of self-pollination for commercially important fruit traits. The fact that some of these studies evaluated a low number of individuals and/or fruit traits, implies the need of a more complete study. In this work, 10 fruit traits were studied in 26 self-compatible almonds following self-pollination by bagging and open pollination treatments. In general, and despite a few individuals showed differences between both pollination types for two of the traits, the results showed no influence of self-pollination in fruit quality. 相似文献
995.
The objective of this study was to determine the effect of a subtherapeutic level of chlortetracycline (CTC) fed to growing beef steers under conditions of limited and adequate dietary protein on plasma concentrations of GH, thyroid-stimulating hormone (TSH), and thyroid hormones before and after an injection of thyrotropin-releasing hormone (TRH) + GHRH. Young beef steers (n = 32; average BW = 285 kg) were assigned to a 2x2 factorial arrangement of treatments of either a 10 or 13% crude protein diet (70% concentrate, 15% wheat straw, and 15% cottonseed hulls) and either a corn meal carrier or carrier + 350 mg of CTC daily top dressed on the diet. Steers were fed ad libitum amounts of diet for 56 d, and a jugular catheter was then placed in each steer in four groups (two steers from each treatment combination per group) during four consecutive days (one group per day). Each steer was injected via the jugular catheter with 1.0 microg/kg BW TRH + .1 microg/kg BW GHRH in 10 mL of saline at 0800. Blood samples were collected at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 120, 240, and 360 min after releasing hormone injection. Plasma samples were analyzed for GH, TSH, thyroxine (T4), and triiodothyronine (T3). After 84 d on trial, the steers were slaughtered and the pituitary and samples of liver were collected and analyzed for 5'-deiodinase activity. Feeding CTC attenuated the GH response to releasing hormone challenge by 26% for both area under the response curve (P<.03) and peak response (P<.10). Likewise, CTC attenuated the TSH response to releasing hormone challenge for area under the response curve by 16% (P<.10) and peak response by 33% (P<.02), and attenuated the T4 response for area under the curve by 12% (P<.08) and peak response by 14% (P<.04). Type II deiodinase activity in the pituitary was 36% less (P<.02) in CTC-fed steers than in steers not fed CTC. The results of this study are interpreted to suggest that feeding subtherapeutic levels of CTC to young growing beef cattle attenuates the release of GH and TSH in response to pituitary releasing hormones, suggesting a mechanism by which CTC may influence tissue deposition in cattle. 相似文献
996.
997.
A. O. Oso A. O. Fafiolu M. A. Adeleke O. A. Ladokun R. A. Sobayo A. V. Jegede S. O. Peters O. A. Oyebamiji J. Akinsola 《Journal of animal physiology and animal nutrition》2014,98(4):766-774
The effect of dosage and application mode of l ‐carnitine on plasma lipid and egg‐yolk cholesterol of breeder turkeys, hatchability of eggs and post‐hatch growth response was investigated using 180 breeder hens. The hens were assigned to six dietary treatments in a 2 × 3 factorial arrangements of two application modes of l ‐carnitine (diet and drinking water) supplemented at 0, 50 and 100 ppm (mg/kg or mg/l) levels, respectively. Each treatment was replicated five times with six hens per replicate. Dietary inclusion of 50 ppm l ‐carnitine showed the lowest (p < 0.01) plasma total cholesterol (TC) and low‐density lipoprotein concentration (LDL). Breeder hens offered 50 ppm l ‐carnitine with no regard to application mode recorded the highest (p < 0.01) plasma high‐density lipoprotein (HDL). Hens offered 50 and 100 ppm l ‐carnitine irrespective of application mode also showed reduced (p < 0.01) egg‐yolk TC concentration at 32 weeks of age. Dietary supplementation of 50 ppm l ‐carnitine for breeder turkeys recorded the lowest (p < 0.01) egg‐yolk triglyceride (TG) at 40 weeks of age. Hens offered 50 ppm l ‐carnitine irrespective of application mode recorded the highest (p < 0.05) hen‐day egg production. Incidence of dead‐in‐shell also reduced (p < 0.05) with increasing dosage of l ‐carnitine. Dietary supplementation of 50 ppm and oral application in drinking water of 100 ppm l ‐carnitine for breeder turkeys resulted in highest (p < 0.05) egg fertility. Offsprings from breeder hens fed diets supplemented with l ‐carnitine recorded no post‐hatch mortality. Highest (p < 0.05) post‐hatch final live weight and weight gain was obtained with poults obtained from hens fed diet supplemented with 50 ppm l ‐carnitine. In conclusion, dietary supplementation of 50 ppm l ‐carnitine for turkey hens showed improved serum lipid profile, egg fertility, reduced dead‐in‐shell, egg‐yolk cholesterol and resulted in improved post‐hatch growth performance. 相似文献
998.
Østerberg J Ekwall SJ Nilsson I Stampe M Engvall A Wallgren P 《Berliner und Münchener tier?rztliche Wochenschrift》2001,114(9-10):331-334
An integrated SPF herd with 320 sows was found infected with Salmonella Yoruba during an annual control among sows, aiming to verify freedom from Salmonella infections. It is believed that the infection was introduced to the herd by purchase of feed. The herd performed an age segregated rearing system. Sows and piglets were reared at a central farm, while growers (25-100 kg body weight) were reared at sub-estates. The growers were free from the infection, and as a consequence a specially designed eradication program was designed. Farrowing and weaning were defined as periods of risk for sows and piglets, respectively. Consequently sows were isolated and individually tested for presence of Salmonella one week before and one week after farrowing. The offspring were tested one week post weaning. To verify freedom from disease among piglets they were also tested another time before transfer to the uninfected sub-estates. Piglets with undefined status regarding Salmonella were denoted animals at risk and not transferred to the sub-estates. Instead they were transferred to a third estate, rented to house pigs at risk. The program was successful. It allowed full production during performance, and the herd was declared free from S. Yoruba seven and a half months after the initial diagnosis. 相似文献
999.
1000.
J. Schumacher DVM MS H. D. Moll DVM MS J. S. Spano DVM PhD L. M. Barone DVM R. D. Powers DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1990,4(3):153-156
Two horses were presented with lethargy, weight loss, anorexia, and swelling of the limbs and ventral body wall. One horse, a 12-month-old American Paso Fino colt, also had acute abdominal pain. The other horse, a seven-month-old Tennessee Walking Horse (TWH) filly passed diarrheic stools during the initial examination. Each horse had low serum protein, neutropenia, and a normal packed cell volume (3.2 g/dl, 1300 cells/ul, and 38%, respectively, for the colt, and 2.4 g/dl, 696 cells/ul, and 44%, respectively for the filly). After intravenously administering plasma, the colt's PCV dropped to 23%, and the filly's dropped to 30%. During exploratory surgery, 3.5 and 2.0 meters of thickened terminal small intestine were removed from the colt and filly respectively, and a jejunocecostomy performed. The results of histologic examination of resected intestine were consistent with a diagnosis of equine granulomatous enteritis (EGE). Both horses showed clinical improvement within two days after surgery. The colt developed a neutrophilia (20,500 cells/ul) within 24 hours of surgery. Serum protein concentrations remained stable and gradually elevated to normal or near normal values of 7.0 g/dl (colt) and 5.8 g/dl (filly) by two weeks. The colt was killed four months after surgery because of signs of abdominal pain. Postmortem examination revealed a small intestinal volvulus associated with an adhesion. The TWH filly remains clinically normal 13 months after surgery. 相似文献