全文获取类型
收费全文 | 9635篇 |
免费 | 485篇 |
国内免费 | 14篇 |
专业分类
林业 | 594篇 |
农学 | 236篇 |
基础科学 | 86篇 |
1674篇 | |
综合类 | 1674篇 |
农作物 | 383篇 |
水产渔业 | 825篇 |
畜牧兽医 | 3616篇 |
园艺 | 282篇 |
植物保护 | 764篇 |
出版年
2023年 | 62篇 |
2022年 | 62篇 |
2021年 | 153篇 |
2020年 | 218篇 |
2019年 | 212篇 |
2018年 | 207篇 |
2017年 | 224篇 |
2016年 | 214篇 |
2015年 | 192篇 |
2014年 | 261篇 |
2013年 | 496篇 |
2012年 | 559篇 |
2011年 | 726篇 |
2010年 | 380篇 |
2009年 | 362篇 |
2008年 | 648篇 |
2007年 | 637篇 |
2006年 | 615篇 |
2005年 | 598篇 |
2004年 | 619篇 |
2003年 | 592篇 |
2002年 | 513篇 |
2001年 | 116篇 |
2000年 | 101篇 |
1999年 | 102篇 |
1998年 | 82篇 |
1997年 | 75篇 |
1996年 | 57篇 |
1995年 | 65篇 |
1994年 | 66篇 |
1993年 | 51篇 |
1992年 | 62篇 |
1991年 | 55篇 |
1990年 | 71篇 |
1989年 | 60篇 |
1988年 | 46篇 |
1987年 | 48篇 |
1986年 | 39篇 |
1985年 | 42篇 |
1984年 | 38篇 |
1983年 | 48篇 |
1982年 | 28篇 |
1981年 | 32篇 |
1980年 | 32篇 |
1979年 | 27篇 |
1978年 | 20篇 |
1977年 | 20篇 |
1976年 | 22篇 |
1975年 | 27篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Systemic candidiasis in calves on prolonged antibiotic therapy 总被引:1,自引:0,他引:1
993.
R Jensen A C Pier C C Kaltenbach W J Murdoch V M Becerra K W Mills J L Robinson 《American journal of veterinary research》1989,50(2):285-289
Premature calving, typified by early expulsion (17 to 43 days) of weak or dead calves and accompanied by retained placentas, was induced in 8 of 9 pregnant cows fed a mixture of Ponderosa pine needles and alfalfa hay. Five control cows of comparable gestation age fed only alfalfa hay maintained normal pregnancies until they were euthanatized at the time the pine needle-treated cows were producing premature calves. Serum specimens from all cows were assayed for progesterone concentration and ovaries and placentomes were examined for histopathologic changes. There were no bacterial, fungal, chlamydial, or viral agents determined to be associated with the premature births. Serum progesterone concentration in the treated cows decreased progressively and were 0.4 to 1.5 ng/ml at the time of premature calving. Histopathologic changes were evident in the placenta and corpora lutea of treated cows only. The number of binucleate trophoblastic giant cells in placentomes was less than normal and the number of necrotic luteal cells in corpora lutea was greater than normal. 相似文献
994.
Deborah A. O''Keefe DVM MS David J. Schaeffer PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(5):276-282
The hematologic toxicity of doxorubicin, 30 mg/m2 body surface area (BSA) every 21 days to a cumulative dose of 300 mg/m2, was evaluated in six cats. Complete blood and platelet counts were performed daily during the first treatment cycle. They were monitored before treatment for all remaining cycles, and at the average neutrophil nadir (day 8) starting with cycle 4. Significant poikilocytosis developed after the first treatment and remained throughout the study, although anemia did not occur. No other red blood cell abnormalities were seen. Platelet counts remained within the reference range throughout the first treatment cycle, but mild thrombocytopenia (88,000-288,000/uL) was found in 11.3% of subsequent complete blood counts (CBCs). Thrombocytosis was seen in 30.9% of CBCs. Neutropenia did not occur during the first treatment cycle although neutrophil counts did decrease, with the nadir occurring between days 8 and 11. All neutrophil counts returned to pretreatment values by day 14. Neutropenia was documented after 14 of 46 (30.4%) doxorubicin treatments, and was associated with fever in 5 cats (10.9%). All fevers responded to oral antibiotic therapy. Neutropenia that lasted more than 14 days developed in two cats, necessitating dosage reduction to 25 mg/m2 BSA. At the dose used in this study, doxorubicin administration was associated with acceptable hematologic toxicosis in most cats. 相似文献
995.
Meat composition and palatability of Holstein and beef steers as influenced by forage type and protein source. 总被引:1,自引:0,他引:1
E W Mills J W Comerford R Hollender H W Harpster B House W R Henning 《Journal of animal science》1992,70(8):2446-2451
This experiment determined meat composition and palatability changes resulting from feeding Holstein (HOL) and crossbred beef (XB) steers diets containing corn silage (CS) or alfalfa haylage (AH) (forage type) and soybean meal (SM) or fish meal (FM) (protein source). Fifty-nine steers (30 HOL and 29 XB) were randomly assigned to diet combinations for a 2 x 2 x 2 (breed x forage x protein) factorial arrangement. Steers were fed to a fat-constant end point (fat depth over the longissimus muscle measured by ultrasound: 1.0 cm XB, .6 cm HOL). Proximate and fatty acid analysis and sensory evaluation were conducted on a rib eye roast and steaks, respectively, removed from the left side of each carcass at ribs 9 to 12. Proximate analysis of the longissimus muscle showed no significant difference (P greater than .05) in moisture, protein, or fat content due to breed, forage, or protein treatment. Forage type had no significant effect (P greater than .05) on amount of individual fatty acids found in longissimus muscle. However, total polyunsaturated fatty acids were higher (P greater than .05) for AH than for CS-fed animals. Longissimus muscle from steers fed FM had higher palmitoleic and lower stearic acid contents (both P less than .05) than longissimus muscle from animals fed SM. Muscle from HOL had higher palmitoleic and lower stearic acid contents than that from XB steers (both P less than .05). There was no significant interaction (P greater than .05) of breed with either diet treatment for individual fatty acid contents.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
996.
Ralph C. Weichsei. Baum DVM Daniel A. Feeney DVM MS David W. Hayden DVM PhD 《Veterinary radiology & ultrasound》1994,35(6):418-426
It was the intent of this study to define which, if any, radiographic observations corresponded with specific causes of diffuse infiltrative small bowel disease and if radiographic findings could differentiate inflammatory disease from neoplastic disease and either of them from normal. Bowel spasticity, luminal narrowing, and thumbprinting tend to indicate the presence of tumor more often than inflammatory disease. Increased bowel gas in cats and barium adhesion in dogs and cats suggest that a component of enteritis is present. Decreased bowel gas in dogs is more often associated with obstructive disease, but is not helpful in differentiating diffuse inflammatory disease from diffuse neoplastic disease. While several observations that can foster differentiation of neoplastic from inflammatory disease were found, this study also indicated that the UGI lacks a high degree of predictive value other than to indicate the presence of infiltrative small bowel disease. 相似文献
997.
J C Williams J W Knox K S Marbury M D Kimball S W Scheide T G Snider M U David 《American journal of veterinary research》1984,45(10):1989-1993
Efficacy of fenbendazole, at doses of 7.5 and 10.0 mg/kg of body weight, against inhibited early 4th-stage larvae of Ostertagia ostertagi and other nematodes of the abomasum and intestinal tract, was investigated in naturally infected yearling heifers in late May 1982. In Louisiana, this is near the end of the period (March to May) in which maximal numbers of inhibition-prone larvae are acquired. The mean numbers of O ostertagi in 10 untreated control cattle were: adults, 4,880; developing 4th-stage larvae, 12,546; and inhibited early 4th-stage larvae, 167,931. At the 7.5 mg/kg dose level (10% liquid suspension) in 10 cattle, percentage reduction of O ostertagi in comparison with controls was: adults, 95.7%; developing 4th stages, 91.1%; and inhibited 4th stage, 55.0%. Percentage reductions of other genera were as follows: abomasum--Trichostrongylus axei, 99.6%; Haemonchus sp, 95.1%; intestinal tract--Cooperia spp, 97.8%; Trichostrongylus colubriformis, 100.0%; and Oesophagostomum radiatum 4th stage and adults, 100.0%. At the 10.0 mg/kg dose (10% liquid suspension) in 11 cattle, the percentage reduction of O ostertagi in comparison with controls was: adults, 98.6%; developing 4th stages, 92.9%; and inhibited 4th stage, 80.0%. Percentage reductions of other genera were: abomasum--T axei, 99.9%; Haemonchus sp, 98.8%; intestinal tract--Cooperia spp, 99.3%; T colubriformis, 100.0%; and Oes radiatum 4th stage and adults, 100.0%. Variability of efficacy against inhibited larvae was observed, particularly at the 7.5 mg/kg dose; at this dose, 7 of the 10 heifers in the group yielded in excess of 54,000 surviving larvae.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
998.
This case history describes a fatal complication of cardiac catheterization in a dog. A 2-year-old intact female miniature Schnauzer presented with a one month history of coughing, tachypnea, and dyspnea that was unresponsive to medical therapy. On clinical examination, a 4/6 systolic murmur was auscultated over the left and right fourth intercostal spaces. Lung sounds were diffusely increased. Survey radiographs revealed cardiomegaly and pulmonary edema. Cardiac catheterization was undertaken to clarify the cause of congestive cardiac failure but was abandoned when contrast medium was seen in the pericardial sac following an attempted injection of the contrast medium into the left ventricle. During recovery from anesthesia progressive pallor, hemothorax, and respiratory distress developed. The dog died 10 hours later despite aggressive support therapy. Gross necropsy revealed hemorrhage into the pericardial sac and pleural space, thrombus formation around and perforation of the right coronary artery. 相似文献
999.
The drivers which influence the types of crop protection most needed by agriculture are changing. A polarisation of approaches has resulted in the needs of organic agriculture and biotechnological agriculture, which can be identified as the current extremes of the spectrum, becoming very different. The main requirements of these two sectors are identified here and used as the basis for questioning future EU research requirements in crop protection. Factors affecting/influencing organic farming and the use of genetically modified crops are discussed in some detail. 相似文献
1000.
Detection and Quantification of Phytophthora ramorum from California Forests Using a Real-Time Polymerase Chain Reaction Assay 总被引:1,自引:0,他引:1
ABSTRACT The timely and accurate detection of pathogens is a critical aid in the study of the epidemiology and biology of plant diseases. In the case of regulated organisms, the availability of a sensitive and reliable assay is essential when trying to achieve early detection of the pathogen. We developed and tested a real-time, nested polymerase chain reaction (PCR) assay for the detection of Phytophthora ramorum, causal agent of sudden oak death. This technique then was implemented as part of a widespread environmental screen throughout California. The method here described is sensitive, detecting less than 12 fg of pathogen DNA, and is specific for P. ramorum when tested across 21 Phytophthora spp. Hundreds of symptomatic samples from 33 sites in 14 California counties were assayed, resulting in the discovery of 10 new host species and 23 infested areas, including 4 new counties. With the exception of a single host, PCR-based discovery of new hosts and infested areas always was confirmed by traditional pathogen isolations and inoculation studies. Nonetheless, molecular diagnostics were key in early pathogen detection, and steered the direction of further research on this newly discovered and generalist Phytophthora species. 相似文献