全文获取类型
收费全文 | 150726篇 |
免费 | 8565篇 |
国内免费 | 94篇 |
专业分类
林业 | 5412篇 |
农学 | 4480篇 |
基础科学 | 976篇 |
17115篇 | |
综合类 | 28177篇 |
农作物 | 5952篇 |
水产渔业 | 7251篇 |
畜牧兽医 | 78670篇 |
园艺 | 1792篇 |
植物保护 | 9560篇 |
出版年
2018年 | 1931篇 |
2017年 | 2254篇 |
2016年 | 2055篇 |
2015年 | 1810篇 |
2014年 | 2209篇 |
2013年 | 5644篇 |
2012年 | 4070篇 |
2011年 | 4982篇 |
2010年 | 3174篇 |
2009年 | 3262篇 |
2008年 | 4784篇 |
2007年 | 4562篇 |
2006年 | 4398篇 |
2005年 | 4052篇 |
2004年 | 3900篇 |
2003年 | 3953篇 |
2002年 | 3728篇 |
2001年 | 4830篇 |
2000年 | 4788篇 |
1999年 | 3786篇 |
1998年 | 1560篇 |
1997年 | 1515篇 |
1996年 | 1408篇 |
1995年 | 1724篇 |
1994年 | 1550篇 |
1993年 | 1504篇 |
1992年 | 3229篇 |
1991年 | 3371篇 |
1990年 | 3182篇 |
1989年 | 3279篇 |
1988年 | 2982篇 |
1987年 | 3179篇 |
1986年 | 3244篇 |
1985年 | 3097篇 |
1984年 | 2483篇 |
1983年 | 2187篇 |
1982年 | 1537篇 |
1981年 | 1346篇 |
1979年 | 2197篇 |
1978年 | 1817篇 |
1977年 | 1573篇 |
1976年 | 1491篇 |
1975年 | 1601篇 |
1974年 | 2014篇 |
1973年 | 2073篇 |
1972年 | 1989篇 |
1971年 | 1857篇 |
1970年 | 1779篇 |
1969年 | 1607篇 |
1967年 | 1402篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
D G Bristol 《Journal of the American Veterinary Medical Association》1989,195(4):492-494
A dairy cow was examined because of extensive obstruction of a teat cistern. The teat was treated by surgical resection of scar tissue, transplantation of an oral-mucosal autograft, and temporary implantation of a silastic tube. The silastic tube became dislodged from the teat, and was surgically removed 30 days after the initial surgery. The cow subsequently had 2 normal lactations. Prior to the third postoperative lactation, the cow developed severe udder edema. During lactation, the surgically treated teat became hard and was difficult to milk. The cow was then culled. 相似文献
992.
H Fuhrmann C Eulitz-Meder H Geldermann H P Sallmann 《Berliner und Münchener tier?rztliche Wochenschrift》1989,102(6):188-193
Lactational performance in high-yielding dairy cows has its limits in metabolic processes. Energy metabolism is maintained by mobilization of body reserves via hormonal regulation, resulting in lipolysis and sometimes ketoacidosis. For characterization of such conditions the intraruminal and intravascular application of glucose and volatile fatty acids was used in ruminant physiology. On the other hand the results of such experiments were correlated to actual and potential milk yield. For this investigation pairs of monozygous Holstein Friesian twins were tested as heifers and as cows by intravenous infusion of glucose, propionate and butyrate after 18 hours of feed withdrawal. Insulin, growth hormone, glucose, free fatty acids and beta-hydroxybutyrate were measured before, during and up to 4 hours after infusion of substrates. Each substrate caused a transient change in plasma concentrations of metabolites and hormones. Differences between heifers and cows are discussed with the time series of the mean concentrations. The reaction profile of each animal was characterized by different parameters. Analysis of these parameters revealed a close relation between hormones and metabolites even under the conditions of the load-test. 相似文献
993.
L. W. FIKES DVM H. C. LIN DVM J. C. THURMON DVM MS DiplomateACVA 《Veterinary surgery : VS》1989,18(1):85-86
Xylazine (0.35 mg/kg) or lidocaine (0.35 mg/kg) was injected into the epidural space of six ponies to compare their effectiveness as epidural analgesics. Each pony received both treatments at 1 week intervals with the order of treatments randomized. Xylazine produced analgesia of significantly longer duration (247 +/- 58 minutes) than that produced by an equal dose of lidocaine (135 +/- 22 minutes). Mild transient ataxia of no clinical significance developed in all ponies with both treatments. Spinal cords were removed from two ponies and examined histologically. No discernible pathologic changes were noted. 相似文献
994.
995.
Evaluation of the Staph-Zym-system for identification of Staphylococcus hyicus and Staphylococcus intermedius 总被引:2,自引:0,他引:2
C L?mmler 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(3):180-184
The Staph-Zym system was evaluated as a means for identifying cultures of Staphylococcus hyicus isolated from pigs and bovines and cultures of Staphylococcus intermedius isolated from canines. The selected cultures had been identified by conventional methods. The Staph-Zym system correctly identified all 52 S. hyicus and all 33 S. intermedius. It is concluded that the Staph-Zym system is a practical and reliable test for identifying mostly animal pathogenic S. hyicus and S. intermedius, and might possibly be useful for veterinary microbiologists. 相似文献
996.
H Adam G von Lengerken D Olthoff M Schwalbe M Wicke 《Archiv fuer experimentelle veterinaermedizin》1989,43(2):293-299
Membraneous phospholipids of subcellular structures were determined from the musculature of German Landrace pigs of the GDR, following exposure to halothane. Mating variants A (H+ male X H+ female), B (H+ male X H- female), and C (H- male X H+ female) were used for positive responders (MHS), while variants B, C, and D (H- male X H- female) were used for negative responders (MHN). Four phospholipid fractions were recorded from the muscle samples for mitochondria and microsomes (according to SR section). Differences between the MHS and MHN groups for the above fractions and without consideration of mating variants and genotype were not observed, although unambiguous responses were exhibited by all animals, either positive or negative to halothan. Significant differences with regard to the above phospholipid fractions were recordable only for variant A (MHS group) as compared to D (MHN), in other words, for the homozygous genotypes, once the above results had been rearranged within MHS and MHN along with different mating variants and genotypes. However, no unambiguous results were obtainable for the heterozygous genotypes of mating variants B and C. Possible underlying reasons are discussed in some detail. The results obtained from mating variants A and D are likely to confirm earlier findings and seem to suggest that the sarcoplasmic reticulum is the primary site of origin of susceptibility to halothane or malignant hyperthermia. 相似文献
997.
B.D. Scott BS MS G.D. Potter PhD J.W. Evans PhD J.C. Reagor PhD G.W. Webb PhD S.P. Webb MS 《Journal of Equine Veterinary Science》1989,9(4)
Twenty-four yearlings were used to evaluate the efficacy of feeding feed-grade fat to growing horses. All horses were started on trial at 13-months-of-age and were fed for 112 days. The experimental diets, containing similar nutrient-to-calorie ratios, were: 1) control (no added fat; 2) 5% added fat and; 3) 10% added fat. There was a trend for yearlings fed the 10% added fat diet to grow faster and eat less feed than those on the control diet. Data from this study indicate that feed-grade fat can be safely fed to growing horses. Feeding fat to yearlings stimulated growth and efficiency of feed utilization initially, but these effects were not maintained as the yearlings grew toward maturity. 相似文献
998.
999.
1000.
R L Hamlin C A Buffington 《Veterinary Clinics of North America: Small Animal Practice》1989,19(3):527-538
Nutritional deficiencies (e.g., carnitine in dogs, taurine in cats) resulting in cardiomyopathy, and nutritional excesses (e.g., calories leading to obesity, sodium leading to hypertension) have emerged as important considerations in cardiology. These dietary factors may become particularly exaggerated in altered physiological and/or pathological states (e.g., pregnancy, old age, primary cardiovascular disease). Unfortunately, we do not have complete information on requirements for essential nutrients, nor do we know the precise role nutrition may play in the production of so-called old-age diseases or on the interactions among other organ systems (e.g., kidney, liver) and the heart. 相似文献