全文获取类型
收费全文 | 220475篇 |
免费 | 11841篇 |
国内免费 | 148篇 |
专业分类
林业 | 9270篇 |
农学 | 7287篇 |
基础科学 | 1387篇 |
28507篇 | |
综合类 | 34962篇 |
农作物 | 8639篇 |
水产渔业 | 11277篇 |
畜牧兽医 | 113410篇 |
园艺 | 3043篇 |
植物保护 | 14682篇 |
出版年
2020年 | 1871篇 |
2019年 | 2236篇 |
2018年 | 3259篇 |
2017年 | 3703篇 |
2016年 | 3399篇 |
2015年 | 2936篇 |
2014年 | 3683篇 |
2013年 | 8938篇 |
2012年 | 6611篇 |
2011年 | 8131篇 |
2010年 | 5399篇 |
2009年 | 5455篇 |
2008年 | 8000篇 |
2007年 | 7663篇 |
2006年 | 7171篇 |
2005年 | 6615篇 |
2004年 | 6340篇 |
2003年 | 6492篇 |
2002年 | 5957篇 |
2001年 | 7002篇 |
2000年 | 6973篇 |
1999年 | 5646篇 |
1998年 | 2388篇 |
1997年 | 2324篇 |
1996年 | 2163篇 |
1995年 | 2586篇 |
1994年 | 2242篇 |
1993年 | 2167篇 |
1992年 | 4362篇 |
1991年 | 4601篇 |
1990年 | 4550篇 |
1989年 | 4556篇 |
1988年 | 4166篇 |
1987年 | 4144篇 |
1986年 | 4195篇 |
1985年 | 3995篇 |
1984年 | 3249篇 |
1983年 | 2904篇 |
1982年 | 1986篇 |
1979年 | 2926篇 |
1978年 | 2339篇 |
1977年 | 1974篇 |
1976年 | 1983篇 |
1975年 | 2096篇 |
1974年 | 2487篇 |
1973年 | 2559篇 |
1972年 | 2441篇 |
1971年 | 2191篇 |
1970年 | 2222篇 |
1969年 | 2135篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
162.
M Washizu K Kobayashi K Misaka T Hayashi G Kinoshita M Kondo S Aoki H Orima T Washizu 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(5):1051-1053
A 2-year-old female Japanese domestic cat weighing 3.6 kg was presented due to marked abdominal distention and was diagnosed as hepatic cyst. The bile acid concentration of the hepatic cyst was as low as the serum bile acid concentration. The membrane of the cysts was excised from the edge of the compressed hepatic tissue and no other surgical manipulation was performed. This surgical procedure is simple and quick compared to hepatic lobectomy, however, it is necessary to evaluate the fluid of the cyst before performing this procedure. 相似文献
163.
M Krajnicáková E Bekeová I Maracek V Hendrichovsky J Elecko 《Veterinární medicína》1992,37(8):449-458
A postparturient period is characterized by low basal secretion of adenohypophysis gonadotropins with the following appropriate changes in ovarian hormones and their response to the morphology of vaginal epithelium. In this study the dynamics of the cytological picture of vaginal swabs and ovarian hormones 17 beta-oestradiol (E2) and progesterone was investigated in the puerpery of ewes. The objective was to obtain and extend the knowledge of cytological changes in vaginal epithelium and levels of ovarian hormones of ewes after parturition and of their relationships from the first several days after lambing until the 51st day of the period of observation. Vaginal swabs for vaginal cytology were taken from nine ewes on days 1, 4, 7, 14, 17, 21, 25, 34, 42 and 51 after parturition. These swabs were fixed in ether-alcohol 1:1, stained according to the Faltínová-Zidovsky method, embedded in Canada balsam and evaluated by differentiation of cells according to Luksh (1953). Blood samples for E2 and P4 determinations were taken from the jugular vein in the same intervals as vaginal swabs. The serum was centrifuged and stored at -18 degrees C until use. E2 and P4 concentrations were determined radioimmunologically, using kits RIA-test ESTRA and RIA-test PROG from URVJT Kosice. A statistically significant decline (P < 0.05) of percentual representation of basal and parabasal cells (Fig. 1, Tab. I) on day 7 after lambing was replaced by their multiplication from day 14 reaching the values of 66.07 +/- 3.95 on day 42. A statistically significant decrease in intermediary flat cells (Fig. 2, Tab. II) was observed on days 14 (P < 0.001), 34 and 42 (P < 0.01; P < 0.001), in comparison with the first day after lambing. An evaluation of intermediary convoluted cells revealed their highest percentage on days 1 and 17 after parturition (34.65 +/- 4.77-20.62 +/- 12.57) and their decline to values in the range of 6.77 +/- 1.46-7.66 +/- 2.25 on the remaining days of the period of observation. Percent occurrence of superficial flat cells (Fig. 3, Tab. I) ranged from 3.9 +/- 1.10 to 10.63 +/- 7.23 from day 1 to day 51 after lambing. The lowest percentual representation (1.32 +/- 0.79-4.10 +/- 1.89) was recorded for superficial convoluted cells. Multiplication of the evaluated cells was observed, reaching the highest but insignificant representation (P > 0.05) on day 25 of postparturient investigation: 4.10 +/- 1.89 (Fig. 3, Tab. I). 17 beta-oestradiol (E2) concentrations were compared to the -1st day before parturition, when its values varied at the level of 2.45 +/- 0.64 nmol/l serum.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
164.
The administration of 20 mg/kg of acetylsalicylic acid in 18 clinically healthy dogs resulted in a thrombocytopathy with lengthened capillary bleeding time and irreversible aggregation inhibition. Through the set up of individual dilution series, one could conclude the proportional percentage of aggregation functional transfused thrombocytes. The capillary bleeding time was shortened after the intravenous injection of prednisolone (5 mg/kg) without measurable influence on the thrombocytes. Compared to the singular use of cortisone or blood transfusion alone, the effect on capillary bleeding time became magnified when one combined transfusion and corticosteroids. The fresh blood conserves (12 hours) were, with respect to the haemostyptical properties, superior to blood stored for 5 days. The component of aggregation-functional thrombocytes was, due to the prophylactic cortisone application prior to transfusion, not increased. 相似文献
165.
In a flock of sheep to which food with excess copper (= Cu) had been fed for some months 39 animals died of chronic copper toxicosis. In 5 sheep of this flock the plasma concentrations of the enzymes glutamate dehydrogenase (GLDH), sorbitol dehydrogenase (SDH), aspartate-amino-transferase (ASAT) and copper were measured several times over a period of 100 days. At day 23, 58 and 97 needle biopsies of the liver were taken. The biopsies were used for histological examination and Cu-analysis. After 100 days the sheep were slaughtered and chronic copper poisoning was diagnosed by raised Cu concentration and typical histological alterations in the liver. The activities of GLDH and SDH in the plasma of the 5 sheep were consistently above normal, ASAT activity and the plasma Cu level were raised only occasionally. The results of Cu determination in biopsy samples were of little predictive value compared with post mortem Cu analysis of the liver. 相似文献
166.
167.
168.
Daniel J. Burba DVM Michael A. Collier DVM Lawrence E. Default PhD Olivia Hanson-Painton PhD Harold C. Thompson Jr. Claude L. Holder 《Journal of Equine Veterinary Science》1993,13(12):696-703
The uptake and distribution of intramuscularly (IM) administered tritium-labeled polysulfated glycosaminoglycan (3H-PSGAG) in serum, synovial fluid, and articular cartilage of eight horses was quantitated, and hyaluronic acid (HA) concentration of the middle carpal joint was evaluated in a pharmacokinetic study. A full-thickness articular cartilage defect, created on the distal articular surface of the left radial carpal bone of each horse served as an osteochondral defect model. 3H-PSGAG (500 mg) was injected IM, between 14 and 35 days after creation of the defects. Scintillation analysis of serum and synovial fluid, collected from both middle carpal joints at specific predetermined times up to 96 hours post-injection, revealed mean 3H-PSGAG concentrations peaked at 2 hours post-injection. 3H-PSGAG was detected in cartilage and subchondral bone 96 hours post-injection in samples from all eight horses. There were no statistically significant differences in 3H-PSGAG concentration of synovial fluid or cartilage between cartilage defect and control (right middle carpal) joints.
HA assay of synovial fluid revealed concentrations significantly increased at 24, 48, and 96 hours post-injection in both joints. The concentration nearly doubled 48 hours post-injection. However, no statistically significant differences were found between synovial concentrations of HA in cartilage defect and control joints.
3H-PSGAG administered IM to horses, was distributed in the blood, synovial fluid, and articular cartilage. HA concentrations in synovial fluid increased after IM administration of polysulfated glycosaminoglycan. 相似文献
169.
The determination of differentiation and transplantation antigens will be of growing importance in immune diagnosis for individual animals as well as for breeding purposes in populations. Differentiation antigens characterize subsets of cell populations and indicate their functional capacity while transplantation antigens represent markers of individuals of a species. Occurrence and significance of these antigenic systems are briefly reviewed. 相似文献
170.
A. I. Rey & C. J. López-Bote 《Journal of animal physiology and animal nutrition》2001,85(9-10):281-292
The objective of this study was to assess the effect of dietary copper and/or vitamin E supplementation on composition and oxidation of M. longissimus in Iberian pigs and to compare it with meat samples from pigs produced extensively and fed with acorn and grass. Grass had the highest α-tocopherol content (> 150 mg/kg DM), while acorns had the highest copper concentration (78.1 mg/kg DM). Dietary treatment did not affect copper composition in muscle and no interactions were detected between copper and α-tocopherol. The α-tocopherol content in muscle from pigs fed diets supplemented with α-tocopheryl acetate (100 mg/kg feed) was 1.5 times greater (p < 0.0001) than those from pigs receiving a basel diet. M. longisssimus dorsi from pigs fed extensively had a higher concentration of α-tocopherol than those fed in confinement with the basel level of α-tocopheryl acetate, but lower values than pigs fed supplemented levels. Total n -3 fatty acids (p < 0.02) and hematin (p < 0.0001) concentrations were significantly higher in muscle from pigs fed extensively than when fed in confinement. Muscle homogenates from Iberian pigs fed in extensive conditions showed significantly (p < 0.02) higher susceptibility to oxidation than those from pigs fed mixed diets. Dietary α-tocopheryl acetate supplementation (100 mg/kg feed) significantly (p < 0.05) reduced lipid oxidation of muscle, while dietary copper concentration did not modify susceptibility to lipid oxidation. 相似文献