全文获取类型
收费全文 | 151915篇 |
免费 | 8523篇 |
国内免费 | 78篇 |
专业分类
林业 | 6187篇 |
农学 | 5104篇 |
基础科学 | 956篇 |
19739篇 | |
综合类 | 21608篇 |
农作物 | 5720篇 |
水产渔业 | 7915篇 |
畜牧兽医 | 81323篇 |
园艺 | 1975篇 |
植物保护 | 9989篇 |
出版年
2020年 | 1273篇 |
2019年 | 1545篇 |
2018年 | 2461篇 |
2017年 | 2759篇 |
2016年 | 2542篇 |
2015年 | 2184篇 |
2014年 | 2692篇 |
2013年 | 6335篇 |
2012年 | 4787篇 |
2011年 | 5721篇 |
2010年 | 3905篇 |
2009年 | 3935篇 |
2008年 | 5713篇 |
2007年 | 5505篇 |
2006年 | 5104篇 |
2005年 | 4687篇 |
2004年 | 4484篇 |
2003年 | 4613篇 |
2002年 | 4190篇 |
2001年 | 5229篇 |
2000年 | 5107篇 |
1999年 | 4129篇 |
1998年 | 1629篇 |
1997年 | 1618篇 |
1996年 | 1490篇 |
1995年 | 1763篇 |
1994年 | 1489篇 |
1993年 | 1536篇 |
1992年 | 3037篇 |
1991年 | 3260篇 |
1990年 | 3140篇 |
1989年 | 3183篇 |
1988年 | 2888篇 |
1987年 | 2863篇 |
1986年 | 2791篇 |
1985年 | 2671篇 |
1984年 | 2205篇 |
1983年 | 1926篇 |
1982年 | 1344篇 |
1979年 | 1945篇 |
1978年 | 1515篇 |
1977年 | 1356篇 |
1976年 | 1315篇 |
1975年 | 1399篇 |
1974年 | 1602篇 |
1973年 | 1672篇 |
1972年 | 1607篇 |
1971年 | 1395篇 |
1970年 | 1418篇 |
1969年 | 1365篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
D A Ward K S Latimer R M Askren 《Journal of the American Veterinary Medical Association》1992,200(10):1503-1506
Squamous cell carcinoma is an uncommon tumor of the cornea in dogs. A 12-year-old Shih Tzu with a history of chronic keratoconjunctivitis sicca was diagnosed as having squamous cell carcinoma of the corneoscleral limbus. The lesion was treated by surgical resection and cryotherapy. One year after surgery, multiple tumors, apparently unrelated to the first tumor, appeared on the same cornea. Keratoconjunctivitis sicca may have predisposed the dog to corneal squamous cell carcinoma development. 相似文献
92.
The dietary lysine requirement of juvenile red drum Sciaenops ocellatus was reevaluated in two separate experiments. In the first experiment, lyophilized red drum muscle was combined with an L-form crystalline amino acid premix to yield diets containing approximately 35% protein on a dry-matter basis. Gradations (0.25%) of L-lysine HCl were added to the basal diet containing approximately 1.0% lysine. Each diet was fed to triplicate groups of juvenile red drum initially weighing 6–7 g for 8 weeks. Based on growth and feed efficiency data, the lysine requirement (±SE) was determined to be 1.55% (±0.079%) of dry diet or 4.430% of dietary protein. In a second experiment, the lysine requirement of red drum was investigated with diets containing 35% intact protein from zein and red drum muscle. Each of the zein-based diets containing incremental levels of lysine was fed to triplicate groups of juvenile red drum initially weighing 1–2 g for 8 weeks. A crystalline amino acid test diet serving as a control in this experiment significantly outperformed the zein-based diets, and palatability of those diets was questionable due to an obvious change in feeding behavior of the fish. Due to the inferior performance of the fish fed the zein-based diets, the authors were not successful in determining a requirement with these diets. Thus, a lysine requirement of 1.55% of dry diet (4.43% of dietary protein) as determined in the first experiment is recommended for juvenile red drum. 相似文献
93.
Meat regulations also involve game inspection. This publication deals with the regulations concerning furred game intended for slaughter and furred game hunted for food. 相似文献
94.
Two cases of H.c.c. which occurred in winter 1987 in Vienna are described. Case one was a female Chow-Chow, 8 weeks of age, that died from the peracute form of the disease. The diagnosis was confirmed by histology and direct immunofluorescence. Case two, a 9-month old female Kuvacz, showed clinical signs of the subacute form of H.c.c. She was hospitalized and therapy was successful. The disease was diagnosed by the typical clinical signs and the raise of antibodies in paired serum samples. Etiology, clinical signs and immunology of H.c.c. are discussed. 相似文献
95.
M C Rick 《Veterinary Clinics of North America: Equine Practice》1989,5(2):407-428
Diagnosis, evaluation, and management of the various grades of rectal tears is discussed. Surgical techniques, which include direct closure, diverting colostomies, and placement of temporary rectal liners, are detailed. Also, rectal prolapses and various methods of repair are outlined. 相似文献
96.
Duration of maternal immunity to peste des petits ruminants 总被引:1,自引:0,他引:1
97.
The responses of some clinical and microbiological parameters of periodontal disease (PD) in sheep were examined subsequent to transferring animals between PD-affected and PD-free farms. Previously healthy animals showed transient deterioration in some clinical, but not microbiological parameters, which suggests either that a different microbiota to the one studied may be more important in the initiation of the disease, or that sampling did not intercept periods of destructive disease activity in the early lesions. In sheep with established disease, those parameters indicative of periodontitis which included pocket depth and bleeding on probing as well as the proportions of black-pigmented Bacteroides species were not significantly altered by environmental changes. This observation suggests that once the disease is established on PD-affected farms, the hand, some clinical signs of the disease including lengthening and mobility of incisor teeth increased in sheep on the PD-affected farm relative to the PD-free farm. This suggests that the disease may have a complex aetiology. 相似文献
98.
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
99.
Enzyme-linked immunosorbent assay for the detection of circulating antigens of Toxoplasma gondii in the serum of cats 总被引:1,自引:0,他引:1
M R Lappin C E Greene A K Prestwood D L Dawe R L Tarleton 《American journal of veterinary research》1989,50(9):1586-1590
An ELISA was developed to detect circulating antigens of Toxoplasma gondii in the serum of cats. For the experiment, toxoplasmosis was induced in a group of cats by oral administration of bradyzoites. An ELISA that detects anti-Toxoplasma IgG, an ELISA to detect circulating antigens, and fecal examinations were performed on samples from each cat for 1 year after inoculation. When coupled with IgG-class antibody measurement, antigen detection can aid in the diagnosis of some cases of subclinical feline toxoplasmosis. 相似文献
100.
M. A. Gomez J. A. Navarro S. Gomez P. Camara J. C. Gomez A. Bernabé 《Anatomia, histologia, embryologia》1989,18(4):305-315
The structure and ultrastructure of the adenohypophyseal pars distalis in kids of the Murciano-granadiana breed (18 males and 12 females), aged 2-3 months and with an average carcass weight of 8 kg has been studied. Techniques of staining (Tetrachrome Herlant's, and Cleveland-Wolfe) and histochemistry (PAS, PAS-OG and BA-PAS-OG) contrasted with immunolabelling (PAP) have been used. In addition an ultrastructural study has been made and nucleus and cytoplasm, secretory granules, mitochondria and lysosomes have been measured with a semiautomatic image analyzer (IBAS-1). TSH cells are found in sagittal section in the anterior area and in an antero-caudodorsal band, and transversally in the ventral and medial region; they are 6% and their average size is 14.15 microns. Ultrastructurally they are a single cellular type with spherical granules whose size is 195 nm in males and 149 in females; these granules are characterized by a clear halo and a variable electronic density. The rough endoplasmic reticulum is found as slightly enlarged vesicles with a homogeneous and moderately electro-dense content or in concentric stratifications. 相似文献