全文获取类型
收费全文 | 9539篇 |
免费 | 77篇 |
国内免费 | 48篇 |
专业分类
林业 | 359篇 |
农学 | 102篇 |
基础科学 | 35篇 |
1348篇 | |
综合类 | 2054篇 |
农作物 | 349篇 |
水产渔业 | 67篇 |
畜牧兽医 | 4798篇 |
园艺 | 275篇 |
植物保护 | 277篇 |
出版年
2019年 | 30篇 |
2018年 | 33篇 |
2016年 | 24篇 |
2015年 | 28篇 |
2014年 | 43篇 |
2013年 | 41篇 |
2012年 | 856篇 |
2011年 | 989篇 |
2010年 | 181篇 |
2009年 | 142篇 |
2008年 | 743篇 |
2007年 | 772篇 |
2006年 | 715篇 |
2005年 | 695篇 |
2004年 | 647篇 |
2003年 | 584篇 |
2002年 | 537篇 |
2001年 | 376篇 |
2000年 | 428篇 |
1999年 | 161篇 |
1998年 | 34篇 |
1997年 | 29篇 |
1996年 | 25篇 |
1995年 | 31篇 |
1994年 | 37篇 |
1993年 | 63篇 |
1992年 | 56篇 |
1991年 | 56篇 |
1990年 | 46篇 |
1989年 | 61篇 |
1988年 | 67篇 |
1987年 | 54篇 |
1986年 | 41篇 |
1985年 | 40篇 |
1984年 | 56篇 |
1983年 | 44篇 |
1982年 | 51篇 |
1981年 | 47篇 |
1980年 | 49篇 |
1979年 | 38篇 |
1978年 | 55篇 |
1977年 | 49篇 |
1976年 | 44篇 |
1975年 | 28篇 |
1974年 | 46篇 |
1973年 | 55篇 |
1972年 | 54篇 |
1971年 | 35篇 |
1970年 | 27篇 |
1960年 | 18篇 |
排序方式: 共有9664条查询结果,搜索用时 71 毫秒
41.
The brain of a 6-year-old Holstein cow, which showed progressive neurologic symptoms during several months, was examined by histopathologic methods. Many round or oval-shaped cytoplasmic inclusions were observed, mainly in neurons of the temporal lobe and the hippocampus. Those inclusions were faintly eosinophilic with hematoxylin and eosin and positive with Bielschowsky's silver stain. Immunohistochemically, the inclusions were recognized by antiubiquitin and antiphosphorylated tau antibodies. Ultrastructurally, the inclusions were globular and well demarcated from the rest of the cytoplasm, lacked limiting membranes, and were mainly composed of straight fibrils about 15 nm in width. The structure of the inclusions was similar to that of Pick bodies in Pick's disease of humans. The pathogenesis of this bovine condition is not known. 相似文献
42.
Disease-induced variations of plasma albumin (ALB) and alpha 1-acid glycoprotein (AAG) levels were investigated in dogs. Lower ALB (sometimes > 50% reduction) and higher AAG (sometimes > 10-fold increase) levels were observed in dogs with various diseases. Drug binding was determined at therapeutic concentrations using normal, low-ALB and high-AAG dog plasma. The binding percentages of the ALB-binding drugs decreased in low-ALB plasma, resulting in a large increase in unbound drug, particularly for naproxen (a 13-fold increase). The binding percentages of all AAG-binding drugs investigated in this study increased in high-AAG plasma, resulting in a large decrease in unbound drug, particularly for quinidine (99% decrease). The fluctuation in the unbound fraction of drugs could affect their efficacy or could cause side-effects. Veterinary clinicians should monitor the ALB and AAG levels in the plasma of patients and correct dosage regimens according to these levels, where field conditions permit this, in order to ensure the proper usage of drugs with high affinity for ALB or AAG. 相似文献
43.
作者研究日粮干物质中不同代谢能含量对试验的黑白花品种4~15.5月龄小公牛活重增长中代谢能利用效率的影响,证明日粮代谢能含量,影响了饲料干物质消耗及其消化率、活重日增长量、代谢能有效率、增长量的能量价值。研究了测定代谢能生产效力的方法,及其对日粮和饲料评价的影响。 相似文献
44.
Takahashi S Hirai N Shirai M Ito K Asai F 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2011,73(7):953-956
The aim of this study was to examine the blood coagulation profiles of ferrets and compare them with those of rats. The ferret activated partial thromboplastin time (aPTT) was slightly longer than the rat aPTT. In contrast, the ferret prothrombin time and thrombin time were profoundly shorter than the corresponding rat values. The fibrinogen level in ferret plasma was 2 times higher than that in rats. Heparin prolonged all blood coagulation times in a concentration-dependent manner in both ferret and rat plasma. A significantly (P<0.01) higher concentration of heparin was required to double the aPTT in ferrets than rats. These blood coagulation data for ferrets will be useful in experimental animal studies. 相似文献
45.
Perri AF Mejía ME Licoff N Lazaro L Miglierina M Ornstein A Becu-Villalobos D Lacau-Mengido IM 《Veterinary parasitology》2011,178(3-4):311-318
Parasitism in cattle is known to impair growth and development. Recent findings suggest that productivity of adult animals is also affected, but little is known about the physiological mechanisms involved. Furthermore, development of nematode resistance to drugs makes imperative the search of management practices that avoid whole herd treatment. We undertook an epidemiological and endocrine study in a grass based dairy farm in Argentina to study the effect of parasites on milk production and the underlying mechanisms involved, and identify individual animals that would benefit from antiparasitic treatment. All the cows in the dairy were followed monthly for egg parasite output in feces. Samples were cultured for genera determination. Milk production and reproductive results were recorded and periodical bleedings for hormone determination were performed. Nematode egg output (EPG) was maximal in late Summer and Autumn and minimal in Spring in coincidence with the Ostertagia inhibition-disinhibition cycle as this genus had the highest prevalence in all the study. The highest proportion of positive samples was found in the high producing herd and maximal counts were found in the peripartal period. Milk production did not correlate with EPG mean values but, when cows were grouped by EPG positivity around parturition, a significant difference in total milk production between EPG null and positive cows was observed. Positive cows produced 7%, 12% or 15% less milk than null EPG cows, depending on the sampling month/s chosen for classification. The highest difference was seen when both prepartum and postpartum samples were taken into account. No difference in lactation length and a marginal effect on partum to first service interval were encountered. Endocrine studies revealed a decrease in serum growth hormone (GH), type I insulin-like growth factor (IGF-I) and prolactin during lactation in cows with positive EPG in the first postpartum sample with respect to null EPG cows at that time. GH levels decreased and prolactin and IGF-I levels increased in both groups of cows from month 0 to 6 in milk. Serum insulin levels remained stable throughout lactation and were similar in both groups of cows. In conclusion, EPG around parturition may be a useful tool for identifying cows that will have a decrease in productivity due to parasite effects and would possibly benefit from an antiparasitic treatment. Besides, our results suggest that detrimental effect of parasites on milk production may be mediated by GH, IGF-I and prolactin serum levels. 相似文献
46.
47.
Ogawa H Sanada Y Sanada N Kudo M Tuchiya K Kodama T Uetsuka K 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2011,73(6):837-840
A 5-month-old female Citron-crested Cockatoo (Cacatua sulphurea citrinocristata) that was born and hand-reared in Japan died with suspected proventricular dilatation disease (PDD). Macroscopic and microscopic examinations of the bird revealed characteristic features of PDD, i.e., distention of the proventriculus and infiltration of lymphocytes and plasma cells in ganglia of various organs and in central and peripheral nerves. A linkage of this PDD case to infection with avian bornavirus (ABV) was documented by RT-PCR amplification of the virus genomes from the affected bird. Phylogenetic analysis revealed that the ABV identified in this study clustered into the genotype 2, which is one of the dominant ABV genotypes worldwide. To the best of our knowledge, this is the first report of a natural case of PDD associated with ABV infection in Japan. 相似文献
48.
49.
Establishment of a potency test by ELISA for a rabies vaccine for animal use in Japan 总被引:2,自引:0,他引:2
Gamoh K Shimazaki Y Senda M Makie H Itoh O Muramatsu M Hirayama N Hatakeyama H 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2003,65(6):685-688
The ELISA we developed was able to determine the antigen content and was suitable for a potency test, and we described a relative potency assay method which determines the potency of test vaccines by comparing the ELISA value of a test vaccine to that of a reference vaccine. In the present study, we standardized the reference vaccine used for determining the potencies of test vaccines, and established a potency test by ELISA. We evaluated the proposed reference vaccine by the neutralizing antibody responses in dogs after vaccination, by the challenge protection test in guinea pigs (GP potency test), which is the earlier official potency test used in Japan, and by the NIH potency test, which is widely used throughout the world. The results showed that a 4-fold dilution of the proposed reference vaccine induced sufficient immunity in dogs. A 3-fold dilution of the proposed reference vaccine passed the GP potency test. The international units (IU) calibrated by the NIH potency test were 3.7 IU/dose. From the results and the WHO recommendation that veterinary rabies vaccines should have a potency of at least 1.0 IU/dose, we determined to dilute the proposed reference vaccine by 3 fold and regarded it as the reference vaccine. Finally, we confirmed that there is a good agreement between the results of the potency test by ELISA and the results of the GP potency test. The establishment of the potency test by ELISA has made it possible to monitor the potency in the production process and has contributed to the stable production of the vaccine. 相似文献
50.
Kühn N Gröne A Pagan O Bacciarini LN 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2003,50(7):359-362
A captive 16-year-old male camel (Camelus ferus bactrianus) was euthanized after a prolonged period of inappetence leading to cachexia. At necropsy, there was a 7 cm large, tan, firm, well-demarcated nodule in the tunica muscularis and serosa of the distal region of C3. Histologically, a gastric adenocarcinoma was diagnosed. Numerous metastases were found in the liver and the hepatic lymph nodes, in the wall of the portal vein and the aorta, in the lung, heart, and pleura parietalis. Osseous metaplasia was found within the pleural and aortic metastases. In the mucosa of the glandular region of the C3 compartment a diffuse marked hypertrophy of rugae resembling cerebral convolutions was observed. The lesion was characterized by glandular hyperplasia and stromal inflammation and oedema. These changes closely resembled Menétrier's disease described in humans. To our knowledge, this is the first report of concomitant metastatic gastric adenocarcinoma and gastric hyperplasia in a camel. 相似文献