全文获取类型
收费全文 | 2245篇 |
免费 | 170篇 |
国内免费 | 6篇 |
专业分类
林业 | 139篇 |
农学 | 40篇 |
基础科学 | 19篇 |
331篇 | |
综合类 | 421篇 |
农作物 | 48篇 |
水产渔业 | 265篇 |
畜牧兽医 | 932篇 |
园艺 | 76篇 |
植物保护 | 150篇 |
出版年
2023年 | 19篇 |
2022年 | 20篇 |
2021年 | 52篇 |
2020年 | 61篇 |
2019年 | 83篇 |
2018年 | 76篇 |
2017年 | 91篇 |
2016年 | 64篇 |
2015年 | 55篇 |
2014年 | 71篇 |
2013年 | 100篇 |
2012年 | 146篇 |
2011年 | 188篇 |
2010年 | 122篇 |
2009年 | 69篇 |
2008年 | 145篇 |
2007年 | 167篇 |
2006年 | 129篇 |
2005年 | 143篇 |
2004年 | 138篇 |
2003年 | 134篇 |
2002年 | 97篇 |
2001年 | 30篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 18篇 |
1994年 | 11篇 |
1993年 | 2篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有2421条查询结果,搜索用时 234 毫秒
241.
242.
An Amazon River dolphin (Inia geoffrensis) developed a dermatologic syndrome characterized by the occurrence of slow-growing, nodular, s.c. abscesses. Initial biopsies, cultures, and cytologic analysis of needle aspirates from the abscesses indicated steatitis with probable secondary, gram-negative bacterial infection. Treatment with dietary vitamin E supplement and broad-spectrum antibiotics yielded minimal improvement. Subsequent cultures revealed Streptococcus iniae in addition to several gram-negative bacteria. Vigorous surgical management of the abscesses, including lancing, debridement, and irrigation, combined with antimicrobial therapy specific for Streptococcus and gram-negative organisms, and improvement of the animal's diet and environmental water quality led to gradual recovery. When the animal was ill, it demonstrated an inflammatory leukogram and transient uremia. Streptococcus iniae is a serious pathogen of aquacultured fishes and humans and should be included in the differential diagnosis of chronic dermatopathy in river dolphins. Specific antimicrobial therapy, excellent water quality, surgical management of abscesses, and adherence to sanitary protocols should be observed in cases of suspected S. iniae infection in dolphins. 相似文献
243.
Robert J. W. Byrde Christopher W. Harper Margaret E. Holgate Thomas Hunter 《Pest management science》1973,4(3):327-333
Spraying programmes for apple scab and mildew control sometimes had residual effects for one or even two years. Thus, benomyl (0.025% a.i.) and pyridinitril (0.035% a.i.) drastically reduced the subsequent incidence of cankers caused by Nectria galligena on young wood. Apple scab fruit infection, caused by Venturia inaequalis, was also less on trees on which benomyl had been used in the previous season. In the bark of such trees, toxic residues equivalent to 1 to 4 μg benomyl/g fresh wt. were detected by bioassay 7 months after spraying. 相似文献
244.
Jonathan L. Stowater DVM MS Christopher R. Lamb MA VETMB 《Veterinary radiology & ultrasound》1989,30(5):232-239
The ultrasonographic features of paraprostatic cysts in nine dogs are described along with historical, clinical, surgical and pathologic findings. Cysts occurred predominantly in older, large breed dogs (mean age 8 years, range 3–11 years). The most common presenting complaints were depression, inappetance, stranguria, tenesmus and bloody penile discharge. A palpable abdominal mass was the most common physical finding. Ultrasonographically, paraprostatic cysts were usually large anechoic structures; many contained internal septa. Moderately large anechoic cavities or cysts were also detected in the prostatic parenchyma of five dogs, and in two of these communication with the paraprostatic cyst was visualized. There were no clearly distinct ultrasonographic criteria to discriminate septic from nonseptic paraprostatic cysts. 相似文献
245.
Lawrence J. Kleine DVM MS Christopher R. Lamb MA ETMB MRCVS 《Veterinary radiology & ultrasound》1989,30(3):133-141
Diagnostic radiology of the esophagus, stomach, small and large intestine, mesentery, and pancreas is reviewed. Survey and contrast radiography remain the principal imaging methods used to evaluate gastrointestinal diseases in animals. Of the other imaging techniques, scintigraphy has potential in assessment of esophageal and gastric motility disorders, and detection of intestinal hemorrhage. Ultrasonography is useful for imaging the pancreas and gastrointestinal mass lesions. 相似文献
246.
Peter C. Phillifs Christopher C. Kohler William L. Muhlach 《Journal of the World Aquaculture Society》1992,23(2):98-113
The plasmid vector, pBRd-AK1-BGH4.6.10 (pBGH), containing the bovine growth hormone sequence driven by an avian retroviral long terminal repeat (LTR) was microinjected at 0.1, 0.5, 1 or 5 ng of pDNA/20 nl of physiological saline into tilapia, Oreochromis mossambicus × O. niloticus embryos. In 24 replicates, normally 60 zygotes were microinjected with either the entire linear 8.5 kb pBGH/ClaI vector or a 3.8 kb pBGH/SalI restriction fragment. Overall mean survival to fry hatching was 7.6% in plasmid DNA-microinjected, 15.6% in sham-microinjected and 48.1% in uninjected control embryos. There were no significant ( P > 0.05) differences in survival to hatching between those embryos microinjected with the 3.8 or the 8.5 kb restriction fragment, nor was there a trend toward decreasing survival as the plasmid DNA concentration increased from 0.1 to 5 ng. The significant ( P < 0.05) increase in survival among uninjected control embryos to hatching indicates that microinjection trauma was the major cause of mortality. Large quantities of plasmid DNA were recovered from pooled-embryo samples. Multiple bands (positive signals) were detected usually in the high molecular weight (HMW) genomic DNA regions. Position shifting of these HMW bands upon digesting with various restriction endonucleases provided evidence for plasmid DNA integration into tilapia embryo chromosomal DNA. Otherwise, these positive signah may have been end-twnd ligations of increasingly longer plasmid DNA constructs. Putative transgenic O. mossmbicus × O. niloticus were found among eight of 27 surviving adults. 相似文献
247.
Alan B. Hadaway Fred Barlow Christopher R. Turner Leonard S. Flower 《Pest management science》1977,8(2):172-176
Tests to evaluate candidate insecticides and formulations for tsetse control are described, and some data are presented to indicate that some new synthetic pyrethroids (e.g. permethrin and NRDC 161) are effective for a long period at such extremely low doses that they could have a pronounced influence on future tsetse control operations. 相似文献
248.
249.
The structure of the dairy farm industry has been changing rapidly in recent years. Milk production has increased, with dramatic increases in milk produced per cow and with a steep decline in number of milk cows and fewer farms with larger herds. The change in dairy farm size has not been uniform across regions. The growth in farm size has occurred much more rapidly in the Pacific and South regions than in the traditional dairy-producing regions (Upper Midwest, Northeast, and Corn Belt). Using USDA data to examine costs and returns over time reveals that the incentives to produce milk have been much greater in the Pacific and South regions in recent years. Although the cash costs are similar across regions, accounting for all costs including unpaid factors such as labor and capital replacement yields a clear advantage for the Pacific region. Dairy farm size and cost of production are jointly determined. The incentive to increase farm size is derived from the economies of size that may be achieved by spreading the capital, labor, and managerial costs across more units of milk production. Empiric evidence from previous studies indicates a declining cost of production over a large range of herd sizes. Even in the presence of a flat average cost curve, the incentive to maximize farm income provides incentive to increase production. Adjustment costs may fix dairy production facilities in their current use. Those firms facing higher adjustment costs because of individual or regional characteristics or because of different timing of growth will be smaller or grow more slowly than if they faced smaller adjustment costs. This situation may explain the continued lag of farm size and technology adoption in the traditional dairy producing regions relative to the Pacific and South regions where the more recent population growth coincided with the presence of modern, large-scale production technologies. Finally, dairy marketing policies almost certainly have affected the structure and regional pattern of dairy farm size and production. For the most part, however, the policy effects have been of indirect nature. The Pacific region has grown (despite having the lowest average price) by taking advantage of economies of size by specializing in milking cows. The United States dairy industry is a technologically advanced, well-managed, and economically important sector of United States agriculture. Future challenges include the ability to remain viable economically while dealing with environmental and social sustainability issues in the form of new constraints from formal policies and from consumer perceptions. 相似文献
250.
THE FIRST TWENTY-ONE YEARS OF VETERINARY DIAGNOSTIC ULTRASOUND 总被引:2,自引:0,他引:2
Christopher R. Lamb MA VETMB MRCVS Jon L. Stowater DVM MS Frank S. Pipers DVM PhD 《Veterinary radiology & ultrasound》1988,29(1):37-45
The veterinary literature of 1966–1986 was searched for articles and books related to the use of diagnostic ultrasound in animals. There were 492 references, categorized as follows: general, 30; small animal applications, 169; large animal applications, 248; blood pressure measurement, 23; ultrasound-guided biopsy, 4; miscellaneous, 18. 相似文献