全文获取类型
收费全文 | 4458篇 |
免费 | 296篇 |
国内免费 | 4篇 |
专业分类
林业 | 172篇 |
农学 | 86篇 |
基础科学 | 24篇 |
494篇 | |
综合类 | 693篇 |
农作物 | 134篇 |
水产渔业 | 245篇 |
畜牧兽医 | 2566篇 |
园艺 | 107篇 |
植物保护 | 237篇 |
出版年
2021年 | 59篇 |
2020年 | 71篇 |
2019年 | 76篇 |
2018年 | 64篇 |
2017年 | 82篇 |
2016年 | 80篇 |
2015年 | 75篇 |
2014年 | 96篇 |
2013年 | 267篇 |
2012年 | 211篇 |
2011年 | 274篇 |
2010年 | 158篇 |
2009年 | 134篇 |
2008年 | 229篇 |
2007年 | 215篇 |
2006年 | 219篇 |
2005年 | 199篇 |
2004年 | 225篇 |
2003年 | 212篇 |
2002年 | 180篇 |
2001年 | 100篇 |
2000年 | 97篇 |
1999年 | 60篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 36篇 |
1994年 | 30篇 |
1993年 | 29篇 |
1992年 | 67篇 |
1991年 | 57篇 |
1990年 | 61篇 |
1989年 | 60篇 |
1988年 | 57篇 |
1987年 | 47篇 |
1986年 | 41篇 |
1985年 | 38篇 |
1984年 | 39篇 |
1983年 | 35篇 |
1981年 | 26篇 |
1980年 | 34篇 |
1979年 | 46篇 |
1978年 | 35篇 |
1976年 | 26篇 |
1974年 | 36篇 |
1973年 | 34篇 |
1972年 | 30篇 |
1971年 | 30篇 |
1970年 | 29篇 |
1969年 | 34篇 |
排序方式: 共有4758条查询结果,搜索用时 17 毫秒
1.
A urinary bladder mass in a 12-year-old spayed female West Highland White Terrier was diagnosed after exploratory surgery and biopsy as a transitional cell carcinoma. Four months later the dog presented with an ulcerated plaque-like cutaneous lesion at the previous surgical incision site; concurrent inguinal lymphadenopathy and recurrence of the urinary bladder mass were identified. Transitional cell carcinoma was diagnosed at all 3 sites. Although a definitive relationship cannot be established between the initial surgery for urinary bladder mass and the resultant subcutaneous lesion, surgical implantation should be considered as a source for the neoplastic cells. 相似文献
2.
H M Syme J C Scott-Moncrieff N G Treadwell M F Thompson P W Snyder M R White J W Oliver 《Journal of the American Veterinary Medical Association》2001,219(12):1725-8, 1707-8
An 11-year-old spayed female Labrador Retriever and a 9-year-old castrated male miniature Poodle were evaluated because of clinical signs of hyperadrenocorticism. Cortisol testing did not support a diagnosis of hypercortisolemia in either dog; however, imaging studies revealed unilateral adrenal tumors in both dogs. Serum concentrations of 17-hydroxyprogesterone, progesterone, and estradiol were high in both dogs, and androstenedione concentrations were also high in 1 dog. It is suspected that sex hormone secretion by the adrenal tumors in these dogs resulted in clinical signs of hyperadrenocorticism. Clinical signs and hormonal abnormalities resolved in the male dog after surgical resection of the tumor. There was no improvement in clinical signs after treatment with mitotane in the female dog, which died 2 months after diagnosis. Histologic evaluation confirmed the presence of adrenocortical carcinoma in both dogs. 相似文献
3.
Washed and unwashed red blood cells (RBC) from young calves, adult cattle, hamsters and humans were incubated with Leptospira interrogans serovars pomona and ballum. Washed cells suspended in saline were always haemolysed while unwashed cells and those which were washed and resuspended in plasma were never haemolysed, despite the presence of large numbers of organisms within the culture supernatant. Pomona produced greater haemolysis of cattle and human RBC than did ballum, but with hamster RBC ballum produced greater haemolysis than did pomona. A group of 6- to 9-month-old cattle infected with pomona showed no signs of clinical disease and RBC taken from them before infection and during the development of antibodies to pomona were haemolysed by pomona only after the cells were washed. Plasma therefore appears to have a protective function. This in vitro protective function of plasma even extended to plasma from young seronegative calves. 相似文献
4.
5.
Carl D. Webster Kenneth R. Thompson Ann M. Morgan Ebony J. Grisby Siddhartha Dasgupta 《Journal of the World Aquaculture Society》2001,32(1):79-88
Abstract.— In an effort to feed sunshine bass Morone chrysops × M. saxatilis efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were grown in cages and fed one of four feeding frequencies: once/d, twice/d, once every other day (I X/EOD), and twice every other day (2X/EOD) for 21 wk. Juvenile sunshine bass were fed a commercial floating diet containing 40% protein and 11.5% lipid. One hundred fish were hand-counted and stocked into each of 12 3.5-m3 cages with three replications per treatment. At the conclusion of the study, percentage weight gain of sunshine bass fed twice/d was significantly (P < 0.05) higher (1,850%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/d was significantly higher (2.1%/d) compared to fish fed all other feeding regimes, while fish fed once/d had a higher SGR (2.0%/d) compared to fish fed I X/EOD (1.6%/d) and 2X/EOD (1.8%/d). Percentage survival was not significantly different (P > 0.05) among all treatments and averaged 70.4%r. Feed conversion ratio (FCR) of fish fed twice/d was significantly higher (2.40) compared to fish fed all other feeding regimes. Percentage fillet weight of fish fed twice/d was significantly higher (27.8%) compared to all other treatments. Percentage moisture, protein, lipid, and ash in fillet were not significantly different among all treatments and averaged 75.7%, 19.4%, 3.5%, and 1.2%n, respectively (wet-weight basis). Based upon data from the present study, it appears that producers growing juvenile sunshine bass in cages may want to feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions. However, economic analysis needs to be conducted to determine if feeding twice/d is profitable. 相似文献
6.
The survival of Leptosphaeria maculans , which causes phoma stem canker (blackleg), on oilseed rape residues ( Brassica napus ) in South Australia was investigated. Using a quantitative polymerase chain reaction (PCR) assay for L. maculans DNA, the pathogen was mainly detected in the upper 5 cm of the soil profile, including residues on the soil surface. As the size of organic matter particles in the soil decreased, so did the quantity of L. maculans detected in them. To obtain representative data for a field, at least 30 subsamples needed to be collected over the 0·81 ha area studied. In a survey of 49 commercial fields in South Australia, most L. maculans was detected in fields 1 year after oilseed rape had been grown, with less detected after 2 years and negligible amounts 3 years or more after cropping. The diagnostic DNA-based assay for L. maculans reduced the time and cost of studying L. maculans survival in soil and increased the sensitivity and accuracy of results compared with estimates of propagule number of colony-forming units on a semiselective medium. 相似文献
7.
8.
Christopher L. Mariani DVM Simon R. Platt BVMS MRCVS Susan M. Newell DVM MS Scott P. Terrell DVM Cheryl L. Chrisman DVM MS EDS Roger M. Clemmons DVM PhD 《Veterinary radiology & ultrasound》2001,42(6):524-531
A 3-year-old neutered female mixed breed dog was examined because of severe, generalized seizure activity, tetraparesis, and encephalopathic signs. Cerebrospinal fluid (CSF) evaluation was unremarkable except for a mild increase in protein. Serum and CSF titers for infectious diseases were negative. Magnetic resonance (MR) imaging examination of the brain was performed and lesions were found within the cerebral gray matter of the temporal and parietal lobes. The lesions had increased signal intensity on T1, T2, and proton density-weighted images. There was mild inhomogeneous enhancement following intravenous contrast medium administration. Neurologic status improved and the seizures were well controlled, but the dog never regained normal mentation and euthanasia was performed 10 weeks after initial evaluation. At necropsy, severe cerebral cortical necrosis was found in the regions corresponding to the lesions seen on MR imaging examination. Large numbers of fat-containing macrophages (gitter cells) were found within these areas, and are thought to be responsible for the characteristic hyperintensity seen on the MR images. 相似文献
9.
Monorchidism in the horse 总被引:1,自引:0,他引:1
Six horses with monorchidism, identified at surgery for cryptorchidectomy, are reported. All six presented with a single scrotal testis. Following surgical removal of one testis, they were either hormonally, anatomically or behaviourally determined to be geldings. Three other horses reported in the literature are reviewed. Of these nine cases of monorchidism, eight were thought to be caused by testicular degeneration and one by testicular agenesis. The vaginal process was present in all of the former and absent in the latter. The left side was involved in five of these eight horses. In seven, the epididymis was absent and, in the remaining two, only the epididymal tail was present. The condition was thought to be congenital in the six horses in this series. A surgical approach to identify accurately monorchid horses is described. 相似文献
10.