全文获取类型
收费全文 | 253962篇 |
免费 | 15299篇 |
国内免费 | 660篇 |
专业分类
林业 | 23757篇 |
农学 | 14072篇 |
基础科学 | 2973篇 |
43255篇 | |
综合类 | 22340篇 |
农作物 | 17406篇 |
水产渔业 | 16983篇 |
畜牧兽医 | 98974篇 |
园艺 | 6291篇 |
植物保护 | 23870篇 |
出版年
2021年 | 2487篇 |
2020年 | 2888篇 |
2019年 | 3676篇 |
2018年 | 4104篇 |
2017年 | 4520篇 |
2016年 | 4894篇 |
2015年 | 4390篇 |
2014年 | 5739篇 |
2013年 | 16274篇 |
2012年 | 6496篇 |
2011年 | 8509篇 |
2010年 | 7504篇 |
2009年 | 8030篇 |
2008年 | 7886篇 |
2007年 | 6904篇 |
2006年 | 7429篇 |
2005年 | 6517篇 |
2004年 | 6406篇 |
2003年 | 6173篇 |
2002年 | 5495篇 |
2001年 | 6472篇 |
2000年 | 6124篇 |
1999年 | 5638篇 |
1998年 | 4158篇 |
1997年 | 4239篇 |
1996年 | 3957篇 |
1995年 | 4510篇 |
1994年 | 3901篇 |
1993年 | 3585篇 |
1992年 | 4396篇 |
1991年 | 4519篇 |
1990年 | 4236篇 |
1989年 | 4221篇 |
1988年 | 3633篇 |
1987年 | 3691篇 |
1986年 | 3596篇 |
1985年 | 3914篇 |
1984年 | 3592篇 |
1983年 | 3366篇 |
1982年 | 2838篇 |
1981年 | 2747篇 |
1980年 | 2706篇 |
1979年 | 3071篇 |
1978年 | 2801篇 |
1977年 | 2555篇 |
1976年 | 2421篇 |
1975年 | 2333篇 |
1974年 | 2436篇 |
1973年 | 2361篇 |
1971年 | 2075篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Osteomyelitis caused by Cryptococcus neoformans was diagnosed in a three-year-old male Irish wolfhound. The case details and radiological findings of radiolucency and periosteal reaction of the left third metatarsal bone had lead to an initial diagnosis of a malignant bone tumour. Biopsy revealed a fungal granuloma and culture identified the causal organism. A four month course of ketaconazole was instigated and the lameness resolved. Twelve months after the end of treatment there was no recurrence of the problem. 相似文献
32.
R F Nachreiner S J Oschmann L E Edqvist J I Richards 《American journal of veterinary research》1992,53(7):1085-1089
Five studies were performed to determine factors affecting progesterone concentration in skim milk. Results of the first study indicated that progesterone concentration was higher in skim milk of samples kept 16 hours in an ice bath (0 C) than of those left at room temperature (21 C). In the second study, this temperature effect was found to be reversible, with skim milk progesterone concentration increasing when whole milk samples were cooled prior to centrifugation. In the third study, [3H]-labeled progesterone was used to determine the relationship between fat content of foremilk (the first milk obtained from the teats), midmilk (milk obtained midway through milking), and strippings (milk obtained immediately after milking machines have been removed) samples and temperature (4 C and 21 C) on the percentage of progesterone in the skim milk fraction. The relationship between percentage of butterfat and percentage of progesterone in skim milk was linear when the log of these variables was used for calculations. In the fourth study, assayable progesterone in the skim milk fraction of foremilk, midmilk, and strippings was affected by temperature. In the fifth study, a multiple-regression procedure was used to determine the amount of variation in percentage of radioactive progesterone in the skim milk fraction. Independent variables (whole milk butterfat and temperature of incubation [1, 3, 13, 22, 37, and 50 C]) and the natural log of each variable, were entered into a stepwise multiple-regression analysis.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
33.
34.
The case records of 149 dogs examined from 1985 to 1989 with clinical signs of nasal disease were reviewed. Gross rhinoscopy was performed in 119 dogs, and rhinoscopy-assisted pinch biopsy was performed in 109. Rhinoscopy was performed by use of a 2.7-mm rigid fiberoptic endoscope. Mucosal biopsy specimens were obtained with rhinoscopic guidance by use of a 2 x 3-mm biopsy forcep. Gross, cytologic, and histologic findings are summarized. Ninety-four of 119 cases could be evaluated on the basis of diagnostic and follow-up criteria established by the authors. The diagnostic success rate of gross rhinoscopy with rhinoscopy-assisted biopsy was 83% (78 of 94 evaluated cases). Protracted hemorrhage was a complication in 2 of 109 cases in which rhinoscopy-assisted biopsy was performed. It was concluded that rhinoscopy with rhinoscopy-assisted biopsy contributes important diagnostic information in dogs with nasal disease without the relative invasiveness, expense, and risk of surgery. 相似文献
35.
Differences in gas exchange parameters i.e. carbon exchange rate (CER), transpiration (Tr), water vapor conductance (g) were investigated, under a controlled environment, in a semi-dwarf (SD) Triticum aestivum line, its tall (TL) near isoline and the Payne (PA) variety characterized by small leaves. The plants were maintained in: (a) optimal substrate moisture condition (CTR); (b) salinized by watering with a 0.12 m NaCl solution (SLT); (c) water stressed by withholding waterings during a period of six days (STR); (d) stressed and salinized during the same period and with the same saline solution (S + S). CER and Tr were negatively affected by the stresses; SLT and S + S treatments had a higher WUE compared to their respective controls CTR and STR.
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO2 concentration curves contributed to explaining the SD performance. 相似文献
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO
36.
A Yabuki S Suzuki M Matsumot M Kurohmaru Y Hayashi H Nishinakagawa 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(12):1339-1342
The proximal straight tubules of the female mouse kidney exhibit heavy periodic acid Schiff (PAS) staining in their brush borders and numerous cytoplasmic granules. In the present study, the female DBA/2Cr mouse kidney was examined, using various fixatives (formalin, PFA, PLP, Zamboni's, Bouin, or Carnoy solution) and various staining methods (HE, PAS, alcian blue, periodic acid methenamine-silver (PAM), toluidine blue, azan, or Congo red). Under azan and PAM, the staining pattern of the brush border was similar to that of PAS, and few effects of the fixative were observed. Cytoplasmic granules were clearly detected with PAM as well as PAS. However, these granules were not detected with Carnoy solution. Furthermore, distribution of granules differed between PAS and PAM. 相似文献
37.
38.
Evaluation of abomasal outflow diversion as an experimental model of hypochloremic, hypokalemic metabolic alkalosis in lactating cows.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J L Ward D F Smith S L Fubini D M Deuel-Aromando 《Canadian journal of veterinary research》1994,58(1):13-19
Four adult, lactating dairy cows were subjected to diversion (loss) of gastric contents through a T-shaped cannula placed in the cranial part of the duodenum just distal to the pylorus. Diversion was continued for 10 to 12 hours, at which point the cows were very weak and depressed. The volume of effluent during this period ranged from 37.3 to 46.8 L, with the largest volume being produced during the first four hours. All cows became dehydrated, with mean packed cell volume and total plasma protein concentration increasing 30% and 19.6%, respectively, but with only a slight increase in plasma creatinine concentration. Plasma Cl- concentrations decreased from a mean of 97.3 mEq/L at the beginning of diversion to a mean of 87.2 mEq/L at eight hours. This was followed by a plateau or slight increase in concentrations over the final hours of diversion. Plasma K+ concentration followed a similar pattern, decreasing from a mean of 3.9 mEq/L to a mean of 2.94 mEq/L at six hours, followed by increasing values until termination of diversion. No changes in plasma Na+ concentration were noted, except for a mild decrease in one cow. Plasma calcium concentrations decreased significantly, reaching 6.6 +/- 0.6 mEq/L at the end of diversion. Venous pH, plasma HCO3- concentration, and plasma base excess concentration increased during the first four to eight hours of diversion, followed by a gradual decline. Although a mild hypochloremic metabolic alkalosis resulted from diversion of abomasal outflow in all cows, substantiated by a mild increase in plasma strong ion difference, the changes observed were not as great as expected.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
39.
Abstract. A humoral antibody response was demonstrated by ELISA in rainbow trout immunized intraperitoneally with extracts from the branchiuran ectoparasite Argulus foliaceus. A similar immunization protocol produced a higher titre response in a rabbit. Both trout and rabbit identified several antigenic components on immunoblots. ELISA and immunoblotting indicated that rainbow trout and rabbit anti-A. foliaceus sera identified components from the parasitic copepods Lepeophtheirus salmonis and Caligus elongatus. 相似文献
40.