全文获取类型
收费全文 | 313839篇 |
免费 | 17067篇 |
国内免费 | 708篇 |
专业分类
林业 | 24588篇 |
农学 | 14227篇 |
基础科学 | 3009篇 |
46909篇 | |
综合类 | 41953篇 |
农作物 | 17737篇 |
水产渔业 | 18408篇 |
畜牧兽医 | 132677篇 |
园艺 | 6539篇 |
植物保护 | 25567篇 |
出版年
2019年 | 3779篇 |
2018年 | 4510篇 |
2017年 | 4904篇 |
2016年 | 5089篇 |
2015年 | 4505篇 |
2014年 | 5871篇 |
2013年 | 16486篇 |
2012年 | 8010篇 |
2011年 | 10423篇 |
2010年 | 8196篇 |
2009年 | 8641篇 |
2008年 | 9775篇 |
2007年 | 8959篇 |
2006年 | 9175篇 |
2005年 | 8448篇 |
2004年 | 8227篇 |
2003年 | 8020篇 |
2002年 | 7263篇 |
2001年 | 8111篇 |
2000年 | 7941篇 |
1999年 | 6949篇 |
1998年 | 4371篇 |
1997年 | 4415篇 |
1996年 | 4092篇 |
1995年 | 4788篇 |
1994年 | 4158篇 |
1993年 | 3860篇 |
1992年 | 5521篇 |
1991年 | 5778篇 |
1990年 | 5561篇 |
1989年 | 5560篇 |
1988年 | 4982篇 |
1987年 | 5013篇 |
1986年 | 5000篇 |
1985年 | 5183篇 |
1984年 | 4575篇 |
1983年 | 4243篇 |
1982年 | 3308篇 |
1981年 | 3123篇 |
1980年 | 3092篇 |
1979年 | 4210篇 |
1978年 | 3593篇 |
1977年 | 3259篇 |
1976年 | 3121篇 |
1975年 | 3118篇 |
1974年 | 3541篇 |
1973年 | 3545篇 |
1972年 | 3263篇 |
1971年 | 3147篇 |
1970年 | 3024篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
42.
C Dorn A Schroeter A Miko D Protz R Helmuth 《Berliner und Münchener tier?rztliche Wochenschrift》2001,114(5-6):179-183
In the last years the number of isolations of Salmonella enterica subspecies enterica serovar paratyphi B (S. paratyphi B) sent to the national salmonella reference laboratory of Germany has increased steadily. Most of the isolates originated from fowl or poultry products. The bacteriological, serological and biochemical properties of the isolates were investigated. Special emphasis was given to the utilization of d-tartrate which subgroups the serovar. All of them belonged to the d-tartrate positive variant, which is generally considered less virulent for humans and was formerly called S. java. The performance of various tests is compared and in addition the possibility of the spread within the production line is discussed. 相似文献
43.
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
44.
Pilot study of the effect of acemannan in cats infected with feline immunodeficiency virus. 总被引:7,自引:0,他引:7
K M Yates L J Rosenberg C K Harris D C Bronstad G K King G A Biehle B Walker C R Ford J E Hall I R Tizard 《Veterinary immunology and immunopathology》1992,35(1-2):177-189
Acemannan, a complex carbohydrate shown to stimulate interleukin-1, tumor necrosis factor alpha and prostaglandin E2 production by macrophages, has also demonstrated antiviral activity in vitro against human immunodeficiency virus, Newcastle disease virus and influenza virus. A pilot study was undertaken to determine acemannan's effect in 49 feline immunodeficiency virus (FIV) infected cats with clinical signs of disease (Stage 3, 4 or 5), 23 of which had severe lymphopenia. Cats received acemannan either by intravenous (Group 1) or subcutaneous (Group 2) injection once weekly for 12 weeks, or by daily oral (Group 3) administration for 12 weeks. Upon entry into the study, cats were randomly assigned to one of the three groups. Laboratory analyses were performed at the beginning of the study and at Weeks 6 and 12. Cats were allowed to continue with a predetermined maintenance regimen of acemannan after completing the 12-week study. Thirteen cats died during the course of treatment. Upon necropsy, the most frequent histopathologic findings were neoplastic, kidney and pancreatic disease. Friedman's two-way ANOVA test showed no significant differences in efficacy among groups administered acemannan by the different routes. Therefore, groups were combined and a signed-ranks test was used to determine changes over time. A significant increase was seen in lymphocyte counts (P < 0.001). Neutrophil counts decreased significantly (P = 0.007), as did incidence of sepsis (P = 0.008). When cats entering with lymphopenia were analyzed separately, a much greater increase in lymphocyte counts was noted (235%) compared with non-lymphopenic cats (42%). A survival rate of 75% was found for all three groups. Thirty-six of 49 animals are alive 5-19 months post-entry. These results suggest that acemannan therapy may be of significant benefit in FIV-infected cats exhibiting clinical signs of disease. 相似文献
45.
46.
Neutralising antibody to bovid herpesvirus 2 was demonstrated in the serum of 31 (10.8%) of 286 heads of cattle in north, south, and west Syria. 38% of titres were 1:2 to 1:8. There is no published report on isolation of this virus in Syria. 相似文献
47.
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
48.
49.
D H Du Plessis 《The Onderstepoort journal of veterinary research》1992,59(2):119-122
The serological reactivity in indirect ELISA of five different bluetongue virus (BTV) serotypes (4, 10, 15, 16 & 20) was compared using polyclonal antisera raised against virus particles and an outer structural protein, VP2. Rabbit and sheep antisera against BTV-10 produced higher ELISA values with their homologous antigens than with heterologous serotypes. A hyperimmune rabbit serum specific for virus particles was able to distinguish heterologous serotypes from each other, but a sheep serum from an infected animal was not. An antiserum directed against VP2, the protein responsible for serotype specificity in neutralization tests, was not serotype-specific in ELISA and cross-reacted with other serotypes. The discriminatory ability of a BTV-4 antiserum was improved by cross-absorption with heterologous antigens. This greatly reduced the ELISA signals with heterologous serotypes and produced an antiserum that was effectively serotype-specific. 相似文献
50.
在查清天津市园林主要花灌木刺吸口器害虫桃粉蚜、绣线菊蚜、棉蚜和山楂红蜘蛛发生消长规律的基础上 ,确定了防治适期和结合点 ,筛选出 10 %吡虫啉、绿灵、蚧螨灵、 1. 8%齐螨素和花保5种低、无毒药剂 ,防效均达到 90 %以上。查出天敌 13种 ,并对优势种作了取食量调查 相似文献