全文获取类型
收费全文 | 2520篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
林业 | 99篇 |
农学 | 29篇 |
基础科学 | 8篇 |
511篇 | |
综合类 | 524篇 |
农作物 | 96篇 |
水产渔业 | 31篇 |
畜牧兽医 | 1110篇 |
园艺 | 5篇 |
植物保护 | 116篇 |
出版年
2023年 | 2篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2016年 | 3篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 4篇 |
2012年 | 351篇 |
2011年 | 369篇 |
2010年 | 63篇 |
2009年 | 31篇 |
2008年 | 240篇 |
2007年 | 226篇 |
2006年 | 192篇 |
2005年 | 149篇 |
2004年 | 156篇 |
2003年 | 143篇 |
2002年 | 140篇 |
2001年 | 89篇 |
2000年 | 87篇 |
1999年 | 54篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1973年 | 2篇 |
1970年 | 5篇 |
1963年 | 2篇 |
1945年 | 2篇 |
1940年 | 2篇 |
1910年 | 1篇 |
1897年 | 1篇 |
1896年 | 1篇 |
1886年 | 2篇 |
1885年 | 6篇 |
排序方式: 共有2529条查询结果,搜索用时 15 毫秒
991.
992.
The value of sunflower seed (SS) in finishing diets was assessed in two feeding trials. In Exp. 1, 60 yearling steers (479 +/- 45 kg) were fed five diets (n = 12). A basal diet (DM basis) of 84.5% steam-rolled barley, 9% barley silage, and 6.5% supplement was fed as is (control), with all the silage replaced (DM basis) with rolled SS, or with grain:silage mix replaced with 9% whole SS, 14% whole SS, or 14% rolled SS. Liver, diaphragm, and brisket samples were obtained from each carcass. In Exp. 2, 120 yearling steers (354 +/- 25 kg) were fed corn- or barley-based diets containing no SS, high-linoleic acid SS, or high-oleic acid SS (a 2 x 3 factorial arrangement, n = 20). Whole SS was included at 10.8% in the corn-based and 14% in the barley-based diets (DM basis). In Exp. 1, feeding whole SS linearly increased DMI (P = 0.02), ADG (P = 0.01), and G:F (P = 0.01). Regression of ME against level of whole SS indicated that SS contained 4.4 to 5.9 Mcal ME/kg. Substituting whole for rolled SS did not significantly alter DMI, ADG, or G:F (8.55 vs. 8.30 kg/d; 1.36 vs. 1.31 kg; and 0.157 vs. 0.158, respectively). Replacing the silage with rolled SS had no effect on DMI (P = 0.91) but marginally enhanced ADG (P = 0.10) and improved G:F (P = 0.01). Dressing percent increased linearly (P = 0.08) with level of SS in the diet. Feeding SS decreased (P < 0.05) levels of 16:0 and 18:3 in both diaphragm and subcutaneous fats, and increased (P = 0.05) the prevalence of 18:1, 18:2, cis-9,trans-11-CLA and trans-10,cis-12-CLA in subcutaneous fat. In Exp. 2, barley diets supplemented with high-linoleic SS decreased DMI (P = 0.02) and ADG (P = 0.007) by steers throughout the trial, whereas no decrease was noted with corn (interaction P = 0.06 for DMI and P = 0.01 for ADG). With barley, high-linoleic SS decreased final live weight (554 vs. 592 kg; P = 0.01), carcass weight (329 vs. 346 kg; P = 0.06), and dressing percent (58.5 vs. 59.4%; P = 0.04). Steers fed high-linoleic SS plus barley had less (P < 0.05) backfat than those fed other SS diets. No adverse effects of SS on liver abscess incidence or meat quality were detected. Although they provide protein and fiber useful in formulating finishing diets for cattle, and did improve performance in Exp. 1, no benefit from substituting SS for grain and roughage was detected in Exp. 2. Because of unexplained inconsistencies between the two experiments, additional research is warranted to confirm the feeding value of SS in diets for feedlot cattle. 相似文献
993.
Freeze-dried ileal effluent (1% wt/vol) from cannulated pigs fed rice-based diets with the inclusion of either animal protein (CON), animal protein plus potato starch (PS), animal protein plus sugar beet pulp (SBP), or animal protein plus wheat bran (WB) was incubated anaerobically at pH 6.0 in fermenters containing 5% (wt/vol) fecal slurry comprising mineral salts medium and 50 g/L of fresh feces from pigs fed the same diets as the cannulated pigs. Samples were collected from the fermenters at 0, 2, 4, 12, 24, and 48 h during in vitro fermentation for measuring nonstarch polysaccharides (NSP), starch, and short-chain fatty acids (SCFA). Results showed that the major SCFA produced were acetate, propionate, and butyrate. The inclusion of soluble dietary fiber (diet SBP) caused the highest concentrations of acetate, propionate, butyrate, and total SCFA, whereas the increase in the production of propionate resulting from the addition of insoluble dietary fiber (diet WB) only occurred at the initial stages during 48 h in vitro fermentation. At all sampling occasions (except for 4 h), the levels of butyrate were increased (P < 0.01) by resistant starch compared with fiber sources, showing that a higher level of butyrate can be achieved through microbial fermentation by potato starch. Lowered (P < 0.05) butyrate concentrations were observed with diet WB during in vitro fermentation. With the inclusion of fiber sources, the energy originating from SCFA was similar to that from NSP disappearance, whereas the values were lower (P < 0.05) from NSP disappearance than for SCFA generated without fiber sources supplemented. We conclude that more substrate is available in ileal effluent with the addition of soluble dietary fiber, and an increased level of butyrate could be achieved through microbial fermentation by resistant starch. 相似文献
994.
The effect of KLP-602 (active substance: lysozyme dimer) on the replication of two animal viruses: the TK900 strain of Aujeszky's disease virus and the Roakin strain of the Newcastle disease virus were investigated. The maximal tolerable dose of the drug was determined for two cell cultures (CECC and GMK) and the effect of the medicine on the titre range of infectious viruses and their adsorption was assayed. The direct impact of KLP-602 on the viral strains used was also determined. And finally the replication dynamics of viruses in the presence of KLP-602 preparation was estimated. KLP-602 showed no direct effect on either the viruses applied in the study or their adsorption. The drug, introduced into the culture 24 hours before its infection, did not affect the replication of the pseudorabies virus, but decreased the titre of the Newcastle disease virus. KLP-602 introduced simultaneously with the infection considerably lowered the final titres of both viruses. The medicine had the greatest inhibitory effect on the replication dynamics of both types of viruses in the CECC and of the pseudorabies virus in the GMK culture upon the maximal tolerable concentrations of drug and low infectious doses of viruses applied. 相似文献
995.
ABSTRACT Spatiotemporal changes in the population structure of Botryosphaeria dothidea, causal agent of panicle and shoot blight of pistachio, were analyzed by using microsatellite-primed polymerase chain reaction (MPPCR), partial sequences of the RNA polymerase II (RPB2) gene, and vegetative compatibility groups (VCGs). We examined 390 isolates, 378 recovered from pistachio in seven counties of California from 1990 to 2001 and 12 recovered from peach, apple, and sycamore in Georgia, North Carolina, South Carolina, Illinois, and Pennsylvania. Six microsatellite primers generated 116 polymorphic bands. Based on MP-PCR data, we observed very high (>98%) levels of genetic identity among populations of B. dothidea collected from the commercial pistachio orchards in California. The near identity of these populations was supported by VCGs and partial sequences of the RBP2 gene. These findings suggest that populations of B. dothidea from commercial pistachio orchards are spatially and temporally stable, at least in the past 5 years. 相似文献
996.
In the apical glandular region of the adult Proteocephalus torulosus (Batsch, 1786), two types of eccrine gland cells are present. The first type of unicellular gland produces large electron-dense granules of various sizes. The second type contains small electron-dense granules. Most cells form glands with large granules; glands with small granules are infrequent. The secretion of both types of gland cells is concentrated in the apical parts of the cyton and in the ducts opening to the exterior. On the scolex of P. torulosus, there are regional structural differences of the microthrix border. The apical glandular region bears filamentous microtriches only. On the remaining frontal part, surrounding the glandular region, there are blade-like and filamentous microtriches. The lateral parts of the scolex and suckers bear blade-like microtriches. Possible functions of both types of gland cells and different parts of the scolex microthrix border are discussed. The unique structure of the frontal part of the scolex of P. torulosus and its differences from Proteocephalus macrocephalus, P. longicollis and P. percae correlate well with the putative basal phylogenetic position of P. torulosus among European species of Proteocephalus. 相似文献
997.
Five types of presumed ciliate sensory receptors were detected in the forebody papillae of the adult fish trematode, Crepidostomum metoecus (Braun, 1900). The cilia are short and submerged in a tegumental pit. The apical bulb part of all types of receptors observed is supported by a dense collar and connected to the tegument basal plasma membrane by a circular septate junction. In sensory receptors types I and III no rootlet is present; the bulbs of sensory receptors types III and IV contain an electron-dense formation. 相似文献
998.
999.
Terzić S Jemersić L Lojkić M Sver L Valpotić I Orsolić N Humski A Cvetnić Z 《Acta veterinaria Hungarica》2004,52(2):151-161
Total white blood cell (WBC) counts and percentages of CD4a+, CD8a+, CD5a+, CD45RA+, CD45RC+, wCD21+ and SWC3a+ cells in the peripheral blood of pigs were analysed in this study. Blood samples were collected before and on days 4, 10, 21 and 28 after vaccination. Group 1 pigs were vaccinated with a subunit E2 vaccine (gp E2 32 microg/dose), and Group 2 received a subunit vaccine combined with an attenuated ORF virus strain D1701 10(6.45) TCID50/dose. Control pigs received a placebo. The total WBC count and percentage of particular cell types were within the normal range in vaccinated and control pigs. Although the mechanism of attenuated ORF virus activity is not clear, changes were observed in CD4a+, CD5a+, CD8a+, CD45RA+ and CD45RC+ cells in pigs that received the combination of a subunit vaccine and ORF virus. However, the percentage of wCD21+ and SWC3a+ did not differ significantly from that recorded in pigs given only the subunit vaccine. At days 4 and 10 the number of pigs positive to E2 antibodies was higher in the group that received the subunit vaccine and ORF virus than in pigs vaccinated with the subunit vaccine only. A higher percentage of memory cells (CD45RC+) as well as Th and Tc lymphocytes in pigs that received the ORF virus and the subunit vaccine could be ascribed to a nonspecific influence of the ORF virus on the development (through cognate interactions between T and B cells) and the duration (presumed according to the finding of the clonal expression of memory cells) of humoral immunity (assessed by a higher number of seropositive pigs in this group). This seems likely since the proportion of these cells was found to be lower in the pigs that received E2 vaccine only. 相似文献
1000.
Differentiation of Actinobacillus pleuropneumoniae by PCR-REA based on sequence variability of the apxIVA gene and by ribotyping 总被引:1,自引:0,他引:1
Jaglic Z Svastova P Rychlik I Nedbalcova K Kucerova Z Pavlik I Bartos M 《Veterinary microbiology》2004,103(1-2):63-69
During the period of 2001-2003, a total of 591 Actinobacillus pleuropneumoniae field isolates from the Czech Republic were serotyped with a high occurrence of cross-reactions. The cross-reactions were observed in 416 isolates. Most frequently, in 401 isolates (67.9%), cross-reactions with antisera specific for serotypes 9, 11, and/or 1 were observed. Two additional molecular methods, ribotyping and restriction analysis of PCR amplified apxIVA gene (PCR-REA), were therefore used for detailed characterisation of A. pleuropneumoniae. In this subsequent analysis, reference strains representing serotypes 1-12 and 25 field isolates showing the most frequent serotype cross-reactions were examined. PCR-REA enabled all reference strains to be distinguished except for the strains of serotypes 9 and 11. Ribotyping distinguished all reference strains except two pairs of serotypes: 3 versus 6, and 9 versus 11, respectively. Field isolates with serotype cross-reactivity 9, 11, and/or 1 could not be differentiated by either of these methods. 相似文献