全文获取类型
收费全文 | 91555篇 |
免费 | 4329篇 |
国内免费 | 45篇 |
专业分类
林业 | 5142篇 |
农学 | 3448篇 |
基础科学 | 587篇 |
12996篇 | |
综合类 | 10778篇 |
农作物 | 3669篇 |
水产渔业 | 4512篇 |
畜牧兽医 | 47568篇 |
园艺 | 1610篇 |
植物保护 | 5619篇 |
出版年
2019年 | 790篇 |
2018年 | 2392篇 |
2017年 | 2542篇 |
2016年 | 1880篇 |
2015年 | 1160篇 |
2014年 | 1464篇 |
2013年 | 3737篇 |
2012年 | 2845篇 |
2011年 | 3963篇 |
2010年 | 3038篇 |
2009年 | 2784篇 |
2008年 | 3562篇 |
2007年 | 3730篇 |
2006年 | 2654篇 |
2005年 | 2429篇 |
2004年 | 2294篇 |
2003年 | 2291篇 |
2002年 | 2059篇 |
2001年 | 2920篇 |
2000年 | 2781篇 |
1999年 | 2176篇 |
1998年 | 878篇 |
1997年 | 813篇 |
1996年 | 763篇 |
1995年 | 900篇 |
1994年 | 761篇 |
1992年 | 1640篇 |
1991年 | 1732篇 |
1990年 | 1806篇 |
1989年 | 1700篇 |
1988年 | 1559篇 |
1987年 | 1535篇 |
1986年 | 1482篇 |
1985年 | 1394篇 |
1984年 | 1207篇 |
1983年 | 976篇 |
1979年 | 1206篇 |
1978年 | 907篇 |
1977年 | 821篇 |
1976年 | 929篇 |
1975年 | 940篇 |
1974年 | 1099篇 |
1973年 | 1033篇 |
1972年 | 1026篇 |
1971年 | 919篇 |
1970年 | 927篇 |
1969年 | 929篇 |
1968年 | 886篇 |
1967年 | 904篇 |
1966年 | 829篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
131.
Immunological control of hematophagous arthropod vectors: utilization of novel antigens 总被引:3,自引:1,他引:2
S K Wikel 《Veterinary parasitology》1988,29(2-3):235-264
Immunological control of ixodid ticks requires development of a vaccine that stimulates an effective anti-tick response. However, it is important to avoid induction of intense host skin reactivity to tick feeding. Salivary-gland-derived molecules are introduced into the host during ixodid engorgement; therefore, use of these moieties might not be an optimal immunization strategy. Antigens not normally involved in acquired resistance can be used to induce anti-tick immunity. These "novel" antigens, obtained from tick gut absorptive surface, are not introduced into the host during tick feeding, but are exposed to host-immune effector elements in the blood meal, resulting in ixodid rejection, prevention of ova production and death. Anti-tick immunity is induced with microgram quantities of this ixodid gut antigen preparation. Sera obtained from immunized animals were used to identify antibody-reactive components of the resistance-inducing extract. Tick gut absorptive surface antigen glycoconjugates were identified by lectin blotting, using a series of probes with different carbohydrate specificities. The lectins, peanut and wheat germ agglutinin, and immunized host antibodies bound extract components with similar molecular weights. Solubilization and fractionization of tick gut proteins with the non-ionic detergent Triton X-114 is described. 相似文献
132.
Cribb AE Burgener DC Reimann KA 《The Canadian veterinary journal. La revue veterinaire canadienne》1988,29(8):654-657
Seven icteric dogs were determined to have bile duct obstruction secondary to chronic pancreatitis. All dogs had histories of intermittent vomiting and diarrhea. Alkaline phosphatase and alanine aminotransferase activities and total bilirubin concentrations were markedly elevated. Diagnosis was based on exploratory laparotomy and histological examination. Each dog had a 3 to 10 cm mass in the body of the pancreas and obstruction of the common bile duct. Three dogs treated with pancreatectomy, gastrojejunostomy, and cholecystojejunostomy died within five weeks. Three dogs treated with conservative surgical procedures were alive at 8, 16, and 26 months postoperatively. One dog was euthanized because of suspected neoplasia. Hepatic enzyme activity and bilirubin levels decreased markedly in the surviving dogs. Histological examination of the pancreatic masses indicated chronic pancreatitis. Hepatic biopsies revealed evidence of cholestasis. Chronic pancreatitis should be included in the differential diagnoses of icterus, bile duct obstruction, and masses in the pancreas. 相似文献
133.
134.
135.
136.
137.
138.
Six shipments totaling 3452 mummies of the blackmargined aphid,Monellia caryella (Fitch), parasitized withAphelinus perpallidus Gahan, were obtained by air freight during the years 1982-1985 from Texas A&M Research Center, El Paso, Texas. About two-thirds of the mummies did not yield parasites. A colony ofA. perpallidus was established in the laboratory. Under laboratory conditions the percentage of emerged parasites was higher than that in the imported mummies, and the parasite had very limited impact on the aphid population. Field releases of the parasite were made but no establishment ofA. perpallidus was observed through the years. 相似文献
139.
The interaction in water of neutral hydrocarbon and fluorocarbon surfaces, prepared by Langmuir-Blodgett deposition of surfactant monolayers, has been investigated. The attraction between these hydrophobic surfaces can be measured at separations of 70 to 90 nanometers and thus is of considerably greater range than previously found. Spontaneous cavitation occurred as soon as the fluorocarbon surfaces were brought into contact but occurred between the hydrocarbon surfaces only after separation from contact. The very long range forces measured are a consequence of the metastability of water films between macroscopic hydrophobic surfaces. Thus the hydrophobic interaction between macroscopic surfaces may not be related to water structure in the same way that the hydrophobic effect between nonpolar molecules is related to water structure. 相似文献
140.