全文获取类型
收费全文 | 2559篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
林业 | 106篇 |
农学 | 29篇 |
基础科学 | 8篇 |
511篇 | |
综合类 | 536篇 |
农作物 | 124篇 |
水产渔业 | 35篇 |
畜牧兽医 | 1096篇 |
园艺 | 7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 | 15篇 |
2014年 | 22篇 |
2013年 | 5篇 |
2012年 | 351篇 |
2011年 | 369篇 |
2010年 | 63篇 |
2009年 | 32篇 |
2008年 | 243篇 |
2007年 | 226篇 |
2006年 | 192篇 |
2005年 | 149篇 |
2004年 | 157篇 |
2003年 | 143篇 |
2002年 | 142篇 |
2001年 | 88篇 |
2000年 | 88篇 |
1999年 | 54篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1973年 | 2篇 |
1970年 | 5篇 |
1963年 | 2篇 |
1950年 | 2篇 |
1945年 | 2篇 |
1940年 | 2篇 |
1897年 | 1篇 |
1896年 | 1篇 |
1886年 | 2篇 |
1885年 | 6篇 |
排序方式: 共有2568条查询结果,搜索用时 15 毫秒
121.
A flavivirus-associated disease of egg-laying ducks was observed in eastern China in 2010, and a novel mosquito-borne flavivirus, Tembusu virus (TMUV), was isolated (Cao et al., 2011). Following up on the earlier study, a virus similar to TMUV was isolated recently from ducklings and characterized. We report that (1) the recently isolated virus, TMUV ZJ-6, replicated in vertebrate cells (DF-1, BHK-21) as well as in mosquito cells (C6/36) and caused cytopathic effect (CPE) in the cell lines tested; (2) extracellular viral particles examined by electron microscopy were approximately 45 nm in diameter and enveloped; (3) the full-length genome of the virus was determined, showing that the TMUV ZJ-6 is more closely related to the Ntaya group of viruses than other members of the Flaviviridae based on the data of phylogenetic analyses. Most importantly, the disease of ducklings was reproducible after administration of plaque-purified virus by intracerebral (i.c.), subcutaneous (s.c.) or intranasal (i.n.) inoculation. This is the first report that TMUV infects not only egg-laying ducks but also 3-21 days-old ducklings. The findings extend our understanding of how the virus spreads and causes disease. 相似文献
122.
Metabolic changes induced by regular submaximal aerobic exercise in meat-type rabbits 总被引:3,自引:0,他引:3
Pannon White growing rabbits (a group of 8) were exposed to treadmill exercise (3-9 m/s, 1.2-1.6 km/day) twice a day for 4 weeks, while additional 8 animals, kept inactive, were assigned as the control group. Weekly, 12 hours after exercise, venous blood was taken for serum metabolite and enzyme activity measurements. Total serum protein, albumin and creatinine levels significantly increased during the second half of the training, as compared to the control group. Triacylglycerol levels in the exercised group as compared to controls, however, were higher only after the first and the fourth weeks of the experiment. Resting non-esterified fatty acid (NEFA) concentration of the trained rabbits was lower at the end of the trial. On the other hand, there were no significant differences, as compared to the respective controls, in serum urea, total and HDL cholesterol levels. At the end of the exercise alkaline phosphatase activity was higher and total lactate dehydrogenase activity was lower in the trained rabbits. Serum alanine aminotransferase, aspartate aminotransferase and gamma-glutamyl transpeptidase activities were not changed, while creatine kinase activity was slightly lower in the trained group. The serum cortisol concentration was not different in the trained and control rabbits. 相似文献
123.
基于Z指数的内蒙古通辽市干旱变化特点分析 《畜牧与饲料科学》2015,36(10):67-67
根据内蒙古通辽市10个气象站1971—2010年逐月的降水量数据,通过"Z指数"计算,划分为7个等级,统计干旱发生的频率。分析结果表明,通辽地区在近40年中,Z指数有较为明显的下降趋势,即该地区有向干旱发展的趋势。 相似文献
124.
Kaleczyc J Pidsudko Z Franke-Radowiecka A Sienkiewicz W Majewski M Lakomy M Timmermans JP 《Polish journal of veterinary sciences》2004,7(3):199-201
The present study investigated the chemical coding of neurons in the celiac-superior mesenteric ganglion complex supplying the normal (n=4) and inflamed (n=4) ileum (chemically-induced inflammation) in juvenile pigs using retrograde tracing combined with immunohistochemistry. Ileum-projecting neurons (IPN) were predominantly distributed in the left and right superior mesenteric pools of the ganglion. The majority of them were adrenergic (tyrosine hydroxylase-positive) and also contained neuropeptide Y, somatostatin or galanin. No clear-cut differences in the distribution and chemical coding of IPN were found between normal and inflamed pigs. However, in the inflamed group, the density of peptidergic, IPN-associated nerve fibres was higher than that found in the control group. 相似文献
125.
126.
Zheng Z Narita M Takahashi M Liu A Furukawa T Toba K Aizawa Y 《Comparative immunology, microbiology and infectious diseases》2004,27(2):93-103
In order to apply for reducing graft versus host disease in allogeneic stem cell transplantation, the study concerning the induction of specific T cell anergy was designed. Normal allogeneic lymphocytes, which were co-cultured with IL-10-treated immature dendritic cells in the first mixed leukocyte culture (MLC), were cultured with mature dendritic cells of the same origin as IL-10-treated immature dendritic cells in the second MLC. By co-culturing with IL-10-treated immature dendritic cells, the response of normal lymphocytes to mature dendritic cells cultured from the same individual as that of IL-10-treated dendritic cells was markedly reduced, compared with the lymphocytes cultured with non-treated dendritic cells or IL-10-treated dendritic cells from a third party individual. The present study demonstrated that antigen specific T cell anergy was generated by priming allogeneic lymphocytes with IL-10-treated immature dendritic cells. These data suggested the applicability of IL-10-treated recipient dendritic cells for the induction of recipient cell-specific donor T cell anergy in donor graft. 相似文献
127.
Collagen fragmentation in cranial cruciate ligament (CCL) explants and stifle synovial fluid was investigated in dogs with ruptured and intact CCL. Cathepsin K and tartrate-resistant acid phosphatase (TRAP) activities were determined in CCL explant supernatants. Formation of collagen fragments was determined in explant supernatants and stifle synovial fluid. Cathepsin K(+) and TRAP(+) cells were stained specifically in histological sections of CCL. Formation of telopeptide collagen fragments was increased in ruptured CCL explants and stifle synovial fluid from dogs with ruptured CCL. In ruptured CCL explants, release of collagen fragments was associated with extracellular release of TRAP and the presence of cathepsin K(+) cells within CCL tissue. Cathepsin K(+) and TRAP(+) cells were only seen in ruptured CCL. It was concluded that infiltration of the CCL with TRAP(+) cells in dogs with CCL rupture is associated with increased collagenolysis. It is hypothesized that recruitment and activation of TRAP(+) mononuclear cells within the synovium and CCL precipitates CCL rupture through upregulation of collagenolytic enzymes and collagen degradation. 相似文献
128.
Zankl A Ritzmann M Zöls S Heinritzi K 《DTW. Deutsche tier?rztliche Wochenschrift》2007,114(11):418-422
Objective of this study was to examine the efficacy of various local anaesthetics (Procaine Hydrochloride, Procaine Hydrochloride + Epinephrin, Lidocaine Hydrochloride) used in castration of four to six day old male piglets. Animals of the control groups (I-IV) were treated analogous to the castration groups (V-IX) but not castrated. In groups I and V 15 minutes prior to castration/fixation the piglets were fixed as for injection but not medicated. The injection volume was standardised to 0.5 ml per testes. Local anaesthetics were applicated intratesticularly in five groups and intrascrotarly in two groups. Blood samples were taken shortly before and one, four and 24 hours after castration/fixation. The serum cortisol level was analysed to determine pain induced neuroendocrine stress reaction. To proof the tissue tolerance creatinkinase-(CK) and aspartataminotransferase-(AST) concentration were analysed. One, seven and 14 days after castration the healing process were evaluated by a wound score. Groups I to IV did not show any increase of the serum cortisol level. Contrary one hour after castration the average cortisol concentration of castration groups (V-IX) rose significantly. Cortisol concentration of the medicated castration groups (VI-IX) showed a comparable or even higher cortisol level as the not medicated control group (V). Determination of CK and AST indicated no tissue damage of the application of the local anaesthetics. The administration of local anaesthetics prior to the castration did not have any effect on the wound healing process. The results of this study lead to the conclusion that injection of local anaesthetics show a good tissue tolerance but the call for reduction of the castration pain by presurgical injection of Procaine Hydrochloride or Lidocaine Hydrochloride is not justified. 相似文献
129.
管理科学是研究人类管理活动规律及其应用的一门科学。跨入新世纪,国际竞争日趋激烈。各国之间的竞争,说到底,是人才的竞争,教育是培养人才和增强民族创新能力的基础,学校对学生的教育,不仅传授给学生知识和技能,进行职业准备和职业训练,还教给学生社会价值观念、社会行为规范和社会理想,教他们如何做人,多层次、全方位地塑造学生个体的素质。因此,构建管理的规范化、制度化、科学化的大学生思想道德教育体系,对将大学生培养成有德之人、有为之才具有重要的理论意义和实践意义。1.科学构建大学生思想政治教育体系高校人才培养的基础 相似文献
130.
Mitochondria are important determinants of developmental competence for oocytes and embryos owing to their central role in cellular metabolism, yet mitochondrial activity and morphometry during early porcine development have not been quantified. In this study, we examined the membrane potential Δψ(m) and the surface density Sv(in,m) of the inner mitochondrial membrane in pig oocytes and pre-implantation embryos using fluorescent probes and confocal microscopy. Mitochondria and their cristae were also examined by transmission electron microscope. Δψ(m) was consistently low from immature oocytes up to morulae and increased significantly in the early blastocyst before decreasing at the expanded blastocyst stage. This stage-dependent pattern of Δψ(m) changes differs from that reported for other mammals. We also determined that Δψ(m) is lower in cultured when compared to non-cultured porcine early blastocysts. Sv(in,m) was higher in immature oocytes than mature oocytes and remained constant up to the 4- to 8-cell embryo stage. It increased significantly at morula and early blastocyst stages. No differences in Sv(in,m) were found between developmentally matched non-cultured and cultured embryos. These results indicate that the inner mitochondrial membrane potential and surface density change significantly during pre-implantation porcine development in relation to metabolic alterations of the embryo. It is possible that modification of Δψ(m) by manipulating culture conditions may improve the performance of embryos that develop in vitro. 相似文献