全文获取类型
收费全文 | 9536篇 |
免费 | 691篇 |
国内免费 | 1054篇 |
专业分类
林业 | 776篇 |
农学 | 968篇 |
基础科学 | 771篇 |
1926篇 | |
综合类 | 3418篇 |
农作物 | 447篇 |
水产渔业 | 702篇 |
畜牧兽医 | 1196篇 |
园艺 | 209篇 |
植物保护 | 868篇 |
出版年
2024年 | 55篇 |
2023年 | 206篇 |
2022年 | 376篇 |
2021年 | 444篇 |
2020年 | 471篇 |
2019年 | 519篇 |
2018年 | 315篇 |
2017年 | 531篇 |
2016年 | 639篇 |
2015年 | 516篇 |
2014年 | 499篇 |
2013年 | 672篇 |
2012年 | 815篇 |
2011年 | 735篇 |
2010年 | 534篇 |
2009年 | 530篇 |
2008年 | 421篇 |
2007年 | 478篇 |
2006年 | 381篇 |
2005年 | 306篇 |
2004年 | 257篇 |
2003年 | 190篇 |
2002年 | 189篇 |
2001年 | 152篇 |
2000年 | 134篇 |
1999年 | 120篇 |
1998年 | 98篇 |
1997年 | 86篇 |
1996年 | 97篇 |
1995年 | 73篇 |
1994年 | 67篇 |
1993年 | 76篇 |
1992年 | 54篇 |
1991年 | 46篇 |
1990年 | 41篇 |
1989年 | 49篇 |
1988年 | 24篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Stine Jacobsen 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2023,52(Z1):8-18
Serum amyloid A (SAA) has become an indispensable part of the management of equine patients in general practice and specialized hospital settings. Although several proteins possess acute phase properties in horses, the usefulness of SAA exceeds that of other acute phase proteins. This is due to the highly desirable kinetics of the equine SAA response. SAA concentrations exhibit a rapid and pronounced increase in response to inflammation and a rapid decline after the resolution of inflammation. This facilitates the detection of inflammatory disease and real-time monitoring of inflammatory activity. SAA may be used in all stages of patient management: (1) before diagnosis (to rule in/rule out inflammatory disease), (2) at the time of diagnosis (to assess the severity of inflammation and assist in prognostication), and (3) after diagnosis (to monitor changes in inflammatory activity in response to therapy, with relapse of disease, or with infectious/inflammatory complications). By assessing other acute phase reactants in addition to SAA, clinicians can succinctly stage inflammation. White blood cell counts and serum iron concentration change within hours of an inflammatory insult, SAA within a day, and fibrinogen within 2–3 days; the interrelationship of these markers thus indicates the duration and activity of the inflammatory condition. Much research on the equine SAA response and clinical use has been conducted in the last decade. This is the prerequisite for the evidence-based use of this analyte. However, still today, most published studies involve a fairly low number of horses. To obtain solid evidence for use of SAA, future studies should be designed with larger sample sizes. 相似文献
102.
103.
104.
Novel surface treatment technique by silane film is developing for metallic anti corrosion and coat improvement. The key points, hydrolysis and condensation, for the stability of the Silane agent(SA) solution is investigated, and the effective factors of stability for silane agent solution and the relative rule are discussed. It is found that stability of SA solution is related to the temperature, pH, solvents, SA concentration and additive by studying the state of the solution and the conductivity-time curve of SA solution. Meanwhile, controlling factors and improving methods for SA stability are proposed to guide the practical application of metallic surface anti-corrosion treatment by SA. 相似文献
105.
A Coptis Chinesis is the dry rhizoma of ranunculaceous Coptis Chinesis Franch or Coptis deltoidea C. 7. Cheng et Hisao, or Coptis teeta Wall. It is the traditional Chinese herb, which is used in the contagious diseases. In recent years, its new pharmacological actions have been reported, which are antitumour, hypoglycemic response, immunoloregulation, improving the functions of cardiovascular. The important pharmacological functions of Coptis Chinesis are hypoglycemic response, improving the functions of cardiovascular, antitumour. With the deeply researching of Coptis Chinesis pharmacology, and the continuous founding of pharmacological mechanism, new preparation will be widely applied in the clinic. 相似文献
106.
An equivalent model for hollowing-center grounding device is proposed, the hollowing-center grounding device resistance is calculated with the surface charge simulation method and the computer programme is programmed based on this model. The accuracy of the model and method is validated by experimentation. 相似文献
107.
A theoretical model is developed for the dropwise condensation heat transfer on the horizontal circular surface with radial gradient surface energy based on the heat transfer model of individual condensate drop and the size distribution model of condensate drop on homogeneous condensation surface.The effect of variation of contact angle on the gradient surface on condensation heat transfer and condensate drop size distribution is taken account of in this model.The theoretical calculation method was obtained to predict the dropwise condensation heat transfer coefficient on the horizontal circular surface with radial gradient surface energy under various wall subcooled temperature,contact angle profile on wall surface,and working fluid.The effects of surface energy gradient,wall subcooled temperature,and thermophysical properties of condensate on the condensation heat transfer are discussed respectively.The calculation results show that the condensation heat transfer coefficient increases slightly with the increase of wall subcooled temperature.As latent heat and surface tension increasing,the condensation heat transfer coefficient increases.A larger surface energy gradient induces a larger condensation heat transfer coefficient. 相似文献
108.
Critical information system in Interact is in face of increasingly security problems. More attention has been focused on the survivability of information system, which is the capability of system to continue its mission even in the presence of damage to the system. The authors first introduce the definition of survivability. According to four function properties of survivability, which are Resistance, Recognition, Recovery, and Adaption, the authors design a model of survivable system structure and then explain survivability requirement, survivability strategy in this model. Additionally, they provide possible technical solutions for the survivability of systems, categorized by different aspects of our survivability strategy. 相似文献
109.
The cavity induced by top-blow gas jets impinging on the bath surface is one of most important parameters, which has overwhelming influence on the rate of slag formation and metallurgical performance. Water model experiments are conducted through a 1/10 scaled-down top-blown convertor. Effects of lance height and gas flow rate on penetration behavior are studied, and also the influence mechanism of liquid surface tension on penetration depth is addressed based on the experiments and theory analysis. An energy utilization index (EUI) is defined to reflect how much the impinging kinetic energy of gas jets are transferred into bath for formation of cavity, and an improved model is proposed to predict penetration depth of jets. The results show that penetration depth increases with lowering lance height and increasing gas flow rate, and impact diameter increases with increasing lance height, but is little affected by gas flow rate. Influence of liquid surface tension on penetration depth is enhanced with increasing surface tension and penetration depth. The EUI increases with increasing lance height, and a function relationship of it with lance height is obtained based on the experiments. 相似文献
110.
According to existent problems on design and application of the cylindrical cam mechanism with the slide roller-follower, the one correct concept about profile design and pressure angle is presented. Based on this concept, the theoretical profile,practical profile,meshing surface equations and pressure angle formula of the cam mechanism are built up by using opp.rotation analysis and offset surface principle. This method is very simple and clear, and avoids the abstract analysing process in meshing principle. The mathematic models built by this paper can be used to design,manufacture and check this type of cam mechanism correctly, and also create conditions to make deeply meshing property analysis of this mechanism. 相似文献