全文获取类型
收费全文 | 142631篇 |
免费 | 19714篇 |
国内免费 | 31849篇 |
专业分类
林业 | 16799篇 |
农学 | 18966篇 |
基础科学 | 14015篇 |
41010篇 | |
综合类 | 51876篇 |
农作物 | 9994篇 |
水产渔业 | 8662篇 |
畜牧兽医 | 18180篇 |
园艺 | 4528篇 |
植物保护 | 10164篇 |
出版年
2024年 | 1111篇 |
2023年 | 1766篇 |
2022年 | 3314篇 |
2021年 | 4103篇 |
2020年 | 5353篇 |
2019年 | 8381篇 |
2018年 | 7414篇 |
2017年 | 8828篇 |
2016年 | 9248篇 |
2015年 | 9869篇 |
2014年 | 9226篇 |
2013年 | 10389篇 |
2012年 | 10828篇 |
2011年 | 10464篇 |
2010年 | 9269篇 |
2009年 | 8561篇 |
2008年 | 7538篇 |
2007年 | 7622篇 |
2006年 | 7196篇 |
2005年 | 6350篇 |
2004年 | 4197篇 |
2003年 | 3754篇 |
2002年 | 3244篇 |
2001年 | 3021篇 |
2000年 | 3009篇 |
1999年 | 3289篇 |
1998年 | 3106篇 |
1997年 | 2766篇 |
1996年 | 2471篇 |
1995年 | 2493篇 |
1994年 | 2302篇 |
1993年 | 2012篇 |
1992年 | 1829篇 |
1991年 | 1548篇 |
1990年 | 1250篇 |
1989年 | 1153篇 |
1988年 | 951篇 |
1987年 | 642篇 |
1986年 | 543篇 |
1985年 | 280篇 |
1984年 | 260篇 |
1983年 | 234篇 |
1982年 | 229篇 |
1981年 | 265篇 |
1980年 | 211篇 |
1979年 | 165篇 |
1978年 | 140篇 |
1975年 | 112篇 |
1965年 | 142篇 |
1964年 | 148篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
G Plassiart J F Guelfi J P Ganiere B Wang G Andre-Fontaine M Wyers 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1992,39(6):443-453
Twenty rabbits were inoculated with a suspension of Viral Hemorrhagic Disease virus. Hemostatic functions were assessed every sixth hour from 6 to 60 hours post-inoculation. Tissue samples obtained at the same intervals allowed the study of the development of lesions throughout the experiment. Biological signs of Disseminated Intravascular Coagulation (DIC) were detected on and after 30 h post-inoculation and consisted of prolonged One Stage Prothrombin Time and Activated Partial Thrombin Time, the decrease of factors V, VII, and X and high levels of soluble fibrin monomer complexes and D-dimers. A reduction of thrombocyte numbers, heterophils and lymphocytes was associated. The close association of DIC and necrotizing hepatitis lesions suggested the hepatic lesions to be the most important DIC triggering factor. Other mechanisms are discussed. 相似文献
13.
ABSTRACT: The reproductive traits and the monthly larval abundance of the mantis shrimp Oratosquilla oratoria were investigated in Tokyo Bay, Japan, in 2002. The goal of the study was to elucidate the cause of changes in the monthly pattern of larval abundance from the 1980s to the 1990s as these changes relate to variation in the stock size of the adult shrimp. Oogenesis was divided into 10 stages by histological observation. The developmental stage of oocytes in an individual's ovary was synchronous, suggesting that almost all the oocytes in an ovary are spawned at the same time. The size at first maturity was estimated to be 7 ≤ body length ( BL ) < 8 cm. Fecundity was expressed as a function of BL , ranging from 19 300 eggs for 8 cm BL to 92 100 eggs for 14 cm BL . Small female shrimps (<10 cm BL ) spawned around August. Most large female shrimps (≥10 cm BL ) spawned around May, and some large female shrimps also spawned until September. Although most large female shrimps spawned in spring, the larval abundance was low before July and high from August onwards. The results suggest that a substantial decrease in the stock size of large individuals causes the low larval abundance before July. 相似文献
14.
CERES-Maize (Vl. 0) predicted no grain yield when 100% defoliation occurred during vegetative growth. This result conflicted with field observations where 100% defoliation early in the vegetative stage did not materially reduce grain yield. CERES-Maize was modified to realistically predict yields when defoliation greater than 50% occurred during vegetative growth by taking into account stem (stem proper and sheath) photosynthesis and translocation of dry matter from the stem to the developing leaves. With these modifications, predictions from CERES-Maize were in good agreement with field measurements when defoliation occurred both early and later in the vegetative stage. This modified version of CERES-Maize can be the basis of a decision support system for defoliating pests of corn where yields can be evaluated under different management strategies and climate scenarios. 相似文献
15.
C. P. Verschueren P. J. Selman J. J. M. de Vijlder J. A. Mol 《Domestic animal endocrinology》1991,8(4):509-519
Canine thyroglobulin (cTg) has been isolated and purified. It has similar electrophoretic patterns as Tg from other mammalian species. The main fraction had a MW of 660,000, whereas also fractions of a MW of approximately 1,300,000 (dimer) and 330,000 (subunit) were present. The iodine content was 0.8 to 1.0 % (w/w). cTg did not cross-react with antibodies against human Tg to a degree that would allow the use of a radioimmunoassay for human Tg for the determination of cTg in serum or plasma. Therefore a polyclonal antiserum was raised against cTg and a homologous radioimmunoassay was developed, which was sensitive (0.4 μg/l) and specific (cross-reactivity in cTg assay of human Tg, goat Tg, T4, T3, and DIT < 0.01 %).
Plasma Tg levels in normal dogs of both sexes and aged 3–15 years amounted to 192 ± 73 μg/l (mean ± SD, n=30). There was no relation between plasma Tg and T4 levels. 相似文献
16.
17.
18.
研究结果表明,由性状果实最大周长,果实体积,门茄显蕾期,单株产量等性状构成的选择指数较好;进一步进行遗传相关分析结果认为,应用选择指数时应注意果实体积这个性状,单株产量是一个重要的辅助性状,门茄显蕾期是一个限制性因子。应用选择指数对品种评价结果认为,早熟性较好的品种有:天津早茄、西安绿茄、二民、七叶茄、白线茄和汉中荷包。 相似文献
19.
本文应用动力学研究方法比较了具有不同耐盐性的3组共6个水稻基因型对NaCl吸收和运转的差异,结果表明,在外部低NaCl浓度(0.1mmolL~(-1)时,水稻对Na~+的吸收为被动吸收,耐盐基因型对Na~+的吸收速率显著低于盐敏感基因型;对Cl~-的吸收为主动吸收,不同耐盐性基因型吸收Cl~-的动力学参数(V_(?)、K_(?))差异不显著,在外部高NaCl浓度(50mmolL~(-1))时,耐盐基因型对Na~+和cl~-的吸收速率均低于对应的盐敏感基因型。耐盐基因型水稻的Na~+、cl-从根部向地上部的运转率低于对应的盐敏感基因型,这种差异在高盐浓度时更为明显。表明了耐盐基因型水稻地上部对NaCl的排斥作用是吸收控制和运转控制共同作用的结果,使地上部Na~+、Cl-含量相对降低而显出较高的耐盐性。 相似文献
20.