全文获取类型
收费全文 | 8817篇 |
免费 | 500篇 |
国内免费 | 1035篇 |
专业分类
林业 | 918篇 |
农学 | 1011篇 |
基础科学 | 731篇 |
1534篇 | |
综合类 | 2688篇 |
农作物 | 473篇 |
水产渔业 | 397篇 |
畜牧兽医 | 1701篇 |
园艺 | 342篇 |
植物保护 | 557篇 |
出版年
2024年 | 44篇 |
2023年 | 124篇 |
2022年 | 300篇 |
2021年 | 453篇 |
2020年 | 412篇 |
2019年 | 358篇 |
2018年 | 275篇 |
2017年 | 400篇 |
2016年 | 326篇 |
2015年 | 429篇 |
2014年 | 441篇 |
2013年 | 556篇 |
2012年 | 664篇 |
2011年 | 652篇 |
2010年 | 610篇 |
2009年 | 545篇 |
2008年 | 505篇 |
2007年 | 478篇 |
2006年 | 417篇 |
2005年 | 363篇 |
2004年 | 192篇 |
2003年 | 203篇 |
2002年 | 173篇 |
2001年 | 157篇 |
2000年 | 170篇 |
1999年 | 153篇 |
1998年 | 119篇 |
1997年 | 129篇 |
1996年 | 95篇 |
1995年 | 90篇 |
1994年 | 94篇 |
1993年 | 62篇 |
1992年 | 82篇 |
1991年 | 60篇 |
1990年 | 48篇 |
1989年 | 49篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 13篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1962年 | 2篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
白背飞虱危害对水稻产量结构的影响 总被引:4,自引:0,他引:4
白背飞虱[Sogatellafurcifera(Horvath)]是太湖稻区的主要害虫之一,近年来,随着耕作制度的变化及水稻品种的变更,白背飞虱跃升为太湖稻区水稻生长前期的优势种群。目前国内的研究多侧重于褐飞虱的危害及其防治,关于白背飞虱危害对水稻产量的影响,国内鲜见报道[1,2]。为了探明白背飞虱在水稻不同生育期危害时,不同虫口密度与产量的关系,作者于1997年进行了白背飞虱危害对水稻产量结构影响的研究。1 材料与方法供试水稻品种为S015。试验田共分28小区,小区面积20m2。选取均匀饱满的… 相似文献
32.
33.
34.
35.
36.
37.
38.
Cardiomyopathy developed in mice deficient for α-kinase 3 (ALPK3), a nuclear kinase previously implicated in the differentiation of cardiomyocytes. Alpk3 (-/-) mice were produced according to normal Mendelian ratios and appeared normal except for a nonprogressive cardiomyopathy that had features of both hypertrophic and dilated forms of cardiomyopathy. Cardiac hypertrophy in Alpk3 (-/-) mice was characterized by increased thickness of both left and right ventricular (LV and RV) walls and by markedly increased heart weight and increased heart weight/body weight and heart weight/tibia length ratios. Magnetic resonance imaging studies confirmed the increased thickness in both septal and LV free walls at end-diastole, although there was no significant change in LV wall thickness at end-systole. Myocardial hypertrophy was the predominant feature in Alpk3 (-/-) mice, but several changes more typically associated with dilated cardiomyopathy included a marked increase in end-diastolic and end-systolic LV volume, as well as reduced cardiac output, stroke volume, and ejection fractions, suggesting LV chamber dilation. Magnetic resonance imaging showed a 50% reduction in both septal and free wall LV contractility in Alpk3 (-/-) mice. Interstitial fibrosis and inflammation were notably absent in Alpk3 (-/-) mice; however, light and electron microscopy revealed altered cardiomyocyte architecture, characterized by reduced numbers of abnormal intercalated discs being associated with mild disarray of myofibrils. These lesions could account for the impaired contractility of the myofibrillar apparatus and contribute to the pathogenesis of cardiomyopathy in Alpk3 (-/-) mice. 相似文献
39.
40.
Pedretti E Passeri B Amadori M Isola P Di Pede P Telera A Vescovini R Quintavalla F Pistello M 《Veterinary immunology and immunopathology》2006,109(3-4):245-254
Feline immunodeficiency virus sustains an AIDS-like syndrome in cats, which is considered a relevant model for human AIDS. Under precise enrolment requirements, 30 naturally infected cats showing overt disease were included in a trial of low-dose, oral human interferon-alpha treatment. Twenty-four of them received 10 IU/Kg of human interferon-alpha and 6 placebo only on a daily basis under veterinary supervision. The low-dose human interferon-alpha treatment significantly prolonged the survival of virus-infected cats (p<0.01) and brought to a rapid improvement of disease conditions in the infected hosts. Amelioration of clinical conditions was neither correlated with plasma viremia, nor with proviral load in leukocytes. A good survival of CD4+ T cells and a slow increase of CD8+ T cells were also observed in human interferon-alpha-treated cats. Interestingly, the improvement of the total leukocyte counts showed a much stronger correlation with the recovery from serious opportunistic infections. As shown in other models of low-dose interferon-alpha treatment, there was a rapid regression of overt immunopathological conditions in virus-infected cats. This hints at a major role of interferon-alpha in the control circuits of inflammatory cytokines, which was probably the very foundation of the improved clinical score and survival despite the unabated persistence of virus and virus-infected cells. 相似文献