全文获取类型
收费全文 | 48381篇 |
免费 | 3196篇 |
国内免费 | 4871篇 |
专业分类
林业 | 3770篇 |
农学 | 3519篇 |
基础科学 | 2768篇 |
5384篇 | |
综合类 | 22354篇 |
农作物 | 3518篇 |
水产渔业 | 2320篇 |
畜牧兽医 | 7330篇 |
园艺 | 3246篇 |
植物保护 | 2239篇 |
出版年
2024年 | 296篇 |
2023年 | 902篇 |
2022年 | 1981篇 |
2021年 | 2128篇 |
2020年 | 1966篇 |
2019年 | 1929篇 |
2018年 | 1382篇 |
2017年 | 2276篇 |
2016年 | 1645篇 |
2015年 | 2383篇 |
2014年 | 2507篇 |
2013年 | 3038篇 |
2012年 | 4161篇 |
2011年 | 4231篇 |
2010年 | 3923篇 |
2009年 | 3450篇 |
2008年 | 3481篇 |
2007年 | 3223篇 |
2006年 | 2726篇 |
2005年 | 2189篇 |
2004年 | 1442篇 |
2003年 | 915篇 |
2002年 | 1095篇 |
2001年 | 995篇 |
2000年 | 843篇 |
1999年 | 402篇 |
1998年 | 172篇 |
1997年 | 145篇 |
1996年 | 87篇 |
1995年 | 97篇 |
1994年 | 103篇 |
1993年 | 67篇 |
1992年 | 60篇 |
1991年 | 54篇 |
1990年 | 29篇 |
1989年 | 22篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1963年 | 1篇 |
1962年 | 7篇 |
1957年 | 1篇 |
1956年 | 6篇 |
1955年 | 3篇 |
1932年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
镧素对镰刀菌Fusarium solani及其致病酶的影响 总被引:2,自引:0,他引:2
采用琼脂平板生长速率法及液体培养基培养测定了La对镰刀菌Fusarium solani的抑制作用和毒力,并测定了其对病菌胞外的果胶酶、蛋白酶和纤维素酶等几种致病酶活性的影响。结果表明,随着La2O3浓度升高,对病菌菌丝生长的抑制作用增强,对病菌的EC50和EC95分别为278.2和552.0 mg/L;在一定浓度范围内,La提高了单位量菌丝所产生3种致病酶的活性,但由于菌丝生长受到抑制,除蛋白酶外,病菌胞外致病酶果胶酶和纤维素酶的总量或总活性受到了抑制,降低了病菌的致病力。 相似文献
103.
104.
105.
106.
107.
108.
AIM:To investigate the effect of the heat shock response on the reperfusion arrhythmias(RAs) and the possible mechanism involved. METHODS:Fifty-five Sprague Dawley rats were randomly divided into 2 groups: the heat shock group (group H,n=29) and the control group (group C,n=26). The rats in group H were preconditioned with heat shock 24 hours before, and that in group C were not. The hearts of 16 rats in group H and 16 in group C were exercised and mounted on a non-circulating Langendorff perfusion apparatus and perfused retrogradely with modified K-H buffer and mimic ischemia/reperfusion was applied. Additionally, conventional intracellular microelectrode techniques were used for recording such electrophysiological parameters as resting potential(RP), action potential amplitude(APA), over shot(OS), maximum depolarization velocity(Vmax) of the hearts of other 13 rats in group H and 10 in group C. RESULTS:①Prior heat stress significantly decreased reperfusion arrhythmia. ②The amount of CK release in the effluent in group H was much less than that in group C. ③Myocardial HSP70 content was elevated significantly in group H. ④Heat stress significantly increased myocardial anti-oxydases activity and decreased lipid peroxydative products. Additionally, heat stress significantly reduced the Vmax of action potential. It indicated that rapid Na+ channel of papillary muscles may be inhibited by heat shock. The degree of change of Vmax after ischemia in H group was significantly less than that in group C. And the time of reperfusoin with Tyrode's solution till the action potential appeared as large as that before perfusion with mimic ischemic solution is shorter in group H than in group C. CONCLUSION:Heat shock pretreatment markedly reduces ischemia/reperfusion-induced injury of heart and ventricular arrhythmias in rats and this effect may be associated with the inhibition of rapid Na+ channel of papillary muscles by heat shock and the increase in myocardial HSP70 and anti-oxydase activity. 相似文献
109.
AIM:To investigate the effect of metallothionein(MT) on proliferation of rat vascular smooth muscle cells (VSMCs) stimulated by homocysteine and its mechanism. METHODS:VSMCs proliferation was measured by [3-H]-TdR incorporation, mitogen-activated protein kinase(MAPK)activity were determined by immunoprecipitation method, the intracellular contents of MT and malondialdehyde (MDA)were assayed by -hemoglobin saturation method and TBA reaction, respectively, and lactate dehydrogenase (LDH) leakage was measured by NADH oxidation. RESULTS:Hcy(10-6-10-4 mmol/L) stimulated [3-H]-TdR incorporation by the VSMCs in a concentration-dependent manner. Compared with control, [3-H]-TdR incorporation in VSMCs treated with 0.1 mmol/L Hcy was increased by 4.2 fold (P<0.01). Meanwhile, Hcy enhanced MAPK activity, MDA formation and LDH release (P<0.01)in a concentration-dependent manner. Treatment of VSMCs with MT alone did not change above parameters, compared with control. However, MT (10-6-10-4 mol/L)attenuated significantly Hcy-stimulated proliferation of VSMCs (P<0.01)in a concentration-dependent manner. And MT inhibited obviously Hcy-induced activation of MAPK activity, MDA formation and LDH release. Preincubation of VSMCs with 0.5 mmol/L ZnCl2 for 6 h induced an increase cellular MT content by 5.7-fold (P<0.01). The MT-overexpressed VSMCs resisted Hcy-stimulating action on MAPK activity, MDA formation and LDH leakage (P<0.01). CONCLUSION:These results show that MT has an inhibitory effect on Hcy-induced VSMCs proliferation, and that MT could inhibit Hcy-stimulated MAPK activity and lipid peroxidation. 相似文献
110.
AIM:To study the effect of environment of liver regeneration on the proliferation of rat fetal hepatocytes after intrasplenical transplantation. METHODS:Fetal hepatocytes isolated from 3-week SD rat fetuses bred were transplanted into the spleens of liver regeneration model rats with 70% partial hepatectomy. The cell cycle of the hepatocytes in the remnants liver was analyzed by flow cytometer and the density dimensions of the donor fetal hepatocytes in spleen were measured by image analysis system 7 and 30 days post-transplantation, respectively. RESULTS:Compared with the control group, the proportions of S and G2 /M cells in the remnants liver were obviously decreased (P<0.05), but the density dimensions of the donor fetal hepatocytes in spleen increased significantly (P<0.05) in rats with hepatectomy 7 days post-transplantation. CONCLUSION:The environment of liver regeneration is propitious to the proliferation of fetal hepatocytes after transplantation into spleen. 相似文献