全文获取类型
收费全文 | 44768篇 |
免费 | 2510篇 |
国内免费 | 4691篇 |
专业分类
林业 | 3607篇 |
农学 | 4061篇 |
基础科学 | 2745篇 |
5255篇 | |
综合类 | 19400篇 |
农作物 | 3229篇 |
水产渔业 | 1842篇 |
畜牧兽医 | 6853篇 |
园艺 | 2807篇 |
植物保护 | 2170篇 |
出版年
2024年 | 284篇 |
2023年 | 747篇 |
2022年 | 1825篇 |
2021年 | 1887篇 |
2020年 | 1852篇 |
2019年 | 1708篇 |
2018年 | 1271篇 |
2017年 | 1905篇 |
2016年 | 1479篇 |
2015年 | 2156篇 |
2014年 | 2170篇 |
2013年 | 2594篇 |
2012年 | 3495篇 |
2011年 | 3624篇 |
2010年 | 3365篇 |
2009年 | 3032篇 |
2008年 | 3077篇 |
2007年 | 2909篇 |
2006年 | 2478篇 |
2005年 | 2051篇 |
2004年 | 1254篇 |
2003年 | 986篇 |
2002年 | 1061篇 |
2001年 | 995篇 |
2000年 | 852篇 |
1999年 | 597篇 |
1998年 | 335篇 |
1997年 | 304篇 |
1996年 | 237篇 |
1995年 | 233篇 |
1994年 | 230篇 |
1993年 | 195篇 |
1992年 | 193篇 |
1991年 | 128篇 |
1990年 | 102篇 |
1989年 | 108篇 |
1988年 | 79篇 |
1987年 | 52篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1966年 | 3篇 |
1962年 | 8篇 |
1956年 | 20篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
番木瓜环斑病毒株系的分子生物学方法鉴定 总被引:6,自引:1,他引:6
以PRSV株系特异性引物对PRSV的PRSV126(PRSV日本分离物)、Ys、Vb和Sm等株系进行RT-PCR方法鉴定,引物PR21/PR22能把Ys从Vb和Sm中鉴定出来,PR300/PR301则能把Vb从Ys、Sm和PRSV126中鉴定出来;用限制性内切酶Hae Ⅱ、Sau3A I和Hinf I对PRSV的PRSV126、Ys、Vb和Sm等株系进行单酶切RT-PCR-RFLP分析,Hinf I能把PRSV126与Ys、Vb和Sm鉴别开来,Sau3A I能把Ys与Vb和Sm鉴别开来,Hae Ⅱ则能把Ys与PRSV126、Vb和Sm鉴别开来;以P1/P2为引物,对Vb、Ys和Sm株系进行RT-PCR-RFLP-SSCP分析,结果能一次把三者较好地区别开来。 相似文献
112.
以稀释倒平板法从0型菌086和IV型菌967-4和9620中分离到59个单细胞系;在12个近等基因系品种上,086和其单细胞系表现为弱毒力,2个IV型菌及其单细胞系能克服抗病基因Xa-1、2、3、8、10、11、14的抗性,不能克服Xa-21、4、5、7、13的抗性;带主效抗病基因的品种Asominori、XM5、M41、XM6和丰锦能把3个母株的59个单细胞系区分为12种数量差异或质量差异的不同致病型;将此5品种与近等基因系配合,适合作为病菌致病基因变异频度监测的寄主;采用"段叶沙培,切口取菌胶"法分离病菌,在中国致病型鉴定品种上划分的致病型,是田间病菌群体毒力结构的表型反应。 相似文献
113.
114.
115.
116.
AIM: To examine the expression of human endostatin in E.coli, produce its fusion protein antibody and observe its biological activity. METHODS: Endostatin gene was amplified by polymerase chain reaction,recombined with plasmid vector pGEX-2T and induced expression with IPTG.The protein activity was tested by endothelial cell proliferation inhibitory assay.Inclusion body crudely purified was used to generate polyclonal antibody to detect its expression at mouse's liver and kidney etc. RESULTS: The protein expressed was 20kD after digestion by thrombin,it appeared the anti-angiogenesis activity and Western blotting indicated the expression of endostatin in liver and kidney of mouse. CONCLUSION: The successful expression of human endostatin and the preparation of polycolonal antibody indicated its potential application in anti-angiogenesis therapy and diagnosis tumors. 相似文献
117.
AIM: To study the electrophysiological characteristics of ion channels of stem cell derived cardiomyocytes(SCDC) of mouse. METHODS: Embryonic stem cells of D3 line(ES-D3) were cultured on the MEF feeder layer with BRL conditioned medium, and fetal mouse heart cells(FMHC)were cultured in vitro. Then ES-D3 cells were induced to differentiate into many kinds of cells. SCDC were harvested on day 12 after differentiation initiating and identified by electro-microscope and immunocytochemistry. SCDC and FMHC were prepared for the patch-clamp research. Sodium and calcium currents together were elicited and compared between SCDC and FMHC. RESULTS: The current characteristics of sodium and calcium channels of SCDC were very similar to FMHC. CONCLUSION: The functional expression of ion channels occurred during ES-D3 cells differentiation and the electrophysiological characteristics of sodium and calcium channels of SCDC are very similar to FMHC. 相似文献
118.
AIM: To investigate the changes of myocardium glycogen content and the relation ship between changes of the myocardial glycogen content and the myocardial function. METHODS: Male Wistar rats were placed in (hypoxia rats) and made to swim in (hypoxia swimming rats) a hypobaxic chamber simulating an altitude of 5 000 m above sea level. The content of myocardium glycogens was determined by colorimetry. RESULTS: The myocardium
glycogen content of rats significantly reduced along with the prolongation of hypoxic exposure and approached to control level in hypoxia swimming rats. The myocardial function of right ventricule was improved significantly compared with control group.CONCLUSION: Moderate exercise (swimming) is beneficial to hypoxic adaptation of rats under the condition of chronic hypoxia. 相似文献
119.
SHANG Zhan-ping HOU Zhong-chi ZHU Shi-gong JI Guo-yi WANG Jian-chun ZHAO Wan 《园艺学报》2002,18(12):1521-1523
AIM: To investigate the activity of interleukin-1β converting enzyme in transplanted intracerebral rat gliomas under angiotensin II-induced hypertension chemotherapy. METHODS: The brain tumor model was produced in Wistar rats by stereotaxic inoculation of C6 glioma cells (1×1012 /L). Tumor-bearing rats were treated with carmustine, teniposide and lisplatin (chemotherapy) during angiotensin II-induced hypertension. Then, the survival time of tumor-bearing rats, tumor blood flow, the concentration of drug, volume of gliomas and the activity of interleukin-1β converting enzyme in glioma were examined.RESULTS: The survival time of tumor-bearing rats was significantly longer in chemotherapy with angiotensin II-induced hypertension group than that of chemotherapy alone. In addition, regional tumor blood flow, the concentration of chemotherapeutic drug and the activity of interleukin -1β converting enzyme in transplanted rat gliomas were increased, while the volume of gliomas was decreased in hypertention chemotherapy group compared with chemotherapy alone. CONCLUSION: Chemotherapy with angiotensin II-induced hypertension has a enhancing effect on chemotherapy for improving the drug delivery to tumor tissue by a increased tumor blood flow and enhancing activity of interleukin -1β converting enzyme. 相似文献
120.