全文获取类型
收费全文 | 9320篇 |
免费 | 705篇 |
国内免费 | 988篇 |
专业分类
11013篇 |
出版年
2024年 | 24篇 |
2023年 | 124篇 |
2022年 | 314篇 |
2021年 | 509篇 |
2020年 | 379篇 |
2019年 | 452篇 |
2018年 | 375篇 |
2017年 | 276篇 |
2016年 | 408篇 |
2015年 | 588篇 |
2014年 | 700篇 |
2013年 | 787篇 |
2012年 | 890篇 |
2011年 | 767篇 |
2010年 | 496篇 |
2009年 | 466篇 |
2008年 | 536篇 |
2007年 | 468篇 |
2006年 | 386篇 |
2005年 | 302篇 |
2004年 | 302篇 |
2003年 | 266篇 |
2002年 | 216篇 |
2001年 | 146篇 |
2000年 | 128篇 |
1999年 | 129篇 |
1998年 | 82篇 |
1997年 | 62篇 |
1996年 | 52篇 |
1995年 | 60篇 |
1994年 | 64篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 48篇 |
1990年 | 31篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
人体小卫星DNA探针的制备 总被引:3,自引:2,他引:1
根据人体小卫星DNA核心顺序,化学合成长23碱基寡核苷酸探针,筛选人体基因组文库,旨在获得能用作遗传分析探针的小卫星顺序。结果得到15个含小卫星的阳性重组子。随机取其一(C_(35.9))作探针,试做群体分析。所有个体均可检出多条杂交带。其中某些带具有多态性。在一定检测条件下,检出的DNA图谱在有限的个体内具有个体特异性。结果表明筛选文库得到的小卫星顺序可用于小卫星多态性的检测。其它小卫星探针的筛选和应用性研究正在进行。 相似文献
3.
4.
Yohichi Kamata Shunji Kozaki Takafumi Nagai Genji Sakaguchi 《FEMS microbiology letters》1985,26(3):305-309
Abstract Five monoclonal antibodies (MCA; E–8–2, 9–1, 11–2, 12–4, and 13–1) against Clostridium botulinum type E derivative toxin were prepared. Their ELISA titers were higher than or equivalent to that of conventional polyclonal antibody. Three of them (E-8–2, 12–4, and 13–1) possessed the neutralizing activity comparable to that of polyclonal antibody. The results of binding-competition experiments indicated that the monoclonal antibodies bound to different sites on the type E toxin molecule. Immunoblotting analyses demonstrated that E-8–2, 9–1, and 11–2 react to fragment I (heavy chain) of the toxin. By use of these monoclonal antibodies, it may be possible to scrutinize the structure-function relationship of botulinum toxins and cross reactions between type E and F toxins. 相似文献
5.
The pathogenesis of type E botulism is discussed as an aspect of the physicochemical and biological properties of 12S toxins (prototoxin and trypsin-activated 12S toxin) and the Ealpha and Ebeta components of each 12S toxin. A molecular weight of 350,000 was determined for each 12S toxin and 150,000 for Ealpha and Ebeta. Owing to the structure comprising the subunits Ealpha and Ebeta, 12S toxins are much more stable than Ealpha at low pH values and high temperatures. Such was also the case with type A 19S toxin and its alpha component. The Ealpha component alone accounts for the total toxicity of type E toxin. The toxic substance detected in the blood of the animals administered 12S toxins orally or parenterally was identified as Ealpha from the molecular size and the chromatographic pattern. Prototoxin escaping from detoxification in the stomach owing to the subunit structure may undergo dissociation in the intestine to release the Ealpha component. After absorption, the activated Ealpha appeared in the circulating blood without any further signs of dissociation or enzymatic digestion. 相似文献
6.
糙叶败酱挥发油镇静作用的研究 总被引:4,自引:1,他引:3
本文观察了败酱科植物糙叶败酱(Patrinia scabra Bunge)根和根茎中制得的挥发油的镇静作用,井与黄花败酱挥发油做了比较。结果表明,此油灌胃给予数组小鼠,剂量0.45ml/kg,显示如下的作用:[1]能显著延长由于腹腔注射戊巴比妥钠(50mg/kg)引起的小鼠睡眠时间,但其作用强度弱于黄花败酱挥发油。(2)一次灌胃给予小鼠大剂量10.46g/kg的糙叶败酱挥发油,连续观察10天,动物外观正常,无一死亡,体重增加与对照组相似。 相似文献
7.
8.
Biological Trace Element Research - The essential trace elements in 30 traditional Chinese medicines, (24 tonics and 6 nontonics) were determined by proton-induced X-ray emission. The... 相似文献
9.
本文设计一种由胶原和高分子聚合物组成的新型生物一人工复合血管。其研制过程是将包绕有聚酯网的硅胶棒埋入羊的皮下组织,再将形成的经聚酯网为支架的胶原管经醛化处理。作者通过肉眼和SEM观察提出了研制生物——人工复合血管的要点:聚酯网网孔要合适,其与硅胶棒的间隙要恰当,理化处理方法更要选择好。 相似文献
10.
We determined the nucleotide sequence of a DNA fragment which contains the replication region of pMSC262, a Mycobacterium scrofulaceum plasmid used to construct the Mycobacterium-Escherichia coli shuttle vector. The complete sequence of the fragment contained 2,504 bp with an overall G+C content of 69.8%. By deletion analysis, we found that the minimum length required for plasmid replication in M. bovis BCG was about 1.6 kb. Within this region, several open reading frames (ORFs) and a putative replication origin (ori) were identified by computer analysis. One of the ORFs, ORF2, which encodes a putative 28.9-kDa basic protein with characteristics of DNA-binding proteins, appeared to be involved in replication of the plasmid in BCG. By separation of ORF2 and the putative ori region, it was revealed that the relative locations of ORF2 and the putative ori region are likely important for replication in BCG. No DNA or amino acid homologies were found between this replication region and that of pAL5000, another mycobacterial plasmid used for vector plasmid construction. In addition, we found that this replicon did not lead to replication in E. coli and was compatible in BCG with pAL5000-derived vector plasmid pYUB75 (R. G. Barletta, D. D. Kim, S. B. Snapper, B. R. Bloom, and W. R. Jacobs, J., J. Gen. Microbiol. 138:23-30, 1992). 相似文献