全文获取类型
收费全文 | 36077篇 |
免费 | 2209篇 |
国内免费 | 5003篇 |
专业分类
43289篇 |
出版年
2024年 | 77篇 |
2023年 | 591篇 |
2022年 | 845篇 |
2021年 | 1111篇 |
2020年 | 980篇 |
2019年 | 1282篇 |
2018年 | 1038篇 |
2017年 | 949篇 |
2016年 | 990篇 |
2015年 | 1239篇 |
2014年 | 1714篇 |
2013年 | 2292篇 |
2012年 | 1640篇 |
2011年 | 1691篇 |
2010年 | 1458篇 |
2009年 | 1780篇 |
2008年 | 1944篇 |
2007年 | 2111篇 |
2006年 | 2155篇 |
2005年 | 1993篇 |
2004年 | 1817篇 |
2003年 | 1706篇 |
2002年 | 1573篇 |
2001年 | 1275篇 |
2000年 | 1058篇 |
1999年 | 998篇 |
1998年 | 887篇 |
1997年 | 768篇 |
1996年 | 754篇 |
1995年 | 713篇 |
1994年 | 692篇 |
1993年 | 516篇 |
1992年 | 436篇 |
1991年 | 363篇 |
1990年 | 306篇 |
1989年 | 223篇 |
1988年 | 240篇 |
1987年 | 211篇 |
1986年 | 162篇 |
1985年 | 152篇 |
1984年 | 156篇 |
1983年 | 73篇 |
1982年 | 86篇 |
1981年 | 54篇 |
1980年 | 58篇 |
1979年 | 41篇 |
1978年 | 23篇 |
1977年 | 17篇 |
1976年 | 23篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Shiro Tabata Takeshi Ide Yasuyoshi Umemura Kenzo Torri 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,797(2):231-238
α-Glucosidases or maltases (EC 3.2.1.20) were purified to electrophoretic homogeneity from a respective strain of Sacchromyces cerevisiae which carries a single MAL gene, either MALα, MALβ or MALγ, using gluconate-Sepharose affinity chromography and isoelectrofocusing. Of these maltases, two types of maltase were obtained from the MALγ strain, the pI values of which were 5.6 and 5.9. From the MALα and MALβ strain was obtained only one type of maltase with the pI at 5.6 which was identical to one of the maltases from the MALγ strain. These four maltases possessed the same properties, except for pI. They were monomers with molecular weights of between 66 000 and 67 000. With regard to the substrate specificity, they hydrolyzed maltose and sucrose exclusively but not α-methulglucoside nor maltooligosaccharide. They did not differ in immunological properties. 相似文献
32.
33.
34.
L. Marklund M. Johansson U. Gustafsson L. Andersson A. K. Winterö M. Fredholm P. D. Thomsen 《Animal genetics》1993,24(5):333-338
Restriction fragment length polymorphisms (RFLPs) were described for the porcine loci for β-glucosidase (GBA) and the β-polypeptide 1 of the Na+, K+-transporting ATPase (ATP1B1). Linkage analyses using a three-generation pedigree provided evidence for the assignment of ATP1B1, GBA and two microsatellite loci (S0001 and S0067) to a previously described linkage group comprising the loci for blood group L (EAL) and an anonymous microsatellite (S0097). The linear order of the six markers was determined with confidence by multipoint analyses and the length of the linkage group was estimated at 88 CM. This linkage group was assigned to pig chromosome 4 on the basis of a previous physical localization of the ATP1B1 gene. In situ hybridization data for S0001 presented in this study were consistent with a localization on chromosome 4 and suggested a regional localization to 4pl2-pl3. The present study reveals conflicting data concerning the genetic localization of the K88 loci controlling the expression of the receptors for the E. coli pilus antigens. One group has reported data suggesting a loose linkage between K88 and EAL, now mapped to chromosome 4, whereas two other groups have found linkage between K88 and the transferrin locus (TF), mapped to chromosome 13 by in situ hybridization. 相似文献
35.
目的对virB2基因编码蛋白进行分析,为virB2基因及其编码蛋白功能提供实验依据。方法利用多种生物学软件以及网站对VirB2蛋白的结构和功能进行分析预测,VirB2蛋白序列通过基因推导获得并由生物公司合成,然后通过免疫动物实验制备鼠抗VirB2蛋白多克隆抗体,同时设计进行VirB2蛋白细胞毒试验(MTT法)。结果virB2基因编码蛋白属于疏水性蛋白,为鞭毛样结构,有较强的细胞毒作用。结论对VirB2蛋白的结构和功能进行了分析预测,证明VirB2蛋白在H.pylori相关的致病性特别是引起胃黏膜炎症方面起到一定的作用,能够为研究H.pylori致病机制提供帮助。 相似文献
36.
《Bioscience, biotechnology, and biochemistry》2013,77(5):1190-1198
The Rhynchosciara americana C3-22 gene is located in an amplified domain and is developmentally expressed. The aim of the present work was to identify intrinsically bent DNA sites in a segment containing the gene promoter and downstream sequence. The results indicated that this gene is flanked by intrinsically bent DNA sites. Three bent DNA sites (b?3, b?2, and b?1) were localized in the promoter, and one was localized downstream of the gene (b+1). These sites had helical parameters that confirmed the curved structure, as well as segments with left-handed superhelical writhe. In silico analysis of the promoters of four other insect genes, which encode secreted polypeptides, showed that they all had curved structures and similar helical parameters. Correlation with other results indicates that the detected intrinsically bent DNA sites that flank the C3-22 gene might be a consensus feature of the gene structure in the amplified domains. 相似文献
37.
Global species delimitation and phylogeography of the circumtropical ‘sexy shrimp’ Thor amboinensis reveals a cryptic species complex and secondary contact in the Indo‐West Pacific
下载免费PDF全文
![点击此处可从《Journal of Biogeography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
38.
39.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2758-2761
A group I intron that can be spliced in vivo and in vitro was identified in the flagellin gene of the thermophilic bacterium Geobacillus stearothermophilus. We also found one or two intervening sequences (IVS) of flagellin genes in five additional bacterial species. Furthermore, we report the presence of these sequences in two sites of a highly conserved region in the flagellin gene. 相似文献
40.