全文获取类型
收费全文 | 4476篇 |
免费 | 239篇 |
国内免费 | 269篇 |
专业分类
4984篇 |
出版年
2023年 | 67篇 |
2022年 | 74篇 |
2021年 | 104篇 |
2020年 | 125篇 |
2019年 | 134篇 |
2018年 | 90篇 |
2017年 | 106篇 |
2016年 | 113篇 |
2015年 | 127篇 |
2014年 | 216篇 |
2013年 | 299篇 |
2012年 | 177篇 |
2011年 | 224篇 |
2010年 | 153篇 |
2009年 | 168篇 |
2008年 | 222篇 |
2007年 | 222篇 |
2006年 | 201篇 |
2005年 | 178篇 |
2004年 | 176篇 |
2003年 | 154篇 |
2002年 | 129篇 |
2001年 | 124篇 |
2000年 | 114篇 |
1999年 | 121篇 |
1998年 | 76篇 |
1997年 | 70篇 |
1996年 | 73篇 |
1995年 | 80篇 |
1994年 | 74篇 |
1993年 | 63篇 |
1992年 | 54篇 |
1991年 | 51篇 |
1990年 | 39篇 |
1989年 | 44篇 |
1988年 | 42篇 |
1987年 | 43篇 |
1986年 | 50篇 |
1985年 | 51篇 |
1984年 | 31篇 |
1983年 | 33篇 |
1982年 | 42篇 |
1981年 | 25篇 |
1980年 | 42篇 |
1979年 | 31篇 |
1978年 | 34篇 |
1977年 | 20篇 |
1976年 | 18篇 |
1975年 | 24篇 |
1972年 | 16篇 |
排序方式: 共有4984条查询结果,搜索用时 15 毫秒
11.
12.
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
13.
D. BERNER 《Journal of evolutionary biology》2009,22(12):2563-2565
Testing for an association between the leading vectors of multivariate trait (co)variation within populations (the ‘line of least resistance’) and among populations is an important tool for exploring variational bias in evolution. In a recent study of stickleback fish populations, a bootstrap‐based test was introduced that takes into account estimation error in both vectors and hence improves the previously available bootstrap method. Because this test was implemented incorrectly, however, I here describe the correct test protocol and provide a reanalysis of the original data set. The application of this new test protocol should improve future investigations of evolution along lines of least resistance and other vector comparisons. 相似文献
14.
Tests for change-points with epidemic alternatives 总被引:1,自引:0,他引:1
15.
16.
17.
J. N. Sachan Basudeo Singh 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(4):571-574
Summary Components of generation means were partitioned for days to flower initiation and maturity in three crosses of Indian mustard (Brassica juncea (L.) Czern and Coss) cultivars. A linked digenics model was adequate for flowering in cross II and maturity in Cross I. All three types of digenic interactions among the linked pairs of genes, additive X additive (i), additive X dominance (j) and dominance X dominance (1), contributed significantly in the inheritance of flowering in cross II and maturity in cross I. A complete association among the genes of greater effects in higher mean parent was detected for flowering in cross II and maturity in Cross I. Duplicate epistasis was evident for flowering in Crosses I and II and maturity in Crosses I and III.Inadequacy of all the fitted models for days to flowering in Cross III and maturity in Cross II indicated the presence of higher order interactions.Part of PhD (plant breeding) Thesis, submitted by senior author to GBPUAT, Pantnagar (Nainital) U.P., India (unpublished). Research paper No. 4262 相似文献
18.
G. Wersuhn K. Kirsch R. Gienapp 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(4):480-482
Summary Culture-derived plants and cell cultures of potato (Solanum tuberosum L.) respond to the application of the herbicides SYS 67 ME (MCPA) and OMNIDEL (Na-2,2-dichloropropionate) in a comparable fashion. By gradually increasing the herbicide concentration, cell lines were developed which tolerated 50 mg/l of ME or 300 mg/l of OMNIDEL. Any further increase in concentration resulted in the death of all cell cultures. From cell cultures that had been able to grow on media supplemented with 30 mg/l of ME, regenerate plants were obtained that were also tolerant to this concentration. This new trait was retained even after repeated vegetative propagation of the plants. 相似文献
19.
Hiroshi Iwasaki Toshikazu Shiba Atsuo Nakata Hideo Shinagawa 《Molecular & general genetics : MGG》1989,219(1-2):328-331
Summary The ruv operon of Escherichia coli consists of two genes, orfl1 and ruv, which encode 22 and 37 kilodalton proteins, respectively, and are regulated by the SOS system. Although the distal gene, ruv, is known to be involved in DNA repair, the function of orf1 has not been studied. To examine whether orf1 is also involved in DNA repair, we constructed a strain with a deletion of the entire ruv operon. The strain was sensitive to UV even after introduction of low copy number plasmids carrying either orf1 or ruv, but UV resistance was restored by introduction of a plasmid carrying both orfl and ruv. These results suggest that orf1 as well as ruv is involved in DNA repair. Therefore, orf1 and ruv should be renamed ruvA and ruvB, respectively. 相似文献
20.
虫生真菌双生座壳孢的研究 总被引:1,自引:0,他引:1
双生座壳孢(Aschersonia duplex Berk.)系日本卷毛蚧的病原真菌。此菌在人工培养基和自然基物上生长好,并能产生大量分生孢子。对 C 源中的蔗糖、葡萄糖、甘露醇、山梨糖;N 源中的蛋白胨,天冬素、L-酪氨酸、KNO_3利用好。生长适温22—26℃。病原流行季节相对湿度在80%以上。田间接种,对寄主致病性强,有应用潜力。 相似文献