全文获取类型
收费全文 | 3080篇 |
免费 | 274篇 |
国内免费 | 307篇 |
出版年
2024年 | 8篇 |
2023年 | 50篇 |
2022年 | 87篇 |
2021年 | 134篇 |
2020年 | 107篇 |
2019年 | 132篇 |
2018年 | 115篇 |
2017年 | 72篇 |
2016年 | 123篇 |
2015年 | 186篇 |
2014年 | 216篇 |
2013年 | 189篇 |
2012年 | 241篇 |
2011年 | 277篇 |
2010年 | 157篇 |
2009年 | 149篇 |
2008年 | 179篇 |
2007年 | 180篇 |
2006年 | 162篇 |
2005年 | 136篇 |
2004年 | 107篇 |
2003年 | 105篇 |
2002年 | 84篇 |
2001年 | 40篇 |
2000年 | 59篇 |
1999年 | 61篇 |
1998年 | 23篇 |
1997年 | 31篇 |
1996年 | 35篇 |
1995年 | 22篇 |
1994年 | 22篇 |
1993年 | 11篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有3661条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
A Kuroiwa K Matsubara T Nagase N Nomura J K Seong A Ishikawa R V Anunciado K Tanaka T Yamagata J S Masangkay V B Dang T Namikawa Y Matsuda 《The Journal of heredity》2001,92(3):282-287
The direct R-banding fluorescence in situ hybridization (FISH) method was used to map 18S-28S ribosomal RNA genes and 10 human cDNA clones on the chromosomes of the musk shrew (Suncus murinus). The chromosomal locations of 18S-28S ribosomal RNA genes were examined in the five laboratory lines and wild animals captured in the Philippines and Vietnam, and the genes were found on chromosomes 5, 6, 9, and 13 with geographic variation. The comparative mapping of 10 cDNA clones of human chromosome 1 demonstrated that human chromosome 1 consisted of at least three segments homologous to Suncus chromosomes (chromosomes 7, 10, and 14). This approach with the direct R-banding FISH method is useful for constructing comparative maps between human and insectivore species and for explicating the process of chromosomal rearrangements during the evolution of mammals. 相似文献
5.
Ion-Exchange Chromatography Separates Activities Synthesizing and Degrading Fructose 2,6-Bisphosphate from C3 and C4 Leaves but Not from Rat Liver 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fructose-6-phosphate,2-kinase and fructose-2,6-bisphosphatase were separated on the basis of charge from leaves of C3 (spinach, lettuce, and pea) and C4 (sorghum and amaranthus) plants but not from rat liver—a tissue known to contain a bifunctional enzyme with both activities. [2-32P]Fructose 2,6-bisphosphate binding experiments also suggest that the major forms of these activities reside on different proteins in leaves. 相似文献
6.
We have identified the domain of the human c-myc protein (c-Myc) produced in Escherichia coli that is responsible for the ability of the protein to bind sequence-nonspecific DNA. Using analysis of binding of DNA by proteins transferred to nitrocellulose, DNA-cellulose chromatography, and a nitrocellulose filter binding assay, we examined the binding properties of c-Myc peptides generated by cyanogen bromide cleavage, of mutant c-Myc, and of proteins that fuse portions of c-Myc to staphylococcal protein A. The results of these analyses indicated that c-Myc amino acids 265 to 318 were responsible for DNA binding and that other regions of the protein (including a highly conserved basic region and a region containing the leucine zipper motif) were not required. Some mutant c-Mycs that did not bind DNA maintained rat embryo cell-cotransforming activity, which indicated that the c-Myc property of in vitro DNA binding was not essential for this activity. These mutants, however, were unable to transform established rat fibroblasts (Rat-1a cells) that were susceptible to transformation by wild-type c-Myc, although this lack of activity may not have been due to their inability to bind DNA. 相似文献
7.
Contractile responses to adrenergic nerve stimulation are enhanced with removal of endothelium in rat caudal artery 总被引:6,自引:0,他引:6
Removal of the endothelium from isolated perfused rat caudal arteries produced a two fold increase in the contractile response to transmural nerve stimulation. Pretreatment with 6-hydroxydopamine eliminated the contractile response to adrenergic nerve stimulation but failed to uncover any vasodilatory effect of electrical stimulation, either directly on smooth muscle or via non-adrenergic nerves. Endothelial removal also produced two and four fold enhancement of the contractile responses to the selective alpha 1- and alpha 2-adrenoceptor agonists methoxamine and B-HT 920. However, pKB values for prazosin and yohimbine versus both agonists indicate that both methoxamine and B-HT 920 are acting primarily at alpha 1-adrenoceptors in this tissue. These results provide evidence that endothelial factors released either at basal levels or by the stimulation of agonists play a significant physiological role in modifying the contractile responses of blood vessels. 相似文献
8.
马齿苋叶片PEPCase由四个相同的亚基组成,亚基分子量为83kD。远紫外CD光谱分析表明,此酶含有36.6%α—螺旋结构。马齿苋叶片PEPCase可被G6P激活,但不能被Gly、Ser激活。G6P可防止酶的尿素变性和枯草杆菌蛋白酶的作用。这种保护效应与G6P诱导的酶构象变化有关。 从酶对低温、高温及尿素的反应来看,马齿苋叶片PEPCase的稳定性高于高粱叶片PEP—Case,两者的免疫特性和电泳特性亦不同。 相似文献
9.
An efficient method for generating embryonic mosaics using a yeast site-specific recombinase (FLP), under the control of a heat shock promoter, is described. FLP-recombinase can promote mitotic exchange between homologous chromosomes that contain FRT (FLP Recombination Target) sequences. To demonstrate the efficiency of FLP-recombinase to generate embryonic mosaics, clones of the recessive and cell autonomous mutation armadillo (arm), detected by their ability to differentiate ectopic denticles in the naked cuticle of each abdominal segment, have been induced. We have analyzed the parameters of FLP-recombinase induced embryonic mitotic recombination and have demonstrated that clones can be efficiently induced during the postblastoderm mitotic divisions. We discuss applications of this technique for the analyses of the roles of various mutations during embryonic patterning. 相似文献
10.