全文获取类型
收费全文 | 4942篇 |
免费 | 387篇 |
国内免费 | 257篇 |
专业分类
5586篇 |
出版年
2024年 | 9篇 |
2023年 | 61篇 |
2022年 | 141篇 |
2021年 | 232篇 |
2020年 | 159篇 |
2019年 | 191篇 |
2018年 | 186篇 |
2017年 | 116篇 |
2016年 | 214篇 |
2015年 | 308篇 |
2014年 | 327篇 |
2013年 | 352篇 |
2012年 | 432篇 |
2011年 | 408篇 |
2010年 | 234篇 |
2009年 | 229篇 |
2008年 | 275篇 |
2007年 | 246篇 |
2006年 | 202篇 |
2005年 | 155篇 |
2004年 | 150篇 |
2003年 | 147篇 |
2002年 | 118篇 |
2001年 | 89篇 |
2000年 | 81篇 |
1999年 | 64篇 |
1998年 | 28篇 |
1997年 | 41篇 |
1996年 | 51篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 45篇 |
1991年 | 29篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有5586条查询结果,搜索用时 15 毫秒
1.
Ai‐Xin Song Chen‐Jie Zhou Xiao Guan Kong‐Hung Sze Hong‐Yu Hu 《Protein science : a publication of the Protein Society》2010,19(5):1104-1109
DC‐UbP/UBTD2 is a ubiquitin (Ub) domain‐containing protein first identified from dendritic cells, and is implicated in ubiquitination pathway. The solution structure and backbone dynamics of the C‐terminal Ub‐like (UbL) domain were elucidated in our previous work. To further understand the biological function of DC‐UbP, we then solved the solution structure of the N‐terminal domain of DC‐UbP (DC‐UbP_N) and studied its Ub binding properties by NMR techniques. The results show that DC‐UbP_N holds a novel structural fold and acts as a Ub‐binding domain (UBD) but with low affinity. This implies that the DC‐UbP protein, composing of a combination of both UbL and UBD domains, might play an important role in regulating protein ubiquitination and delivery of ubiquitinated substrates in eukaryotic cells. 相似文献
2.
3.
Journal of Plant Growth Regulation - With the increasing popularity of urban landscaping, there is a greater need to address iron deficiency and chlorosis in Cinnamomum camphora. Beneficial... 相似文献
4.
Murine histocompatibility antigens were solubilized from the spleens and lungs of C57BL/6 (H-2b) animals with hypertonic salt (3 M KC1). Aggregate-free soluble antigens were incubated with nonadherent lymph node cells from BALB/c (H-2d) mice for 18 hr prior to their use as responder cells in the mixed-lymphocyte reaction (MLR). It was found that the generation of cytotoxic cells was suppressed while the proliferative response was not affected. The observed suppression was not due to a shift in the kinetics of the generation of cytotoxicity as determined throughout a 10-day culture period. The suppression was specific in that the response in MLR to unrelated H-2f stimulator cells and the subsequent generation of cytotoxic cells were unchanged. Using various H-2 recombinant strains as target cells in the assay of cell-mediated lympholysis, suppression of cytotoxicity was observed when the D end, but not the K end, was shared with the C57BL/6 strain from which the antigens were derived. 相似文献
5.
The aacA-aphD gentamicin and kanamycin resistance determinant of Tn4001 from Staphylococcus aureus: expression and nucleotide sequence analysis 总被引:15,自引:0,他引:15
The aacA-aphD aminoglycoside resistance determinant of the Staphylococcus aureus transposon Tn4001, which specifies resistance to gentamicin, tobramycin and kanamycin, has been cloned and shown to express these resistances in Escherichia coli. The determinant encoded a single protein with an apparent size of 59 kDa which specified both aminoglycoside acetyltransferase [AAC(6')] and aminoglycoside phosphotransferase [APH(2")] activities. Nucleotide sequence analysis of the determinant showed it to be capable of encoding a 479-amino-acid protein of 56.9 kDa. analysis of Tn1725 insertion mutants of the determinant indicated that resistance to tobramycin and kanamycin is due to the AAC activity specified by, approximately, the first 170 amino acids of the predicted protein sequence and is consistent with the gentamicin resistance, specified by the APH activity, being encoded within the C-terminal region of the protein. Comparison of the C-terminal end of the predicted amino acid sequence with the reported sequences of 13 APHs and a viomycin phosphotransferase revealed a region which is highly conserved among these phosphotransferases. 相似文献
6.
Y C Kong W M Keung T T Yip K M Ko S W Tsao M H Ng 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,87(2):221-226
1. An epidermal growth factor (EGF)-like activity was detected and partially purified from swiftlet's nest extract. 2. The partially purified EGF-like activity was able to (a) generate competitive binding curves parallel to the standard curves in radioreceptor assay and (b) stimulate thymidine incorporation in quiescent culture of 3T3 fibroblasts and the latter activity can be suppressed by mouse EGF antibody. 3. Partial characterization of the EGF-like activity in terms of pI, molecular weight and its behavior on gel filtration column suggest that it bears similar physical properties to the EGFs isolated from the mouse and the shrew. 相似文献
7.
L I Kong L J Swango B L Blagburn C M Hendrix D E Williams S D Worley 《Applied and environmental microbiology》1988,54(10):2580-2582
Free chlorine and a combined organic N-chloramine (3-chloro-4,4-dimethyl-2-oxazolidinone, compound 1) were compared for efficacy as disinfectants against an admixture of cysts of Giardia lamblia and Giardia canis in water solution under a variety of test conditions; variables were pH, temperature, and water quality. In general, compound 1 was found to reduce the giardial excystation in the solutions at lower concentration or shorter contact time at a given total chlorine concentration than did free chlorine. 相似文献
8.
Status of metacercarial infections of Paragonimus westermani was observed in freshwater crabs, which were purchased at 3 markets in its peak season of 1990. All of 85 crabs were Eriocheir japonicus. No other species of Eriocheir were found. When crushed muscle and viscera was examined individually, the infection rate was 11.8%; and mean number of metacercariae was 2.1 per infected crab. Unless adequately cooked, freshwater crabs are still potential sources of human paragonimiasis. 相似文献
9.
The nature of 2 component proteins in crude saline extract of adult Paragonimus westermani was investigated. By immunoaffinity chromatography using monoclonal antibodies (MAb) as ligands, the proteins were purified from the crude extract. Band 1 protein in disc-polyacrylamide gel electrophoresis (PAGE) was purified by PFCK-136 MAb. The protein, known to have molecular mass of 440 kDa, was composed of 23, 46 and 92 kDa subunits when observed by reducing SDS-PAGE and SDS-PAGE/immunoblot. This protein was originated from eggs of the worm as revealed by immunohistochemical staining with PFCK-136 Mab. Another affinity purified protein utilizing PFCK-44 MAb was the band 4 protein of 17 kDa in disc-PAGE. This was a monomer protein in reducing SDS-PAGE and SDS-PAGE/immunoblot. The protein was produced at intestinal epithelium of the worm. 相似文献
10.
The effect of the length of direct repeats and the presence of palindromes on deletion between directly repeated DNA sequences in bacteriophage T7. 总被引:13,自引:0,他引:13
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The frequency of genetic deletion between directly repeated DNA sequences in bacteriophage T7 was measured as a function of the length of the direct repeat. The non-essential ligase gene (gene 1.3) of bacteriophage T7 was interrupted with pieces of synthetic DNA bracketed by direct repeats of various lengths. Deletion of these 76 bp long inserts was too low to be measured when the direct repeats were less than 6 bp long. However, the frequency of deletion of inserts with longer direct repeats increased exponentially as the length of the repeats increased from 8 to 20 bp. When inverted repeats (palindromes) were designed in the midst of the insert there was essentially no increase in deletion frequency between 10 bp direct repeats. But, the same palindromic sequences increased the deletion frequency between 5 bp direct repeats by at least two orders of magnitude. Thus, in this system homology at the endpoints is a more important determinant of deletion frequency than is the presence of palindromes between the direct repeats. 相似文献