全文获取类型
收费全文 | 192052篇 |
免费 | 27036篇 |
国内免费 | 13139篇 |
专业分类
232227篇 |
出版年
2024年 | 343篇 |
2023年 | 2017篇 |
2022年 | 4618篇 |
2021年 | 8118篇 |
2020年 | 7027篇 |
2019年 | 9645篇 |
2018年 | 9472篇 |
2017年 | 8181篇 |
2016年 | 10176篇 |
2015年 | 13394篇 |
2014年 | 14890篇 |
2013年 | 16330篇 |
2012年 | 16751篇 |
2011年 | 15237篇 |
2010年 | 11338篇 |
2009年 | 9241篇 |
2008年 | 9746篇 |
2007年 | 8408篇 |
2006年 | 7397篇 |
2005年 | 6144篇 |
2004年 | 5249篇 |
2003年 | 4753篇 |
2002年 | 4170篇 |
2001年 | 3572篇 |
2000年 | 3369篇 |
1999年 | 3127篇 |
1998年 | 1834篇 |
1997年 | 1739篇 |
1996年 | 1691篇 |
1995年 | 1474篇 |
1994年 | 1390篇 |
1993年 | 1095篇 |
1992年 | 1592篇 |
1991年 | 1242篇 |
1990年 | 1038篇 |
1989年 | 944篇 |
1988年 | 750篇 |
1987年 | 677篇 |
1986年 | 582篇 |
1985年 | 563篇 |
1984年 | 359篇 |
1983年 | 349篇 |
1982年 | 207篇 |
1981年 | 201篇 |
1980年 | 140篇 |
1979年 | 220篇 |
1977年 | 151篇 |
1975年 | 166篇 |
1974年 | 168篇 |
1973年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
P. Cruz C. H. Mejia‐Ruiz R. Perez‐Enriquez A. M. Ibarra 《Molecular ecology resources》2002,2(3):239-241
Five polymorphic microsatellite loci were characterized for Penaeus (Litopenaeus) vannamei. Loci were isolated using a partial Sau3A1 genomic library by the sequencing of randomly selected clones and by a biotinylated (CT)10 and (GT)10 probes screening procedure. The last strategy resulted in the most useful data. About 40% of the clones showed a previously reported satellite/microsatellite (PVS1), reducing the chance of finding new microsatellite regions. Whereas two of the microsatellite loci with more than 10 alleles will be useful for mating analysis in a breeding program, the others might prove useful for population genetic studies. 相似文献
43.
We used a N-biotinylated peptide analog of the C-terminal domain of the tumor suppressor protein, p21cip1/waf1 to elucidate peptide/protein interacting partners. The C-terminal domain of p21cip1/waf1 protein spanning 141-160 amino acid residues is known to bind PCNA and this interaction is important in many biological processes including cell-cycle control. This C-terminal 20-mer efficiently extracts PCNA in the presence of a variety of N- or C-terminally attached affinity tags. Using difference silver stained 2D gels combined with in-gel tryptic digests, we identified the difference spots using MALDI-TOF mass spectrometry-based peptide mass fingerprinting followed by a database search using PROFOUND against NCBIs human nonredundant protein sequence data bank. Identified spots include the p48 subunit of chromatin assembly factor-1, the heat shock 70 protein analog BiP, calmodulin, nucleolin and a spot similar in size to dimeric PCNA. In contrast, microcapillary ion-trap LC-MS/MS analysis of a tryptic digest of entire affinity extracts derived from both control and experimental runs followed by database searches using SEQUEST confirmed the presence of most of the above proteins. This strategy also identified hnRNPA1, HPSP90alpha, HSP40 and T-complex protein 1, a protein similar to prothymosin, and a possible allelic variant of the p21cip1/waf1 protein. The use of N-biotinylated peptide derived from the C-terminal domain of p21cip1/waf1 protein in proteomic analysis exemplified here suggests that peptides obtained from intracellular functional screens could also potentially serve as efficient baits to discover new drug targets. 相似文献
44.
A cDNA library was prepared from poly(A) mRNA extracted from 9-day hamster-yolk-sac erythroid cells. Two clones containing inserts coding for embryonic beta-like z or y globin-chains were isolated. Their identity was confirmed by (a) translation of hybrid selected mRNAs and (b) nucleotide sequence analysis of the inserts and comparison to the embryonic beta-like globin genes of Balb/c mouse. Availability of sequences for embryonic and adult globin cDNAs will aid in investigations of the molecular mechanisms of the globin switch in hamster YSEC. 相似文献
45.
K W Culver W T Hsieh Y Huyen V Chen J Liu Y Khripine A Khorlin 《Nature biotechnology》1999,17(10):989-993
A sequence-specific genomic delivery system for the correction of chromosomal mutations was designed by incorporating two different binding domains into a single-stranded oligonucleotide. A repair domain (RD) contained the native sequence of the target region. A third strand-forming domain (TFD) was designed to form a triplex by Hoogsteen interactions. The design was based upon the premise that the RD will rapidly form a heteroduplex that is anchored synergistically by the TFD. Deoxyoligonucleotides were designed to form triplexes in the human adenosine deaminase (ADA) and p53 genes adjacent to known point mutations. Transfection of ADA-deficient human lymphocytes corrected the mutant sequence in 1-2% of cells. Neither the RD or TFD individually corrected the mutation. Transfection of p53 mutant human glioblastoma cells corrected the mutation and induced apoptosis in 7.5% of cells. 相似文献
46.
47.
48.
49.
K T Chen 《Acta cytologica》1984,28(2):133-135
Localized amyloidosis of the respiratory tract is seldom diagnosed in cytologic specimens. This report describes a case of the tracheobronchial form of amyloidosis in which diagnostic material was present in a cytologic specimen obtained during bronchoscopy. 相似文献
50.
Chien-Hung Liu Wen-Ming Chen Jo-Shu Chang 《World journal of microbiology & biotechnology》2007,23(5):633-640
Acidic lipase finds its commercial values in medical applications and bioremediation of food wastes. In this work, approaches
for rapid screening of lipase-producing bacteria were developed and the feasibility assessment of the screening methods was
performed. From food waste samples, the proposed screening procedures allowed isolation of sixteen pure bacterial strains
expressing higher lipase activity at acidic pH (pH 6.0) than at alkaline pH (pH 9.0). To enhance the accuracy of lipase activity
determination under acidic conditions, a novel assay procedure was also developed by deactivating lipase activity by microwave
treatment prior to back titration. This additional step could minimize interferences arising from residual lipase activity
during conventional direct back-titration methods in measuring lipase activity at acidic pH. Using the four strategies proposed
in this work, the best acidic-lipase-producing isolate was obtained by strategy C (SSC) and was identified as Aeromonas sp. C14, displaying an optimal lipase activity of 0.7 U/ml at an acidic pH of 6.0. 相似文献