全文获取类型
收费全文 | 2512篇 |
免费 | 178篇 |
国内免费 | 121篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 58篇 |
2021年 | 128篇 |
2020年 | 94篇 |
2019年 | 93篇 |
2018年 | 85篇 |
2017年 | 73篇 |
2016年 | 117篇 |
2015年 | 151篇 |
2014年 | 165篇 |
2013年 | 209篇 |
2012年 | 213篇 |
2011年 | 196篇 |
2010年 | 123篇 |
2009年 | 96篇 |
2008年 | 128篇 |
2007年 | 117篇 |
2006年 | 97篇 |
2005年 | 79篇 |
2004年 | 74篇 |
2003年 | 65篇 |
2002年 | 65篇 |
2001年 | 40篇 |
2000年 | 37篇 |
1999年 | 31篇 |
1998年 | 13篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有2811条查询结果,搜索用时 937 毫秒
161.
Liu L Mo J Rodriguez-Belmonte EM Lee MY 《The Journal of biological chemistry》2000,275(25):18739-18744
A 12-kDa and two 25-kDa polypeptides were isolated with highly purified calf thymus DNA polymerase delta by conventional chromatography. A 16-mer peptide sequence was obtained from the 12-kDa polypeptide which matched a new open reading frame from a human EST () encoding a hypothetical protein of unknown function. The protein was designated as p12. Human EST was identified as the putative human homologue of Schizosaccharomyces pombe Cdm1 by a tBlastn search of the EST data base using S. pombe Cdm1. The open reading frame of human EST encoded a polypeptide of 107 amino acids with a predicted molecular mass of 12.4 kDa, consistent with the experimental findings. p12 is 25% identical to S pombe Cdm1. Both of the 25-kDa polypeptide sequences matched the hypothetical KIAA0039 protein sequence, recently identified as the third subunit of pol delta. Western blotting of immunoaffinity purified calf thymus pol delta revealed the presence of p125, p50, p68 (the KIAA0039 product), and p12. With the identification of p12 mammalian pol delta can now be shown to consist of four subunits. These studies pave the way for more detailed analysis of the possible functions of the mammalian subunits of pol delta. 相似文献
162.
DNA polymerase delta, the key enzyme for eukaryotic chromosomal replication, has been well characterized as consisting of a core enzyme of a 125 kDa catalytic subunit and a smaller 50 kDa subunit. However, less is known about the other proteins that may comprise additional subunits or participate in the macromolecular protein complex that is involved in chromosomal DNA replication. In this study, the properties of calf thymus pol delta preparations isolated by immunoaffinity chromatography were investigated. It is demonstrated for the first time using highly purified preparations that the pol delta heterodimer is associated with other polypeptides in high-molecular weight species that range from 260000 to >500000 in size, as determined by FPLC gel filtration. These preparations are associated with polypeptides of ca. 68-70, 34, 32, and 25 kDa. Similar findings were revealed with glycerol gradient ultracentrifugation. The p68 polypeptide was shown to be a PCNA binding protein by overlay methods with biotinylated PCNA. Protein sequencing of the p68, p34, and p25 polypeptide bands revealed sequences that correspond to the hypothetical protein KIAA0039. KIAA0039 displays a small but significant degree of homology to Schizosaccharomyces pombe Cdc27, which, like Saccharomyces cerevisiae Pol32p, has been described as the third subunit of yeast pol delta. These studies provide evidence that p68 is a subunit of pol delta. In addition, the p68-70 and p32 polypeptides were found to be derived from the 70 and 32 kDa subunits of RPA, respectively. 相似文献
163.
A highly ordered structure in V(D)J recombination cleavage complexes is facilitated by HMG1 总被引:4,自引:0,他引:4
Central to understanding the process of V(D)J recombination is appreciation of the protein–DNA complex which assembles on the recombination signal sequences (RSS). In addition to RAG1 and RAG2, the protein HMG1 is known to stimulate the efficiency of the cleavage reaction. Using electrophoretic mobility shift analysis we show that HMG1 stimulates the in vitro assembly of a stable complex with the RAG proteins on each RSS. We use UV crosslinking studies of this complex with azido-phenacyl derivatized probes to map the contact sites between the RAG proteins, HMG1 derivatives and the RSS. We find that the RAG proteins make contacts at the nonamer, heptamer and adjacent coding region. The HMG1 protein by itself appears to localize at the 3′ side of the nonamer, but a cooperative complex with the RAG proteins is positioned at the 3′ side of the heptamer and adjacent spacer in the 12RSS. In the complex with RAG proteins, HMG1 is positioned primarily in the spacer of the 23RSS. We suggest that bends introduced into these DNA substrates at specific locations by the RAG proteins and HMG1 may help distinguish the 12RSS from the 23RSS and may therefore play an important role in the coordinated reaction. 相似文献
164.
A new cry1I-type gene, cry1Id1, was cloned from a B. thuringiensis isolate, and its nucleotide sequence was determined. The deduced amino acid sequence of Cry1Id1 is 89.7%, 87.2%, and 83.4%
identical to the Cry1Ia, Cry1Ib, and Cry1Ic proteins, respectively. The upstream sequence of the cry1Id1 structural gene was not functional as promoter in B. subtilis. The Cry1Id1 protein, purified from recombinant E. coli cells, had a toxicity comparable to that of Cry1Ia against Plutella xylostella, but it was significantly less active than Cry1Ia against Bombyx mori. Cry1Id1 was not active against the coleopteran insect, Agelastica coerulea.
Received: 19 January 2000 / Accepted: 22 February 2000 相似文献
165.
Koo LS Tschirret-Guth RA Straub WE Moënne-Loccoz P Loehr TM Ortiz de Montellano PR 《The Journal of biological chemistry》2000,275(19):14112-14123
CYP119 from Sulfolobus solfataricus, the first thermophilic cytochrome P450, is stable at up to 85 degrees C. UV-visible and resonance Raman show the enzyme is in the low spin state and only modestly shifts to the high spin state at higher temperatures. Styrene only causes a small spin state shift, but T(1) NMR studies confirm that styrene is bound in the active site. CYP119 catalyzes the H(2)O(2)-dependent epoxidation of styrene, cis-beta-methylstyrene, and cis-stilbene with retention of stereochemistry. This catalytic activity is stable to preincubation at 80 degrees C for 90 min. Site-specific mutagenesis shows that Thr-213 is catalytically important and Thr-214 helps to control the iron spin state. Topological analysis by reaction with aryldiazenes shows that Thr-213 lies above pyrrole rings A and B and is close to the iron atom, whereas Thr-214 is some distance away. CYP119 is very slowly reduced by putidaredoxin and putidaredoxin reductase, but these proteins support catalytic turnover of the Thr-214 mutants. Protein melting curves indicate that the thermal stability of CYP119 does not depend on the iron spin state or the active site architecture defined by the threonine residues. Independence of thermal stability from active site structural factors should facilitate the engineering of novel thermostable catalysts. 相似文献
166.
167.
When directly transmitted infectious diseases are modeled assuming an everlasting induced immunity (and constant contact rate),
there are well-established formulas to deal with, which is not true if we include the loss of induced immunity. In general,
the immunity induced by the disease is everlasting. We propose a model considering the loss of immunity and present methods
for the estimation of two epidemiological parameters: the force of infection and the basic reproduction ratio. We also analyze the effects of the loss of immunity on these parameters. Based on these results, we conclude that reinfection
can play an important role in highly vaccinated populations. 相似文献
168.
采用L-型脯氨酸(L-Pro)作为原料,三甲基硅烷异硫氰酸酯(TMS-ITC)作为偶联试剂制备脯氨酸乙内酰硫脲(TH-Pro).产物经反相HPLC分离纯化,并通过氨基酸组成分析,紫外光谱扫描,质谱和核磁共振等方法鉴定.反应产率高达96%. 相似文献
169.
170.
Xiaofei Lyu Junbao Yu Mo Zhou Bin Ma Guangmei Wang Chao Zhan Guangxuan Han Bo Guan Huifeng Wu Yunzhao Li De Wang 《PloS one》2015,10(3)