全文获取类型
收费全文 | 7697篇 |
免费 | 627篇 |
国内免费 | 198篇 |
专业分类
8522篇 |
出版年
2024年 | 8篇 |
2023年 | 51篇 |
2022年 | 125篇 |
2021年 | 185篇 |
2020年 | 148篇 |
2019年 | 168篇 |
2018年 | 266篇 |
2017年 | 185篇 |
2016年 | 303篇 |
2015年 | 453篇 |
2014年 | 550篇 |
2013年 | 551篇 |
2012年 | 726篇 |
2011年 | 634篇 |
2010年 | 437篇 |
2009年 | 380篇 |
2008年 | 453篇 |
2007年 | 430篇 |
2006年 | 424篇 |
2005年 | 343篇 |
2004年 | 361篇 |
2003年 | 269篇 |
2002年 | 227篇 |
2001年 | 173篇 |
2000年 | 114篇 |
1999年 | 102篇 |
1998年 | 39篇 |
1997年 | 43篇 |
1996年 | 33篇 |
1995年 | 29篇 |
1994年 | 21篇 |
1993年 | 20篇 |
1992年 | 32篇 |
1991年 | 33篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 19篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有8522条查询结果,搜索用时 15 毫秒
11.
O. I. Kiselev V. M. Blinov M. M. Pisareva V. A. Ternovoy A. P. Agafonov D. V. Saraev M. Ju. Eropkin T. G. Lobova V. A. Grigorieva M. P. Grudinin 《Molecular Biology》2008,42(1):70-78
In the second half of 2005, a large-scale outbreak of influenza in poultry and wild birds was caused by a highly pathogenic H5N1 influenza virus in Russia. The level of pathogenicity is a polygenic trait, and most individual genes contribute to the influenza A virus pathogenicity in birds, animals, and humans. The full-length nucleotide sequences were determined for H5N1 strains isolated in the Kurgan region (Western Siberia). The structure of viral proteins was analyzed using the deduced amino acid sequences. The receptor-binding site of hemagglutinin (HA) in strains A/chicken/Kurgan/05/2005 and A/duck/Kurgan/08/2005 was typical for avian influenza viruses and contained Glu and Gly at positions 226 and 228, respectively. The structure of the basic amino acid cluster located within the HA cleavage site was identical in all isolates: QGERRRKKR. According to the neuraminidase structure, all H5N1 isolates from the Kurgan region were assigned to the Z genotype. Amino acid residues typical for the avian influenza virus were revealed in 30 out of 32 positions of M1, M2, NP, PA, and PB2, determining the host range specificity. One of the strains contained Lys at position 627 of PB2. Isolates from the Kurgan region were shown to have a remantadine-sensitive genotype. Both strains contained Glu at position 92 of NS1, indicating that the virus is interferon-resistant. Phylogenetic analysis related the Kurgan isolates to subclade 2 of clade 2 of highly pathogenic H5N1 influenza viruses. 相似文献
12.
Acireductone dioxygenase (ARD) from Klebsiella ATCC 8724 is a metalloenzyme that is capable of catalyzing different reactions with the same substrates (acireductone and O2) depending upon the metal bound in the active site. A model for the solution structure of the paramagnetic Ni2+-containing ARD has been refined using residual dipolar couplings (RDCs) measured in two media. Additional dihedral restraints
based on chemical shift (TALOS) were included in the refinement, and backbone structure in the vicinity of the active site
was modeled from a crystallographic structure of the mouse homolog of ARD. The incorporation of residual dipolar couplings
into the structural refinement alters the relative orientations of several structural features significantly, and improves
local secondary structure determination. Comparisons between the solution structures obtained with and without RDCs are made,
and structural similarities and differences between mouse and bacterial enzymes are described. Finally, the biological significance
of these differences is considered. 相似文献
13.
A monoclonal antibody produced by hydridoma cell line, ATCC HB8209, was used to detect and purify erythropoietin synthesized in a cell-free system. The antibody was raised against the N-terminal 20 residues of erythropoietin. It retained anti-erythropoietin activity in 6 M urea in which most of the cell-free synthesized erythropoietin became soluble and gave an enhanced activity of the antibody. 相似文献
14.
15.
16.
17.
Koung Jin Suh June-Won Cheong Inho Kim Hyeoung-Joon Kim Dong-Yeop Shin Youngil Koh Sung-Soo Yoon Yoo Hong Min Jae-Sook Ahn Yeo-Kyeoung Kim Yun-Gyoo Lee Jeong-Ok Lee Soo-Mee Bang Yeung-Chul Mun Chu-Myoung Seong Yong Park Byung-Soo Kim Junshik Hong Jinny Park Jae Hoon Lee Sung-Yong Kim Hong Ghi Lee 《PloS one》2016,11(11)
Chromosomal translocations are rare in myelodysplastic syndrome (MDS) and their impact on overall survival (OS) and response to hypomethylating agents (HMA) is unknown. The prognostic impact of the revised International Prognostic Scoring System (IPSS-R) and for chromosomal translocations was assessed in 751 patients from the Korea MDS Registry. IPSS-R effectively discriminated patients according to leukaemia evolution risk and OS. We identified 40 patients (5.3%) carrying translocations, 30 (75%) of whom also fulfilled complex karyotype criteria. Translocation presence was associated with a shorter OS (median, 12.0 versus 79.7 months, P < 0.01). Multivariate analysis demonstrated that translocations (hazard ratio [HR] 1.64 [1.06–2.63]; P = 0.03) as well as age, sex, IPSS-R, and CK were independent predictors of OS. In the IPSS-R high and very high risk subgroup (n = 260), translocations remained independently associated with OS (HR 1.68 [1.06–2.69], P = 0.03) whereas HMA treatment was not associated with improved survival (median OS, 20.9 versus 21.2 months, P = 0.43). However, translocation carriers exhibited enhanced survival following HMA treatment (median 2.1 versus 12.4 months, P = 0.03). Our data suggest that chromosomal translocation is an independent predictor of adverse outcome and has an additional prognostic value in discriminating patients with MDS having higher risk IPSS-R who could benefit from HMA treatment. 相似文献
18.
Outer membrane proteins (OMPs) of pathogenic bacteria have been used as protective antigens in developing bacterial vaccines. In the present study, we compared the antibody responses to a Pseudomonas aeruginosa OMP vaccine elicited in humans and rabbits by immunization. Immunization with the vaccine induced high titers of serum IgG antibody both in rabbits and humans but reactivities of the induced antibodies with the OMPs were different. The rabbit immune sera recognized most of the OMPs in the vaccine both in immunoblot and immunoprecipitation analyses. In contrast, a great variation in band pattern and intensity was observed among the human immune sera in immunoblot analysis, but not in immunoprecipitation analysis. Denaturation of the OMPs did not affect the binding activity of the rabbit immune sera as determined by ELISA, but substantially reduced those of the human immune sera and anti-OMP IgG purified from a pooled normal human plasma. These data suggest that antibody response to P. aeruginosa OMPs elicited by immunization in humans is mainly directed against discontinuous or conformation-dependent epitopes, which should be taken into account in developing vaccines, especially for OMP-derived synthetic peptides. 相似文献
19.
Ondřej Korábek Lucie Juřičková Adam Petrusek 《Journal of Zoological Systematics and Evolutionary Research》2020,58(4):944-956
Exact locations of glacial refugia are relevant for the study of contemporary biodiversity, not only as places less disturbed during the climatic changes but also as sources of rapid expansion of the biota after the Last Glacial cycle. If continuously inhabited over several of the Quaternary glacial cycles, the refugia are readily identifiable by the accumulated genetic diversity. However, the sources of the Holocene range expansion, particularly important for the emergence of present-day bio- and phylogeographic patterns and for realistic estimation of species’ expansion rates, might have been located at the fringes of the glacial species ranges and lack unique lineages. This problem is pertinent when the variation is explored at slowly evolving genetic markers. We suggest that the location of such source refugia may be approximated by reconstructing the geographic location as a continuous trait evolving along the branches of a phylogenetic tree. We applied this approach, using the BEAST software, on two large southeast European land snail species: Caucasotachea vindobonensis and Helix thessalica. We found evidence for C. vindobonensis refugia in the western Balkans; notable is an apparently old refugium in Bosnia and Herzegovina. The plausible sources of the species’ Holocene range expansion, however, were located around the south-western end of the Carpathians. Although the source areas were likely similar in H. thessalica, some expansion sources suggested by the analyses (e.g., Podolia, Ukraine) appeared implausible and driven by sampling clustered in that area. The applied approach allows for additional exploitation of the mitochondrial data gathered during the past two decades of animal phylogeography studies. 相似文献
20.
Yoo KS Ahn JE Han JS Seo E Otgonbayar GE Han NS 《Journal of microbiology and biotechnology》2011,21(12):1243-1249
This study was performed to examine the use of NaOCl as an alternative antimicrobial compound in winemaking because of the potential health problems that may arise as a result of the use of SO2. For this, the blank (non-treated), control (SO2-added), and sample (NaOCl-treated) wines were made, and microbial and chemical changes including sensory characteristics were analyzed during the fermentation periods. Treatment of grapes with NaOCl decreased the initial contaminating microbial population in grape must, resulting in higher growth of yeast and lactic acid bacteria. After 200 days of fermentation, the chemical analysis of sample wine revealed that it had higher ethanol content, redness (a*), and concentrations of fruity ester compounds and lower total acidity than the control. In the sensory analyses, the sample wine obtained a higher overall acceptability score (5.70) than the control (4.26). This result reveals that NaOCl can be used as an alternative to SO2 in winemaking for inhibiting the growth of contaminating microorganisms. 相似文献