全文获取类型
收费全文 | 4780篇 |
免费 | 332篇 |
国内免费 | 5篇 |
出版年
2024年 | 3篇 |
2023年 | 40篇 |
2022年 | 79篇 |
2021年 | 156篇 |
2020年 | 87篇 |
2019年 | 114篇 |
2018年 | 169篇 |
2017年 | 116篇 |
2016年 | 188篇 |
2015年 | 269篇 |
2014年 | 288篇 |
2013年 | 347篇 |
2012年 | 435篇 |
2011年 | 466篇 |
2010年 | 287篇 |
2009年 | 233篇 |
2008年 | 262篇 |
2007年 | 332篇 |
2006年 | 255篇 |
2005年 | 232篇 |
2004年 | 220篇 |
2003年 | 186篇 |
2002年 | 152篇 |
2001年 | 34篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 28篇 |
1997年 | 19篇 |
1996年 | 18篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有5117条查询结果,搜索用时 15 毫秒
31.
Raisa P. Gorshkova Natalia I. Korchagina Tatianna A. Medonova Elena N. Kalmykova Natalia N. Besednova Yury S. Ovodov 《Carbohydrate research》1980,84(2):237-243
Lipopolysaccharides (LPS) from various strains of Yersinia pseudotuberculosis type V have been isolated and characterised. Differences in sugar composition and serological activity of LPS from various strains within the same subtype of Y. pseudotuberculosis have been revealed. 相似文献
32.
Michael Z. Ludwig Ilya I. Uspensky Andrew I. Ivanov Maria R. Kopantseva Christem M. Dianov Natalia A. Tamarina Leonid I. Korochkin 《Biochemical genetics》1991,29(5-6):215-239
PEB-me is a predominant protein of matureDrosophila melanogaster ejaculatory bulbs. It is resolved into four or five closely spaced subfractions (apparent molecular weight 35–39 kD) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Four electrophoretic variants of PEB-me differing in apparent molecular weight by 200–800 daltons were found. These appear to be controlled by four alleles of a gene (peb) located by recombination and deletion mapping to the 60F1-2 region of chromosome 2. A minor ejaculatory bulb protein of ca. 80 kD (hPEB) was found to be immunochemically related to PEB and possibly encoded bypeb. PEB is not detected by immunoblotting techniques in virgin females, in male tissues other than the ejaculatory bulb, or during developmental stages preceding the formation of this organ. The results of transplantations of genital imaginal discs and of immature ejaculatory bulbs between two strains having different PEB alleles suggest that the ejaculatory bulb is the site of PEB synthesis. In flies mutant fortra, tra-2, dsx, orix, tissue specificity of PEB localization is retained and the protein is found whenever the ejaculatory bulb is formed, regardless of the chromosomal sex of the fly. The protein is transferred into the female genital duct during mating, where it can be detected for up to 12 hr. Possible functions of PEB inDrosophila reproduction are discussed. 相似文献
33.
Dimiter S. Dimitrov Georgi A. Georgiev Natalia G. Stoicheva Trayko T. Traykov 《Journal of theoretical biology》1982,96(4):517-532
Double-valued pressure-volume relationships in dynamic conditions for spherical membranes, modelling the lung alveoli, were obtained at small deformations. This hysteretic behavior was considered to be produced by at least three independent mechanisms: (1) the lung parenchyma exhibits viscoelastic properties; (2) the lung surface film, independent of the tissue, exhibits viscoelastic properties and (3) the pressure acting on the inner membrane surface depends on the rate of the alveolus volume change, due to the air viscous resistance in the bronchial tree. In each case, the maximum volume change, the hysteresis loop area, the tilt angle of the hysteresis loop and the relaxation time of the system were calculated. The results show pronounced hysteresis at normal breathing due to the air viscous resistance and smaller one due to the tissue and surface viscoelastic properties. In quasistatic conditions the values of the surface viscoelasticity and the tissue viscoelasticity effects are comparable or different, depending on the concrete external conditions. Comparison with the available experimental data is discussed in detail. 相似文献
34.
35.
Loren P. Albert Natalia Restrepo‐Coupe Marielle N. Smith Jin Wu Cecilia Chavana‐Bryant Neill Prohaska Tyeen C. Taylor Giordane A. Martins Philippe Ciais Jiafu Mao M. Altaf Arain Wei Li Xiaoying Shi Daniel M. Ricciuto Travis E. Huxman Sean M. McMahon Scott R. Saleska 《Global Change Biology》2019,25(11):3591-3608
Plant phenology—the timing of cyclic or recurrent biological events in plants—offers insight into the ecology, evolution, and seasonality of plant‐mediated ecosystem processes. Traditionally studied phenologies are readily apparent, such as flowering events, germination timing, and season‐initiating budbreak. However, a broad range of phenologies that are fundamental to the ecology and evolution of plants, and to global biogeochemical cycles and climate change predictions, have been neglected because they are “cryptic”—that is, hidden from view (e.g., root production) or difficult to distinguish and interpret based on common measurements at typical scales of examination (e.g., leaf turnover in evergreen forests). We illustrate how capturing cryptic phenology can advance scientific understanding with two case studies: wood phenology in a deciduous forest of the northeastern USA and leaf phenology in tropical evergreen forests of Amazonia. Drawing on these case studies and other literature, we argue that conceptualizing and characterizing cryptic plant phenology is needed for understanding and accurate prediction at many scales from organisms to ecosystems. We recommend avenues of empirical and modeling research to accelerate discovery of cryptic phenological patterns, to understand their causes and consequences, and to represent these processes in terrestrial biosphere models. 相似文献
36.
Natalia Mroczek-Sosnowska Monika Łukasiewicz Dobrochna Adamek Maciej Kamaszewski Jan Niemiec Agnieszka Wnuk-Gnich 《Archives of animal nutrition》2017,71(4):327-332
The objective of this study was to evaluate bone resistance after in ovo administration of copper nanoparticles (NanoCu) and to determine the number of cells positive for proliferating cell nuclear antigen (PCNA) in the femoral bones of broiler chickens (n = 12 per group). The study demonstrated that femoral bones from the NanoCu group were characterised by a higher weight and volume and by significantly greater resistance to fractures compared to the Control group. NanoCu promoted the proliferation of PCNA-positive cells in the long bones of chickens. A significantly higher number of PCNA-positive cells in the bones of birds in the NanoCu group compared with the Control group (137 and 122, respectively) indicate a stimulatory effect during embryogenesis. Considering the improvement in bone resistance to fractures and the effect of NanoCu on the number of PCNA-positive cells in femoral bones, NanoCu may be an alternative agent to minimise the ever-present problem of weak bones in broiler chickens. 相似文献
37.
Franziska Pern Natalia Bogdanova Peter Schürmann Min Lin Aysun Ay Florian L?nger Peter Hillemanns Hans Christiansen Tjoung-Won Park-Simon Thilo D?rk 《PloS one》2012,7(10)
Triple-negative breast cancer (TNBC) is an aggressive form of breast carcinoma with a poor prognosis. Recent evidence suggests that some patients with TNBC harbour germ-line mutations in DNA repair genes which may render their tumours susceptible to novel therapies such as treatment with PARP inhibitors. In the present study, we have investigated a hospital-based series of 40 German patients with TNBC for the presence of germ-line mutations in BRCA1, BRCA2, PALB2, and BRD7 genes. Microfluidic array PCR and next-generation sequencing was used for BRCA1 and BRCA2 analysis while conventional high-resolution melting and Sanger sequencing was applied to study the coding regions of PALB2 and BRD7, respectively. Truncating mutations in BRCA1 were found in six patients, and truncating mutations in BRCA2 and PALB2 were detected in one patient each, whereas no truncating mutation was identified in BRD7. One patient was a double heterozygote for the PALB2 mutation, c.758insT, and a BRCA1 mutation, c.927delA. Our results confirm in a hospital-based setting that a substantial proportion of German TNBC patients (17.5%) harbour germ-line mutations in genes involved in homology-directed DNA repair, with a preponderance of BRCA1 mutations. Triple-negative breast cancer should be considered as an additional criterion for future genetic counselling and diagnostic sequencing. 相似文献
38.
DNA vaccination can break immunological tolerance to PrP in wild-type mice and attenuates prion disease after intracerebral challenge
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fernandez-Borges N Brun A Whitton JL Parra B Diaz-San Segundo F Salguero FJ Torres JM Rodriguez F 《Journal of virology》2006,80(20):9970-9976
Transmissible spongiform encephalopathies (TSEs) can be ameliorated by prion protein (PrP)-specific antibodies, but active immunization is complicated by immune tolerance to the normal cellular host protein (PrP(C)). Here, we show that DNA immunization of wild-type mice can break immune tolerance against the prion protein, resulting in the induction of PrP-specific antibody and T-cell responses. PrP immunogenicity was increased by fusion to the lysosomal targeting signal from LIMPII (lysosomal integral membrane protein type II). Although mice immunized with a PrP-LIMPII DNA vaccine showed a dramatic delay in the onset of early disease signs after intracerebral challenge, immunization against PrP also had some deleterious effects. These results clearly confirm the feasibility of using active immunization to protect against TSEs and, in the absence of effective treatments, indicate a suitable alternative for combating the spread of these diseases. 相似文献
39.
Valery N Urakov Igor A Valouev Natalia V Kochneva-Pervukhova Anna N Packeiser Alexander Yu Vishnevsky Oleg O Glebov Vladimir N Smirnov Michael D Ter-Avanesyan 《BMC molecular biology》2006,7(1):34-13
Background
Termination of translation in eukaryotes requires two release factors, eRF1, which recognizes all three nonsense codons and facilitates release of the nascent polypeptide chain, and eRF3 stimulating translation termination in a GTP-depended manner. eRF3 from different organisms possess a highly conservative C region (eRF3C), which is responsible for the function in translation termination, and almost always contain the N-terminal extension, which is inessential and vary both in structure and length. In the yeast Saccharomyces cerevisiae the N-terminal region of eRF3 is responsible for conversion of this protein into the aggregated and functionally inactive prion form. 相似文献40.
Nikulin A Eliseikina I Tishchenko S Nevskaya N Davydova N Platonova O Piendl W Selmer M Liljas A Drygin D Zimmermann R Garber M Nikonov S 《Nature structural biology》2003,10(2):104-108
The L1 protuberance of the 50S ribosomal subunit is implicated in the release/disposal of deacylated tRNA from the E site. The apparent mobility of this ribosomal region has thus far prevented an accurate determination of its three-dimensional structure within either the 50S subunit or the 70S ribosome. Here we report the crystal structure at 2.65 A resolution of ribosomal protein L1 from Sulfolobus acidocaldarius in complex with a specific 55-nucleotide fragment of 23S rRNA from Thermus thermophilus. This structure fills a major gap in current models of the 50S ribosomal subunit. The conformations of L1 and of the rRNA fragment differ dramatically from those within the crystallographic model of the T. thermophilus 70S ribosome. Incorporation of the L1-rRNA complex into the structural models of the T. thermophilus 70S ribosome and the Deinococcus radiodurans 50S subunit gives a reliable representation of most of the L1 protuberance within the ribosome. 相似文献