全文获取类型
收费全文 | 616篇 |
免费 | 103篇 |
国内免费 | 9篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 27篇 |
2014年 | 22篇 |
2013年 | 32篇 |
2012年 | 29篇 |
2011年 | 37篇 |
2010年 | 18篇 |
2009年 | 26篇 |
2008年 | 20篇 |
2007年 | 30篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 20篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1972年 | 7篇 |
1969年 | 4篇 |
1956年 | 7篇 |
1955年 | 5篇 |
1948年 | 4篇 |
1930年 | 4篇 |
排序方式: 共有728条查询结果,搜索用时 15 毫秒
161.
162.
Charles V. Benton Howard M. Hodge Donald L. Fine 《In vitro cellular & developmental biology. Plant》1978,14(2):192-199
Summary A cell culture method is described for the large-scale (50 to 150 1) production of Mason-Pfizer monkey virus and squirrel
monkey virus, two primate retroviruses. Virus production was achieved with suspension cultures of chronically infected A204
human rhabdomyosarcoma cells harvested and clarified in the logarithmic stages of cell culture growth. Methods for the subsequent
purification and concentration of virus material utilizing zonal centrifugation also are described. Applications of these
methodologies resulted in products that afforded biochemical comparisons of these agents in a manner such that host cell-derived
variations were minimized. These data indicated that high levels of production and efficient recovery and purification of
virus material were achieved.
This work was supported by Contract NO1-CO-25423 with the National Cancer Institute, National Institutes of Health. 相似文献
163.
Qureshi H Ma ZM Huang Y Hodge G Thomas MA DiPasquale J DeSilva V Fritts L Bett AJ Casimiro DR Shiver JW Robert-Guroff M Robertson MN McChesney MB Gilbert PB Miller CJ 《Journal of virology》2012,86(4):2239-2250
The Step Trial showed that the MRKAd5 HIV-1 subtype B Gag/Pol/Nef vaccine did not protect men from HIV infection or reduce setpoint plasma viral RNA (vRNA) levels but, unexpectedly, it did modestly enhance susceptibility to HIV infection in adenovirus type 5 (Ad5)-seropositive, uncircumcised men. As part of the process to understand the results of the Step Trial, we designed a study to determine whether rhesus macaques chronically infected with a host-range mutant Ad5 (Ad5hr) and then immunized with a replication defective Ad5 SIVmac239 Gag/Pol/Nef vaccine were more resistant or susceptible to SIV infection than unimmunized rhesus macaques challenged with a series of escalating dose penile exposures to SIVmac 251. The Ad5 SIV vaccine induced CD8(+) T cell responses in 70% of the monkeys, which is similar to the proportion of humans that responded to the vaccine in the Step Trial. However, the vaccine did not protect vaccinated animals from penile SIV challenge. At the lowest SIV exposure dose (10(3) 50% tissue culture infective doses), 2 of 9 Ad5-seropositive animals immunized with the Ad5 SIV vaccine became infected compared to 0 of 34 animals infected in the other animal groups (naive animals, Ad5-seropositive animals immunized with the empty Ad5 vector, Ad5-seronegative animals immunized with the Ad5 SIV vaccine, and Ad5-seronegative animals immunized with the empty Ad5 vector). Penile exposure to more concentrated virus inocula produced similar rates of infection in all animal groups. Although setpoint viral loads were unaffected in Step vaccinees, the Ad5 SIV-immunized animals had significantly lower acute-phase plasma vRNA levels compared to unimmunized animals. Thus, the results of the nonhuman primate (NHP) study described here recapitulate the lack of protection against HIV acquisition seen in the Step Trial and suggest a greater risk of infection in the Ad5-seropositive animals immunized with the Ad5 SIV vaccine. Further studies are necessary to confirm the enhancement of virus acquisition and to discern associated mechanisms. 相似文献
164.
Campbell SJ Edwards RA Leung CC Neculai D Hodge CD Dhe-Paganon S Glover JN 《The Journal of biological chemistry》2012,287(28):23900-23910
The repair of DNA double strand breaks by homologous recombination relies on the unique topology of the chains formed by Lys-63 ubiquitylation of chromatin to recruit repair factors such as breast cancer 1 (BRCA1) to sites of DNA damage. The human RING finger (RNF) E3 ubiquitin ligases, RNF8 and RNF168, with the E2 ubiquitin-conjugating complex Ubc13/Mms2, perform the majority of Lys-63 ubiquitylation in homologous recombination. Here, we show that RNF8 dimerizes and binds to Ubc13/Mms2, thereby stimulating formation of Lys-63 ubiquitin chains, whereas the related RNF168 RING domain is a monomer and does not catalyze Lys-63 polyubiquitylation. The crystal structure of the RNF8/Ubc13/Mms2 ternary complex reveals the structural basis for the interaction between Ubc13 and the RNF8 RING and that an extended RNF8 coiled-coil is responsible for its dimerization. Mutations that disrupt the RNF8/Ubc13 binding surfaces, or that truncate the RNF8 coiled-coil, reduce RNF8-catalyzed ubiquitylation. These findings support the hypothesis that RNF8 is responsible for the initiation of Lys-63-linked ubiquitylation in the DNA damage response, which is subsequently amplified by RNF168. 相似文献
165.
Plastic plants and patchy soils 总被引:5,自引:0,他引:5
Hodge A 《Journal of experimental botany》2006,57(2):401-411
Soil nutrients are distributed in a non-uniform or 'patchy' manner. It is well established that the modular nature of root systems allows them to show both morphological and/or physiological plasticity upon encountering nutrient-rich patches. These plastic responses are widely believed to be foraging mechanisms by the plant to enhance nutrient resource capture. Although morphological plasticity has traditionally been viewed as the more expensive option as it requires new root construction, more recent evidence suggests this may not necessarily be the case. Moreover, plants may be able to recapture most of the initial outlay involved in new root construction, again lowering the overall cost to the plant. Under natural conditions the roots of most plant species have an additional nutrient acquisition mechanism namely mycorrhizal symbiosis. However, the impact of these important symbiotic associations upon the host plant's response to nutrient patches has received relatively little attention. The mycorrhizal fungal symbiont should, in theory, be better able to compete directly with the rest of the microbial community for the nutrients in the patch. This could potentially be important to the host plant, as generally, root proliferation responses are more important for interspecific plant, than plant-microbial, competition. 相似文献
166.
167.
M. J. S. Hodge 《Journal of the history of biology》2009,42(3):399-416
When socio-economic contexts are sought for Darwin’s science, it is customary to turn to the Industrial Revolution. However,
important issues about the long run of England’s capitalisms can only be recognised by taking a wider view than Industrial
Revolution historiographies tend to engage. The role of land and finance capitalisms in the development of the empire is one
such issue. If we historians of Darwin’s science allow ourselves a distinction between land and finance capitalisms on the
one hand and industrial capitalism on the other; and if we ask with which side of this divide were Darwin and his theory of
branching descent by natural selection aligned, then reflection on leading features of that theory, including its Malthusian
elements, suggests that the answer is often and largely, though not exclusively: on the land side. The case of Wallace, socialist
opponent of land capitalism, may not be as anomalous for this suggestion as one might at first think. Social and economic
historians have reached no settled consensuses on the long-run of England’s capitalisms. We historians of Darwin’s science
would do well to import some of these unsettled states of discussion into our own work over the years to come. 相似文献
168.
169.
Jennelle C. Hodge Karen T.Cuenco Priya Somasundaram Carolien I. M. Panhuysen Elizabeth A. Stewart Cynthia C. Morton 《Human genetics》2009,125(3):257-263
Uterine leiomyomata (UL) are the most common female pelvic tumors and the primary indication for hysterectomy in the United
States. We assessed genetic liability for UL by a known embryonic proliferation modulator, HMGA2, in 248 families ascertained through medical record-confirmed affected sister-pairs. Using a (TC)
n
repeat in the 5′ UTR and 17 SNPs spanning HMGA2, permutation-based association tests identified a significant increase in transmission of a single TC repeat allele (TC227)
with UL (allele-specific P = 0.00005, multiple testing corrected min-P = 0.0049). The hypothesis that TC227 is a pathogenic variant is supported by a trend towards higher HMGA2 expression in TC227 allele-positive compared with non-TC227 UL tissue as well as by absence of culpable exonic sequence variants.
HMGA2 has also been suggested recently by three genome-wide SNP studies to influence human height variation, and our examination
of the affected sister-pair families revealed a significant association of TC227 with decreased height (allele-specific P = 0.00033, multiple testing corrected min-P = 0.016). Diminished stature and elevated risk of UL development have both been correlated with an earlier age of menarche,
which may be the biological mechanism for TC227 effects as a tendency of women with TC227 to have an earlier onset of menarche
was identified in our study population. These results indicate HMGA2 has a role in two growth-related phenotypes, UL predisposition and height, of which the former may affect future medical
management decisions for many women.
J. C. Hodge and K. T.Cuenco are to be regarded as co-First Authors. 相似文献
170.
采用红外气体分析仪,于2008年10月17-19日连续3个昼夜原位监测了荷木的树干CO_2释放通量、树干温度、木质部液流密度和CO_2浓度.结果表明:树干CO_2释放通量(EA)日变化呈S形曲线,不同径级间差异显著.EA与树干温度呈显著幂函数关系(0.24Abstract: By using a Li-820 infra-red CO_2 gas analyzer, an in situ measurement of Schima super-ba stem CO_2 efflux was conducted for three consecutive days from 17 to 19 October 2008. In the meantime, the stem temperature, xylem sap efflux density, and xylem CO_2 concentration were measured. The stem CO_2 efflux had a diurnal variation of "S" pattern, and differed significantly with stem diameter. There was a significant exponential relationship between stem CO_2 efflux and stem temperature (0. 24 < R~2 < 0. 78). The temperature coefficient (b) and regression coeffi-cient (R~2) were higher at nighttime than at daytime, and the Q_(10) value ranged from 2. 01 to 2. 79. The stem CO_2 efflux correlated significantly with the xylem CO_2 concentration, and the best regression curve was cubic (R~2= 0. 48). Excluding the effects of stem temperature, the stem CO_2 efflux showed a significant negative correlation with xylem sap flux density (r =-0.462). Therefore, only using simple temperature function to estimate stem CO_2 efflux would yield a significant error, and xylem sap flux should be taken into consideration in the stem CO_2 emux estimation. 相似文献