全文获取类型
收费全文 | 5497篇 |
免费 | 411篇 |
国内免费 | 1篇 |
出版年
2023年 | 30篇 |
2022年 | 33篇 |
2021年 | 134篇 |
2020年 | 61篇 |
2019年 | 90篇 |
2018年 | 123篇 |
2017年 | 141篇 |
2016年 | 191篇 |
2015年 | 252篇 |
2014年 | 304篇 |
2013年 | 367篇 |
2012年 | 459篇 |
2011年 | 481篇 |
2010年 | 269篇 |
2009年 | 191篇 |
2008年 | 281篇 |
2007年 | 306篇 |
2006年 | 286篇 |
2005年 | 302篇 |
2004年 | 259篇 |
2003年 | 227篇 |
2002年 | 197篇 |
2001年 | 86篇 |
2000年 | 52篇 |
1999年 | 54篇 |
1998年 | 60篇 |
1997年 | 28篇 |
1996年 | 28篇 |
1995年 | 34篇 |
1994年 | 17篇 |
1993年 | 24篇 |
1992年 | 26篇 |
1991年 | 26篇 |
1990年 | 35篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 37篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 22篇 |
1977年 | 13篇 |
1976年 | 21篇 |
1975年 | 14篇 |
1974年 | 19篇 |
1973年 | 24篇 |
排序方式: 共有5909条查询结果,搜索用时 189 毫秒
1.
Background
Radial chromosome positioning in interphase nuclei is nonrandom and can alter according to developmental, differentiation, proliferation, or disease status. However, it is not yet clear when and how chromosome repositioning is elicited. 相似文献2.
3.
Paclitaxel enhances macrophage IL-12 production in tumor-bearing hosts through nitric oxide. 总被引:9,自引:0,他引:9
D W Mullins C J Burger K D Elgert 《Journal of immunology (Baltimore, Md. : 1950)》1999,162(11):6811-6818
Tumor-induced macrophages (Mphis) mediate immunosuppression, in part, through increased production of factors that suppress T cell responsiveness and underproduction of positive regulatory cytokines. Pretreatment of tumor-bearing host (TBH) Mphis with the anticancer agent paclitaxel (Taxol) partially reverses tumor-induced Mphi suppressor activity, suggesting that paclitaxel may restore TBH Mphi production of proimmune factors. Because paclitaxel demonstrates LPS-mimetic capabilities and increased production of the LPS-induced immunostimulatory cytokine IL-12 could account for enhanced T cell responsiveness, we investigated whether paclitaxel induces Mphi IL-12 production. Tumor growth significantly down-regulated Mphi IL-12 p70 production through selective dysregulation of IL-12 p40 expression. LPS stimulation failed to overcome tumor-induced dysregulation of p40 expression. In contrast, paclitaxel significantly enhanced both normal host and TBH Mphi IL-12 p70 production in vitro, although TBH Mphi IL-12 production was lower than that of similarly treated normal host Mphis. Paclitaxel enhanced p40 expression in a dose-dependent manner. Through reconstituted Mphi IL-12 expression, paclitaxel pretreatment relieved tumor-induced Mphi suppression of T cell alloreactivity. Blocking Mphi NO suppressed paclitaxel's ability to induce IL-12 production. This suggests that paclitaxel-induced activities may involve a NO-mediated autocrine induction pathway. Collectively, these data demonstrate that paclitaxel restores IL-12 production in the TBH and ascribe a novel immunotherapeutic component to the pleiotropic activities of NO. Through its capacity to induce IL-12 production, paclitaxel may contribute to the correction of tumor-induced immune dysfunction. 相似文献
4.
5.
The diminished production of arachidonic acid oxygenation products by elicited mouse peritoneal macrophages: possible mechanisms 总被引:12,自引:0,他引:12
6.
Joanna Nakonieczna Ewelina Michta Magda Rybicka Mariusz Grinholc Anna Gwizdek-Wiśniewska Krzysztof P Bielawski 《BMC microbiology》2010,10(1):323
Background
Staphylococcus aureus, a major human pathogen causes a wide range of disease syndromes. The most dangerous are methicillin-resistant S. aureus (MRSA) strains, resistant not only to all β-lactam antibiotics but also to other antimicrobials. An alarming increase in antibiotic resistance spreading among pathogenic bacteria inclines to search for alternative therapeutic options, for which resistance can not be developed easily. Among others, photodynamic inactivation (PDI) of S. aureus is a promising option. Photodynamic inactivation is based on a concept that a non toxic chemical, called a photosensitizer upon excitation with light of an appropriate wavelength is activated. As a consequence singlet oxygen and other reactive oxygen species (e.g. superoxide anion) are produced, which are responsible for the cytotoxic effect towards bacterial cells. As strain-dependence in photodynamic inactivation of S. aureus was observed, determination of the molecular marker(s) underlying the mechanism of the bacterial response to PDI treatment would be of great clinical importance. We examined the role of superoxide dismutases (Sod) in photodynamic inactivation of S. aureus as enzymes responsible for oxidative stress resistance. 相似文献7.
The in vitro DNA-cleaving activity of neocarzinostatin, a protein antibiotic, is strongly but reversibly inhibited by anaerobiosis. Half-maximal activity is seen in the presence of 0.25 mM O2. The stability of neocarzinostatin, as demonstrated by its ability to cleave DNA, is significantly reduced in light. Inactivation by light is complete and irreversible. 相似文献
8.
Nathan Downs Alfio Parisi Joanna Turner David Turnbull 《Photochemical & photobiological sciences》2008,7(6):700-710
A technique has been developed to represent erythemally effective ultraviolet radiation exposure within a school environment. The technique models the erythemally effective exposure onto a horizontal plane representation of a mapped school environment located in Hervey Bay (25 degrees S, 153 degrees E), Australia. The input parameters used to model the ultraviolet exposures received within the school playground included the measured sky view, ground albedo and standing surface albedo. Estimates of the erythemally effective ultraviolet exposure received within the school playground during morning tea and lunch time meal breaks during a winter and summer school day are presented. The influence of tree shade and building structure was found to vary significantly with solar zenith angle modelled over the winter and summer school meal break times with horizontal plane exposures predicted to vary from between 0 and 7 SED at different locations within the playground. The technique presented provides a method that can be followed to examine the effect of surrounding buildings and surface structures of real environments on the predicted horizontal plane ultraviolet exposure. 相似文献
9.
Carroll D. Arnett Joanna S. Fowler Robert R. MacGregor David J. Schlyer Alfred P. Wolf Bengt Långström Christer Halldin 《Journal of neurochemistry》1987,49(2):522-527
The distribution of carbon-11-labeled L-deprenyl, an irreversible inhibitor of monoamine oxidase type B (MAO-B), was determined in the baboon brain by positron emission tomography. The irreversible blood-to-brain transfer constant (influx constant, Ki) was measured using a complete metabolite-corrected arterial plasma concentration curve. This influx constant was used as a measure of functional enzyme activity for sequential determinations of MAO-B recovery following a single high dose of unlabeled l -deprenyl. The half-life for turnover of MAO-B was thus determined to be 30 days. Using appropriate irreversible inhibitors, this procedure should be generally useful for determining enzyme turnover rates in any organ in vivo and can be applied to some human studies as well. 相似文献
10.