全文获取类型
收费全文 | 1307篇 |
免费 | 147篇 |
专业分类
1454篇 |
出版年
2022年 | 9篇 |
2021年 | 31篇 |
2020年 | 15篇 |
2019年 | 23篇 |
2018年 | 26篇 |
2017年 | 18篇 |
2016年 | 32篇 |
2015年 | 44篇 |
2014年 | 61篇 |
2013年 | 88篇 |
2012年 | 83篇 |
2011年 | 101篇 |
2010年 | 43篇 |
2009年 | 61篇 |
2008年 | 63篇 |
2007年 | 62篇 |
2006年 | 44篇 |
2005年 | 34篇 |
2004年 | 45篇 |
2003年 | 39篇 |
2002年 | 44篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 24篇 |
1988年 | 25篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1975年 | 8篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1971年 | 11篇 |
1969年 | 10篇 |
1965年 | 8篇 |
排序方式: 共有1454条查询结果,搜索用时 15 毫秒
101.
In Norway, there was considerable overlap between the poor house, the workhouse, and correctional facilities. An assemblage of human skeletal remains from Oslo's House of Correction cemetery, largely comprised of individuals disturbed during municipal development in 1989, consists of c. 314 individuals who died as inmates or residents; many were disabled or elderly. Although names were recorded at death, the cemetery lacked grave markers or a map, with no expectation families might one day reclaim relatives. All remains have been aged and sexed anthropologically, with samples collected for biomolecular investigations. Despite extensive archival documentation, including names recorded in the House of Correction church book, their identities are shrouded by time. Observations of age, injury, and disease can suggest why inmates ended up in the House of Correction cemetery. But there, individual stories end and identities are lost. 相似文献
102.
103.
104.
Joshua A. Drew Jennifer M. Gumm 《Ethology : formerly Zeitschrift fur Tierpsychologie》2015,121(1):2-7
Small‐scale population differentiation among coral reef fishes may be more common than previously thought. New molecular technologies have informed patterns of differentiation, while experimental approaches focusing on larval abilities to limit distribution have explored processes leading to diversification. Building upon a recently published paper by Wismer et al. that examined population level differences in learning and cooperative behaviors in cleaner wrasse (Labroides dimidiatus), we use a phylogenetic framework to explore how social behaviors are distributed among wrasses in the Labrichthyines clade. Establishing links between social behavior and speciation across the phylogeny allows us explore how social behaviors such as learning and cooperation may also act as possible mechanisms driving diversification at the microevolutionary scale. 相似文献
105.
Viktoria Stab Sandra Nitsche Thomas Niezold Michael Storcksdieck genannt Bonsmann Andrea Wiechers Bettina Tippler Drew Hannaman Christina Ehrhardt Klaus überla Thomas Grunwald Matthias Tenbusch 《PloS one》2013,8(8)
The Respiratory Syncytial Virus (RSV) and Influenza A Virus (IAV) are both two major causative agents of severe respiratory tract infections in humans leading to hospitalization and thousands of deaths each year. In this study, we evaluated the immunogenicity and efficacy of a combinatory DNA vaccine in comparison to the single component vaccines against both diseases in a mouse model. Intramuscular electroporation with plasmids expressing the hemagglutinin (HA) of IAV and the F protein of RSV induced strong humoral immune responses regardless if they were delivered in combination or alone. In consequence, high neutralizing antibody titers were detected, which conferred protection against a lethal challenge with IAV. Furthermore, the viral load in the lungs after a RSV infection could be dramatically reduced in vaccinated mice. Concurrently, substantial amounts of antigen-specific, polyfunctional CD8+ T-cells were measured after vaccination. Interestingly, the cellular response to the hemagglutinin was significantly reduced in the presence of the RSV-F encoding plasmid, but not vice versa. Although these results indicate a suppressive effect of the RSV-F protein, the protective efficacy of the combinatory vaccine was comparable to the efficacy of both single-component vaccines. In conclusion, the novel combinatory vaccine against RSV and IAV may have great potential to reduce the rate of severe respiratory tract infections in humans without increasing the number of necessary vaccinations. 相似文献
106.
107.
Molitor-Dart ML Andrassy J Kwun J Kayaoglu HA Roenneburg DA Haynes LD Torrealba JR Bobadilla JL Sollinger HW Knechtle SJ Burlingham WJ 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(10):6749-6761
We hypothesize that developmental exposure to noninherited maternal Ags (NIMA) results in alloantigen-specific natural and adaptive T regulatory (T(R)) cells. We compared offspring exposed to maternal H-2(d) (NIMA(d)) with nonexposed controls. In vitro assays did not reveal any differences in T cell responses pretransplant. Adoptive transfer assays revealed lower lymphoproliferation and greater cell surface TGF-beta expression on CD4(+) T cells of NIMA(d)-exposed vs control splenocytes. NIMA(d)-exposed splenocytes exhibited bystander suppression of tetanus-specific delayed-type hypersensitivity responses, which was reversed with Abs to TGF-beta and IL-10. Allospecific T effector cells were induced in all mice upon i.v. challenge with B6D2F1 splenocytes or a DBA/2 heart transplant, but were controlled in NIMA(d)-exposed mice by T(R) cells to varying degrees. Some (40%) NIMA(d)-exposed mice accepted a DBA/2 allograft while others (60%) rejected in delayed fashion. Rejector and acceptor NIMA(d)-exposed mice had reduced T effector responses and increased Foxp3(+) T(R) cells (CD4(+)CD25(+)Foxp3(+) T(R)) in spleen and lymph nodes compared with controls. The key features distinguishing NIMA(d)-exposed acceptors from all other mice were: 1) higher frequency of IL-10- and TGF-beta-producing cells primarily in the CD4(+)CD25(+) T cell subset within lymph nodes and allografts, 2) a suppressed delayed-type hypersensitivity response to B6D2F1 Ags, and 3) allografts enriched in LAP(+), Foxp3(+), and CD4(+) T cells, with few CD8(+) T cells. We conclude that the beneficial NIMA effect is due to induction of NIMA-specific T(R) cells during ontogeny. Their persistence in the adult, and the ability of the host to mobilize them to the graft, may determine whether NIMA-specific tolerance is achieved. 相似文献
108.
Central nervous system regulation of mammalian hibernation: implications for metabolic suppression and ischemia tolerance 总被引:1,自引:0,他引:1
Drew KL Buck CL Barnes BM Christian SL Rasley BT Harris MB 《Journal of neurochemistry》2007,102(6):1713-1726
Torpor during hibernation defines the nadir of mammalian metabolism where whole animal rates of metabolism are decreased to as low as 2% of basal metabolic rate. This capacity to decrease profoundly the metabolic demand of organs and tissues has the potential to translate into novel therapies for the treatment of ischemia associated with stroke, cardiac arrest or trauma where delivery of oxygen and nutrients fails to meet demand. If metabolic demand could be arrested in a regulated way, cell and tissue injury could be attenuated. Metabolic suppression achieved during hibernation is regulated, in part, by the central nervous system through indirect and possibly direct means. In this study, we review recent evidence for mechanisms of central nervous system control of torpor in hibernating rodents including evidence of a permissive, hibernation protein complex, a role for A1 adenosine receptors, mu opiate receptors, glutamate and thyrotropin-releasing hormone. Central sites for regulation of torpor include the hippocampus, hypothalamus and nuclei of the autonomic nervous system. In addition, we discuss evidence that hibernation phenotypes can be translated to non-hibernating species by H(2)S and 3-iodothyronamine with the caveat that the hypothermia, bradycardia, and metabolic suppression induced by these compounds may or may not be identical to mechanisms employed in true hibernation. 相似文献
109.
The repeated Prisoner's Dilemma is usually known as a story of tit-for-tat (TFT). This remarkable strategy has won both of Robert Axelrod's tournaments. TFT does whatever the opponent has done in the previous round. It will cooperate if the opponent has cooperated, and it will defect if the opponent has defected. But TFT has two weaknesses: (i) it cannot correct mistakes (erroneous moves) and (ii) a population of TFT players is undermined by random drift when mutant strategies appear which play always-cooperate (ALLC). Another equally simple strategy called 'win-stay, lose-shift' (WSLS) has neither of these two disadvantages. WSLS repeats the previous move if the resulting payoff has met its aspiration level and changes otherwise. Here, we use a novel approach of stochastic evolutionary game dynamics in finite populations to study mutation-selection dynamics in the presence of erroneous moves. We compare four strategies: always-defect (ALLD), ALLC, TFT and WSLS. There are two possible outcomes: if the benefit of cooperation is below a critical value then ALLD is selected; if the benefit of cooperation is above this critical value then WSLS is selected. TFT is never selected in this evolutionary process, but lowers the selection threshold for WSLS. 相似文献
110.