全文获取类型
收费全文 | 5495篇 |
免费 | 705篇 |
国内免费 | 3篇 |
专业分类
6203篇 |
出版年
2021年 | 55篇 |
2019年 | 56篇 |
2018年 | 65篇 |
2017年 | 56篇 |
2016年 | 75篇 |
2015年 | 169篇 |
2014年 | 157篇 |
2013年 | 216篇 |
2012年 | 247篇 |
2011年 | 230篇 |
2010年 | 159篇 |
2009年 | 160篇 |
2008年 | 188篇 |
2007年 | 208篇 |
2006年 | 205篇 |
2005年 | 169篇 |
2004年 | 185篇 |
2003年 | 176篇 |
2002年 | 206篇 |
2001年 | 159篇 |
2000年 | 199篇 |
1999年 | 145篇 |
1998年 | 71篇 |
1997年 | 73篇 |
1996年 | 48篇 |
1995年 | 56篇 |
1994年 | 69篇 |
1993年 | 58篇 |
1992年 | 129篇 |
1991年 | 99篇 |
1990年 | 118篇 |
1989年 | 123篇 |
1988年 | 128篇 |
1987年 | 114篇 |
1986年 | 91篇 |
1985年 | 96篇 |
1984年 | 101篇 |
1983年 | 79篇 |
1982年 | 87篇 |
1981年 | 55篇 |
1979年 | 80篇 |
1978年 | 77篇 |
1977年 | 53篇 |
1976年 | 55篇 |
1975年 | 55篇 |
1974年 | 68篇 |
1973年 | 61篇 |
1972年 | 56篇 |
1970年 | 50篇 |
1968年 | 49篇 |
排序方式: 共有6203条查询结果,搜索用时 15 毫秒
991.
992.
993.
Ohara Chisato Sekiguchi Atsushi Takakura Shu Endo Yuka Tamura Naho Kikuchi Hiroe Maruo Kazushi Sugawara Norio Hatano Kenji Kawanishi Hitomi Funaba Misako Sugawara Ayako Nohara Nobuhiro Kawai Keisuke Fukudo Shin Sudo Nobuyuki Cooper Zafra Yoshiuchi Kazuhiro Ando Tetsuya 《BioPsychoSocial medicine》2020,14(1):1-3
Although fatigue is a common and distressing symptom in cancer survivors, the mechanism of fatigue is not fully understood. Therefore, this study aims to investigate the relation between the fatigue and mindfulness of breast cancer survivors using anxiety, depression, pain, loneliness, and sleep disturbance as mediators. Path analysis was performed to examine direct and indirect associations between mindfulness and fatigue. Participants were breast cancer survivors who visited a breast surgery department at a university hospital in Japan for hormonal therapy or regular check-ups after treatment. The questionnaire measured cancer-related-fatigue, mindfulness, anxiety, depression, pain, loneliness, and sleep disturbance. Demographic and clinical characteristics were collected from medical records. Two-hundred and seventy-nine breast cancer survivors were registered, of which 259 answered the questionnaire. Ten respondents with incomplete questionnaire data were excluded, resulting in 249 participants for the analyses. Our final model fit the data well (goodness of fit index = .993; adjusted goodness of fit index = .966; comparative fit index = .999; root mean square error of approximation = .016). Mindfulness, anxiety, depression, pain, loneliness, and sleep disturbance were related to fatigue, and mindfulness had the most influence on fatigue (β = − .52). Mindfulness affected fatigue not only directly but also indirectly through anxiety, depression, pain, loneliness, and sleep disturbance. The study model helps to explain the process by which mindfulness affects fatigue. Our results suggest that mindfulness has both direct and indirect effects on the fatigue of breast cancer survivors and that mindfulness can be used to more effectively reduce their fatigue. It also suggests that health care professionals should be aware of factors such as anxiety, depression, pain, loneliness, and sleep disturbance in their care for fatigue of breast cancer survivors. This study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN number. 000027720) on June 12, 2017. 相似文献
994.
David E. Andersen Wayne L. Brininger Thomas R. Cooper 《Journal of Field Ornithology》2015,86(4):345-351
American Woodcocks (Scolopax minor) are a high priority species of conservation need across most of their breeding range due to long‐term population declines. Survival of juveniles may be key to understanding these population declines, but there have been few direct estimates of juvenile woodcock survival rates, and no recent assessment of the possible effect of radio‐tagging on juvenile survival. In 2011 and 2012, we radio‐tagged 73 juvenile American Woodcocks in west‐central Minnesota and compared survival rates of radio‐tagged (N = 58) and non‐radio‐tagged (N = 82) juveniles during the period from hatching to fledging. We compared survival rates of juveniles with known fates and used logistic‐exposure models to assess the potential impact of radio‐transmitters on survival. We evaluated variables related to juvenile survival including age, hatch date, maximum and minimum temperature, precipitation, and year to assess the possible effects of radio‐transmitters. The best‐supported model of survival rate of juvenile American Woodcocks included the interaction of age and year and a negative effect of precipitation (β = ?0.76, 85% CI: ?1.08 to ?0.43), but did not include a negative effect of transmitters. Our results suggest that radio‐transmitters did not impact survival of juvenile American Woodcocks and that transmitters are a reliable tool for studying survival of juvenile American Woodcocks, and perhaps other precocial shorebirds. 相似文献
995.
Escape theory has been exceptionally successful in conceptualizing and accurately predicting effects of numerous factors that affect predation risk and explaining variation in flight initiation distance (FID; predator–prey distance when escape begins). Less explored is the relative orientation of an approaching predator, prey, and its eventual refuge. The relationship between an approaching threat and its refuge can be expressed as an angle we call the “interpath angle” or “Φ,” which describes the angle between the paths of predator and prey to the prey’s refuge and thus expresses the degree to which prey must run toward an approaching predator. In general, we might expect that prey would escape at greater distances if they must flee toward a predator to reach its burrow. The “race for life” model makes formal predictions about how Φ should affect FID. We evaluated the model by studying escape decisions in yellow-bellied marmots Marmota flaviventer, a species which flees to burrows. We found support for some of the model’s predictions, yet the relationship between Φ and FID was less clear. Marmots may not assess Φ in a continuous fashion; but we found that binning angle into 4 45° bins explained a similar amount of variation as models that analyzed angle continuously. Future studies of Φ, especially those that focus on how different species perceive relative orientation, will likely enhance our understanding of its importance in flight decisions. 相似文献
996.
A noncoding nuclear DNA marker sequence (Cpnl-1) was used to investigate subdivision in the grasshopper Chorthippus parallelus and deduce postglacial expansion patterns across its species range in Europe. Investigation of the spatial distribution of 71 Cpnl-1 haplotypes and estimation of levels of genetic differentiation (KST values) between populations and geographic regions provided evidence for subdivision of C. parallelus into at least five major geographic regions and indicated that the French form of C. parallelus originated after range expansion from a Balkan refugium, Further evidence for subdivision of C. parallelus between Italy and northern Europe suggests that the Alps may have formed a significant barrier to gene flow in this grasshopper. 相似文献
997.
Wound healing in the PU.1 null mouse--tissue repair is not dependent on inflammatory cells 总被引:11,自引:0,他引:11
Martin P D'Souza D Martin J Grose R Cooper L Maki R McKercher SR 《Current biology : CB》2003,13(13):1122-1128
Damage to neonatal and adult tissues always incites an influx of inflammatory neutrophils and macrophages. Besides clearing the wound of invading microbes, these cells are believed to be crucial coordinators of the repair process, acting both as professional phagocytes to clear wound debris and as a major source of wound growth factor signals. Here we report wound healing studies in the PU.1 null mouse, which is genetically incapable of raising the standard inflammatory response because it lacks macrophages and functioning neutrophils. Contrary to dogma, we show that these "macrophageless" mice are able to repair skin wounds with similar time course to wild-type siblings, and that repair appears scar-free as in the embryo, which also heals wounds without raising an inflammatory response. The growth factor and cytokine profile at the wound site is changed, cell death is reduced, and dying cells are instead engulfed by stand-in phagocytic fibroblasts. We also show that hyperinnervation of the wound site, previously believed to be a consequence of inflammation, is present in the PU.1 null wound, too. 相似文献
998.
DNA repeat expansions can result in the production of toxic RNA. RNA toxicity has been best characterised in the context of myotonic dystrophy. Nearly 20 mouse models have contributed significant and complementary insights into specific aspects of this novel disease mechanism. These models provide a unique resource to test pharmacological, anti-sense, and gene-therapy therapeutic strategies that target specific events of the pathobiological cascade. Further proof-of-principle concept studies and preclinical experiments require critical and thorough analysis of the multiple myotonic dystrophy transgenic lines available. This review provides in-depth assessment of the molecular and phenotypic features of these models and their contribution towards the dissection of disease mechanisms, and compares them with the human condition. More importantly, it provides critical assessment of their suitability and limitations for preclinical testing of emerging therapeutic strategies. 相似文献
999.
Bernadette Sánchez Kevin D. Pinkston Adina C. Cooper Carlos Luna Shelby T. Wyatt 《应用发育科学》2018,22(1):14-28
The aim of this study was to investigate the processes involved in developing close peer mentoring relationships among African American and Latino male adolescents in a school-based, group peer mentoring program. Qualitative one-on-one in-depth interviews were conducted with six school staff members, who administer the program, and 26 program participants about their experiences in the mentoring program. Data analysis revealed five program processes that led to close mentoring relationships: (a) rapport-building activities, (b) safe space, (c) mutual support, (d) group identity, and (e) trust. These processes ultimately led to bonding and friendship among program members, which further solidified the previous processes. Implications and future directions are discussed. 相似文献
1000.
Natural killer (NK) cells are innate immune lymphocytes capable of killing target cells and producing immunoregulatory cytokines. Herein, we discuss recent studies that indicate that NK cells span the conventional boundaries between innate and adaptive immunity. For example, it was recently discovered that NK cells have the capacity for memory‐like responses, a property that was previously thought to be limited to adaptive immunity. NK cells have also been identified in multiple tissues, and a subset of cells that specialize in the production of the TH17 cytokine IL‐22, NK‐22s, was recently described in mucosal‐associated lymphoid tissue. Finally, we review work that shows that NK cells develop at sites that were traditionally thought to be occupied only by adaptive immune cells, including the thymus and lymph nodes. 相似文献