全文获取类型
收费全文 | 551864篇 |
免费 | 56871篇 |
国内免费 | 395篇 |
出版年
2016年 | 5638篇 |
2015年 | 7208篇 |
2014年 | 8854篇 |
2013年 | 12722篇 |
2012年 | 14226篇 |
2011年 | 14766篇 |
2010年 | 10041篇 |
2009年 | 9332篇 |
2008年 | 13292篇 |
2007年 | 14020篇 |
2006年 | 13279篇 |
2005年 | 12777篇 |
2004年 | 12842篇 |
2003年 | 12367篇 |
2002年 | 12335篇 |
2001年 | 24868篇 |
2000年 | 25584篇 |
1999年 | 19875篇 |
1998年 | 6378篇 |
1997年 | 6637篇 |
1996年 | 6075篇 |
1995年 | 6016篇 |
1994年 | 5860篇 |
1993年 | 5929篇 |
1992年 | 16386篇 |
1991年 | 16231篇 |
1990年 | 15723篇 |
1989年 | 15368篇 |
1988年 | 14445篇 |
1987年 | 13765篇 |
1986年 | 12877篇 |
1985年 | 13145篇 |
1984年 | 10797篇 |
1983年 | 9232篇 |
1982年 | 7010篇 |
1981年 | 6436篇 |
1980年 | 6001篇 |
1979年 | 10427篇 |
1978年 | 8433篇 |
1977年 | 7658篇 |
1976年 | 7196篇 |
1975年 | 8263篇 |
1974年 | 9209篇 |
1973年 | 9098篇 |
1972年 | 8487篇 |
1971年 | 7665篇 |
1970年 | 6632篇 |
1969年 | 6523篇 |
1968年 | 6010篇 |
1967年 | 5197篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Detection and genotyping of group A rotaviruses isolated from sewage samples in Monastir,Tunisia between April 2007 and April 2010 下载免费PDF全文
3.
4.
Daniela Bellicoso Maureen Trudeau Margaret I. Fitch Martin R. Ralph 《Chronobiology international》2017,34(6):808-818
Primary caregivers for victims of chronic illness and or trauma experience both positive and negative emotional consequences. These are broadly classified as compassion satisfaction (CS) and compassion fatigue (CF). Because one of the components of CF, burnout, varies with chronotype and sleep quality, we assessed the influence of chronobiological features on the broader constructs of CS and CF. Responses from primary ambulatory care oncology staff working dayshifts were assessed for potential relationships of chronotype and sleep quality with CS and CF using the professional quality of life scale. These were analyzed further in a multivariate model that included personality and job satisfaction as cofactors. We found that sleep quality was a key contributor to CS development and CF reduction. Morningness was positively linked to CS, but the univariate association was masked in the multivariate model. Job satisfaction (contingent rewards, nature of work and operating procedures) heavily influenced CS and CF development. Agreeableness and openness showed positive correlations with CS and negative with burnout, while emotional stability was linked to reduced CF. While job satisfaction and personality predictably played roles in the development of CS and CF, sleep quality and chronotype contributed significantly to benefits and negative consequences of providing care. 相似文献
5.
6.
Effects of experimental warming on survival,phenology, and morphology of an aquatic insect (Odonata) 下载免费PDF全文
SHANNON J. MCCAULEY JOHN I. HAMMOND DACHIN N. FRANCES KAREN E. MABRY 《Ecological Entomology》2015,40(3):211-220
1. Organisms can respond to changing climatic conditions in multiple ways including changes in phenology, body size or morphology, and range shifts. Understanding how developmental temperatures affect insect life‐history timing and morphology is crucial because body size and morphology affect multiple aspects of life history, including dispersal ability, whereas phenology can shape population performance and community interactions. 2. It was experimentally assessed how developmental temperatures experienced by aquatic larvae affected survival, phenology, and adult morphology of dragonflies [Pachydiplax longipennis (Burmeister)]. Larvae were reared under three environmental temperatures: ambient, +2.5, and +5 °C, corresponding to temperature projections for our study area 50 and 100 years in the future, respectively. Experimental temperature treatments tracked naturally‐occurring variation. 3. Clear effects of temperature were found in the rearing environment on survival and phenology: dragonflies reared at the highest temperatures had the lowest survival rates and emerged from the larval stage approximately 3 weeks earlier than animals reared at ambient temperatures. There was no effect of rearing temperature on overall body size. Although neither the relative wing nor thorax size was affected by warming, a non‐significant trend towards an interaction between sex and warming in relative thorax size suggests that males may be more sensitive to warming than females, a pattern that should be investigated further. 4. Warming strongly affected survival in the larval stage and the phenology of adult emergence. Understanding how warming in the developmental environment affects later life‐history stages is critical to interpreting the consequences of warming for organismal performance. 相似文献
7.
Leaf phenology mediates provenance differences in herbivore populations on valley oaks in a common garden 下载免费PDF全文
IAN S. PEARSE JILL H. BATY DUSTIN HERRMANN RICHARD SAGE WALTER D. KOENIG 《Ecological Entomology》2015,40(5):525-531
1. Plants from different populations often display a variation in herbivore resistance. However, it is rarely understood what plant traits mediate such differences. 2. It was tested how leaf phenology affects herbivore populations in a 15‐year‐old common garden of valley oaks (Quercus lobata Née) with different populations and maternal parents from throughout the Q. lobata range. 3. The abundance of leaf miners (Stigmella sp. Shrank) and leaf phenology of oaks in the common garden was measured. 4. Leaf miner abundance varied among provenance locations (population), but not among maternal parents within populations. Leaf phenology varied by provenance location and maternal parent, and trees that leafed out earlier accrued higher leaf‐miner abundance. Path analysis indicated that leaf phenology was the likely driver of provenance and parental differences in resistance to leaf miners. 5. Understanding population differences is particularly important when considering transport of genotypes for ornamental or restoration purposes. The present study suggests that similarity in leaf phenology may be one factor that could be used to find genotypes with a similar herbivore resistance to local genotypes. 相似文献
8.
9.
10.
A. A. Minervina A. Y. Komkov I. Z. Mamedov Y. B. Lebedev 《Doklady. Biochemistry and biophysics》2016,467(1):85-88
T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignant neoplasm of the lymphocyte precursors that suffered malignant transformation arresting the lymphoid cell differentiation. Clinical studies revealed monoor, more rarely, oligoclonal nature of the disease. A precise identification of malignant clone markers is both the crucial stage of early diagnostics and the essential prognostic factor for therapeutic treatment. Here we present an improved system for unbiased detection of lymphoblastic clones in bone marrow aspirates of T-ALL patients. The system based on multiplex PCR of rearranged T-cell receptor locus (TRB) and straightforward sequencing of the resulted PCR fragments. Testing of the system on genomic DNA from Jurkat cell line and four clinical bone marrow aspirates revealed a set of unique TRB rearrangements that precisely characterize each of tested samples. Therefore, the outcome of the system produces highly informative molecular genetic markers for further monitoring of minimal residual disease in T-ALL patients. 相似文献