全文获取类型
收费全文 | 1937篇 |
免费 | 152篇 |
国内免费 | 171篇 |
出版年
2023年 | 44篇 |
2022年 | 48篇 |
2021年 | 57篇 |
2020年 | 62篇 |
2019年 | 101篇 |
2018年 | 77篇 |
2017年 | 67篇 |
2016年 | 83篇 |
2015年 | 58篇 |
2014年 | 93篇 |
2013年 | 107篇 |
2012年 | 68篇 |
2011年 | 67篇 |
2010年 | 61篇 |
2009年 | 105篇 |
2008年 | 109篇 |
2007年 | 116篇 |
2006年 | 100篇 |
2005年 | 70篇 |
2004年 | 70篇 |
2003年 | 77篇 |
2002年 | 77篇 |
2001年 | 53篇 |
2000年 | 42篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 30篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 35篇 |
1992年 | 20篇 |
1991年 | 32篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 2篇 |
1974年 | 3篇 |
排序方式: 共有2260条查询结果,搜索用时 15 毫秒
81.
Papillary renal cell carcinoma (pRCC) is a heterogeneous disease containing multifocal or solitary tumors with an aggressive phenotype. Increasing evidence has indicated the involvement of aberrant splicing variants in renal cell cancer, while systematic profiling of aberrant alternative splicing (AS) in pRCC was lacking and largely unknown. In the current study, comprehensive profiling of AS events were performed based on the integration of pRCC cohort from the Cancer Genome Atlas database and SpliceSeq software. With rigorous screening and univariate Cox analysis, a total of 2077 prognoses AS events from 1642 parent genes were identified. Then, stepwise least absolute shrinkage and selection operator method-penalized Cox regression analyses with 10-fold cross-validation followed by multivariate Cox regression were used to construct the prognostic AS signatures within each AS type. And a final 21 AS event-based signature was proposed which showed potent prognostic capability in stratifying patients into low- and high-risk subgroups (P < .0001). Furthermore, time-dependent receiver operating characteristics curves confirmed that the final AS signature was effective and robust in predicting overall survival for pRCC patients with the area under the curve above 0.9 from 1 to 5 years. In addition, splicing correlation network was built to uncover the potential regulatory pattern among prognostic splicing factors and candidate AS events. Besides, gene set enrichment analysis revealed the involvement of these candidates AS events in tumor-related pathways including extracellular matrix organization, oxidative phosphorylation, and P53 signaling pathways. Taken together, our results could contribute to elucidating the underlying mechanism of AS in the oncogenesis process and broaden the novel field of prognostic and clinical application of molecule-targeted approaches in pRCC. 相似文献
82.
83.
《Critical reviews in biotechnology》2013,33(4):382-400
Agricultural and food-industry residues constitute a major proportion (almost 30%) of worldwide agricultural production. These wastes mainly comprise lignocellulosic materials, fruit and vegetable wastes, sugar-industry wastes as well as animal and fisheries refuse and byproducts. Agro-residues are rich in many bioactive and nutraceutical compounds, such as polyphenolics, carotenoids and dietary fiber among others. Agro residues are a major valuable biomass and present potential solutions to problems of animal nutrition and the worldwide supply of protein and calories, if appropriate technologies can be used for their valorization by nutrient enrichment. Technologies available for protein enrichment of these wastes include solid substrate fermentation, ensiling, and high solid or slurry processes. Technologies to be developed for the reprocessing of these wastes need to take account of the peculiarities of individual wastes and the environment in which they are generated, reprocessed, and used. In particular, such technologies need to deliver products that are safe, not just for animal feed use, but also from the perspective of human feeding. This review focuses on the major current applications of solid-state fermentation in relation to the feed sector. 相似文献
84.
85.
Tycho Walaardt 《Ethnic and racial studies》2013,36(7):1199-1218
Abstract In 1975, the first Christian Turks applied for asylum in the Netherlands. They were at first denied, and only in the early 1980s did they finally begin to win refugee status from the Dutch government. In the meantime, they faced years of uncertainty. Campaigns of lobbyists in the years between 1977 and 1983 contributed to end their waiting. Their campaigns caused a drastic change of the image of the ‘deserving refugee’ in the Netherlands. This article explores the arguments that lobbyists used to influence decision-makers. It shows how and why the public and political image of the ‘deserving refugee’ had to change in order to successfully claim refugee status. 相似文献
86.
María de los Angeles Ribas Antúnez Blanca Girón Iraima Monsalvez Luis Morier Gretel Acosta Yahisel Tejero Yanislet Cordero Dainelyd Piedra 《Memórias do Instituto Oswaldo Cruz》2013,108(2):255-256
Rabies is a neurotropic disease that is often lethal. The early diagnosis of rabies infection is important and requires methods that allow for the isolation of the virus from animals and humans. The present study compared a modified shell vial (MSV) procedure using 24-well tissue culture plates with the mouse inoculation test (MIT), which is considered the gold standard for rabies virus isolation. Thirty brain samples (25 positive and 5 negative by the fluorescent antibody test) obtained from different animal species at the National Institute of Hygiene Rafael Rangel in Caracas, Venezuela, were studied by the MIT and MSV assays. Nine samples (36%) were positive at 24 h, 10 (40%) were positive at 48 h and six (24%) were positive at 72 h by the MSV assay. With the MIT assay, 76% were positive at six days post inoculation and 12% were positive at 12 and 18 days post inoculation. One sample that was negative according to the MSV assay was positive with MIT on the 12th day. The MSV procedure exhibited a sensitivity of 96.2%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value 80%. This procedure allowed for rapid rabies virus detection. MIT can be employed as an alternative method in laboratories without tissue culture facilities. 相似文献
87.
ROBERT C. JOHNSON HWA‐SEONG JIN MARGARET M. CARREIRO JEFFREY D. JACK 《Freshwater Biology》2013,58(5):843-857
1. Despite non‐point‐source (NPS) pollution being perhaps the most ubiquitous stressor affecting urban streams, there is a lack of research assessing how urban NPS pollution affects stream ecosystems. We used a natural experimental design approach to assess how stream macroinvertebrate community structure, secondary production and trophic structure are influenced by urban NPS pollution in six streams. 2. Differences in macroinvertebrate community structure and secondary production among sites were highly correlated with stream‐water specific conductivity and dissolved inorganic phosphorus (DIP) concentrations. Macroinvertebrate richness, the Shannon diversity index and the Shannon evenness index were all negatively correlated with specific conductivity. These patterns were driven by differences in the richness and production of EPT and other intolerant taxa. Production of the five most productive taxa, tolerant taxa, non‐insect taxa and primary consumers were all positively correlated with stream‐water DIP. 3. Despite the positive correlation between primary consumer production and DIP, there was no correlation between macroinvertebrate predator production and either total or primary consumer macroinvertebrate production. This was observed because DIP was positively correlated with the production of non‐insect macroinvertebrate taxa assumed to be relatively unavailable for macroinvertebrate predator consumption. After removing production of these taxa, we observed a strong positive correlation between macroinvertebrate predator production and production of available prey. 4. Our results suggest that urban NPS pollution not only affects macroinvertebrate community structure, but also alters secondary production and trophic‐level dynamics. Differences in taxon production in our study indicate the potential for altered energy flow through stream food webs and potential effects on subsidies of aquatic insect prey to riparian food webs. 相似文献
88.
Anne Gro Vea Salvanes Olav Moberg Lars O. E. Ebbesson Tom Ole Nilsen Knut Helge Jensen Victoria A. Braithwaite 《Proceedings. Biological sciences / The Royal Society》2013,280(1767)
Different kinds of experience during early life can play a significant role in the development of an animal''s behavioural phenotype. In natural contexts, this influences behaviours from anti-predator responses to navigation abilities. By contrast, for animals reared in captive environments, the homogeneous nature of their experience tends to reduce behavioural flexibility. Studies with cage-reared rodents indicate that captivity often compromises neural development and neural plasticity. Such neural and behavioural deficits can be problematic if captive-bred animals are being reared with the intention of releasing them as part of a conservation strategy. Over the last decade, there has been growing interest in the use of environmental enrichment to promote behavioural flexibility in animals that are bred for release. Here, we describe the positive effects of environmental enrichment on neural plasticity and cognition in juvenile Atlantic salmon (Salmo salar). Exposing fish to enriched conditions upregulated the forebrain expression of NeuroD1 mRNA and improved learning ability assessed in a spatial task. The addition of enrichment to the captive environment thus promotes neural and behavioural changes that are likely to promote behavioural flexibility and improve post-release survival. 相似文献
89.
90.
通过顶置光源植物生长室控制380和760 μmol·mol-1 2个CO2浓度水平,研究了磷缺乏与正常供磷条件下,CO2浓度升高对玉米/大豆间作、玉米单作和大豆单作3种种植模式下作物株高、茎粗、叶面积及干物质积累的影响.结果表明:(1)CO2浓度升高能显著增加单/间作玉米、大豆的株高、茎粗、叶面积、根干重、地上部干重及总干重.(2)CO2浓度升高对供磷水平下单、间作玉米大豆的株高、茎粗、叶面积及干物质积累量增加的正效应均大于缺磷处理.(3)两种CO2浓度下,间作大豆与单作大豆生长差异不显著,而间作玉米较单作玉米有明显的生长优势,且供磷和CO2浓度的升高均能够促进这种优势. 相似文献