全文获取类型
收费全文 | 9160篇 |
免费 | 666篇 |
国内免费 | 8篇 |
专业分类
9834篇 |
出版年
2024年 | 12篇 |
2023年 | 42篇 |
2022年 | 108篇 |
2021年 | 179篇 |
2020年 | 127篇 |
2019年 | 180篇 |
2018年 | 261篇 |
2017年 | 242篇 |
2016年 | 357篇 |
2015年 | 561篇 |
2014年 | 603篇 |
2013年 | 635篇 |
2012年 | 864篇 |
2011年 | 817篇 |
2010年 | 489篇 |
2009年 | 417篇 |
2008年 | 590篇 |
2007年 | 553篇 |
2006年 | 468篇 |
2005年 | 408篇 |
2004年 | 476篇 |
2003年 | 378篇 |
2002年 | 333篇 |
2001年 | 120篇 |
2000年 | 121篇 |
1999年 | 94篇 |
1998年 | 69篇 |
1997年 | 46篇 |
1996年 | 36篇 |
1995年 | 26篇 |
1994年 | 27篇 |
1993年 | 15篇 |
1992年 | 31篇 |
1991年 | 25篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1973年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有9834条查询结果,搜索用时 15 毫秒
51.
Dong Hoon Shin Gyeong Im Yu Jae Seok Hwang Eun Soo Kim Jong Won Yun 《Proteomics》2013,13(15):2361-2374
In the present study, we screened proteomic and cytokine biomarkers between patients with adenomatous polyps and colorectal cancer (CRC) in order to improve our understanding of the molecular mechanisms behind turmorigenesis and tumor progression in CRC. To this end, we performed comparative proteomic analysis of plasma proteins using a combination of 2DE and MS as well as profiled differentially regulated cytokines and chemokines by multiplex bead analysis. Proteomic analysis identified 11 upregulated and 13 downregulated plasma proteins showing significantly different regulation patterns with diagnostic potential for predicting progression from adenoma to carcinoma. Some of these proteins have not previously been implicated in CRC, including upregulated leucine‐rich α‐2‐glycoprotein, hemoglobin subunit β, Ig α‐2 chain C region, and complement factor B as well as downregulated afamin, zinc‐α‐2‐glycoprotein, vitronectin, and α‐1‐antichymotrypsin. In addition, plasma levels of three cytokines/chemokines, including interleukin‐8, interferon gamma‐induced protein 10, and tumor necrosis factor α, were remarkably elevated in patients with CRC compared to those with adenomatous polyps. Although further clinical validation is required, these proteins and cytokines can be established as novel biomarkers for CRC and/or its progression from colon adenoma. 相似文献
52.
Young-Hoon Park Mi Suk Jeong Hyun Ho Park Se Bok Jang 《Biochimica et Biophysica Acta - Proteins and Proteomics》2013,1834(1):292-300
Fas-associated death domain (FADD) protein is an adapter molecule that bridges the interactions between membrane death receptors and initiator caspases. The death receptors contain an intracellular death domain (DD) which is essential to the transduction of the apoptotic signal. The kinase receptor-interacting protein 1 (RIP1) is crucial to programmed necrosis. The cell type interplay between FADD and RIP1, which mediates both necrosis and NF-κB activation, has been evaluated in other studies, but the mechanism of the interaction of the FADD and RIP1 proteins remain poorly understood. Here, we provided evidence indicating that the DD of human FADD binds to the DD of RIP1 in vitro. We developed a molecular docking model using homology modeling based on the structures of FADD and RIP1. In addition, we found that two structure-based mutants (G109A and R114A) of the FADD DD were able to bind to the RIP1 DD, and two mutations (Q169A and N171A) of FADD DD and four mutations (G595, K596, E620, and D622) of RIP1 DD disrupted the FADD–RIP1 interaction. Six mutations (Q169A, N171A, G595, K596, E620, and D622) lowered the stability of the FADD–RIP1 complex and induced aggregation that structurally destabilized the complex, thus disrupting the interaction. 相似文献
53.
Yuwon Park Nam‐Soon Choi Sangjin Park Seung Hee Woo Soojin Sim Bo Yun Jang Seung M. Oh Soojin Park Jaephil Cho Kyu Tae Lee 《Liver Transplantation》2013,3(2):206-212
Remarkable improvements in the electrochemical performance of Si materials for Li‐ion batteries have been recently achieved, but the inherent volume change of Si still induces electrode expansion and external cell deformation. Here, the void structure in Si‐encapsulating hollow carbons is optimized in order to minimize the volume expansion of Si‐based anodes and improve electrochemical performance. When compared to chemical etching, the hollow structure is achieved via electroless etching is more advanced due to the improved electrical contact between carbon and Si. Despite the very thick electrodes (30 ~ 40 μm), this results in better cycle and rate performances including little capacity fading over 50 cycles and 1100 mA h g?1 at 2C rate. Also, an in situ dilatometer technique is used to perform a comprehensive study of electrode thickness change, and Si‐encapsulating hollow carbon mitigates the volume change of electrodes by adoption of void space, resulting in a small volume increase of 18% after full lithiation corresponding with a reversible capacity of about 2000 mA h g?1. 相似文献
54.
In-Gyun Lee Sun-Bok Jang Ji-Hun Kim Ki-Young Lee Kyu-Yeon Lee Hae-Kap Cheong Bong-Jin Lee 《Biomolecular NMR assignments》2013,7(2):159-162
Cell adhesion molecules play a crucial role in fundamental biological processes via regulating cell–cell interactions. Nerve injury induced protein1 (Ninjurin1) is a novel adhesion protein that has no significant homology with other known cell adhesion molecules. Here we present the assignment of an 81 aa construct for human Ninjurin1 Extracellular N-Terminal (ENT) domain, which comprises the critical adhesion domain. 相似文献
55.
Jung Hyun Yoon Kyung Hwa Han Eun-Kyung Kim Hee Jung Moon Min Jung Kim Young Joo Suh Ji Soo Choi Byeong-Woo Park 《PloS one》2013,8(2)
Introduction
To assess whether the value of CYFRA21-1 in the aspirates of ultrasonography-guided fine-needle aspiration biopsy (US-FNAB) can contribute to improving the performances of US-FNAB in the diagnosis of axillary lymph node (LN) metastasis in breast cancer patients.Methods
US-FNAB was performed in 156 axillary LNs in 152 breast cancer patients (mean age: 51.4 years, range: 17–92 years). Concentrations of CYFRA21-1 were measured from washouts of the syringe used during US-FNAB. Tumor marker concentrations, US-FNAB, intraoperative sentinel node biopsy (SNB), and surgical pathology results were reviewed and analyzed. For comparison, the values of CEA and CA15-3 were also measured from washouts.Results
Among the 156 LNs, 75 (48.1%) were benign, and 81 (51.9%) were metastases. Mean concentrations of CYFRA21-1 were significantly higher in metastasis compared to benign LNs (P<0.001). US-FNAB combined to CYFRA21-1 showed significantly higher sensitivity, NPV, and accuracy compared to US-FNAB alone (all values P<0.05). All diagnostic indices of US-FNAB combined to CYFRA21-1 were significantly higher compared to US-FNAB combined with CEA or CA15-3 (all P<0.001). Of the 28 metastatic LNs which showed metastasis on SNB, CYFRA21-1 showed higher positive rate of 75.0% (CEA or CA15-3∶60.7%, P = 0.076).Conclusion
Measuring CYFRA 21-1 concentrations from US-FNAB aspirates improves sensitivity, NPV, and accuracy of US-FNAB alone, and may contribute to reducing up to 75.0% of unnecessary intraoperative SNB. Compared to CEA or CA15-3, CYFRA21-1 shows significantly higher performances when combined to US-FNAB in the preoperative diagnosis of LN metastasis in breast cancer patients. 相似文献56.
Alexander Chi Pan Ma Guishan Fu Gerry Hobbs James S. Welsh Nam P. Nguyen Si Young Jang Jinrong Dai Jing Jin Ritsuko Komaki 《PloS one》2013,8(4)
Background
Helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) are both advanced techniques of delivering intensity-modulated radiotherapy (IMRT). Here, we conduct a study to compare HT and partial-arc VMAT in their ability to spare organs at risk (OARs) when stereotactic ablative radiotherapy (SABR) is delivered to treat centrally located early stage non-small-cell lung cancer or lung metastases.Methods
12 patients with centrally located lung lesions were randomly chosen. HT, 2 & 8 arc (Smart Arc, Pinnacle v9.0) plans were generated to deliver 70 Gy in 10 fractions to the planning target volume (PTV). Target and OAR dose parameters were compared. Each technique’s ability to meet dose constraints was further investigated.Results
HT and VMAT plans generated essentially equivalent PTV coverage and dose conformality indices, while a trend for improved dose homogeneity by increasing from 2 to 8 arcs was observed with VMAT. Increasing the number of arcs with VMAT also led to some improvement in OAR sparing. After normalizing to OAR dose constraints, HT was found to be superior to 2 or 8-arc VMAT for optimal OAR sparing (meeting all the dose constraints) (p = 0.0004). All dose constraints were met in HT plans. Increasing from 2 to 8 arcs could not help achieve optimal OAR sparing for 4 patients. 2/4 of them had 3 immediately adjacent structures.Conclusion
HT appears to be superior to VMAT in OAR sparing mainly in cases which require conformal dose avoidance of multiple immediately adjacent OARs. For such cases, increasing the number of arcs in VMAT cannot significantly improve OAR sparing. 相似文献57.
Influenza epidemics arise through the accumulation of viral genetic changes. The emergence of new virus strains coincides with a higher level of influenza-like illness (ILI), which is seen as a peak of a normal season. Monitoring the spread of an epidemic influenza in populations is a difficult and important task. Twitter is a free social networking service whose messages can improve the accuracy of forecasting models by providing early warnings of influenza outbreaks. In this study, we have examined the use of information embedded in the Hangeul Twitter stream to detect rapidly evolving public awareness or concern with respect to influenza transmission and developed regression models that can track levels of actual disease activity and predict influenza epidemics in the real world. Our prediction model using a delay mode provides not only a real-time assessment of the current influenza epidemic activity but also a significant improvement in prediction performance at the initial phase of ILI peak when prediction is of most importance. 相似文献
58.
Jan F. Kamler Khamtai Thatdokkham Susana Rostro-García Anita Bousa Anthony Caragiulo Rachel Crouthers Visattha In Chen Pay Chanratana Pin Sovanna Prum Chantavy Vongkhamheng Arlyne Johnson David W. Macdonald 《The Journal of wildlife management》2020,84(7):1396-1405
Endangered dholes (Cuon alpinus) are restricted to small and declining populations in Southeast Asia, and little is known about how their ecology differs within the region. We used DNA-confirmed scats and prey surveys to determine the seasonal diet and prey selection of dholes in 2 different landscapes that dominate Southeast Asia: closed evergreen forests in hilly terrain in northern Laos, and open deciduous forests in relatively flat terrain in eastern Cambodia. On both sites, muntjac (Muntiacus spp.; 20–28 kg) was the dominant prey item and was selectively consumed over other ungulates in all seasons. Our findings differ from previous conclusions, based largely on studies from India, that the preferred prey weight range of dholes was either 40–60 kg or 130–190 kg. Other important prey were sambar (Rusa unicolor) in Laos, and wild pig (Sus scrofa) and banteng (Bos javanicus) in Cambodia. Seasonal differences in overall diet occurred in Laos, but not Cambodia, primarily because of an increase in livestock consumption. The mean number of dhole scats in group defecation sites was higher in Cambodia (5.9 ± 0.5 [SE]) than Laos (2.4 ± 0.2), suggesting pack sizes were larger in Cambodia. Our results suggest that regardless of land cover type, prey diversity, or pack size, the management of muntjac will be important for conserving dhole populations in Southeast Asia. In Laos, we recommend that local villagers remove livestock from the protected area during the hot-dry season to reduce livestock predation by dholes. © 2020 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society. 相似文献
59.
60.
Samanta Iop Tiago Gomes dos Santos Sonia Zanini Cechin Eduardo Vélez-Martin Valério D. Pillar Paulo Inácio Prado 《Biotropica》2020,52(5):913-926
We investigated the role of local and landscape environmental variables on anurans density classified as habitat specialists and generalists in grassland landscapes, known as South Brazilian grasslands (SBG). In this region, we surveyed 187 ponds distributed over 40 landscape sampling units. For each pond, 31 local environmental variables were measured. Each landscape sampling unit was embedded within a larger regional sampling unit with different landscape properties. For each landscape and regional sampling units, 16 landscape metrics were extracted from a land cover and use map. We recorded 35 species, eleven of which are specialists in the SBG. The specialists were affected by 11 local and 2 landscape environmental variables, while generalists were affected by 14 local and one landscape environmental variable. Thus, specialists and generalists presented different relationships with local and landscape variables, but in general local variables had a greater influence on the density of anurans than the landscape variables. However, the landscape indirectly influenced local variables because higher quality ponds were in landscapes with higher percentages of natural habitat. In conclusion, reproductive sites with higher local quality and located within landscapes with higher percentages of natural grasslands are essential to conserve anurans in this habitat. Effective conservation of such sites would benefit from further studies that assess effects of land use and biotic integrity of ponds, which can help to determine (a) the relative effects of local habitat quality of ponds and (b) the effectiveness of protecting ponds and their local surroundings for anuran conservation in SBG. Abstract in Portuguese is available with online material. 相似文献