全文获取类型
收费全文 | 35071篇 |
免费 | 2871篇 |
国内免费 | 1898篇 |
专业分类
39840篇 |
出版年
2024年 | 68篇 |
2023年 | 389篇 |
2022年 | 934篇 |
2021年 | 1634篇 |
2020年 | 1041篇 |
2019年 | 1250篇 |
2018年 | 1232篇 |
2017年 | 867篇 |
2016年 | 1325篇 |
2015年 | 2026篇 |
2014年 | 2373篇 |
2013年 | 2551篇 |
2012年 | 3090篇 |
2011年 | 2775篇 |
2010年 | 1729篇 |
2009年 | 1437篇 |
2008年 | 1671篇 |
2007年 | 1525篇 |
2006年 | 1353篇 |
2005年 | 1144篇 |
2004年 | 1023篇 |
2003年 | 870篇 |
2002年 | 746篇 |
2001年 | 678篇 |
2000年 | 686篇 |
1999年 | 655篇 |
1998年 | 388篇 |
1997年 | 336篇 |
1996年 | 360篇 |
1995年 | 334篇 |
1994年 | 326篇 |
1993年 | 218篇 |
1992年 | 352篇 |
1991年 | 272篇 |
1990年 | 306篇 |
1989年 | 257篇 |
1988年 | 191篇 |
1987年 | 176篇 |
1986年 | 152篇 |
1985年 | 135篇 |
1984年 | 123篇 |
1983年 | 95篇 |
1982年 | 77篇 |
1981年 | 61篇 |
1979年 | 75篇 |
1978年 | 55篇 |
1977年 | 53篇 |
1975年 | 59篇 |
1974年 | 47篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Self‐Assembled BiFeO3‐ε‐Fe2O3 Vertical Heteroepitaxy for Visible Light Photoelectrochemistry 下载免费PDF全文
Le Thi Quynh Chien Nguyen Van Yugandhar Bitla Jhih‐Wei Chen Thi Hien Do Wen‐Yen Tzeng Sheng‐Chieh Liao Kai‐An Tsai Yi‐Chun Chen Chun‐Lin Wu Chih‐Huang Lai Chih‐Wei Luo Yung‐Jung Hsu Ying‐Hao Chu 《Liver Transplantation》2016,6(18)
Self‐assembled vertical heterostructure with a high interface‐to‐volume ratio offers tremendous opportunities to realize intriguing properties and advanced modulation of functionalities. Here, a heterostructure composed of two visible‐light photocatalysts, BiFeO3 (BFO) and ε‐Fe2O3 (ε‐FO), is designed to investigate its photoelectrochemical performance. The structural characterization of the BFO‐FO heterostructures confirms the phase separation with BFO nanopillars embedded in the ε‐FO matrix. The investigation of band structure of the heterojunction suggests the assistance of photoexcited carrier separation, leading to an enhanced photoelectrochemical performance. The insights into the charge separation are further revealed by means of ultrafast dynamics and electrochemical impedance spectroscopies. This work shows a delicate design of the self‐assembled vertical heteroepitaxy by taking advantage of the intimate contact between two phases that can lead to a tunable charge interaction, providing a new configuration for the optimization of photoelectrochemical cell. 相似文献
992.
Liang Huang Qinhong Wang Sijing Jiang Yuling Zhou Guimin Zhang Yanhe Ma 《Bioprocess and biosystems engineering》2016,39(11):1679-1687
Chitosanase (CSN) from Aspergillus fumigatus has good thermal stability, wide pH range duration, and effective hydrolysis for chitosan. Inhere, CSN was successfully expressed in Escherichia coli followed by extracellular secretion under the guidance of an N-terminal signal peptide PelB, which effectively prompted its secretion out of E. coli cells. To facilitate its later purification, N-terminal or C-terminal 6xHis epitope tag was added to the PelB-CSN protein complex. Our results indicated that PelB-CSN without 6xHis-tag (PelB-CSN) or with N-terminal 6xHis-tag (PelB-CSN-N) can both be effectively secreted into the medium, while CSN with 6xHis-tag anchored at C-terminus was expressed as inclusion bodies. Process optimization strategies were further developed to improve the secretion efficiency of recombinant PelB-CSN-N in E. coli. Under the induction of 10 g/L lactose in shake-flask culture, the extracellular activity of CSN reached 6015 U/mL at 25 °C in TB medium containing 1 % glycine. Moreover, a fed-batch fermentation strategy for high-cell-density cultivation was applied in a 5-L fermenter, increasing the extracellular CSN activity to 14,000 U/mL in 2-day fermentation with the optimal addition of lactose and glycine. 相似文献
993.
Andreas Schmideder Xenia Priebe Mark Rubenbauer Thomas Hoffmann Fong-Chin Huang Wilfried Schwab Dirk Weuster-Botz 《Bioprocess and biosystems engineering》2016,39(9):1409-1414
Whole cells of Escherichia coli overexpressing a glucosyltransferase from Vitis vinifera were used for the glucosylation of geraniol to geranyl glucoside. A high cell density cultivation process for the production of whole-cell biocatalysts was developed, gaining a dry cell mass concentration of up to 67.6 ± 1.2 g L?1 and a glucosyltransferase concentration of up to 2.7 ± 0.1 g protein L?1 within a process time of 48 h. Whole-cell batch biotransformations in milliliter-scale stirred-tank bioreactors showed highest conversion of geraniol at pH 7.0 although the pH optimum of the purified glucosyltransferase was at pH 8.5. The biocatalytic batch process performance was improved significantly by the addition of a water-immiscible ionic liquid (N-hexylpyridinium bis(trifluoromethylsulfonyl)imid) for in situ substrate supply. The so far highest final geranyl glucoside concentration (291 ± 9 mg L?1) and conversion (71 ± 2 %) reported for whole-cell biotransformations of geraniol were achieved with 5 % (v/v) of the ionic liquid. 相似文献
994.
995.
Skin aging caused by intrinsic or extrinsic processes characterized with functional proteomics 下载免费PDF全文
Jia‐You Fang Pei‐Wen Wang Chun‐Hsun Huang Mu‐Hong Chen Yun‐Ru Wu Tai‐Long Pan 《Proteomics》2016,16(20):2718-2731
The skin provides protection against environmental stress. However, intrinsic and extrinsic aging causes significant alteration to skin structure and components, which subsequently impairs molecular characteristics and biochemical processes. Here, we have conducted an immunohistological investigation and established the proteome profiles on nude mice skin to verify the specific responses during aging caused by different factors. Our results showed that UVB‐elicited aging results in upregulation of proliferating cell nuclear antigen and strong oxidative damage in DNA, whereas chronological aging abolished epidermal cell growth and increased the expression of caspase‐14, as well as protein carbonylation. Network analysis indicated that the programmed skin aging activated the ubiquitin system and triggered obvious downregulation of 14‐3‐3 sigma, which might accelerate the loss of cell growth capacity. On the other hand, UVB stimulation enhanced inflammation and the risk of skin carcinogenesis. Collectively, functional proteomics could provide large‐scale investigation of the potent proteins and molecules that play important roles in skin subjected to both intrinsic and extrinsic aging. 相似文献
996.
Jiandong Zheng Xixiang Huo Yang Huai Lin Xiao Hui Jiang John Klena Carolyn M. Greene Xuesen Xing Jigui Huang Shali Liu Youxing Peng Hui Yang Jun Luo Zhibin Peng Linlin Liu Maoyi Chen Hui Chen Yuzhi Zhang Danqin Huang Xuhua Guan Luzhao Feng Faxian Zhan Dale J. Hu Jay K. Varma Hongjie Yu 《PloS one》2016,11(3)
997.
Chu-Chih Chen Shu-Li Wang Ming-Tsang Wu Yin-Han Wang Po-Chin Huang Bai-Hsiun Chen Chien-Wen Sun Chi-Kung Ho Yang-Chih Shih Ming-Neng Shiu Wen-Harn Pan Mei-Lien Chen Ching-Chang Lee Chao A. Hsiung 《PloS one》2016,11(3)
Background
In May 2011, di(2-ethylhexyl) phthalates (DEHP) and, to a lesser extent, di-iso-nonyl phthalate (DiNP) were found to have been illegally used for many years in Taiwan as clouding agents in foods including sports drinks, juice beverages, tea drinks, fruit jam/nectar/jelly, and health or nutrient supplements.Objective
To estimate the DEHP exposure for the study participants for the follow-up epidemiological study and health risk assessment.Methods
A total of 347 individuals possibly highly exposed to phthalate-tainted foods participated in the study. Exposure assessment was performed based on the participants'' responses to a structured questionnaire, self-report of exposure history, urinary metabolite concentrations, and DEHP concentration information in 2449 food records. A Bayesian statistical approach using Markov chain Monte Carlo simulation was employed to deal with the uncertainties in the DEHP concentrations of the contaminated foods and the participants'' likelihood of being exposed.Results
An estimated 37% and 15% of children younger than 12 years old were exposed to DEHP at medium (20–50 μg / kg_bw / day) and high AvDIs (50–100 μg / kg_bw / day), respectively, prior to the episode (9% and 3% in adults, respectively). Moreover, 11% of children and 1% of adults were highly exposed (> 100 μg / kg_bw / day), with a maximum of 414.1 μg / kg_bw / day and 126.4 μg / kg_bw / day, respectively.Conclusions
The phthalate exposure-associated adverse health effects for these participants warrant further investigation. The estimation procedure may be applied to other exposure assessment with various sources of uncertainties. 相似文献998.
Lan-Lan Wang Xin-Ru Wang Xue-Mei Wei Huang Huang Jian-Xiang Wu Xue-Xin Chen 《Autophagy》2016,12(9):1560-1574
Macroautophagy/autophagy plays an important role against pathogen infection in mammals and plants. However, little has been known about the role of autophagy in the interactions of insect vectors with the plant viruses, which they transmit. Begomoviruses are a group of single-stranded DNA viruses and are exclusively transmitted by the whitefly Bemisia tabaci in a circulative manner. In this study, we found that the infection of a begomovirus, tomato yellow leaf curl virus (TYLCV) could activate the autophagy pathway in the Middle East Asia Minor 1 (MEAM1) species of the B. tabaci complex as evidenced by the formation of autophagosomes and ATG8-II. Interestingly, the activation of autophagy led to the subsequent degradation of TYLCV coat protein (CP) and genomic DNA. While feeding the whitefly with 2 autophagy inhibitors (3-methyladenine and bafilomycin A1) and silencing the expression of Atg3 and Atg9 increased the viral load; autophagy activation via feeding of rapamycin notably decreased the amount of viral CP and DNA in the whitefly. Furthermore, we found that activation of whitefly autophagy could inhibit the efficiency of virus transmission; whereas inhibiting autophagy facilitated virus transmission. Taken together, these results indicate that TYLCV infection can activate the whitefly autophagy pathway, which leads to the subsequent degradation of virus. Furthermore, our report proves that an insect vector uses autophagy as an intrinsic antiviral program to repress the infection of a circulative-transmitted plant virus. Our data also demonstrate that TYLCV may replicate and trigger complex interactions with the insect vector. 相似文献
999.
1000.