全文获取类型
收费全文 | 2854篇 |
免费 | 212篇 |
国内免费 | 5篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 36篇 |
2021年 | 72篇 |
2020年 | 52篇 |
2019年 | 83篇 |
2018年 | 107篇 |
2017年 | 80篇 |
2016年 | 121篇 |
2015年 | 191篇 |
2014年 | 186篇 |
2013年 | 225篇 |
2012年 | 264篇 |
2011年 | 229篇 |
2010年 | 161篇 |
2009年 | 148篇 |
2008年 | 197篇 |
2007年 | 175篇 |
2006年 | 133篇 |
2005年 | 114篇 |
2004年 | 110篇 |
2003年 | 104篇 |
2002年 | 72篇 |
2001年 | 34篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 5篇 |
1994年 | 14篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有3071条查询结果,搜索用时 140 毫秒
31.
Hee Kyoung Kang Jung Han Suh Jung Jin Lee Sun Hee Yoon Jin Won Hyun Seong Won Choi 《Free radical research》2013,47(7):773-779
The present study was undertaken to examine the effect of l-ascorbic acid (LAA) on the growth of HL-60 promyelocytic leukemia cells, besides induction of apoptosis. LAA (≥10-4?M) was found to markedly inhibit the proliferation of HL-60 in liquid culture and clonogenicity in semisolid culture. Moreover, LAA-treated HL-60 showed activity to produce chemiluminescence and expressed CD 66b cell surface antigens, indicating that LAA induces the differentiation of HL-60 mainly into granulocytes. The results are supported by morphological changes of LAA-treated HL-60 into segmented neutrophils. Therefore, the inhibitory effect of LAA on the growth of HL-60 cells seems to arise from the induction of differentiation. To assess the potential role of LAA, cells were exposed to oxygen radical scavengers in the absence or presence of LAA. Catalase abolished and superoxide dismutase promoted LAA-induced differentiation of HL-60. Thus, H2O2 produced as a result of LAA treatment seems to play a major role in induction of HL-60 differentiation. 相似文献
32.
Technology transition can have significant implications on the evolution of environmental impact potential of disposed electronics over time. Considering technology transition, we quantify the temporal behavior of ecological and human health impact potential from select heavy metals in electronic waste (e‐waste). The case study analyzes product substitution effects in two electronic cohorts from the U.S. market: (1) computers (laptops substituting for desktops) and (2) televisions (flat‐panel liquid crystal displays [LCDs] and plasma displays substituting for cathode‐ray tubes [CRTs]). Quantities of end‐of‐life (EoL) units to year 2030 are forecasted by the unique combination of dynamic material flow analysis, logistic trend analysis, and product lifespan calibration methods. Metal content from EoL units are assessed via a pathway and effect model using USETox? characterization factors to determine the toxicity potential attributed to heavy metal releases into different media (e.g., air, water, and soil) as an indicator of environmental burden. Results show high impact materials such as lead, nickel, and zinc cause changes in human health toxicity potential and copper causes changes in ecological toxicity potential. Effects of dematerialization, such as reduced metal content in laptops over desktops, provide some positive benefits in toxicity potential per product. However, from a market perspective, emerging e‐waste quantities created by increasing per capita penetration rates of electronics and increasing population will offset gains in environmental performance at the product level. The resulting analysis provides guidance on the timing expected for emerging EoL units and an indication of high impact potential materials requiring pollution prevention as product substitution occurs. 相似文献
33.
Jae-Jin Lee Hyun Ji Lee Gi Seon Jang Ja Myoung Yu Ji Yoon Cha Su Jeong Kim Eun Bit Lee Myung Kyum Kim 《Journal of microbiology (Seoul, Korea)》2013,51(3):305-311
Strain DY59T, a Gram-positive non-motile bacterium, was isolated from soil in South Korea, and was characterized to determine its taxonomic position. Phylogenetic analysis based on the 16S rRNA gene sequence of strain DY59T revealed that the strain DY59T belonged to the family Deinococcaceae in the class Deinococci. The highest degree of sequence similarities of strain DY59T were found with Deinococcus radiopugnans KACC 11999T (99.0%), Deinococcus marmoris KACC 12218T (97.9%), Deinococcus saxicola KACC 12240T (97.0%), Deinococcus aerolatus KACC 12745T (96.2%), and Deinococcus frigens KACC 12220T (96.1%). Chemotaxonomic data revealed that the predominant fatty acids were iso-C15:0 (19.0%), C16:1 ω7c (17.7%), C15:1 ω6c (12.6%), iso-C17:0 (10.3%), and iso-C17:1 ω9c (10.3%). A complex polar lipid profile consisted of a major unknown phosphoglycolipid. The predominant respiratory quinone is MK-8. The cell wall peptidoglycan contained D-alanine, L-glutamic acid, glycine, and L-ornithine (di-amino acid). The novel strain showed resistance to gamma radiation, with a D10 value (i.e. the dose required to reduce the bacterial population by 10-fold) in excess of 5 kGy. Based on the phylogenetic, chemotaxonomic, and phenotypic data, strain DY59T (=KCTC 33033T =JCM 18581T) should be classified as a type strain of a novel species, for which the name Deinococcus swuensis sp. nov. is proposed. 相似文献
34.
Rice is the most widely consumed staple food, and is cultivated worldwide to satisfy our daily caloric needs. Thus, extensive efforts on rice breeding and biotechnology have substantially focused on the development of elite cultivars with high yields and better grain quality, as well as enhanced resistance against biotic and abiotic stresses. Recently, it has been observed that rice is more than a just grain-producing crop. Carbon-rich materials of the rice cell wall polysaccharides from post-harvest wastes, including the straw and husk, have been converted into bioethanol and other invaluable, renewable materials. In order to maximize the utilization of cell wall-derived resources, it is imperative to understand cell wall chemistry and molecular mechanism underlying cell wall biosynthesis in rice. In the last decade, several approaches, including mutational genetics and the functional characterization of candidate genes, have been successful in isolating some of cell wall biosynthetic genes in rice, marking the first step forward in obtaining a complete understanding of rice cell wall biosynthesis, although the exact biochemical functions have not been conclusive. In this paper, we focus on integrating old and new information to provide an updated perspective in the cell wall formation of rice, highlighting the chemical structures and biosynthesis of rice cell wall polysaccharides. 相似文献
35.
Jae Choon Kim Jin Hyun Seong Brian Lee Yas Hashimura Daniel Groux Duk Jae Oh 《Biotechnology and Bioprocess Engineering》2013,18(4):801-807
Single use culture systems are a tool in research and biotechnology manufacturing processes and are employed in mammalian cell-based manufacturing processes. Recently, we characterized a novel bioreactor system developed by PBS Biotech. The Pneumatic Bioreactor System? (PBS) employs the Air-wheel?, which is a mixing device similar in structure to a water wheel but is driven by the buoyant force of gas bubbles. In this study, we investigated the physical properties of the PBS system, with which we performed biological tests. In 2 L PBS, the mixing times ranged from 6 (30 rpm, 0.175 vvm) to 15 sec (10 rpm, 0.025 vvm). The kLa value reached upto 7.66/h at 0.5 vvm, even without a microsparger, though this condition is not applicable for cell cultures. Also, when a 10 L PBS equipped with a microsparger was evaluated, a kLa value of upto approximately 20/h was obtained particularly in mild cell culture conditions. We performed cultivation of Chinese hamster ovary (CHO) cells in 2 and 10 L PBS prototypes. Results from the PBS were compared with those from an Erlenmeyer flask and conventional stirred tank type bioreactor (STR). The maximum cell density of 10.6 × 106 cells/mL obtained fromthe 2 L PBSwas about 2 times higher than that from the Erlenmeyer flask (5.6 × 106 cells/mL) andwas similar to the STR (9.7 × 106 cells/mL) when the CHO-S cells were cultured. These results support the general suitability of the PBS system using pneumatic mixing for suspension cell cultivation as a novel single-use bioreactor system. 相似文献
36.
37.
38.
39.
Jun Seo Goo Yo Na Kim Kyung Mi Choi In Sik Hwang Ji Eun Kim Young Ju Lee Moon Hwa Kwak Sun Bo Shim Seung Wan Jee Chul Joo Lim Je Kyung Seong Dae Youn Hwang 《Clinical proteomics》2013,10(1):10
Background
To characterize changes in global protein expression in kidneys of transgenic rats overexpressing human selenoprotein M (SelM) in response to increased bioabivility of selenium (Sel), total proteins extracted from kidneys of 10-week-old CMV/hSelM Tg and wild-type rats were separated by 2-dimensional gel electrophoresis and measured for changes in expression.Results
Ten and three proteins showing high antioxidant enzymatic activity were up- and down-regulated, respectively, in SelM-overexpressing CMV/hSelM Tg rats compared to controls based on an arbitrary 2-fold difference. Up-regulated proteins included LAP3, BAIAP2L1, CRP2, CD73 antigen, PDGF D, KIAA143 homolog, PRPPS-AP2, ZFP313, HSP-60, and N-WASP, whereas down-regulated proteins included ALKDH3, rMCP-3, and STC-1. After Sel treatment, five of the up-regulated proteins were significantly increased in expression in wild-type rats, whereas there were no changes in CMV/hSelM Tg rats. Only two of the down-regulated proteins showed reduced expression in wild-type and Tg rats after Sel treatment.Conclusions
These results show the primary novel biological evidences that new functional protein groups and individual proteins in kidneys of Tg rats relate to Sel biology including the response to Sel treatment and SelM expression. 相似文献40.
Byung-Im So Yi-Sun Song Cheng-Hu Fang Jun-Young Park Yonggu Lee Jeong Hun Shin Hyuck Kim Kyung-Soo Kim 《PloS one》2013,8(10)