全文获取类型
收费全文 | 19532篇 |
免费 | 708篇 |
国内免费 | 244篇 |
专业分类
20484篇 |
出版年
2024年 | 126篇 |
2023年 | 131篇 |
2022年 | 372篇 |
2021年 | 528篇 |
2020年 | 391篇 |
2019年 | 496篇 |
2018年 | 559篇 |
2017年 | 497篇 |
2016年 | 718篇 |
2015年 | 1079篇 |
2014年 | 1253篇 |
2013年 | 1388篇 |
2012年 | 1685篇 |
2011年 | 1626篇 |
2010年 | 1030篇 |
2009年 | 864篇 |
2008年 | 1167篇 |
2007年 | 1022篇 |
2006年 | 871篇 |
2005年 | 777篇 |
2004年 | 790篇 |
2003年 | 610篇 |
2002年 | 495篇 |
2001年 | 308篇 |
2000年 | 272篇 |
1999年 | 262篇 |
1998年 | 133篇 |
1997年 | 91篇 |
1996年 | 69篇 |
1995年 | 76篇 |
1994年 | 69篇 |
1993年 | 54篇 |
1992年 | 86篇 |
1991年 | 87篇 |
1990年 | 60篇 |
1989年 | 59篇 |
1988年 | 41篇 |
1987年 | 26篇 |
1986年 | 30篇 |
1985年 | 36篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1977年 | 18篇 |
1975年 | 16篇 |
1974年 | 17篇 |
1970年 | 12篇 |
1969年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
91.
Atanas V. Demirev Ji Seon Lee Bhishma R. Sedai Ivan G. Ivanov Doo Hyun Nam 《Journal of microbiology (Seoul, Korea)》2009,47(4):473-478
The gene locus for acetyl-CoA carboxylase (ACC) involved in the primary metabolism was identified from the genomic library
of Streptomyces toxytricini which produces a lipase inhibitor lipstatin. The 7.4 kb cloned gene was comprised of 5 ORFs including accD1, accA1, hmgL, fadST1, and stsF. In order to confirm the biochemical characteristics of AccA1, the gene was overexpressed in Escherichia coli cells, and the recombinant protein was purified through Ni2+ affinity chromatography. Because most of the expressed AccAl was biotinylated by host E. coli BirA in the presence of D-biotin, the non-biotinylated apo-AccA1 was purified after gene induction without D-biotin, followed by exclusion of holo-AccA1 using streptavidin beads. The separated apo-AccA1 was post-translationally biotinylated
by S. toxytricini biotin apo-protein ligase (BPL) in a time- and enzyme-dependent manner. This result supports that this gene cluster of S. toxytricini encodes the functional ACC enzyme subunits to be biotinylated. 相似文献
92.
93.
Effects of load carriage and fatigue on gait characteristics 总被引:1,自引:0,他引:1
The objective of this study was to determine the main and interactive effects of load carriage and fatigue on gait characteristics. Twelve young male participants were recruited in this study. Fatiguing protocol involved a running exercise, and fatigue was considered to be induced when the participants first gave an RPE rating at or above 17. Gait data were collected when the participants walked on a medical treadmill at their self-selected comfortable speed, both before and right after the fatiguing exercise. Different back-carrying loads (i.e. 0, 7.5, and 15 kg) were applied separately to the participants during the walking trials. Gait variability measures and kinematic measures were used to quantify gait characteristics. The results showed that gait width variability, hip range of motion, and trunk range of motion increased with fatigue and with the application of the heavy load. These findings suggest that both fatigue and load carriage compromise gait. Findings from this study can help better understand how fatigue and load carriage affect gait, and further aid in developing interventions that are able to minimize fall risks especially with the application of fatigue and/or external load. 相似文献
94.
Hee Wan Kang Yong Gu Cho Ung Han Yoon Moo Young Eun 《Plant Molecular Biology Reporter》1998,16(1):90-90
A single-seed DNA extraction method was developed for rapid identification of plant genotype. The method was applied to 12 plant species, including the oil seeds sesame and soybean. The results were comparable to those obtained for oil-less seeds such as rice. This method will be useful for genotypic selection which requires rapid screening of large populations. It can also be used to identify varietal purity of seed stocks by PCR and RFLP analysis. The method includes two major steps, (i) treatment by proteinase K in an SDS extraction buffer, and (ii) grinding of a single half seed in the buffer after incubation. About 1.5–2 µg of DNA per half seed (the endosperm part) of rice was obtained and more than 200 half seed samples could be handled by one person in a day. The DNA could be used for fingerprinting and detection of target genes in a transgenic plant by PCR. The amplified PCR products from the half seed DNA exhibited the same banding patterns as those from leaf DNA. Yield and quality of DNA extracted from half seeds of rice was also sufficient for RFLP analysis. The remnant half seeds containing the embryo can be maintained for later germination of selected genotypes. 相似文献
95.
Quality of Life and Its Association with Physical Activity among Different Types of Cancer Survivors
PurposeThe main goal of this study was to compare the quality of life (QOL) and its association with physical activity (PA) among patients diagnosed with different types of cancer. Based on the results, we tentatively present suggestions for the cancer health care model.MethodA cross-sectional study was conducted with 2915 cancer survivors recruited from multi-community cancer rehabilitation centers, all of which were affiliated with the Shanghai Cancer Rehabilitation Club. We collected data including socio-demographic characteristics and information about PA. All the subjects included were asked to complete the European Organization for Research and Treatment Quality of Life Questionnaires (EORTC QLQ-C30) and Functional Assessment of Cancer Therapy—General Questionnaire (FACT-G). Multiple linear regression models were employed to control the potential confounding factors.ResultsLung cancer survivors reported the worst dyspnea. Colorectal cancer survivors claimed the highest level of constipation and diarrhea. Liver cancer survivors indicated greatest loss of appetite and financial difficulties. Generally, survivors with PA tended to reported better QOL, although these associations among liver cancer survivors were not statistically significant. Moreover, survivors of all cancer types who performed PA did not report significant lower level of constipation or diarrhea. The relationship between PA frequency and QOL among cancer survivors remained unexplored.ConclusionsBoth QOL and its association with PA vary among survivors of different cancer types. The detailed results can assist clinicians and public health practitioners with improving health care management. 相似文献
96.
Genome sequence of Leuconostoc fallax KCTC 3537 总被引:2,自引:0,他引:2
Nam SH Choi SH Kang A Kim DW Kim DS Kim RN Kim A Park HS 《Journal of bacteriology》2011,193(2):588-589
Leuconostoc fallax is known to be present during the manufacturing process of kimchi, the best-known traditional Korean dish. Here, we present the draft genome sequence of the type strain Leuconostoc fallax KCTC 3537 (1,638,971 bp, with a G+C content of 37.5%), which consists of 30 large contigs (>100 bp in size). 相似文献
97.
Ki-Yeol Kim Dong Hyuk Ki Ha Jin Jeong Hei-Cheul Jeung Hyun Cheol Chung Sun Young Rha 《BMC bioinformatics》2007,8(1):218
Background
With microarray technology, variability in experimental environments such as RNA sources, microarray production, or the use of different platforms, can cause bias. Such systematic differences present a substantial obstacle to the analysis of microarray data, resulting in inconsistent and unreliable information. Therefore, one of the most pressing challenges in the field of microarray technology is how to integrate results from different microarray experiments or combine data sets prior to the specific analysis. 相似文献98.
99.
Paragonimus westermani: molecular cloning,expression, and characterization of a recombinant yolk ferritin 总被引:2,自引:0,他引:2
Ferritin is an intracellular protein involved in iron metabolism. A cDNA PwYF-1 cloned from the adult Paragonimus westermani cDNA library encoded a putative polypeptide of 216 amino acids homologous with ferritins of vertebrates and invertebrates. Febinding motifs identified in PwYF-1 polypeptide were conserved and predicted to form a ferroxidase center. PwYF-1 polypeptide contained an extended peptide of 45 amino acids at its C-terminus. Recombinant PwYF-1 protein, expressed and purified from Escherichia coli, showed iron-uptake ability and ferroxidase activity. Ferroxidase activity of recombinant PwYF-1 protein was reactivated by secondary addition of apotransferrin to assay mixture. Mouse immune serum raised against the recombinant PwYF-1 protein recognized specifically 24 kDa protein from adult P. westermani lysate. PwYF-1 protein was localized to vitelline follicles and the eggs of P. westermani. Collectively, PwYF-1 protein was identified as a P. westermani yolk ferritin. 相似文献
100.
Effect of acidity on the enantiomeric resolution of thyroxine and tocainide by HPLC on a (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid column 总被引:1,自引:0,他引:1
Aboul-Enein HY Ali I Hyun MH Cho YJ Jin JS 《Journal of biochemical and biophysical methods》2002,54(1-3):407-413
Enantiomeric resolution of thyroxine and tocainide was achieved on a (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid column. The mobile phases were methanol/water (4:1, v/v) and methanol/water containing 5 mM sulfuric acid (4:1, v/v) for tocainide and thyroxine respectively. The flow rate was 0.5 ml/min. The effect of the acidity on the chiral resolution of these drugs was studied. Detection was at 220 nm for both drugs. The values of alpha and Rs were 2.08-3.11 and 1.00-2.60, respectively, for thyroxine while the values of alpha and Rs were 1.13-1.26 and 0.10-1.30, respectively, for tocainide. 相似文献