全文获取类型
收费全文 | 10657篇 |
免费 | 898篇 |
国内免费 | 5篇 |
专业分类
11560篇 |
出版年
2024年 | 8篇 |
2023年 | 36篇 |
2022年 | 116篇 |
2021年 | 218篇 |
2020年 | 154篇 |
2019年 | 190篇 |
2018年 | 289篇 |
2017年 | 289篇 |
2016年 | 431篇 |
2015年 | 611篇 |
2014年 | 716篇 |
2013年 | 783篇 |
2012年 | 1038篇 |
2011年 | 924篇 |
2010年 | 622篇 |
2009年 | 519篇 |
2008年 | 704篇 |
2007年 | 658篇 |
2006年 | 610篇 |
2005年 | 500篇 |
2004年 | 464篇 |
2003年 | 421篇 |
2002年 | 311篇 |
2001年 | 139篇 |
2000年 | 125篇 |
1999年 | 92篇 |
1998年 | 69篇 |
1997年 | 56篇 |
1996年 | 34篇 |
1995年 | 35篇 |
1994年 | 31篇 |
1993年 | 17篇 |
1992年 | 36篇 |
1991年 | 32篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 31篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1972年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Hyun Koo Kim Moon Sun Ham Jong Soo Hong Jin Ha Lee Kyung Yu Park Hyeon Yong Lee 《Biotechnology and Bioprocess Engineering》1996,1(1):32-35
A moving aeration-membrane (MAM) bioreactor was employed for the production of 2 μg/mL of tissue type Plasminogen Activator (tPA) in serum free medium from normal human fibroblast cells. This system could maintain high cell density for long periods of steady state conditions in perfusion cultivation. Under normal operating conditions, shear stress was as low as 0.65 dynes/cm2 at the agitation speed of 80 rpm. Even though cell density gradually decreased with increasing agitation speed, tPA production increased linearly with increasing shear stress within a moderate range. This culture system allowed production of 2 μg tPA/mL while maintaining a high cell density of 1.0×107 viable cells/mL. 相似文献
22.
Bae JS Cheong HS Kim JH Park BL Kim JH Park TJ Kim JY Pasaje CF Lee JS Park YJ Park M Park C Koh I Chung YJ Lee JY Shin HD 《PloS one》2011,6(4):e19091
Background
Unlike Caucasian populations, genetic factors contributing to the risk of type 2 diabetes mellitus (T2DM) are not well studied in Asian populations. In light of this, and the fact that copy number variation (CNV) is emerging as a new way to understand human genomic variation, the objective of this study was to identify type 2 diabetes–associated CNV in a Korean cohort.Methodology/Principal Findings
Using the Illumina HumanHap300 BeadChip (317,503 markers), genome-wide genotyping was performed to obtain signal and allelic intensities from 275 patients with type 2 diabetes mellitus (T2DM) and 496 nondiabetic subjects (Total n = 771). To increase the sensitivity of CNV identification, we incorporated multiple factors using PennCNV, a program that is based on the hidden Markov model (HMM). To assess the genetic effect of CNV on T2DM, a multivariate logistic regression model controlling for age and gender was used. We identified a total of 7,478 CNVs (average of 9.7 CNVs per individual) and 2,554 CNV regions (CNVRs; 164 common CNVRs for frequency>1%) in this study. Although we failed to demonstrate robust associations between CNVs and the risk of T2DM, our results revealed a putative association between several CNVRs including chr15:45994758–45999227 (P = 8.6E-04, Pcorr = 0.01) and the risk of T2DM. The identified CNVs in this study were validated using overlapping analysis with the Database of Genomic Variants (DGV; 71.7% overlap), and quantitative PCR (qPCR). The identified variations, which encompassed functional genes, were significantly enriched in the cellular part, in the membrane-bound organelle, in the development process, in cell communication, in signal transduction, and in biological regulation.Conclusion/Significance
We expect that the methods and findings in this study will contribute in particular to genome studies of Asian populations. 相似文献23.
Jung YY Oh MS Shin DW Kang SH Oh HS 《Biometrical journal. Biometrische Zeitschrift》2006,48(3):435-450
A Bayesian model-based clustering approach is proposed for identifying differentially expressed genes in meta-analysis. A Bayesian hierarchical model is used as a scientific tool for combining information from different studies, and a mixture prior is used to separate differentially expressed genes from non-differentially expressed genes. Posterior estimation of the parameters and missing observations are done by using a simple Markov chain Monte Carlo method. From the estimated mixture model, useful measure of significance of a test such as the Bayesian false discovery rate (FDR), the local FDR (Efron et al., 2001), and the integration-driven discovery rate (IDR; Choi et al., 2003) can be easily computed. The model-based approach is also compared with commonly used permutation methods, and it is shown that the model-based approach is superior to the permutation methods when there are excessive under-expressed genes compared to over-expressed genes or vice versa. The proposed method is applied to four publicly available prostate cancer gene expression data sets and simulated data sets. 相似文献
24.
Tong L Lin Q Wong WK Ali A Lim D Sung WL Hew CL Yang DS 《Protein expression and purification》2000,18(2):175-181
HPLC6 is the major component of liver-type antifreeze polypeptides (AFPs) from the winter flounder, Pleuronectes americanus. To facilitate mutagenesis studies of this protein, a gene encoding the 37-amino acid mature polypeptide was chemically synthesized and cloned into the Tac cassette immediately after the bacterial ompA leader sequence for direct excretion of the AFP into the culture medium. Escherichia coli transformant with the construct placIQpar8AF was cultured in M9 medium. The recombinant AFP (rAFP) was detected by a competitive enzyme-linked immunosorbent assay (ELISA). After IPTG induction, a biologically active rAFP was expressed. The majority of the rAFP was excreted into the culture medium with only trace amounts trapped in the periplasmic space and cytoplasm. After 18 h of induction, the accumulated rAFP in the culture medium amounted to about 16 mg/L. The excreted AFP was purified from the culture medium by a single-step reverse-phase HPLC. Mass spectrometric and amino acid composition analyses confirmed the identity of the purified product. The rAFP, which lacked amidation at the C-terminal, was about 70% active when compared to the amidated wild-type protein, thus confirming the importance of C-terminal cap structure in protein stability and function. 相似文献
25.
Suyoung Yoon Sung-Eun Kim Jong Hyun Kim Ina Yoon Phuong-Thao Tran Jihyae Ann Changhoon Kim Woong Sub Byun Sangkook Lee Sunghoon Kim Jiyoun Lee Jeewoo Lee 《Bioorganic & medicinal chemistry》2019,27(6):1099-1109
Leucyl-tRNA synthetase (LRS) plays an important role in amino acid-dependent mTORC1 signaling, which is known to be associated with cellular metabolism and proliferation. Therefore, LRS-targeting small molecules that can suppress mTORC1 activation may provide an alternative strategy to current anticancer therapy. In this work, we developed a library of leucyladenylate sulfate analogues by extensively modifying three different pharmacophoric regions comprising adenine, ribose and leucine. Several effective compounds were identified by cell-based mTORC1 activation assays and further tested for anticancer activity. The selected compounds mostly exhibited selective cytotoxicity toward five different cancer cell lines, supporting the hypothesis that the LRS-mediated mTORC1 pathway is a promising alternative target to current therapeutic approaches. 相似文献
26.
WEHI-231 and Bal 17 B cell lines are representative models for immature and mature B cells, respectively. Their regulation of cytosolic Ca(2+) concentration ([Ca(2+)](c)) was compared using fura-2 fluorescence ratiometry. The ligation of B cell antigen receptor (BCR) by anti-IgM antibody induced a slow but large increase of [Ca(2+)](c) in WEHI-231 cells while not in Bal 17 cells. The thapsigargin-induced store-operated Ca(2+) entry (SOCE) of Bal 17 cells reached a steady state which was blocked by 2-aminoethoxydiphenyl borate (2-APB). On the contrary, the thapsigargin-induced SOCE of WEHI-231 cells increased continuously, which was accelerated by 2-APB. The increase of [Ca(2+)](c) by BCR ligation was also enhanced by 2-APB in WEHI-231 cells while blocked in Bal 17 cells. The Mn(2+) quenching study showed that the thapsigargin-, or the BCR ligation-induced Ca(2+) influx pathway of WEHI-231 was hardly permeable to Mn(2+). The intractable increase of [Ca(2+)](c) may explain the mechanism of BCR-driven apoptosis of WEHI-231 cells, a well-known model of clonal deletion of autoreactive immature B cells. 相似文献
27.
28.
29.
Doo Hyun Park 《Bioscience, biotechnology, and biochemistry》2018,82(7):1234-1242
Bacterial communities and metabolites in kimchi fermented under conventional conditions (CC) compared to CO2-rich environments (CO2) were analyzed. After a 20-day fermentation, lactic and acetic acid productions were 54 and 69 mM under CC, and 19 and 12 mM under CO2, respectively. The final pH of kimchi fermented under CC (CC-fermenting) and CO2 (CO2-fermenting) were 4.1 and 4.7, respectively. For bacterial communities, OTU and Chao1 indices were both 35 in fresh kimchi, 10 and 15 in CC-fermenting kimchi, and 8 and 24 in CO2-fermenting kimchi, respectively. Shannon and Simpson indices were 3.47 and 0.93 in fresh kimchi, 1.87–0.06 and 0.46–0.01 in CC-fermenting kimchi, and 1.65–0.44 and 0.63–0.12 in CO2-fermenting kimchi, respectively. Non-lactic acid bacteria were eliminated in fermenting kimchi after 12 days under CC and 6 days under CO2. I conclude that carbon dioxide can alter bacterial communities, reduce metabolite production, and improve fermented kimchi quality. 相似文献
30.
Jong Hyun Park Changhoon Choi Jung Been Park Seungho Yu Dong-Wan Kim 《Liver Transplantation》2024,14(5):2470019