全文获取类型
收费全文 | 8757篇 |
免费 | 633篇 |
国内免费 | 3篇 |
专业分类
9393篇 |
出版年
2024年 | 10篇 |
2023年 | 33篇 |
2022年 | 102篇 |
2021年 | 191篇 |
2020年 | 119篇 |
2019年 | 146篇 |
2018年 | 236篇 |
2017年 | 236篇 |
2016年 | 363篇 |
2015年 | 514篇 |
2014年 | 604篇 |
2013年 | 668篇 |
2012年 | 813篇 |
2011年 | 802篇 |
2010年 | 511篇 |
2009年 | 454篇 |
2008年 | 565篇 |
2007年 | 519篇 |
2006年 | 476篇 |
2005年 | 397篇 |
2004年 | 385篇 |
2003年 | 309篇 |
2002年 | 255篇 |
2001年 | 145篇 |
2000年 | 112篇 |
1999年 | 89篇 |
1998年 | 46篇 |
1997年 | 43篇 |
1996年 | 24篇 |
1995年 | 27篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 22篇 |
1991年 | 28篇 |
1990年 | 24篇 |
1989年 | 23篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有9393条查询结果,搜索用时 15 毫秒
81.
Kung Ahn Jin-Han Bae Kyu-Hwi Nam Chong-Eon Lee Kyung-Do Park Hak-Kyo Lee Byung-Wook Cho Heui-Soo Kim 《Genes & genomics.》2011,33(3):245-250
Quantitative analysis of horse gene expression profiles under diverse experimental conditions is limited by the lack of reliable reference genes for normalization of mRNA levels. Therefore, in this study, the expression of potential reference genes was compared between thoroughbred and Jeju native horse (Jeju pony). We compared the expression of nine genes by quantitative real-time RT-PCR in fourteen tissues between the two horse breeds and analyzed their stability using the geNorm and NormFinder programs. The data obtained in this study suggest that the UBB gene could serve as a reference gene in gene expression analysis of thoroughbred and Jeju native horses. 相似文献
82.
Purification of aquarium water by PVA gel-immobilized photosynthetic bacteria during goldfish rearing 总被引:1,自引:0,他引:1
Soo Kyong Jeong Jeong-Sup Cho In-Soo Kong Hyun Do Jeong Joong Kyun Kim 《Biotechnology and Bioprocess Engineering》2009,14(2):238-247
This study was conducted to evaluate the ability of a PVA-gel beads filtration (PVA) system using photosynthetic bacteria
to purify water. To accomplish this, duplicate long-term goldfish rearing experiments were conducted using four different
types of aquarium systems (COF, PSB, EMC, and PVA). The results revealed that the concentrations of NH4
+-N on the day of a goldfish’s death were significantly higher than the concentrations on other days for all the aquarium systems.
In addition, the mean concentration of NH4
+-N during goldfish rearing occurred in the following order: COF system > EMC system > PSB system > PVA system. Furthermore,
the mean values of all other ion concentrations (NO3
−-N, NO2
−-N, and PO4
2−-P) were found to be lowest in the PVA system. As a result, there was more prominent decomposition of organic matter in the
aquarium tank containing the PVA system, as well as less turbid aquarium water and more active goldfish. Additionally, the
PVA-gel beads resulted in almost complete denitrification, even after six-months of goldfish rearing. To our knowledge, this
is the first study to report that PVA gel-immobilized photosynthetic bacteria have the ability to purify water. Overall, the
results of this study indicate that this immobilized photosynthetic bacteria system has the potential for use as a component
in circulating filtration systems. 相似文献
83.
Kim JY Kim YG Han YK Choi HS Kim YH Lee GM 《Applied microbiology and biotechnology》2011,89(6):1917-1928
In order to understand the intracellular responses in recombinant CHO (rCHO) cells producing antibody in serum-free medium
(SFM) supplemented with optimized hydrolysates mixtures, yielding the highest specific growth rate (μ, SFM#S1) or the highest
specific antibody productivity (q
Ab, SFM#S2), differentially expressed proteins in rCHO cells are measured by two-dimensional gel electrophoresis combined with
nano-LC-ESI-Q-TOF tandem MS. The comparative proteomic analysis with basal SFM without hydrolysates revealed that the addition
of hydrolysate mixtures significantly altered the profiles of CHO proteome. In SFM#S1, the expression of metabolism-related
proteins, cytoskeleton-associated proteins, and proliferation-related proteins was up-regulated. On the other hand, the expression
of anti-proliferative proteins and pro-apoptotic protein was down-regulated. In SFM#S2, the expression of various chaperone
proteins and proliferation-linked proteins was altered. 2D-Western blot analysis of differentially expressed proteins confirmed
the proteomic results. Taken together, identification of differentially expressed proteins in CHO cells by a proteomic approach
can provide insights into understanding the effect of hydrolysates on intracellular events and clues to find candidate genes
for cell engineering to maximize the protein production in rCHO cells. 相似文献
84.
To investigate the effect of Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) on human cancer cells, we sought to identify and analyze potential target genes that were differentially expressed in the presence and absence of LMP1. Our cDNA microarray analysis revealed that expression of early growth response gene-1 (Egr-1) was increased by LMP1 expression in MCF7 and Jurkat cells. An NFkappaB inhibitor (SN50) antagonized LMP1-induced enhancement of Egr-1 expression, indicating that LMP1 induced Egr-1 via NFkappaB. Furthermore, three lines of evidence indicated that Egr-1 was required for LMP1-induced cancer cell survival. First, Egr-1 expression enhanced the survival of doxorubicin-treated MCF7 cells. Second, inhibition of Egr-1 expression by siRNA (siEgr-1) effectively suppressed LMP-1-induced survival of MCF7 cells. Third, Egr-1 knockdown decreased LMP1-induced expression of Bfl-1. Similar relationships among EBV infection, Egr-1 and drug resistance were also observed in tissues of peripheral T-cell lymphoma-unspecified (PTCL-u) patients. 相似文献
85.
Kyoung Ah Kang Rui Zhang Mei Jing Piao Min Jeong Park Ae Ran Kwon Bum Joon Kim Ho Jin You Myung Hee Chung Jin Won Hyun 《Biotechnology and Bioprocess Engineering》2007,12(2):114-120
8-Hydroxydeoxyguanosine (oh8dG) treatment induced senescence-like changes in KG-1 cells, a human acute myelocytic leukemia cell line. The oh8dG-treated cells stained positive for senescence associated β-galactosidase (SA-β-galactosidase) and had enlarged cell shape,
both of which are senescence indexes. The oh8dG-treated cells were also cell growth inhibited and arrested at G1 in the cell cycle. The accumulation of cdk (cyclin dependent kinase) inhibitors, such as p16, p21, and p27, also implies
that cellular senescence was induced in oh8dG-treated cells. However, these changes were not accompanied by cell differentiation or telomerase activity. Taken together,
we conclude that oh8dG treatment of KG-1 cells induces cellular senescence. 相似文献
86.
Yoon SM Choi CH Kim M Hyun MS Shin SH Yi DH Kim HJ 《Journal of microbiology and biotechnology》2007,17(1):110-115
Electrochemically active bacteria were successfully enriched in an electrochemical cell using a positively poised working electrode. The positively poised working electrode (+0.7 V vs. Ag/AgCl) was used as an electron acceptor for enrichment and growth of electrochemically active bacteria. When activated sludge and synthetic wastewater were fed to the electrochemical cell, a gradual increase in amperometric current was observed. After a period of time in which the amperometric current was stabilized (generally 8 days), linear correlations between the amperometric signals from the electrochemical cell and added BOD (biochemical oxygen demand) concentrations were established. Cyclic voltammetry of the enriched electrode also showed prominent electrochemical activity. When the enriched electrodes were examined with electron microscopy and confocal scanning laser microscopy, a biofilm on the enriched electrode surface and bacterium-like particles were observed. These experimental results indicate that the electrochemical system in this study is a useful tool for the enrichment of an electrochemically active bacterial consortium and could be used as a novel microbial biosensor. 相似文献
87.
Improved fuel cell and electrode designs for producing electricity from microbial degradation 总被引:34,自引:0,他引:34
A new one-compartment fuel cell was composed of a rubber bunged bottle with a center-inserted anode and a window-mounted cathode containing an internal, proton-permeable porcelain layer. This fuel cell design was less expensive and more practical than the conventional two-compartment system, which requires aeration and a ferricyanide solution in the cathode compartment. Three new electrodes containing bound electron mediators including a Mn(4+)-graphite anode, a neutral red (NR) covalently linked woven graphite anode, and an Fe(3+)-graphite cathode were developed that greatly enhanced electrical energy production (i.e., microbial electron transfer) over conventional graphite electrodes. The potentials of these electrodes measured by cyclic voltametry at pH 7.0 were (in volts): +0.493 (Fe(3+)-graphite); +0.15 (Mn(4+)-graphite); and -0.53 (NR-woven graphite). The maximal electrical productivities obtained with sewage sludge as the biocatalyst and using a Mn(4+)-graphite anode and a Fe(3+)-graphite cathode were 14 mA current, 0.45 V potential, 1,750 mA/m(2) current density, and 788 mW/m(2) of power density. With Escherichia coli as the biocatalyst and using a Mn(4+)-graphite anode and a Fe(3+)-graphite cathode, the maximal electrical productivities obtained were 2.6 mA current, 0.28 V potential, 325 mA/m(2) current density, and 91 mW/m(2) of power density. These results show that the amount of electrical energy produced by microbial fuel cells can be increased 1,000-fold by incorporating electron mediators into graphite electrodes. These results also imply that sewage sludge may contain unique electrophilic microbes that transfer electrons more readily than E. coli and that microbial fuel cells using the new Mn(4+)-graphite anode and Fe(3+)-graphite cathode may have commercial utility for producing low amounts of electrical power needed in remote locations. 相似文献
88.
Acetohydroxy acid isomeroreductase (AHIR) is a key enzyme in the biosynthesis of branched-chain amino acids. We have determined the first crystal structure of a class I AHIR from Pseudomonas aeruginosa at 2.0 A resolution. Its dodecameric architecture of 23 point group symmetry is assembled of six dimeric units and dimerization is essential for the formation of the active site. The dimeric unit of P.aeruginosa AHIR partially superimposes with a three-domain monomer of spinach AHIR, a class II enzyme. This demonstrates that the so-called plant-specific insert in the middle of spinach AHIR is structurally and functionally equivalent to the C-terminal alpha-helical domain of P.aeruginosa AHIR, and the C-terminal alpha-helical domain was duplicated during evolution from the shorter, class I AHIRs to the longer, class II AHIRs. The dimeric unit of P.aeruginosa AHIR possesses a deep figure-of-eight knot, essentially identical with that in the spinach AHIR monomer. Thus, our work lowers the likelihood of the previous proposal that "domain duplication followed by exchange of a secondary structure element can be a source of such a knot in the protein structure" being correct. 相似文献
89.
Monitoring and classification of PAH toxicity using an immobilized bioluminescent bacteria 总被引:6,自引:0,他引:6
An immobilized recombinant bioluminescent Escherichia coli strain, harboring a lac::luxCDABE fused plasmid, which shows lower bioluminescence levels when cellular metabolism is inhibited, was used to monitor the cellular toxicity of polycyclic aromatic hydrocarbons (PAHs). PAHs, classified as pericondensed (PCPAHs) or catacondensed (CCPAHs) according to their molecular structures, were differentiable according to the response of this biosensor. Only CCPAHs were found to cause cellular toxicity, resulting in a dose-dependent decrease in the bioluminescent output. The induction of cellular toxicity by CCPAHs and PCPAHs was compared with acute toxicity predictions obtained using the quantitative structure-activity relationship (QSAR) model. A good relationship was obtained between the toxicities determined with the bioluminescent response of the immobilized bacterium GC2 and the QSAR model. It was also found that the present study offers a new method of predicting the cellular toxicities of CCPAHs or PCPAHs using this biosensor. 相似文献
90.
Two non-stoichiometric binding sites had previously been characterized for the NK-1 receptor using two different types of radiolabelled analogues of substance P. However, the question remained on their eventual conformational interconversion induced or not by the ligand. In this study, kinetic, saturation, and competition studies using [3H]propionyl[Pro(9)]SP demonstrate the existence of two independent binding components in CHO cells transfected with the human NK-1 receptor, with K(d) values of 0.040 nM ( approximately 20% of total sites) and 5.9 nM ( approximately 80% of total sites) that correspond to those of the two previously described binding sites. These two binding sites do not seem to interconvert since the minor one can be selectively extinguished in saturation studies in the presence of a SP analogue specific of this binding site. 相似文献