全文获取类型
收费全文 | 511篇 |
免费 | 32篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 42篇 |
2012年 | 43篇 |
2011年 | 35篇 |
2010年 | 20篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 23篇 |
2006年 | 16篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 4篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1965年 | 2篇 |
1949年 | 1篇 |
排序方式: 共有543条查询结果,搜索用时 609 毫秒
101.
Tsunehito Higashi Yosuke Mai Yoichi Noya Takahiro Horinouchi Koji Terada Akimasa Hoshi Prabha Nepal Takuya Harada Mika Horiguchi Chizuru Hatate Yuji Kuge Soichi Miwa 《PloS one》2014,9(9)
Cigarette smoke consists of tar and gas phase: the latter is toxicologically important because it can pass through lung alveolar epithelium to enter the circulation. Here we attempt to establish a standard method for preparation of gas phase extract of cigarette smoke (CSE). CSE was prepared by continuously sucking cigarette smoke through a Cambridge filter to remove tar, followed by bubbling it into phosphate-buffered saline (PBS). An increase in dry weight of the filter was defined as tar weight. Characteristically, concentrations of CSEs were represented as virtual tar concentrations, assuming that tar on the filter was dissolved in PBS. CSEs prepared from smaller numbers of cigarettes (original tar concentrations ≤15 mg/ml) showed similar concentration-response curves for cytotoxicity versus virtual tar concentrations, but with CSEs from larger numbers (tar ≥20 mg/ml), the curves were shifted rightward. Accordingly, the cytotoxic activity was detected in PBS of the second reservoir downstream of the first one with larger numbers of cigarettes. CSEs prepared from various cigarette brands showed comparable concentration-response curves for cytotoxicity. Two types of CSEs prepared by continuous and puff smoking protocols were similar regarding concentration-response curves for cytotoxicity, pharmacology of their cytotoxicity, and concentrations of cytotoxic compounds. These data show that concentrations of CSEs expressed by virtual tar concentrations can be a reference value to normalize their cytotoxicity, irrespective of numbers of combusted cigarettes, cigarette brands and smoking protocols, if original tar concentrations are ≤15 mg/ml. 相似文献
102.
Mapping of hiv-1 Gag epitopes recognized by polyclonal antibodies using gene-fragment phage display system. 总被引:1,自引:0,他引:1
S Gupta K Arora A Sampath S S Singh A Gupta V K Chaudhary 《Preparative biochemistry & biotechnology》2001,31(2):185-200
Phage display has emerged as a powerful technique for mapping epitopes recognised by monoclonal and polyclonal antibodies. We have recently developed a simple gene-fragment phage display system and have shown its utility in mapping epitope recognised by a monoclonal antibody. In the present study, we have employed this system in mapping epitopes recognised by polyclonal antibodies raised against HIV-1 capsid protein, p24 which is derived from proteolytic cleavage of Gag polyprotein. HIV-1 gag DNA was fragmented by DNase I and the fragments (50-250 bp) were cloned into gene-fragment phage display vector to construct a library of phages displaying peptides. This phage library was used for affinity selection of phages displaying epitopes recognised by rabbit anti-p24 polyclonal antibodies. Selected phages contained sequences from two discrete regions of p24, demonstrating the presence of two antigenic regions. The DNA sequences encoding these regions were also cloned and expressed as GST fusion proteins. The immunoreactivity of these epitopes as GST fusion proteins, or as phage-displayed peptides, was comparable in ELISA system using same anti-p24 polyclonal antibodies. The results indicate that the gene-fragment based phage display system can be used efficiently to identify epitopes recognised by polyclonal antibodies, and phage displayed epitopes can be directly employed in ELISA to detect antibodies. 相似文献
103.
N. S. Sampath Kumar R. A. Nazeer R. Jaiganesh 《International journal of peptide research and therapeutics》2012,18(3):185-192
Type I collagen was extracted from the bone of two marine fishes; Magalaspis cordyla and Otolithes ruber and its efficacy in wound healing was studied. The yields of acid soluble (30.5 and 27.6%) and pepsin soluble (45.1 and 48.6%) collagen were respectively as per their dry weight basis. Extracted protein was characterized as type I collagen basing on SDS PAGE, UV?CVis, FTIR spectrometer and amino acid composition. The characterized collagen was cross-linked with glutaraldehyde and found to possess three dimensional pores and acted efficiently in healing the excision wounds made on Wistar rats. Bone is generally considered as waste and discarded in many processing plant. But, the current study proved that it has excellent medicinal importance and reveals a possible way to convert this waste into a medicinally important source. 相似文献
104.
Michael Callahan Anthony M. Treston Grace Lin Marla Smith Brian Kaufman Mansoora Khaliq Lisa Evans DeWald Kevin Spurgers Kelly L. Warfield Preeya Lowe Matthew Duchars Aruna Sampath Urban Ramstedt 《PLoS neglected tropical diseases》2022,16(8)
BackgroundUV-4 (N-(9’-methoxynonyl)-1-deoxynojirimycin, also called MON-DNJ) is an iminosugar small-molecule oral drug candidate with in vitro antiviral activity against diverse viruses including dengue, influenza, and filoviruses and demonstrated in vivo efficacy against both dengue and influenza viruses. The antiviral mechanism of action of UV-4 is through inhibition of the host endoplasmic reticulum-resident α-glucosidase 1 and α-glucosidase 2 enzymes. This inhibition prevents proper glycan processing and folding of virus glycoproteins, thereby impacting virus assembly, secretion, and the fitness of nascent virions.Methodology/Principal findingsHere we report a first-in-human, single ascending dose Phase 1a study to evaluate the safety, tolerability, and pharmacokinetics of UV-4 hydrochloride (UV-4B) in healthy subjects (ClinicalTrials.gov Identifier ). Sixty-four subjects received single oral doses of UV-4 as the hydrochloride salt equivalent to 3, 10, 30, 90, 180, 360, 720, or 1000 mg of UV-4 (6 subjects per cohort), or placebo (2 subjects per cohort). Single doses of UV-4 hydrochloride were well tolerated with no serious adverse events or dose-dependent increases in adverse events observed. Clinical laboratory results, vital signs, and physical examination data did not reveal any safety signals. Dose-limiting toxicity was not observed; the maximum tolerated dose of UV-4 hydrochloride in humans has not yet been determined (>1000 mg). UV-4 was rapidly absorbed and distributed after dosing with the oral solution formulation used in this study. Median time to reach maximum plasma concentration ranged from 0.5–1 hour and appeared to be independent of dose. Exposure increased approximately in proportion with dose over the 333-fold dose range. UV-4 was quantifiable in pooled urine over the entire collection interval for all doses.Conclusions/SignificanceUV-4 is a host-targeted broad-spectrum antiviral drug candidate. At doses in humans up to 1000 mg there were no serious adverse events reported and no subjects were withdrawn from the study due to treatment-emergent adverse events. These data suggest that therapeutically relevant drug levels of UV-4 can be safely administered to humans and support further clinical development of UV-4 hydrochloride or other candidate antivirals in the iminosugar class.Trial registrationClinicalTrials.gov NCT02061358 https://clinicaltrials.gov/ct2/show/ NCT02061358. NCT02061358相似文献
105.
Prabha Chandrasekaran Victoria Moore Monica Buckley Joshua Spurrier John H. Kehrl Sundararajan Venkatesan 《PloS one》2014,9(1)
Human and Simian Immunodeficiency virus (HIV-1, HIV-2, and SIV) encode an accessory protein, Nef, which is a pathogenesis and virulence factor. Nef is a multivalent adapter that dysregulates the trafficking of many immune cell receptors, including chemokine receptors (CKRs). Physiological endocytic itinerary of agonist occupied CXCR4 involves ubiquitinylation of the phosphorylated receptor at three critical lysine residues and dynamin-dependent trafficking through the ESCRT pathway into lysosomes for degradation. Likewise, Nef induced CXCR4 degradation was critically dependent on the three lysines in the C-terminal -SSLKILSKGK- motif. Nef directly recruits the HECT domain E3 ligases AIP4 or NEDD4 to CXCR4 in the resting state. This mechanism was confirmed by ternary interactions of Nef, CXCR4 and AIP4 or NEDD4; by reversal of Nef effect by expression of catalytically inactive AIP4-C830A mutant; and siRNA knockdown of AIP4, NEDD4 or some ESCRT-0 adapters. However, ubiquitinylation dependent lysosomal degradation was not the only mechanism by which Nef downregulated CKRs. Agonist and Nef mediated CXCR2 (and CXCR1) degradation was ubiquitinylation independent. Nef also profoundly downregulated the naturally truncated CXCR4 associated with WHIM syndrome and engineered variants of CXCR4 that resist CXCL12 induced internalization via an ubiquitinylation independent mechanism. 相似文献
106.
The structure of a new triterpene lactone, palustrolide, has been elucidated as 3β,23-dihydroxylupan-13β→28 lactone on the basis of physico-chemical studies. In addition, sitosterol, its glucoside, hederagenin, 16,17-dihydroxykauran-19-oic acid and hederagenic acid have been characterized. 相似文献
107.
T K Sampath J C Maliakal P V Hauschka W K Jones H Sasak R F Tucker K H White J E Coughlin M M Tucker R H Pang 《The Journal of biological chemistry》1992,267(28):20352-20362
We reported previously that a 32-36-kDa osteogenic protein purified from bovine bone matrix is composed of dimers of two members of the transforming growth factor (TGF)-beta superfamily: the bovine equivalent of human osteogenic protein-1 (OP-1) and bone morphogenetic protein-2a, BMP-2a (BMP-2). In the present study, we produced the recombinant human OP-1 (hOP-1) in mammalian cells as a processed mature disulfide-linked homodimer with an apparent molecular weight of 36,000. Examination of hOP-1 in the rat subcutaneous bone induction model demonstrated that hOP-1 was capable of inducing new bone formation with a specific activity comparable with that exhibited by highly purified bovine osteogenic protein preparations. The half-maximal bone-inducing activity of hOP-1 in combination with a rat collagen matrix preparation was 50-100 ng/25 mg of matrix as determined by the calcium content of day 12 implants. Evaluation of hOP-1 effects on cell growth and collagen synthesis in rat osteoblast-enriched bone cell cultures showed that both cell proliferation and collagen synthesis were stimulated in a dose-dependent manner and increased 3-fold in response to 40 ng of hOP-1/ml. Examination of the expression of markers characteristic of the osteoblast phenotype showed that hOP-1 specifically stimulated the induction of alkaline phosphatase (4-fold increase at 40 ng of hOP-1/ml), parathyroid hormone-mediated intracellular cAMP production (4-fold increase at 40 ng of hOP-1/ml), and osteocalcin synthesis (5-fold increase at 25 ng of hOP-1/ml). In long-term (11-17 day) cultures of osteoblasts in the presence of beta-glycerophosphate and L(+)-ascorbate, hOP-1 markedly increased the rate of mineralization as measured by the number of mineral nodules per well (20-fold increase at 20 ng of hOP-1/ml). Direct comparison of TGF-beta 1 and hOP-1 in these bone cell cultures indicated that, although both hOP-1 and TGF-beta 1 promoted cell proliferation and collagen synthesis, only hOP-1 was effective in specifically stimulating markers of the osteoblast phenotype. 相似文献
108.
The present study was designed to evaluate the effect of P. aeruginosa on reproductive potential of male mice via a series of in vitro and in vivo experiments. In vitro studies involved sperm parameters, Mg2+ATPase activity and acrosome status. In vivo study employed male mice which in the right vas deferens received 20?μl of either PBS (Group I) or 104 cfu of P. aeruginosa (Group II). The animals were sacrificed on day 3, 7 and 14 and various parameters viz. body weight, TSI (%), bacterial load, spermiogram {i.e. sperm count, motility (%), viability (%) and morphology}, lipid peroxidation and tissue histopathology were evaluated. The results revealed that cell free supernatant of P. aeruginosa resulted in reduced motility, viability, Mg2+dependent ATPase activity and premature acrosomal loss of mouse spermatozoa in vitro. In vivo study showed that in comparison to group I, group II revealed significant alterations in all the parameters on all the days of sacrifice. Further, when reproductive organs of right and left side of mice in group II were compared, the right side demonstrated more devastating effects in terms of altered TSI (%) of testis and cauda epididymis, higher bacterial counts, azoospermia, increased malondialdehyde levels and severe inflammation in tissue histopathology in comparison to left side where bacteria disseminated in reduced numbers, thereby, resulting in insignificant changes in TSI (%), spermiogram, malondialdehyde levels and tissue histology. This study demonstrates that the colonization of P. aeruginosa in male genital tract could be a risk factor for fertility. 相似文献
109.
Differential expression of soybean cysteine proteinase inhibitor genes during development and in response to wounding and methyl jasmonate. 总被引:13,自引:0,他引:13 下载免费PDF全文
M A Botella Y Xu T N Prabha Y Zhao M L Narasimhan K A Wilson S S Nielsen R A Bressan P M Hasegawa 《Plant physiology》1996,112(3):1201-1210
110.
Musa A Haxhiu Prabha Kc Constance T Moore Sandra S Acquah Christopher G Wilson Syed I Zaidi V John Massari Donald G Ferguson 《Journal of applied physiology》2005,98(6):1961-1982
This review summarizes recent work on two basic processes of central nervous system (CNS) control of cholinergic outflow to the airways: 1) transmission of bronchoconstrictive signals from the airways to the airway-related vagal preganglionic neurons (AVPNs) and 2) regulation of AVPN responses to excitatory inputs by central GABAergic inhibitory pathways. In addition, the autocrine-paracrine modulation of AVPNs is briefly discussed. CNS influences on the tracheobronchopulmonary system are transmitted via AVPNs, whose discharge depends on the balance between excitatory and inhibitory impulses that they receive. Alterations in this equilibrium may lead to dramatic functional changes. Recent findings indicate that excitatory signals arising from bronchopulmonary afferents and/or the peripheral chemosensory system activate second-order neurons within the nucleus of the solitary tract (NTS), via a glutamate-AMPA signaling pathway. These neurons, using the same neurotransmitter-receptor unit, transmit information to the AVPNs, which in turn convey the central command to airway effector organs: smooth muscle, submucosal secretory glands, and the vasculature, through intramural ganglionic neurons. The strength and duration of reflex-induced bronchoconstriction is modulated by GABAergic-inhibitory inputs and autocrine-paracrine controlling mechanisms. Downregulation of GABAergic inhibitory influences may result in a shift from inhibitory to excitatory drive that may lead to increased excitability of AVPNs, heightened airway responsiveness, and sustained narrowing of the airways. Hence a better understanding of these normal and altered central neural circuits and mechanisms could potentially improve the design of therapeutic interventions and the treatment of airway obstructive diseases. 相似文献