全文获取类型
收费全文 | 1541篇 |
免费 | 192篇 |
国内免费 | 2篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 37篇 |
2020年 | 15篇 |
2019年 | 22篇 |
2018年 | 33篇 |
2017年 | 33篇 |
2016年 | 42篇 |
2015年 | 83篇 |
2014年 | 87篇 |
2013年 | 108篇 |
2012年 | 129篇 |
2011年 | 119篇 |
2010年 | 76篇 |
2009年 | 55篇 |
2008年 | 72篇 |
2007年 | 72篇 |
2006年 | 72篇 |
2005年 | 69篇 |
2004年 | 61篇 |
2003年 | 59篇 |
2002年 | 46篇 |
2001年 | 25篇 |
2000年 | 40篇 |
1999年 | 24篇 |
1998年 | 15篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 23篇 |
1990年 | 9篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1973年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有1735条查询结果,搜索用时 15 毫秒
991.
Background
China’s rapidly changing economic landscape has led to widening social inequalities. Occupational status in terms of occupational type and prestige may reflect these socio-structural shifts of social position and be more predictive of self-rated health status than income and education, which may only reflect more gradual acquisitions of social status over time. The goals of this study were to understand the role of occupational status in predicting self-rated health, which is well known to be associated with long-term mortality, as well as compare the occupational status to the other major socioeconomic indicators of income and education.Methods
Data from the 2010 baseline surveys of the China Family Panel Studies, which utilized multi-stage probability sampling with implicit stratification was used. Logistic regression was used to examine the relationship of various socioeconomic indicators (i.e. occupational status, income, and education) with self-rated health as the primary outcome of interest. A series of models considered the associations of occupational category or occupational prestige with self-rated health.Results
The final sample consisted of 14,367 employed adults aged 18–60, which was nationally representative of working adults in China. We found that occupation was not a major predictor of self-rated health in China when age, ethnicity, location, marital status, physical and mental health status were controlled for, with the exception of women working in lower grade management and professional jobs (OR = 1.82, 95% CI: 1.03–3.22). In comparison, income followed by education exhibited greater association with self-rated health. The highest income group had the least probability to report poor health (In men: OR = 0.30, 95% CI: 0.21–0.43. In women: OR = 0.44, 95% CI: 0.26–0.73). People educated with junior high school had better self-rated health than those with primary and below education level (In men: OR = 0.62, 95% CI: 0.50–0.75. In women: OR = 0.53, 95% CI: 0.42–0.68). Income, education and occupation were correlated with each other.Conclusions
Within the context of rapid societal changes in China, income and its implications for greater healthcare access and benefits had the greatest association with self-rated health followed by education. Occupational status was not associated. Occupational categories and prestige should be better adapted to reflect China’s unique sociopolitical and historical context. 相似文献992.
Ching-Yu Lin Feng-Peng Huang Yee Soon Ling Hao-Jan Liang Sheng-Han Lee Mei-Yun Hu Po-Nien Tsao 《PloS one》2015,10(4)
Naphthalene, the most common polycyclic aromatic hydrocarbon, causes airway epithelium injury in mice. Repeated exposure of mice to naphthalene induces airway epithelia that are resistant to further injury. Previous studies revealed that alterations in bioactivation enzymes and increased levels of gamma-glutamylcysteine synthase in the bronchioles protect tolerant mice from naphthalene and its reactive metabolites. In our current study, tolerance was induced in male ICR mice using a total of 7 daily intraperitoneal injections of naphthalene (200 mg/kg). Both naphthalene-tolerant and non-tolerant mice were challenged with a dose of 300 mg/kg naphthalene on day 8 to investigate metabolite differences. The lungs, liver, and kidneys were collected for histopathology 24 h after the challenge dose. Bronchial alveolar lavage fluid (BALF) and both hydrophilic and hydrophobic extracts from each organ were analyzed using nuclear magnetic resonance (NMR)-based metabolomics. The histological results showed no observable injuries to the airway epithelium of naphthalene-tolerant mice when compared with the control. In contrast, airway injuries were observed in mice given a single challenge dose (injury mice). The metabolomics analysis revealed that the energy metabolism in the lungs of tolerant and injury mice was significantly perturbed. However, antioxidant metabolites, such as glutathione and succinate, were significantly increased in the lungs of tolerant mice, suggesting a role for these compounds in the protection of organs from naphthalene-induced electrophilic metabolites and free radicals. Damage to the airway cellular membrane, as shown by histopathological results and increased acetone in the BALF and perturbation of hydrophobic lung extracts, including cholesterol, phosphorylcholine-containing lipids, and fatty acyl chains, were observed in injury mice. Consistent with our histopathological results, fewer metabolic effects were observed in the liver and kidney of mice after naphthalene treatments. In conclusion, NMR-based metabolomics reveals possible mechanisms of naphthalene tolerance and naphthalene-induced toxicity in the respiratory system of mice. 相似文献
993.
Laura E. Yee Francesc R. Garcia-Gonzalo Rachel V. Bowie Chunmei Li Julie K. Kennedy Kaveh Ashrafi Oliver E. Blacque Michel R. Leroux Jeremy F. Reiter 《PLoS genetics》2015,11(11)
Mutations in genes encoding cilia proteins cause human ciliopathies, diverse disorders affecting many tissues. Individual genes can be linked to ciliopathies with dramatically different phenotypes, suggesting that genetic modifiers may participate in their pathogenesis. The ciliary transition zone contains two protein complexes affected in the ciliopathies Meckel syndrome (MKS) and nephronophthisis (NPHP). The BBSome is a third protein complex, affected in the ciliopathy Bardet-Biedl syndrome (BBS). We tested whether mutations in MKS, NPHP and BBS complex genes modify the phenotypic consequences of one another in both C. elegans and mice. To this end, we identified TCTN-1, the C. elegans ortholog of vertebrate MKS complex components called Tectonics, as an evolutionarily conserved transition zone protein. Neither disruption of TCTN-1 alone or together with MKS complex components abrogated ciliary structure in C. elegans. In contrast, disruption of TCTN-1 together with either of two NPHP complex components, NPHP-1 or NPHP-4, compromised ciliary structure. Similarly, disruption of an NPHP complex component and the BBS complex component BBS-5 individually did not compromise ciliary structure, but together did. As in nematodes, disrupting two components of the mouse MKS complex did not cause additive phenotypes compared to single mutants. However, disrupting both Tctn1 and either Nphp1 or Nphp4 exacerbated defects in ciliogenesis and cilia-associated developmental signaling, as did disrupting both Tctn1 and the BBSome component Bbs1. Thus, we demonstrate that ciliary complexes act in parallel to support ciliary function and suggest that human ciliopathy phenotypes are altered by genetic interactions between different ciliary biochemical complexes. 相似文献
994.
Sequential Processing for Organic Photovoltaics: Design Rules for Morphology Control by Tailored Semi‐Orthogonal Solvent Blends 下载免费PDF全文
Jordan C. Aguirre Steven A. Hawks Amy S. Ferreira Patrick Yee Selvam Subramaniyan Samson A. Jenekhe Sarah H. Tolbert Benjamin J. Schwartz 《Liver Transplantation》2015,5(11)
Design rules are presented for significantly expanding sequential processing (SqP) into previously inaccessible polymer:fullerene systems by tailoring binary solvent blends for fullerene deposition. Starting with a base solvent that has high fullerene solubility, 2‐chlorophenol (2‐CP), ellipsometry‐based swelling experiments are used to investigate different co‐solvents for the fullerene‐casting solution. By tuning the Flory‐Huggins χ parameter of the 2‐CP/co‐solvent blend, it is possible to optimally swell the polymer of interest for fullerene interdiffusion without dissolution of the polymer underlayer. In this way solar cell power conversion efficiencies are obtained for the PTB7 (poly[(4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)(3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl)]) and PC61BM (phenyl‐C61‐butyric acid methyl ester) materials combination that match those of blend‐cast films. Both semicrystalline (e.g., P3HT (poly(3‐hexylthiophene‐2,5‐diyl)) and entirely amorphous (e.g., PSDTTT (poly[(4,8‐di(2‐butyloxy)benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)‐alt‐(2,5‐bis(4,4′‐bis(2‐octyl)dithieno[3,2‐b:2′3′‐d]silole‐2,6‐diyl)thiazolo[5,4‐d]thiazole)]) conjugated polymers can be processed into highly efficient photovoltaic devices using the solvent‐blend SqP design rules. Grazing‐incidence wide‐angle x‐ray diffraction experiments confirm that proper choice of the fullerene casting co‐solvent yields well‐ordered interdispersed bulk heterojunction (BHJ) morphologies without the need for subsequent thermal annealing or the use of trace solvent additives (e.g., diiodooctane). The results open SqP to polymer/fullerene systems that are currently incompatible with traditional methods of device fabrication, and make BHJ morphology control a more tractable problem. 相似文献
995.
996.
Dino Samartzis Yee Leung Hideki Shigematsu Deepa Natarajan Oliver Stokes Kin-Cheung Mak Guanfeng Yao Keith D. K. Luk Kenneth M. C. Cheung 《PloS one》2015,10(8)
ObjectiveSelecting fusion levels based on the Luk et al criteria for operative management of thoracic adolescent idiopathic scoliosis (AIS) with hook and hybrid systems yields acceptable curve correction and balance parameters; however, it is unknown whether utilizing a purely pedicle screw strategy is effective. Utilizing the fulcrum bending radiographic (FBR) to assess curve flexibility to select fusion levels, the following study assessed the efficacy of pedicle screw fixation with alternate level screw strategy (ALSS) for thoracic AIS.MethodsA retrospective study with prospective radiographic data collection/analyses (preoperative, postoperative 1-week and minimum 2-year follow-up) of 28 operative thoracic AIS patients undergoing ALSS was performed. Standing coronal/sagittal and FBR Cobb angles, FBR flexibility, fulcrum bending correction index (FBCI), trunkal shift, radiographic shoulder height (RSH), and list were assessed on x-rays. Fusion level selection was based on the Luk et al criteria and compared to conventional techniques.ResultsIn the primary curve, the mean preoperative and postoperative 1 week and last follow-up standing coronal Cobb angles were 59.9, 17.2 and 20.0 degrees, respectively. Eighteen patients (64.3%) had distal levels saved (mean: 1.6 levels) in comparison to conventional techniques. Mean immediate and last follow-up FBCIs were 122.6% and 115.0%, respectively. Sagittal alignment did not statistically differ between any assessment intervals (p>0.05). A decrease in trunkal shift was noted from preoperative to last follow-up (p = 0.003). No statistically significant difference from preoperative to last follow-up was noted in RSH and list (p>0.05). No "add-on" of other vertebra or decompensation was noted and all patients achieved fusion.ConclusionsThis is the first report to note that using the FBR for decision-making in selecting fusion levels in thoracic AIS patients undergoing management with pedicle screw constructs (e.g. ALSS) is a cost-effective strategy that can achieve clinically-relevant deformity correction that is maintained and without compromising fusion levels. 相似文献
997.
998.
Mendel D Marquart AL Joseph S Waid P Yee YK Tebbe AL Ratz AM Herron DK Goodson T Masters JJ Franciskovich JB Tinsley JM Wiley MR Weir LC Kyle JA Klimkowski VJ Smith GF Towner RD Froelich LL Buben J Craft TJ 《Bioorganic & medicinal chemistry letters》2007,17(17):4832-4836
SAR about the B-ring of a series of N(2)-aroyl anthranilamide factor Xa (fXa) inhibitors is described. B-ring o-aminoalkylether and B-ring p-amine probes of the S1' and S4 sites, respectively, afforded picomolar fXa inhibitors that performed well in in vitro anticoagulation assays. 相似文献
999.
Solution structure of the hypothetical protein TA0095 from Thermoplasma acidophilum: a novel superfamily with a two-layer sandwich architecture 下载免费PDF全文
León E Yee A Ortíz AR Santoro J Rico M Jiménez MA 《Protein science : a publication of the Protein Society》2007,16(10):2278-2286
TA0095 is a 96-residue hypothetical protein from Thermoplasma acidophilum that exhibits no sequence similarity to any protein of known structure. Also, TA0095 is a member of the COG4004 orthologous group of unknown function found in Archaea bacteria. We determined its three-dimensional structure by NMR methods. The structure displays an alpha/beta two-layer sandwich architecture formed by three alpha-helices and five beta-strands following the order beta1-alpha1-beta2-beta3-beta4-beta5-alpha2-alpha3. Searches for structural homologs indicate that the TA0095 structure belongs to the TBP-like fold, constituting a novel superfamily characterized by an additional C-terminal helix. The TA0095 structure provides a fold common to the COG4004 proteins that will obviously belong to this new superfamily. Most hydrophobic residues conserved in the COG4004 proteins are buried in the structure determined herein, thus underlying their importance for structure stability. Considering that the TA0095 surface shows a large positively charged patch with a high degree of residue conservation within the COG4004 domain, the biological function of TA0095 and the rest of COG4004 proteins might occur through binding a negatively charged molecule. Like other TBP-like fold proteins, the COG4004 proteins might be DNA-binding proteins. The fact that TA0095 is shown to interact with large DNA fragments is in favor of this hypothesis, although nonspecific DNA binding cannot be ruled out. 相似文献
1000.
Kwok KO Leung GM Lam WY Riley S 《Proceedings. Biological sciences / The Royal Society》2007,274(1610):611-617
Two factors dominated the epidemiology of severe acute respiratory syndrome (SARS) during the 2002-2003 global outbreak, namely super-spreading events (SSE) and hospital infections. Although both factors were important during the first and the largest hospital outbreak in Hong Kong, the relative importance of different routes of infection has not yet been quantified. We estimated the parameters of a novel mathematical model of hospital infection using SARS episode data. These estimates described levels of transmission between the index super-spreader, staff and patients, and were used to compare three plausible hypotheses. The broadest of the supported hypotheses ascribes the initial surge in cases to a single super-spreading individual and suggests that the per capita risk of infection to patients increased approximately one month after the start of the outbreak. Our estimate for the number of cases caused by the SSE is substantially lower than the previously reported values, which were mostly based on self-reported exposure information. This discrepancy suggests that the early identification of the index case as a super-spreader might have led to biased contact tracing, resulting in too few cases being attributed to staff-to-staff transmission. We propose that in future outbreaks of SARS or other directly transmissible respiratory pathogens, simple mathematical models could be used to validate preliminary conclusions concerning the relative importance of different routes of transmission with important implications for infection control. 相似文献