全文获取类型
收费全文 | 1728篇 |
免费 | 153篇 |
专业分类
1881篇 |
出版年
2019年 | 18篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 30篇 |
2015年 | 41篇 |
2014年 | 46篇 |
2013年 | 63篇 |
2012年 | 69篇 |
2011年 | 64篇 |
2010年 | 42篇 |
2009年 | 37篇 |
2008年 | 56篇 |
2007年 | 53篇 |
2006年 | 57篇 |
2005年 | 62篇 |
2004年 | 56篇 |
2003年 | 59篇 |
2002年 | 60篇 |
2001年 | 31篇 |
2000年 | 64篇 |
1999年 | 45篇 |
1998年 | 28篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1993年 | 23篇 |
1992年 | 27篇 |
1991年 | 33篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1980年 | 15篇 |
1979年 | 25篇 |
1977年 | 17篇 |
1976年 | 21篇 |
1975年 | 18篇 |
1974年 | 24篇 |
1973年 | 19篇 |
1972年 | 21篇 |
1971年 | 19篇 |
1970年 | 18篇 |
1969年 | 20篇 |
1968年 | 20篇 |
1961年 | 15篇 |
排序方式: 共有1881条查询结果,搜索用时 15 毫秒
61.
Pieper R Gatlin CL Makusky AJ Russo PS Schatz CR Miller SS Su Q McGrath AM Estock MA Parmar PP Zhao M Huang ST Zhou J Wang F Esquer-Blasco R Anderson NL Taylor J Steiner S 《Proteomics》2003,3(7):1345-1364
Plasma, the soluble component of the human blood, is believed to harbor thousands of distinct proteins, which originate from a variety of cells and tissues through either active secretion or leakage from blood cells or tissues. The dynamic range of plasma protein concentrations comprises at least nine orders of magnitude. Proteins involved in coagulation, immune defense, small molecule transport, and protease inhibition, many of them present in high abundance in this body fluid, have been functionally characterized and associated with disease processes. For example, protein sequence mutations in coagulation factors cause various serious disease states. Diagnosing and monitoring such diseases in blood plasma of affected individuals has typically been conducted by use of enzyme-linked immunosorbent assays, which using a specific antibody quantitatively measure only the affected protein in the tested plasma samples. The discovery of protein biomarkers in plasma for diseases with no known correlations to genetic mutations is challenging. It requires a highly parallel display and quantitation strategy for proteins. We fractionated blood serum proteins prior to display on two-dimensional electrophoresis (2-DE) gels using immunoaffinity chromatography to remove the most abundant serum proteins, followed by sequential anion-exchange and size-exclusion chromatography. Serum proteins from 74 fractions were displayed on 2-DE gels. This approach succeeded in resolving approximately 3700 distinct protein spots, many of them post-translationally modified variants of plasma proteins. About 1800 distinct serum protein spots were identified by mass spectrometry. They collapsed into 325 distinct proteins, after sequence homology and similarity searches were carried out to eliminate redundant protein annotations. Although a relatively insensitive dye, Coomassie Brilliant Blue G-250, was used to visualize protein spots, several proteins known to be present in serum in < 10 ng/mL concentrations were identified such as interleukin-6, cathepsins, and peptide hormones. Considering that our strategy allows highly parallel protein quantitation on 2-DE gels, it holds promise to accelerate the discovery of novel serum protein biomarkers. 相似文献
62.
63.
The interchain disulfide bonds of a human pathological immunoglobulin 总被引:12,自引:0,他引:12
64.
Malte Steiner David Volkheimer Nicholaus Meyers Tim Wehner Hans-Joachim Wilke Lutz Claes Anita Ignatius 《PloS one》2015,10(3)
For ex vivo measurements of fracture callus stiffness in small animals, different test methods, such as torsion or bending tests, are established. Each method provides advantages and disadvantages, and it is still debated which of those is most sensitive to experimental conditions (i.e. specimen alignment, directional dependency, asymmetric behavior). The aim of this study was to experimentally compare six different testing methods regarding their robustness against experimental errors. Therefore, standardized specimens were created by selective laser sintering (SLS), mimicking size, directional behavior, and embedding variations of respective rat long bone specimens. For the latter, five different geometries were created which show shifted or tilted specimen alignments. The mechanical tests included three-point bending, four-point bending, cantilever bending, axial compression, constrained torsion, and unconstrained torsion. All three different bending tests showed the same principal behavior. They were highly dependent on the rotational direction of the maximum fracture callus expansion relative to the loading direction (creating experimental errors of more than 60%), however small angular deviations (<15°) were negligible. Differences in the experimental results between the bending tests originate in their respective location of maximal bending moment induction. Compared to four-point bending, three-point bending is easier to apply on small rat and mouse bones under realistic testing conditions and yields robust measurements, provided low variation of the callus shape among the tested specimens. Axial compressive testing was highly sensitive to embedding variations, and therefore cannot be recommended. Although it is experimentally difficult to realize, unconstrained torsion testing was found to be the most robust method, since it was independent of both rotational alignment and embedding uncertainties. Constrained torsional testing showed small errors (up to 16.8%, compared to corresponding alignment under unconstrained torsion) due to a parallel offset between the specimens’ axis of gravity and the torsional axis of rotation. 相似文献
65.
The Neusiedler See – Seewinkel National Park area is confronted with a remarkable increase in tourism and recreational activities during the last years. The “Koppel” area, situated on the eastern shore of the lake, is one of the most important breeding sites for Greylag Geese. Behaviour and distribution of the geese on the breeding site as well as touristic activities on the adjacent road leading along the Koppel were examined to investigate relations and interactions between the Greylag Goose population and tourism. Taking into account the excellent weather and breeding conditions in the year 2000 the results of the survey indicate a stable or even rising Greylag population, increasing numbers of visitors and high disturbance frequencies in the vicinity of the study area. The number of disturbances on the adjacent road seems to affect the suitability of the site in general, leading to a specific temporal and spatial distribution of the birds, whereas different disturbance qualities result in changes of the birds behaviour. 相似文献
66.
Oshry Markovich Evyatar Steiner Štěpán Kouřil Petr Tarkowski Asaph Aharoni Rivka Elbaum 《Plant, cell & environment》2017,40(7):1189-1196
Silicate minerals are dominant soil components. Thus, plant roots are constantly exposed to silicic acid. High silicon intake, enabled by root silicon transporters, correlates with increased tolerance to many biotic and abiotic stresses. However, the underlying protection mechanisms are largely unknown. Here, we tested the hypothesis that silicon interacts with the plant hormones, and specifically, that silicic acid intake increases cytokinin biosynthesis. The reaction of sorghum (Sorghum bicolor) and Arabidopsis plants, modified to absorb high versus low amounts of silicon, to dark‐induced senescence was monitored, by quantifying expression levels of genes along the senescence pathway and measuring tissue cytokinin levels. In both species, detached leaves with high silicon content senesced more slowly than leaves that were not exposed to silicic acid. Expression levels of genes along the senescence pathway suggested increased cytokinin biosynthesis with silicon exposure. Mass spectrometry measurements of cytokinin suggested a positive correlation between silicon exposure and active cytokinin concentrations. Our results indicate a similar reaction to silicon treatment in distantly related plants, proposing a general function of silicon as a stress reliever, acting via increased cytokinin biosynthesis. 相似文献
67.
Danilo ML Prado Fabiana B Benatti Ana L de Sá-Pinto Ana P Hayashi Bruno Gualano Rosa MR Pereira Adriana ME Sallum Eloisa Bonfá Clovis A Silva Hamilton Roschel 《Arthritis research & therapy》2013,15(2):R46
Introduction
Exercise training has emerged as a promising therapeutic strategy to counteract physical dysfunction in adult systemic lupus erythematosus. However, no longitudinal studies have evaluated the effects of an exercise training program in childhood-onset systemic lupus erythematosus (C-SLE) patients. The objective was to evaluate the safety and the efficacy of a supervised aerobic training program in improving the cardiorespiratory capacity in C-SLE patients.Methods
Nineteen physically inactive C-SLE patients were randomly assigned into two groups: trained (TR, n = 10, supervised moderate-intensity aerobic exercise program) and non-trained (NT, n = 9). Gender-, body mass index (BMI)- and age-matched healthy children were recruited as controls (C, n = 10) for baseline (PRE) measurements only. C-SLE patients were assessed at PRE and after 12 weeks of training (POST). Main measurements included exercise tolerance and cardiorespiratory measurements in response to a maximal exercise (that is, peak VO2, chronotropic reserve (CR), and the heart rate recovery (ΔHRR) (that is, the difference between HR at peak exercise and at both the first (ΔHRR1) and second (ΔHRR2) minutes of recovery after exercise).Results
The C-SLE NT patients did not present changes in any of the cardiorespiratory parameters at POST (P > 0.05). In contrast, the exercise training program was effective in promoting significant increases in time-to-exhaustion (P = 0.01; ES = 1.07), peak speed (P = 0.01; ES = 1.08), peak VO2 (P = 0.04; ES = 0.86), CR (P = 0.06; ES = 0.83), and in ΔHRR1 and ΔHRR2 (P = 0.003; ES = 1.29 and P = 0.0008; ES = 1.36, respectively) in the C-SLE TR when compared with the NT group. Moreover, cardiorespiratory parameters were comparable between C-SLE TR patients and C subjects after the exercise training intervention, as evidenced by the ANOVA analysis (P > 0.05, TR vs. C). SLEDAI-2K scores remained stable throughout the study.Conclusion
A 3-month aerobic exercise training was safe and capable of ameliorating the cardiorespiratory capacity and the autonomic function in C-SLE patients.Trial registration
NCT01515163. 相似文献68.
Towards a framework for the evolutionary genomics of Kinetoplastids: what kind of data and how much?
The current status of kinetoplastids phylogeny and evolution is discussed in view of the recent progresses on genomics. Some ideas on a potential framework for the evolutionary genomics of kinetoplastids are presented. 相似文献
69.
Rizky Pasthika Kirana Kumar Gaurav Sanu Arora Gerlinde Wiesenberger Maria Doppler Sebastian Michel Simone Zimmerl Magdalena Matic Chinedu E. Eze Mukesh Kumar Ajla Topuz Marc Lemmens Rainer Schuhmacher Gerhard Adam Brande B. H. Wulff Hermann Buerstmayr Barbara Steiner 《Plant biotechnology journal》2023,21(1):109-121
Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley. 相似文献
70.
Amino-terminal sequences of the L, M, and H subunits of reaction centers from the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26 总被引:7,自引:0,他引:7
We have determined the sequence of the 25-28 amino-terminal residues of the three subunits, L, M, and H, of the membrane-bound reaction center protein of the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26. The sequences are as follows: L, H2N-Ala-Leu-Leu-Ser-Phe-Glu-Arg-Lys-Tyr-Arg- Val-Pro-Gly-Gly-Thr-Leu-Val-Gly-Gly-Asn-Leu-Phe-Asp-Phe-(His)-Val-; M, H2N-Ala-Glu-Tyr-Gln-Asn-Ile-Phe-Ser-Gln-Val-Gln-Val-Arg-Gly-Pro-Ala-Asp-Leu-Gly-Met-Thr-Glu-Asp-Val-Asn-Leu-Ala-Asn-; H, H2N-Met-Val-Gly-Val-Thr-Ala-Phe-Gly-Asn-Phe-Asp-Leu-Ala-Ser-Leu-Ala-Ile-Tyr-Ser-Phe-Trp-Ile-Phe-Leu-Ala-X-Leu-Ile-. The H sequence, especially after the aspartyl residue at position 11, is rich in hydrophobic residues, consistent with the possibility that this section of the polypeptide chain is located within the membrane. The L sequence is hydrophilic near the amino terminus and then becomes moderately hydrophobic. The M sequence is of average polarity. 相似文献