全文获取类型
收费全文 | 406篇 |
免费 | 11篇 |
专业分类
417篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 21篇 |
2014年 | 17篇 |
2013年 | 23篇 |
2012年 | 25篇 |
2011年 | 30篇 |
2010年 | 15篇 |
2009年 | 8篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 22篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 19篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有417条查询结果,搜索用时 15 毫秒
61.
Danuta Dudek-Adamska Teresa Lech Tomasz Konopka Paweł Kościelniak 《Biological trace element research》2018,186(2):370-378
Recently, considerable attention has been paid to the negative effects caused by the presence and constant increase in concentration of heavy metals in the environment, as well as to the determination of their content in human biological samples. In this paper, the concentration of chromium in samples of blood and internal organs collected at autopsy from 21 female and 39 male non-occupationally exposed subjects is presented. Elemental analysis was carried out by an electrothermal atomic absorption spectrometer after microwave-assisted acid digestion. Reference ranges of chromium in the blood, brain, stomach, liver, kidneys, lungs, and heart (wet weight) in the population of Southern Poland were found to be 0.11–16.4 ng/mL, 4.7–136 ng/g, 6.1–76.4 ng/g, 11–506 ng/g, 2.9–298 ng/g, 13–798 ng/g, and 3.6–320 ng/g, respectively. 相似文献
62.
Charan Gowda Glen A Toomayan Wen-Ning Qi Long-En Chen Yongting Cai Diane M Allen Anthony V Seaber James R Urbaniak 《Nitric oxide》2004,11(1):17-24
N(omega)-Propyl-L-arginine (NPA) is reported to be a highly selective inhibitor of neuronal nitric oxide synthase (nNOS). This in vivo study observed its role in ischemia/reperfusion (I/R) injury in rat skeletal muscle. Our results showed that NPA infusion significantly increased vessel diameters and blood flow in reperfused cremaster muscle, and slightly increased contractile function in reperfused extensor digitorum longus (EDL) muscle. In addition, NPA treatment slightly increased I/R-mediated downregulation of nNOS and eNOS mRNA and protein levels. Although NPA showed a beneficial role in I/R injury, our in vivo data do not support NPA as a selective nNOS inhibitor. Also, our data do not provide any insight into the mechanism of NPA. Thus, the in vivo mechanism of action of NPA needs to be further identified, and the role of nNOS in skeletal muscle I/R still remains to be determined. 相似文献
63.
Dariusz Jakubas Katarzyna Wojczulanis-Jakubas Rafal Boehnke Dorota Kidawa Katarzyna Błachowiak-Samołyk Lech Stempniewicz 《Polar Biology》2016,39(9):1547-1561
Different phenological responses to climate changes by species representing preys and predators may lead to mismatch between functionally dependent components of an ecosystem, with important effects on its structure and functioning. Here, we investigate within-season variation in zooplankton availability, chick diet composition and breeding performance of a small planktivorous seabird, the little auk (Alle alle) in two large colonies in Hornsund and Magdalenefjorden, Spitsbergen, differing in synchrony of breeding (11-day vs. 22-day hatching period, respectively). Assuming similar zooplankton phenology and existing differences in duration of the little auk breeding period, we expected lower availability of the preferred food in the less synchronized colony in Magdalenefjorden and in consequence a negative effect on nestling body mass and survival. We found that in both colonies Calanus glacialis (copepodite stage CV) was the most important prey item in the chick diet making up 68–87 % of the biomass and energy of all prey items. The only exception was the end of the chick-rearing period in Magdalenefjorden, when contribution of this prey item was significantly lower (24–26 %). Thus, late breeders in Magdalenefjorden were apparently mismatched regarding C. glacialis CV availability. However, the hatching date did not affect birds fitness (reproductive output and chick pre-fledging mass) significantly. Results of our study indicate that little auks breeding on Spitsbergen can respond to a wide range of environmental conditions and prey availabilities through the plasticity of their foraging behaviour, which may help them to maintain their optimum fitness level in changing and unpredictable environments. 相似文献
64.
Makowska J Rodziewicz-Motowidlo S Baginska K Makowski M Vila JA Liwo A Chmurzynski L Scheraga HA 《Biophysical journal》2007,92(8):2904-2917
It has been suggested that the alanine-based peptide with sequence Ac-XX-[A](7)-OO-NH(2), termed XAO where X denotes diaminobutyric acid and O denotes ornithine, exists in a predominantly polyproline-helix (P(II)) conformation in aqueous solution. In our recent work, we demonstrated that this "polyproline conformation" should be regarded as a set of local conformational states rather than as the overall conformation of the molecule. In this work, we present further evidence to support this statement. Differential scanning calorimetry measurements showed only a very small peak in the heat capacity of an aqueous solution of XAO at 57 degrees C, whereas the suggested transition to the P(II) structure should occur at approximately 30 degrees C. We also demonstrate that the temperature dependence of the (3)J(HNHalpha) coupling constants of the alanine residues can be explained qualitatively in terms of Boltzmann averaging over all local conformational states; therefore, this temperature dependence proves that a conformational transition does not occur. Canonical MD simulations with the solvent represented by the generalized Born model, and with time-averaged NMR-derived restraints, demonstrate the presence of an ensemble of structures with a substantial amount of local P(II) conformational states but not with an overall P(II) conformation. 相似文献
65.
Purification of glycomacropeptide from non-dialyzable fraction of sweet whey by anion-exchange chromatography 总被引:3,自引:0,他引:3
Glycomacropeptide (GMP) was purified from non-dialyzable fraction of sweet whey by anion-exchange chromatography on DEAE-Sephacel at two pHs 6.4 and 3.0. Chromatography at pH 3.0 (but not pH 6.4) gave a GMP fraction of high purity with its yield (1 g from every litre of whey) being approximately 100 times higher than that shown in the previous report. It was concluded that DEAE-Sephacel chromatography at pH 3.0 is a simple useful method to separate GMP from most whey proteins. It may be applicable to a large scale production of GMP. 相似文献
66.
The concentration of cadmium in human tissues obtained on the basis of autopsies of non-poisoned Polish people (n = 150), aged from 1 to 80 years, examined between 1990 and 2010, is presented. The following values were found in wet digested samples by flame atomic absorption spectrometry (FAAS) (mean ± SD, median, and range, μg/g of wet weight): brain 0.020 ± 0.031, 0.084, 0–0.120 (n = 41); stomach 0.148 ± 0.195, 0.084, 0–1.25 (n = 89); small intestine 0.227 ± 0.231, 0.130, 0–0.830 (n = 39); liver 1.54 ± 1.55, 1.01, 0.015–9.65 (n = 99); kidney 16.0 ± 13.2, 14.0, 0.62–61.3 (n = 91); lung 0.304 ± 0.414, 0.130, 0–1.90 (n = 25); and heart 0.137 ± 0.107, 0.140, 0.017–0.250 (n = 4). Additionally, results (n = 13 people, aged from 2 to 83 years, 63 samples) obtained by inductively coupled plasma optical emission spectrometry (ICP OES) between 2010 and 2015 are given. The obtained data on Cd concentration in the human body can be used to estimate the amounts occurring in “healthy” people and those occurring in cases of chronic or acute poisonings with Cd compounds, which are examined for forensic purposes or to assess environmental exposure levels. 相似文献
67.
Camilla Urbaniak Joanne Cummins Muriel Brackstone Jean M. Macklaim Gregory B. Gloor Chwanrow K. Baban Leslie Scott Deidre M. O'Hanlon Jeremy P. Burton Kevin P. Francis Mark Tangney Gregor Reid 《Applied and environmental microbiology》2014,80(10):3007-3014
In recent years, a greater appreciation for the microbes inhabiting human body sites has emerged. In the female mammary gland, milk has been shown to contain bacterial species, ostensibly reaching the ducts from the skin. We decided to investigate whether there is a microbiome within the mammary tissue. Using 16S rRNA sequencing and culture, we analyzed breast tissue from 81 women with and without cancer in Canada and Ireland. A diverse population of bacteria was detected within tissue collected from sites all around the breast in women aged 18 to 90, not all of whom had a history of lactation. The principal phylum was Proteobacteria. The most abundant taxa in the Canadian samples were Bacillus (11.4%), Acinetobacter (10.0%), Enterobacteriaceae (8.3%), Pseudomonas (6.5%), Staphylococcus (6.5%), Propionibacterium (5.8%), Comamonadaceae (5.7%), Gammaproteobacteria (5.0%), and Prevotella (5.0%). In the Irish samples the most abundant taxa were Enterobacteriaceae (30.8%), Staphylococcus (12.7%),
Listeria welshimeri (12.1%), Propionibacterium (10.1%), and Pseudomonas (5.3%). None of the subjects had signs or symptoms of infection, but the presence of viable bacteria was confirmed in some samples by culture. The extent to which these organisms play a role in health or disease remains to be determined. 相似文献
68.
Mrózek L Dvořáková L Mandelová Z Rárová L Řezáčová A Plaček L Opatřilová R Dohnal J Paleta O Král V Drašar P Jampílek J 《Steroids》2011,76(10-11):1082-1097
Skin penetration enhancers are used in the formulation of transdermal delivery systems for drugs that are otherwise not sufficiently skin-permeable. Intestinal absorption promoters/enhancers are used as excipients in oral formulations of poorly oral-bioavailable drugs. Series of fourteen acyloxy derivatives of 5β-cholic acid as potential drug absorption modifiers was generated by multistep synthesis. The synthesis of all newly prepared compounds is presented here. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (R(M)) was determined. The hydrophobicity (logP) and solubility (logS) of the studied compounds were also calculated using two commercially available programs. All the target compounds were tested for their in vitro transdermal penetration activity and as potential intestinal absorption enhancers. The anti-proliferative activity of all the final compounds was also assessed against the human cancer cell lines: T-lymphoblastic leukemia cell line and the breast adenocarcinoma cell line. Their cytotoxicity was also evaluated against the normal human skin fibroblast cells. Two compounds showed anti-proliferative effect on cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC(50)>37 μM), indicating they would have low cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effects are discussed in this article. 相似文献
69.
Sławomir Borek Szymon Kubala Sylwia Kubala Lech Ratajczak 《Acta Physiologiae Plantarum》2011,33(5):1953-1968
Storage lipid and protein breakdown in germinating seeds of yellow (Lupinus luteus L.), white (L. albus L.), and Andean lupine (L. mutabilis Sweet) and regulatory function of sucrose were investigated. Less oil bodies were detected in organs of yellow lupine seeds,
whereas the highest content of oil bodies was noticed in the Andean lupine seeds. Mature, air-dried yellow, white and Andean
lupine seeds do not contain starch. Starch grains appear the earliest in white lupine seeds during imbibition. Sucrose deficiency
in tissues enhances breakdown of storage lipid, protein and temporary starch in cotyledons. In sucrose starved embryo axes
of all investigated lupine species, an increased level of vacuolization was noted. Interconnections between catabolism of
storage protein and storage lipid in germinating lupine seeds were identified by applying 14C-acetate. To assess the importance of key processes in storage lipid breakdown NaF (inhibitor of glycolysis and gluconeogenesis),
KCN, NaN3 and SHAM (inhibitors of mitochondrial electron transport chain) and MSO (inhibitor of glutamine synthetase) were used. Radioactivity
coming from 14C-acetate was released as 14CO2 but mostly was incorporated into ethanol-soluble fraction of embryo axes and cotyledons. Respiratory inhibitors caused a
significant decrease in 14CO2 and ethanol fractions in all three lupine species studied. MSO stimulated release of 14CO2 and radioactivity of ethanol fractions in yellow lupine organs fed with sucrose, but in Andean lupine MSO enhanced the production
of 14CO2 and radioactivity of ethanol fractions both in organs fed and not fed with sucrose. Different strategies of storage compound
breakdown are proposed, depending on relative proportion in storage protein and lipid content in lupine seeds. 相似文献
70.
Dobrzycka B Terlikowski SJ Garbowicz M Niklinski J Chyczewski L Kulikowski M 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2011,49(4):631-635
The objective of this study was to verify the frequency of P53 and BCL-2 immunohistochemical expression in 98 patients with endometrial carcinoma, and to correlate it with clinical stage and patient survival. A significant difference was found regarding the frequency of P53 expression when comparing type I and II tumors (23.7% and 54.5%, respectively; p = 0.006). A positive correlation was observed between P53 immunoexpression and patient survival in type I and II tumors (p = 0.009 and p = 0.036, respectively). BCL-2 expression was significantly more frequent in early clinical stages in both types of endometrial cancer (p 〈 0.001 and 0.002) and correlated with a decrease in overall survival in type I endometrial cancer (p = 0.014). Thus, the prognostic value of these biomarkers in endometrial cancer needs to be further investigated. 相似文献