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排序方式: 共有479条查询结果,搜索用时 15 毫秒
61.
62.
Aleksandra Pawlak Witold Gładkowski Justyna Kutkowska Marcelina Mazur Bożena Obmińska-Mrukowicz Andrzej Rapak 《Bioorganic & medicinal chemistry letters》2018,28(7):1171-1177
For many years, studies focused on developing new natural or synthetic compounds with antineoplastic activity have attracted the attention of researchers. An interesting group of such compounds seem to be those with both lactone moiety and an aromatic ring which, in addition to antimicrobial or antiviral activity, also exhibit antitumor properties. The study shows antitumor activity of two enantiomeric trans isomers of 5-(1-iodoethyl)-4-(2′,5′-dimethylphenyl)dihydrofuran-2-one. Our aim was to determine their antitumor activity manifested as an ability to induce apoptosis in selected canine cancer cell lines as well as to evaluate differences in their strength depending on the configuration of their stereogenic centers. The enantiomers (+)-(4R,5S,6R)-1 and (?)-(4S,5R,6S)-2 were found to induce classical caspase-dependent apoptosis through downregulation of the expression of anti-apoptotic proteins Bcl-xL and Bcl-2. Although the mechanism of apoptosis induction was the same for both enantiomers, they differed in their strength, as stronger antineoplastic activity in vitro was exhibited by isomer (+)-(4R,5S,6R)-1. 相似文献
63.
Witold Wachowiak Annika Perry Kevin Donnelly Stephen Cavers 《Ecology and evolution》2018,8(1):655-666
Closely related taxa occupying different environments are valuable systems for studying evolution. In this study, we examined differences in early phenology (bud set, bud burst) and early growth in a common garden trial of closely related pine species: Pinus sylvestris, P. mugo, and P. uncinata. Seeds for the trial were sourced from populations across the ranges of each species in Europe. Over first 4 years of development, clear differences were observed between species, while the most significant intraspecific differentiation was observed among plants from P. sylvestris populations from continental European locations. Trait differences within P. sylvestris were highly correlated with altitude and latitude of the site of origin. Meanwhile, P. mugo populations from the Carpathians had the earliest bud set and bud flush compared to other populations of the species. Overall, populations from the P. mugo complex from heterogeneous mountain environments and P. sylvestris from the Scottish Highlands showed the highest within‐population variation for the focal traits. Although the three species have been shown to be genetically highly similar, this study reveals large differences in key adaptive traits both among and within species. 相似文献
64.
Marcin Miłkowski Witold M. Hensel Mateusz Hohol 《Journal of computational neuroscience》2018,45(3):163-172
Replicability and reproducibility of computational models has been somewhat understudied by “the replication movement.” In this paper, we draw on methodological studies into the replicability of psychological experiments and on the mechanistic account of explanation to analyze the functions of model replications and model reproductions in computational neuroscience. We contend that model replicability, or independent researchers' ability to obtain the same output using original code and data, and model reproducibility, or independent researchers' ability to recreate a model without original code, serve different functions and fail for different reasons. This means that measures designed to improve model replicability may not enhance (and, in some cases, may actually damage) model reproducibility. We claim that although both are undesirable, low model reproducibility poses more of a threat to long-term scientific progress than low model replicability. In our opinion, low model reproducibility stems mostly from authors' omitting to provide crucial information in scientific papers and we stress that sharing all computer code and data is not a solution. Reports of computational studies should remain selective and include all and only relevant bits of code. 相似文献
65.
Witold Kozak Marianna Rajchert-Trzpil Jolanta Zajdel W?adys?aw T. Dobrzański 《Applied microbiology》1973,25(2):305-308
Eighty-seven strains of lactic streptococci (46 of Streptococcus lactis, 24 of S. diacetilactis, and 17 of S. cremoris) were tested for lysogeny; 12 S. lactis strains produced nisin. Lysogeny was found in five S. lactis strains (two of them were nisin producers) and in two S. diacetilactis strains. Four S. lactis and two S. diacetilactis lysogens liberated phages both spontaneously and after ultraviolet treatment, and one S. lactis strain liberated phages spontaneously only. No lysogens were found among the S. cremoris strains tested. An initial characterization of the lysogens and their phages was made. The lytic spectrum of some of the examined phages was very narrow (homospecific), whereas that of others was wide, including strains of the three investigated species. 相似文献
66.
67.
Three-dimensional dynamic structure of the liquid-ordered domain in lipid membranes as examined by pulse-EPR oxygen probing 下载免费PDF全文
Membranes made of dimyristoylphosphatidylcholine and cholesterol, one of the simplest paradigms for the study of liquid ordered-disordered phase separation, were investigated using a pulse-EPR spin-labeling method in which bimolecular collision of molecular oxygen with the nitroxide spin label is measured. This method allowed discrimination of liquid-ordered, liquid-disordered, and solid-ordered domains because the collision rates (OTP) differ in these domains. Furthermore, the oxygen transport parameter (OTP) profile across the bilayer provides unique information about the three-dimensional dynamic organization of the membrane domains. First, the OTP in the bilayer center in the liquid-ordered domain was comparable to that in the liquid-disordered domain without cholesterol, but the OTP near the membrane surface (up to carbon 9) was substantially smaller in the ordered domain, i.e., the cholesterol-based liquid-ordered domain is ordered only near the membrane surface, still retaining high levels of disorder in the bilayer center. This property may facilitate lateral mobility in ordered domains. Second, in the liquid-disordered domain, the domains with ~5 mol % cholesterol exhibited higher OTP than those without cholesterol, everywhere across the membrane. Third, the transmembrane OTP profile in the liquid-ordered domain that contained 50 mol % cholesterol dramatically differed from that which contained 27 mol % cholesterol. 相似文献
68.
Changes in CDKN2a gene are known to be linked with sporadic melanoma and hereditary predisposition to this cancer. In the Polish population mutations in the coding region of the CDKN2a gene are rather rare, therefore the attention has been focused on polymorphisms and alterations in uncoding regions such as 3' UTR. The aim of this study was to analyze two common polymorphisms, Ala148Thr and 500 C/G, and correlate them with the clinical course of melanoma. DNA from 285 patients was analyzed and found polymorphisms were correlated with the clinical parameters employing statistical methods. The obtained results allow us to conclude: (i) survival times of 500 C/G carriers vs. cumulating proportion surviving was not statistically significant; (ii) CDKN2a polymorphism 500 C/G correlated with Ala148Thr; (iii) no correlation was observed between the 500 C/G polymorphism and age of diagnosis, localization of primary melanoma and survival time; (iv) we did not find correlation between 500 C/G and type of cancer in the family; (v) changes in the CDKN2a gene were not found in patients with second cancer. 相似文献
69.
Simon Boecker Giulia Slaviero Thorben Schramm Witold Szymanski Ralf Steuer Hannes Link Steffen Klamt 《Molecular systems biology》2021,17(12)
One long‐standing question in microbiology is how microbes buffer perturbations in energy metabolism. In this study, we systematically analyzed the impact of different levels of ATP demand in Escherichia coli under various conditions (aerobic and anaerobic, with and without cell growth). One key finding is that, under all conditions tested, the glucose uptake increases with rising ATP demand, but only to a critical level beyond which it drops markedly, even below wild‐type levels. Focusing on anaerobic growth and using metabolomics and proteomics data in combination with a kinetic model, we show that this biphasic behavior is induced by the dual dependency of the phosphofructokinase on ATP (substrate) and ADP (allosteric activator). This mechanism buffers increased ATP demands by a higher glycolytic flux but, as shown herein, it collapses under very low ATP concentrations. Model analysis also revealed two major rate‐controlling steps in the glycolysis under high ATP demand, which could be confirmed experimentally. Our results provide new insights on fundamental mechanisms of bacterial energy metabolism and guide the rational engineering of highly productive cell factories. 相似文献
70.
Membranes made from binary mixtures of egg sphingomyelin (ESM) and cholesterol were investigated using conventional and saturation-recovery
EPR observations of the 5-doxylstearic acid spin label (5-SASL). The effects of cholesterol on membrane order and the oxygen
transport parameter (bimolecular collision rate of molecular oxygen with the nitroxide spin label) were monitored at the depth
of the fifth carbon in fluid- and gel-phase ESM membranes. The saturation-recovery EPR discrimination by oxygen transport
(DOT) method allowed the discrimination of the liquid-ordered (l
o), liquid-disordered (l
d), and solid-ordered (s
o) phases because the bimolecular collision rates of the molecular oxygen with the nitroxide spin label differ in these phases.
Additionally, oxygen collision rates (the oxygen transport parameter) were obtained in coexisting phases without the need
for their separation, which provides information about the internal dynamics of each phase. The addition of cholesterol causes
a dramatic decrease in the oxygen transport parameter around the nitroxide moiety of 5-SASL in the l
o phase, which at 50 mol% cholesterol becomes ∼5 times smaller than in the pure ESM membrane in the l
d phase, and ∼2 times smaller than in the pure ESM membrane in the s
o phase. The overall change in the oxygen transport parameter is as large as ∼20-fold. Conventional EPR spectra show that 5-SASL
is maximally immobilized at the phase boundary between regions with coexisting l
d and l
o phases or s
o and l
o phases and the region with a single l
o phase. The obtained results all
owed for the construction of a phase diagram for the ESM-cholesterol membrane. 相似文献