全文获取类型
收费全文 | 1287篇 |
免费 | 57篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 31篇 |
2020年 | 16篇 |
2019年 | 23篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 34篇 |
2015年 | 52篇 |
2014年 | 55篇 |
2013年 | 56篇 |
2012年 | 87篇 |
2011年 | 84篇 |
2010年 | 57篇 |
2009年 | 46篇 |
2008年 | 53篇 |
2007年 | 80篇 |
2006年 | 64篇 |
2005年 | 47篇 |
2004年 | 50篇 |
2003年 | 58篇 |
2002年 | 46篇 |
2001年 | 36篇 |
2000年 | 21篇 |
1999年 | 23篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1992年 | 25篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1985年 | 5篇 |
1983年 | 10篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1972年 | 9篇 |
1971年 | 10篇 |
1970年 | 13篇 |
1969年 | 10篇 |
1968年 | 8篇 |
1967年 | 5篇 |
1965年 | 9篇 |
排序方式: 共有1345条查询结果,搜索用时 218 毫秒
1.
2.
E. N. Medvedeva N. A. Neverova T. E. Fedorova V. A. Babkin E. S. Meteleva A. V. Dushkin T. G. Tolstikova M. V. Khvostov M. P. Dolgikh 《Russian Journal of Bioorganic Chemistry》2010,36(7):853-859
It has been found by gel-penetrating chromatography and quantitative 13C NMR spectroscopy that mechanochemical processing of arabinogalactan isolated from the wood of the Siberian larch changes
the molecular mass distribution, monosaccharide composition, and the degree of branching of its macromolecules. This is due
to the partial destruction of polysaccharide macromolecules and subsequent recombination of resulting fragments. The intensity
of these processes depends on the conditions of mechanochemical processing. Based on the data of IR and 13C NMR spectra, the conclusion has been drawn that no functionalization of arabinogalactan macromolecules occurs under these
conditions. The toxicopharmacological properties of mechanically processed arabinogalactan have been studied. Its acute toxicity
is >5000 mg/kg. 相似文献
3.
L. A. Piruzyan V. A. Sukhanov E. V. Kalinina T. Yu. Fedorova A. N. Saprin 《Biology Bulletin》2002,29(2):115-119
We studied intraspecific features of the main enzymes of metabolism and detoxication of xenobiotics on mice (eight inbred lines) and rats (five lines) for estimation of possible variants of complete or incomplete metabolic equality. Significant genetically determined intraspecific differences for activities of the enzymes of metabolism and detoxication of xenobiotics were described. Generalized criteria for comparison of the metabolic status were proposed on the basis of activities of the main enzymes: cytochrome P-450 (hydroxylation and epoxidation), epoxyhydrolase, glutathione-S-transferase, UDP-glucuronosyl transferase, and sulfotransferase. The proposed criteria for estimation of the metabolic parameters of an individual can serve as a basis of metabolic portraiting. 相似文献
4.
S V Usova T S Fedorova Iu V Fedorov N B Al'bitskaia 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1984,(12):89-90
Materials on the study of relationship between the activity of immunoreactive insulin and the degree of an increase in the level of anti-influenza antibodies, induced by vaccine strains, are presented. A short-term decrease in the activity of insulin, more pronounced in donors immunized with adsorbed chemical influenza vaccine, and an increase in the antibody level, mainly in the group of donors receiving killed influenza vaccine, have been noted. 相似文献
5.
6.
The paper submits the results of studies on the kinetics of spermatogenous epithelium cell number after exposure to fast neutrons (60-300 cGy) and gamma-radiation (200-600 cGy). It was shown that a relative decrease in the quantity of spermatocytes is determined by an exponential dose-response curve with D0 of 35 and 120 cGy for neutrons and gamma-radiation respectively. For spermatides and spermatozoa a single D0 value of 20 and 55 cGy was obtained for neutrons and gamma-radiation respectively. As the radiation dose increases the recovery process in the epithelium is substantially decelerated. The equation T1/2 = T1/2(0)e0.0009D well describes the dependence of the half-recovery period T1/2 upon the equivalent dose. 相似文献
7.
8.
The complex N-AcPhe-tRNA(Phe).poly(U).80 S ribosome from human placenta was treated with puromycin taken in various concentrations. Based on the kinetic data of N-acetylphenylalanyl-puromycin formation, the association constant of puromycin with the acceptor site of the ribosome was estimated to be (3.96 +/- 0.84) x 10(4) M-1 at 37 degrees C. 相似文献
9.
The 34-mer oligodeoxynucleotide was shown to be selectively modified at the G17 position upon photoirradiation in the presence of complementary 17-mer oligodeoxynucleotide bearing Pd(II)-coproporphyrin I covalently linked to the 5'-end phosphate group. 相似文献
10.
Larisa R. G. DeSantis Jessica R. Scott Blaine W. Schubert Shelly L. Donohue Brian M. McCray Courtney A. Van Stolk Amanda A. Winburn Michael A. Greshko Mackie C. O’Hara 《PloS one》2013,8(8)
The analysis of dental microwear is commonly used by paleontologists and anthropologists to clarify the diets of extinct species, including herbivorous and carnivorous mammals. Currently, there are numerous methods employed to quantify dental microwear, varying in the types of microscopes used, magnifications, and the characterization of wear in both two dimensions and three dimensions. Results from dental microwear studies utilizing different methods are not directly comparable and human quantification of wear features (e.g., pits and scratches) introduces interobserver error, with higher error being produced by less experienced individuals. Dental microwear texture analysis (DMTA), which analyzes microwear features in three dimensions, alleviates some of the problems surrounding two-dimensional microwear methods by reducing observer bias. Here, we assess the accuracy and comparability within and between 2D and 3D dental microwear analyses in herbivorous and carnivorous mammals at the same magnification. Specifically, we compare observer-generated 2D microwear data from photosimulations of the identical scanned areas of DMTA in extant African bovids and carnivorans using a scanning white light confocal microscope at 100x magnification. Using this magnification, dental microwear features quantified in 2D were able to separate grazing and frugivorous bovids using scratch frequency; however, DMTA variables were better able to discriminate between disparate dietary niches in both carnivorous and herbivorous mammals. Further, results demonstrate significant interobserver differences in 2D microwear data, with the microwear index remaining the least variable between experienced observers, consistent with prior research. Overall, our results highlight the importance of reducing observer error and analyzing dental microwear in three dimensions in order to consistently interpret diets accurately. 相似文献