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961.
962.
通过对宣城扬子鳄繁殖研究中心三代繁殖鳄1982—2003年繁殖力有关参数的分析,结果表明近三年来繁殖研究中心扬子鳄产卵量明显减少;亲代受精率为(83.80±2.37)%、孵化率为(89.53±0.86)%;发现F1受精率为(79.38±2.74)%、孵化率为(83.78±1.95)%;F2代个体受精率为(68.7±1.84)%、孵化率为(88.16±1.68)%;通过单因素方差分析F(受精率)=4.33(P<0.05)、F(孵化率)=4.56(P<0.05)差异显著。分析影响扬子鳄繁殖的因素发现:产卵量明显减少可能与亲代鳄逐渐退出繁殖期、F1代鳄整体产卵能力有下降趋势、F2代鳄没有大规模进入繁殖期有关;分析历史资料发现扬子鳄产卵窝数与4月份的温度相关性高(R=0.979,P<0.01);作者认为F1、F2代个体与亲代之间的受精率、孵化率有显著差异,近交衰退、遗传多样性的丧失有密切关系。利用时间序列分析建立理想状态下饲养扬子鳄种群数量估计模型,预测10年内扬子鳄饲养将可能达到19000尾;根据该种群增长模式及种群年龄结构特点,应扩大饲养规模,特别是育成鳄饲养池及幼鳄饲养池的建设。 相似文献
963.
A cell-detaching reactor was developed to collect cells growing on microcarriers for inoculation between stepwise-expanded
bioreactors. It consisted of a trypsinization zone and a separation zone, which were separated by a 200-mesh stainless steel
screen. The screen allowed the cells only to pass through to the next bioreactor, after the cells have been trypsinized and
detached from microcarriers. The operating feasibility of the cell-detaching reactor was tested with anchorage-dependent recombinant
Chinese hamster ovary (rCHO) and African green monkey kidney (Vero) cells. rCHO and Vero cells were first cultured in a small
microcarrier bioreactor, and then inoculated via the cell-detaching reactor into either a packed-bed bioreactor (for rCHO
cells) or a larger microcarrier bioreactor (for Vero cells). For rCHO cells, the cell density reached 1.3 × 107 cells/ml in the perfusion culture, and Vero cells reached 1.3 × 106 cells/ml in the batch culture. 相似文献
964.
Conventional breeding of Chinese sweetgum is constrained by its long-reproductive cycle, which includes long-juvenile periods,
and by its complex reproductive characteristics, including self-incompatibility and a high degree of heterozygosis. Like other
tree species, sweetgum has undergone relatively little domestication; the methodology described here in illustrates the possibility
of transforming Liquidambar formosana L. obtained from leafy explants using Agrobacter tumefaciens. PCR and Southern blotting show that foreign gene had integrated to genomic DNA. The results indicated that superoxide dismutase
(SOD) and peroxidase (POD) activities increased with the stress time in all treated plants and these activities of the transgenic
plant were stably higher than those of the control. RT-PCR showed that BADH expressed strongly induced by NaCl. The present study showed that the Rd29A promoter is able to direct osmotant gene expression when plant was exposed to salt, cold, and drought stress, with the advantage
that expression was absent or undetectable in natural grow phase. 相似文献
965.
Matsumiya S Yamaguchi Y Saito J Nagano M Sasakawa H Otaki S Satoh M Shitara K Kato K 《Journal of molecular biology》2007,368(3):767-779
Removal of the fucose residue from the oligosaccharides attached to Asn297 of human immunoglobulin G1 (IgG1) results in a significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) via improved IgG1 binding to Fcgamma receptor IIIa. To provide structural insight into the mechanisms of affinity enhancement, we determined the crystal structure of the nonfucosylated Fc fragment and compared it with that of fucosylated Fc. The overall conformations of the fucosylated and nonfucosylated Fc fragments were similar except for hydration mode around Tyr296. Stable-isotope-assisted NMR analyses confirmed the similarity of the overall structures between fucosylated and nonfucosylated Fc fragments in solution. These data suggest that the glycoform-dependent ADCC enhancement is attributed to a subtle conformational alteration in a limited region of IgG1-Fc. Furthermore, the electron density maps revealed that the traces between Asp280 and Asn297 of our fucosylated and nonfucosylated Fc crystals were both different from that in previously reported isomorphous Fc crystals. 相似文献
966.
In order to clarify the origin and genetic diversity of yak in China, we analysed mitochondrial DNA (mtDNA) control region sequences (approximately 891 bp) in 52 individuals from four domestic yak (Poephagus grunniens) breeds, as well as from a hybrid between yak and cattle (Pianniu). Twenty-five samples were further selected for partial (420 bp) cytochrome b sequencing based on control region sequence information. Two yak samples shared sequences with Chinese cattle (Bos taurus); the remaining yak mtDNAs converged into two major clades in the phylogenetic analysis. Genetic diversity varied substantially among the breeds, with the hybrid Pianniu yak demonstrating the highest diversity. Our results suggest that the Chinese yak was domesticated from two distinct matrilineal sources or from a heterogeneous pool containing both divergent lineages, with occasional gene introgression from cattle. 相似文献
967.
The first example of cell therapy using cultured stem cells dates back to 1981, when it was demonstrated that human epidermis could be grown in the laboratory and transplanted onto burnt patients to reconstitute a functional epidermis [Green H, Kehinde O, Thomas J. Growth of cultured human epidermal cells into multiple epithelia suitable for grafting. Proc Natl Acad Sci USA 1979;76(11):5665-8; Banks-Schlegel S, Kehinde O, Green H. Grafting of burns with cultured epithelium prepared from autologous epidermal cells. Lancet 1981;1:75-8; Gallico 3rd GG, O'Connor NEMJ, Compton CC, Kehinde O, Green H. Permanent coverage of large burn wounds with autologous cultured human epithelium. N Engl J Med 1984;311(7):448-51]. This was the onset of regenerative medicine, which is now being developed also in many other fields including ophthalmology. Emerging cell therapies for the restoration of sight have focused on two areas of the eye that are critical for visual function, the cornea and the retina. The relatively easy access of the cornea, the homogeneity of the cells forming the different layers of the corneal epithelium and the improvement of cell culture protocols are leading to considerable success in corneal epithelium restoration. Rebuilding the entire cornea is however still far from reality. The restoration of the retina has recently been achieved in different animal models of retinal degeneration using immature photoreceptors, and two other promising strategies have been demonstrated: transplantation of endothelial precursors to rescue retinal vessels and neurons, and transplantation of retinal pigmented epithelial cells to preserve vision over the long term. The relevance of these approaches will be discussed in function of the disease targeted. 相似文献
968.
The quality of pharmaceutical products such as ginseng is important for ensuring consumer safety and efficacy. Ginseng is
an expensive herb, and adulteration with other cheaper products may occur. Quality assurance of ginseng is needed since many
of its commercial products now come in various formulations such as capsules, powder, softgels and tea. Thus traditional means
of authentication via smell, taste or physical appearance are hardly reliable. Herbs like ginseng tend to exhibit characteristic
infrared fingerprints due to their different chemical constituents. Here we report for the first time a rapid means of distinguishing
American and Asian ginsengs from two morphological fakes – sawdust and Platycodon grandiflorum, via pattern differences and principal component analysis of their infrared spectra. Our results show that ginseng can be
distinguished from both sawdust and Platycodon grandiflorum, hence there is a potential of using infrared spectroscopy as a novel analytical technique in the authentication of ginseng. 相似文献
969.
Min BW Cho YN Song MJ Noh TK Kim BK Chae WK Park YS Choi YD Harn CH 《Plant cell reports》2007,26(3):337-344
A mannose selection system was adapted for use in the Agrobacterium-mediated transformation of Chinese cabbage. This system makes use of the pmi gene that encodes phosphomannose isomerase, which converts mannose-6-phosphate to fructose-6-phosphate. Hypocotyl explants
from 4–5-day-old seedlings of Chinese cabbage inbred lines were pre-cultured for 2–3 days and then infected with Agrobacterium. Two genes (l-guluno-γ-lactone oxidase, GLOase, and jasmonic methyl transferase, JMT) were transformed into Chinese cabbage using the transformation procedure developed in this study. We found that supplementing
the media with 7 g l−1 mannose and 2% sucrose provides the necessary conditions for the selection of transformed plants from nontransformed plants.
The transformation rates were 1.4% for GLOase and 3.0% for JMT, respectively. The Southern blot analysis revealed that several independent transformants (T
0) were obtained from each transgene. Three different inbred lines were transformed, and most of the T
1 plants had normal phenotypes. The transformation method presented here for Chinese cabbage using mannose selection is efficient
and reproducible, and it can be useful to introduce a desirable gene(s) into commercially useful inbred lines of Chinese cabbage. 相似文献
970.
Paula Meleady 《Cytotechnology》2007,53(1-3):23-31
Global expression profiling of mammalian cells used for the production of biopharmaceuticals will allow greater insights into
the molecular mechanisms that result in a high producing cellular phenotype. These studies may give insights for genetic intervention
to possibly create better host cell lines or even to provide clues to more rational strategies for cell line and process development.
In this review I will focus on the contribution of proteomic technologies to a greater understanding of the biology of Chinese
hamster ovary cells and other producing cell lines such as NS0 mouse cells. 相似文献