全文获取类型
收费全文 | 2313篇 |
免费 | 184篇 |
专业分类
2497篇 |
出版年
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 29篇 |
2016年 | 28篇 |
2015年 | 46篇 |
2014年 | 53篇 |
2013年 | 139篇 |
2012年 | 87篇 |
2011年 | 81篇 |
2010年 | 60篇 |
2009年 | 58篇 |
2008年 | 88篇 |
2007年 | 83篇 |
2006年 | 110篇 |
2005年 | 106篇 |
2004年 | 94篇 |
2003年 | 102篇 |
2002年 | 109篇 |
2001年 | 86篇 |
2000年 | 80篇 |
1999年 | 97篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 25篇 |
1995年 | 26篇 |
1994年 | 16篇 |
1993年 | 24篇 |
1992年 | 74篇 |
1991年 | 47篇 |
1990年 | 54篇 |
1989年 | 55篇 |
1988年 | 35篇 |
1987年 | 44篇 |
1986年 | 41篇 |
1985年 | 39篇 |
1984年 | 41篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1977年 | 22篇 |
1976年 | 14篇 |
1975年 | 20篇 |
1974年 | 12篇 |
1971年 | 12篇 |
1970年 | 12篇 |
排序方式: 共有2497条查询结果,搜索用时 15 毫秒
991.
Akita Kae Takagi Tomoko Kobayashi Keiko Kuchitsu Kazuyuki Kuroiwa Tsuneyoshi Nagata Noriko 《Protoplasma》2021,258(1):129-138
Protoplasma - During pollen maturation, various organelles change their distribution and function during development as male gametophytes. We analyzed the behavior of lipid bodies and vacuoles... 相似文献
992.
Takagi T Nakamura M Hayashi H Inatsugi R Yano R Nishida I 《Plant & cell physiology》2003,44(9):922-931
993.
994.
Yuki Sudo Ayako Okazaki Hikaru Ono Jin Yagasaki Seiya Sugo Motoshi Kamiya Louisa Reissig Keiichi Inoue Kunio Ihara Hideki Kandori Shin Takagi Shigehiko Hayashi 《The Journal of biological chemistry》2013,288(28):20624-20632
Ion-transporting rhodopsins are widely utilized as optogenetic tools both for light-induced neural activation and silencing. The most studied representative is Bacteriorhodopsin (BR), which absorbs green/red light (∼570 nm) and functions as a proton pump. Upon photoexcitation, BR induces a hyperpolarization across the membrane, which, if incorporated into a nerve cell, results in its neural silencing. In this study, we show that several residues around the retinal chromophore, which are completely conserved among BR homologs from the archaea, are involved in the spectral tuning in a BR homolog (HwBR) and that the combination mutation causes a large spectral blue shift (λmax = 498 nm) while preserving the robust pumping activity. Quantum mechanics/molecular mechanics calculations revealed that, compared with the wild type, the β-ionone ring of the chromophore in the mutant is rotated ∼130° because of the lack of steric hindrance between the methyl groups of the retinal and the mutated residues, resulting in the breakage of the π conjugation system on the polyene chain of the retinal. By the same mutations, similar spectral blue shifts are also observed in another BR homolog, archearhodopsin-3 (also called Arch). The color variant of archearhodopsin-3 could be successfully expressed in the neural cells of Caenorhabditis elegans, and illumination with blue light (500 nm) led to the effective locomotory paralysis of the worms. Thus, we successfully produced a blue-shifted proton pump for neural silencing. 相似文献
995.
Lysosomes contain multiple proteases, which play a crucial role in breast cancer invasion and metastasis. Noninvasive labeling of lysosomes in breast cancer cells and solid breast tumor models is therefore useful to study lysosomal trafficking and its role in invasion. We have synthesized a novel compound, 6'-O-lissamine-rhodamine B-glucosamine, to fluorescently label lysosomes, and evaluated the compound in human breast cancer cells in cell culture or in orthotopic human breast cancer models. We demonstrated that this novel compound biosynthetically labeled lysosomal proteins following addition to cell culture medium or following intravenous injection into mouse models of breast cancer. Fluorescence from 6'-O-lissamine-rhodamine B-glucosamine colocalized with several well-established lysosomal markers, such as lysosome-associated proteins 1 and 2 (LAMP-1 and -2) and CD63. We also demonstrated the feasibility of performing in vivo fluorescence imaging of 6'-O-lissamine-rhodamine B-glucosamine to image lysosomes in human breast cancer models. 相似文献
996.
Users' fatigue is the biggest technological hurdle facing Interactive Evolutionary Computation (IEC). This paper introduces the idea of "absolute scale" and "neighbour scale" to improve the performance of predicting users' subjective evaluation characteristics in IEC, and thus it will accelerate EC convergence and reduce users' fatigue. We experimentally evaluate the effect of the proposed method using two benchmark functions. The experimental results show that the convergence speed of IEC using the proposed predictor, which learns from absolute evaluation data, is much faster than the conventional one, which learns from relative data, especially in early generations. Also, IEC with predictors that use recent data are more effective than those which use all past data. 相似文献
997.
The ALK2 gene, encoding one of the n-alkane-hydroxylating cytochromes P450 in Candida maltosa, is induced by n-alkanes and a peroxisome proliferator, clofibrate. Deletion analysis of this gene's promoter revealed two cis-acting elements-an n-alkane-responsive element (ARE2) and a clofibrate-responsive element (CRE2)-that partly overlap in sequence but have distinct functions. ARE2-mediated activation responded to n-alkanes but not to clofibrate and was repressed by glucose. CRE2-mediated activation responded to polyunsaturated fatty acids and steroid hormones as well as to peroxisome proliferators but not to n-alkanes, and it was not repressed by glucose. Both elements mediated activation by oleic acid. Mutational analysis demonstrated that three CCG sequences in CRE2 were critical to the activation by clofibrate as well as to the in vitro binding of a specific protein to this element. These findings suggest that ALK2 is induced by peroxisome proliferators and steroid hormones through a specific CRE2-mediated regulatory mechanism. 相似文献
998.
999.
Improvement of single nucleotide polymorphism genotyping by allele-specific PCR using primers modified with an ENA residue 总被引:2,自引:0,他引:2
When we placed an ENA residue into primers at the 3' end, or the n-1, n-2, or n-3 position, which included a single nucleotide polymorphism (SNP) site at the 3' end, only primers containing the ENA residue at the n-2 position were read by Taq DNA polymerase for amplification. The use of the ENA primers avoided the generation of undesired short products, which are thought to be derived from primer-dimers. A greater discrimination of the SNP site by these primers containing the ENA residue was observed compared with that of the corresponding unmodified DNA primers that are often used for allele-specific polymerase chain reaction (AS-PCR). This improvement is probably due to the difficulty of incorporating a nucleotide into the mismatched ENA primer by Taq DNA polymerase in the modified primer-template duplex. These results demonstrate that ENA primer-based AS-PCR would enable a rapid and reliable technique for SNP genotyping. 相似文献
1000.
Suganuma R Pelczar P Spetz JF Hohn B Yanagimachi R Moisyadi S 《Biology of reproduction》2005,73(6):1157-1163
We have developed a novel method for mouse transgenesis. The procedure relies on a hyperactive Tn5 transposase to insert a transgene into mouse chromosomes during intracytoplasmic sperm injection. This procedure integrates foreign DNA into the mouse genome with dramatically increased effectiveness as compared to conventional methods such as pronuclear microinjection and traditional sperm injection-mediated transgenesis. Our data indicate that with this method, transgenic mice, both hybrids and inbreds, can be produced more consistently and with lower numbers of manipulated oocytes required for traditional microinjection methods. The transposase-mediated transgenesis technique is also effective with round spermatids, offering the potential for rescuing the fertility of azoospermic animals using sperm precursor cells. 相似文献