全文获取类型
收费全文 | 8635篇 |
免费 | 754篇 |
国内免费 | 16篇 |
专业分类
9405篇 |
出版年
2023年 | 72篇 |
2022年 | 148篇 |
2021年 | 254篇 |
2020年 | 112篇 |
2019年 | 184篇 |
2018年 | 237篇 |
2017年 | 213篇 |
2016年 | 277篇 |
2015年 | 419篇 |
2014年 | 426篇 |
2013年 | 551篇 |
2012年 | 699篇 |
2011年 | 625篇 |
2010年 | 397篇 |
2009年 | 306篇 |
2008年 | 451篇 |
2007年 | 447篇 |
2006年 | 420篇 |
2005年 | 375篇 |
2004年 | 326篇 |
2003年 | 295篇 |
2002年 | 363篇 |
2001年 | 209篇 |
2000年 | 238篇 |
1999年 | 174篇 |
1998年 | 80篇 |
1997年 | 47篇 |
1996年 | 38篇 |
1995年 | 60篇 |
1994年 | 43篇 |
1993年 | 46篇 |
1992年 | 94篇 |
1991年 | 86篇 |
1990年 | 75篇 |
1989年 | 87篇 |
1988年 | 68篇 |
1987年 | 53篇 |
1986年 | 59篇 |
1985年 | 68篇 |
1984年 | 38篇 |
1983年 | 30篇 |
1982年 | 22篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1974年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有9405条查询结果,搜索用时 15 毫秒
141.
142.
143.
越南铁线莲属一新种 总被引:3,自引:0,他引:3
Nguyen Yhi DO 《植物分类学报》2006,44(5):595-597
本文描述的产于越南的毛茛科Ranunculaceae铁线莲属Clematis一新种C. hagiangensis N. T. Do是欧亚大陆第一个具单性花的种, 在花构造方面与单性铁线莲组单性铁线莲亚组sect. Aspidanthera Spach subsect. Dioicae (Prantl) W. T. Wang的种类近缘, 但叶均为单叶, 萼片呈卵形或宽卵形而不同。在单性铁线莲亚组的种, 叶通常为复叶, 只在C. dimorphophylla W. T. Wang和C. variifolia W. T. Wang同时为单叶和复叶, 此外萼片呈长圆形、倒披针形或狭卵形。 相似文献
144.
145.
Lan Phi NT Nishiyama C Choi HS Sawamura M 《Bioscience, biotechnology, and biochemistry》2006,70(8):1832-1838
The characteristic aroma compounds of Citrus natsudaidai Hayata essential oil were evaluated by a combination of instrumental and sensory methods. Sixty compounds were identified and quantified, accounting for 94.08% of the total peel oil constituents. Limonene was the most abundant compound (80.68%), followed by gamma-terpinene (5.30%), myrcene (2.25%) and alpha-pinene (1.30%). Nineteen compounds which could not be identified in the original oil were identified in the oxygenated fraction. Myrcene, linalool, alpha-pinene, beta-pinene, limonene, nonanal, gamma-terpinene, germacrene D, and perillyl alcohol were the active aroma components (FD-factor > 3(6)), whereas beta-copaene, cis-sabinene hydrate and 1-octanol were suggested as characteristic aroma compounds, having a Natsudaidai-like aroma in the GC effluent. Three other compounds, heptyl acetate, (E)-limonene oxide and 2,3-butanediol, which each showed a high RFA value (>35) were considered to be important in the reconstruction of the original Natsudaidai oil from pure odor chemicals. The results indicate that 1-octanol was the aroma impact compound of C. natsudaidai Hayata peel oil. 相似文献
146.
Exonuclease V from Saccharomyces cerevisiae. A 5'----3'-deoxyribonuclease that produces dinucleotides in a sequential fashion 总被引:3,自引:0,他引:3
A novel deoxyribonuclease, exonuclease V, has been purified approximately 30,000-fold from Saccharomyces cerevisiae. Exonuclease V is localized in the nucleus. The nuclease degrades single-stranded, but not double-stranded, DNA from the 5'-end. The products of exonuclease action are dinucleotides, except the 3'-terminal tri- and tetranucleotides which are not degraded. Studies with synthetic oligo- and polynucleotides with specified sequence elements showed that exonuclease V cleaves off dinucleotides as primary digestion products. Thus, the polymers (pT)9pA(pT)n and (pT)10pA(pT)n yielded pTpA and pApT as digestion products, respectively. Removal of the 5'-terminal phosphate from the DNA substrate results in reduced binding of the enzyme to the substrate. In addition, the initial hydrolytic cut by exonuclease V on the dephosphorylated substrate produces a mixture of dinucleoside monophosphates and trinucleoside diphosphates. The enzyme is processive in action. 相似文献
147.
Su Duy Nguyen 《生物化学与生物物理学报:生物膜》2006,1758(4):499-508
To examine the effect of phospholipids on PON1 activities, purified PON1 was exposed to phospholipids prior to the determination of arylesterase and paraoxonase activities. Phosphatidylcholines with saturated acyl chains (C10-C16) showed a stimulation of both activities, chain length-dependent, with a greater stimulation of arylesterase activity, suggesting the implication of lipid bilayer in the stimulatory action. Such a preferable stimulation of arylesterase activity was more remarkable with phosphatidylcholines with polyunsaturated acyl chains or oxidized chains at sn-2 position, implying that the packing degree of acyl chain may be also important for the preferable stimulation of arylesterase activity. Separately, 1-palmitoyl-lysoPC also stimulated arylesterase activity preferably, indicating that the micellar formation of lipids around PON1 also contributes to the stimulatory action. Additionally, phosphatidylglycerols slightly enhanced arylesterase activity, but not paraoxonase activity. In contrast, phosphatidylserine and phosphatidic acid (≥0.1 mM) inhibited both activities Further, such a preferable stimulation of arylesterase activity by phosphatidylcholines was also reproduced with VLDL-bound PON1, although to a less extent. These data indicate that phosphatidylcholines with polyunsaturated acyl chains or oxidized chain, or lysophosphatidylcholine cause a preferable stimulation of arylesterase activity, thereby contributing to the decrease in the ratio of paraoxonase activity to arylesterase activity. 相似文献
148.
Development of a 16S rRNA gene-based prototype microarray for the detection of selected actinomycetes genera 总被引:1,自引:0,他引:1
Kyselková M Kopecký J Felföldi T Cermák L Omelka M Grundmann GL Moënne-Loccoz Y Ságová-Marecková M 《Antonie van Leeuwenhoek》2008,94(3):439-453
Actinomycetes are known for their secondary metabolites, which have been successfully used as drugs in human and veterinary medicines. However, information on the distribution of this group of Gram-positive bacteria in diverse ecosystems and a comprehension of their activities in ecosystem processes are still scarce. We have developed a 16S rRNA-based taxonomic microarray that targets key actinomycetes at the genus level. In total, 113 actinomycete 16S rRNA probes, corresponding to 55 of the 202 described genera, were designed. The microarray accuracy was evaluated by comparing signal intensities with probe/target-weighted mismatch values and the Gibbs energy of the probe/target duplex formation by hybridizing 17 non-actinomycete and 29 actinomycete strains/clones with the probe set. The validation proved that the probe set was specific, with only 1.3% of false results. The incomplete coverage of actinomycetes by a genus-specific probe was caused by the limited number of 16S rRNA gene sequences in databases or insufficient 16S rRNA gene polymorphism. The microarray enabled discrimination between actinomycete communities from three forest soil samples collected at one site. Cloning and sequencing of 16S rRNA genes from one of the soil samples confirmed the microarray results. We propose that this newly constructed microarray will be a valuable tool for genus-level comparisons of actinomycete communities in various ecological conditions. 相似文献
149.
Nonrandom induction of pyrimidine-pyrimidone (6-4) photoproducts in ultraviolet-irradiated human chromatin 总被引:8,自引:0,他引:8
Radioimmunoassays that detect pyrimidine-pyrimidone (6-4) photoproducts and cyclobutane dimers were used to determine the relative induction of these photoproducts in nucleosomal (core) and internucleosomal (linker) DNA in human cell chromatin irradiated with UV light. Cyclobutane dimers were formed in equal amounts/nucleotide in core and linker DNA, whereas (6-4) photoproducts occurred with 6-fold greater frequency/nucleotide in linker DNA. 相似文献
150.
Loc Van Nguyen Ryoji Takahashi Stephen Mwangi Githiri Tito O. Rodriguez Nobuko Tsutsumi Sayuri Kajihara Takasi Sayama Masao Ishimoto Kyuya Harada Keisuke Suematsu Tomomi Abiko Toshihiro Mochizuki 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2017,130(4):743-755