全文获取类型
收费全文 | 6932篇 |
免费 | 340篇 |
国内免费 | 5篇 |
专业分类
7277篇 |
出版年
2023年 | 13篇 |
2022年 | 51篇 |
2021年 | 70篇 |
2020年 | 56篇 |
2019年 | 53篇 |
2018年 | 83篇 |
2017年 | 68篇 |
2016年 | 158篇 |
2015年 | 230篇 |
2014年 | 237篇 |
2013年 | 507篇 |
2012年 | 450篇 |
2011年 | 486篇 |
2010年 | 295篇 |
2009年 | 276篇 |
2008年 | 467篇 |
2007年 | 500篇 |
2006年 | 452篇 |
2005年 | 440篇 |
2004年 | 506篇 |
2003年 | 383篇 |
2002年 | 398篇 |
2001年 | 65篇 |
2000年 | 56篇 |
1999年 | 65篇 |
1998年 | 96篇 |
1997年 | 72篇 |
1996年 | 69篇 |
1995年 | 69篇 |
1994年 | 59篇 |
1993年 | 51篇 |
1992年 | 41篇 |
1991年 | 48篇 |
1990年 | 38篇 |
1989年 | 36篇 |
1988年 | 40篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 29篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有7277条查询结果,搜索用时 15 毫秒
131.
Gotoh T Ono H Kikuchi K Nirasawa S Takahashi S 《Bioscience, biotechnology, and biochemistry》2010,74(10):2154-2157
An aspartic protease that is significantly produced by baculovirus-infected Spodoptera frugiperda Sf9 insect cells was purified to homogeneity from a growth medium. To monitor aspartic protease activity, an internally quenched fluoresce (IQF) substrate specific to cathepsin D was used. The purified aspartic protease showed a single protein band on SDS-PAGE with an apparent molecular mass of 40 kDa. The N-terminal amino acid sequence of the enzyme had a high homology to a Bombyx mori aspartic protease. The enzyme showed greatest affinity for the IQF substrate at pH 3.0 with a K(m) of 0.85 μM. The k(cat) and k(cat)/K(m) values were 13 s(-1) and 15 s(-1) μM(-1) respectively. Pepstatin A proved to be a potent competitive inhibitor with inhibitor constant, K(i), of 25 pM. 相似文献
132.
Age-related changes of elements and relationships among elements in the common bile and pancreatic ducts 总被引:1,自引:0,他引:1
Tohno Y Tohno S Yamada MO Azuma C Moriwake Y Minami T Maruyama H Omura T 《Biological trace element research》2004,101(1):47-60
To elucidate compositional changes of the common bile and main pancreatic ducts with aging, the authors investigated age-related
changes of element contents in the common bile and pancreatic ducts by inductively coupled plasma-atomic emission spectrometry.
After ordinary dissection by medical students was finished, the common bile ducts and main pancreatic ducts (pancreatic ducts)
were resected and the element contents were determined. The Mg content increased significantly only in the pancreatic duct
with aging, but the other element contents did not change significantly in both the common bile and pancreatic ducts with
aging. Regarding the relationship among the elements, significant direct correlations were found among the contents of Ca,
P, S, and Mg in the common bile ducts, with some exceptions between P and either S or Mg contents. In the pancreatic ducts,
significant direct correlations were found between S and Mg contents and between P and Na contents. The relationships in the
elements between the common bile and pancreatic ducts were examined. It was found that there were significant direct correlations
in the Ca, Mg, and Fe contents between the common bile and pancreatic ducts; that is, as Ca, Mg, and Fe increased in the common
bile duct, they increased simultaneously in the pancreatic duct. 相似文献
133.
Detection of Rhizoctonia solani AG 2-2 LP isolates causing large-patch disease on zoysia grass was done using polymerase chain reaction (PCR). Specific primers were designed based on an amplified region using random amplified polymorphic DNA (RAPD)-PCR. Fifteen primers and three cultural types of R. solani AG 2-2 (types IIIB, IV and LP) were used for RAPD-PCR. The banding patterns by RAPD-PCR showed that the three cultural types were clearly distinguishable. A dendrogram constructed from the results of RAPD-PCR showed that the three cultural types of AG 2-2 clustered separately. The sequence of one PCR-amplified region which appeared only in LP isolates using primer A09 was selected for designing specific primers. Primer pair A091-F/R gave a single product from pure fungal DNA of LP isolates but not from those of the other two types (IIIB and IV), R. solani AG 1, 2-1, 2-3, 2-tulip, 3-10 and BI isolates and other turfgrass fungal pathogens. Primer pair A091-F/R also gave a single product from diseased leaf sheaths and this product was in accordance with those of pure fungal DNA of LP isolates. Primer pair A091-F/R did not yield PCR product from healthy leaf sheaths. The frequencies of detection of LP isolates from leaf sheaths of zoysia grass using PCR with primer pair A091-F/R were higher than those of the conventional isolation technique. These results showed that the PCR-based technique using specific primers A091-F/R is useful for the rapid detection of LP isolates from leaf sheaths of zoysia grass exhibiting large-patch symptoms. 相似文献
134.
Fusarium solani M-13-1 was shake-cultured in a medium containing guaiacylglycerol-β-coniferyl ether (I), a model compound representing the arylglycerol-β-aryl ether linkage in lignin, as sole carbon source. From the culture filtrate guaiacylglycerol-β-coniferyl aldehyde ether (II) and guaiacylglycerol-β-ferulic acid ether (III) were isolated as metabolic products. Incubation with (III) resulted in formation of guaiacylglycerol-β-vanillin ether (IV), which was further metabolized to guaiacyglycerol-β-vanillic acid ether (V). The results indicate that the cinnamyl alcohol group of (I) is initially oxidized to an aldehyde group, which is further oxidized to a carboxyl group, yielding (II) and (III). Compound (III) is converted to (IV) by the release of a C2 fragment, and the aldehyde group of (IV) is further oxidized to a carboxyl group, giving (V). In the pathway from (I) to (V), neither oxidation of the benzylic secondary alcohol to ketone nor cleavage of the arylglycerol-β-aryl ether linkage was observed. The fungus was found to attack both erythro and threo form without distinction. 相似文献
135.
Osamu Yamauchi Tatsuo Yajima Rie Fujii Yuichi Shimazaki Masanobu Yabusaki Masako Takani Minoru Tashiro Takeshi Motoyama Mitsuhiro Kakuto Yasuo Nakabayashi 《Journal of inorganic biochemistry》2008,102(5-6):1218
Intramolecular M(II)H–C interactions (M(II)=Cu(II), Pd(II)) involving a side chain alkyl group of planar d8 and d9 metal complexes of the N-alkyl (R) derivatives of N,N-bis(2-pyridylmethyl)amine with an N3Cl donor set were established by structural and spectroscopic methods. The methyl group from the branched alkyl group (R = 2,2-dimethylpropyl and 2-methylbutyl) axially interacts with the metal ion with the MC and MH distances of 3.056(3)–3.352(9) and 2.317(1)–2.606(1) Å, respectively, and the M–H–C angles of 122.4–162.3°. The Cu(II) complexes showing the interaction have a higher redox potential as compared with those without it, and the 1H NMR signals of the interacting methyl group in Pd(II) complexes shifted downfield relative to the ligand signals. Dependence of the downshift values on the dielectric constants of the solvents used indicated that the M(II)H–C interaction is mainly electrostatic in nature and may be regarded as a weak hydrogen bond. Implications for possible environmental effects of the leucine alkyl group at the type 1 Cu site of fungal laccase are also discussed. 相似文献
136.
Conversion of AFLP markers to sequence-specific markers for closely related lines in rice by use of the rice genome sequence 总被引:1,自引:0,他引:1
Shirasawa Kenta Kishitani Sachie Nishio Takeshi 《Molecular breeding : new strategies in plant improvement》2004,14(3):283-292
DNA polymorphism between two major japonica rice cultivars, Nipponbare and Koshihikari, was identified by AFLP. Eighty-four polymorphic AFLP markers were obtained by analysis with 360 combinations of primer pairs. Nucleotide sequences of 73 markers, 29 from Nipponbare and 44 from Koshihikari, were determined, and 46 AFLP markers could be assigned to rice chromosomes based on sequence homology to the rice genome sequence. Specific primers were designed for amplification of the regions covering the AFLP markers and the flanking sequences. Out of the 46 primer pairs, 44 amplified single DNA fragments, six of which showed different sizes between Nipponbare and Koshihikari, yielding codominant SCAR markers. Eight primer pairs amplified only Nipponbare sequences, providing dominant SCAR markers. DNA fragments amplified by 13 primer pairs showed polymorphism by CAPS, and polymorphism of those amplified by 13 other primer pairs were detected by PCR-RF-SSCP (PRS). Nucleotide sequences of the other four DNA fragments were determined in Koshihikari, but no difference was found between Koshihikari and Nipponbare. In total, 40 sequence-specific markers for the combination of Nipponbare and Koshihikari were produced. All the SNPs identified by AFLP were detectable by CAPS and PRS. The same method was applicable to a combination of Kokoromachi and Tohoku 168, and 23 polymorphic markers were identified using these two rice cultivars. The procedure of conversion of AFLP-markers to the sequence-specific markers used in this study enables efficient sequence-specific marker production for closely related cultivars. 相似文献
137.
In ectotherms, lower temperatures at high latitudes would theoretically reduce annual growth rates of individuals. If slower
growth and resulting smaller body size reduce fitness, individuals at high latitudes may evolve compensatory growth. This
study compares individual growth rates among and within 12 latitudinal populations of the medaka (Oryzias latipes). Growth rates during juvenile stage were measured in a common, temperature-controlled (28°C) environment. The results revealed
that juvenile growth rates differed significantly among the populations. Growth rates were, moreover, significantly correlated
with latitudes of source populations, such that higher-latitude individuals grew faster. Significant variation in growth rates
among full-sib families within populations was also demonstrated. The results strongly suggest that higher-latitude O. latipes have acquired a greater capacity for growth as an adaptation to shorter growing seasons (which would reduce annual growth
rates), thus refuting probability processes, i.e., genetic drift, founder, or bottleneck effects, as a cause of the among-population
variation. 相似文献
138.
Dai Kitamoto Takashi Nakane Noriko Nakao Tadaatsu Nakahara Takeshi Tabuchi 《Applied microbiology and biotechnology》1992,36(6):768-772
Summary
Candida antarctica strain T-34, which was isolated as a biosurfactant producer, was found to produce organic acids and polyols extracellularly but not to produce biosurfactants, when grown on glucose or other carbohydrates as the sole carbon source. It was also observed microscopically that the strain contained oil globules within the cells. The intracellular lipids of the strain mainly consisted of triglycerides and mannosylerythritol lipids (MEL). The MEL content of the cells during the culture exceeded 10% of the dry cell weight, and the pattern of variation of the MEL content was very similar to that of triglycerides. All three stock strains of C. antarctica tested also accumulated a relatively large amount of MEL from glucose. These results suggested that these strains accumulated the MEL intracellularly as one of the storage materials together with triglycerides.Offprint requests to: D. Kitamoto 相似文献
139.
140.
Poly(binaphthyl salen manganese complex)es 3-Mn were synthesized from a 3,3'-diformylbinaphthol derivative, alpha,omega-diamines, and Mn(OAc)2. Their helical structures were well-supported by their IR, UV, and CD spectra. The catalysis of 3-Mn in an asymmetric epoxidation was investigated. 相似文献