全文获取类型
收费全文 | 3791篇 |
免费 | 318篇 |
国内免费 | 2篇 |
出版年
2022年 | 10篇 |
2021年 | 36篇 |
2020年 | 22篇 |
2019年 | 39篇 |
2018年 | 59篇 |
2017年 | 44篇 |
2016年 | 71篇 |
2015年 | 104篇 |
2014年 | 134篇 |
2013年 | 265篇 |
2012年 | 210篇 |
2011年 | 268篇 |
2010年 | 152篇 |
2009年 | 140篇 |
2008年 | 245篇 |
2007年 | 224篇 |
2006年 | 226篇 |
2005年 | 210篇 |
2004年 | 222篇 |
2003年 | 221篇 |
2002年 | 233篇 |
2001年 | 55篇 |
2000年 | 68篇 |
1999年 | 70篇 |
1998年 | 61篇 |
1997年 | 43篇 |
1996年 | 24篇 |
1995年 | 22篇 |
1994年 | 40篇 |
1993年 | 34篇 |
1992年 | 62篇 |
1991年 | 42篇 |
1990年 | 53篇 |
1989年 | 45篇 |
1988年 | 52篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1975年 | 14篇 |
1974年 | 15篇 |
1970年 | 10篇 |
1968年 | 14篇 |
排序方式: 共有4111条查询结果,搜索用时 250 毫秒
51.
Hisao Kurazono Shinji Yamasaki Orn-anong Ratchtrachenchai G. Balakrish Nair Yoshifumi Takeda 《Microbiology and immunology》1996,40(4):303-305
Vibrio cholerae O139 isolated from different countries, as well as from different locations within a country, were examined using macrorestriction DNA analysis to determine the clonality of the O139 strains. NotI digests of genomic DNA of representative strains from Nepal, India, Bangladesh, China, Thailand, and Malaysia revealed very similar but not identical patterns. Examinations of the banding patterns generated by pulsed-field gel electrophoresis of strains isolated within countries revealed complete homogeneity. These results further reiterate the spread of an identical clone of V. cholerae O139 although it appears that genetic polymorphism among the O139 strains is becoming apparent. 相似文献
52.
Shinji Yamasaki Zaw Lin Hiromasa Shirai Akito Terai Yuichi Oku Hideaki Ito Mari Ohmura Tadahiro Karasawa Teizo Tsukamoto Hisao Kurazono Yoshifumi Takeda 《Microbiology and immunology》1996,40(5):345-352
To identify the type of Verotoxins (VT) produced by Verocytotoxin-producing Escherichia coli (VTEC), a sensitive bead-enzyme-linked immunosorbent assay and polymerase chain reaction with common and specific primers to various VTs (VT1, VT2, VT2vha, VT2vhb, and VT2vp1) were developed. Together with colony hybridization tests with oligo- and polynucleotide probes, these methods were applied to VTEC isolates to type the VT produced. The toxin types of 26 of 37 strains were identified, but the reaction profiles in assays of the remaining 11 strains suggested the existence of new VT2 variants. The application of these identification procedures may be useful as a tool for clinical and epidemiological studies of VTEC infection. 相似文献
53.
M. Kato H. J. Bao C.-K. Kang T. Fukui Y. Doi 《Applied microbiology and biotechnology》1996,45(3):363-370
Pseudomonas sp. 61-3 (isolated from soil) produced a polyester consisting of 3-hydroxybutyric acid (3HB) and of medium-chain-length 3-hydroxyalkanoic
acids (3HA) of C6, C8, C10 and C12, when sugars of glucose, fructose and mannose were fed as the sole carbon source. The polyester produced was a blend of homopolymer
and copolymer, which could be fractionated with boiling acetone. The acetone-insoluble fraction of the polyester was a homopolymer
of 3-hydroxybutyrate units [poly (3HB)], while the acetone-soluble fraction was a copolymer [poly(3HB-co-3HA)] containing both short- and medium-chain-length 3-hydroxyalkanoate units ranging from C4 to C12:44 mol% 3-hydroxybutyrate, 5 mol% 3-hydroxyhexanoate, 21 mol% 3-hydroxyoctanoate, 25 mol% 3-hydroxydecanoate, 2 mol% 3-hydroxydodecanoate
and 3 mol% 3-hydroxy-5-cis-dodecenoate. The copolyester was shown to be a random copolymer of 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoate
units by analysis of the 13C-NMR spectrum. The poly(3HB) homopolymer and poly (3HB-co-3HA) copolymer were produced simultaneously within cells from glucose in the absence of any nitrogen source, which suggests
that Pseudomonas sp. 61-3 has two types of polyhydroxy-alkanoate syntheses with different substrate specificities.
Received: 9 June 1995/Received last revision: 30 October 1995/Accepted: 6 November 1995 相似文献
54.
Shinichiro Nakamura Wijit Kiatipattanasakul Hiroyuki Nakayama Fumiko Ono Ippei Sakakibara Yasuhiro Yoshikawa Naoaki Goto Kunio Doi 《Journal of medical primatology》1996,25(4):294-300
Abstract: In this study, we immunohistochemically examined the several constituents of senile plaques (SPs) and cerebral amyloid angiopathy (CAA) in aged cynomolgus monkeys. Apolipoprotein E (apoE) deposited in all mature plaques and CAA, and in half of the diffuse plaques. Alpha-1-antichymotripsin (αACT) deposited in half of the mature plaques and in one third of the CAA. Amyloid precursor protein (APP), ubiquitin (Ub), and microtubule-associated protein-2 (MAP-2) accumulated in the swollen neurites of mature plaques. Glial fibrillary acidic protein (GFAP) was detected in the astrocytes and their processes surrounding the mature plaques. Tau was detected in neither the SPs nor CAA. Therefore, mature plaques involved extracellular Aβ, apoE, and αACT, and also astrocytes and swollen neurites. However, diffuse plaques involved only extracellular Aβ and apoE. Since these features, except for tau, were consistent with those in humans, this animal model will be useful for studying the pathogenesis of cerebral amyloid deposition. 相似文献
55.
Shiraha H Koide N Hada H Ujike K Nakamura M Shinji T Gotoh S Tsuji T 《Biotechnology and bioengineering》1996,50(4):416-421
We designed a bioartificial liver support system in which encapsulated multicellular spheroids of rat hepatocytes were utilized as a bioreactor in a hollow fiber cartridge. The spheroids, formed in a positively charged polystyrene dish that contained hormonally defined medium, were encapsulated into microdroplets of agarose that contained about 9 x 10(7) rat hepatocytes. The medium, including 150 mL reservoir volume, was circulated in a closed circuit in which the cartridge was inserted. The pH and levels of dissolved oxygen were monitored and automatically regulated so that they were maintained within a constant range for 72 h. Albumin accumulated in the circuit at the rate of 2.0 mg/L/h in this system. When the bioreactor cells in the system were replaced with Hep G2 cells, a human hepatoblastoma cell line, albumin accumulated at the rate of 0.15 mg/L/h. The spheroids of primary culture hepatocytes had 13 times higher albumin-producing capacity than the aggregates of Hep G2. The serum of a patient with fulminant hepatic failure was circulated in this system with the spheroids of primary culture hepatocytes. The concentration of branched amino acid (BCAA) in the circuit significantly increased during the 48 h circulation, while the concentration of aromatic amino acid (AAA) and methionine decreased. The ratio of BCAA/AAA increased from 0.640 to 0.772, indicating that the hepatocyte spheroids had improved the imbalance of the amino acid profile in the serum. These findings indicate that this system may be a useful model for an artificial liver support. (c) 1996 John Wiley & Sons, Inc. 相似文献
56.
Streptomyces azureus ATCC 14921 harboured a plasmid pSA1 together with its chromosomal integrated sequence (pSA1int ). The att P site on the plasmid was located at ca 170 bp Bam HI- Sph I fragment by site-specific integration. The free form was generated from the integrated sequence during the development of its host mycelia in the solid culture, but not in the liquid culture. The free form seemed to elicit the formation of spontaneously developing pocks on its host mycelia in the solid culture. 相似文献
57.
Shinji Tokuyama Hiroyuki Miya Kazunori Hatano Takeshi Takahashi 《Applied microbiology and biotechnology》1994,40(6):835-840
A novel enzyme, N-acylamino acid racemase, was purified to homogeneity from Streptomyces atratus Y-53 and characterized. This enzyme catalyzes the interconversion of optically active N-acylamino acids. The relative molecular mass (Mr) of the enzyme was estimated to be about 41 000 and 244 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, respectively, indicating that the enzyme is composed of six subunits with an equal Mr. The enzyme showed a broad substrate specificity toward N-acylamino acids, such as N-acetylmethionine, N-chloroacetylphenylalanine and N-chloroacetylvaline. The apparent Michaelis constant (Km) values for N-acetyl-l-methionine and N-acetyl-d-methionine were calculated to be 15.2 and 5.6 mm, respectively. Enzyme activity was markedly enhanced by divalent metal ions, such as Co2+, Mg2+ and Mn2+, and was inhibited by metal-chelating reagent, indicating that the enzyme is a metalloenzyme. We propose to name the enzyme N-acylamino acid racemase (acylamino acid racemase).
Correspondence to: S. Tokuyama 相似文献
58.
Mutation analysis of the cellulose-binding domain of the Clostridium cellulovorans cellulose-binding protein A. 总被引:1,自引:0,他引:1 下载免费PDF全文
Cellulose-binding protein A (CbpA) has been previously shown to mediate the interaction between crystalline cellulose substrates and the cellulase enzyme complex of Clostridium cellulovorans. CbpA contains a family III cellulose-binding domain (CBD) which, when expressed independently, binds specifically to crystalline cellulose. A series of N- and C-terminal deletions and a series of small internal deletions of the CBD were created to determine whether the entire region previously described as a CBD is required for the cellulose-binding function. The N- and C-terminal deletions reduced binding affinity by 10- to 100-fold. Small internal deletions of the CBD resulted in substantial reduction of CBD function. Some, but not all, point mutations throughout the sequence had significant disruptive effects on the binding ability of the CBD. Thus, mutations in any region of the CBD had effects on the binding of the fragment to cellulose. The results indicate that the entire 163-amino-acid region of the CBD is required for maximal binding to crystalline cellulose. 相似文献
59.
Summary
Pseudomonas oleovorans grew well and synthesized copolyesters of 3-hydroxyalkanoates and 3-hydroxy--fluoroalkanoates in the mineral medium containing 1-fluorononane and sodium gluconate. The content of fluorinated units in copolyesters could be controlled from 0 to 40 mol%. The copolyesters were shown to have a random sequence distribution of different monomeric units by analysis of the13C NMR spectra. The melting temperatures of copolyesters were 52–58°C, and the enthalpy of fusion decreased with the content of fluorinated units. 相似文献
60.
Summary Using an ethanol solution of nile blue, we have developed an efficient method to detect the colonies of poly(3-hydroxyalkanoic
acids) (PHA) producing bacteria on the agar plate. When the bacterial colonies with PHA granules were stained with nile blue,
the stained colonies fluoresced bright orange on the irradiation of UV light. In the fluoresce emission spectra, fluorescence
intensity increased with an increase in the PHA content of bacterial cells.Alcaligenes eutrophus andA.latus colonies with poly(3-hydroxybutyric acid) (PHB) homopolymer exhibited an emission maximum at 580nm on the excitation at 490nm.
On the other hand,Pseudomonas oleovorans andP.putida with medium-chain-length (mcl-) PHA copolymers of C6, C8 and C10 units exhibited an emission maximum at 570nm. 相似文献