全文获取类型
收费全文 | 13591篇 |
免费 | 883篇 |
国内免费 | 2篇 |
出版年
2022年 | 84篇 |
2021年 | 142篇 |
2019年 | 94篇 |
2018年 | 135篇 |
2017年 | 110篇 |
2016年 | 202篇 |
2015年 | 323篇 |
2014年 | 354篇 |
2013年 | 792篇 |
2012年 | 650篇 |
2011年 | 618篇 |
2010年 | 338篇 |
2009年 | 379篇 |
2008年 | 597篇 |
2007年 | 579篇 |
2006年 | 578篇 |
2005年 | 587篇 |
2004年 | 618篇 |
2003年 | 582篇 |
2002年 | 548篇 |
2001年 | 541篇 |
2000年 | 529篇 |
1999年 | 438篇 |
1998年 | 169篇 |
1997年 | 158篇 |
1996年 | 140篇 |
1995年 | 110篇 |
1994年 | 124篇 |
1993年 | 126篇 |
1992年 | 330篇 |
1991年 | 305篇 |
1990年 | 308篇 |
1989年 | 285篇 |
1988年 | 241篇 |
1987年 | 238篇 |
1986年 | 211篇 |
1985年 | 181篇 |
1984年 | 136篇 |
1983年 | 131篇 |
1982年 | 114篇 |
1981年 | 107篇 |
1980年 | 90篇 |
1979年 | 113篇 |
1978年 | 91篇 |
1977年 | 80篇 |
1976年 | 81篇 |
1975年 | 71篇 |
1974年 | 86篇 |
1973年 | 93篇 |
1971年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
291.
Summary Maximum production of alkaline serine protease by Bacillus alcalophilus subsp. halodurans KP 1239 was achieved after 24 h cultivation, at an initial pH of 7.6, on a medium containing 1.0% sodium citrate, 0.3% yeast extract, and 0.3% KH2PO4. The enzyme was purified to crystalline form from culture broth. The enzyme was most active at 60° C and at pH 11.5. The molecular weight, isoelectric point and sedimentation coefficient in water at 20° C were estimated as 29 000, 8.8 and 3.3S, respectively. The N-terminal amino acid sequence was Ala-Gln-Ser-Val-Pro-Trp-Gly-Ile-Ser-Arg-Val-Gln-Ala-Pro-Ala-Ala-His-Asn-Arg-Gly-. The enzyme shared its antigenic determinants with B. alcalophilus ATCC 21522 serine protease, but not with the subtilisins Carlsberg and BPN.
Offprint requests to: Yuzuru Suzuki 相似文献
292.
Hidekazu Sawada Takashi Suzuki Shun-ichi Akiyama Yoshio Nakao 《Applied microbiology and biotechnology》1990,32(5):556-559
Summary Gel-filtration analysis of a mixture of cyclodextrin (CyD) and lankacidin C showed that -CyD had strong, -CyD weak and -CyD no affinity for lankacidin C. Lankacidin C production activity, which was assayed by measuring the incorporation of l-[methyl-14C-]methionine into the lankacidin molecule, was the greatest with cells grown in the presence of -CyD, less with -CyD and the least with -CyD. Lankamycin and T-2636M, which are by-products in lankacidin C fermentation, were not included by -CyD and their production was not stimulated by -CyD. It was apparent that the stimulatory effect of CyD was closely related to the formation of an inclusion complex between CyD and the antibiotic. Lankacidin C biosynthesis was repressed by preincubating cells with lankacidin C, while the repressive effect of lankacidin C was abrogated by the inclusion by -CyD. Thus, abrogation of feed-back repression seems to be a main mechanism of the effect of CyD. However, -CyD, which had no affinity for lankacidin C, stimulated the production to the least extent and exhibited a complementary effect on the stimulation by -CyD or -CyD. -CyD also caused a change in cell morphology and cell-surface hydrophobicity. It was assumed that the modification of the cell surface is a secondary mechanism of the effect of CyD.The second report of the stimulatory effect of cyclodextrins on lankacidin fermentationOffprint requests to: H. Sawada 相似文献
293.
The three-dimensional structure of the seed storage protein phaseolin at 3 A resolution. 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M C Lawrence E Suzuki J N Varghese P C Davis A Van Donkelaar P A Tulloch P M Colman 《The EMBO journal》1990,9(1):9-15
The polypeptides of the trimeric seed storage protein phaseolin comprise two structurally similar units each made up of a beta-barrel and an alpha-helical domain. The beta-barrel has the 'jelly-roll' folding topology of the viral coat proteins and the alpha-helical domain shows structural similarity to the helix-turn-helix motif found in certain DNA-binding proteins. 相似文献
294.
Aortic endothelial cells synthesize a large chondroitin sulphate proteoglycan capable of binding to hyaluronate. 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
H Morita T Takeuchi S Suzuki K Maeda K Yamada G Eguchi K Kimata 《The Biochemical journal》1990,265(1):61-68
Confluent cultures of mouse aortic endothelial (END-D) were incubated with either [35S]methionine or 35SO4 2-, and the radiolabelled proteoglycans in media and cell layers were analysed for their hyaluronate-binding activity. The proteoglycan subfraction which bound to hyaluronate accounted for about 18% (media) and 10% (cell layers) of the total 35S radioactivity of each proteoglycan fraction. The bound proteoglycan molecules could be dissociated from the aggregates either by digestion with hyaluronate lyase or by treatment with hyaluronate decasaccharides. Digestion of [methionine-35S]proteoglycans with chondroitinase and/or heparitinase, followed by SDS/polyacrylamide-gel electrophoresis, indicated that the medium and cell layer contain at least three chondroitin sulphate proteoglycans, one dermatan sulphate proteoglycan, and two heparan sulphate proteoglycans which differ from one another in the size of core molecules. Among these, only the hydrodynamically large chondroitin sulphate species with an Mr 550,000 core molecule was shown to bind to hyaluronate. A very similar chondroitin sulphate proteoglycan capable of binding to hyaluronate was also found in cultures of calf pulmonary arterial endothelial cells (A.T.C.C. CCL 209). These observations, together with the known effects of hyaluronate on various cellular activities, suggest the existence of possible specialized functions of this proteoglycan subspecies in cellular processes characteristic of vascular development and diseases. 相似文献
295.
The effects of prostaglandin E2 (PGE2) and indomethacin on excitatory neuro-effector transmission in the human bronchus were investigated by tension recording and microelectrode methods. PGE2 (10−10–10−9M) suppressed the amplitude of twitch contractions and excitatory junction potentials (e.j.ps) evoked by field stimulation at a steady level of basal tension obtained by the combined application of indomethacin (10−5M) and FPL55712 (10−6M). In doses over 10−8M, PGE2 reduced the muscle tone and dose-dependently suppressed the amplitude of twitch contractions. Indomethacin (10−5 or 5 × 10−5M) reduced the muscle tone and enhanced the amplitude of twitch contractions and e.j.ps evoked by field stimulation in the presence of FPL55712. PGE2 (10−9M) had no effect on the post-junctional response of smooth muscle cells to exogenously applied acetylcholine (ACh) (4 × 10−7M). However, indomethacin (10−5M) significantly enhanced the ACh-induced contraction of the human bronchus. These results indicate that PGE2 in low concentrations has a pre-junctional action to inhibit excitatory neuro-effector transmission in addition to a post-junctional action, presumably by suppressing transmitter release from the vagus nerve terminals in the human bronchial tissues. 相似文献
296.
297.
The complete amino acid sequence of myoglobin from the triturative stomach of gastropodic molluscBursatella leachii has been determined. It is composed of 146 amino acid residues, is acetylated at the N-terminus, and contains a single histidine residue at position 95 which corresponds to the heme-binding proximal histidine. The E7 distal histidine, which is conserved widely in myoglobins and hemoglobins, is replaced by valine inBursatella myoglobin. The amino acid sequence ofBursatella myoglobin shows strong homology (73–84%) with those ofAplysia andDolabella myoglobins. 相似文献
298.
299.
Hiroko Tsukano Ken-Ichiro Itoh Sosuke Suzuki Haruo Watanabe 《Microbiology and immunology》1996,40(10):773-775
A PCR method for detection of Yersinia pestis-virulence determinants by the use of multiplex primers was developed. Four pairs of oligonucleotide primers were designed from each gene of three kinds of virulent plasmids and a chromosomal DNA; 60-Md plasmid-located gene (caf1) encoding Y. pestis-specific capsular antigen fraction 1, a Y. pestis-specific region of a yopM gene encoded on 42-Md virulent plasmid, a plasminogen activator gene (pla) encoded on Y. pestis-specific 7-Md plasmid and an invasin protein gene (inv) encoded on chromosomal DNA. This multiplex-primer system was specific for the detection of Y. pestis among pathogenic Yersinia species and other enterobacteriaceae having antigens common to Y. pestis. Since this method is simple and safe, it will be useful to identify and confirm Y. pestis in cases of emergency and for the surveillance of epidemics. 相似文献
300.
Comparison of OspA Serotypes for Borrelia burgdorferi Sensu Lato from Japan,Europe and North America
Toshiyuki Masuzawa Bettina Wilske Tetsuro Komikado Hiroyuki Suzuki Hiroki Kawabata Nanao Sato Koichi Muramatsu Nobutake Sato Emiko Isogai Hiroshi Isogai Russell C. Johnson Yasutake Yanagihara 《Microbiology and immunology》1996,40(8):539-545
Sixty-one Borrelia burgdorferi sensu lato strains from various sources (ticks, human, and wild animals) in Japan and two strains from ticks in Far Eastern Russia were classified on the basis of reactivity with 16 monoclonal antibodies (mAb) to outer surface protein A (OspA) and by DNA-DNA hybridization assay. Eleven OspA serotypes (J1 to J11) were recognized among the Japanese and the Far East Russian isolates (serotypes J1 to J9 were identified as B. garinii, serotype J10 was identified as B. afzelii, and serotype J11 corresponded to B. japonica), whereas 7 OspA serotypes for North American and European isolates previously reported (Bettina Wilske et al, J. Clin. Microbiol. 31:340-350, 1993) were not observed except for OspA serotype 2 which showed identical reactivity with OspA serotype J10. This finding provides helpful information for understanding the geographical distribution of Lyme disease borrelia and the development of vaccine and diagnostic tests. In conclusion: 1. B. burgdorferi sensu stricto has not been observed in Japan, 2. Japanese B. afzelii isolates are closely related to those from Europe, 3. B. garinii isolates from Japan are highly heterogeneous and apparently different from European B. garinii isolates. 相似文献