全文获取类型
收费全文 | 8138篇 |
免费 | 424篇 |
国内免费 | 6篇 |
出版年
2022年 | 39篇 |
2021年 | 72篇 |
2020年 | 42篇 |
2019年 | 46篇 |
2018年 | 90篇 |
2017年 | 78篇 |
2016年 | 141篇 |
2015年 | 192篇 |
2014年 | 235篇 |
2013年 | 810篇 |
2012年 | 413篇 |
2011年 | 495篇 |
2010年 | 288篇 |
2009年 | 272篇 |
2008年 | 477篇 |
2007年 | 488篇 |
2006年 | 502篇 |
2005年 | 510篇 |
2004年 | 477篇 |
2003年 | 463篇 |
2002年 | 530篇 |
2001年 | 88篇 |
2000年 | 73篇 |
1999年 | 92篇 |
1998年 | 138篇 |
1997年 | 103篇 |
1996年 | 99篇 |
1995年 | 93篇 |
1994年 | 83篇 |
1993年 | 121篇 |
1992年 | 91篇 |
1991年 | 58篇 |
1990年 | 46篇 |
1989年 | 62篇 |
1988年 | 50篇 |
1987年 | 51篇 |
1986年 | 44篇 |
1985年 | 47篇 |
1984年 | 59篇 |
1983年 | 37篇 |
1982年 | 73篇 |
1981年 | 55篇 |
1980年 | 58篇 |
1979年 | 29篇 |
1978年 | 39篇 |
1977年 | 26篇 |
1976年 | 34篇 |
1974年 | 20篇 |
1973年 | 24篇 |
1972年 | 20篇 |
排序方式: 共有8568条查询结果,搜索用时 296 毫秒
191.
Subcutaneous infection withYersinia enterocolitica harboring plasmid responsible for Ca2+ dependence at 37°C induced cell-mediated protective immunity against a lethal challenge withYersinia pestis; the isogenic derivative strain cured from this plasmid subverted the immunity in mice. This is the first identification of the antigen(s) responsible for the induction of cell-mediated protective immunity against the facultatively intracellular bacteria. 相似文献
192.
193.
Tohru Kotera Akira Hashimoto Shunji Ueda Yasunobu Okada 《The Journal of membrane biology》1991,124(1):43-52
Summary Patch-clamp studies of whole-cell ionic currents were carried out in parietal cells obtained by collagenase digestion of the gastric fundus of the guinea pig stomach. Applications of positive command pulses induced outward currents. The conductance became progressively augmented with increasing command voltages, exhibiting an outwardly rectifying current-voltage relation. The current displayed a slow time course for activation. In contrast, inward currents were activated upon hyperpolarizing voltage applications at more negative potentials than the equilibrium potential to K+ (E
K). The inward currents showed time-dependent inactivation and an inwardly rectifying current-voltage relation. Tail currents elicited by voltage steps which had activated either outward or inward currents reversed at nearE
K, indicating that both time-dependent and voltagegated currents were due to K+ conductances. Both outward and inward K+ currents were suppressed by extracellular application of Ba2+, but little affected by quinine. Tetraethylammonium inhibited the outward current without impairing the inward current, whereas Cs+ blocked the inward current but not the outward current. The conductance of inward K+ currents, but not outward K+ currents, became larger with increasing extracellular K+ concentration. A Ca2+-mobilizing acid secretagogue, carbachol, and a Ca2+ ionophore, ionomycin, brought about activation of another type of outward K+ currents and voltage-independent cation currents. Both currents were abolished by cytosolic Ca2+ chelation. Quinine preferentially inhibited this K+ current. It is concluded that resting parietal cells of the guinea pig have two distinct types of voltage-dependent K+ channels, inward rectifier and outward rectifier, and that the cells have Ca2+-activated K+ channels which might be involved in acid secretion under stimulation by Ca2+-mobilizing secretagogues. 相似文献
194.
195.
Takashi Tobe Shigeo Nakajo Atsutaka Tanaka Akira Mitoya Kumiko Omata Kazuyasu Nakaya Motowo Tomita Yasuharu Nakamura 《Journal of neurochemistry》1992,59(5):1624-1629
A new acidic protein with a molecular weight of 14,000 was purified from rat brain, in which it was specifically expressed, and partially sequenced by protein sequencing. On the basis of results obtained from the amino acid sequences, mixed oligonucleotides were synthesized and used as probes to clone a cDNA from a rat brain cDNA library. The cloned cDNA provided the full-length sequence of the 14-kDa protein. Northern blot hybridization using total RNA from several tissues of the rat provided evidence that the 14-kDa protein was expressed specifically in rat brain. Transfection of this cDNA into mammalian cells resulted in expression of the 14-kDa protein. The amino acid sequence predicted from the cDNA of the rat brain 14-kDa protein contained 137 amino acid residues. A hydropathy profile revealed a hydrophobic domain (amino acids 60-80) flanked by highly hydrophilic stretches on both sides. Whereas the N-terminal region of the 14-kDa protein contained four repeating motifs, EKTKEGV, the C-terminal domain was rich in glutamic acid and proline. A computer search of the amino acid sequence of the 14-kDa protein indicated no homology to any other protein reported so far. 相似文献
196.
Claire Zehnacker Thomas W. Becker Akira Suzuki Elisa Carrayol Michel Caboche Bertrand Hirel 《Planta》1992,187(2):266-274
Ferredoxin-dependent glutamate synthase (Fd-GOGAT, EC 1.4.7.1) was purified to electrophoretic homogeneity from leaves of tobacco (Nicotiana tabacum L.). The holoenzyme is a monomeric flavoprotein with a molecular weight of 164 kDa. Polyclonal rabbit antibodies against the purified enzyme were used to isolate a 450-bp Fd-GOGAT cDNA clone (C16) from a tobacco gt11 expression library. A longer Fd-GOGAT cDNA clone (C35) encoding about 70% of the amino acids of tobacco Fd-GOGAT was isolated from a tobacco gt10 cDNA library using C16 as the probe. The amino-acid sequence of the protein encoded by the Fd-GOGAT cDNA clone C35 was delineated. It is very likely that Fd-GOGAT is encoded by two genes in the amphidiploid genome of tobacco while only a single Fd-GOGAT gene appears to be present in the diploid genome of Nicotiana sylvestris. Two Fd-GOGAT isoenzymes could be distinguished in extracts of tobacco leaf protein. In contrast, a single Fd-GOGAT protein species was detected in leaves of Nicotiana sylvestris speg. et Comes. In tobacco leaves, the 6-kb Fd-GOGAT mRNA is about 50-fold less abundant than chloroplastic glutamine synthetase (EC 6.3.1.2) mRNA. Both Fd-GOGAT mRNA and Fd-GOGAT protein accumulated during greening of etiolated tobacco leaves, and a concomitant increase in Fd-GOGAT activity was observed. These results indicate that tobacco Fd-GOGAT gene expression is light-inducible. Levels of Fd-GOGAT mRNA in tobacco organs other than leaves were below the detection limit of our Northern-blot analysis. Polypeptides of Fd-GOGAT were present in tobacco leaves and, to a lesser extent, in pistils and anthers, but not in corollas, stems and roots. These results support organ specificity in tobacco Fd-GOGAT gene expression.Abbreviations bp
base pairs
- Fd-GOGAT
ferredoxin-dependent glutamate synthase
- GS
glutamine synthetase
- PAGE
polyacrylamide gel electrophoresis
- SDS
sodium dodecyl sulfate
The authors wish to thank Juan Luis Gómez Pinchetti (Marine Plant Biotechnology Laboratory) for his assistance during the experiments. This study was supported by grants received from SAREC (Swedish Agency for Research Cooperation with Developing Countries), Carl Tryggers Fund for Scientific Research (K. Haglund), SJFR (Swedish Council for Forestry and Agricultural Research) (M. Björk, M. Pedersén), CITYT Spain (SAB 89-0091 and MAR 91-1237, M. Pedersén) and CICYT Spain (Z. Ramazanov, invited professor of Ministerio de Educatión y Ciencia, Spain). The planning of this cooperation was facilitated by COST-48. 相似文献
197.
Proteins and Carbohydrates in Xylem Sap from Squash Root 总被引:8,自引:0,他引:8
Satoh Shinobu; Iizuka Chika; Kikuchi Akira; Nakamura Norio; Fujii Tadashi 《Plant & cell physiology》1992,33(7):841-847
The xylem sap from squash roots was collected from the cut surfaceof stems, and the proteins and carbohydrates in the sap wereanalyzed. The sap contained 18.6 µg ml1 proteinand the major polypeptides were as follows: 1) two polypeptides,of 75 and 40 kDa, with high-mannose glycans, the levels of whichincreased for about 24 h after cutting and then decreased; 2)a 32-kDa polypeptide, which appeared soon after cutting, disappearedand then reappeared again 4864 h after cutting; and 3)a 19-kDa and a 14-kDa polypeptide, which were present constitutively.The carbohydrates contained in the xylem sap were fractionatedinto 80% ethanol-soluble and -insoluble material, and whichwere analyzed by high-performance liquid chromatography, gaschromatography and enzymatic mathods. The former fraction containedconsiderable amounts of myo-inositol and fructose as free sugarsand oligosaccharides composed mainly of galactose, arabinoseand glucose. The latter contained polysaccharides composed mainlyof uronic acids, galactose and arabinose. The possible significanceof these substances, which may mediate the interactions betweenthe root and the aerial organs, is discussed. (Received April 20, 1992; Accepted July 4, 1992) 相似文献
198.
Kuriyama Akira; Takeuchi Masayuki; Kawai Fumio; Kanamori Masao 《Plant & cell physiology》1992,33(5):647-650
The formation of sporophytic shoots, which is induced by treatmentwith benzylaminopurine of gametophyte tissue of Equisetum arvense,can be divided into initiation and developmental phases. Thenitrogen in MS medium was suitable for two phases as well as gametophytic growth, buta reduction in the concentration of available nitrogen was neededfor the development of shoots. ions alone were effective for gametophytic growth and the initiationof sporophytic shoots, but both and ions was required for the developmental phase. (Received February 18, 1992; Accepted April 14, 1992) 相似文献
199.
Tomohiro Kiyosue Jiro Nakayama Shinobu Satoh Akira Isogai Akinori Suzuki Hiroshi Kamada Hiroshi Harada 《Planta》1992,186(3):337-342
ECP31, an embryogenic-cell protein from carrot (Daucus carota L.), was purified by sequential column-chromatographic steps and digested by V8 protease on a nitrocellulose membrane. The resultant peptides were separated by reverse-phased column chromatography and sequenced. The sequences obtained were 70–80% homologous to those of a late-embryogenesis-abundant protein (D34) from cotton (Baker et al, 1988, Plant Mol. Biol. 11, 227–291). The level of ECP31 in somatic embryos of carrot was increased by treatment of the embryos with 3.7 · 10–6 M abscisic acid (ABA) for 48 h, and there was no change in this enhanced level for up to 192 h in the presence of ABA. No similar enhancing effect of ABA was observed on the level of ECP31 in embryogenic callus or segments of carrot hypocotyls. In an immunohistochemical analysis, ECP31 was found in epidermal tissue and in the vascular system of ABA-treated somatic embryos.Abbreviations ABA
abscisic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- LEA protein
late-embryogenesis-abundant protein
To whom correspondence should be addressedThis work was supported in part by a grant-in-aid for Special Research in Priority Areas (Project No. 02242102) from the Ministry of Education, Science and Culture, Japan, and by Special Coordination Funds of the Science and Technology Agency of the Japanese Government. 相似文献
200.
Adenine depurination and inactivation of plant ribosomes by an antiviral protein of Mirabilis jalapa (MAP) 总被引:4,自引:0,他引:4
Jiro Kataoka Noriyuki Habuka Masashi Miyano Chikara Masuta Akira Koiwai 《Plant molecular biology》1992,20(6):1111-1119
Mirabilis antiviral protein (MAP) is a single-chain ribosome-inactivating protein (RIP) isolated from Mirabilis jalapa L. It depurinates the 28S-like rRNAs of prokaryotes and eukaryotes. A specific modification in the 25S rRNA of M. jalapa was found to occur during isolation of ribosomes by polyacrylamide/agarose composite gel electrophoresis. Primer extension analysis revealed the modification site to be at the adenine residue corresponding to A4324 in rat 28S rRNA. The amount of endogenous MAP seemed to be sufficient to inactivate most of the homologous ribosomes. The adenine of wheat ribosomes was also found to be removed to some extent by an endogenous RIP (tritin). However, the amount of endogenous tritin seemed to be insufficient for quantitative depurination of the homologous ribosomes.Endogenous MAP could shut down the protein synthesis of its own cells when it spreads into the cytoplasm through breaks of the cells. Therefore, we speculate that MAP is a defensive agent to induce viral resistance through the suicide of its own cells. 相似文献