全文获取类型
收费全文 | 11695篇 |
免费 | 908篇 |
国内免费 | 287篇 |
出版年
2022年 | 74篇 |
2021年 | 116篇 |
2020年 | 76篇 |
2019年 | 126篇 |
2018年 | 117篇 |
2017年 | 149篇 |
2016年 | 183篇 |
2015年 | 245篇 |
2014年 | 336篇 |
2013年 | 670篇 |
2012年 | 589篇 |
2011年 | 566篇 |
2010年 | 396篇 |
2009年 | 382篇 |
2008年 | 553篇 |
2007年 | 565篇 |
2006年 | 515篇 |
2005年 | 515篇 |
2004年 | 519篇 |
2003年 | 528篇 |
2002年 | 482篇 |
2001年 | 471篇 |
2000年 | 479篇 |
1999年 | 380篇 |
1998年 | 146篇 |
1997年 | 153篇 |
1996年 | 113篇 |
1995年 | 122篇 |
1994年 | 117篇 |
1993年 | 106篇 |
1992年 | 268篇 |
1991年 | 238篇 |
1990年 | 236篇 |
1989年 | 234篇 |
1988年 | 231篇 |
1987年 | 189篇 |
1986年 | 197篇 |
1985年 | 167篇 |
1984年 | 121篇 |
1983年 | 134篇 |
1982年 | 111篇 |
1981年 | 74篇 |
1980年 | 75篇 |
1979年 | 120篇 |
1978年 | 73篇 |
1977年 | 74篇 |
1975年 | 55篇 |
1973年 | 58篇 |
1972年 | 53篇 |
1970年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
961.
Fujii K Yamamoto R Tanaka T Hirakawa T Kikuchi S 《Journal of industrial microbiology & biotechnology》2003,30(9):531-535
Sphingomonas cloacae S-3T, a nonylphenol (NP)-degrading bacterium, was evaluated for its utility in the remediation of NP-contaminated wastewater. In flask-scale experiments, S-3T cells immobilized on porous polypropylene carriers (beads) efficiently degraded NP to concentrations routinely measured in aquatic environments [a few parts per billion (ppb), or micrograms per liter). Therefore, we constructed and evaluated a laboratory-scale wastewater treatment system with a 3-l carrier-filled column. The system worked properly and consistently removed several hundred ppb of NP to ecologically safe concentrations of less than 10 ppb in industrial wastewater without the addition of nutrients. The effect of wastewater pH on the system performance was also evaluated; and wastewater samples with pH values of 6 or 8 were treated efficiently without pH adjustment. These results suggest that a biotreatment system using NP-degrading bacteria can efficiently remediate industrial wastewater and contribute to the preservation of aquatic environments. 相似文献
962.
Okada Anzu Okada Takashi Ide Takeshi Itoh Mituaki Tanaka Kunisuke Takaiwa Fumio Toriyama Kinya 《Molecular breeding : new strategies in plant improvement》2003,12(1):61-70
Recombinant Cry j 1, a Japanese cedar pollen allergen, was produced in rice seeds for potential use for oral immunotherapy. Cry j 1 cDNA was divided into two parts, an N-terminal half and a C-terminal half, and each was fused downstream to glutelin GluB-1 gene containing sequences of the promoter, 5 untranslated region and signal peptide. A gene for green fluorescent protein was also fused to the 3 end of the Cry j 1 fragment. Recombinant Cry j 1 of up to 16.6 g per mg total protein of the seeds was expressed in transgenic rice seeds. Although the recombinant Cry j 1 was expected to be accumulated in protein body II because of the employment of glutelin signal peptide, it was demonstrated to be accumulated exclusively in protein body I. The recombinant Cry j 1 was not shown to react with IgE of allergic patients, indicating the reduction of the risk of anaphylactic reaction. These results demonstrate that the transgenic rice seeds with the recombinant Cry j 1 would be useful for the study of oral immunotherapy. 相似文献
963.
Ueda M Kinoshita H Yoshida T Kamasawa N Osumi M Tanaka A 《FEMS microbiology letters》2003,219(1):93-98
3-Amino-1,2,4-triazole (3-AT) is known as an inhibitor of catalase to whose active center it specifically and covalently binds. Subcellular fractionation and immunoelectronmicroscopic observation of the yeast Candida tropicalis revealed that, in 3-AT-treated cells in which the 3-AT was added to the n-alkane medium from the beginning of cultivation, catalase transported into peroxisomes was inactivated and was present as insoluble aggregated forms in the organelle. The aggregation of catalase in peroxisomes occurred only in these 3-AT-treated cells and not in cells in which 3-AT was added at the late exponential growth phase. Furthermore, 3-AT did not affect the transportation of catalase into peroxisomes. The appearance of aggregation only in cells to which 3-AT was added from the beginning of cultivation suggests that, in the process of catalase transportation into yeast peroxisomes, some conformational change may take place and that correct folding may be inhibited by the binding of 3-AT to the active center of catalase. Accordingly, 3-AT will be an interesting compound for investigation of the transport machinery of the peroxisomal tetrameric catalase. 相似文献
964.
Tyrosine phosphorylation of a novel 100-kDa protein coupled to CD28 in resting human T cells is enhanced by a signal through TCR/CD3 complex 总被引:1,自引:0,他引:1
Matsumoto A Dobashi H Ohnishi H Tanaka T Kubota Y Kitanaka A Ishida H Tokuda M Waki M Kubo A Ishida T 《Microbiology and immunology》2003,47(1):63-69
For T cell activation, two signals are required, i.e., a T cell receptor (TCR)/CD3-mediated main signal and a CD28-mediated costimulatory signal. CD28 binds to its ligand (CD80 or CD86) and transduces the most important costimulatory signal. The cytoplasmic domain of the CD28 molecule, composed of 41 amino acids, does not contain any intrinsic enzyme activity. The cytoplasmic domain of CD28 is remarkably conserved among species and is associated with a number of signaling molecules that affect the main signal. We report here that a tyrosine phosphorylated 100-kDa protein (ppl00) was coupled to the CD28 cytoplasmic domain in Jurkat and human peripheral T cells. The pp100 was distinguished from other CD28 associated molecules such as Vav, STAT5, PI 3-kinase, Valosin-containing protein (VCP), Nucleolin, Gab2 (Grb2-associated binding protein 2), and STAT6. The tyrosine phosphorylation of pp100 coprecipitated with CD28 was enhanced by CD3 stimulation by the specific antibody, tyrosine phosphatase inhibitor and PKC activator. Tyrosine phosphorylation of pp100 was attenuated by the prior addition of PKC inhibitor. These findings indicate that pp100 is a novel tyrosine phosphorylated protein coupled to CD28 under continuous control of tyrosine phosphatases and might play a role in T cell activation augmented by a TCR/CD3-mediated main signal. 相似文献
965.
Maruyama S Kabeya H Nakao R Tanaka S Sakai T Xuan X Katsube Y Mikami T 《Microbiology and immunology》2003,47(2):147-153
Seroprevalence of Bartonella henselae, Toxoplasma gondii, feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) infections was investigated in 1,447 domestic cats derived from the north (Hokkaido) to the south (Okinawa) prefectures in Japan. Of the cats investigated, 8.8% (128/1,447) were seropositive to B. henselae, 5.4% (78/1,447) to T. gondii, 9.8% (107/1,088) to FIV, and 2.9% (32/1,088) to FeLV, respectively. For B. henselae infection, the positive rate varied from 11.5% in cats of 1 to <2 years old to 7.2% in those over 3 years old. Outdoor cats showed higher positive rate (14.5%) than that (7.0%) in indoor ones. The rate (13.5%) in flea-infested cats was significantly higher than that (7.4%) in flea-negative cats. The positive rates in southern and urban sites were more likely to be higher than those in northern and suburban sites, suggesting that warm and humid environments, density of cat population, and raising status, including hygienic condition and flea infestation in cats may correlate to higher seroprevalence of B. henselae infection. For T. gondii, FIV and FeLV infections, the seroprevalence also tended to be higher in outdoor, flea-infested cats and advanced age groups. For FIV infection, the positive rates in male (14.3%) and outdoor cats (15.0%) were significantly higher than those in female (5.0%) and indoor cats (4.6%). On the other hand, no significant difference in seropositivities was observed in FeLV and T. gondii infections concerning to both genders and raising status. 相似文献
966.
Sexual modification of female spinach seeds (Spinacia oleracea L.) by irradiation with ion particles
The female seeds of a spinach plant (Spinacia orelacea L.) were exposed to He (12.5 MeV/n) and C (18.3 MeV/n) ions in order to investigate the effects of ion particles on sex expression. He ions did not affect germination rates or flowering at doses up to 50 Gy. C ions did not affect germination rates or flowering at doses up to 15 Gy, but a dose of 25 Gy resulted in many plants with morphological aberrations. When unexposed female plants were grown without cross-fertilization for 10 weeks after sowing, 5.6-14.3% of the plants produced anthers from female flowers. These sex-modified plants could self-pollinate and form seeds, which expressed only female organs. Conversely, gynomonoecious plants were induced from these female seeds by exposure to He ions (5-50 Gy) and C ions (5-25 Gy) without any difference in the rates of flowered progeny. Moreover, andromonoecious plants were induced from female seeds by exposure to He ions at 50 Gy. These results suggest that the sex of a spinach plant is expressed as a flexible phenotype, converging from female to gyno- and andromonoecy after exposure to ion particles. 相似文献
967.
Microsomal omega-3 fatty acid desaturase is an essential enzyme in the production of the n-3 polyunsaturated fatty acid alpha-linolenic acid during the seed developing stage. We have constructed a chimeric gene consisting of a maize Ubi1-P-int and a soybean GmFAD3 cDNA, which was introduced into rice plants by Agrobacterium-mediated transformation. Ten transformants containing the chimeric gene were established and expression subsequently confirmed by Northern blotting. Furthermore, alpha-linolenic acid content of the T(1) seeds increased dramatically up to tenfold that of the control, and this phenotype was also stably inherited in the T(2) and T(3) progenies. These results demonstrate that the alpha-linolenic acid content of rice seed oil can easily be altered using the combination of a high-activity promoter and a GmFAD3 gene. 相似文献
968.
Thelephantins D-H: five p-terphenyl derivatives from the inedible mushroom Thelephora aurantiotincta
Ngoc Quang D Hashimoto T Hitaka Y Tanaka M Nukada M Yamamoto I Asakawa Y 《Phytochemistry》2003,63(8):919-924
Five p-terphenyl derivatives named thelephantins D-H (1-5) together with nine known compounds, thelephantins A-C (6-8), ganbajunin E (9), p-hydroxylbenzoic acid (10), ganbajunin C (11), thelephorin A (12), 2-O-methylatromentin (13) and atromentin (14), were isolated from the methanolic extract of fruit bodies of the Thelephoraceous Basidiomycete Thelephora aurantiotincta. Their structures were elucidated by high-resolution MS, 2D NMR, IR and UV spectroscopic analysis. 相似文献
969.
Aciculosporium take (Ascomycota; Clavicipitaceae), causes the witches' broom disease in bamboo, particularly Phyllostachys bambusoides. Since it was observed that endogenous indole-3-acetic acid is reduced in the twigs of the diseased bamboo, the symptoms (bushy appearance) may be induced by reduction in auxin levels. Furthermore, two indolic compounds accumulated in diseased twigs, these being identified as N-p-coumaroylserotonin and N-feruloylserotonin by LC-MS, 1H NMR and 13C NMR spectroscopic analyses. N-p-Coumaroylserotonin possesses antifungal activity against A. take. 相似文献
970.
An arylbenzofuran, erypoegin F and four isoflavonoids, erypoegins G-J, together with six known compounds were isolated from the roots of Erythrina poeppigiana, and their structures were elucidated on the basis of spectroscopic evidence. Erypoegin F is a rare 2-arylbenzofuran possessing a formyl group from a natural source, and erypoegin I is the first naturally occurring isoflavonoid with a 2-oxo-3-methylbutyl group. 相似文献