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91.
Chiral synthesis of secondary alcohols of both the (S)- and (R)-enantiomer with extremely high enantioselectivities (up to >99% ee) using a biocatalyst, Geotrichum candidum, is reviewed. Resting cell and dried-cell preparation using acetone were applied to oxidation, reduction, and deracemization reactions. Many methods to improve the reactivity and enantioselectivity of the reactions were developed. For example, additives such as secondary alcohols and hydrophobic resin (Amberlite XAD) were used in nonaqueous reaction media such as organic and supercritical solvents as well as in aqueous ones. As a result, optically pure alcohols of both enantiomers were synthesized on a gram scale. 相似文献
92.
Determination of the stereochemistry of (-)-koninginin A by an X-ray analysis of its synthetic sample 总被引:1,自引:0,他引:1
The absolute configuration of (-)-koninginin A [10-hexyl-11, 12-dioxatricyclo[7.2. 1.0<1 ,6>]dodecane-2,5-diol (1)], the antibiotic metabolite of Trichoderma koningii and T. harzianum, was determined as 1S, 2R, 5S, 6S, 9S, 10S by an X-ray crystallographic analysis of its synthetic sample coupled with the established stereochemical outcome of Sharpless asymmetric dihydroxylation used as the key reaction to prepare intermediate 4. 相似文献
93.
The vertebrate brain is regionalized during development into forebrain, midbrain and hindbrain. Fibroblast growth factor 8 (FGF8) is expressed in the midbrain/hindbrain boundary (MHB) and functions as an organizer molecule. Previous studies demonstrated that the brain of basal chordates or ascidians is also regionalized at least into fore/midbrain and hindbrain. To better understand the ascidian brain regionalization, the expression of the Ciona Fgf8/17/18 gene was compared with the expression of Otx, En and Pax2/5/8 genes. The expression pattern of these genes resembled that of the genes in the vertebrate forebrain, midbrain, MHB and hindbrain, each of those domains being characterized by sole or combined expression of Otx, Pax2/5/8, En and Fgf8/17/18. In addition, the putative forebrain and midbrain expressed Ci-FgfL and Ci-Fgf9/16/20, respectively. Therefore, the regionalization of the ascidian larval central nervous system was also marked by the expression of Fgf genes. 相似文献
94.
Establishment and characterization of a cell-line originated from human mucinous cystadenocarcinoma of the ovary 总被引:2,自引:0,他引:2
We recently established a cell line (designated 371M) derived from an ovarian mucinous cystadenocarcinoma. The tumor cells were obtained from the ascitic fluid of a 54-year-old Japanese woman while she was undergoing surgery. Adjuvant chemotherapy (combined paclitaxel and carboplatin) was administered, but was ineffective, and she died about 4 months after surgery. The 371M cells continuously propagated in vitro over a period of about 50 months and, to date, have undergone over 100 passages. They proliferated in a monolayered sheet with doubling times of 84 h and 37 h in the 10th and 34th passages, respectively. When transplanted into nude mice, the tumor histopathologically resembled the structure of the original tumor. The 371M cells secreted high levels of CA125 and CA19-9 into the culture medium. There were several abnormal chromosomes in all karyotypes selected at random. Sensitivity of 371M cells to a variety of anti-cancer drugs was examined by in vitro MTT assay, and the results suggested that CPT-11 and CDDP were more effective against 371M cells than other anti-cancer agents. 相似文献
95.
MAP kinase cascades in elicitor signal transduction 总被引:3,自引:0,他引:3
Suzuki K 《Journal of plant research》2002,115(3):0237-0244
Protein kinases play important roles in elicitor signal transduction. In this article, I describe the current view of the
role of mitogen-activated protein kinase (MAPK) cascades in elicitor signal transduction of plant cells based on our own research
and recent developments in this field. In the past several years, it has become apparent that MAPK cascades play important
roles in elicitor signal transduction in plants. Our early studies demonstrated the identification of p47 MAPK in tobacco
as an elicitor-responsive protein kinase and possible involvement of p47 MAPK in elicitor signal transduction to induce defense
responses, including defense gene expression and hypersensitive cell death. However, the molecular identity of p47 MAPK is
still unclear. Recent important studies suggest that tobacco MAPK cascades that include SIPK, and/or WIPK, and NtMEK2, an
upstream kinase for both SIPK and WIPK, have a crucial function in induction of defense responses and hypersensitive cell
death. The orthologs of these protein kinases in Arabidopsis and alfalfa are also suggested to have similar functions. Furthermore, the identification of loss-of-function mutation in
Arabidopsis reveals a negative regulatory role for putative MAPK cascades in plant defense mechanisms.
Received: February 7, 2002 / Accepted: February 25, 2002 相似文献
96.
97.
Hanashiro K Tokeshi Y Nakasone T Sunagawa M Nakamura M Kosugi T 《Mediators of inflammation》2002,11(1):61-64
We aim to clarify whether suplatast and azelastine (anti-allergic drugs) can shorten the half-life of imnunoglobulin E (IgE) in the circulating blood. Thirty Wistar rats were divided into six groups. Distilled water or anti-allergic drugs were given orally for 6 days after the first sensitization. Two milligrams of monoclonal dinitrophenyl (DNP)-specific rat IgE was administered to the rats, which had been given suplatast or azelastine orally. The level of DNP-specific rat IgE in the serum was estimated by IgE-capture enzyme-linked immunosorbent assay, and the turnover of IgE was analyzed from its pharmacokinetic parameters. The elimination half-life of rat IgE was about 12 h irrespective of the sensitized state. The intercompartmental rate constants (Kct and Ktc) in the suplatast-administered or azelastine-administered group were larger than those of the distilled water-administered group under non-sensitized conditions. These findings suggested that the anti-allergic drugs used in the present study facilitated the excretion of IgE from the circulation in rats. 相似文献
98.
99.
The XPC-HR23B complex displays high affinity and specificity for damaged DNA in a true-equilibrium fluorescence assay 总被引:5,自引:0,他引:5
The XPC-HR23B complex is a prime candidate for the initial damage recognition step during global genome nucleotide excision repair. A specific interaction between the XPC-HR23B complex and various types of damaged DNA substrates has been demonstrated in recent work by electrophoretic mobility shift assays or immunoprecipitation. Although these studies allowed the estimation of relative binding affinities for the different types of lesions, the presence of large amounts of competitor DNA or the need for glutaraldehyde fixation prevented the quantification of equilibrium constants. We have performed a quantitative study on the binding of XPC to damaged DNA using fluorescence anisotropy measurements. The XPC-HR23B complex binds with high affinity (K(D) approximately 1-3 nM) to fluorescent 36 bp DNA fragments containing a single cisplatin 1,3-intrastrand adduct or a six-nucleotide mispaired region. From stoichiometric titration experiments, it is concluded that approximately 70% of the XPC-HR23B preparation is active in DNA binding. Binding experiments employing fluorescent probes with a single defined photoproduct reveal a 30-fold preference of XPC for 6,4-photoproducts as compared to a cyclobutane dimer. Competition experiments with undamaged and damaged plasmid DNA indicate that the XPC-HR23B complex discriminates between damaged and undamaged sites with high specificity. The specificity factor is between 100 and 3000, depending on the number of nonspecific sites considered in the calculations. Upon addition of XPA to the XPC binding reaction mixtures, it was not possible to detect cooperative ternary complex formation on the platinated 36 bp probe. 相似文献
100.
Imai KS 《Differentiation; research in biological diversity》2003,71(6):346-360
Nuclear localization of beta-catenin is most likely the first step of embryonic axis formation or embryonic cell specification in a wide variety of animal groups. Therefore, the elucidation of beta-catenin target genes is a key research subject in understanding the molecular mechanisms of the early embryogenesis of animals. In Ciona savignyi embryos, nuclear accumulation of beta-catenin is the first step of endodermal cell specification. Previous subtractive hybridization screens of mRNAs between beta-catenin-overexpressed embryos and nuclear beta-catenin-depleted embryos have resulted in the identification of beta-catenin downstream genes in Ciona embryos. In the present study, I characterize seven additional beta-catenin downstream genes, Cs-cadherinII, Cs-protocadherin, Cs-Eph, Cs-betaCD1, Cs-netrin, Cs-frizzled3/6, and Cs-lefty/antivin. All of these genes were expressed in vegetal blastomeres between the 16-cell and 110-cell stages, although their spatial and temporal expression patterns were different from one another. In situ hybridizations and real-time PCR revealed that the expression of all of these genes was up-regulated in beta-catenin-overexpressed embryos, and down-regulated in beta-catenin-suppressed embryos. Therefore, the accumulation of beta-catenin in the nuclei of vegetal blastomeres activates various vegetally expressed genes with potentially important functions in the specification of these cells. 相似文献