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51.
52.
Higurashi M Ohtsuki T Inase A Kusumoto R Masutani C Hanaoka F Iwai S 《The Journal of biological chemistry》2003,278(51):51968-51973
The (6-4) photoproduct formed by ultraviolet light is known as an alkali-labile DNA lesion. Strand breaks occur at (6-4) photoproducts when UV-irradiated DNA is treated with hot alkali. We have analyzed the degradation reaction of this photoproduct under alkaline conditions using synthetic oligonucleotides. A tetramer, d(GT(6-4)TC), was prepared, and its degradation in 50 mm KOH at 60 degrees C was monitored by high performance liquid chromatography. A single peak with a UV absorption spectrum similar to that of the starting material was detected after the reaction, and this compound was regarded as an intermediate before the strand break. The formation of this intermediate was compared with intermediates from the degradation of other alkali-labile lesions such as the abasic site, thymine glycol, and 5,6-dihydrothymine. The results strongly suggested that the first step of the alkali degradation of the (6-4) photoproduct was the hydrolysis between the N3 and C4 positions of the 5'-pyrimidine component. Analyses by NMR spectroscopy and mass spectrometry supported the chemical structure of this product. Assays of the complex formation with XPC.HR23B and the translesion synthesis by DNA polymerase eta revealed that the biochemical properties are indistinguishable between the intact and hydrolyzed photoproducts. 相似文献
53.
The Chlamydomonas outer dynein arm contains three distinct heavy chains (alpha, beta, and gamma) that exhibit different motor properties. The LC4 protein, which binds 1-2 Ca2+ with KCa = 3 x 10-5 m, is associated with the gamma heavy chain and has been proposed to act as a sensor to regulate dynein motor function in response to alterations in intraflagellar Ca2+ levels. Here we genetically dissect the outer arm to yield subparticles containing different motor unit combinations and assess the microtubule-binding properties of these complexes both prior to and following preincubation with tubulin and ATP, which was used to inhibit ATP-insensitive (structural) microtubule binding. We observed that the alpha heavy chain exhibits a dominant Ca2+-independent ATP-sensitive MT binding activity in vitro that is inhibited by attachment of tubulin to the structural microtubule-binding domain. Furthermore, we show that ATP-sensitive microtubule binding by a dynein subparticle containing only the beta and gamma heavy chains does not occur at Ca2+ concentrations below pCa 6 but is maximally activated above pCa 5. This activity was not observed in mutant dyneins containing small deletions in the microtubule-binding region of the beta heavy chain or in dyneins that lack both the alpha heavy chain and the motor domain of the beta heavy chain. These findings strongly suggest that Ca2+ binding directly to a component of the dynein complex regulates ATP-sensitive interactions between the beta heavy chain and microtubules and lead to a model for how individual motor units are controlled within the outer dynein arm. 相似文献
54.
Kimoto H Nomura M Kobayashi M Mizumachi K Okamoto T 《Canadian journal of microbiology》2003,49(11):707-711
One of the important properties of probiotics is the ability to survive in the intestine. There have been few studies on the probiotic property of lactococci, since they are formally not considered to be natural inhabitants of the intestine. To evaluate lactococci as probiotic bacteria, we investigated their ability to survive during gastric transit by in vitro and in vivo tests. When exposed to an in vitro simulated gastrointestinal environment, such as low pH and bile, only Lactococcus lactis subsp. lactis bv. diacetylactis N7 showed a moderate survival rate among the four strains tested. The tested strains were orally administered to mice, and intestinal passage of the ingested strains was monitored by two methods: antibiotics and PCR. Viable cells of strain N7 were recovered from feces within 24-48 h after administration but not at 72 h. Lactococcus lactis subsp. cremoris ATCC 19257, which had a poor survival rate in vitro test, was also detected at 12 h but not at 24 h. These results indicate that lactococci can reach the mouse intestine alive, but not colonize it. If administered daily, viable strain N7 may exist continuously in the intestine. The effect of strain N7 on intestinal microbial balance and on animal health will be the subject of a further study. 相似文献
55.
Kouki T Kishitake M Okamoto M Oosuka I Takebe M Yamanouchi K 《Hormones and behavior》2003,44(2):140-145
It is well known that neonatal exposure to estrogen induces masculinization or defeminization of the brain. In this study, the effects of neonatal treatment with two kinds of soybean isoflavone aglycone, genistein (GS) and daidzein (DZ), on the estrous cycle and lordosis behavior were investigated. Female rats were injected subcutaneously with 1 mg GS, 1 mg DZ, 100 microg estradiol (E2), or oil daily for 5 days from birth. As a result, vaginal opening was advanced in GS- or E2-treated females. A vaginal smear check indicated that oil- or DZ-treated females showed a constant 4- or 5-day estrous cycle, whereas GS- or E2-treated rats showed a persistent or prolonged estrus. Ovariectomy was performed in all females at 60 days of age. The ovaries in the GS- or E2-treated groups were smaller than those in the oil- and DZ-treated groups and contained no corpora lutea. In the DZ group, although corpora lutea were seen, ovaries were smaller than that of control females. Behavioral tests were carried out after implantation of E2-tubes. All of the oil- or DZ-treated females showed lordosis with a high lordosis quotient (LQ). On the other hand, as male rats, LQs were extremely low in the E2-treated group, when compared to the oil-treated group. In the GS-treated group, the mean LQ was lower than that in the oil-treated group, but higher than those in the E2-treated female or male groups. These results suggest that genistein acts as an estrogen in the sexual differentiation of the brain and causes defeminization of the brain in regulating lordosis and the estrous cycle in rats. In addition, neonatal daidzein also has some influence on ovarian function. 相似文献
56.
Ueda HR Matsumoto A Kawamura M Iino M Tanimura T Hashimoto S 《The Journal of biological chemistry》2002,277(16):14048-14052
Circadian rhythms govern the behavior, physiology, and metabolism of living organisms. Recent studies have revealed the role of several genes in the clock mechanism both in Drosophila and in mammals. To study how gene expression is globally regulated by the clock mechanism, we used a high density oligonucleotide probe array (GeneChip) to profile gene expression patterns in Drosophila under light-dark and constant dark conditions. We found 712 genes showing a daily fluctuation in mRNA levels under light-dark conditions, and among these the expression of 115 genes was still cycling in constant darkness, i.e. under free-running conditions. Unexpectedly the expression of a large number of genes cycled exclusively under constant darkness. We found that cycling in most of these genes was lost in the arrhythmic Clock (Clk) mutant under light-dark conditions. Expression of periodically regulated genes is coordinated locally on chromosomes where small clusters of genes are regulated jointly. Our findings reveal that many genes involved in diverse functions are under circadian control and reveal the complexity of circadian gene expression in Drosophila. 相似文献
57.
58.
The mammalian immune system has cytotoxic mechanisms, both cellular and humoral, that destroy the membrane integrity of target
cells. The main effector molecules of these cytolytic mechanisms—perforin, used by killer lymphocytes, and the membrane attack
complex (MAC) components of the complement system—share a unique module called the MAC/perforin module. Until now, both immunological
cytotoxicity and the MAC/perforin module have been reported only in jawed vertebrates. Here, we report the identification
of a protein containing the MAC/perforin module from the invertebrate cephalochordate, amphioxus (Branchiostoma belcheri), using expressed sequence tag (EST) analysis of the notochord. The deduced amino acid sequence of this molecule is most
similar to the primary structure of human complement component C6 and is designated AmphiC6. AmphiC6 shares a unique modular
structure, including the MAC/perforin module, with human C6 and other MAC components. Another EST clone predicts the presence
of a thioester-containing protein with the closest structural similarity to vertebrate C3 (therefore designated AmphiC3).
AmphiC3 retains most of the functionally important residues of vertebrate C3 and is shown by phylogenetic analysis to be derived
directly from the common ancestor of vertebrate C3, C4, and C5. Only opsonic activity has been assigned to the invertebrate
complement system until now. Therefore, this is the first molecular evidence for complement-mediated immunological cytotoxicity
in invertebrates.
Received: 24 August 2001 / Accepted: 12 November 2001 相似文献
59.
Ichiro Tabuchi Sayaka Soramoto Miho Suzuki Koichi Nishigaki Naoto Nemoto Yuzuru Husimi 《Biological procedures online》2002,4(1):49-54
The “in vitro virus” is a molecular construct to perform evolutionary protein engineering. The “virion(=viral particle)”(mRNA-peptide fusion),
is made by bonding a nascent protein with its coding mRNA via puromycin in a test tube for in vitro translation. In this work, the puromycin-linker was attached to mRNA using the Y-ligation, which was a method of two single-strands
ligation at the end of a double-stranded stem to make a stem-loop structure. This reaction gave a yield of about 95%. We compared
the Y-ligation with two other ligation reactions and showed that the Y-ligation gave the best productivity. An efficient amplification
of the in vitro virus with this “viral genome” was demonstrated.
Published: October 28, 2002 相似文献
60.
Induction and activation of the transcription factor NFATc1 (NFAT2) integrate RANKL signaling in terminal differentiation of osteoclasts 总被引:15,自引:0,他引:15