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991.
Twelve species of the palm genus Aiphanes occur in Ecuador. The morphological variation in the genus is surveyed, and the distribution of the Ecuadorean species is discussed. A key to the species of Aiphanes in Ecuador is provided. Aiphanes chiribogensis, A. grandis , and A. verrucosa are described as new species, and illustrated. Aiphanes caryotifolia, A. eggersii, A. erinacea, A. fosteriorum, A. gela-tinosa, A. macroloba, A. schultzeana , and A. tricuspidata are characterized. One still unidentified species resembling A. tessmannii is discussed. 相似文献
992.
The life history characteristics of many species of seahorse, including the hedgehog seahorse Hippocampus spinosissimus, make them sensitive to exploitation. Consequently, proper management tools must be employed; these are often based on reliable ageing. The aim of the present study was to evaluate the possibility of using otoliths for ageing hedgehog seahorses from Vietnam. Asteriscus, lapillus and sagitta all showed moderate to strong correlations between fish standard length (SL), otolith length and number of increments in seahorses between 83 and 188 mm SL. There were no annual or seasonal marks in any of the three otolith pairs observed using dissecting or light microscopy, and only asteriscus revealed microincrements under light microscopy. The number of increments ranged between 71 and 137. A full trajectory of lapillar microincrements was only visible when using scanning electron microscopy, and then only in two of the examined individuals (88 and 115 increments). A validation experiment showed that the number of increments in the asterisci did not correspond to the age of seahorses bred and reared for 717 and 868 days. Furthermore, a second validation study using Alizarine Complexone (ALZ) otolith marking did not reveal any increments peripheral to the ALZ mark 30 days after marking. The conclusion of the study was that otoliths do not at present provide a reliable tool for estimating age in adult hedgehog seahorses, and therefore other tools have to be employed to improve their management. 相似文献
993.
Differential interactions of p23 and the TPR-containing proteins Hop, Cyp40, FKBP52 and FKBP51 with Hsp90 mutants 总被引:6,自引:2,他引:4
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Shiying Chen William P. Sullivan David O. Toft David F. Smith 《Cell stress & chaperones》1998,3(2):118-129
Hsp90 is required for the normal function of steroid receptors, but its binding to steroid receptors is mediated by Hsc70 and several hsp-associated accessory proteins. An assortment of Hsp90 mutants were tested for their abilities to interact with each of the following accessories: Hop, Cyp40, FKBP52, FKBP51, and p23. Of the 11 Hsp90 mutants tested, all were defective to some extent in associating with progestin (PR) complexes. In every case, however, reduced PR binding correlated with a defect in binding of one or more accessories. Co-precipitation of mutant Hsp90 forms with individual accessories was used to map Hsp90 sequences required for accessory protein interactions. Mutation of Hsp90's highly conserved C-terminal EEVD to AAVD resulted in diminished interactions with several accessory proteins, most particularly with Hop. Deletion of amino acids 661–677 resulted in loss of Hsp90 dimerization and also caused diminished interactions with all accessory proteins. Binding of p23 mapped most strongly to the N-terminal ATP-binding domain of Hsp90 while binding of TPR proteins mapped to the C-terminal half of Hsp90. These results and others further suggest that the N- and C-terminal regions of Hsp90 maintain important conformational links through intramolecular interactions and/or intermolecular influences in homodimers. 相似文献
994.
Henrik Wenzel 《The International Journal of Life Cycle Assessment》1998,3(5):281-288
The reason to perform an LCA is essentially to use it in support of a decision. A decision gives rise to a change somewhere
in society compared to a scenario in which this decision was not taken. The key requirement for the LCA in any application
is therefore, that it shall reflect the environmental change caused by the decision. It is found, that the need to differentiate
LCA methodology for the use in different applications is born by a few key characteristics of the decision to be supported.
The first key characteristic is the environmental consequence of the decision, i.e. the nature and extent of the environmental
change caused by the decision. When modelling the environmental change, its extent in time and space will differ between decision
types, thus giving rise to different requirements, primarily for the scoping and inventory phases of the LCA. Furthermore,
some decisions will imply trade-offs between different impact categories, while others will not, thus causing different requirements
for the impact assessment. The second key characteristic is the social and economic consequence of the decision, the magnitude
of which will influence the need for certainty, transparency and documentation. The third characteristic is the context in
which the decision is taken, including the decision maker and interested parties, implicitly influencing the impact assessment
and weighting. 相似文献
995.
Extracellular compounds isolated from embryogenic carrot cell suspension cultures increase, by 1.5 to 6-fold, end-stage embryo production when added back to carrot cultures initiating embryogenesis. The causative factors related to the enhancement of embryo production are most likely to be extracellular, high molecular weight proteins found in the embryo-free medium (EFM) after somatic embryos have been formed. The addition of heat-treated EFM to fresh cultures did not result in enhancing effects on the production of end-stage embryos. However, the addition of compounds precipitated from EFM, by high concentrations of salt, accelerated by four days the formation of comparable amounts of end-stage embryos and surpassed total end-stage embryo levels by a factor of 4-6, dependent on the precipitate dose. These results suggest that heat-labile polypeptide molecules may be responsible for growth factor-like effects during somatic embryogenesis. 相似文献
996.
Michael P. Doyle William R. WinchesterStanley H. Simonsen Ratna Ghosh 《Inorganica chimica acta》1994,220(1-2):193-199
The preparation and structural characterization of dirhodium(II) tetrakis[N,N-dimethyl-2-pyrrolidone-5(S)-carb- oxamide], Rh2(5S-DMAP)4, a new sterically-demanding catalyst for enantioselective metal carbene transformations, is described. The pyrrolidone ligands are arrayed around the dirhodium(II) core with two oxygen and two nitrogen donor atoms, each oriented cis, bound to each octahedral rhodium. The crystal structure of this compound has been determined to be that of Rh2(5S-DMAP)4(CH3CN)2·CH3CN·6H2O: space group P212121 with cell constants a= 12.685(4), b=15.050(3), c=24.035(4) Å; V=4588.5(1.9) Å3, Z=4, R=0.0316, Rh---Rh DISTANCE =2 4538(5) Å. Decreased activity for diazodecomposition catalyzed by Rh2(5S-DMAP)4 is observed, and enantiocontrol for cyclopropanation and carbon-hydrogen insertion is lower than expected by analogy to the corresponding di- rhodium(II) tetrakis[methyl 2-pyrrolidone-5(S)-carboxylate], Rh2(5S-MEPY)4 Electronic stabilization of the in- termediate metal carbene is absent in reactions catalyzed by Rh2(5S-DMAP)4. 相似文献
997.
pH
i
recovery in acid-loaded Ehrlich ascites tumor cells and pH
i
maintenance at steady-state were studied using the fluorescent probe BCECF.Both in nominally HCO
3
–
-free media and at 25 mm HCO
3
–
, the measured pH
i
(7.26 and 7.82, respectively) was significantly more alkaline than the pH
i
. value calculated assuming the transmembrane HCO
3
–
gradient to be equal to the Cl– gradient. Thus, pH
i
in these cells is not determined by the Cl– gradient and by Cl–/HCO
3
–
exchange.pH
i
recovery following acid loading by propionate exposure, NH
4
+
withdrawal, or CO2 exposure is mediated by amiloride-sensitive Na+/H+ exchange in HCO3
– free media, and in the presence of HCO
3
–
(25 mm) by DIDS-sensitive, Na+-dependent Cl–/HCO
3
–
exchange. A significant residual pH
i
recovery in the presence of both amiloride and DIDS suggests an additional role for a primary active H+ pump in pH
i
regulation. pH
i
maintenance at steady-state involves both Na+/H+ exchange and Na+-dependent Cl–/HCO
3
–
exchange.Acute removal of external Cl– induces a DIDS-sensitive, Na+-dependent alkalinization, taken to represent HCO
3
–
influx in exchange for cellular Cl–. Measurements of 36Cl– efflux into Cl–-free gluconate media with and without Na+ and/or HCO
3
–
(10 mm) directly demonstrate a DIDS-sensitive, Na+
dependent Cl–/HCO
3
–
exchange operating at slightly acidic pH
i
(pHo 6.8), and a DIDS-sensitive, Na+-independent Cl–/HCO
3
–
exchange operating at alkaline pH
i
(pH
o
8.2).The excellent technical assistance of Marianne Schiødt and Birgit B. Jørgensen is gratefully acknowledged. The work was supported by the Carlsberg Foundation (B.K.) and by a grant from the Danish Natural Science Foundation (E.K.H. and L.O.S.). 相似文献
998.
Hans Henrik Saxild Jan Hassan Jacobsen Per Nygaard 《Molecular & general genetics : MGG》1994,242(4):415-420
We have found that Bacillus subtilis possesses a second 5-phosphoribosyl-1-glycinamide (GAR) transformylase catalysing the first one-carbon transfer reaction in the purine biosynthetic pathway. Inactivation of the purN gene encoding the N10-formyl tetrahydrofolate-dependent enzyme did not result in purine auxotrophy. However, growth of a purN strain was stimulated when either purine or formate was added to the growth medium. In cell-free extracts GAR could be formylated, provided formate was added to the assay mixture. From the purN strain, purine-requiring mutants were isolated. One of these mutant strains was defective in the formate-dependent formylation of GAR in vitro. The gene containing this second mutation was designated purT, and was mapped to approximately 20° on the genetic map between the cysA and aroI markers. 相似文献
999.
Lise Mossin Henrietta Blankson Henrik Huitfeldt Per O. Seglen 《Experimental cell research》1994,214(2)
The proliferative activity of rat hepatocytes, cultured in the presence of epidermal growth factor (EGF) and insulin, was examined by immunostaining of S-phase cells labeled with bromodeoxyuridine (BrdU) in culture. Proliferation rates of the different hepatocellular ploidy and nuclearity classes were measured by fluorescence image cytometry or by microscope counting of immunostained cells. Effects of EGF and insulin were largely additive, the binuclear cells being more growth factor-dependent (showing less growth in the absence of factors) than the mononuclear cells. A serial warm-washing procedure was used to remove excess BrdU from the culture medium, allowing the study of hepatocellular binucleation by a BrdU pulse-chase approach. A high rate of binucleation was detected (50%, possibly suggesting a quantal mechanism), indicating that the hormones induce a binucleating (polyploidizing) type of growth similar to that normally observed in the liver of growing rats. The highest proliferative activity (labeling index) in the hepatocyte cultures was found among the diploid cells, independent of the degree of mitogenic stimulation. The labeling index was inversely correlated with ploidy, suggesting that the ability of hepatocytes to proliferate decreases with increasing polyploidization. 相似文献
1000.
Henrik Leffers Morten S. Nielsen Annette H. Andersen Bent Honor Peder Madsen Joël Vandekerckhove Julio E. Celis 《Experimental cell research》1993,209(2)
Proteins (IEF's 1120, 8118, 8120) sharing similarity to the bovine Rho GDP dissociation inhibitor (GDI) have been identified in the human two-dimentional-gel database of keratinocyte proteins. Molecular cloning of the corresponding cDNAs showed that IEF 8118 is the human homolog of bovine GDI while IEF 8120 is a distinct although related protein. All available information indicates the IEF 1120 is a derivative of IEF 8120. The cDNAs coding for IEF's 8118 and 8120 were recombined into vaccinia virus and expressed in differentiated human keratinocytes and their effect on the actin cytoskeleton was assessed by immunofluorescence using TRITC-phalloidin. The results showed that overexpression of both GDI proteins leads to rounding up of the cells and loss of stress fibers and focal contact sites. In addition, the cell to cell adhesion belts gradually disappeared, an effect that was particularly pronounced in infected cells overexpressing IEF 8120. Taken together, the results imply that Rho GDI's play a role in modulating the activity of the Rho proteins as their overexpression mimics phenotypic changes associated with the inactivation of these proteins. 相似文献