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61.
haemolysin of Escherichia coli: Comparison of pore-forming properties between chromosome and plasmid-encoded haemolysins 总被引:3,自引:0,他引:3
Roland Benz reas Döbereiner Albrecht Ludwig Werner Goebel 《FEMS microbiology letters》1992,105(1-3):55-62
Abstract Lipid bilayer experiments were performed with chromosome-encoded haemolysin of Escherichia coli . The addition of the toxin to the aqueous phase bathing lipid bilayer membranes of asolectin resulted in the formation of transient ion-permeable channels with two states at small transmembrane voltages. One is prestate (single-channel conductance 40 pS in 0.15 M KCl) of the open state, which had a single-channel conductance of 420 pS in 0.15 M KCl and a mean lifetime of 30 s. Membranes formed of pure lipids were rather inactive targets for this haemolysin. Experiments with different salts suggested that the haemolysin channel was highly cation-selective at neutral pH. The mobility sequence of the cations in the channel was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with a wide, water-filled channel with an estimated minimal diameter of about 1 nm. The pore-forming properties of chromosome-encoded haemolysin were compared with those of plasmid-encoded haemolysin. Both toxins share common features, oligomerize probably to form pores in lipid bilayer membranes. Both types of haemolysin channels have similar properties but different lifetimes. 相似文献
62.
Coen van den Berg Ferdinand A. Sibbing Jan W. M. Osse Wim Hoogenboezem 《Environmental Biology of Fishes》1992,33(1-2):105-124
Synopsis The filter feeding organ of cyprinid fishes is the branchial sieve, which consists of a mesh formed by gill rakers and tiny channels on the gill arches. In order to establish its possible role during growth we measured the following morphological gill raker parameters over a range of sizes in three cyprinid fishes, bream, white bream and roach: inter raker distance, bony raker length, raker width, cushion length and channel width. At any given standard length common bream has the largest inter raker distance, roach the lowest and white bream is intermediate. In the comb model of filter feeding the inter raker distance is considered to be a direct measure of the mesh size and retention ability (= minimal size of prey that can be retained) of a filter. For the three species under study there is a conflict between the comb model and experimental data on particle retention. Lammens et al. (1987) found that common bream has a large retention ability whereas roach and white bream have a much smaller one. A new model, the channel model (Hoogenboezem et al. 1991) has been developed for common bream; in this model the lateral gill rakers can regulate the mesh size of the medial channels on the other side of the gill slit. The present data indicate that this model is not appropriate for white bream and roach. At any given standard length white bream and roach only reach 70% of the raker length of common bream, which means that in this model the gill slits should to be very narrow during filter feeding. The gill rakers consist of a bony raker and a fleshy cushion. The bony rakers have a rather long needle-like part outside the cushion in bream, but not in white bream and roach which have blunt gill rakers. Blunt gill rakers are not suited to reduce the diameter of the medial channels. The comb model seems more appropriate for white bream and roach, but doubts about the validity of this simple model remain. The sum of the areas of the medial channels is an approximation of the area through which water flows in the filter. This channel area therefore gives an impression of the capacity or flow rate of the filter. With this capacity estimation and an estimation of energy consumption we calculated an energy ratio of filter feeding. The energy ratio decreases with increasing standard length with an exponent close to the expected exponent of -0.40. The energy ratio is highest in bream, intermediate in white bream and lowest in roach. 相似文献
63.
The response of a bumblebee goby,Brachygobius sabanus,to chemical stimuli from injured conspecifics 总被引:1,自引:0,他引:1
Synopsis
Brachygobius sabanus move less often and spend less time swimming when they detect chemicals released from injured conspecifics. This resembles the alarm response found in ostariophysan fishes, darters, and at least one other gobiid. Chemicals from injured Poecilia reticulata do not induce an alarm response in B. sabanus. 相似文献
64.
Rapid and simple isolation of pure photosystem II core and reaction center particles from spinach 总被引:2,自引:2,他引:0
Peter J. van Leeuwen Maaike C. Nieveen Erik Jan van de Meent Jan P. Dekker Hans J. van Gorkom 《Photosynthesis research》1991,28(3):149-153
Pure and active oxygen-evolving PS II core particles containing 35 Chl per reaction center were isolated with 75% yield from spinach PS II membrane fragments by incubation with n-dodecyl--D-maltoside and a rapid one step anion-exchange separation. By Triton X-100 treatment on the column these particles could be converted with 55% yield to pure and active PS II reaction center particles, which contained 6 Chl per reaction center.Abbreviations Bis-Tris
bis[2-hydroxyethyl]imino-tris[hydroxymethyl]methane
- Chl
chlorophyll
- CP29
Chl a/b protein of 29 kDa
- Cyt b
559
cytochrome b
559
- DCBQ
2,5-dichloro-p-benzo-quinone
- LHC II
light-harvesting complex II, predominant Chl a/b protein
- MES
2-[N-Morpholino]ethanesulfonic acid
- Pheo
pheophytin
- PS H
photosystem II
- QA
bound plastoquinone, serving as the secondary electron acceptor in PS II (after Pheo)
- SDS
sodiumdodecylsulfate 相似文献
65.
Jan M. Anderson 《Photosynthesis research》1991,30(1):1-5
Obituary
Robert (Robin) Hill (1899–1991) 相似文献66.
Summary At the end of a 4-year period of gas exchange measurements in a natural stand in the Lower Bavarian Forest, needles of an adult spruce [Picea abies (L.) Karst.] were harvested from two chambers, one with pure air and the other with ambient air. The needles were examined as to their histological properties in the stomatal apparatus and in the bundle sheath. In needles from the polluted air UV absorbance at 280 nm was decreased in the walls of the stomatal apparatus. Simultaneously, the deposition of compounds with an absorption maximum at 310 nm increased within the encrusted plate-like thickenings of the subsidiary cells. The contents of the lumina of hypodermal cells and of the bundle sheath exhibited a greater degree of autofluorescence in ambient-air material than in pure-air leaf organs. Differences between needles exposed to pure and polluted air are gradual. The damaged condition is rare in pure air, common in polluted air. The needles from outside the chambers occupied an intermediate position between pure-air and ambient-air needles. This fact is traced to an unnaturally high pollutant load in the liquid phase of the needle surfaces within the ambient-air chamber because in order to compensate pollutant losses within the system, SO2 and O3 were added even during periods of irrigation. The reduction of absorption capacity at 280 nm in the walls of the stomatal apparatus is attributed to destruction of lignin due to the high reactivity of the pollutants in the liquid phase on the damp needle surface. The importance of delignification with regard to hydroregulation is discussed. 相似文献
67.
J. Bernhards B. Weitzel M. Werner M. Rimpler A. Georgii 《Histochemistry and cell biology》1992,98(3):145-154
Summary A new procedure of embedding in methyl methacrylate (MMA) is introduced, which enables immunostaining by preservation of cellular epitopes. This could be achieved by reduction of polymerisation temperature from ca. 60° C to 22° C within the core of tissue blocks. Reduction of the polymerisation temperature is due to destabilisation of acrylate monomer, reduction of catalyst, exclusion of molecular oxygen, chemical initiation and reduction of environmental temperature. This results in good preservation of antigens and enzymes in the haematopoietic and lymphatic tissue of bone marrow as well as lymphoid, epithelial and mesenchymal markers in other tissues, comparable to paraffin embedding. Results are demonstrated by application of monoclonal and polyclonal antibodies and by demonstration of enzyme activity conventionally used in haematology. 相似文献
68.
The AXB and BXA set of recombinant inbred mouse strains 总被引:1,自引:1,他引:0
Jan D. Marshall Jian-Long Mu Yin-Chai Cheah Muriel N. Nesbitt Wayne N. Frankel Beverly Paigen 《Mammalian genome》1992,3(12):669-680
The recombinant inbred (RI) set of strains, AXB and BXA, derived from C57BL/6J and A/J, originally constructed and maintained at the University of California/San Diego, have been imported into The Jackson Laboratory and are now in the 29th to 59th generation of brother-sister matings. Genetic quality control testing with 45 proviral and 11 biochemical markers previously typed in this RI set indicated that five strains had been genetically contaminated sometime in the past, so these strains have been discarded. The correct and complete strain distribution patterns for 56 genetic markers are reported for the remaining RI strain set, which consists of 31 living strains and 8 extinct strains for which DNA is available. Two additional strains, AXB 12 and BXA 17, are living and may be added to the set pending further tests of genetic purity. The progenitors of this RI set differ in susceptibility to 27 infectious diseases as well as atherosclerosis, obesity, diabetes, cancer, cleft palate, and hydrocephalus. Thus, the AXB and BXA set of RI strains will be useful in the genetic analysis of several complex diseases. 相似文献
69.
Molecular analysis of the avirulence gene avr9 of the fungal tomato pathogen Cladosporium fulvum fully supports the gene-for-gene hypothesis 总被引:12,自引:0,他引:12
Guido F.J.M. Van den Ackerveken Jan A.L. Van Kan Pierre J.G.M. De Wit 《The Plant journal : for cell and molecular biology》1992,2(3):359-366
The interaction between the fungal pathogen Cladosporium fulvum and tomato is supposed to have a gene-for-gene basis. Races of C. fulvum which have 'overcome' the resistance gene Cf9 of tomato, lack the avirulence gene avr9 which encodes a race-specific peptide elicitor. Races avirulent on tomato genotypes carrying the resistance gene Cf9 produce the race-specific peptide elicitor, which induces the hypersensitive response (HR) on those genotypes. The causal relationship between the presence of a functional avr9 gene and avirulence on tomato genotype Cf9 was demonstrated by cloning of the avr9 gene and subsequent transformation of C. fulvum. A race virulent on tomato genotype Cf9 was shown to become avirulent by transformation with the cloned avr9 gene. These results clearly demonstrate that the avr9 gene is responsible for cultivar specificity on tomato genotype Cf9 and fully support the gene-for-gene hypothesis. The avr9 gene is the first fungal avirulence gene to be cloned. 相似文献
70.
Jan A. Veenstra 《Peptides》1991,12(6):1285-1289
An ELISA for corazonin, a cardioactive neuropeptide from the American cockroach, Periplaneta americana, was developed. It was used to isolate corazonin from the cockroach Nauphoeta cinerea, the locust Schistocerca americana, and the hawkmoth Manduca sexta. The peptides from Nauphoeta and Manduca had the same retention times as Periplaneta corazonin, and their amino acid compositions also suggested that these peptides are identical with corazonin. The corazonin-immunoreactive peptide from Schistocerca eluted slightly earlier on HPLC than corazonin, and its structure was determined to be [His7]corazonin, or pGlu-Thr-Phe-Gln-Tyr-Ser-His-Gly-Trp-Thr-Asn-amide. These results indicate that corazonin is generally present in insects and that its structure has been well conserved. 相似文献