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201.
The analysis of 68 published sets of dose-incidence data for marrow failure in different species, using a double-log mortality function, indicates: (a) There is more heterogeneity, i.e. greater sums-of-squares per degree of freedom, within the data sets for mouse than for larger species (monkey, dog, sheep, goat, pig). (b) For mice the curves for acute doses are characterized by a D0 of about 100 cGy for tissue-rescuing units (or target cells), which are depleted at most to about 3 x 10(-4) at LD50. (c) Larger species are much less tolerant to target-cell depletion, the corresponding level being consistently in the range of 10(-2)-10(-3) at LD50. Also, the D0 is often lower (approximately 55 cGy), which is compatible in the dog with such a value for hemopoietic progenitor cells. (d) With larger species there is an unexpected reduction in heterogeneity when the dose rate is lower, which gives a D0 lower than expected and a higher extrapolate. It is concluded that the position and slope of the dose-incidence curves are compatible with interpretations based primarily on target-cell number and survival characteristics, modified by additional heterogeneity factors. 相似文献
202.
Spatiotemporal patterns of expression of the cell-surface arabinogalactan-protein epitope defined by monoclonal antibody JIM4 (J.P. Knox et al., 1989, Development 106, 47–56) have been characterized by indirect immunofluorescence during the process of somatic embryogenesis in Daucus carota L. The JIM 4 epitope (J4e) occurred on cells established in culture from hypocotyl explants which appeared to derive, at least in part, from the epidermal cells of the hypocotyl. Cultures maintained in the presence of 2,4-dichlorophenoxyacetic acid developed proembryogenic masses of which only infrequent cells at the surface expressed J4e. Sub-culture at a low cell density and withdrawl of the synthetic auxin resulted in an increase in J4e expression in most surface cells and most abundantly in surface layers of cells at the future shoot end of developing embryos. The transition to heart-shaped embryos occurred concurrently with the expression of J4e by groups of cells beneath the developing cotyledons, at the junction of the future root and shoot. At this stage, J4e was also expressed by a single well-defined layer of cells at the surface of the embryos. Advancement to the mature torpedo stage was accompanied by the expression of the epitope on cells forming two regions of the future stele and of cells associated with the cotyledonary provascular tissue characteristic of the carrot seedling. At this stage there was substantially less expression of the marker antigen by epidermal cells, although infrequent expression by isolated cells of the epidermis was maintained. The correlation of J4e expression with the development and distinction of plant tissue patterns during somatic embryogenesis indicates a role for plasma-membrane arabinogalactan proteins in these processes.Abbreviations AGP
arabinogalactan protein
- 2,4-D
2,4-di-chlorophenoxyacetic acid
- J4e
JIM 4 epitope
- PEM
proembryogenic mass
We thank Andrew Davis for photographic assistance and Roger Pennell for useful discussions. 相似文献
203.
S F Sharif H Francis D H Keisler R M Roberts 《Journal of reproduction and fertility》1989,85(2):471-476
We studied the biosynthesis of two proteins, p70 (Mr 70,000; pI 4.0) and p15 (Mr 15,000; pI 5.7), by endometrial tissues from ewes between Days 12 and 24 of pregnancy and between Days 12 and 16 of the oestrous cycle to determine whether production of the two was correlated with the period of biosynthesis of ovine trophoblast protein-1 (oTP-1) by the conceptus. We also compared the protein synthetic activities of endometrium from gravid and non-gravid horns of pregnant ewes at Days 14, 16 and 18 in which the conceptus had been confined to one uterine horn. Proteins p70 and p15 were produced maximally between Days 14 and 20 of pregnancy, but synthesis by endometrial cultures from cyclic ewes was low or absent. Furthermore, synthesis of Protein p70 in particular was much greater by the gravid than non-gravid horn of unilaterally pregnant ewes. We conclude that synthesis of Proteins p70 and p15 by the uterus of sheep coincides with the time of oTP-1 production by the conceptus. 相似文献
204.
205.
S H Oh H Y Steiner D K Dougall D M Roberts 《Archives of biochemistry and biophysics》1992,297(1):28-34
Carrot cell cultures were used to study the dynamics of calmodulin protein levels, calmodulin methylation, and calmodulin-binding proteins during plant growth and development. Comparisons of proliferating and nonproliferating wild carrot cells show that, while calmodulin protein levels does not vary significantly, substantial variation in post-translational methylation of calmodulin on lysine-115 is observed. Calmodulin methylation is low during the lag and early exponential stages, but increases substantially as exponential growth proceeds and becomes maximal in the postexponential phase. Unmethylated calmodulin quickly reappears within 12 h of reinoculation of cells into fresh media, suggesting that the process is regulated according to the cell growth state. Calmodulin and calmodulin-binding proteins were also analyzed during the formation and germination of domestic carrot embryos in culture. Neither calmodulin methylation nor calmodulin protein levels varied significantly during somatic embryogenesis. However, upon germination of embryos, the level of calmodulin protein doubled. By calmodulin overlay analysis, we have detected a major 54,000 M(r) calmodulin-binding protein that also increased during embryo germination. This protein was purified from carrot embryo extracts by calmodulin-Sepharose chromatography. Overall, the data suggest that calmodulin methylation is regulated depending upon the state of cell growth and that calmodulin and its target proteins are modulated during early plant development. 相似文献
206.
J Langlais J G Chafouleas R Ingraham N Vigneault K D Roberts 《Biochemical and biophysical research communications》1992,182(1):208-214
In view of its proposed key role in the acrosome reaction, phospholipase A2 has been isolated and purified from human spermatozoa. Following SDS-PAGE, a single major band was obtained with an estimated molecular mass of 16.7 kDa. Sequence analysis of the N-terminal portion of the molecule revealed the identity of the first 19 amino acids to be YNYQFGLMIVITKGHFAMV. From this partial analysis it is evident that the phospholipase A2 of human spermatozoa represents a new sequence. Of interest is the location of glutamine-4, phenylalanine-5, methionine-8 and isoleucine-9; this sequence appears to be highly conserved throughout evolution. 相似文献
207.
L Chandonnet K D Roberts A Chapdelaine P Manjunath 《Molecular reproduction and development》1990,26(4):313-318
A group of four similar proteins, BSP-A1, BSP-A2, BSP-A3, and BSP-30-kDa, represent the major acidic proteins found in bovine seminal plasma (BSP). These proteins are secretory products of the seminal vesicles; they bind to spermatozoa upon ejaculation and could represent decapacitation factors. It has been shown that the glycosaminoglycans present in the female reproductive tract are involved in the capacitation of spermatozoa. Therefore, it was of interest to investigate whether BSP-A1, -A2, -A3, and -30-kDa proteins of bovine seminal fluid interact with heparin. Chromatography of alcohol precipitates of bovine seminal fluid on a heparin-Sepharose column resolved these proteins into three peaks. Peaks 1 and 2 (retarded proteins) were eluted upon extensive washing of the column with 0.05 M phosphate buffer, pH 7.4 (equilibrating buffer), and accounted for approximately 25% of the applied proteins. Proteins in peak 3 represented adsorbed proteins and were eluted with phosphate buffer containing 1 M NaCl. Proteins in each peak were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. Peak 1 contained proteins with molecular weights ranging from 8 to 350 kDa, peak 2 contained a single protein with a molecular weight of 14 kDa, and peak 3 contained proteins with molecular weights of 15.5, 16, 25, and 30 kDa. The proteins in peak 3 were further resolved into unadsorbed (peak 4) and adsorbed (peak 5) proteins on a gelatin-Agarose column. Separation of the proteins of peak 3 and peak 5 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and reducing agents followed by transfer to nitrocellulose and probing with antibodies against the previously well-characterized BSP proteins indicated the presence of BSP-A1, BSP-A2, BSP-A3, and BSP-30-kDa proteins.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
208.
Protein synthesis and secretion in the human epididymis and immunoreactivity with sperm antibodies 总被引:1,自引:0,他引:1
P Ross F W Kan P Antaki N Vigneault A Chapdelaine K D Roberts 《Molecular reproduction and development》1990,26(1):12-23
The synthesis and secretion of proteins in the different regions of the human epididymis were studied in vitro. Epididymal tissues obtained from patients undergoing castration for prostatic carcinoma or from cadavers were incubated in the presence of [35S]methionine, and the resulting radiolabeled proteins were analysed on SDS-PAGE. The corpus region was found to be the most active segment in total protein synthesis. Significant qualitative and quantitative changes were observed in the pattern of proteins secreted from the different epididymal regions. To establish those epididymal proteins that interact with maturing sperm, the secreted products were immunoreacted with antibodies raised against a Triton X-100 extract of ejaculated human sperm heads. The antibodies react mainly with the head region of ejaculated spermatozoa as judged by indirect immunofluorescence. Protein A-gold labeling of freeze-fracture images showed gold particle distribution on the sperm plasma membrane. Western blot analysis of the secreted proteins revealed four bands (66, 37, 32, and 29 kDa) in the proximal regions and six additional bands (80, 76, 48, 27, 22, and 17 kDa) in the distal part of the epididymis. Immunoprecipitation of the secreted proteins with these antibodies revealed six radioactive bands of 170, 80, 76, 60, 48, and 37 kDa, which indicates that certain proteins of epididymal origin bind to the sperm plasma membrane. 相似文献
209.
Perturbation of nifT expression in Klebsiella pneumoniae has limited effect on nitrogen fixation. 总被引:1,自引:1,他引:0 下载免费PDF全文
In the nitrogenase system of Klebsiella pneumoniae, nifT is located between nifDK, the structural genes for dinitrogenase, and nifY, whose product is involved in nitrogenase maturation. It is, therefore, a reasonable hypothesis that the NifT protein might also have a role in the maturation of nitrogenase. However, the phenotypic characterization of nifT and nifT-overexpressing strains for effects on the regulation, maturation, and activity of nitrogenase identified no properties that were distinct from those of the wild type. We conclude that the K. pneumoniae NifT protein is not essential for nitrogen fixation under the conditions examined. 相似文献
210.
Mulholland B.J.; Taylor I.B.; Black C.R.; Roberts J.A. 《Journal of experimental botany》1996,47(4):551-556
The abscisic acid (ABA)-deficient mutant of barley, Az34, exhibiteda much reduced rate of leaf expansion at a bulk density of 1.6g cm3 as compared to the isogenic wild-type variety,Steptoe. Az34 had a consistently lower xylem sap ABA concentrationat 7 d and 14 d after emergence (DAE). The xylem sap data suggestthat ABA present at Steptoe concentrations may have a directrole in maintaining leaf expansion at the sub-critical bulkdensity (1.6 g cm3 To test this hypothesis, additionof synthetic ABA either to the rooting environment (100 nM)or directly to the xylem sap (5 pg µl1 to reproducethe xylem sap ABA concentrations found in Steptoe, increasedleaf expansion in Az34 to the wild-type level. Furthermore,feeding Steptoe xylem sap to Az34 produced similar effects.These experiments provide direct evidence of a positive rolefor ABA as a root-to-shoot signal which assists in maintainingleaf growth in plants experiencing subcritical levels of compactionstress. Key words: ABA-deficient mutant, leaf expansion, xylem sap, ABA 相似文献