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991.
Recovery of Waterborne Cryptosporidium parvum Oocysts by Freshwater Benthic Clams (Corbicula fluminea) 下载免费PDF全文
Thaddeus K. Graczyk Ronald Fayer Michael R. Cranfield David Bruce Conn 《Applied microbiology》1998,64(2):427-430
Asian freshwater clams, Corbicula fluminea, exposed for 24 h to 38 liters of water contaminated with infectious Cryptosporidium parvum oocysts (1.00 × 106 oocysts/liter; approximately 1.9 × 105 oocysts/clam) were examined (hemolymph, gills, gastrointestinal [GI] tract, and feces) on days 1, 2, 3, 7, and 14 postexposure (PE). No oocysts were detected in the water 24 h after the contamination event. The percentage of oocyst-containing clams varied from 20 to 100%, depending on the type of tissue examined and the technique used—acid-fast stain (AFS) or immunofluorescent antibody (IFA). The oocysts were found in clam tissues and feces on days 1 through 14 PE; the oocysts extracted from the tissues on day 7 PE were infectious for neonatal BALB/c mice. Overall, the highest number of positive samples was obtained when gills and GI tracts were processed with IFA (prevalence, 97.5%). A comparison of the relative oocyst numbers indicated that overall, 58.3% of the oocysts were found in clam tissues and 41.7% were found in feces when IFA was used; when AFS was used, the values were 51.9 and 48.1%, respectively. Clam-released oocysts were always surrounded by feces; no free oocysts or oocysts disassociated from fecal matter were observed. The results indicate that these benthic freshwater clams are capable of recovery and sedimentation of waterborne C. parvum oocysts. To optimize the detection of C. parvum oocysts in C. fluminea tissue, it is recommended that gill and GI tract samples be screened with IFA (such as that in the commercially available MERIFLUOR test kit). 相似文献
992.
Distribution and Developmental Regulation of Metabotropic Glutamate Receptor 7a in Rat Brain 总被引:2,自引:0,他引:2
Stefania Risso Bradley Howard D. Rees Hong Yi Allan I. Levey P. Jeffrey Conn 《Journal of neurochemistry》1998,71(2):636-645
Abstract: To determine the regional and cellular distribution of the metabotropic glutamate receptor mGluR7a, we used rabbit anti-peptide polyclonal-targeted antibodies against the C-terminal domain of mGluR7a. Here we report that immunocytochemistry at the light-microscopic level revealed that mGluR7a is widely distributed throughout the adult rat brain, with a high level of expression in sensory areas, such as piriform cortex, superior colliculus, and dorsal cochlear nucleus. In most brain structures, mGluR7a immunoreactivity is characterized by staining of puncta and fibers. However, in some regions, including the locus ceruleus, cerebellum, and thalamic nuclei, both cell bodies and fibers are immunopositive. The changes in levels of mGluR7a during development were investigated with immunoblotting and immunocytochemical analysis. Immunoblot analysis revealed that the levels of mGluR7a are differentially regulated across brain regions during postnatal development. In cortical regions (hippocampus, neocortex, and olfactory cortex), mGluR7a levels were highest at postnatal day 7 (P7) and P14, then declined in older rats. In contrast, mGluR7a levels were highest at P7 in pons/medulla and cerebellum and decreased markedly between P7 and P14. In these regions, mGluR7a immunoreactivity was at similar low levels at P14 and P21 and in adults. Immunocytochemical analysis revealed that staining for mGluR7a was exceptionally high in fiber tracts in P7 animals relative to adults. Furthermore, the pattern of mGluR7a immunoreactivity in certain brain structures, including cerebellum, piriform cortex, and hippocampus, was significantly different in P7 and adult animals. In summary, these data suggest that mGluR7a is widely distributed throughout the rat brain and that this receptor undergoes a dynamic, regionally specific regulation during postnatal development. 相似文献
993.
Female mice of pregnant random-bred, or unmated BALB/c groups were exposed per os to Mesocestoides corti tetrathyridia and necropsied at various intervals postexposure. The right posterior subcutaneous fat pad with two mammary glands was removed from each mouse, stained, mounted whole and examined microscopically for localization of worms. The left fat pad/gland set was processed, sectioned and stained using standard histological techniques. In pregnant mice, tetrathyridia were localized primarily in the fat pad's posteroventral lobe. Unmated mice had few worms in the mammary glands or associated fat pads. The difference in infection levels between the two host groups may result from mouse strain difference or the pregnant condition of one group. 相似文献
994.
The hydroxynitrile lyase (HNL, EC 4.2.1.-) of Hevea brasiliensis (Muell.-Arg.) catalyzes the dissociation of acetone cyanohydrin and mandelonitrile, but shows higher activity towards the natural substrate acetone cyanohydrin. The ratio between the activities of linamarase (β-glycosidase, EC 3.2.1.21) to HNL was screened for more than 30 Hevea plants. In mixed-enzyme incubations various ratios of HNL to β-glucosidase were analyzed for the rapidity of HCN liberation. Addition of HNL increased the rate of HCN liberation up to 20-fold, thus demonstrating the significance of the HNL for rapid cyanogenesis. Its physiological importance is shown by the fact that only plants possessing high HNL activity are able to liberate HCN efficiently. Cyanogenic plants have been described as being weakly or strongly cyanogenic depending on the total amount of HCN which is potentially liberated. The data presented in this paper suggest that cyanogenic plants should also be differentiated as fast or slow cyanogenic according to the observed velocity of HCN liberation. Thus, for evaluating the repellent action of cyanogenic plants not only the final level of the HCN liberated is important but rather the rate with which this level is reached. 相似文献
995.
Infertile couples with Robertsonian translocations: preimplantation genetic analysis of embryos reveals chaotic cleavage divisions 总被引:22,自引:0,他引:22
C. M. Conn Joyce C. Harper Robert M. L. Winston Joy D. A. Delhanty 《Human genetics》1998,102(1):117-123
Preimplantation genetic diagnosis (PGD) may provide a feasible option for some Robertsonian translocation carriers who experience
severe difficulty in achieving a normal pregnancy. We report on five PGD cycles for two such couples, 45,XY,der(13;14)(q10:q10)
and 45,XX,der(13;21)(q10;q10), carried out by biopsy of two cells from day 3 post-insemination embryos generated by in vitro
fertilisation. Locus-specific YAC probes for chromosomes 13, 14 and 21 were used to detect the chromosomes involved in the
translocation using multicolour FISH. Three embryos transfers were carried out (two single embryo transfers and one double
transfer) but no clinical pregnancies were established. In two cycles no embryos were transferred as all those biopsied were
chromosomally abnormal. Combined results from both couples show 13% (6/45) of embryos analysed were normal for the translocation
chromosomes and 87% (39/45) were chromosomally abnormal; these were categorised as 36% aneuploid or aneuploid mosaic and 51%
chaotic where the chromosome constitution varied randomly from cell to cell. This suggests two factors may be acting to reduce
fertility in these couples; the aneuploid segregation of the parental Robertsonian translocation and also a post-zygotic factor
leading to uncontrolled chromosome distribution in early cleavage stages in an exceptionally high proportion of embryos.
Received: 24 September 1997 / Accepted: 22 October 1997 相似文献
996.
Resistance of nicotiana benthamiana to phytophthora infestans is mediated by the recognition of the elicitor protein INF1 总被引:11,自引:0,他引:11 下载免费PDF全文
Phytophthora infestans, the agent of potato and tomato late blight disease, produces a 10-kD extracellular protein, INF1 elicitin. INF1 induces a hypersensitive response in a restricted number of plants, particularly those of the genus Nicotiana. In virulence assays with different P. infestans isolates, five Nicotiana species displayed resistance responses. In all of the interactions, after inoculation with P. infestans zoospores, penetration of an epidermal cell was observed, followed by localized necrosis typical of a hypersensitive response. To determine whether INF1 functions as an avirulence factor in these interactions, we adopted a gene-silencing strategy to inhibit INF1 production. Several transformants deficient in inf1 mRNA and INF1 protein were obtained. These strains remained pathogenic on host plants. However, in contrast to the wild-type and control transformant strains, INF1-deficient strains induced disease lesions when inoculated on N. benthamiana. These results demonstrate that the elicitin INF1 functions as an avirulence factor in the interaction between N. benthamiana and P. infestans. 相似文献
997.
The involvement of the microtubule (MT) and actin microfilament (MF) cytoskeletons in establishing nuclear positions during zoosporogenesis in Allomyces macrogynus was assessed using selective cytoskeletal disrupting treatments and documented with light microscopy. These experiments were coupled with low-speed centrifugation studies to determine the degree to which cytoskeletal elements anchor nuclear position. At the onset of zoospore formation, nuclei were positioned only in cortical cytoplasmic regions of the zoosporangia (ZS). Immunofluorescence microscopy revealed that MTs primarily emanated from centrosomal regions into the surrounding cytoplasm at this stage. During delimitation of the cytoplasm into individual uninucleate zoospores, nuclei migrated from cortical regions to become distributed throughout the cytoplasm. Coincident with nuclear migrations, MTs were primarily organized at and emanated from nuclear surfaces, forming extensive perinuclear arrays. Nuclear migrations were suppressed in ZS induced to sporulate in the presence of cytochalasin D, an actin MF inhibiting compound. Disruption of MTs with nocodazole did not block nuclear migrations, although resultant nuclear spacing was irregular. Centrifugation treatments of control and drug-treated ZS demonstrated that nuclear positions were stabilized by perinuclear MT arrays. The results indicate that nuclear motility in ZS of A. macrogynus is the result of an actin-based system while perinuclear MTs arrays function to establish and fix nuclear position during zoospore formation. Copyright 1998 Academic Press. 相似文献
998.
Schmid metaphyseal chondrodysplasia results from mutations within the COOH-terminal globular domain (NC1) of type X collagen, a short chain collagen expressed in the hypertrophic region of the growth plate cartilage. Previous in vitro studies have proposed that mutations prevent the association of the NC1 domain of constituent chains of the trimer based upon a lack of formation of a trimeric structure that is resistant to dissociation with sodium dodecyl sulfate. To examine the effect of mutations on folding and assembly within a cellular context, bovine type X cDNAs containing analogous disease causing mutations Y598D, N617K, W651R, and wild-type were expressed in semi-permeabilized cells. We assessed trimerization of the mutant chains by their ability to form a collagen triple helix. Using this approach, we demonstrate that although there is an apparent lower efficiency of association of the mutant NC1 domains, they can drive the formation of correctly aligned triple helices with the same thermal stability as the wild-type collagen. When epitope-tagged mutant and wild-type collagen were co-expressed, heterotrimers could be detected by sequential immunoprecipitation. Both wild-type and mutant type X chains were found in association with the molecular chaperones protein disulfide isomerase and Hsp 47. The implications of these findings on the likely mechanism of Schmid metaphyseal chondrodysplasia will be discussed. 相似文献
999.
1000.
Cozzi J Conn CM Harper J Winston RM Rindl M Farndon PA Delhanty JD 《Human genetics》1999,104(1):23-28
A chromosomally normal 37-year-old woman was referred for preimplantation genetic diagnosis after having several conceptuses
with trisomy 21. Segregation of chromosome 21 was assessed in unfertilised meiosis II oocytes and preimplantation embryos
from PGD cycles using fluorescent in situ hybridisation (FISH). Of 7 preimplantation embryos, 5 were chromosomally abnormal
with 4 having trisomy 21 and one being tetraploid. Of 4 oocytes, 3 had an abnormal chromosomal constitution with either an
extra chromosome 21 or an extra chromatid 21. In one oocyte an extra chromatid 21 was detected in both the metaphase II complement
and the first polar body providing the first direct evidence of a maternal trisomic germ cell line. Moreover, this result
shows that the extra chromosome 21 can precociously divide into its two chromatids at the first meiotic division.
Received: 9 September 1998 / Accepted: 26 November 1998 相似文献