全文获取类型
收费全文 | 1083篇 |
免费 | 69篇 |
国内免费 | 2篇 |
出版年
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 28篇 |
2014年 | 45篇 |
2013年 | 40篇 |
2012年 | 64篇 |
2011年 | 58篇 |
2010年 | 37篇 |
2009年 | 44篇 |
2008年 | 70篇 |
2007年 | 54篇 |
2006年 | 48篇 |
2005年 | 49篇 |
2004年 | 56篇 |
2003年 | 57篇 |
2002年 | 38篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 25篇 |
1998年 | 21篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 20篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1973年 | 8篇 |
1968年 | 5篇 |
1967年 | 6篇 |
1937年 | 4篇 |
排序方式: 共有1154条查询结果,搜索用时 15 毫秒
951.
Cytogenetic and molecular characterization of inverted duplicated chromosomes 15 from 11 patients. 总被引:9,自引:2,他引:7
下载免费PDF全文
![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S. D. Cheng N. B. Spinner E. H. Zackai J. H. Knoll 《American journal of human genetics》1994,55(4):753-759
We have studied the inverted duplicated chromosomes 15 (inv dup(15)) from 11 individuals--7 with severe mental retardation and seizures, 3 with a normal phenotype, and 1 with Prader-Willi syndrome (PWS). Through a combination of FISH and quantitative DNA analyses, three different molecular sizes of inv dup(15) were identified. The smallest inv dup(15) was positive only for the centromeric locus D15Z1 (type 1); the next size was positive for D15Z1 and D15S18 (type 2); and the largest inv dup(15) was positive for two additional copies of loci extending from D15Z1 and D15S18 through D15S12 (type 3). Type 1 or type 2 was observed in the three normal individuals and the PWS patient. Type 3 was observed in all seven individuals with mental retardation and seizures but without PWS or Angelman Syndrome (AS). The PWS patient, in addition to being mosaic for a small inv dup(15), demonstrated at D15S63 a methylation pattern consistent with maternal uniparental inheritance of the normal chromosomes 15. The results from this study show (a) two additional copies of proximal 15q loci, D15S9 through D15S12, in mentally retarded patients with an inv dup(15) but without AS or PWS and (b) no additional copies of these loci in patients with a normal phenotype or with PWS. 相似文献
952.
The innervation of the bovine tubouterine junction was studied in sexually mature heifers using antisera against various neuronal markers and a modified acetylcholinesterase method. The vast majority of the nerve fibres in the bovine tubouterine junction belongs to the sympathetic nervous system; peptidergic and cholinergic fibers are restricted to characteristic locations. The endosalpinx in the adovarian portion of the terminal tubal segment is poorly innervated. The mucosa of the aduterine portion and of the tubouterine transitinal region proper receives a strikingly dense innervation, which is observed mainly in combination with a strong vascularisation of specialised mucosal structures. In the endometrium, perivascular nerves accompany the ascending spiral arteries but sporadic contacts between nerve fibres and uterine glands are also observed. From the muscular coat the inner longitudinal layer of the terminal tubal segment is more richly supplied by nerve fibres than the intermediate circular and outer longitudinal layers of the tubouterine junction. No changes in the innervation pattern were seen during the different stages of the sexual cycle. 相似文献
953.
Jan Kuever Juergen Kulmer Sigrid Jannsen Ulrich Fischer Karl-Heinz Blotevogel 《Archives of microbiology》1993,159(3):282-288
A new mesophilic sulfate-reducing bacterium, strain Groll, was isolated from a benzoate enrichment culture inoculated with black mud from a freshwater ditch. The isolate was a spore-forming, rod-shaped, motile, gram-positive bacterium. This isolate was able of complete oxidation of several aromatic compounds including phenol, catechol, benzoate, p-and m-cresol, benzyl alcohol and vanillate. With hydrogen and carbon dioxide, formate or O-methylated aromatic compounds, autotrophic growth during sulfate reduction or homoacetogenesis was demonstrated. Lactate was not used as a substrate. SO
inf4
sup2-
, SO
inf3
sup2-
, and S2O
inf3
sup2-
were utilized as electron acceptors. Although strain Groll originated from a freshwater habitat, salt concentrations of up to 30 g·l-1 were tolerated. The optimum temperature for growth was 35–37°C. The G+C content of DNA was 42.1 mol%. This isolate is described as a new species of the genus Desulfotomaculum. 相似文献
954.
A new sulfate-reducer strain SAX was isolated from an anaerobic marine sediment [Saxild, Denmark]. The isolate was a gram-negative, motile and non-spore-forming rod which sometimes appeared as a curved rod. Strain SAX differed from all described Desulfovibrio-, Desulfobotulus- and Desulfoarculus-species by the ability to degrade aromatic compounds such as benzoate, 4-hydroxybenzoate and phenol completely to CO2. Electron donors used included lactate, pyruvate, malate, fumarate, crotonate and butyrate, while pyruvate was fermented in the absence of an external electron acceptor. Sulfate, thiosulfate or sulfite served as electron acceptors with benzoate as the donor, while nitrate and nitrite did not. The sulfate-reducing bacterium required vitamins and NaCl-concentrations of about 20 g/l. The optimum temperature for growth of strain SAX was 30°C and the optimum pH value was 7.3. The DNA base composition was 62.4 mol% G+C. The strain possessed cytochrome c3, but no desulfoviridin. On the basis of these characteristics and because strain SAX could not be ascribed to any of the existing species therefore assignment as a new species to the genus Desulfoarculus was suggested.Abbreviations G+C
Guanine plus Cytosine 相似文献
955.
A rapid and sensitive ion chromatographic technique for the determination of sulfate and sulfate reduction rates in freshwater lake sediments 总被引:6,自引:0,他引:6
Abstract Newly developed low capacity columns were used in suppressed ion chromatography for rapid and highly reproducible determination of SO4 2− in porewater samples from freshwater sediments without preconcentration of samples. With a 50 μl injection the detection limit for SO4 2− was ca. 50 pmol (= 1 μ M) with a precision of 1–3% at the 10–200 μM level and <1% at concentrations above 200 μM. SO4 2− could be measured in 4–5 min with the routinely used eluent (3.0 mM NaHCO3 /0.8 mM Na2 CO3 ). When the strength of the eluent was increased to 3.0 mM NaHCO3 /2.0 mM Na2 CO3 , sulfate analysis was possible in less than 3 min, provided that samples were nitrate-free. Under these conditions S2 O3 2− could also be sensitively determined in about 6 min. Examples of application of the method are given for measurements of sulfate reduction rates in freshwater sediment samples from Lake Constance. 相似文献
956.
Among the variety of parameters affecting immuno-gold labelling efficiency, mainly the effects of different preparative protocols were tested. Preservation of ultrastructure and of antigenicity are the salient features of this study. We have labelled insoluble components of the secretory matrix of Paramecium trichocysts with specific antisera, using 10 nm colloidal gold particles. The highest labelling efficiency was obtained with fast freezing (cryofixation, either by sandwich or spray-freezing), freeze-substitution in methanol (without added fixatives) and hydrophilic Lowicryls, particularly when applied at low temperatures (K11M at 193 K). The presence of different chemical fixatives always reduced the labelling density and some recommendations from the literature do not appear advisable. Methods commencing with fixation at greater than or equal to 0 degree C, such as "progressive lowering of temperature" (PLT) or preparation of cryostat sections, i.e. with chemical pretreatments, always resulted in lower labelling density. Our data appear, therefore, relevant for optimal immuno-gold labelling of insoluble antigens and emphasize the potential of cryofixation as a primary preparation step. In addition, ultrastructural preservation was also superior after cryofixation. 相似文献
957.
Summary Among the variety of parameters affecting immuno-gold labelling efficiency, mainly the effects of different preparative protocols were tested. Preservation of ultrastructure and of antigenicity are the salient features of this study. We have labelled insoluble components of the secretory matrix of Paramecium trichocysts with specific antisera, using 10 nm colloidal gold particles. The highest labelling efficiency was obtained with fast freezing (cryofixation, either by sandwich or spray-freezing), freeze-substitution in methanol (without added fixatives) and hydrophilic Lowicryls, particularly when applied at low temperatures (K11M at 193 K). The presence of different chemical fixatives always reduced the labelling density and some recommendations from the literature do not appear advisable. Methods commencing with fixation at 0° C, such as progressive lowering of temperature (PLT) or preparation of cryostat sections, i.e. with chemical pretreatments, always resulted in lower labelling density. Our data appear, therefore, relevant for optimal immuno-gold labelling of insoluble antigens and emphasize the potential of cryofixation as a primary preparation step. In addition, ultrastructural preservation was also superior after cryofixation.Abbreviations AB
antibodies
- AED
aminoethyldextran
- Au10
colloidal gold (10 nm diameter)
- BSA
bovine serum albumin
- EtOH
ethanol
- FA
formaldehyde
- GA
glutaraldehyde
- LN2
liquid nitrogen
- MeOH
methanol
- pA
protein A
- Pipes
piperazine-N,N-bis(2-ethanesulphonic acid)
- PLT
progressive lowering of temperature
- PVP
polyvinylpyrrolidone
- UA
uranylacetate 相似文献
958.
Birgit Theisinger Cornelius Welter Karl-Heinz Grzeschik Nikolaus Blin 《Human genetics》1992,89(6):681-682
Summary A human cDNA corresponding to the porcine pancreatic spasmolytic protein (PSP) was isolated, and the recombinant clone was originally termed hSP for human spasmolytic protein. Later, the term SML1 for spasmolysin was suggested for the human gene. This protein shows a remarkable sequence homology to pS2, a protein coded by an estrogen-induced gene isolated from the breast carcinoma cell line MCF-7. Although, at the DNA level, the gene sequences pS2 and hSP/SML1 display insufficient homology for cross-hybridization, their expression in tumor cells occurs with remarkable coordination. The human pS2 gene sequence has been assigned to chromosome 21, and we have therefore attempted to map the hSP/SMLl gene by using cDNA and Southern blotting of genomic DNAs from a panel of human-rodent somatic cell hybrids carrying different complements of human chromosomes. Interestingly, the hSP/SMLl gene is also localized on chromosome 21. 相似文献
959.
The photoaffinity analog of ATP, 8-azidoATP, labels T7 RNA polymerase. Photoincorporation exhibits saturation behavior and is protected against by the substrate ATP. 8-AzidoATP is a competitive inhibitor of ATP incorporation with Ki approximately 40 microM. The photolabeled T7 RNA polymerase, following cyanogen bromide digestion, was analyzed by phenylboronate agarose column chromatography followed by reverse-phase high pressure liquid chromatography. Sequencing of the peptides labeled with radioactive photoprobe allowed the identification of three peptides, P314-M362 (I), L550-M666 (II), and F751-M861 (III). These peptides are in the proximity of the photoprobe 8-azidoATP and, therefore, expected to contain functionally significant residues and define an active site domain. These peptides (I and II) contain residues previously implicated in T7 RNA polymerase activity or show homology to active site regions of the Klenow fragment of DNA polymerase I (II and III). 相似文献
960.
We demonstrate that surface-plasmon microscopy allows one to monitor the specific binding of streptavidin to biotinylated lipid molecules selectively enriched in one of the two coexisting phase domains of a phospholipid monolayer transferred in its phase transition region from the water-air interface to a solid support. 相似文献