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61.
A serotype-specific epitope of dengue virus 1 identified by phage displayed random peptide library 总被引:3,自引:0,他引:3
Zhi-Jian Yao Mandy C.C. Kao Kean-Chong Loh Maxey C.M. Chung 《FEMS microbiology letters》1995,127(1-2):93-98
Abstract From a panel of monoclonal antibodies of dengue viruses, a serotype-specific epitope of dengue virus 1 was screened from a random peptide library displayed on phage. The epitope was the determinant reactive with monoclonal antibody 15F3-1 that was specific to dengue 1. The screening was monitored by a dot blotting procedure, and after three rounds of screening a consensus motif, HRYSWK, was found. This sequence matches the sequence HKYSWK, corresponding to the amino acid residues 885–890 of polyprotein or residues 111–116 of the non-structural protein 1 of dengue virus serotype 1. The linear epitope was confirmed by testing the antigenicity of chemically synthesized 8-branched peptide. 相似文献
62.
Y. Yie Z. X. Wu S. Y. Wang S. Z. Zhao T. Q. Zhang G. Y. Yao P. Tien 《Transgenic research》1995,4(4):256-263
A procedure for the fast production of homozygotic transgenic plants was developed. Leaf discs of haploid tobacco plants from anther cultures were transformed with a chimaeric vector containing coat protein (CP) and satellite RNA (Sat-RNA) genes from cucumber mosaic virus (CMV). One-hundred-and-twelve Kanamycin-resistant transformed haploid plants were subjected to selection based on the expression of both CP and Sat-RNA. Eighty-nine transgenic plants expressing both genes were selected and tested for their resistance to CMV by inoculation with high concentration of CMV (200 g ml–1). Only five plants showed no symptoms of viral infection 30 days after inoculation. These plants were then diploidized by colchicine treatment. Three homozygous diploid lines with high levels of resistance to CMV were obtained after only one generation. The three transgenic lines were further tested under field conditions. The results showed that the progenies of these transgenic lines were homozygous and were highly resistant to CMV under natural field infection and manual inoculation conditions. 相似文献
63.
The effect of both prenatally and postnatally induced acute hypoxia on the blood volume was studied in 16 newborn lambs. Hypoxia was induced by 8% O2 inhalation for 10–20 minutes prenatally in 7 term pregnant ewes immediately before caesarean section delivery of the lambs (Group 1), and postnatally in nine 2–4 day old lambs born spontaneously (Group 11). The umbilical cords of Group 1 lambs were clamped early (E.C.) within 10 seconds after birth. Group 11 lambs had their cords severed within one minute of birth by the ewes. Blood volume (BV) was measured by the double label, radioiodinated human serum albumin-125 (RIHSA-125) plasma tag and radiochromium-51 (Cr51) red cell tag dilution technique. The red cell volume (RCV), which reflects the size of placental transfusion best, is significantly higher in Group 1 (42.1 ± 1.6 ml/kg) than in normal E.C. lambs (29.8 ± 2.0 ml/kg). The RCV in Group 1 was smaller than that in late clamped (L.C.) lambs, in whom an almost complete placental transfusion (RCV = 50.4 ± 2.3 ml/kg) had occurred; and close to those of spontaneously born lambs (S.B.) who received a partial placental transfusion (RCV = 36.7 ± 2.1 ml/kg). This finding in Group 1 suggests that with prenatal hypoxia, a partial placental transfusion had occurred in utero. In Group 11 lambs in whom hypoxia was postnatally induced, the BV, RCV, and plasma volume (109.7 ± 5.2, 44.1 ± 1.7 and 65.1 ± 4.2 ml/kg) were slightly, but not significantly, increased from control values of 101.6 ± 4.9, 40.8 ± 1.7 and 60.8 ± 4.3 mg/kg), respectively. It is suggested that postnatally induced hypoxia does not significantly increase the blood volume of newborn lambs due to the absence of placental reservoir of blood. Prenatally induced hypoxia appeared to bring about a higher blood volume than expected in E.C. lambs due to a transfer of placental blood to the fetus in utero. Blood volume redistribution in the feto-placental unit in utero is an unique adaptational response to prenatal hypoxia. 相似文献
64.
本文介绍了珠状交联琼脂糖及以此作为载体,经氯代环氧丙烷活化后与蛋白酶(胰蛋白酶或糜蛋白酶)结合,制成固定化蛋白酶亲和吸附剂,进而用以亲和层析牛肺提取液中的Kunitz抑制剂的方法。纯化出的抑制剂在SDS-聚丙烯酰胺凝胶电泳上呈现单一条带,与参照物Trasytol(商品Kunitz抑制剂)具有相对应的电泳迁移率,其分子量也相符。纯化产品每毫克蛋白的抑制活力相当于16 000胰蛋白酶BAEE单位。纯化效果为90倍,收率约85%。 相似文献
65.
66.
Acetylation of O-specific lipopolysaccharides from Shigella flexneri 3a and 2a occurs in Escherichia coli K-12 carrying cloned S. flexneri 3a and 2a rfb genes. 下载免费PDF全文
Most of the Shigella flexneri O-specific serotypes result from O-acetyl and/or glucosyl groups added to a common O-repeating unit of the lipopolysaccharide (LPS) molecule. The genes involved in acetylation and/or glucosylation of S. flexneri LPS are physically located on lysogenic bacteriophages, whereas the rfb cluster contains the biosynthesis genes for the common O-repeating unit (D.A.R. Simmons and E. Romanowska, J. Med. Microbiol. 23:289-302, 1987). Using a cosmid cloning strategy, we have cloned the rfb regions from S. flexneri 3a and 2a. Escherichia coli K-12 containing plasmids pYS1-5 (derived from S. flexneri 3a) and pEY5 (derived from S. flexneri 2a) expressed O-specific LPS which reacted immunologically with S. flexneri polyvalent O antiserum. However, O-specific LPS expressed in E. coli K-12 also reacted with group 6 antiserum, indicating the presence of O-acetyl groups attached to one of the rhamnose components of the O-repeating unit. This was confirmed by measuring the amounts of acetate released from purified LPS samples and also by the chemical removal of O-acetyl groups, which abolished group 6 reactivity. The O-acetylation phenotype was absent in an E. coli strain with an sbcB-his-rfb chromosomal deletion and could be restored upon conjugation of F' 129, which carries sequences corresponding to a portion of the deleted region. Our data demonstrate that E. coli K-12 strains possess a novel locus which directs the O acetylation of LPS and is located in the sbcB-rfb region of the chromosomal map. 相似文献
67.
Calcium binding lysozyme from pigeon egg-white was crystallized by the hanging drop vapor diffusion technique using ammonium sulphate as a precipitant. The crystals belong to the orthorhombic system, space group P2(1)2(1)2(1), and have unit cell dimensions of a = 34.2 A, b = 34.8 A, and c = 99.4 A. One asymmetric unit contains one molecule of the pigeon lysozyme. The crystals diffract X-rays at least to 2.0 A resolution and are suitable for high resolution structure analysis. The diffraction data up to 3.0 A resolution were collected with a diffraction image processor, DIP100, using a Fuji imaging plate as an area detector. The structure was solved by the molecular replacement technique and refined to an R factor of 0.216. Least-squares fitting of the main-chains of pigeon egg-white lysozyme with those of chicken egg-white lysozyme and baboon alpha-lactalbumin showed that the main-chain folding of pigeon lysozyme is more similar to that of chicken lysozyme than that of alpha-lactalbumin. The largest differences between the pigeon and chicken lysozymes are in the surface loop regions. 相似文献
68.
A soluble protein isolated from mitochondria has been found to modulate the voltage-dependent properties of the mitochondrial outer membrane channel, VDAC. This protein, called the VDAC modulator, was first found inNeurospora crassa and then discovered in species from other eukaryotic kingdoms. The modulator-containing fraction (at a crude protein concentration of 20 µg/ml) increases the voltage dependence of VDAC channels over 2–3-fold. At higher protein concentrations (50–100 µg/ml), some channels seem to remain in a closed state or be blocked while others display the higher voltage dependence and are able to close at low membrane potentials. By increasing the steepness of the voltage-dependent properties of VDAC channels, this modulator may serve as an amplifierin vivo to increase the sensitivity of the channels in response to changes in the cell's microenvironment, and consequently, regulate the metabolic flux across the outer mitochondrial membrane by controlling the gating of VDAC channels. 相似文献
69.
Metastable ripple phase of fully hydrated dipalmitoylphosphatidylcholine as studied by small angle x-ray scattering 总被引:1,自引:1,他引:0 下载免费PDF全文
Fully hydrated dipalmitoylphosphatidylcholine (DPPC) undergoes liquid crystalline to metastable Pβ, phase transition in cooling. A small angle x-ray scattering study has been performed for obtaining further evidence about the structure of this phase. From a high-resolution observation of x-ray diffraction profiles, a distinct multipeak pattern has become obvious. Among them the (01) reflection in the secondary ripple structure is identified clearly. There are peaks assigned straightforwardly to (10) and (20) reflections in the primary ripple structure and peaks assigned to (10) and (20) reflections in the secondary ripple structure. Therefore the multipeak pattern is due to superposition of the reflections cause by the primary and secondary ripple structures. The lattice parameters are estimated as follows: for the primary ripple structure a = 7.09 nm, b = 13.64 nm, and γ = 95°, and for the secondary ripple structure a = 8.2 nm, b = 26.6 nm, and γ = 90°. The lattice parameters thus obtained for the secondary ripple structure are not conclusive, however. The hydrocarbon chains in the primary ripple structure have been reported as being tilted against the bilayer plane and, on the other hand, the hydrocarbon chains in the secondary ripple structure are likely to be perpendicular to the bilayer plane. This fact seems to be related to a sequential mechanism of phase transitions. On heating from the Lβ, phase where the hydrocarbon chains are tilted the primary ripple structure having tilted hydrocarbon chains takes place and on cooling from the Lα phase where the hydrocarbon chains are not tilted the secondary ripple structure with untilted chains tends to be stabilized. It appears that the truly metastable ripple phase is expressed by the second ripple structure although in the course of the actual cooling transition both the secondary and primary ripple structures form and coexist. 相似文献
70.
Early Stimulation of Phosphatidylcholine Biosynthesis During Wallerian Degeneration of Rat Sciatic Nerve 总被引:7,自引:7,他引:0
V. Natarajan Jeffrey K. Yao Peter J. Dyck Harald H. O. Schmid 《Journal of neurochemistry》1982,38(5):1419-1428
Phospholipid metabolism was studied in rat sciatic nerve during Wallerian degeneration induced by crush injury. Portions of crushed sciatic nerve, incubated with labeled substrates, showed significantly higher phosphatidylcholine synthesis than normal nerve, prior to any measurable alterations of phospholipid composition. Maximum synthesis occurred 3 days after crush injury, at which time the metabolism of other phospholipids was unchanged. After a rapid decrease in biosynthetic activity, a second phase of enhanced phosphatidylcholine synthesis occurred, beginning 6 days after crush injury. Increased incorporation of [33P]phosphate, [2-3H]glycerol, and [Me-14C]choline indicated stimulation of de novo synthesis of phosphatidylcholine 3 days after injury. Neither base exchange reactions nor sequential methylation of ethanolamine phospholipids contributed significantly to phosphatidylcholine synthesis. Assay of certain key enzymes under optimal conditions in subcellular fractions of sciatic nerve revealed higher activities of cholinephosphate cytidyltransferase, choline phosphotransferase, and acyl-CoA:lysophosphatidylcholine acyltransferase in injured nerve, while choline kinase activity remained unchanged. This indicates that stimulation of phosphatidylcholine synthesis occurs via the cytidine nucleotide pathway, as well as by increased acylation of lysophosphatidylcholine. Although the cause of stimulated phosphatidylcholine synthesis remains unexplained, it is possible that trace amounts of lysophospholipids or other metabolites produced by injury-enhanced phospholipase activity may be responsible. 相似文献