全文获取类型
收费全文 | 195篇 |
免费 | 17篇 |
国内免费 | 3篇 |
出版年
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1964年 | 2篇 |
1960年 | 3篇 |
1959年 | 2篇 |
1956年 | 1篇 |
1952年 | 1篇 |
1950年 | 1篇 |
1948年 | 2篇 |
1945年 | 1篇 |
1943年 | 2篇 |
1940年 | 1篇 |
1936年 | 1篇 |
1922年 | 1篇 |
1908年 | 1篇 |
排序方式: 共有215条查询结果,搜索用时 30 毫秒
161.
The alteration of myosin isoform compartmentation in specific mutants of Caenorhabditis elegans 总被引:11,自引:9,他引:2 下载免费PDF全文
Myosin isoforms A and B are located at the surface of the central and polar regions, respectively, of thick filaments in body muscle cells of Caenorhabditis elegans, whereas paramyosin and a distinct core structure comprise the backbones of these filaments. Thick filaments and related structures were isolated from nematode mutants that have altered thick filament protein compositions. These mutant filaments and their complexes with specific antibodies were studied by electron microscopy to determine the distribution of the two myosins. The compartmentation of the two myosin isoforms in body wall muscle thick filaments depends not only upon the intrinsic properties of the myosins but their interactions with other components such as paramyosin and their relative quantities determined by synthesis. 相似文献
162.
Se diferencian 5 arcos de precipitatión en la técnica de inmunoelectroforesis (IEF) luego de enfrentar sueros de 16 pacientes de paracoccidioidomicosis a la paracoccidioidina. El arco l presente en todos los sueros es asimilado a arcos presuntamente específicos descritos previamente. En immunoelectroosmoforesis-inmunodifusión (IEOF-ID) se observaron bandas anódicas y bandas catódicas en todos los casos. La comparación de los resultados obtenidos con las 2 técnicas reveló siempre un mayor número de arcos en IEOF-ID lo que se debería a la aparición de los arcos de localizatión catódica 1 y 2 del inmunoelectroforegrama, tanto en el lado anódico como en el catódico de las láminas de IEOF-ID.
Summary Immunoelectroporesis (IEF) and immunoelectroosmophoresis-immunodiffusion (IEOP-ID) (1) were comparatively used in the diagnosis of 16 patients with mycologically proved paracocidioidomycosis.In IEF, 5 different precipitin arcs were found and identified with arable numbers. Arc. 1, cathodic, present in all the patients, is assimilated to specific arcs previously described by other authors.In IEOP-ID both cathodic and anodic arcs were observed in all the sera.A high number of precipitin arcs were revealed by IEOP-ID technique in comparison to IEF in every case. This should be due to the presence of cathodic arcs 1 and 2 of the immunoelectrophoregram at both sides of the IEOP-ID preparate.相似文献
163.
Loss of meiosis in Aspergillus 总被引:2,自引:0,他引:2
If strictly mitotic asexual fungi lack recombination, the conventional view
predicts that they are recent derivatives from older meiotic lineages. We
tested this by inferring phylogenetic relationships among closely related
meiotic and strictly mitotic taxa with Aspergillus conidial (mitotic)
states. Phylogenies were constructed by using DNA sequences from the
mitochondrial small ribosomal subunit, the nuclear ribosomal internal
transcribed spacers, and the nuclear 5.8S ribosomal gene. Over 920 bp of
sequence was analyzed for each taxon. Phylogenetic analysis of both the
mitochondrial and nuclear data sets showed at least four clades that
possess both meiotic and strictly mitotic taxa. These results support the
hypothesis that strictly mitotic lineages arise frequently from more
ancient meiotic lineages with Aspergillus conidial states. Many of the
strictly mitotic species examined retained characters that may be vestiges
of a meiotic state, including the production of sclerotia, sclerotium-like
structures, and hulle cells.
相似文献
164.
Lopez JV; Culver M; Stephens JC; Johnson WE; O'Brien SJ 《Molecular biology and evolution》1997,14(3):277-286
Differential rates of nucleotide substitution among different gene segments
and between distinct evolutionary lineages is well documented among
mitochondrial genes and is likely a consequence of locus-specific selective
constraints that delimit mutational divergence over evolutionary time. We
compared sequence variation of 18 homologous loci (15 coding genes and 3
parts of the control region) among 10 mammalian mitochondrial DNA genomes
which allowed us to describe different mitochondrial evolutionary patterns
and to produce an estimation of the relative order of gene divergence. The
relative rates of divergence of mitochondrial DNA genes in the family
Felidae were estimated by comparing their divergence from homologous
counterpart genes included in nuclear mitochondrial DNA (Numt, pronounced
"new might"), a genomic fossil that represents an ancient transfer of 7.9
kb of mitochondrial DNA to the nuclear genome of an ancestral species of
the domestic cat (Felis catus). Phylogenetic analyses of mitochondrial
(mtDNA) sequences with multiple outgroup species were conducted to date the
ancestral node common to the Numt and the cytoplasmic (Cymt) mtDNA genes
and to calibrate the rate of sequence divergence of mitochondrial genes
relative to nuclear homologous counterparts. By setting the fastest
substitution rate as strictly mutational, an empirical "selective
retardation index" is computed to quantify the sum of all constraints,
selective and otherwise, that limit sequence divergence of mitochondrial
gene sequences over time.
相似文献
165.
Clinical application of peripheral nerve transplantation. 总被引:9,自引:0,他引:9
Surgical reconstruction of extensive peripheral nerve injuries frequently exhausts the patient's own source of expendable autogenous nerve grafts. Nerve allografts would offer a limitless supply of graft material. A 23-cm, 10-cable sciatic nerve allograft was performed in an 8-year-old boy in September of 1988. The patient was managed with Cyclosporin A for 2 years. Forty-four months after the transplant surgery and 19 months after the cessation of Cyclosporin A therapy, the patient has evidence of nerve regeneration across the allograft with recovery of functional sensibility in his foot. In the selected patient with an otherwise irreparable nerve injury, consideration can be given to the use of a nerve allograft. 相似文献
166.
G M Hare P J Evans S E Mackinnon T J Best J R Bain J P Szalai D A Hunter 《Plastic and reconstructive surgery》1992,89(2):251-258
Functional recovery following sciatic, tibial, and peroneal nerve injury was assessed over a 1-year period using walking track analysis in the rat. Internal neurolysis did not affect nerve function. Crush injury induced a temporary, but complete, loss of function that recovered to control levels by 4 weeks. Nerve transection resulted in complete loss of function without any evidence of recovery. After nerve repair, functional recovery occurred, reaching near-optimal recovery by 12 weeks. The degree of functional recovery varied with the specific nerve involved. The sciatic nerve recovered 41 percent of function, whereas the tibial nerve recovered 54 percent of function. The peroneal nerve exhibited the highest degree of recovery, achieving functional levels similar to control values. Assessment of neural regeneration using walking track analysis appears to be a valuable addition to the traditional methods of histology and electrophysiology. 相似文献
167.
The chemical composition of highly purified plasma membrane preparations from a series of malignant Chinese hamster ovary (CHO) cell lines were undertaken to ascertain if neutral lipid, including cholesteryl ester and triacylglycerol, were present. Triacylglycerols (33-41 nmol/mg total lipid) and cholesteryl ester (226-271 nmol/mg) were measured in the plasma membranes and differences in the chemical composition of these membranes recorded. The most significant difference was a gradual decrease in the level of free cholesterol from wild type (312 +/- 7 nmol/mg total plasma membrane lipid), Pod RII-6 (268 +/- 64 nmol/mg total plasma membrane lipid), Col R-22 (243 +/- 39 nmol/mg total plasma membrane lipid) to EOT (204 +/- 20 nmol/mg total plasma membrane lipid), with a concomitant increase in the degree of saturation of the cholesteryl ester fatty acids, particularly palmitic acid. No statistically significant differences were apparent in the chemical composition of the whole cells in this series. The one-dimensional (1D) 1H-NMR spectra of the four malignant cell lines showed a gradation in intensity of lipid resonances, in the order of wild type, Pod RII-6, Col R-22 and EOT, with EOT having the strongest lipid spectrum. Interestingly, the increase in acyl-chain signal intensities in the 1H-NMR spectra of this series of CHO cells and emergence of signals from cholesterol and/or cholesteryl ester, coincide with alterations in the amount of free cholesterol and the degree of saturation of the fatty-acyl chain of the esterified cholesterol in the plasma membranes. It is our hypothesis that, together, cholesteryl ester and triacylglycerol form domains in the plasma membrane and that when the cholesteryl ester has a largely saturated fatty acid content, the lipids are in isotropic liquid phase and hence visible by NMR. 相似文献
168.
The effect of exogenous steroid hormones on the egg output of Heligmosomoides polygyrus (Nematoda: Trichostrongylidae) was examined in vitro. Using worms raised in female mice, it was found that estradiol, testosterone, and cortisone each significantly decreased egg output. Although similar trends were found using H. polygyrus raised in male mice, none of the decreases found was significant. No significant differences were found with ecdysone or progesterone treatments using worms from female or male mice. Treatment of worms with cortisone did not significantly affect retention of eggs within the uterus of H. polygyrus. Titration of the effect of cortisone on egg output indicated that levels of reduction were significant for concentrations of 5.6 x 10(-6) M to 5.6 x 10(-3) M in worms from female mice and for concentrations of 5.6 x 10(-8), x 10(-7), x 10(-5) and x 10(-3) in worms from male mice. Radioisotope labelling experiments showed incorporation of 3H-corticosterone in the nucleus of intestinal cells of H. polygyrus suggesting that its effect on egg production may be via a modulatory effect on the intestinal cells. 相似文献
169.
Blood lactate responses in older swimmers during active and passive recovery following maximal sprint swimming 总被引:2,自引:0,他引:2
P R Reaburn L T Mackinnon 《European journal of applied physiology and occupational physiology》1990,61(3-4):246-250
The purpose of this study was to determine the effect of age on three blood lactate parameters following maximal sprint swimming. The parameters examined were maximal blood lactate concentration, time to reach maximal blood lactate concentration, and half recovery time to baseline lactate concentration. These parameters were examined in 16 male competitive masters swimmers (n = 4 for each age group: 25-35, 36-45, 46-55, and 56 plus years) during both passive and active recovery following a maximal 100 m freestyle sprint. Passive recovery consisted of 60 min sitting in a comfortable chair and active recovery consisted of a 20-min swim at a self-selected pace. Capillary blood samples were obtained every 2 min up to 10 min of recovery then at regular intervals to the end of the recovery period. Curves of blood lactate concentration against time were drawn and the three parameters determined for each condition for each subject. There were no significant differences between age groups in any of the lactate parameters examined. A significant difference (P less than 0.05) was noted in each of the parameters between active and passive recovery over all age groups. As expected, active recovery produced lower maximal blood lactate concentrations, lower time to maximal blood lactate values, and lower half recovery times. These data suggest that intensive swimming training may prevent or delay the decline with age in the physiological factors affecting blood lactate values following a maximal sprint swim. Older sprint swimmers appeared to be capable of producing and removing lactic acid at the same rate as younger swimmers.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
170.
M J Whiting R A Wishart M R Gowing M E McManus A M Mackinnon 《Biochimica et biophysica acta》1989,1001(2):176-184
Rabbit hepatocytes isolated after liver perfusion with collagenase were maintained in primary monolayer culture for periods up to 96 h. Bile acid synthesis and secretion was measured by capillary gas-liquid chromatography and by a rapid enzymatic-bioluminescence assay. As expected from the bile acid profile of rabbit gallbladder bile, cholic acid was the only bile acid synthesized in detectable amounts and was produced at a linear rate of 170 pmol/h per mg cell protein from 24 to 96 h in culture. Ketoconazole (20 microM) inhibited cholic acid synthesis and secretion by 78%, whereas the bile acids chenodeoxycholic acid (100 microM), deoxycholic acid (100 microM) or lithocholic acid (2 microM) had no effect. When rat hepatocytes were cultured under identical conditions, the rate of bile acid synthesis was found to be only 12 pmol/h per mg cell protein, a value in agreement with previous work. The large difference in rates of bile acid synthesis between rabbit and rat hepatocytes may be due to rapid loss of cytochrome P-450 from rat hepatocytes when placed in monolayer culture. Although reportedly active in cholesterol 7 alpha-hydroxylation, form 4 cytochrome P-450 levels in rabbit hepatocytes did not correlate with rates of bile acid synthesis. 相似文献