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91.
Epididymal spermatozoa of the guinea pig were incubated under conditions known to promote a rapid synchronous capacitation in a large proportion of the spermatozoa (Ca2+-free medium with lysophosphatidylcholine, LC) or in Ca 2+-free medium without LC. To study the effects of altered thiol-disulfide status and content, incubations were conducted with reagents that maintain and increase thiol groups (DTT, GSH), maintain and increase disulfide groups (diamide, GSSG), or which irreversibly block thiol groups by alkylation (NEM). The permeable DTT inhibited LC-induced capacitation and at high concentrations diminished the percentage of acrosome reactions in capacitated spermatozoa. The permeable diamide exhibited a stimulatory effect upon capacitation. The largely impermeable GSH and GSSG exhibited effects similar to their respective permeable counterparts but their effects were moderate and required extremely high concentrations. The DTT inhibition of LC-induced capacitation was reversible by washing and a further 1 hr incubation. In this final incubation after removal of DTT by washing, LC was absent too so its stimulatory effect must have been accomplished prior to washing and in the presence of DTT. NEM-alkylation of the existing thiol population did not affect LC-induced capacitation but alkylation of the increased thiol population after prior DTT treatment was inhibitory of capacitation. These results suggest that the maintenance and/or formation of disulfide groups on enzymes or structural proteins may be a component of the capacitation process. In contrast, the formation and maintenance by alkylation of increased thiol groups but not the maintenance of existing thiol groups, is inhibitory of capacitation. The relevance of these findings to a role for a thiol-sensitive proteinase in capacitation is discussed.  相似文献   
92.
The phytoplankton taxonomic composition of the subsurface chlorophyllmaximum layer (SCM) was compared with that of the surface layerin July, September and November 1979 in the western North PacificOcean. Besides the use of chemical fixatives for preservablephytoplankton, serial dilution culture method was employed fornon-preservable flagellates and monads, i.e., fragile forms.The SCM was characterized by a high species diversity of preservablephytoplankton and by the numerical dominance of fragile forms.Among the fragile forms, Micromonas and Ochromonas were dominant.This dominance is consistent with their viability at low lightintensity. Cluster analysis revealed that, for blue-green algae,coccolithophorids, silicoflagellates and diatoms, a marked differenceexisted in species assemblages between the SCM and the surfacebut there was no distinct difference in dinoflagellate assemblages.The difference between both layers is discussed, as relatedto the mechanisms of formation of the SCM. 1Present address: Nodai Research Institute, Tokyo Universityof Agriculture, 1-1-1, Sakuragaoka, Setagaya-ku, Tokyo 156,Japan.  相似文献   
93.
A putative precursor of rat liver mitochondrial glutamic oxaloacetic transaminase which was about 2,000 daltons larger than the subunits of the mature enzyme synthesized in vitro was sensitive to proteases (trypsin and chymotrypsin). When this precursor was incubated with isolated mitochondria in the absence of protein synthesis, it was processed to the mature form; the mature form co-sedimented with mitochondria and was resistant to externally added proteases. Mature enzyme did not compete with this transport.  相似文献   
94.
Semen from a male dolphin in captivity was collected by electro-ejaculation and frozen to -176 degrees C. Sperm motility was excellent after thawing 10 days later. Electron microscopy showed 14-16 parallel ridges in the post-acrosomal region and two types of mitochondria in the mid-piece. The spermatozoa were capable of fusing with zona-free hamster eggs only after preincubation for 2 h, suggesting the need for sperm capacitation and acrosome reaction before fertilization in this species.  相似文献   
95.
The epididymis was reflected unilaterally or bilaterally to the abdomen in adult hamsters, leaving normally functioning testes in the scrotum. In unilateral cases, spermatozoa taken from the abdominal cauda, 1 month or more post-operatively, underwent a reversal of head agglutination and dispersed earlier, and underwent hyperactivation and fertilized cumulus-free eggs about 30-45 min sooner than did spermatozoa from the contralateral scrotal cauda. In addition, spermatozoa from the abdominal cauda began to undergo a spontaneous acrosome reaction 30-45 min earlier and to a greater extent than in control spermatozoa. Finally, in females mated at or soon after ovulation, spermatozoa ejaculated by bilaterally cryptepididymal males fertilized eggs 30-45 min before those from normal males. Other females mated to bilaterally cryptepididymal males gave birth to normal litters. The results are considered in terms of the possibility that temperature-sensitive sperm-binding macromolecules, which may be involved in sperm storage in the cauda epididymis, could be one determinant of the need for capacitation.  相似文献   
96.
Summary The lateral membrane system of the cochlear outer hair cell, consisting of the lateral plasma membrane, pillars, filamentous lattice and subsurface cisternae, is considered to be involved in the contractile movement of the isolated cochlear outer hair cell. The filamentous lattice, called the cytoskeletal spring, has been identified in the demembranated cochlear outer hair cell treated with the detergent Triton X-100. In this study, the quick-freeze, deep-etch method was applied to demonstrate the three-dimensional organization of both the filamentous and membranous structures of the lateral membrane system of cochlear outer hair cells. Treatment with saponin revealed that the inner leaflet of the lateral plasma membrane of the cochlear outer hair cell possesses more membrane particles than the outer leaflets, and that the pillars are closely associated with membrane particles in the inner leaflet of the lateral membrane. The presence of filamentous bridges between the filamentous lattice and the subsurface cisternae was also detected. We propose that the lateral membrane system in the cochlear outer hair cell may play an important role in the tuning mechanisms within the cochlea in normal hearing.  相似文献   
97.
Mature female Chinese hamsters ovulate an average of 8.8 ± 1.0 (mean ± SD) eggs per female in each estrous cycle. Superovulation can be induced in both immature and mature females by subcutaneous or intraperitoneal injections of pregnant mare serum gonadotropin (PMSG) and either human chorionic gonadotropin (hCG) or pituitary luteinizing hormone (PLH). The best superovulation in immature females was induced by the administration of 15 IU of PMSG followed 72 hr later by injection of 15 IU of hCG (about 25 eggs per female) or 0.2 mg (200 IU) PLH (about 46 eggs per female). Ovulation started about 13–15 hr after administration of hCG (or PLH) and was completed during the next 5–6 hr. Superovulation in mature females could be induced by injecting PMSG any day of the estrous cycle, but the best superovulation (about 39 eggs per female) was induced by injecting 15 IU of PMSG on day 1 (day of ovulation) followed by the injection of 0.4 mg of PLH 72 hr later. When immature females treated with the best superovulatory protocol were mated on the evening of PLH injection, only 5% of the eggs were found fertilized 50 hr after PLH administration. On the other hand, about 60% of the eggs were found fertilized in mature females mated following treatment with the best superovulatory protocol. The majority (83–85%) of superovulated eggs obtained from both immature and mature females were normally fertilized in vitro.  相似文献   
98.
99.
Moderate cell growth occurred after a long lag phase of about 100 hr when oxygen-sensitive hydrogen bacterium N34 was cultivated chemoautotrophically under 40% O2. A decrease in cell growth or viable count was not observed during the lag phase. These cells grown under 40 % O2 were oxygen-resistant because when used as inocula for fresh 40 % O2-culture, the growth lag period was less than 10 hr. Nine oxygen-sensitive colonies developed from a single oxygen-sensitive cell respectively. When these colonies were inoculated into 40% O2-culture, they showed an almost equal lag period and growth rate. These results suggest that cell growth in 40% O2-culture inoculated with oxygen-sensitive strain N34 occurred not by selection of oxygen-resistant variants which might preexist but by adaptation of very oxygen-sensitive cells to high oxygen tension. Oxygen-resistance thus developed was maintained after successive subcultures under 10% O2 for more than one year.  相似文献   
100.
Abstract: We identified GABAA receptor subunits in rat retina using PCR. The high degree of conservation among previously described members of ligand-gated anion channels in transmembrane domains was used to design degenerate sense and antisense oligonucleotides. These oligonucleotides were used as primers for PCR, which was applied to the rat retina cDNA. Analysis of clones derived from the PCR amplification identified the GABAAα1, β1, β3, and γ2 subunits and the glycine α1 subunit. In addition, two clones closely related to the human GABAAρ-subunit class were obtained. Molecular cloning revealed one of them as the rat counterpart of the human ρ2 subunit. Northern blot analysis demonstrated the expression of mRNAs for ρ subunits in retina. These results further support the hypothesis that bicuculline-insensitive GABA channels in rat retina are comprised of ρ subunits.  相似文献   
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