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41.
We cloned and sequenced cDNAs encoding calponin (Calp) and SM22 (smooth muscle-specific 22-kDa protein) from rat aorta (RaA) smooth muscle (Smu) cells. The 1504-bp calp cDNA contains a single open reading frame (ORF) which encodes 297 amino acids (aa) (Mr 33 342). The 1186-bp SM22 cDNA contains a single ORF which encodes 201 aa (Mr 22 601). There were 43% identical aa in a 181-aa overlap between RaA Calp and SM22. Especially for the C-terminal region of SM22 and for the first repeat motif of Calp, 70% identity was observed. Northern blot analysis revealed that the calp and SM22 mRNAs were expressed in RaA Smu, but not in rat cardiac and skeletal muscles. SM22 mRNA was much more abundant than calp mRNA in RaA (3- to 4-fold). The expression levels of the calp and SM22 mRNAs in RaA showed a significant increase for 5 to 15 week old rats (1.5- to 3-fold) with vascular development and blood pressure elevation. No significant differences were observed in the expression of the RaA calp and SM22 mRNAs between normotensive (Wistar Kyoto) and spontaneously hypertensive rats (SHR). 相似文献
42.
N. M. Jansonius J. H. van Hateren 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,172(4):467-471
We recorded from the spiking on-off unit in the first optic chiasm (between lamina and medulla) in the blowfly Calliphora vicina, and investigated its spatial properties. The receptive field extends over (11.4±0.9)° horizontally and (8.7±0.6)° vertically, i.e. about 7 by 5 interommatidial angles. The line spread function of the on-off unit — calculated from its response to moving sinusoidal gratings — has a half-width of (2.3±0.2)°. This half-width is slightly broader than that of the photoreceptor. Lateral inhibition occurs when two different areas of the receptive field are stimulated simultaneously. Fast temporal adaptation (i.e. adaptation to trains of short light pulses) takes place independently in different areas of the receptive field. 相似文献
43.
44.
J. Mogdans H. -U. Schnitzler J. Ostwald 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,172(3):309-323
1. | Echolocating bats (Eptesicus fuscus) were trained to discriminate between simulated targets consisting of one or two echo-wavefronts with internal time delays of up to 100 s. Spectral and temporal properties and total signal energy of the targets were evaluated and predictions for performances of bats derived from receiver models were compared with measured performances. |
2. | Eptesicus fuscus was able to discriminate a one-wavefront target from two-wavefront targets with distinct internal time delays (12 s, 32–40 s and 52–100 s). Performance was not affected by changes in total signal energy. Bats also successfully discriminated between two-wavefront targets with different internal time delays. |
3. | Performance predicted from differences in total energy between targets did not match the measured performance, indicating that bats did not rely on total echo energy. This finding is also supported by the behavioral data. Performance predicted from spectral and temporal receiver models both matched the measured performance and, therefore, neither one of these models can be favored over the other. |
4. | The behavioral data suggest that Eptesicus fuscus did not transform echo information into estimates of target range separation and, therefore, did not perceive the two wavefronts of each simulated two-wavefront echo as two separate targets. |
45.
A. B. Fulton 《Journal of cellular biochemistry》1993,52(2):148-152
The cytoskeleton of most cells is complex and spatially diverse. The mRNAs for some cytoskeletal proteins are localized, suggesting that synthesis of these proteins may occur at sites appropriate for function or assembly. mRNA concentrations were first observed for several oocyte and embryonic mRNAs. Some insight has been gained into the mechanisms that help to position these mRNAs. More surprising to some, many cytoskeletal mRNAs are also localized. Among them are mRNAs for actin, tubulin, intermediate filaments, and a variety of associated proteins. Different mRNAs in the same cell can be located in different places; the same mRNA can be located in different places; the same mRNA can be located differently at different times of development. For example, we observed vimentin mRNA in developing chicken muscle cultures by fluorescent in situ hybridization. We found that vimentin mRNA takes on a variety of positions during myogenesis, ending up located with its cognate protein at costameres. This last pattern is significant because it is too finely structured to have a function in the soluble phase and probably reflects contranslational assembly of this particular protein. Analogies can be made between oocyte or embryonic positions (animal/vegetal poles, oocyte cortex, and interior) and somatic cell positions (anterior/posterior and cell cortex/cell center). These analogies may point to conserved mechanisms for moving and retaining mRNA. Localization of cytoskeletal synthesis, through the mRNA or by other means, may prove as important for assembling and maintaining differentiated cytoskeletal structures and somatic cells as mRNA location is for organizing the embryo. Mechanisms that permit mRNA localization are likely to be conserved. 相似文献
46.
Garðar Guðmundsson 《Vegetation History and Archaeobotany》1996,5(1-2):13-23
Lyme-grass (Elymus arenarius L.) was harvested and processed for human consumption along the southern coast of Iceland until the beginning of this century.
The origin of this exploitation is not known, but lyme-grass may have been gathered for this purpose already in the Viking
Age. The system of processing lyme-grass is complex, and special implements and facilities are needed. The method is similar
to traditional processing methods for cereals. Extensive research on Icelandic ethnographic observations was undertaken to
establish the exact methods and sequence of operations that was involved. On the basis of this, a set of archaeological experiments
was performed to test the viability of the processing techniques outlined in the written records. A model describing the harvesting
and processing of lyme-grass is presented. 相似文献
47.
Successful expression in pollen of various plant species of in vitro synthesized mRNA introduced by particle bombardment 总被引:5,自引:0,他引:5
Toshinori Tanaka Masahiro Nishihara Motoaki Seki Atsushi Sakamoto Kunisuke Tanaka Kohei Irifune Hiromichi Morikawa 《Plant molecular biology》1995,28(2):337-341
Gold particles coated with -glucuronidase (GUS) mRNA with a 5 cap structure that had been synthesized in vitro were introduced, by use of a pneumatic particle gun, into pollen grains of lily (Lilium longiflorum), freesia (Freesia refracta) and tulip (Tulipa gesneriana). A fluorometric assay for the GUS activity indicated that in vitro synthesized GUS mRNA introduced into these pollen cells by particle bombardment was successfully expressed. GUS activity in extracts of the bombarded lily pollen became detectable fluorometrically within 30 min after bombardment, peaked at 6 h, then gradually decreased. This activity changed as a function of the developmental stage of the pollen cell of lily. 相似文献
48.
We have purified and characterized poly(A) polymerases (PAPs) from Pisum sativum, Brassica juncea, and Zea mays. Through chromatography on DEAE-Sepharose and heparin-Sepharose, these PAPs copurified as a single enzyme along with RNPs that could provide RNA substrates for the enzyme. More extensive purification by chromatography on MonoQ resulted in the resolution of the PAPs into as many as three fractions. One of these (PAP-I) contained a 43-kDa polypeptide immunologically related to the yeast PAP, and two others (PAP-II and PAP-III) contained RNAs that could serve as substrates for polyadenylation. These fractions by themselves possessed little PAP activity, but mixtures containing combinations of these displayed substantial activity. Similar PAP factors (PAP-I and PAP-III) were identified after fractionation of extracts prepared from Brassica juncea and Zea mays. The factors from one plant were completely interchangeable with those from different plants. We conclude that the poly(A) polymerases present in vegetative plant tissues consist of more than one component. In this respect, they are substantially different from other reported plant, mammalian, and yeast PAPs. 相似文献
49.
Processing of Procarboxypeptidase E into Carboxypeptidase E Occurs in Secretory Vesicles 总被引:2,自引:0,他引:2
Abstract: Carboxypeptidase E (CPE) functions in the posttranslational processing of bioactive peptides. Like other peptide processing enzymes, CPE is initially produced as a precursor ("proCPE") that undergoes posttranslational processing at a site containing five adjacent Arg residues near the N-terminus and at other sites near the C-terminus of proCPE. The time course of the N-terminal processing step suggests that this conversion occurs in either the Golgi apparatus or the secretory vesicles. To delineate further the site of proCPE processing, pulse/chase analysis was performed under conditions that block transit out of the Golgi apparatus (brefeldin A, carbonyl cyanide m -chlorophenylhydrazone, or 20°C) or that block acidification of vesicles (chloroquine, monensin, or ammonium chloride). The results of these analysis suggest that efficient proCPE processing requires an acidic post-Golgi compartment. To test whether known processing enzymes can perform this cleavage, purified proCPE was incubated with furin, prohormone convertase 1, or a dynorphin converting enzyme, and the products were analyzed on denaturing polyacrylamide gels. Furin cleaves proCPE within the N-terminal region, although the reaction is not very efficient, requiring relatively large amounts of furin or long incubation times. The other two peptide processing enzymes did not cleave proCPE, whereas a relatively small amount of secretory granule extract was able to convert proCPE into CPE. Taken together, these findings suggest that the conversion of proCPE into CPE occurs primarily in secretory vesicles. 相似文献
50.
Abstract: This laboratory has previously reported that the maternal opioid analgesia associated with pregnancy and parturition is mediated, at least in part, by a maternal spinal cord dynorphin/κ opioid system. This analgesia is accompanied by an increase in dynorphin peptides (1–17 and 1–8) in the lumbar spinal cord. Levels of trypsin-generated arginine6 -leucine-enkephalin (Leu-Enk-Arg)-immunoreactive determinants were also determined and used to reflect the content of dynorphin precursor intermediates. In spinal tissue, the amount of dynorphin A (1–17) contained in the form of precursor is, at a minimum, 10-fold higher than the content of mature dynorphin A (1–17) or dynorphin (1–8). During gestational day 22, the content of dynorphin precursor is reduced significantly (∼50%). The decline in the magnitude of dynorphin precursor intermediates in the spinal cord of pregnant rats vastly exceeds the magnitude of increase in the content of dynorphin peptides (1–17 and 1–8). This difference can best be explained by postulating a corresponding increase in the rate of release of spinal cord dynorphin (1–17). It is suggested that enhanced processing of dynorphin precursor intermediates represents the initial biochemical level of adaptation of spinal dynorphin neurons to increased demands of pregnancy. 相似文献