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991.
Seismic and auditory tuning curves from bullfrog saccular and amphibian papular axons 总被引:1,自引:0,他引:1
Xiaolong Yu Edwin R. Lewis David Feld 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(2):241-248
We present seismic and auditory frequency tuning curves of individual bullfrog, Rana catesbeiana, saccular and amphibian papilla axons that responded to both seismic and auditory stimuli. In this study we found: 1) most saccular axons respond well to auditory stimuli with moderate signal strength (50-70 dB SPL) as well as to seismic stimuli; 2) most amphibian papilla axons respond well to seismic stimuli as well as to auditory stimuli, and their seismic sensitivities are comparable to those of saccular axons (responding to sinusoidal stimuli with peak accelerations in the range 0.001 to 0.1 cm/S2); 3) the responses to both seismic and auditory stimuli from both saccule and amphibian papilla are tuned, i.e. the strength of the response varies with the frequency of the stimulus; and this tuning is clearly not the result of second order resonance; 4) in individual axons the tuning properties for seismic stimuli often are not the same as those for auditory stimuli, a fact that may provide clues about how the stimulus signal energy is transferred to the hair cells in each case. 相似文献
992.
993.
Physiology and taxonomy of scleractinian corals: a case study in the genus Stylophora 总被引:1,自引:0,他引:1
The morphology and skeletal characteristics of colonies of the coral genus Stylophora living on the reef edge at 1 m depth on the Jordanian coast of the Gulf of Aqaba (Red Sea) are those of S. mordax (Dana 1846) which has not been reported previously from that area. These colonies were considered earlier as ecomorphs of S. pistillata (Esper 1797) which lives down to at least 67 m on the reef slopes. Growth, organic content and metabolism were compared in colonies living at different depths (1,5,10 and 30 m). The trends of twelve parameters between 1 and 5 m were different from the variation observed between 5 and 30 m. Colonies living at 1 m have a higher chlorophyll content but a lower metabolic activity and growth rate than colonies living at 5 m. Most of these pecularities cannot be explained by the influence of environmental factors. It is therefore suggested that S. mordax is a valid taxon. 相似文献
994.
The paleontological evidence pertaining to the evolution of the modern diversity in structure and function of primate hands
is reviewed. A reconstructed digit ofPlesiadapis shows characters and functional capacities typical of an arboreal way of life. In euprimates, we describe the strepsirhine
morphotype hand, characterized by a relatively high degree of pollical divergence, features of the ulnocarpal articulation
that imply an enhanced capacity for ulnar deviation, and relatively long digits; this hand is specialized for grasping. Hand
remains ofSmilodectes, Adapis and a Messel adapiform reveal a remarkable diversity in carpal structure achieved in these Eocene adapiforms, due to differing
locomotor evolutionary pathways. The subfossil lemuriformsMegaladapis andPalaeopropithecus both show stereotyped (but different) grasping capabilities.
The simiiform morphotype hand combines a relatively low degree of pollical divergence, features of the ulnocarpal articulation
that imply a limited capacity for ulnar deviation, and relatively long metacarpals and short digits. This type of hand anatomy
is mechanically well-suited to arboreal palmigrade quadrupedalism. The hands ofPliopithecus andMesopithecus are generally monkey-like.Oreopithecus' hand fits with its presumed suspensory habits. The hand ofProconsul suggests palmigrade quadrupedalism and climbing.Australopithecus afarensis' hand remains primarily a branch-grasping organ, with indications of enhanced manipulatory abilities.Homo habilis andParanthropus robustus illustrate two lines of increased tool-use abilities.
The euprimate morphotype hand was elongated, had a short carpus and limited mobility, but the corresponding locomotor mode
remains speculative. Considerations on hand evolution in some living primate groups are included in the final summary of hand
evolution in primates. 相似文献
995.
The cyclophilin multigene family of peptidyl-prolyl isomerases. Characterization of three separate human isoforms. 总被引:8,自引:0,他引:8
D J Bergsma C Eder M Gross H Kersten D Sylvester E Appelbaum D Cusimano G P Livi M M McLaughlin K Kasyan 《The Journal of biological chemistry》1991,266(34):23204-23214
Cyclophilin (CyP), a major cytosolic protein possessing peptidyl-prolyl cis-trans isomerase activity, has been implicated as the specific receptor of the immunosuppressive drug cyclosporin A (CsA). To identify other potential CsA receptors related to CyP, two human cDNA libraries were screened under low stringency conditions using human CyP cDNA (encoding hCyP1) as a probe. Two cDNAs were identified which encode distinct proteins related to human hCyP1. These two novel proteins, designated hCyP2 and hCyP3, share 65 and 76% amino acid sequence homology with hCyP1, respectively. Both hCyP2 and hCyP3 contain NH2-terminal hydrophobic extensions of 32 and 42 amino acids, respectively. Protein-specific antibodies revealed the predominant association of hCyP2 and hCyP3 with membranes and subcellular organelles, which suggests that the amino-terminal leader sequences of the two CyP isoforms may act as signal peptides. In contrast to the results with hCyP1, Southern blot analysis indicated that both hCyP2 and hCyP3 gene sequences are represented infrequently in the human genome. Northern and Western blot analysis showed that the distribution of mRNA and proteins of the three hCyPs in differing tissues and cell types was similar. Each hCyP protein was expressed in Escherichia coli, purified, and shown to be an active peptidyl-prolyl isomerase. Substrate specificity was examined with 11 synthetic peptides (Suc-Xaa-Yaa-Pro-Phe-4-nitroanilide), and inhibition of the peptidyl-prolyl isomerase activities associated with hCyP1, hCyP2, and hCyP3 was studied with CsA, MeAla6-CsA and MeBm2t1-CsA. From both equilibrium considerations and the results of kinetic characterizations it is proposed that of these three CyP proteins, hCyP1 is the most likely intracellular target for CsA. 相似文献
996.
A serum- and glucocorticoid-regulated 4-kilobase mRNA encodes a cyclooxygenase-related protein. 总被引:21,自引:0,他引:21
M K O'Banion H B Sadowski V Winn D A Young 《The Journal of biological chemistry》1991,266(34):23261-23267
997.
R N Mitchell A C Shaw Y K Weaver P Leder A K Abbas 《The Journal of biological chemistry》1991,266(14):8856-8860
Membrane-bound immunoglobulin (mIg) is the antigen receptor on B lymphocytes mediating early events in antigen presentation and signal transduction. Wild-type human mIgM constructs transfected into the murine B-cell lymphoma A20 are expressed as transmembrane proteins with antigen presentation and signaling functions comparable to the endogenous mIgG2A; the transfected wild-type mIgM is internalized rapidly after anti-Ig cross-linking. Transfected constructs lacking the normal three-amino acid cytoplasmic tail are expressed exclusively as phosphatidylinositol-linked proteins, lack both antigen presentation and signal transduction functions, and are internalized slowly following anti-Ig binding. The molecular mass of the cytoplasmic tail-deleted phosphatidylinositol-linked Ig molecule is consistent with cleavage of the transmembrane residues during processing. Cytoplasmic domains may therefore regulate the mode of expression of membrane proteins and thereby influence their functional capabilities. 相似文献
998.
Archaeal rRNA operons 总被引:11,自引:0,他引:11
Ribosomal RNA (rRNA) operons of the archaea reflect both the unity and the diversity of this third primary taxon. They have proven to be a rich source of both molecular biological and phylogenetic information. 相似文献
999.
1000.