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71.
72.
Henry R. Halperin Joshua E. Tsitlik Rafael Beyar Nisha Chandra Alan D. Guerci 《Annals of biomedical engineering》1987,15(3-4):385-403
Whether blood flow during cardiopulmonary resuscitation (CPR) results from intrathoracic pressure fluctuations or direct cardiac
compression remains controversial. We developed a mathematical model that predicts that blood flow due to intrathoracic pressure
fluctuations should be insensitive to compression rate over a wide range but dependent on the applied force and compression
duration. If direct compression of the heart plays a major role, however, the model predicts that flow should be dependent
on compression rate and force, but above a threshold, insensitive to compression duration. These differences in hemodynamics
produced by changes in rate and duration form a basis for determining whether blood flow during CPR results from intrathoracic
pressure fluctuations or from direct cardiac compression. The model was validated for direct cardiac compression by studying
the hemodynamics of cyclic cardiac deformation following thoracotomy in four anesthetized, 21–32-kg dogs. As predicted by
the model, there was no change in myocardial or cerebral perfusion pressures when the duration of compression was increased
from 15% to 45% of the cycle at a constant rate of 60/min. There was, however, a significant increase in perfusion pressures
when rate was increased from 60 to 150/min at a constant duration of 45%. The model was validated for intrathoracic pressure
changes by studying the hemodynamics produced by a thoracic vest (vest CPR) in eight dogs. The vest contained a bladder that
was inflated and deflated. Vest CPR changed intrathoracic pressure without direct cardiac compression, since sternal displacement
was <0.8 cm. As predicted by the model and opposite to direct cardiac compression, there was no change in perfusion pressures
when the rate was increased from 60 to 150/min at a constant duration of 45% of the cycle. Manual CPR was then studied in
eight dogs. There was no surgical manipulation of the chest. Myocardial and cerebral blood flows were determined with radioactive
microspheres and behaved as predicted from the model of intrathoracic pressure, not direct cardiac compression. At nearly
constant peak sternal force (378–426 N), flow was significantly increased when the duration of compression was increased from
short (13%–19% of the cycle) to long (40%–47%), at a rate of 60/min. Flow was unchanged, however, for an increase in rate
from 60 to 150/min at constant compression duration. In addition, myocardial and cerebral flow correlated with their respective
perfusion pressures. Thus vital organ perfusion pressures and flow for manual external chest compression are dependent on
the duration of compression, but not on rates of compression of 60 and 150/min. These data are of course similar to those
produced by vest CPR, where intrathoracic pressure is manipulated without sternal displacement, and to those predicted for
movement of blood by intrathoracic pressure changes. These data are, however, opposite to those produced by cardiac deformation
and to those predicted for movement blood by direct cardiac compression. We conclude that intrathoracic pressure fluctuations
generate blood flow during manual CPR. 相似文献
73.
Leffell MS Fallin MD Hildebrand WH Cavett JW Iglehart BA Zachary AA 《Human immunology》2004,65(1):78-89
Human leukocyte antigen (HLA) class I and II alleles were defined for 302 Lakota Sioux American Indians as part of the American Society for Histocompatibility and Immunogenetics coordinated studies on minority populations. The study group was comprised of adult volunteers from the Cheyenne River and Ogala Sioux tribes residing, respectively, on the Cheyenne River and Pine Ridge Reservations in South Dakota. Of the participants, 263 (87%) claimed full American Indian ancestry through both maternal and paternal grandparents. The study group included 25 nuclear families that were informative for genotyping. HLA phenotypes from 202 adults with no other known first-degree relative included in the study were used for calculation of allele and haplotype frequencies by maximum likelihood estimation. HLA-A, -B, and -Cw alleles were found to be in Hardy Weinberg equilibrium. Deviation from equilibrium was observed for DRB1 alleles (p=0.01), but could be attributed to the sample size and the occurrence of some genotypes with low expected frequencies. Polymorphism among the Sioux was limited with four to seven alleles comprising >80% of those observed at each locus. Several alleles were found at high frequency (0.05-0.30) among the Sioux that are also prevalent in other Native Americans and Alaska Natives, including: A*2402, *3101, and *0206; B*3501,*3901, *5101, and *2705; Cw*0702, *0404, and *03041; DRB1*0407, *0404, *1402, and *16021; and DQB1*0301, *0302, and *0402. DRB1*0811, which has been only previously described in Navajo and Tlingit Indians, was found to occur at a frequency of 0.119 among the Sioux. Two new alleles were defined among the Sioux: Cw*0204 and DRB1*040703, which were found in two and four individuals, respectively. In the haplotype analyses, significant linkage disequilibrium (p<0.00001) was seen in all pairwise comparisons of loci and numerous two and three locus haplotypes were found to have strong, positive linkage disequilibrium values. The two most common extended haplotypes among the Sioux, determined by maximum likelihood estimation and genotyping were: A*31012, B*3501, Cw*0404, DRB1*0407; and A*24021, B*3501, Cw*0404, DRB1*0404. 相似文献
74.
75.
Assessment of the epidemic potential of a new strain of rotavirus associated with the novel G9 serotype which caused an outbreak in the United States for the first time in the 1995-1996 season 下载免费PDF全文
Clark HF Lawley DA Schaffer A Patacsil JM Marcello AE Glass RI Jain V Gentsch J 《Journal of clinical microbiology》2004,42(4):1434-1438
Rotavirus causes severe morbidity in developed countries and frequent deaths (> or = 500,000 per year) in less-developed countries. Historically, four serotypes--G1, G2, G3, and G4-have predominated; they are distinguished by one of two surface neutralization antigens (VP7). However, in 1983 and 1984 we described a new rotavirus serotype, designated G9, in five children hospitalized for diarrhea in Philadelphia, Pa. G9 rotavirus was not identified again in the Western Hemisphere until it caused ca. 50% of the rotavirus disease detected in Philadelphia in the 1995-1996 season. This outbreak allowed us to question whether a rotavirus strain completely new to a well-studied community would target either very young infants or older children, cause especially severe disease, or completely displace previously extant serotypes. We observed a significant excess of G9 infections in younger infants (especially in those < 6 months old) that might be attributed to the lack of G9-specific antibodies in mothers. Of further note, six of the seven oldest patients with rotavirus diarrhea were infected with the G9 strains (not significant). However, the age distribution of children with rotavirus did not differ over a 5-year study period regardless of the infecting serotype. Patients with diarrhea associated with G9 strains did not have disease more severe than that caused by the G1, G2, or G3 serotype. G9 strains did not displace the other serotypes but were virtually completely replaced by G1 or G2 serotypes in the three subsequent rotavirus seasons. We conclude that the abrupt appearance of this novel rotavirus serotype did not present a special threat to public health in the community. 相似文献
76.
Simon JL Roy TD Parsons JR Rekow ED Thompson VP Kemnitzer J Ricci JL 《Journal of biomedical materials research. Part A》2003,66(2):275-282
Tight control of pore architecture in porous scaffolds for bone repair is critical for a fully elucidated tissue response. Solid freeform fabrication (SFF) enables construction of scaffolds with tightly controlled pore architecture. Four types of porous scaffolds were constructed using SFF and evaluated in an 8-mm rabbit trephine defect at 8 and 16 weeks (n = 6): a lactide/glycolide (50:50) copolymer scaffold with 20% w/w tri-calcium phosphate and random porous architecture (Group 1); another identical design made from poly(desaminotyrosyl-tyrosine ethyl ester carbonate) [poly(DTE carbonate)], a tyrosine-derived pseudo-polyamino acid (Group 2); and two poly(DTE carbonate) scaffolds containing 500 microm pores separated by 500-microm thick walls, one type with solid walls (Group 3), and one type with microporous walls (Group 4). A commercially available coralline scaffold (Interpore) with a 486-microm average pore size and empty defects were used as controls. There was no significant difference in the overall amount of bone ingrowth in any of the devices, as found by radiographic analysis, but patterns of bone formation matched the morphology of the scaffold. These results suggest that controlled scaffold architecture can be superimposed on biomaterial composition to design and construct scaffolds with improved fill time. 相似文献
77.
78.
Joshua K. Meisner Donna M. Martin 《American journal of medical genetics. Part C, Seminars in medical genetics》2020,184(1):81-89
CHARGE syndrome is characterized by a pattern of congenital anomalies (Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth, Genital abnormalities, and Ear abnormalities). De novo mutations of chromodomain helicase DNA binding protein 7 (CHD7) are the primary cause of CHARGE syndrome. The clinical phenotype is highly variable including a wide spectrum of congenital heart defects. Here, we review the range of congenital heart defects and the molecular effects of CHD7 on cardiovascular development that lead to an over‐representation of atrioventricular septal, conotruncal, and aortic arch defects in CHARGE syndrome. Further, we review the overlap of cardiovascular and noncardiovascular comorbidities present in CHARGE and their impact on the peri‐operative morbidity and mortality in individuals with CHARGE syndrome. 相似文献
79.
Reliability and validity of the Biodex system 3 pro isokinetic dynamometer velocity,torque and position measurements 总被引:1,自引:1,他引:1
Drouin JM Valovich-mcLeod TC Shultz SJ Gansneder BM Perrin DH 《European journal of applied physiology》2004,91(1):22-29
This study quantitatively assessed the mechanical reliability and validity of position, torque and velocity measurements of the Biodex System 3 isokinetic dynamometer. Trial-to-trial and day-to-day reliability were assessed during three trials on two separate days. To assess instrument validity, measurement of each variable using the Biodex System 3 dynamometer was compared to a criterion measure of position, torque and velocity. Position was assessed at 5° increments across the available range of motion of the dynamometer. Torque measures were assessed isometrically by hanging six different calibrated weights from the lever arm. Velocity was assessed (30°/s to 500°/s) across a 70° arc of motion by manually accelerating the weighted lever arm. With the exception of a systematic decrease in velocity at speeds of 300°/s and higher, the Biodex System 3 performed with acceptable mechanical reliability and validity on all variables tested.DisclosureThe Biodex dynamometer used for this investigation was donated to the laboratory by Biodex Medical Systems. The authors have no commercial or proprietary interest in this device. 相似文献
80.
McRobert SP Tompkins L Barr NB Bradner J Lucas D Rattigan DM Tannous AF 《Behavior genetics》2003,33(3):347-356
Many aspects of the reproductive behavior of Drosophila melanogaster are modified dramatically by experience and age. Males' courtship of immature males and fertilized females decreases over time. Females' receptivity to copulation, and the behaviors that females perform and elicit, are affected by their age and sexual experience. We show that mutations in a raised stock affect all of these age- and experience-dependent aspects of male and female sexual behavior. Experience has no effect on raised males' courtship of immature males and has opposite effects on raised and wild-type males' courtship of fertilized females. In comparison to controls, raised females become sexually mature at an earlier age, and sexually mature raised virgin females copulate more quickly. Following mating, raised females elicit more courtship and remate faster and more frequently than control females. 相似文献