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71.
Victor A. Sorokin Vladimir F. Fedorov Victor S. Leontiev Yuri P. Blagoi Vladimir L. Galkin 《Macromolecular chemistry and physics.》1987,188(10):2301-2309
The helix-coil transition in Phage T2 DNA in the presence of 6,4 · 10?3 mol/l Mn2+ is studied using light scattering and UV spectroscopy. The transition range is about 0,5°C. Near the temperature of the end of melting Tf the molecular weight Mw and the radius of gyration Rz of the complex are observed to decrease to about one half. At a temperature 0,1–0,25°C higher than Tf, Mw and Rz pass through a minimum, which implies that aggregation is preceded by unwinding of DNA strands. Thus, rise in temperature rather than Mn2+ -induced aggregation causes DNA + Mn2+ melting. 相似文献
72.
Ioulia?Kobliakova Olga?Zatsepina Vera?Stefanova Vladimir?Polyakov Igor?KireevEmail author 《Chromosome research》2005,13(2):169-181
In this study we used a novel technique to reveal both longitudinal and transverse differentiation within mammalian mitotic
chromosomes. Structural changes in chromosomes that we term ‘differential decondensation’ were produced in cells that were
first incubated in hypotonic medium (15% Hanks’ solution), then adapted to normotonic conditions and thereafter exposed to
a second short hypotonic shock. Such a double hypotonic treatment (DHT) is not critical for cell viability, but considerably
elongates the G2 phase of the cell cycle. Giemsa staining of differentially decondensed chromosomes corresponds to standard
G-banding, but does not need the standard post-fixation treatment. Using ‘dynamic’ BrdU banding, we show that such ‘differential’
staining is a result of differential resistance of the R- and G-bands to DHT. Thus, early-replicating foci, markers of R-bands,
are localized in the peripheral chromatin halo, whereas late-replicating foci, corresponding to G-bands, remain associated
with the axial regions of chromatids. Remarkably, despite these major changes in the structure of the chromosomal bands, the
replication foci still preserve their discrete structure. 相似文献
73.
Gennadii D. Bukatov Sergei H. Shepelev Vladimir A. Zakharov Sergei A. Sergeev Yurii I. Yermakov 《Macromolecular chemistry and physics.》1982,183(11):2657-2665
By use of the quenching technique with 14CO and 14CO2 the number of active centers and the propagation rate constants (kp) were determined for the propylene polymerization on different titanium-magnesium catalysts in the presence and absence of an organoaluminium cocatalyst. The kp values at 70°C were found to be 500–1000 1·mol?1·s?1, which were confirmed by independent data of molecular mass measurements of the isotatic polymer after a short polymerization time (5 s). Similar isotactic and atactic kpvalues were found. The maximum number of active centers for supported titanium-magnesium catalysts can reach about 10% of the titanium content in the catalyst. The kp values of ethylene polymerization on catalysts active without an organoaluminium cocatalyst were also determined (≈ 104 l·mol?1·s?1 at 70°C). 相似文献
74.
Burova L Thern A Pigarevsky P Gladilina M Seliverstova V Gavrilova E Nagornev V Schalén C Totolian A 《APMIS : acta pathologica, microbiologica, et immunologica Scandinavica》2003,111(10):955-962
Our previous studies have indicated that the IgG-binding M-family proteins (IgGBP) of group A streptococci may be involved in eliciting experimental acute poststreptococcal glomerulonephritis (APSGN) in the rabbit. These surface proteins were also found to trigger production of anti-IgG, which might conceivably act to enhance renal deposition of immune complexes (IC). In the present study, a clinical isolate of serotype M22 (strain AL168), an isogenic double mutant deficient for both the IgGBPs Mrp and Emm, as well as mutants deficient in only one of the proteins were tested for capacity to induce glomerulonephritis. Streptococci to be used for injecting rabbits were heat-killed. Surface-bound IgG was removed by 1 M KSCN and cells were then repeatedly washed in PBS before use. Rabbits were injected intravenously with 109 cells three times a week for 8 weeks and, following one month of rest, for another 6 weeks. Deposits of IgG and C3 as well as induced chemokines TNF-alpha, IL-1beta and IL-6 were traced in cryostat sections using specific antibodies and appropriate peroxidase-labelled anti-antibodies. In four rabbits immunized with the double mutant strain, no deposits were found, and as examined by TEM, only subtle and transient renal changes were observed. In contrast, the original strain AL168 induced pronounced inflammatory and degenerative glomerular changes in all four rabbits injected, and deposits of TNF-alpha, IL-1beta and IL-6 were found in mesangial and endothelial cells. Similar deposits and glomerular changes were seen in all eight rabbits injected with the mrp-emm+ mutant and in four out of seven animals receiving the mrp+emm- mutant. There was a highly significant correlation between high levels of circulating anti-IgG and development of APSGN. These results confirm an important role of streptococcal IgGBP in triggering experimental APSGN as earlier proposed by our group. 相似文献
75.
Smooth muscle myosin filament assembly under control of a kinase-related protein (KRP) and caldesmon
Kudryashov DS Vorotnikov AV Dudnakova TV Stepanova OV Lukas TJ Sellers JR Watterson DM Shirinsky VP 《Journal of muscle research and cell motility》2002,23(4):341-351
Kinase-related protein (KRP) and caldesmon are abundant myosin-binding proteins of smooth muscle. KRP induces the assembly
of unphosphorylated smooth muscle myosin filaments in the presence of ATP by promoting the unfolded state of myosin. Based
upon electron microscopy data, it was suggested that caldesmon also possessed a KRP-like activity (Katayama et al., 1995, J Biol Chem 270: 3919–3925). However, the nature of its activity remains obscure since caldesmon does not affect the equilibrium between
the folded and unfolded state of myosin. Therefore, to gain some insight into this problem we compared the effects of KRP
and caldesmon, separately, and together on myosin filaments using turbidity measurements, protein sedimentation and electron
microscopy. Turbidity assays demonstrated that KRP reduced myosin filament aggregation, while caldesmon had no effect. Additionally,
neither caldesmon nor its N-terminal myosin binding domain (N152) induced myosin polymerization at subthreshold Mg2+ concentrations in the presence of ATP, whereas the filament promoting action of KRP was enhanced by Mg2+. Moreover, the amino-terminal myosin binding fragment of caldesmon, like the whole protein, antagonizes Mg2+-induced myosin filament formation. In electron microscopy experiments, caldesmon shortened myosin filaments in the presence
of Mg2+ and KRP, but N152 failed to change their appearance from control. Therefore, the primary distinction between caldesmon and
KRP appears to be that caldesmon interacts with myosin to limit filament extension, while KRP induces filament propagation
into defined polymers. Transfection of tagged-KRP into fibroblasts and overlay of fibroblast cytoskeletons with Cy3KRP demonstrated
that KRP colocalizes with myosin structures in vivo. We propose a new model that through their independent binding to myosin and differential effects on myosin dynamics, caldesmon
and KRP can, in concert, control the length and polymerization state of myosin filaments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
Recruitment and baseline epidemiologic profile of participants in the first phase 3 HIV vaccine efficacy trial 总被引:2,自引:0,他引:2
Harro CD Judson FN Gorse GJ Mayer KH Kostman JR Brown SJ Koblin B Marmor M Bartholow BN Popovic V;VAX Study Group 《Journal of acquired immune deficiency syndromes (1999)》2004,37(3):1385-1392
OBJECTIVE: To describe recruitment and baseline epidemiologic characteristics of volunteers in the first phase 3 placebo-controlled trial of a recombinant gp120 HIV vaccine (AIDSVAX B/B). METHODS: Volunteers were gay/bisexual men or women at risk for sexually transmitted HIV infection. Recruitment strategies, demographics, and risk factors were assessed. HIV status was determined by standard HIV-1 antibody assays. Seronegative/viremic HIV infection at enrollment was determined using the HIV-1 nucleic acid test. RESULTS: From June 1998 through October 1999, 5417 of 7185 volunteers screened were enrolled at 61 sites in the United States, Canada, and The Netherlands. Successful recruitment methods included distribution of study information at gay venues, advertising and media coverage, and referrals from volunteers. Most volunteers were altruistically motivated, men (98%), young (median, 36 years), white (83%), well educated (61% college education or more), and at high risk for HIV during the 6 months before enrollment. At baseline, 14 were HIV infected (12 were seronegative but viremic; 2 were seropositive and viremic). CONCLUSION: Men and women at high risk for sexually transmitted HIV infection were successfully recruited for the first phase 3 HIV vaccine efficacy trial. Knowledge of recruitment and baseline epidemiologic characteristics of participants in this trial will provide valuable guidance for designing and conducting future trials. 相似文献
77.
Two paralogous mitochondrial malate dehydrogenase 2 (Mdh2) genes of Xenopus laevis have been cloned and sequenced, revealing 95% identity. Fluorescence in-situ hybridization (FISH) combined with tyramide amplification discriminates both genes; Mdh2a was localized into chromosome q3
and Mdh2b into chromosome q8. One kb cDNA probes detect both genes with 85% accuracy. The remaining signals were on the paralogous
counterpart. Introns interrupt coding sequences at the same nucleotide as defined for mouse. Restriction polymorphism has
been detected in the first intron of Mdh2a, while the individual variability in intron 6 of Mdh2b gene is represented by an
insertion of incomplete retrotransposon L1Xl. Rates of nucleotide substitutions indicate that both genes are under similar
evolutionary constraints. X. laevis Mdh2 genes can be used as markers for physical mapping and linkage analysis. 相似文献
78.
79.
Cristina García-Amador Vladimir Arteaga Peralta Roberto de la Plaza Llamas Miguel Torralba Anibal Medina Velasco José Manuel Ramia 《Cirugía espa?ola》2021,99(4):282-288
BackgroundTo analyze whether clinical and analytical parameters differ according to histopathology in cases of acute appendicitis (AA).MethodsThis is a retrospective, observational study including patients (>14 years of age) admitted for suspicion of AA from 1 April 2014 to 31 July 2016. Histopathology was divided into complicated (including perforated and gangrenous AA) and uncomplicated appendicitis (phlegmonous). Sex, age, temperature of patients on admission to the Emergency Department, symptom duration, preoperative white blood cell (WBC) count, neutrophil percentage, mean platelet volume (MPV), platelet distribution width (PDW), C-reactive protein (CRP) and hospital stay were compared in the two groups.ResultsThree hundred and thirty-five patients were analyzed, and 284 were included. Appendicitis was uncomplicated in 194 (68.3%) and complicated in 90 (31.7%). Age, symptom duration, neutrophil percentage, CRP and hospital stay were higher in the complicated AA group (P < .05). The mean differences between uncomplicated and complicated AA were: age 13.2 years (95% CI: 8.2-18.2), symptom duration 14.1 hours (95% CI: 6.3-21.9), neutrophil percentage 5.0% (95% CI: 3.2-6.8), CRP 73.6 mg/l (95% CI: 50.0-97.2) and hospital stay 2.2 days (95% CI: 1.4-3.0), with p<0.05 for all these variables. A model based on the preoperative parameters (age, symptom duration, neutrophil percentage and CRP) was calculated to predict the likelihood of complicated AA. The receiver operating characteristic (ROC) of the model had an area under the curve of 0.80 (95% CI 0.75-0.85).ConclusionThis model is able to diagnose complicated AA without the need for imaging techniques, although it must be validated with prospective analysis. 相似文献
80.