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71.
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Carlos José Soares DDS MS PhD Luís Henrique Araújo Raposo DDS Paulo Vinícius Soares DDS MS PhD Paulo César Freitas Santos‐Filho DDS MS PhD Murilo Sousa Menezes DDS MS PhD Priscilla Barbosa Ferreira Soares DDS MS Denildo Magalhães DDS MS PhD 《Journal of prosthodontics》2010,19(2):130-137
Purpose: To test the hypothesis that the type of cement used for fixation of cast dowel‐and‐cores might influence fracture resistance, fracture mode, and stress distribution of single‐rooted teeth restored with this class of metallic dowels. Materials and Methods: The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu–Al cast dowel‐and‐cores cemented with one of four options: conventional glass ionomer cement (GI); resin‐modified glass ionomer cement (GR); dual‐cure resin cement (RC); or zinc‐phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135° angle with a 0.5 mm/min crosshead speed. Data were analyzed using one‐way analysis of variance (ANOVA) and the Fisher test. Two‐dimensional finite element analysis (2D‐FEA) was then performed with representative models of each group simulating a 100 μm cement layer. Results were analyzed based on von Mises stress distribution criteria. Results: The mean fracture resistance values were (in N): RC, 838.2 ± 135.9; GI, 772.4 ± 169.8; GR, 613.4 ± 157.5; ZP, 643.6 ± 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values. Conclusions: The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel‐and‐cores. 相似文献
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Luis Fernández-Mérida Guillermo E. Garcı́a-Garcı́a Raquel R. Raposo Miguel A. Esteso 《Journal of electroanalytical chemistry (Lausanne, Switzerland)》1999,466(1):38-44
From emf values of galvanic cells of the types {Na-glass ∣ NaCl (mB), HZ± (mA) ∣ AgCl(S) ∣ Ag}; {glass-H ∣ HCl (mC=0.01 mol kg?1), HZ± (mA), NaCl (mB) ∣ AgCl(S) ∣ Ag} and {glass-H ∣ HZ± (mA), NaZ (mD=0.09982 mol kg?1), NaCl (mB) ∣ AgCl(S) ∣ Ag} (where HZ± stands for dl-α-amino-n-butyric acid), activity coefficients for NaCl and the aminoacid were determined, at various relative concentrations of both compounds, in the ionic strength range of 0.1–4 mol kg?1 and 298.15 K. Likewise, activity coefficients for both the pure aminoacid hydrochloride (up to 0.5 mol kg?1) and the sodium salt of the aminoacid (up to 0.1 mol kg?1) were also determined, together with the thermodynamic ionisation equilibrium constants for these latter compounds. 相似文献
76.
Ander BP Hurtado C Raposo CS Maddaford TG Deniset JF Hryshko LV Pierce GN Lukas A 《Cardiovascular research》2007,73(2):395-403
OBJECTIVE: Dietary intake of omega-3 polyunsaturated fatty acids (PUFA) like alpha-linolenic acid (ALA) is antiarrhythmic and cardioprotective. PUFA may also be beneficial in hypertension. Altered Na(+)-Ca(2+) exchanger (NCX) activity has been implicated in arrhythmias, hypertension and heart failure and may be a target for PUFA. Thus, we tested the effects of ALA and other distinct fatty acids on the cardiac (NCX1.1) and vascular (NCX1.3) NCX isoforms. METHODS: HEK293 cells stably expressing NCX isoforms were ramped from +60 to -100 mV (over 1600 ms) in the absence and presence of 25 microM oleic acid (OA, omega-9), linoleic acid (LA, omega-6), ALA (omega-3), or eicosapentaenoic acid (EPA, omega-3). NiCl(2) (5 mM) was used to inhibit and therefore identify the NCX current. The effect of 25 microM ALA on NCX1.1 and NCX1.3 activity was also assessed in adult rat ventricular cardiomyocytes and rabbit aortic vascular smooth muscle cells (VSMC) by measuring [Ca(2+)](i) following substitution of [Na(+)](o) with Li(+). RESULTS: Application of Ni(2+) had no effect in non-transfected cells. ALA and EPA (25 microM) reduced the Ni(2+)-sensitive forward NCX1.1 current (at -100 mV) by 64% and reverse current (at +60 mV) by 57%, and inhibited the Ni(2+)-sensitive NCX1.3 forward and reverse currents by 79% and 76%, respectively. Neither OA nor LA (25 microM) affected the NCX1.1 currents, but both partially inhibited the forward and reverse mode NCX1.3 currents. Inhibition of NCX1.3 by ALA occurred at a much lower IC(50) ( approximately 19 nM) than for NCX1.1 ( approximately 120 nM). In cardiomyocytes and VSMC, ALA significantly reduced the Li(+)-induced rise in intracellular [Ca(2+)]. CONCLUSIONS: NCX1.3 is more sensitive to inhibition by ALA than NCX1.1. In addition, only omega-3 PUFA inhibits NCX1.1, but several classes of fatty acids inhibit NCX1.3. The differential sensitivity of NCX isoforms to fatty acids may have important implications as therapeutic approaches for hypertension, heart failure and arrhythmias. 相似文献
77.
N Yang SM Liu LF Zheng T Ji Y Li XL Mi H Xue W Ren JD Xu XH Zhang LS Li Y Zhang JX Zhu 《British journal of pharmacology》2010,159(8):1623-1625
Background and purpose:
5-Hydroxytryptamine (5-HT) is a key regulator of the gastrointestinal system and we have shown that submucosal neuronal 5-HT3 receptors exerted a novel inhibitory effect on colonic ion transport. The aim of the present study was to investigate the precise mechanism(s) underlying this inhibitory effect.Experimental approach:
Mucosa/submucosa or mucosa-only preparations from rat distal colon were mounted in Ussing chambers for measurement of short-circuit current (Isc) as an indicator of ion secretion. Somatostatin release was determined with radioimmunoassay. Intracellular cAMP content was measured with enzyme-linked immunoadsorbent assay (elisa). Immunohistochemical techniques were used to study the expression of 5-HT3 receptors, somatostatin and somatostatin receptors in colonic tissue.Key results:
In rat distal colonic mucosa/submucosa preparations, pretreatment with 5-HT3 receptor antagonists enhanced 5-HT-induced increases in Isc. However, in mucosa-only preparations without retained neural elements, pretreatment with 5-HT3 receptor antagonists inhibited 5-HT-induced ΔIsc. Pretreatment with a somatostatin-2 (sst2) receptor antagonist in mucosa/submucosa preparations augmented 5-HT-induced ΔIsc. Combination of sst2 and 5-HT3 receptor antagonists did not cause further enhancement of 5-HT-induced ΔIsc. Moreover, both sst2 and 5-HT3 receptor antagonists enhanced 5-HT-induced increase in intracellular cAMP concentration in the mucosa/submucosa preparations. 5-HT released somatostatin from rat colonic mucosa/submucosa preparations, an effect prevented by pretreatment with 5-HT3 receptor antagonists. Immunohistochemical staining demonstrated the presence of 5-HT3 receptors on submucosal somatostatin neurons and of sst2 receptors on colonic mucosa.Conclusion and implications:
Activation of neuronal 5-HT3 receptors in the submucosal plexus of rat colon suppressed 5-HT-induced ion secretion by releasing somatostatin from submucosal neurons. 相似文献78.
79.
Colony-stimulating factors: clinical evidence for treatment and prophylaxis of chemotherapy-induced febrile neutropenia 总被引:1,自引:0,他引:1
César Gómez Raposo Álvaro Pinto Marín Manuel González Barón 《Clinical & translational oncology》2006,8(10):729-734
The hematopoietic growth factors (HGFs) are a family of glycoproteins which plays a major role in the proliferation, differentiation,
and survival of primitive hematopoietic stem and progenitor cells, and in the functions of some mature cells. More than 20
different molecules of HGF have been identified. Among them, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage
colony-stimulating factor (GM-CSF) have been demostrated to be effective in reducing the incidence of febrile neutropenia
when administered inmediately after chemotherapy and as supportive therapy in patients undergoing bone marrow transplantation.
Chemotherapy used for treatment of cancer often causes neutropenia, which may be profound, requiring hospitalization, and
leading to potentially fatal infection. The uses of the recombinant human hematopoietic colony-stimulating factors G-CSF and
GM-CSF for treatment and prophylaxis of chemotherapy-induced febrile neutropenia will be reviewed here. 相似文献
80.