首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2723篇
  免费   250篇
  国内免费   13篇
耳鼻咽喉   14篇
儿科学   46篇
妇产科学   38篇
基础医学   438篇
口腔科学   33篇
临床医学   323篇
内科学   626篇
皮肤病学   64篇
神经病学   123篇
特种医学   93篇
外科学   297篇
综合类   17篇
一般理论   1篇
预防医学   337篇
眼科学   92篇
药学   224篇
中国医学   14篇
肿瘤学   206篇
  2024年   3篇
  2023年   31篇
  2022年   94篇
  2021年   217篇
  2020年   74篇
  2019年   120篇
  2018年   121篇
  2017年   62篇
  2016年   97篇
  2015年   95篇
  2014年   133篇
  2013年   143篇
  2012年   228篇
  2011年   191篇
  2010年   99篇
  2009年   90篇
  2008年   150篇
  2007年   134篇
  2006年   130篇
  2005年   117篇
  2004年   108篇
  2003年   94篇
  2002年   81篇
  2001年   46篇
  2000年   27篇
  1999年   35篇
  1998年   20篇
  1997年   12篇
  1996年   17篇
  1995年   9篇
  1994年   9篇
  1993年   11篇
  1992年   23篇
  1991年   19篇
  1990年   13篇
  1989年   11篇
  1988年   27篇
  1987年   14篇
  1986年   13篇
  1985年   17篇
  1984年   10篇
  1983年   9篇
  1982年   5篇
  1981年   2篇
  1980年   6篇
  1979年   6篇
  1975年   2篇
  1968年   5篇
  1966年   1篇
  1964年   1篇
排序方式: 共有2986条查询结果,搜索用时 15 毫秒
971.
Adjuvants are essential vaccine components used to enhance, accelerate, and/or prolong adaptive immunity against specific vaccine antigens. In this study, we compared the adjuvanticity of two adjuvant formulations containing de-O-acylated lipooligosaccharide (dLOS), a toll-like receptor 4 agonist, on the Japanese encephalitis (JE) vaccine in mice. Mice were immunized once or twice at a two-week interval with inactivated JE vaccine in the absence or presence of adjuvant. We found that both the alum- and the liposome-based formulation induced significantly faster and higher serum IgG antibody responses as compared with the non-adjuvanted vaccine after either one or two immunizations. The antibody titers of the mouse immune sera correlated with 50% plaque reduction neutralization test (PRNT50) antibody titers. In addition, the dLOS/liposome formulation was more effective in inducing a Th1-type immune response than the dLOS/alum formulation, as suggested by a strong antigen-specific interferon (IFN)-γ response. Based on these results, we suggest that both alum- and liposome-based adjuvant formulations containing dLOS may be used for the development of JE vaccines with improved immunogenicity.  相似文献   
972.

Background

Chemicals in nail products have been linked to numerous health concerns.

Methods

We recruited Vietnamese‐American nail salon owners and workers in California and randomized salons into an intervention or control group. Owners in the intervention group received training and then provided education to workers in their salons on best practices to reduce workplace chemical exposures. Methyl methacrylate (MMA), toluene, and total volatile organic compounds (TVOCs) were measured using personal air monitors worn by workers during the work‐shift.

Results

We enrolled 77 salons (37 intervention and 40 control) and 200 workers. There was no significant intervention effect between the two groups. However, MMA and TVOCs were higher for workers who used gel polish and acrylic nails as well as in busy salons.

Conclusions

Although the intervention did not show reductions in chemical levels, identifying worker tasks and salon characteristics that predict chemical levels can inform future interventions to reduce exposures.
  相似文献   
973.
Dengue virus infection is an increasingly important tropical disease, causing 100 million cases each year. Symptoms range from mild febrile illness to severe hemorrhagic fever. The pathogenesis is incompletely understood, but immunopathology is thought to play a part, with antibody-dependent enhancement and massive immune activation of T cells and monocytes/macrophages leading to a disproportionate production of proinflammatory cytokines. We sought to investigate whether a defective population of regulatory T cells (T reg cells) could be contributing to immunopathology in severe dengue disease. CD4(+)CD25(high)FoxP3(+) T reg cells of patients with acute dengue infection of different severities showed a conventional phenotype. Unexpectedly, their capacity to suppress T cell proliferation and to secrete interleukin-10 was not altered. Moreover, T reg cells suppressed the production of vasoactive cytokines after dengue-specific stimulation. Furthermore, T reg cell frequencies and also T reg cell/effector T cell ratios were increased in patients with acute infection. A strong indication that a relative rise of T reg cell/effector T cell ratios is beneficial for disease outcome comes from patients with mild disease in which this ratio is significantly increased (P < 0.0001) in contrast to severe cases (P = 0.2145). We conclude that although T reg cells expand and function normally in acute dengue infection, their relative frequencies are insufficient to control the immunopathology of severe disease.  相似文献   
974.
Objective The aim of this study was to evaluate a postural change test during sinus ultrasound, compared with CT scan, in case of partial sinusogram to differentiate air-fluid level from mucosal thickening. Design Prospective clinical investigation. Setting Medical intensive care unit. Patients 150 intubated patients. Interventions Patients were examined by sinus ultrasound in half-sitting position. A partial sinusogram was defined as the sole visualization of the hyperechogenic posterior wall of the sinus. In this situation, a postural change was performed and ultrasound was achieved in supine position. If the partial sinusogram disappeared when the patient was placed in a supine position (positive test), the partial sinusogram was an air-fluid level. If the partial sinusogram did not disappear (negative test), we considered it as a mucosal thickening. The CT and ultrasound were performed on the same day. Radiological maxillary sinusitis (RMS) on CT was defined as the presence of an air-fluid level. Absence of RMS on CT was defined as normal sinus or as the presence of mucosal thickening. Measurements and results 300 sinuses were examined. A partial sinusogram was found in 90 sinuses and CT scan confirmed the presence of RMS in 55 sinuses (61%). Sensitivity, specificity, positive predictive value, and negative predictive value of postural change test compared with CT were, respectively, 94.6, 85.6, 91.2 and 90.9%. The positive predictive value increased from 61 to 91.2% after the postural change test. Conclusions In case of a partial sinusogram, a postural change increases the accuracy of ultrasound to diagnose RMS.  相似文献   
975.
976.
Anecdotal reports have suggested that transplantation of hepatitis C virus (HCV) antibody positive (Ab+)/nucleic acid test negative (NAT?) donor kidneys into HCV negative recipients is not associated with HCV transmission. We reviewed our center's outcomes of 32 HCV negative patients who received kidney allografts from 25 donors who were HCV Ab+/NAT?. The mean recipient age was 56.9 ± 12.1 years and the mean donor age was 41.5 ± 14 years, with a median Kidney Donor Profile Index (KDPI) of 68%. Twelve donors (48%) met Public Health Service (PHS) increased risk status. All patients received antithymocyte globulin induction followed by tacrolimus, mycophenolate mofetil, and steroid maintenance immunosuppression. With a mean follow‐up posttransplant of 10 ± 2.7 months, 1‐ and 3‐ month serum creatinine levels were 1.7 ± 0.8 and 1.3 ± 0.4, respectively, and patient and graft survival rates were 100% and 97%, respectively. Fourteen patients (44%) seroconverted and became HCV Ab+ posttransplant. However, all 32 patients were HCV RNA negative at 1‐ and 3‐ months posttransplant, and 27 and 8 patients tested at 6‐ and 12‐months posttransplant, respectively, remain HCV RNA negative. In conclusion, transplantation of HCV Ab+/NAT? kidneys to HCV negative recipients frequently causes HCV Ab seroconversion but not HCV viremia.  相似文献   
977.
OBJECTIVE: To determine whether the systolic fraction (SF) of the pulmonary venous flow (PVF), measured by transesophageal echocardiography (TEE) could be used to estimate the pulmonary artery occlusion pressure (PAOP). DESIGN: Prospective clinical investigation. PATIENTS: Nineteen intubated patients with ARDS. INTERVENTIONS: Doppler examinations with measurement of the SF of the PVF (ie, the systolic velocity-time integral expressed as a fraction of the sum of systolic and early diastolic velocity-time integrals) were performed simultaneously with measurements of PAOP via a right heart catheter at 0 cmH2O PEEP (ZEEP), at PEEP = 8 cmH20 and at PEEP = 16 cmH2O. MEASUREMENTS AND MAIN RESULTS: At ZEEP, PAOP was inversely correlated with the SF of the PVF (r = -.89). The difference of SF between the group with PAOP <18 mm Hg and the group with PAOP > or = 18 mm Hg was statistically significant (P < .05). A SF > or = 55% predicted a PAOP < 15 mm Hg with a positive predictive value of 100% (95% CI = 63-100%). A SF < or = 40% predicted a PAOP > or =18 mm Hg with a positive predictive value of 100% (95% CI = 52-100%). At PEEP = 8 cm H20 (12 patients studied) and at PEEP = 16 cmH2O (10 patients studied), PAOP was inversely correlated with the SF of the PVF: r = -.84, and r = -.85, respectively. CONCLUSION: The SF of the PVF measured by Pulsed Doppler TEE seems to be a valuable index to estimate the left ventricular filling pressure in mechanically ventilated patients with ARDS.  相似文献   
978.

Purpose

To identify all available reconstruction methods for a total sacrectomy. Secondarily, we aimed to evaluate outcomes based on different interventions.

Methods

We searched PubMed to identify sacral resections for tumors requiring internal fixation for stabilization. Demographic information, fixation techniques and postoperative outcomes were abstracted.

Results

Twenty-three publications (43 patients) met inclusion criteria from an initial search of 856 (κ 0.93). Mean age was 37 years and follow-up was 33 months. Fixation methods included a combination of spinopelvic fixation (SPF), posterior pelvic ring fixation (PPRF), and/or anterior spinal column fixation (ASCF). For the purposes of analysis, patients were segregated based on whether they received ASCF. Postoperative complications including wound/instrument infections, GI or vascular complications were reported at a higher rate in the non-ASCF group (1.63 complications/patient vs. 0.7 complications/patient). Instrument failure was seen in 5 (16.1 %) out of the 31 patients with reported outcomes. Specifically, 1 out of 8 patients (12.5 %) with ASCF compared with 4 out of 23 patients (17.4 %) without ASCF had hardware failure. At final follow-up, 35 of 39 patients were ambulating.

Conclusion

While surgical treatment of primary sacral tumors remains a challenge, there have been advances in reconstruction techniques following total sacrectomy. SPF has shifted from intrapelvic rod and hook constructs to pedicle and iliac screw–rod systems for improved rigidity. PPRF and ASCF have adapted for deficiencies in the posterior ring and anterior column. A trend toward a lower rate of hardware failure emerged in the group utilizing anterior spinal column support. Despite a more involved reconstruction with ASCF, surgical complications such as infection rates and blood loss were lower compared to the group without ASCF. While we cannot definitively say one system is superior to the other, based on the data gleaned from this systematic review, it is our opinion that incorporation of ASCF in reconstructing the spinopelvic junction may lead to improved outcomes. However, most importantly, we recommend that the treating surgeon operate on patients requiring a total sacrectomy based on his or her level of comfort, as these cases can be extremely challenging even among experts.  相似文献   
979.
Context: Terminalia macroptera Guill. &; Perr. (Combretaceae), a tree that grows in West Africa, has been used in traditional medicine against a variety of diseases such as hepatitis, gonorrhea, skin diseases, and diabetes.

Objective: To investigate enzyme inhibitory activity against α-glucosidase and 15-lipoxygenase (15-LO) and toxicity against brine shrimp of extracts and compounds from T. macroptera leaves.

Materials and methods: Methanol extract, ethyl acetate, and butanol extracts obtained from the methanol extract, six isolated polyphenols (chebulagic acid, chebulic acid trimethyl ester, corilagin, methyl gallate, narcissin, and rutin), and shikimic acid were evaluated for enzyme inhibition and toxicity.

Results: In enzyme inhibition assays, all extracts showed high or very high activity. Chebulagic acid showed an IC50 value of 0.05?µM towards α-glucosidase and 24.9?±?0.4?µM towards 15-LO, in contrast to positive controls (acarbose: IC50?201?±?28?µM towards α-glucosidase, quercetin: 93?±?3?µM towards 15-LO). Corilagin and narcissin were good 15-LO and α-glucosidase inhibitors, as well, while shikimic acid, methyl gallate, and chebulic acid trimethyl ester were less active or inactive. Rutin was a good α-glucosidase inhibitor (IC50 ca. 3?µM), but less active towards 15-LO. None of the extracts or the isolated compounds seemed to be very toxic in the brine shrimp assay compared with the positive control podophyllotoxin.

Conclusion: Inhibition of α-glucosidase in the gastrointestinal tract may be a rationale for the medicinal use of T. macroptera leaves against diabetes in traditional medicine in Mali. The plant extracts and its constituents show strong inhibition of the peroxidative enzyme 15-LO.  相似文献   
980.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号