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   27832篇
  免费   1767篇
  国内免费   74篇
耳鼻咽喉   243篇
儿科学   625篇
妇产科学   491篇
基础医学   3908篇
口腔科学   643篇
临床医学   2585篇
内科学   5341篇
皮肤病学   478篇
神经病学   3100篇
特种医学   1128篇
外国民族医学   55篇
外科学   3838篇
综合类   361篇
一般理论   10篇
预防医学   2173篇
眼科学   786篇
药学   1938篇
中国医学   32篇
肿瘤学   1938篇
  2022年   194篇
  2021年   388篇
  2020年   233篇
  2019年   382篇
  2018年   436篇
  2017年   360篇
  2016年   400篇
  2015年   541篇
  2014年   720篇
  2013年   1072篇
  2012年   1588篇
  2011年   1641篇
  2010年   896篇
  2009年   842篇
  2008年   1553篇
  2007年   1660篇
  2006年   1589篇
  2005年   1607篇
  2004年   1539篇
  2003年   1439篇
  2002年   1401篇
  2001年   396篇
  2000年   344篇
  1999年   356篇
  1998年   310篇
  1997年   301篇
  1996年   258篇
  1995年   245篇
  1994年   211篇
  1993年   210篇
  1992年   220篇
  1991年   202篇
  1990年   181篇
  1989年   193篇
  1988年   189篇
  1987年   193篇
  1986年   171篇
  1985年   175篇
  1984年   221篇
  1983年   191篇
  1982年   230篇
  1981年   209篇
  1980年   192篇
  1979年   166篇
  1978年   152篇
  1977年   106篇
  1976年   142篇
  1975年   126篇
  1974年   152篇
  1973年   115篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Maternal obesity and gestational diabetes mellitus (GDM) are associated with obesity and diabetes risk in offspring. We tested whether maternal insulin resistance, which frequently coexists with GDM and obesity, could independently contribute to dysregulation of offspring metabolism. Female mice haploinsufficient for insulin receptor substrate-1 (IRS1-het) are hyperinsulinemic and insulin resistant during pregnancy, despite normal plasma glucose and body weight, and thus serve as a model of isolated maternal insulin resistance. Wild-type (WT) offspring of IRS1-het dams insulin resistance-exposed [IR-exposed] were compared with WT offspring of WT dams. Despite no differences in adiposity, male IR-exposed pups were glucose intolerant (P = 0.04) and hyperinsulinemic (1.3-fold increase, P = 0.02) by 1 month of age and developed progressive fasting hyperglycemia. Moreover, male IR-exposed pups challenged with high-fat diet exhibited insulin resistance. Liver lipidomic analysis of 3-week-old IR-exposed males revealed increases in the 16:1n7 fraction of several lipid classes, suggesting increased Scd1 activity. By 6 months of age, IR-exposed males had increased lipid accumulation in liver as well as increased plasma refed fatty acids, consistent with disrupted lipid metabolism. Our results indicate that isolated maternal insulin resistance, even in the absence of hyperglycemia or obesity, can promote metabolic perturbations in male offspring.  相似文献   
993.

Background

The T-cell activation Rho GTPase–activating protein (TAGAP) gene has a regulatory role in T cell activation. We have previously suggested a correlation between the TAGAP-associated single nucleotide polymorphism rs212388 and protection from anal sepsis in Crohn's disease (CD) patients. The present study sought to evaluate TAGAP's expression in colonic tissue of CD patients with varying disease severity and location.

Materials and methods

Five transverse, 17 left, and five sigmoid colectomy specimens from 27 CD patients with varying disease severity (16 male, mean age at diagnosis 26.4 ± 2.2 y) were evaluated for TAGAP messenger RNA expression. Fisher exact, Mann–Whitney, and Welch two-sample t-tests were used for statistical evaluation. Immunohistochemistry confirmed results.

Results

Patients with tissue demonstrating lower TAGAP messenger RNA expression (less than the overall mean) were younger at diagnosis (mean age 21.1 ± 6.3 versus 32.5 ± 13 y, P = 0.009). Increased TAGAP expression was seen in moderate or severely diseased tissue versus tissue with no or mild disease (RQ = 1.3 ± 0.34 versus 0.53 ± 0.09, P = 0.050). This was the most dramatic in the sigmoid colon (P = 0.041). TAGAP expression was increased in more distal tissue with a significant difference seen when comparing transverse versus sigmoid colon with moderate or severe disease (0.51 ± 0.14 versus 1.9 ± 0.37, P = 0.049).

Conclusions

Colonic expression of TAGAP in CD patients varied according to disease severity and location, being the most elevated in patients with severe disease in the sigmoid colon. Whether changes in TAGAP expression are a result of disease response or inherent to the disease pathophysiology itself remains to be determined. This gene warrants further investigation for its role in CD.  相似文献   
994.
995.

Background

Autologous bone flap reinsertion follows as a second surgical intervention after decompressive craniectomy in patients with malignant middle cerebral artery (MCA) infarction. In addition to surgery-related short-term complications, aseptic resorption of the reimplanted bone flap is a possible long-term problem which has not yet been sufficiently elucidated in these patients.

Methods

A total of 109 patients who had undergone decompressive hemicraniectomy for malignant MCA infarction in our institution between September 1994 and December 2011 were included in the study. Clinical and radiological findings were retrieved retrospectively. Aseptic bone necrosis was classified into two categories based on computer tomographic features.

Results

A total of 76 patients received their own cryoconserved bone flap (mean age 54.34 ± 10.73 years; 49 males). The overall short-term complication rate was 9.2 %. Bone flap necrosis occurred in 26 patients (22.8 %) with 7 flaps showing signs of surgically relevant type II necrosis after a median time of 14 months (interquartile range [IQR] 4–22).

Conclusions

There is a noticeable complication rate in patients undergoing bone flap reinsertion after hemicraniectomy due to malignant MCA infarction. Aseptic bone necrosis represents a significant complication during long-term follow-up. The pathophysiological mechanisms remain unclear and more efforts should be undertaken to understand and possibly prevent this complication in these patients.  相似文献   
996.
Traumatic brain injury (TBI) is a major cause of death and disability worldwide. In large part critical care for TBI is focused on the identification and management of secondary brain injury. This requires effective neuromonitoring that traditionally has centered on intracranial pressure (ICP). The purpose of this paper is to review the fundamental literature relative to the clinical application of ICP monitoring in TBI critical care and to provide recommendations on how the technique maybe applied to help patient management and enhance outcome. A PubMed search between 1980 and September 2013 identified 2,253 articles; 244 of which were reviewed in detail to prepare this report and the evidentiary tables. Several important concepts emerge from this review. ICP monitoring is safe and is best performed using a parenchymal monitor or ventricular catheter. While the indications for ICP monitoring are well established, there remains great variability in its use. Increased ICP, particularly the pattern of the increase and ICP refractory to treatment is associated with increased mortality. Class I evidence is lacking on how monitoring and management of ICP influences outcome. However, a large body of observational data suggests that ICP management has the potential to influence outcome, particularly when care is targeted and individualized and supplemented with data from other monitors including the clinical examination and imaging.  相似文献   
997.

Background

To determine neurologic outcome in patients with out-of-hospital cardiac arrest (OHCA) and treatment with mild therapeutic hypothermia (MTH).

Methods

Seventy-three consecutive OHCA patients treated with MTH were retrospectively analyzed. Serum neuron-specific enolase (NSE) was measured 24, 48, and 72 h after admission. In patients with no motor response 48 h after termination of analgosedation (n = 40), clinical neurological examination and evoked potentials (EPs) were determined. Neurological outcome was assessed after 2 months based on the cerebral performance categories (CPC), and categorized as good (CPC 1–3) or poor (CPC 4 and 5).

Results

Forty-three patients had a CPC score of 1–3 and 30 patients had a CPC 4–5. The best predictive value for poor neurologic outcome was an increase of NSE by ≥4.3 ng/mL between day 1 and day 2 (sensitivity 80 %, specificity 100 %, positive predictive value (PPV) 100 %, negative predictive value 86 %). Absolute NSE values were less reliable in the prediction of poor outcome with the highest sensitivity (88 %) and specificity (95 %) if values reached ≥36.3 ng/mL on day 3. Somatosensory EPs (SSEPs) showed a specificity of 100 % and PPV of 100 %; however, sensitivity for evoked potentials was low (29 %). Intriguingly, two initially comatose patients with excessive NSE values (24 h NSE: 101 and 256 ng/mL, and 48 h NSE: 93 and 110 ng/mL, respectively) had physiological SSEPs and regained a CPC score of 1.

Conclusion

In patients treated with MTH after OHCA changes in NSE are more suitable than its absolute serum levels for the prediction of poor neurologic outcome. Since unequivocal prediction of poor neurologic outcome is of utmost importance in these patients the decision to limit therapy must be based on several prediction tools with the highest PPV and specificity including SSEPs.  相似文献   
998.
Objective.To evaluate the association between coffee and caffeine consumption and suicide risk in three large-scale cohorts of US men and women. Methods. We accessed data of 43,599 men enrolled in the Health Professionals Follow-up Study (HPFS, 1988–2008), 73,820 women in the Nurses’ Health Study (NHS, 1992–2008), and 91,005 women in the NHS II (1993–2007). Consumption of caffeine, coffee, and decaffeinated coffee, was assessed every 4 years by validated food-frequency questionnaires. Deaths from suicide were determined by physician review of death certificates. Multivariate adjusted relative risks (RRs) were estimated with Cox proportional hazard models. Cohort specific RRs were pooled using random-effect models. Results. We documented 277 deaths from suicide. Compared to those consuming ≤ 1 cup/week of caffeinated coffee (< 8 oz/237 ml), the pooled multivariate RR (95% confidence interval [CI]) of suicide was 0.55 (0.38–0.78) for those consuming 2–3 cups/day and 0.47 (0.27–0.81) for those consuming ≥ 4 cups/day (P trend < 0.001). The pooled multivariate RR (95% CI) for suicide was 0.75 (0.63–0.90) for each increment of 2 cups/day of caffeinated coffee and 0.77 (0.63–0.93) for each increment of 300 mg/day of caffeine. Conclusions. These results from three large cohorts support an association between caffeine consumption and lower risk of suicide.  相似文献   
999.

Background

Chronic endoplasmic reticulum (ER) stress contributes to the apoptotic cell death in the myocardium, thereby playing a critical role in the development of cardiomyopathy. ER stress has been reported to be induced after high-fat diet feeding in mice and also after saturated fatty acid treatment in vitro. Therefore, since several studies have shown that peroxisome proliferator-activated receptor (PPAR)β/δ inhibits ER stress, the main goal of this study consisted in investigating whether activation of this nuclear receptor was able to prevent lipid-induced ER stress in cardiac cells.

Methods and results

Wild-type and transgenic mice with reduced PPARβ/δ expression were fed a standard diet or a high-fat diet for two months. For in vitro studies, a cardiomyocyte cell line of human origin, AC16, was treated with palmitate and the PPARβ/δ agonist GW501516. Our results demonstrate that palmitate induced ER stress in AC16 cells, a fact which was prevented after PPARβ/δ activation with GW501516. Interestingly, the effect of GW501516 on ER stress occurred in an AMPK-independent manner. The most striking result of this study is that GW501516 treatment also upregulated the protein levels of beclin 1 and LC3II, two well-known markers of autophagy. In accordance with this, feeding on a high-fat diet or suppression of PPARβ/δ in knockout mice induced ER stress in the heart. Moreover, PPARβ/δ knockout mice also displayed a reduction in autophagic markers.

Conclusion

Our data indicate that PPARβ/δ activation might be useful to prevent the harmful effects of ER stress induced by saturated fatty acids in the heart by inducing autophagy.  相似文献   
1000.
Phosphatidylserine-dependent antiprothrombin antibodies (aPS/PT) were strongly correlated with the presence of lupus anticoagulant showing a high specificity for the diagnosis of antiphospholipid syndrome. However, the main criticism for the clinical applicability of aPS/PT testing is the lack of reproducibility of the results among laboratories. In this study, we measured IgG and IgM aPS/PT using our original in-house enzyme-linked immunosorbent assays (ELISA) and commercial ELISA kits to assess the assay performance and to evaluate the accuracy of aPS/PT results. The study included 111 plasma samples collected from patients and stored at our laboratory for aPS/PT assessment. Sixty-one samples were tested for IgG aPS/PT using two assays: (1) aPS/PT in-house ELISA and (2) QUANTA Lite? aPS/PT IgG ELISA kit (INOVA Diagnostics, Inc., USA). Fifty samples were evaluated for IgM aPS/PT using two assays: (1) aPS/PT in-house ELISA and (2) QUANTA Lite? aPS/PT IgM ELISA kit (INOVA Diagnostics). Ninety-eight percent of samples yielded concordant results for IgG aPS/PT and 82 % for IgM aPS/PT. There was an excellent agreement between the IgG aPS/PT assays (Cohen κ = 0.962) and moderate agreement between the IgM aPS/PT assays (κ = 0.597). Statistically significant correlations in the aPS/PT results were obtained from both IgG and IgM aPS/PT assays (r = 0.749, r = 0.622, p < 0.001, respectively). In conclusion, IgG and IgM detection by ELISA is accurate. The performance of aPS/PT is reliable, and concordant results can be obtained using different ELISA methods.  相似文献   
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