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   3208篇
  免费   208篇
  国内免费   11篇
耳鼻咽喉   34篇
儿科学   65篇
妇产科学   70篇
基础医学   798篇
口腔科学   39篇
临床医学   261篇
内科学   786篇
皮肤病学   77篇
神经病学   271篇
特种医学   109篇
外科学   299篇
综合类   36篇
一般理论   2篇
预防医学   206篇
眼科学   60篇
药学   215篇
中国医学   2篇
肿瘤学   97篇
  2023年   25篇
  2022年   33篇
  2021年   80篇
  2020年   28篇
  2019年   59篇
  2018年   66篇
  2017年   55篇
  2016年   36篇
  2015年   57篇
  2014年   67篇
  2013年   104篇
  2012年   136篇
  2011年   135篇
  2010年   88篇
  2009年   64篇
  2008年   115篇
  2007年   138篇
  2006年   137篇
  2005年   111篇
  2004年   107篇
  2003年   110篇
  2002年   97篇
  2001年   25篇
  2000年   39篇
  1999年   31篇
  1998年   28篇
  1997年   21篇
  1992年   21篇
  1989年   21篇
  1987年   22篇
  1984年   26篇
  1982年   28篇
  1978年   23篇
  1975年   18篇
  1974年   22篇
  1973年   19篇
  1972年   20篇
  1937年   16篇
  1934年   35篇
  1933年   40篇
  1932年   23篇
  1931年   44篇
  1930年   29篇
  1929年   19篇
  1928年   40篇
  1926年   22篇
  1925年   16篇
  1924年   20篇
  1923年   26篇
  1922年   21篇
排序方式: 共有3427条查询结果,搜索用时 15 毫秒
91.
BackgroundFOLFOX plus bevacizumab is a standard of care (SOC) for first-line treatment of microsatellite-stable metastatic colorectal cancer (MSS mCRC). This study randomized patients to SOC or SOC plus avelumab (anti-PD-L1) plus CEA-targeted vaccine.MethodsPatients with untreated MSS mCRC enrolled to a lead-in arm assessing safety of SOC + immuno-oncology agents (IO). Next, patients were randomized to SOC or SOC + IO. The primary endpoint was progression-free survival (PFS). Multiple immune parameters were analyzed.ResultsSix patients enrolled to safety lead-in, 10 randomized to SOC, and 10 to SOC + IO. There was no difference in median PFS comparing SOC versus SOC + IO (8.8 months (95% CI: 3.3-17.0 months) versus 10.1 months (95% CI: 3.6-16.1 months), respectively; hazard ratio 1.061 [P = .91; 95% CI: 0.380-2.966]). The objective response rate was 50% in both arms. Of patients analyzed, most (8/11) who received SOC + IO developed multifunctional CD4+/CD8+ T-cell responses to cascade antigens MUC1 and/or brachyury, compared to 1/8 who received SOC alone (P = .020). We detected post-treatment changes in immune parameters that were distinct to the SOC and SOC + IO treatment arms. Accrual closed after an unplanned analysis predicted a low likelihood of meeting the primary endpoint.ConclusionsSOC + IO generated multifunctional MUC1- and brachyury-specific CD4+/CD8+ T cells despite concurrent chemotherapy. Although a tumor-directed immune response is necessary for T-cell–mediated antitumor activity, it was not sufficient to improve PFS. Adding agents that increase the number and function of effector cells may be required for clinical benefit.  相似文献   
92.
Currently there are several compounds used as drugs or studied as new chemical entities, which have an electron withdrawing group connected to a vinylic double bond in a phenolic or catecholic core structure. These compounds share a common feature – current computational methods utilizing the Hammett type equation for the prediction of ionisation constants fail to give accurate prediction of pKa's for compounds containing the vinylic moiety. The hypothesis was that the effect of electron-withdrawing substituents on the pKa of p-vinyl phenols is due to the delocalized electronic structure of these compounds. Thus, this effect should be additive for multiple substituents attached to the vinylic double bond and quantifiable by LFER-based methods. The aim of this study was to produce an improved equation with a reduced tendency to underestimate the effect of the double bond on the ionisation of the phenolic hydroxyl. To this end a set of 19 para-substituted vinyl phenols was used. The ionisation constants were measured potentiometrically, and a training set of 10 compounds was selected to build a regression model (r2 = 0.987 and S.E. = 0.09). The average error with an external test set of six compounds was 0.19 for our model and 1.27 for the ACD-labs 7.0. Thus, we have been able to significantly improve the existing model for prediction of the ionisation constants of substituted p-vinyl phenols.  相似文献   
93.
ObjectiveMultiple studies have identified single-nucleotide polymorphisms (SNPs) that are associated with coronary heart disease (CHD). We examined whether SNPs selected based on predefined criteria will improve CHD risk prediction when added to traditional risk factors (TRFs).MethodsSNPs were selected from the literature based on association with CHD, lack of association with a known CHD risk factor, and successful replication. A genetic risk score (GRS) was constructed based on these SNPs. Cox proportional hazards model was used to calculate CHD risk based on the Atherosclerosis Risk in Communities (ARIC) and Framingham CHD risk scores with and without the GRS.ResultsThe GRS was associated with risk for CHD (hazard ratio [HR] = 1.10; 95% confidence interval [CI]: 1.07–1.13). Addition of the GRS to the ARIC risk score significantly improved discrimination, reclassification, and calibration beyond that afforded by TRFs alone in non-Hispanic whites in the ARIC study. The area under the receiver operating characteristic curve (AUC) increased from 0.742 to 0.749 (Δ = 0.007; 95% CI, 0.004–0.013), and the net reclassification index (NRI) was 6.3%. Although the risk estimates for CHD in the Framingham Offspring (HR = 1.12; 95% CI: 1.10–1.14) and Rotterdam (HR = 1.08; 95% CI: 1.02–1.14) Studies were significantly improved by adding the GRS to TRFs, improvements in AUC and NRI were modest.ConclusionAddition of a GRS based on direct associations with CHD to TRFs significantly improved discrimination and reclassification in white participants of the ARIC Study, with no significant improvement in the Rotterdam and Framingham Offspring Studies.  相似文献   
94.
95.
In hypertensive patients without prevalent cardiovascular disease, enhanced left atrial systolic force is associated with left ventricular hypertrophy and increased preload. It also predicts cardiovascular events in a population with high prevalence of obesity. Relations between left atrial systolic force and left ventricular geometry and function have not been investigated in high-risk hypertrophic hypertensive patients. Participants in the Losartan Intervention For Endpoint reduction in hypertension echocardiography substudy without prevalent cardiovascular disease or atrial fibrillation (n = 567) underwent standard Doppler echocardiography. Left atrial systolic force was obtained from the mitral orifice area and Doppler mitral peak A velocity. Patients were divided into groups with normal or increased left atrial systolic force (>14.33 kdyn). Left atrial systolic force was high in 297 patients (52.3%), who were older and had higher body mass index and heart rate (all P < 0.01) but similar systolic and diastolic blood pressure, in comparison with patients with normal left atrial systolic force. After controlling for confounders, increased left atrial systolic force was associated with larger left ventricular diameter and higher left ventricular mass index (both P < 0.01). Prevalence of left ventricular hypertrophy was greater (84 vs. 64%; P < 0.001). Participants with increased left atrial systolic force exhibited normal ejection fraction; higher stroke volume, cardiac output, transmitral peak E velocities and peak A velocities; and lower E/A ratio (all P < 0.01). Enhanced left atrial systolic force identifies hypertensive patients with greater left ventricular mass and prevalence of left ventricular hypertrophy, but normal left ventricular chamber systolic function with increased transmitral flow gradient occurring during early filling, consistent with increased preload.  相似文献   
96.
CXCL12 and VCAM1 retain hematopoietic stem cells (HSCs) in the BM, but the factors mediating HSC egress from the BM to the blood are not known. The sphingosine-1-phosphate receptor 1 (S1P(1)) is expressed on HSCs, and S1P facilitates the egress of committed hematopoietic progenitors from the BM into the blood. In the present study, we show that both the S1P gradient between the BM and the blood and the expression of S1P(1) are essential for optimal HSC mobilization by CXCR4 antagonists, including AMD3100, and for the trafficking of HSCs during steady-state hematopoiesis. We also demonstrate that the S1P(1) agonist SEW2871 increases AMD3100-induced HSC and progenitor cell mobilization. These results suggest that the combination of a CXCR4 antagonist and a S1P(1) agonist may prove to be sufficient for mobilizing HSCs in normal donors for transplantation purposes, potentially providing a single mobilization procedure and eliminating the need to expose normal donors to G-CSF with its associated side effects.  相似文献   
97.
Endotoxin or lipopolysaccharide isolated from Brucella abortus (strain 456) produced a typical endotoxin-type interferon response in mice with peak levels of the inhibitor occurring 2 h after intravenous injection of the stimuli. Brucella lipopolysaccharide was a much less effective interferon stimulus than the lipopolysaccharide isolated from Salmonella typhimurium (strain LT-2).  相似文献   
98.
BackgroundCholesterol 24S-hydroxylase (CYP46) catalyzes the conversion of cholesterol to 24S-hydroxycholesterol, the primary cerebral cholesterol elimination product. Only few gene variations in CYP46 gene (CYP46A1) have been investigated for their relevance as genetic risk factors of Alzheimer's disease (AD) and results are contradictory.MethodsWe performed a gene variability screening in CYP46A1 and investigated the effect of gene variants on the risk of AD and on CSF levels of cholesterol and 24S-hydroxycholesterol.ResultsTwo of the identified 16 SNPs in CYP46A1 influenced AD risk in our study (rs7157609: p = 0.016; rs4900442: p = 0.019). The interaction term of both SNPs was also associated with an increased risk of AD (p = 0.006). Haplotypes including both SNPs were calculated and haplotype G–C was identified to influence the risk of AD (p = 0.005). AD patients and non-demented controls, who were carriers of the G–C haplotype, presented with reduced CSF levels of 24S-hydroxycholesterol (p = 0.001) and cholesterol (p < 0.001).ConclusionOur results suggest that CYP46A1 gene variations might act as risk factor for AD via an influence on brain cholesterol metabolism.  相似文献   
99.
In five patients with severe essential hypertension, placebo was substituted after 24 to 48 months of treatment with clonidine and a diuretic. In the present study, four of the patients developed a marked blood pressure rise following withdrawal of clonidine which was rapidly reversed by intravenous administration of propranolol 0.2 mg. per kilogram of body weight and phentolamine 20 to 30 mg. The fifth patient was pretreated with reserpine 2.0 mg. intramuscularly for three days prior to withdrawal of clonidine, and the blood pressure rise which he experienced was far less impressive. All patients experienced similar “withdrawal” symptoms, consisting of headaches, insomnia, restlessness, tremor, and nausea.Catecholamines were determined in arterial blood and urine, before and during the overshoot. They revealed a marked increase, particularly in the urine samples, consistent with the appearance of a hyperadrenergic state.  相似文献   
100.
Mucinous Cystadenoma: Pitfalls of Differential Diagnosis   总被引:1,自引:0,他引:1  
Cystic neoplasms of the pancreas often are difficult to differentiate from pseudocysts. It has been proposed that a history of clinical pancreatitis, elevated serum pancreatic enzymes, elevated cyst fluid amylase, and a communication with the pancreatic duct suggest the diagnosis of a pseudocyst. We report the case of a young woman who presented with a cystic mass in the pancreas and was thought to have a pseudocyst because of the above; at surgery, a mucinous cystadenoma was documented. The pitfalls of differentiating neoplastic cysts of the pancreas from pseudocysts are discussed.  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