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   2606篇
  免费   157篇
  国内免费   9篇
耳鼻咽喉   22篇
儿科学   100篇
妇产科学   72篇
基础医学   471篇
口腔科学   52篇
临床医学   260篇
内科学   529篇
皮肤病学   35篇
神经病学   180篇
特种医学   82篇
外科学   333篇
综合类   30篇
预防医学   192篇
眼科学   63篇
药学   218篇
中国医学   5篇
肿瘤学   128篇
  2023年   13篇
  2022年   32篇
  2021年   78篇
  2020年   37篇
  2019年   60篇
  2018年   65篇
  2017年   53篇
  2016年   51篇
  2015年   72篇
  2014年   69篇
  2013年   106篇
  2012年   177篇
  2011年   148篇
  2010年   99篇
  2009年   94篇
  2008年   169篇
  2007年   165篇
  2006年   176篇
  2005年   150篇
  2004年   160篇
  2003年   142篇
  2002年   151篇
  2001年   25篇
  2000年   11篇
  1999年   22篇
  1998年   31篇
  1997年   17篇
  1996年   29篇
  1995年   16篇
  1994年   18篇
  1993年   16篇
  1992年   9篇
  1991年   15篇
  1990年   11篇
  1989年   8篇
  1987年   13篇
  1986年   9篇
  1985年   8篇
  1984年   12篇
  1983年   7篇
  1982年   7篇
  1981年   9篇
  1980年   12篇
  1937年   9篇
  1929年   7篇
  1928年   11篇
  1926年   8篇
  1925年   7篇
  1923年   6篇
  1922年   6篇
排序方式: 共有2772条查询结果,搜索用时 15 毫秒
1.
This meta-analysis focuses on the accuracy of upgrading to clinically significant prostate cancer (PCa) by multiparametric magnetic resonance imaging-targeted biopsy (MRI-TB) versus systematic biopsy (SB). We searched the Medline, Embase, Cochrane Central Register of Controlled Trials, Web of Science, Scopus, and Literatura Latino Americana em Ciências da Saúde databases through January 2020 for comparative, retrospective/prospective, paired-cohort, and randomized clinical trials with paired comparisons. The population consisted of patients with low-risk PCa in active surveillance with at least 1 index lesion on imaging. We evaluated the quality of evidence by using the Quality Assessment of Diagnostic Accuracy Studies-2 score. Group comparisons considered the differences between the area under the curve summary receiver operating characteristic curve in a 2-tailed method. We also compared the positive predictive value of the best single method (MRI-TB or SB) and the referral study test (combined biopsy, a combination of MRI-TB and SB). The meta-analysis included 6 studies enrolling 741 patients. The pooled sensitivity for the 2 groups was 0.79 (95% confidence interval, 0.74-0.83; I2 = 75%) and 0.67 (95% confidence interval, 0.63-0.74; I2 = 55.4%), respectively. The area under the curve for the MRI-TB and SB groups were 0.99 and 0.92 (P < .001), respectively. The positive predictive value for the MRI-TB and combined biopsy groups were similar. The accumulated evidence suggests better results for MRI-TB compared with SB. Therefore, use of MRI-TB alone may be preferable in patients in active surveillance harboring low-risk PCa.  相似文献   
2.
3.
4.
5.
INTRODUCTION: One-third of children with epilepsy are classified as having a cryptogenic localization related epilepsy (CLRE). In cohort studies CLRE is often grouped together with either symptomatic localization related epilepsy (SLRE) or idiopathic generalized epilepsy (IGE). Therefore, this categorization is not specific enough and will not lead to prognostic or treatment information. We objectified the classification differences between these categories. METHODS: A total of 114 children admitted to our epilepsy centre underwent a standardized clinical analysis, which yielded age at onset, duration of the epilepsy, seizure frequency, seizure type, percentage of interictal epileptiform activity on EEG (IEA), type of treatment, and full scale IQ. These variables are regarded the characteristics of the epilepsy, and used in a discriminant function analysis. RESULTS: IEA was found to be the only variable to distinguish between groups of epilepsy. SLRE could easily be distinguished significantly from IGE and CLRE, while the latter two did not differ significantly. Discriminant function analysis combined the variables into two functions, applicable to classify the children. By applying this statistical analysis method, the groups clinically classified as SLRE and IGE were mostly classified as SLRE (71.4%) and IGE (57.9%). However, CLRE appeared difficult to classify (49.2%), and most children were classified as either SLRE (19%) or IGE (31.7%). CONCLUSION: The current opinion that CLRE is 'probably symptomatic' cannot be confirmed in all cases in this study. It is most likely that the current CLRE population consists of both children with eventually SLRE, as well as yet to be described syndromes to be classified as idiopathic epilepsies. We emphasize the need for separate studies regarding children with 'probably symptomatic' (cryptogenic) localization related epilepsy, as this will maximally help children, caretakers and treating physicians to achieve the best possible outcome.  相似文献   
6.
7.
Diarrhea is the most frequently reported adverse event in patients treated with mycophenolate mofetil. Twenty-six renal transplant patients on a mycophenolate mofetil-based immunosuppressive regime with persistent afebrile diarrhea were examined. Diarrhea caused a significant rise in FK-506 trough levels despite intake of stable doses, necessitating FK-506 dose reductions of 30% to obtain pre-diarrhea trough levels. In contrast, trough levels of cyclosporine A remained stable without dose adjustments. This suggests that absorption and/or metabolism is differentially altered for FK506 compared with cyclosporine A in patients with diarrhea. In nine patients mycophenolate mofetil was reduced or stopped because of persistent diarrhea without identifiable cause. This resulted in end-stage renal disease because of chronic rejection in two patients, and in acute rejection in two patients, all taking FK506 and steroids. Therefore, dose adjustments of FK506 in patients with diarrhea must be carefully monitored, especially when doses of mycophenolate mofetil are also reduced.  相似文献   
8.
9.
The role of Ca2+ in the regulation of antidiuretic hormone(ADH)-induced water permeability of the apical membrane of the toad urinary bladder was examined. The effects of modifying Ca2+ entry through the apical membrane of toad urinary bladders on the hydroosmotic water flow H2O) and short circuit current (I sc) were measured. In most experiments the bladders were treated with small amounts of Ag+ (10–7 mol/l) on the apical side. This treatment was used because previous experiments indicate that it markedly increases alkali-earth cation fluxes through an amiloride-insensitive cation channel in the apical membrane of the urinary bladder. Moreover, when Ca2+ is the major cation in the apical solution of these Ag+-treated bladders, I sc is mostly due to Ca2+ entry through the apical membrane. Ag+ increased I sc and simultaneously inhibited H2O in bladders perfused with Ca2+ solutions on the apical side. Addition of La3+ to the apical solution reversed the stimulation of I sc and the inhibition of H2O produced by Ag+. When bladders were perfused with Ca2+-free solutions on the apical side, addition of Ag+ did not inhibit H2O while the stimulation of cation movements through the amiloride-insensitive cation channel persisted. In bladders perfused with apical Ca2+ solutions and treated with chlorophenyl thio-cyclic adenosine monophosphate (ClPheS-cAMP) the addition of Ag+ did not inhibit H2O while it still increased I sc. Finally, addition of Ca2+ to the apical solution of bladders not treated with Ag+ reduced H2O. These results taken together with other findings in the literature suggest: (1) Ca2+ entry through the Ag+-treated amiloride-insensitive cation channel of the apical membrane inhibits H2O; (2) the effects of Ca2+ entry are at a regulatory site that precedes the interaction of cAMP with the water channels; (3) it is also possible that Ca2+ entry through the unmodified amiloride-insensitive cation channel may have some inhibitory effect on H2O.  相似文献   
10.
Zn(2+) (1-1,000 microM) applied to the apical side of polarized A6 epithelia inhibits Na(+) transport, as reflected in short-circuit current and conductance measurements. The Menten equilibrium constant for Zn(2+) inhibition was 45 microM. Varying the apical Na(+) concentration, we determined the equilibrium constant of the short-circuit current saturation (34.9 mM) and showed that Zn(2+) inhibition is non-competitive. A similar effect was observed in Xenopus oocytes expressing alphabetagammarENaC (alpha-, beta-, and gamma-subunits of the rat epithelial Na(+) channel) in the concentration range of 1-10 microM Zn(2+), while at 100 microM Zn(2+) exerted a stimulatory effect. The analysis of the voltage dependence of the steady-state conductance revealed that the inhibitory effect of Zn(2+) was due mainly to a direct pore block and not to a change in surface potential. The equivalent gating charge of ENaC, emerging from these data, was 0.79 elementary charges, and was not influenced by Zn(2+). The stimulatory effect of high Zn(2+) concentrations could be reproduced by intra-oocyte injection of Zn(2+) (approximately 10 microM), which had no direct effect on the amiloride-sensitive conductance, but switched the effect of extracellular Zn(2+) from inhibition to activation.  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