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   56181篇
  免费   3103篇
  国内免费   598篇
耳鼻咽喉   985篇
儿科学   630篇
妇产科学   825篇
基础医学   9759篇
口腔科学   1352篇
临床医学   4889篇
内科学   10545篇
皮肤病学   1873篇
神经病学   3987篇
特种医学   2971篇
外科学   7471篇
综合类   213篇
现状与发展   1篇
一般理论   17篇
预防医学   2716篇
眼科学   1233篇
药学   4987篇
中国医学   625篇
肿瘤学   4803篇
  2023年   428篇
  2022年   1330篇
  2021年   2061篇
  2020年   985篇
  2019年   1290篇
  2018年   1665篇
  2017年   1243篇
  2016年   1757篇
  2015年   2559篇
  2014年   3061篇
  2013年   3489篇
  2012年   5316篇
  2011年   4809篇
  2010年   2805篇
  2009年   2362篇
  2008年   3416篇
  2007年   3094篇
  2006年   2653篇
  2005年   2352篇
  2004年   2025篇
  2003年   1692篇
  2002年   1435篇
  2001年   1363篇
  2000年   1262篇
  1999年   906篇
  1998年   362篇
  1997年   250篇
  1996年   208篇
  1995年   176篇
  1994年   148篇
  1993年   132篇
  1992年   332篇
  1991年   316篇
  1990年   280篇
  1989年   258篇
  1988年   247篇
  1987年   248篇
  1986年   177篇
  1985年   165篇
  1984年   119篇
  1983年   111篇
  1982年   55篇
  1981年   58篇
  1979年   81篇
  1978年   68篇
  1975年   50篇
  1974年   60篇
  1973年   51篇
  1972年   50篇
  1970年   49篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The retrosplenial cortex is a cytoarchitecturally distinct brain structure located in the posterior cingulate gyrus and bordering the splenium, precuneus, and calcarine fissure. Functional imaging suggests that the retrosplenium is involved in memory, visuospatial processing, proprioception, and emotion.We report on a patient who developed reversible verbal and visual memory deficits following a stroke. Neuropsychological testing revealed both anterograde and retrograde memory deficits in verbal and visual modalities. Brain diffusion-weighted and T2-weighted magnetic resonance imaging (MRI) demonstrated an acute infarction of the left retrosplenium.  相似文献   
102.
103.
The stereoselective metabolism of lansoprazole enantiomers was evaluated by incubation of human liver microsomes and cDNA-expressed cytochrome p450 (p450) enzymes to understand and predict their stereoselective disposition in humans in vivo. The intrinsic clearances (Clint) of the formation of both hydroxy and sulfone metabolites from S-lansoprazole were 4.9- and 2.4-fold higher than those from the R-form, respectively. The sums of formation Clint of both metabolites were 13.5 and 57.3 microl/min/mg protein for R- and S-lansoprazole, respectively, suggesting that S-lansoprazole would be cleared more rapidly than the R-form. The p450 isoform selective inhibition study in liver microsomes, and the incubation study of cDNA-expressed enzymes, demonstrated that the stereoselective sulfoxidation is mediated by CYP3A4 and that the hydroxylation is mediated by CYP2C9 and CYP3A4 as well as by CYP2C19. Total Clint values of hydroxy and sulfone metabolite formation catalyzed by all these p450 enzymes were consistently higher for S-lansoprazole than for the R-form. The CYP3A4 produced the greatest difference of Clint between S- and R-enantiomers, mainly due to a difference of sulfoxidation metabolism (Clint 76.5 versus 10.8 microl/min/nmol of p450, respectively), whereas CYP2C19-catalyzed hydroxylation resulted in a minor difference of Clint between S- and R-enantiomers (179.6 versus 143.3 microl/min/nmol of p450, respectively). However, the affinity of CYP2C19 on hydroxylation was 5.7-fold higher for S-enantiomer than for the R-form (Km 2.3 versus 13.1 microM), suggesting that the role of CYP2C19 on stereoselective hydroxylation would be more prominent at concentrations around the usual therapeutic level. These findings suggest that both CYP2C19 and CYP3A4 are major enzymes contributing to the stereoselective disposition of lansoprazole, but stereoselective hydroxylation of lansoprazole enantiomers is mainly influenced by CYP2C19, especially at the usual therapeutic doses.  相似文献   
104.
Poly(arylene-1,2,4-oxadiazole)s (PAOs) bearing flexible, linear side chains, 3a - c , were prepared by solution cyclodehydration of their precursors, poly(arylene acyloylamide oxime)s (PAAs), 2a - c , which were synthesized by solution polycondensation of 2,5-bis(n-alkoxymethyl)-terephthaldiamide oximes (DIS-TADO), 1a - c , with terephthaloyl dichloride (TPC). The length of the n-alkoxy group was varied from methoxy via butoxy to octyloxy. The reduction of the phase transition temperatures and the enhancement of the solubilities of 3a - c were greatly affected by the length of the side chains. PAOs with longer side chains, 3b and 3c , are nematic type liquid-crystalline polymers.  相似文献   
105.
Toluene diisocyanate (TDI), a low molecular weight reactive chemical, is known to be a main cause of occupational asthma (OA) in Korea. Although it is thought that inhaled TDI may act as a hapten, the precise mechanisms of TDI-induced OA are unknown. In this study, TDI-human serum albumin (HSA) conjugates (5, 10, 20 and 30 min) were prepared in the range of 1.5 to 5.0 TDI mole/HSA mole. Specific binding of serum IgE to TDI-HSA (30 min) was observed using IgE ELISA as well as ELISA inhibition assay. Around 40% of TDI-induced OA patients were positive for serum specific IgE by ELISA. Degrees of serum IgE binding were different depending on which TDI-HSA conjugate was used as an antigen. Moreover, binding patterns were different depending on the individuals. Interestingly, higher binding of IgE to TDI-HSA (5 min) than to TDI-HSA (30 min) which was more highly substituted was observed in some patients. Probably new antigenic epitopes on carrier proteins were targets of the specific IgE. The results of this study indicated that IgE responses to TDI-HSA conjugates were heterogeneous in TDI-induced OA patients and self-proteins modified by reactive chemicals can become a major target antigen of IgE in certain cases.  相似文献   
106.
Mortality among ferrous foundry workers   总被引:8,自引:0,他引:8  
Mortality analyses were carried out for 278 male hourly workers who were employed for at least 10 years at a gray iron foundry and who died between January 1, 1970 and December 31, 1981. Statistically significant excess proportional mortality due to non-malignant respiratory disease (SPMR = 177), lung cancer (SPMR = 148), and leukemia (SPMR = 284) was found among the 221 white males. Among nonwhite males there was a significant excess in proportional mortality due to circulatory diseases (SPMR = 143). White males in the Finishing classification experienced a significant excess of proportional mortality due to nonmalignant respiratory disease (SPMR = 279) and lung cancer (SPMR = 179). White males in the Core Room classification experienced an excess of proportional mortality due to nonmalignant respiratory disease (SPMR = 321). Case-control studies demonstrated a significant association between nonmalignant respiratory disease and the Finishing classification after controlling for the effects of age, prior occupations in coal mining or foundries, and smoking. A positive but nonsignificant association between lung cancer and Finishing was also found after controlling for age, prior work history, and smoking in case control studies.  相似文献   
107.
OBJECTIVE: To evaluate the ultrasonographic measurement of shoulder subluxation in patients with post-stroke hemiplegia. DESIGN: Prospective, single blind study. PATIENTS: A total of 41 patients with post-stroke hemiplegia were included (24 men and 17 women, mean age 56 years (standard deviation 11), age range 34-78 years). METHODS: Clinical evaluation of the affected shoulder was assessed using the Motricity Index scores and the Modified Ashworth Scale. Two ultrasonographic measurements were taken to check intra-rater reliability. The shoulder subluxation ratio was determined as the ratio of the radiographic vertical and horizontal distance, and the ultrasonographic lateral and anterior distances in the affected shoulder divided by that in the unaffected shoulder. RESULTS: Intraclass correlation coefficients of the repeated ultrasonographic lateral/anterior distance measurements in the unaffected and affected shoulders were 0.979/0.969 and 0.950/0.947, respectively. Ultrasonographic lateral/anterior distance ratios were negatively correlated with Motricity Index scores of the affected shoulder abduction (r = -0.490, p < 0.001/ r = -0.671, p < 0.001). Ultrasonographic anterior distance ratio was negatively correlated with Modified Ashworth Scale score of the affected shoulder (r = -0.374, p < 0.05). However, there was no correlation between radiographic distance ratios and clinical evaluation scores. CONCLUSION: We strongly recommend ultrasonography as a diagnostic tool to measure the degree of shoulder subluxation in patients with post-stroke hemiplegia.  相似文献   
108.
109.
We studied the effect of the 5-HT1A receptor antagonist, pindolol, on the prolactin (PRL) response to the 5-HT releasing agent,d-fenfluramine (d-FEN), in ten healthy male volunteers. Pindolol pretreatment lowered baseline PRL levels but, when this effect was taken into account, did not significantly attenuate the PRL response tod-FEN. Within the limitations that attend the use of pindolol as a 5-HT1A receptor antagonist, the data suggest that although 5-HT1A receptors may play a role in the tonic release of PRL, they are not involved in the release of PRL produced byd-FEN. We propose that the PRL response tod-FEN may involve selective activation of postsynaptic 5-HT2 receptors.  相似文献   
110.
BACKGROUND: Previous studies reported that early diagnosis and avoidance therapy are the most important factors for prevention of permanent lung impairment; however, few studies have evaluated the long-term prognosis of reactive dye-induced occupational asthma (RD-OA). OBJECTIVE: To evaluate the long-term outcomes of RD-OA. METHODS: Methacholine airway hyperresponsiveness (AHR) and lung functions were evaluated and compared in 26 patients with RD-OA at the time of diagnosis and after complete avoidance of the causative agents. Patients with continued (n = 13) or remitted (n = 6) AHR were further monitored for up to a mean +/- SD of 8.7 +/- 1.8 years. RESULTS: The AHR resolved in 10 (38%) of 26 patients a mean +/- SD of 2.2 +/- 1.3 years after complete avoidance of RDs; however, prebronchodilator forced expiratory volume in 1 second (FEV1) values were not different. Levels of IgE specific to the RD-human serum albumin complex were markedly decreased at first follow-up in 5 RD-atopic patients from whom paired serum samples were compared (P = .02). The AHR disappeared in an additional 5 patients and improved in 4 by the second follow-up. The FEV1 values also improved compared with diagnosis and first follow-up levels. Favorable prognosis was associated with early diagnosis of RD-OA and complete avoidance of the causative agent. No association was found with smoking history, latent periods, the presence of RD specific IgE, baseline provocation concentration that caused a decrease in FEV1 of 20%, or FEV1. CONCLUSIONS: Early diagnosis and avoidance therapy are the most important prognostic factors in RD-OA. The AHR and lung function of patients with RD-OA can sometimes be recovered steadily and slowly through avoidance measures.  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