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   5469篇
  免费   326篇
  国内免费   46篇
耳鼻咽喉   52篇
儿科学   150篇
妇产科学   152篇
基础医学   756篇
口腔科学   91篇
临床医学   427篇
内科学   1222篇
皮肤病学   146篇
神经病学   617篇
特种医学   100篇
外科学   464篇
综合类   10篇
一般理论   1篇
预防医学   415篇
眼科学   61篇
药学   455篇
中国医学   20篇
肿瘤学   702篇
  2023年   41篇
  2022年   47篇
  2021年   200篇
  2020年   122篇
  2019年   160篇
  2018年   153篇
  2017年   132篇
  2016年   139篇
  2015年   178篇
  2014年   211篇
  2013年   263篇
  2012年   485篇
  2011年   396篇
  2010年   219篇
  2009年   192篇
  2008年   344篇
  2007年   354篇
  2006年   367篇
  2005年   372篇
  2004年   351篇
  2003年   310篇
  2002年   262篇
  2001年   43篇
  2000年   39篇
  1999年   38篇
  1998年   54篇
  1997年   35篇
  1996年   26篇
  1995年   39篇
  1994年   26篇
  1993年   28篇
  1992年   15篇
  1991年   23篇
  1990年   9篇
  1989年   11篇
  1988年   17篇
  1987年   14篇
  1986年   17篇
  1985年   8篇
  1984年   11篇
  1983年   10篇
  1982年   6篇
  1981年   9篇
  1979年   10篇
  1978年   10篇
  1977年   4篇
  1976年   7篇
  1974年   6篇
  1969年   3篇
  1968年   3篇
排序方式: 共有5841条查询结果,搜索用时 607 毫秒
1.
Colorectal cancer (CRC) screening programs help diagnose cancer precursors and early cancers and help reduce CRC mortality. However, currently recommended tests, the fecal immunochemical test (FIT) and colonoscopy, have low uptake. There is therefore a pressing need for screening strategies that are minimally invasive and consequently more acceptable to patients, most likely blood based, to increase early CRC identification. MicroRNAs (miRNAs) released from cancer cells are detectable in plasma in a remarkably stable form, making them ideal cancer biomarkers. Using plasma samples from FIT-positive (FIT+) subjects in an Italian CRC screening program, we aimed to identify plasma circulating miRNAs that detect early CRC. miRNAs were initially investigated by quantitative real-time PCR in plasma from 60 FIT+ subjects undergoing colonoscopy at Fondazione IRCCS Istituto Nazionale dei Tumori, then tested on an internal validation cohort (IVC, 201 cases) and finally in a large multicenter prospective series (external validation cohort [EVC], 1121 cases). For each endoscopic lesion (low-grade adenoma [LgA], high-grade adenoma [HgA], cancer lesion [CL]), specific signatures were identified in the IVC and confirmed on the EVC. A two-miRNA-based signature for CL and six-miRNA signatures for LgA and HgA were selected. In a multivariate analysis including sex and age at blood collection, the areas under the receiver operating characteristic curve (95% confidence interval) of the signatures were 0.644 (0.607–0.682), 0.670 (0.626–0.714) and 0.682 (0.580–0.785) for LgA, HgA and CL, respectively. A miRNA-based test could be introduced into the FIT+ workflow of CRC screening programs so as to schedule colonoscopies only for subjects likely to benefit most.  相似文献   
2.
3.
4.
The purpose of the work was to set‐up a simple method to evaluate the contribution of Mn2+ ions in the intra‐ and extracellular tumor compartments in a MEMRI experiment. This task has been tackled by “silencing” the relaxation enhancement arising from Mn2+ ions in the extracellular space. In vitro relaxometric measurements allowed assessment of the sequestering activity of DO2A (1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid) towards Mn2+ ions, as the addition of Ca‐DO2A to a solution of MnCl2 causes a drop of relaxivity upon the formation of the highly stable and low‐relaxivity Mn‐DO2A. It has been proved that the sequestering ability of DO2A towards Mn2+ ions is also fully effective in the presence of serum albumin. Moreover, it has been shown that Mn‐DO2A does not enter cell membranes, nor does the presence of Ca‐DO2A in the extracellular space prompt migration of Mn ions from the intracellular compartment. On this basis the in vivo, instantaneous, drop in SE% (percent signal enhancement) in T1‐weighted images is taken as evidence of the sequestration of extracellular Mn2+ ions upon addition of Ca‐DO2A. By applying the method to B16F10 tumor bearing mice, T1 decrease is readily detected in the tumor region, whereas a negligible change in SE% is observed in kidneys, liver and muscle. The relaxometric MRI results have been validated by ICP‐MS measurements. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
5.
Aim and methods  Nutrition, unhealthy lifestyles and cancer appear to be strictly related, but few authors have analysed the interest in dietary information of cancer patients and their families. This survey was conducted in the Veneto area (Italy) to investigate the concern of cancer patients and their family members about diet as a health tool before and after diagnosis of cancer. Results  Seven hundred and four questionnaires were collected: 380 from cancer patients and 324 from family members of cancer subjects. Breast cancer (BC) was the most frequent disease for patients (61.8%) as well as families (26.5%). Generally, the importance of having precise diet information after diagnosis is recognised by 40.3% of patients, with significant differences between the various types of cancer: gastric and colon/rectum cancer (GCC) patients were more concerned than BC women about precise information concerning a diet to follow immediately after diagnosis (p = 0.000, ODs = 3.10, CI 1.68–5.71) or during treatments (p = 0.001, ODs = 2.67, CI 1.46–4.89). The nutritional information is supplied to patients in 34% of cases and to relatives in 30.3%, often from non-medical sources. In total healthcare workers (family doctor, oncologist, surgeon, dietician) represented the exclusive source of dietary information for 24.9% of patients and 22.9% of family members. Diet after diagnosis changes in 69.1% of GCC patients and in 39.2% of BC women. Relatives, particularly women, report difficulties preparing patients’ meals in 30.7% of cases, changes in the eating habits of the entire family in 29.9% and discontent connected with patients diet in 13.9%. The concern about proper nutrition after diagnosis increases more in GCC subjects (p < 0.025) when compared to BC subjects and in patients with more recent diagnosis (p < 0.041) when compared with patients with diagnosis >5 years ago, while in family members the interest in diet after diagnosis increases more in women than in men (p < 0.030) without other differences regarding the degree of relationship, type of cancer or diagnosis time. Relatives (92.7%) have more interest in nutritional education than patients (74.9%). Cancer patients <65 years were more interested in educational initiatives concerning nutrition (p = 0.000, ODs = 4.46, CI 2.6–7.4) than older patients (>65 years) and female subjects were more concerned than male patients (p = 0.008, ODs = 2.11, CI 1.2–3.6). Conclusions  The interest in the dietary knowledge and in educational initiatives concerning nutrition is high in cancer patients and their relatives, although it decreases with the age. The poor attention paid to nutrition of cancer patients by various healthcare workers deserves consideration, since the psychophysical wellbeing and perhaps also survival of cancer patients can be improved by correct dietary management, as well as, naturally, by the principal treatments themselves.  相似文献   
6.

Ethnopharmacological importance

Celastrus paniculatus Willd. (Celastraceae) is an Ayurvedic remedy used for the treatment of a number of diseases, including bowel spasms.

Aim of the study

To investigate the mode of the relaxing action of a methanolic extract prepared from the seeds of Celastrus paniculatus (CPE, 0.0001–10 μg/mL) in the rat ileum and to try to confirm on human tissues the intestinal pharmacological activity of the extract.

Materials and methods

The relaxant effect of CPE was studied in vitro by evaluating its effect on the spontaneous contractions of the isolated ileum.

Results

CPE exerted a tetrodotoxin- and ω-conotoxin-resistant inhibitory effect on rat ileum motility (IC50: 0.24 ± 0.02 μg/mL; Emax: 99.0 ± 0.60%). The inhibitory effect was reduced by nifedipine but not by cyclopiazonic acid. Experiments with specific antagonists enabled us to exclude the involvement of the main endogenous spasmogenic (i.e. acetylcholine and tachykinins) and relaxing (noradrenaline, nitric oxide, ATP) compounds. CPE also relaxed the isolated human ileum (IC50: 0.26 ± 0.02 μg/mL; Emax: 99.1 ± 0.46%).

Conclusion

It is concluded that (i) CPE exerted a powerful myogenic and L-type Ca2+-dependent relaxing effect in the isolated rat ileum and that (ii) the human ileum is sensitive to the inhibitory effect of CPE. If confirmed in vivo, our data could explain the traditional use of this herb in the treatment of intestinal spasms.  相似文献   
7.
The occurrence of transitory cognitive impairment during diffuse subclinical electroencephalographic (EEG) discharges has been widely documented but the role of the parameters influencing the cognitive performance and the involvement of motor or verbal response in the tasks used is still under debate. Fifteen patients suffering from primary generalized epilepsy with frequent bisynchronous EEG epileptic bursts underwent a shape recognition task during EEG monitoring. The test sequence was as follows: memorandum, pause, and multiple choice set. After pressing the response button, the patient was asked to confirm the choice verbally. The following parameters were considered: geometrical complexity of the shape, chronological position of the burst occurring during the single test, and the duration of discharge ranging from 1 to 3 s. Results showed a significant increase in incorrect responses during the test when discharges occurred, with more errors occurring for difficult than for easy shapes. Neither the discharge position nor the duration of the epileptic burst influenced the performance. Diffuse epileptic activity of short duration produced selective effects on the cognitive process regardless of the motor component of the response.  相似文献   
8.
9.
10.
Ten protein coding loci (6‐PGD, A1‐AT, ACP1, CaII, ESD, GC, GPX1, Hbβ, PGM1, and TF) were analyzed in the Mbenzele Pygmies from the Central African Republic. The frequency data were used to calculate the genetic distances between Mbenzele Pygmies and other African groups. In the principal coordinate plot of FST genetic distances, the Mbenzele cluster together with other Pygmies of the western cluster, the Biaka from C.A.R., Gielli from Cameroon, and Babinga from Congo. By contrast, they are considerably distanced from other Pygmy groups of the eastern cluster (Twa from Rwanda, Mbuti from Zaire). Genetic distances obtained using protein loci were compared with those based on microsatellite loci. The two distance matrices are insignificantly correlated (r = 0.268; one tail probability = 0.332), and the main difference is in the higher genetic affinity between the Mbenzele and Biaka Pygmies observed at the protein level. Although reasons underlying the discrepancy between inter‐populational variation at protein and DNA loci are not established with certainty, the comparison suggests that the genetic distance between the Mbenzele and Biaka Pygmies at microsatellite loci could have been shaped by genetic drift. Am. J. Hum. Biol. 14:9–14, 2002.© 2002 Wiley‐Liss, Inc.  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