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   15374篇
  免费   821篇
  国内免费   69篇
耳鼻咽喉   129篇
儿科学   295篇
妇产科学   469篇
基础医学   1855篇
口腔科学   531篇
临床医学   1241篇
内科学   4376篇
皮肤病学   377篇
神经病学   1357篇
特种医学   315篇
外科学   2240篇
综合类   95篇
一般理论   2篇
预防医学   1130篇
眼科学   233篇
药学   833篇
中国医学   71篇
肿瘤学   715篇
  2024年   10篇
  2023年   154篇
  2022年   369篇
  2021年   633篇
  2020年   332篇
  2019年   517篇
  2018年   685篇
  2017年   400篇
  2016年   409篇
  2015年   464篇
  2014年   704篇
  2013年   827篇
  2012年   1302篇
  2011年   1324篇
  2010年   675篇
  2009年   597篇
  2008年   1024篇
  2007年   950篇
  2006年   918篇
  2005年   882篇
  2004年   781篇
  2003年   620篇
  2002年   620篇
  2001年   85篇
  2000年   73篇
  1999年   91篇
  1998年   95篇
  1997年   63篇
  1996年   71篇
  1995年   60篇
  1994年   48篇
  1993年   33篇
  1992年   47篇
  1991年   30篇
  1990年   27篇
  1989年   22篇
  1988年   21篇
  1987年   12篇
  1986年   27篇
  1985年   27篇
  1984年   26篇
  1983年   20篇
  1982年   23篇
  1981年   20篇
  1980年   22篇
  1979年   10篇
  1978年   13篇
  1974年   12篇
  1973年   19篇
  1972年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Background: The Patient-Reported Outcomes Measurement Information System Upper Extremity (PROMIS UE) computer adaptive test was developed to improve precision and reduce question burden. We hypothesized that in patients with carpal tunnel syndrome (CTS): (1) PROMIS UE would correlate with established patient-reported outcome measures (PROs); (2) the time and number of questions required would be lower than current metrics; (3) there would be no floor or ceiling effects; and (4) PROMIS UE would not correlate with disease severity. Methods: Patients undergoing electrodiagnostic evaluation found to have a primary diagnosis of unilateral CTS prospectively completed PROMIS UE, Quick Disabilities of the Arm, Shoulder and Hand (qDASH), and Boston Carpal Tunnel Syndrome Questionnaire (BCTQ). Electrophysiologic and clinical severity was recorded. The relationships among PROs were described with Spearman coefficients. A floor or ceiling effect was confirmed if >15% of patients achieved the lowest or highest possible score, respectively. Results: Fifty-one patients (average, 53.9 years) were enrolled. An excellent correlation was identified between PROMIS UE and qDASH (R = −0.76, P < .001). There was a good correlation between PROMIS UE and BCTQ (R = −0.58, P < 0.001). The PROMIS UE required less time and fewer questions than qDASH and BCTQ (P = .02 and P < .001). There were no floor or ceiling effects. Neither neurophysiologic nor clinical severity correlated with PROMIS UE (R = 0.24, P > .05 and R = −0.18, P > .05). Conclusions: The PROMIS UE has an excellent correlation with qDASH and a good correlation with BCTQ in patients with CTS. Furthermore, PROMIS UE required less time and fewer questions than established PROs. Used as a single PRO, PROMIS UE represents a practical alternative to current metrics in patients with CTS.  相似文献   
92.
Abstract

Information on children’s diet including bioactive compounds is quite scarce. This observational study investigated the composition of the diet of children living in Parma (Italy; n?=?172, 8–10?years) using 3-day food records completed in winter and spring. Mean daily intakes of food groups, energy and nutrients were obtained using the national food database, while (poly)phenol contents were estimated from Phenol-Explorer or by specific literature searches. Food consumption, energy and nutrient intakes decreased in spring and were partially in line with national data. Adherence to the nutritional recommendations was not satisfied for the majority of nutrients. Main contributors to the phenolic intake were flavonoids (flavan-3-ols) and phenolic acids (hydroxycinnamic acids), while main dietary sources were fruit, chocolate-based products, vegetables, and tea & coffee (decaffeinated). This study provided the first comprehensive analysis of the nutritional composition of children’s diet. Future research should look at the health implications of dietary choices in children.  相似文献   
93.
The role of tumour suppressor genes in the development of human cancers has been studied extensively. In viral carcinogenesis, the inactivation of suppressor proteins such as retinoblastoma (pRb) and p53, and cellular oncogenes overexpression, such as c-myc, has been the subject of a number of investigations. In uterine-cervix carcinomas, where high-risk human papillomavirus (HPV) plays an important role, pRb and p53 are inactivated by E7 and E6 viral oncoproteins, respectively. However, little is known about the in situ expression of some of these proteins in pre-malignant and malignant cervical tissues. On the other hand, it has also been demonstrated that c-myc is involved in cervical carcinogenesis, and that pRb participates in the control of c-myc gene expression. By using immunostaining techniques, we investigated pRb immunodetection pattern in normal tissues, squamous intraepithelial lesions (SILs) and invasive carcinomas from the uterine cervix. Our data show low pRb detection in both normal cervical tissue and invasive lesions, but a higher expression in SILs. C-Myc protein was observed in most of the cellular nuclei of the invasive lesions, while in SILs was low. These findings indicate a heterogeneous pRb immunostaining during the different stages of cervical carcinogenesis, and suggest that this staining pattern could be a common feature implicated in the pathogenesis of uterine-cervix carcinoma.  相似文献   
94.
Mantle cell lymphoma (MCL) is a B-cell neoplasm with a relatively aggressive clinical course. There is a very small subgroup of patients who present with atypical lymphocytes in peripheral blood, with or without lymphocytosis, lymphadenopathy, or splenomegaly, and with an indolent clinical course. They frequently show mutated IgV(H) genes and CD5 negativity. We report an asymptomatic elderly patient who presented with a single submandibular lymphadenopathy. The biopsy showed immunophenotype and t(11;14)(q13;q32) consistent with MCL. The abnormal lymphoid population was also detected in peripheral blood and bone marrow. The patient has remained asymptomatic for 5 years without receiving any therapy. It is uncertain whether these cases represent an early-stage event in the development or an indolent form of MCL. The existence of such asymptomatic patients with an indolent clinical course should induce a strict clinical judgment in terms of therapeutic decisions.  相似文献   
95.
The present review summarizes recent studies describing the role of renal sympathetic innervation in the regulation of renal function during development. The afferent renal innervation appears early during fetal life and probably precedes the development of efferent renal nerves. There is suggestive evidence that renal nerves are required for the proper development of the kidney and that neurotrophic growth factors play an important role in renal embryogenesis and in renal tubular differentiation. Renal sympathetic innervation modulates renal hemodynamics early during development. Renal nerve stimulation during -adrenoceptor blockade produces renal vasodilation in fetal and newborn animals but not in adults. Unlike the effect of renal nerves on fetal renal hemodynamics which is observed in the young fetus, the role of renal sympathetic nerves in modulating fluid and electrolyte homeostasis seems to develop during late gestation. Recent studies have also shown that renal nerves play an important role in regulating renin secretion during the transition from fetal to newborn life. For example, renal denervation during fetal life suppressed the physiological rise in plasma renin activity associated with delivery and decreased renal renin mRNA levels after birth. Taken together, these studies suggest that renal nerves influence fetal renal development and that the influence of renal sympathetic innervation on renal hemodynamics and function changes with maturation.  相似文献   
96.
Globus pharyngeus is a relatively common complaint in an ear, nose, and throat consulting room and may account for 3–4% of outpatient referrals. The cause is still unknown, although a number of hypotheses have been suggested. Between 40% and 75% of the patients remain symptomatic despite any treatment regimen. Thirteen patients from a group of 124 with the diagnosis of globus pharyngeus and no response to medical treatment were treated with partial epiglottectomies. One year after the surgery all but one patient were free of symptoms. Our experience indicates that partial epiglottectomy can be a good treatment for those patients with globus pharyngeus in whom no cause is found after all studies are performed or when medical treatment fails. Received: 19 October 1999 / Accepted: 16 December 1999  相似文献   
97.
Phorbol ester protein kinase C (PKC) activators and PKC isozyme over-expression have been shown to significantly reduce intracellular accumulation of chemotherapeutic drugs, in association with the induction of multidrug resistance (MDR) in drug-sensitive cancer cells and enhancement of drug resistance in MDR cancer cells. These observations constitute solid evidence that PKC plays a significant role in the MDR phenotype of cancer cells. PKC-catalyzed phosphorylation of the drug-efflux pump P-glycoprotein was recently ruled out as a contributing factor in MDR. At present, the sole drug transport-related event that has been identified as a component of the role of PKC in MDR is PKC-induced expression of the P-glycoprotein-encoding gene mdr1. The objective of this study was to test the hypothesis that PKC can modulate the uptake of chemotherapeutic drugs in cancer cells independently of P-glycoprotein. We analyzed the effects of selective PKC activators/inhibitors on the uptake of radiolabelled cytotoxic drugs by cultured human colon cancer cells that lacked P-glycoprotein activity and did not express the drug efflux pump at the level of message (mdr1) or protein. We found that the selective PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA) significantly reduced uptake of [14C] Adriamycin and [3H] vincristine in human colon cancer cells devoid of P-glycoprotein activity, and that PKC-inhibitory N-myristoylated PKC- pseudosubstrate synthetic peptides potently and selectively induced uptake of the cytotoxic drugs in the phorbol ester-treated and non-treated colon cancer cells. TPA treatment of the cells did not induce expression of either P-glycoprotein or its message mdr1. In contrast with [14C]Adriamycin and [3H] vincristine uptake, [3H] 5-fluorouracil uptake by the cells was unaffected by TPA and reduced by the PKC-inhibitory peptides. These results indicate that PKC activation can significantly reduce the uptake of multiple cytotoxic drugs by cancer cells independently of P-glycoprotein, and that N-myristoylated PKC- pseudosubstrate peptides potently and selectively induce uptake of multiple cytotoxic drugs in cultured human colon cancer cells by a novel mechanism that does not involve P-glycoprotein and may involve PKC isozyme inhibition. Thus, N-myristoylated PKC- pseudosubstrate peptides may offer a basis for the development of agents that reverse intrinsic drug resistance in human colon cancer.  相似文献   
98.
99.
In recent years, eating disorders (Anorexia and Bulimia Nervosa) have increased and are appearing at increasingly younger ages. They affect predominantly adolescent females 12 to 25 years of age. The objective of this study of adolescents is to detect and discuss unhealthy eating behaviour, defined by either of two factors: (1) following a slimming diet not advised or supervised by any person trained in health care; or (2) eating very large quantities at irregular times, not related to anxiety or stress. A transversal study has been undertaken of 630 school children of 14–18 years of age (average: 15.9 years) in Cádiz (Andalucia, Spain), using an anonymous self-reporting questionnaire to collect data on personal and educational situation, on eating habits, on nutritive intake and knowledge of nutrition, and on dieting and physical exercise. The study has considered averages, ratios, statistical significance (x 2) and, as a measure of risk, the Disequality Ratio of Prevalence (DRP). Anomalous eating behaviour was detected in 46.3% (292), with females predominant by a ratio of 2:1. Comparing groups with anomalous and with normal eating habits, significant differences were detected in respect of: perception of body image (p<0.001), frequency of weighing oneself (p<0.05), periods of abstinence from eating (DRP 1.66; 95% confidence interval (CI): 1.66–2.37), provocation of vomiting (DRP 2.02; 95% CI: 1.13–3.65), use of laxatives (DRP 4.25; 95% CI: 1.08–9.63), and the exclusion of certain meals and types of food, mainly bread and cereals, fats and sugars. Conclusions are drawn on the substantial scale of unhealthy eating behaviour among adolescents in Cadiz. More adequate education on personal health and related social issues should be provided.  相似文献   
100.
The purpose of these experiments was to study the incidence of stress ulcers in restrained rats and to correlate it with hypothalamic and adrenal cortical and medullary activity, with and without vagotomy. A total of 217 adult rats were used, grouped into 56 sets, and distributed at random in 5 experimental groups. Restraint was followed by a 79% incidence of ulceration in the glandular portion of the gastric mucosa. Vagotomy made these worse (p<0.01). Hypothalamic levels of catecholamines and serotonin showed no significant changes. Urinary measurements revealed decreased excretion of 17-ketosteroids (p<0.001), increased excretion of uropepsinogen (p<0.01), and no significant changes in vanillylmandelic acid among the rats submitted to immobilization. In the adrenal glands of stressed animals, there was a decreased level of catecholamines (p<0.01) and no significant changes in corticosteroid content (17-ketosteroids). These results suggest that hypothalamic stimulation and the participation of the adrenal glands are not essential factors in the pathogenesis of restraint-induced experimental stress ulcer.  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