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   15777篇
  免费   758篇
  国内免费   51篇
耳鼻咽喉   335篇
儿科学   343篇
妇产科学   317篇
基础医学   2701篇
口腔科学   349篇
临床医学   1407篇
内科学   2609篇
皮肤病学   399篇
神经病学   1615篇
特种医学   841篇
外科学   2264篇
综合类   110篇
一般理论   2篇
预防医学   779篇
眼科学   531篇
药学   1040篇
中国医学   19篇
肿瘤学   925篇
  2022年   97篇
  2021年   172篇
  2020年   115篇
  2019年   196篇
  2018年   251篇
  2017年   193篇
  2016年   304篇
  2015年   307篇
  2014年   371篇
  2013年   468篇
  2012年   866篇
  2011年   803篇
  2010年   528篇
  2009年   519篇
  2008年   702篇
  2007年   815篇
  2006年   861篇
  2005年   877篇
  2004年   825篇
  2003年   737篇
  2002年   778篇
  2001年   372篇
  2000年   298篇
  1999年   291篇
  1998年   226篇
  1997年   184篇
  1996年   159篇
  1995年   130篇
  1994年   110篇
  1993年   106篇
  1992年   139篇
  1991年   155篇
  1990年   158篇
  1989年   160篇
  1988年   160篇
  1987年   125篇
  1986年   112篇
  1985年   130篇
  1984年   120篇
  1983年   85篇
  1982年   73篇
  1981年   86篇
  1979年   111篇
  1978年   82篇
  1977年   89篇
  1976年   77篇
  1975年   78篇
  1974年   83篇
  1973年   73篇
  1972年   83篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The diagnosis of idiopathic Parkinson's disease (PD) can be achieved with high degrees of accuracy in cases with full expression of classical clinical features. However, diagnostic uncertainty remains in early disease with subtle or ambiguous signs. Functional imaging has been suggested to increase the diagnostic yield in parkinsonian syndromes with uncertain clinical classification. Loss of striatal dopamine nerve terminal function, a hallmark of neurodegenerative Parkinsonism, is strongly related to decreases of dopamine transporter (DAT) density, which can be measured by single photon emission computed tomography (SPECT). The use of DAT‐SPECT facilitates the differential diagnosis in patients with isolated tremor symptoms not fulfilling PD or essential tremor criteria, drug‐induced, psychogenic and vascular Parkinsonism as well as dementia when associated with Parkinsonism. This review addresses the value of DAT‐SPECT in early differential diagnosis, and its potential as a screening tool for subjects at risk of developing PD as well as issues around the assessment of disease progression. © 2007 Movement Disorder Society  相似文献   
72.
The developmental courses of high-risk and resilient children were analyzed in a follow-up study of members of a 1955 birth cohort on the island of Kauai, Hawaii. Relative impact of risk and protective factors changed at various life phases, with males displaying greater vulnerability than females in their first decade and less during their second; another shift appears under way at the beginning of their fourth decade. Certain protective factors seem to have a more general effect on adaptation than do specific risk factors.  相似文献   
73.
Genetic engineering provides the opportunity for the synthesis of human proteins and derivatives thereof which are of significant value for replacement therapy. However, in addition to genetic engineering an extensive process development has to be carried out in order to establish an economic production process and to guarantee consistently high product quality from batch to batch. This includes the characterization of the production host cell vector construct, the validation of the fermentation and the protein purification process as well as the lyophilization and the reconstitution of the final product. A number of in-process and final product controls have to be established and limits for the specification have to be elaborated to provide consistent product quality. Real time stability data have to be supplied because data from accelerated conditions do not allow extrapolation of the shelf life of proteins. Data obtained from process development and validation of the production process contributes to the preparation of the chemical pharmaceutical dossier and the expert report to be submitted to the regulatory authorities.  相似文献   
74.
75.
Werner  U.  Seitz  O.  Szelenyi  I. 《Inflammation research》1993,38(2):C112-C114

In the present study the effects of drugs, with different modes of action, on FMLP-stimulated release of elastase from human leukocytes were investigatedin vitro. Anti-asthmatic and anti-allergic drugs were compared to well-known anti-inflammatory and anti-histamine agents. The anti-asthmatic/anti-allergic compounds azelastine, astemizole and oxatomide, and the 5-lipoxygenase inhibitor NDGA, were able to suppress the release of elastase from human leukocytes in concentrations between 10 and 100 μM. NSAIDs such as indomethacin, diclofenac and piroxicam and the glucocorticoids dexamethasone and hydrocortisone showed little or no activity. The histamine H1 antagonists mepyramine and ketotifen and the calcium antagonists verapamil, nifedipine and TMB-8 were also ineffective in suppressing FMLP-induced elastase release. Reduction in elastase release by azelastine, that accumulates in lung tissue during long-term treatment in animals, may contribute to its anti-inflammatory and anti-allergic effects which are thought to be central to its use in asthma therapy.

  相似文献   
76.
Zusammenfassung Herzkreislauf-Erkrankungen sind die wichtigste Todesursache in den Industrieländern. Anders als die Krebsforschung, vernachlässigt die Herzkreislauf-Forschung bei uns toxische Wirkungen weitgehend, abgesehen von den Genussgiften Nikotin, Koffein, Alkohol, einigen Medikamenten und den (bei uns) arbeitsmedizinischen Randproblemen Schwefelkohlenstoff, Nitratester und Kohlenmonoxid. Es sind aber zahlreiche kardiovaskulärtoxische Arbeitsstoffe bekannt: neben den Genannten auch organische Lösemittel, Metalle, Pestizide, Vinylchlorid, polychlorierte Biphenyle, etc. Ebenso sind verschiedene toxische Wirkmechanismen auf das Herzkreislaufsystem bekannt: z. B. langfristige Entstehung von Arteriosklerose, Bluthochdruck, koronaren Herzerkrankungen, Herzmuskelerkrankungen und Herzrhythmusstörungen. Die Vernachlässigung kardiovaskulär-toxischer Wirkungen widerspricht der Logik; bei vielen Herzkreislauf-Erkrankungen ist eine toxische Mitverursachung plausibel; mit einer weiteren Aufdeckung kardiovaskulär-toxischer Wirkungen ist zu rechnen.
Summary Cardiovascular diseases are the most important cause of mortality in industrialised countries. Contrary to cancer research, cardiovascular research mostly ignores toxic effects, apart from nicotine, caffeine, alcohol, a few pharmaceutical drugs, and the (in our countries) minor workplace problems carbon disulfide, nitrate esters, and carbon monoxide. But many workplace chemicals are known to be harmful to the cardiovascular system: beside the mentioned, also organic solvents, metals, pesticides, vinylchloride, polychlorinated biphenyles, etc. Several toxic mechanisms in the cardiovascular system are already known: e.g., long-term development of atherosclerosis, hypertension, coronary heart disease, cardiomyopathy, and arrhythmia. To neglect cardiovascular toxicity is contrary to logic; for many cardiovascular diseases toxic effects may be constitutive; more of these effects may be seen in the future.

Résumé Les maladies cardiovasculaires sont les causes de mort les plus fréquentes dans les pays industrialisés. Contrairement à la recherche sur le cancer, la recherche cardiovasculaire chez nous néglige largement les effets toxiques, à part la nicotine, la caféine, l'alcool, quelques médicaments et les problèmes (chez nous) marginaux de médecine du travail tels que le sulfure de carbone, les esters de nitrate et le monoxyde de carbone. Beaucoup de substances rencontrées sur le lieu de travail sont pourtant connues pour être toxiques pour le système cardiovasculaire: celles déjà citées, les solvants organiques, les métaux, les pesticides, le chlorure de vinyl, les biphényles polychlorés, etc. Plusieurs mécanismes d'action toxique sur le système cardiovasculaires sont également connus, par exemple la formation à longue échéance d'artériosclérose, d'hypertension artérielle, de coronopathies, de cardiomyopathies, de troubles du rythme cardiaque. Négliger la toxicité cardiovasculaire est illogique; les effets toxiques pourraient contribuer à la genèse de beaucoup de maladies cardiovasculaires; la découverte d'autres effets toxiques cardiovasculaires est à prévoir.
  相似文献   
77.
The aims of the present investigation were (a) to evaluate the effect of eccentric quadriceps training in patients with unilateral patellofemoral pain and (b) to compare the effect of eccentric and concentric quadriceps training in patients with bilateral patellofemoral pain. Fifteen patients (9 male and 6 female, aged 17–36 years with a mean of 27.5 years) participated in this study. Nine patients had unilateral pain and trained their painful leg eccentrically, while six had bilateral pain and trained one leg eccentrically and the other concentrically. Quadriceps muscle training was performed on a Kin-Com dynamometer at 90°/s and 120°/s angular velocity twice a week for 8 weeks. Before and after the treatment period the thigh muscle torques were measured on the Kin-Com dynamometer at 60°/s, 90°/s, 120°/s and 180°/s for quadriceps and at 60°/s and 180°/s for hamstrings. Nine controls, matched for gender and age with the group with unilateral pain, were tested in the same way on the Kin-Com dynamometer. For functional evaluation a knee score was calculated before training, after 8 weeks of training and at a mean of 3.4 years after completion of the training. After 8 weeks of training and at follow-up times of 1 and 3.4 years the patients were also questioned regarding whether or not they felt improvement from the training programme. To determine the degree of knee pain during the training Borg's pain scale was used. The results showed that, compared with the controls, the patients had a significantly lower knee extensor torque in their painful leg at all velocities measured. The greatest difference was found during eccentric actions. However, in comparison with the controls there were no significant differences in eccent ic and concentric knee flexor torques. After training there was a significant increase particularly in eccentric but also in concentric torque of the knee extensor in the painful leg of the eccentrically trained group. Of the six patients in the bilateral training group there were five who increased their concentric knee extensor torque and three who increased their eccentric torque. There were no significant differences in concentric and eccentric knee flexor torques before and after training in either of the legs in both training groups. The hamstring/quadriceps ratio was significantly higher in the patients' painful leg before training. However, due to increased quadriceps strength the hamstring/quadriceps ratio dropped after training. Patients in both groups reported no pain or mild pain during the training sessions. The eccentrically trained group was significantly improved both after 8 weeks of treatment and at follow-up 3.4 years later as evaluated using the knee score. The bilaterally trained group was significantly improved 3.4 years after completion of the training programme as evaluated using the knee score.  相似文献   
78.
Summary Epidermal growth factor (EGF) has been shown to stimulate DNA synthesis and cell division in normal glia. At least half of malignant human gliomas (MHG) express high levels of the EGF receptor (EGFR), which are above those detected in normal brain. The demonstration that antibodies against the EGFR inhibit the growth of squamous cell carcinoma line A-431, with large numbers of EGFR, in vitro and in vivo raises the possibility that these agents could be used therapeutically against malignant human gliomas either alone or conjugated to other agents. We have measured the growth effects of EGF and an anti-EGFR monoclonal antibody, 528 (Ab-528), on four well-characterized human malignant glioma cell lines, D-263 MG, D-247 MG, U-343 MGa Cl 26, and D-37 MG, with 2.9×104, 1.5×105, 8.6×105 and 1.59×106 EGFRs per cell, respectively. EGF significantly increased cell number in D-263 MG and D-37 MG by 65% and 74%, respectively, had no effect on D-247 MG, and significantly decreased cell number in U-343 MGa Cl 26 by 39%. U-343 MGa Cl 26 growth was inhibited 19% by Ab-528, but Ab-528 had no effect on growth of the other MHG lines. Ab-528 significantly inhibited all EGF-mediated growth effects. These studies demonstrate that, although Ab-528 alone has little antiproliferative activity on MGH, it successfully competes with EGF to reduce the biological effects of EGF-EGFR binding. Therefore, this antibody could potentially be used to target radioisotopes to MHG via the EGFR for diagnosis and therapy.Supported by Grants CA-11898, NS-20023, CA-43722, and the Association for Brain Tumor Research (MHW, PAH)  相似文献   
79.
It has been demonstrated in transgenic mice that the overexpression of human phospholipase A2 group IIA (sPLA2), an acute-phase reactant, is associated with depressed plasma cholesterol levels, altered lipoprotein compositions, and increased lipid depositions in aortic walls. It was the aim of the present study to investigate whether the reduced plasma cholesterol levels in sPLA2-transgenic mice may be due to an increased transfer of lipids from sPLA2-modified lipoproteins to the liver and/or other nonvascular tissues. Ten sPLA2-transgenic mice and an equal number of nontransgenic littermates were fed a cholesterol-enriched (1%) diet for 13 weeks. After autopsy, cholesterol and triglyceride concentrations were measured in homogenates of liver, spleen, kidney, and myocardial tissues. Compared to the nontransgenic controls, the sPLA2-transgenic mice exhibited significantly lower plasma cholesterol levels, which was due to a reduction in both HDL and beta-lipoprotein (LDL + beta-VLDL) cholesterol. Liver tissues from the transgenic mice were found to contain significantly increased concentrations of free and esterified cholesterol, which was not associated with increased triglyceride concentrations. Spleen, kidney, and heart tissues of the two animal groups showed no significant differences in cholesterol or triglyceride concentrations. The findings suggest that the overexpression of human secretory phospholipase A2 group IIA leads to an enhanced delivery of cholesterol from phospholipolysed lipoproteins to the liver. This mechanism is likely to contribute to the development of hypocholesterolemia observed in patients with inflammatory diseases.  相似文献   
80.
Recent studies have revealed that dynamic biomechanical forces can exert antiinflammatory and antiproteolytic effects on fibrocartitage. Whether the effects of mechanical strain also involve stimulation of the insulin-like growth factor (IGF) system and, therefore, of growth and repair of fibrocartilage has yet to be determined. The objective of this in vitro study was to determine if continuous biophysical strain regulates the gene expression of IGF1, IGF2, IGF1 receptor (IGF1R), insulin receptor substrate (IRS1), and IGF-binding proteins (IGFBP) 3 and 5 in cells from the fibrocartilaginous disc of the temporomandibular joint (TMJ). Rat TMJ disc cells were subjected to continuous biophysical strain (3% and 20%) for 4 and 24 h. Subsequently, RNA was extracted and real-time PCR was performed using an iCycler iQ detection system to analyze the gene expression of the IGF system. The gene expression of IGF1, IGF2, IGF1R, IRS1, IGFBP3, and IGFBP5 was significantly (p < 0.05) inhibited when cells were subjected to continuous biophysical strain, as compared to control at both time points. High strain induced a stronger inhibition of these molecules as compared to strain of Low magnitude. In conclusion, continuous biophysical strain seems to downregulate the expression of the IGF system and may, therefore, reduce the potential of fibrocartilage for growth and repair.  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