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   32811篇
  免费   3011篇
  国内免费   613篇
耳鼻咽喉   394篇
儿科学   693篇
妇产科学   467篇
基础医学   2090篇
口腔科学   540篇
临床医学   2405篇
内科学   3254篇
皮肤病学   232篇
神经病学   1176篇
特种医学   1243篇
外国民族医学   45篇
外科学   3281篇
综合类   4204篇
预防医学   2639篇
眼科学   422篇
药学   1765篇
  17篇
中国医学   693篇
肿瘤学   10875篇
  2024年   52篇
  2023年   561篇
  2022年   1323篇
  2021年   1565篇
  2020年   1387篇
  2019年   1283篇
  2018年   1279篇
  2017年   1197篇
  2016年   1315篇
  2015年   1275篇
  2014年   2334篇
  2013年   2314篇
  2012年   2016篇
  2011年   2200篇
  2010年   1844篇
  2009年   1739篇
  2008年   1566篇
  2007年   1675篇
  2006年   1481篇
  2005年   1202篇
  2004年   1004篇
  2003年   818篇
  2002年   695篇
  2001年   592篇
  2000年   547篇
  1999年   466篇
  1998年   371篇
  1997年   310篇
  1996年   289篇
  1995年   225篇
  1994年   199篇
  1993年   150篇
  1992年   146篇
  1991年   123篇
  1990年   99篇
  1989年   98篇
  1988年   114篇
  1987年   71篇
  1986年   52篇
  1985年   95篇
  1984年   62篇
  1983年   47篇
  1982年   58篇
  1981年   27篇
  1980年   43篇
  1979年   32篇
  1978年   26篇
  1977年   23篇
  1976年   10篇
  1974年   6篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
31.
32.
Summary Experiments were performed on rats to determine whether primary afferents from the upper cervical region terminate directly on Spinothalamic and propriospinal neurones. The central terminations of primary afferents from the upper cervical region were identified by diffusely filling their axons with horseradish peroxidase. Spinothalamic neurones or propriospinal neurones were identified in the same experimental animals by using retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase. Approximately 3–11 % of Spinothalamic cells in laminae 4–6 of spinal segments C2–4 received apparent synaptic contacts from primary afferents on the soma or primary dendrites. Approximately 18–36% of propriospinal neurones with axons descending to lower thoracic or lumbar levels received apparent synaptic contacts on the soma or primary dendrites. These data provide anatomical evidence that Spinothalamic and long propriospinal neurones in the upper cervical cord are excited directly by primary afferents. The data also help to clarify the neural circuitry underlying somatic sensation and reflex movements evoked by neck receptors.  相似文献   
33.
BACKGROUND AND AIM: Electronic patient-provider communication promises to improve efficiency and effectiveness of clinical care. This study aims to explore whether a secure web-based messaging system is an effective way of providing patient care in general practices. METHOD: We conducted a randomised controlled trail and recruited 200 patients from the waiting area in one primary clinic in Norway. Participants were randomised to either the intervention group, which received access to a secure messaging system, or the control group receiving standard care without such access. Primary outcome measures were number of online consultations, telephone consultations and office visits in the two groups. Data were derived from patient records and collected 1 year prior to (baseline), and 1 year after the intervention. RESULTS: Forty-six percent of the patients who were given access to the messaging system (n=99) used the online communication system on at least one occasion (ranging from 1 to 17 messages per patient per year). A total of 147 electronic messages were sent to six general practitioners during a 1-year trial period. Eleven percent of the messages were to schedule an appointment. In 10% of the messages, the GP was unable to respond adequately and recommended an office visit. The reduction in office visits over time was greater for the intervention group than for the control group (P=0.034). There was however no significant difference in the number of telephone consultations between the groups during the study (P=0.258). CONCLUSION: The use of a secure electronic messaging system reduced the number of office visits at the general practice, but not phone consultations.  相似文献   
34.
In contrast to primary gastric lymphomas of B-cell type, little is known about primary gastric T-cell lymphomas. We describe three cases with remarkably similar features: diffuse growth, epitheliotropism, medium too large cell size, high apoptotic rates, and a CD3+, CD4+, CD8+, CD45RO+ immunophenotype. Clonal TCRγ gene rearrangement was shown in two cases. Epstein-Barr virus infection was excluded in two cases. Taking advantage of fresh-frozen material, we analyzed two cases further, revealing CD5–, CD16+, CD56–, CD57–, CD25+, CD30+, CD103 (αEβ7)+, bcl-2 protein+, CD95+, CD95 ligand(L)–. CD95L, however, was detected in histiocytic and fibroblastoid by stander cells. The lymphomas expressed granzyme B, perforin, and the TIA-1 antigen in various combinations. All three cases had a very unfavorable clinical course characterized by local recurrence and/or dissemination to other epithelial sites, leading to death within 6–12 months after the initial diagnosis despite surgery and aggressive antineoplastic treatment. These data suggest a novel variant of peripheral T-cell lymphoma operationally characterized as primary gastric, apoptosis-rich, CD103+, EBV-, T-cell lymphoma co-expressing CD4, CD8, CD16 and cytotoxic molecules. Received: 20 August 1999 / Accepted: 2 November 1999  相似文献   
35.
We compared in the anesthetized cat the effects of reversible spinalization by cold block on primary afferent depolarization (PAD) and primary afferent hyperpolarization (PAH) elicited in pairs of intraspinal collaterals of single group I afferents from the gastrocnemius nerve, one of the pairs ending in the L3 segment, around the Clarkes column nuclei, and the other in the L6 segment within the intermediate zone. PAD in each collateral was estimated by independent computer-controlled measurement of the intraspinal current required to maintain a constant probability of antidromic firing. The results indicate that the segmental and ascending collaterals of individual afferents are subjected to a tonic PAD of descending origin affecting in a differential manner the excitatory and inhibitory actions of cutaneous and joint afferents on the pathways mediating the PAD of group I fibers. The PAD-mediating networks appear to function as distributed systems whose output will be determined by the balance of the segmental and supraspinal influences received at that moment. It is suggested that the descending differential modulation of PAD enables the intraspinal arborizations of the muscle afferents to function as dynamic systems, in which information transmitted to segmental reflex pathways and to Clarkes column neurons by common sources can be decoupled by sensory and descending inputs, and funneled to specific targets according to the motor tasks to be performed.  相似文献   
36.
The Spanish Registry for Primary Immunodeficiency Diseases (REDIP) was organized in 1993. One thousand sixty-nine cases of primary immunodeficiency diseases (PID) were registered in patients diagnosed between January 1980 and December 1995. PID diagnosis was made according to the World Health Organization criteria. The most frequent disorders were IgA deficiency (n = 394) and common variable immunodeficiency (n = 213), followed by severe combined immunodeficiency (n = 61), C1 inhibitor deficiency (n = 52), X-Iinked agammaglobulinemia (n = 49), IgG subclass deficiency (n = 48), and chronic granulomatous disease (n = 32). A comparative study between REDIP and data recently obtained from the European registry (ESID Report, 1995) revealed important differences between phagocytic disorders and complement deficiencies reported in both registries, 4.9 vs 8.7 and 6.0 vs 3.6, while percentages of predominantly antibody deficiencies and T cell and combined deficiencies concurred with those reported in the European registry, 69.3 vs 64.7 and 14.7 vs 20.2, respectively. The heterogeneous nature of the geographical distribution of cases submitted may indicate underdiagnosis of PID in some country areas; surprisingly, the interval between the onset of clinical symptoms and diagnosis was significant, even in immunodeficiency diseases, such as IgA deficiency, which are easy to diagnose.  相似文献   
37.
目的:评价^32P灌注球囊预防再狭窄的有效性、可行性和安全性。方法:对猪冠状动脉左前降支行过度球囊扩张术后,治疗组以^32P作血管内照射,对照组作假照射。术后35d收获目标血管、检测血管形态、细胞增殖百分比等。结果:治疗组血管腔面积较对照组明显增大(P<0.01),新生内膜面积、血管狭窄程度和各层PCNA阳性细胞明显减小(P均<0.01)。结论:^31P灌注球囊照射预防冠状动脉再狭窄有效、安全而且可行。  相似文献   
38.
四种祛风类中药治疗原发性肾小球肾炎的临床研究   总被引:1,自引:0,他引:1  
目的 :评价口服火把花根、祖师麻、清风藤碱和雷公藤多甙单独与联合用药治疗原发性肾小球肾炎的效果。方法 :选择 6 5 6例经单味或两味祛风类中药治疗的原发性肾小球肾炎患者 ,观察不同治疗患者的临床表现、尿蛋白定量、尿常规、肝肾功能等指标变化。结果 :单味药治疗肾炎的缓解率为 2 4.0 %~ 44 .5 % ,两味药联合治疗肾炎的缓解率为 5 1.9%~ 5 9.2 % ;清风藤碱治疗的各种临床表现的肾炎缓解率均低于其他治疗组 ,单味药火把花根、祖师麻和雷公藤多甙对单纯性蛋白尿的缓解率为 5 0 .0 %~ 6 9.7% ,对单纯性血尿的缓解率为 36 .0 %~ 5 0 .0 % ,对蛋白尿合并血尿的缓解率为 19.5 %~ 2 2 .7% ,联合用药对各种表现的缓解率均高于单味药组 ,对单味药未缓解的部分病例两味药治疗仍有一定效果 ,复发率低于单味药组 ;联合用药组消化道反应、肾功能损害、停经和白细胞减少发生率与单味药组均无明显差别 ,转氨酶增高发生率增加 ,但谷丙转氨酶 >10 0 U /L者少见。结论 :四种祛风类单味药对肾小球肾炎均有一定疗效 ,联合治疗能够显著增加对肾小球肾炎的疗效  相似文献   
39.
Radiotherapy (or radiation therapy) uses ionizing radiation to selectively kill cancer cells, especially for solid tumours. Like surgery, it is meant to be a ‘local’ treatment, although its beneficial systemic effects are being discovered. It is most commonly used in addition to surgery (adjuvant, e.g. breast), but its role in the neoadjuvant setting in combination with chemotherapy for some cancers (e.g. rectum) is also established. In early stages of cancer, it can be the definitive treatment, avoiding surgery and enabling organ preservation (e.g. larynx), while in late stages, it can provide excellent palliation (e.g. bone metastasis). Radiotherapy can be delivered at various energy levels (kiloVolts, megaVolts), with various subatomic particles (e.g. electrons, protons, and high-energy electromagnetic radiation). The traditional bulky equipment (e.g. linear accelerator) needs to be housed in an underground bunker and uses complex imaging to improve precision and avoid radiation to normal tissues. Fractionated regimens spanning several days reduce individual doses. Modern techniques using mobile devices (e.g. TARGIT-IORT) can deliver radiotherapy during surgery with the highest precision and immediacy.  相似文献   
40.
BackgroundRadiotherapy after breast-conserving surgery (BCS) is not always necessary in older women staged T1N0M0 with low-risk invasive breast cancer, but few studies have concluded the detailed tumor size as a reference for avoiding radiotherapy. The study was conducted to explore and identify the optimal cutoff tumor size.MethodsThe study population was from the Surveillance, Epidemiology, and End Results (SEER) database in 2010–2016. Propensity score matching was used to balance the confounders between groups. Predictors associated with survival were analyzed by Kaplan–Meier, X-tile, Cox proportional hazards model and competing risk model.ResultsA total of 52049 women and 3846 deaths were included in the cohort with a median follow-up of 34 months. Based on the cutoff value determined by X-tile analysis, the study population were divided into small tumor group (≤14 mm in diameter) and large tumor group (>14 mm in diameter). Small tumors and radiotherapy were correlated with better breast cancer-specific survival (BCSS). In subgroup analysis, the absolute benefit of BCSS in 6 years attributed to radiotherapy was only 0.90% (RT vs. non- RT:98.77% vs. 97.87%) for patients with small tumors but up to 3.33% (RT vs. non- RT:97.10% vs. 93.77%) for those with large tumors.ConclusionSmall tumors and adjuvant radiotherapy were associated with improved long-term prognosis, and 14 mm in diameter was the cutoff tumor size of omitting radiotherapy for patients aged 65 or older with T1N0M0 stage, ER+ and HER2-breast carcinoma after BCS.  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