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   289701篇
  免费   6795篇
  国内免费   138篇
耳鼻咽喉   2888篇
儿科学   11779篇
妇产科学   6910篇
基础医学   32412篇
口腔科学   4356篇
临床医学   20504篇
内科学   52356篇
皮肤病学   4008篇
神经病学   25248篇
特种医学   13889篇
外国民族医学   32篇
外科学   47542篇
综合类   3867篇
一般理论   29篇
预防医学   23769篇
眼科学   6084篇
药学   17395篇
中国医学   947篇
肿瘤学   22619篇
  2018年   22729篇
  2017年   18065篇
  2016年   20527篇
  2015年   2090篇
  2014年   2354篇
  2013年   3069篇
  2012年   9932篇
  2011年   23991篇
  2010年   20666篇
  2009年   13336篇
  2008年   22600篇
  2007年   24984篇
  2006年   4083篇
  2005年   5819篇
  2004年   6974篇
  2003年   7802篇
  2002年   5915篇
  2001年   7264篇
  2000年   7357篇
  1999年   6010篇
  1998年   1818篇
  1997年   1754篇
  1996年   1417篇
  1995年   1298篇
  1994年   1182篇
  1993年   1174篇
  1992年   3796篇
  1991年   3657篇
  1990年   3682篇
  1989年   3418篇
  1988年   3036篇
  1987年   2933篇
  1986年   2825篇
  1985年   2650篇
  1984年   1963篇
  1983年   1614篇
  1982年   952篇
  1981年   918篇
  1980年   804篇
  1979年   1824篇
  1978年   1355篇
  1977年   1115篇
  1976年   946篇
  1975年   1183篇
  1974年   1230篇
  1973年   1200篇
  1972年   1041篇
  1971年   976篇
  1970年   899篇
  1969年   807篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
BACKGROUND: Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. OBJECTIVE: We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. METHODS: Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. RESULTS: Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. CONCLUSION: Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.  相似文献   
44.
45.
A microfluorometric method was used to determine the nuclear DNA content in the nasopharyngeal carcinomas (NPC) of 25 patients treated before 1983. Eleven patients are still alive with no evidence of disease (NED), while the rest died of their disease (DOD). All of the patients received a cycle of radiotherapy, while some also received chemotherapy or neck dissections. The neoplastic cells studied were taken from the original biopsy blocks, deparaffinized, isolated by enzymatic treatment and mechanical fragmentation, and then Feulgen-stained. The cytofluorometric measurement was carried out by a microphotometer equipped for fluorescence excitation and connected to a computer. This method allowed us to construct a histogram of the DNA content in the neoplastic cells. Different neoplastic classes were identified and represent the heteroclonality of the tumor, which can be expressed by the heteroclonality index (HCT). From the collected data it appears that the NED patients all had a low HTC (less than 1) and only 7 of the DOD patients had low HTCs (less than 1). Six of the DOD patients with a low HTC were in advanced stages of their tumor at the time of diagnosis, while the remaining patient did not complete his treatment. Our results show that the DNA analysis of the NPC cell population may offer a useful tool in predicting the biological behavior of this tumor and also improving its treatment.  相似文献   
46.
K Rehse  U Lükens  G Claus 《Archiv der Pharmazie》1987,320(12):1233-1238
Platelet Aggregation Inhibiting and Anticoagulant Effects of Oligoamines, VII: Benzene-1,3,5-trialkanamines Seventeen title compounds were synthesized. Platelet aggregation induced by collagen in vitro is inhibited by 9 of them at IC50 = 2–4 μmol/L. Seven compounds depress the formation of fibrin to ≦ 25 % of normal in concentrations below 50 μmol/L. Compound 15 [4-(2-thienylbutyl)benzene-1,3,5-trimethanamine is the first oligoamine which shows anticoagulant and antiplatelet effects at the same concentration (25 μmol/L).  相似文献   
47.
Phenytoin-induced gingival overgrowth is a recognized side effect in many cerebral palsy patients using diphenyl hydantoin for the control of seizures. Severe gingival overgrowth in these patients can affect normal masticatory function, lead to poor occlusal development, and compromise esthetics. This report addresses the complex nature of treating phenytoin-induced gingival overgrowth in a mentally retarded 20-year-old female patient. For this patient, full-mouth gingivectomy procedure was performed under general anesthesia in a single session. Post operative follow-up was uneventful. This article discusses major indications, contraindications, and protocols to be followed for periodontal surgical procedures done under general anesthesia.  相似文献   
48.
49.
The study presented here was conducted to evaluate the performance of the newly available RIDASCREEN Set (R-Biopharm AG, Darmstadt, Germany) for the detection of immunoglobulin G antibodies against Entamoeba histolytica. The sensitivity and specificity of this new enzyme-linked immunosorbent assay were evaluated using a panel of sera from 239 individuals. The assay was positive for 43 of 44 patients with invasive amebiasis, including all 18 patients with amebic liver abscess, while it was negative for 190 of 195 adult controls who were either healthy individuals or patients with other parasitic diseases. The kit was found to be highly specific (97.4%) and sensitive (97.7%) for detecting antibodies against E. histolytica in humans. Although antibody titers in patients with amebic liver abscess tend to be higher on average than in patients with invasive amebiasis, it is not possible to distinguish the two forms solely based on the results of this commercial test.  相似文献   
50.
The detection of antineuronal antibodies against cytoplasm and nuclei of Purkinje cells is considered to be an essential factor in the diagnosis of neurologic paraneoplastic syndromes. Published data rely on different immunological methods and relatively small numbers of patients. The clinical relevance of this phenomenon is not clear from the literature. A positive correlation between antibody detection and the appearance of neurologic paraneoplastic syndromes has been reported, but this finding has been questioned in critical reviews.  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