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   517332篇
  免费   33618篇
  国内免费   619篇
耳鼻咽喉   6938篇
儿科学   16950篇
妇产科学   13569篇
基础医学   85550篇
口腔科学   14514篇
临床医学   44764篇
内科学   94231篇
皮肤病学   12215篇
神经病学   36478篇
特种医学   18522篇
外国民族医学   63篇
外科学   77457篇
综合类   8496篇
一般理论   120篇
预防医学   39392篇
眼科学   12236篇
药学   40738篇
中国医学   1011篇
肿瘤学   28325篇
  2018年   5071篇
  2016年   4166篇
  2015年   4611篇
  2014年   6218篇
  2013年   9747篇
  2012年   13171篇
  2011年   14551篇
  2010年   8434篇
  2009年   7885篇
  2008年   13863篇
  2007年   14879篇
  2006年   15096篇
  2005年   14486篇
  2004年   14167篇
  2003年   13499篇
  2002年   13371篇
  2001年   24116篇
  2000年   25134篇
  1999年   20590篇
  1998年   5454篇
  1997年   4724篇
  1996年   5054篇
  1995年   4642篇
  1994年   4330篇
  1992年   15756篇
  1991年   16325篇
  1990年   16433篇
  1989年   15817篇
  1988年   14601篇
  1987年   14437篇
  1986年   13610篇
  1985年   13000篇
  1984年   9640篇
  1983年   8260篇
  1982年   4568篇
  1981年   4239篇
  1979年   9433篇
  1978年   6860篇
  1977年   5777篇
  1976年   5610篇
  1975年   6401篇
  1974年   7645篇
  1973年   7137篇
  1972年   6963篇
  1971年   6688篇
  1970年   6177篇
  1969年   5894篇
  1968年   5563篇
  1967年   5014篇
  1966年   4454篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Lipid peroxidation in the brain cortex, striatum, hippocampus, and hypothalamus of rats of the KLA and KHA lines which were distinguished by their strategies of adaptive behavior was investigated following emotional-painful stress. Significant long-term changes in lipid peroxidation were shown to occur in the brain. These had a phase character and depended on the behavioral characteristics of the animals. The investigated brain regions were characterized by different reactions of lipid peroxidation to the stress. The induced depressive-like states (on the 21st day after the stress) in rats of the KLA and KHA lines were distinguished by the largest changes in lipid peroxidation in the striatum and hypothalamus and in the striatum and hippocampus, respectively. One could conclude on the basis of these results that both identical and different mechanisms of formation and development of depression existed in the animals with different behavioral strategies.  相似文献   
962.
This paper describes a response directed stress management intervention (SMI) in the form of a Jungian based preference awareness education (PAE). It uses the Insights System of personality types to increase awareness of behaviour and communication preferences of self and different others. Eighteen self‐recruited academic employees participated for 7 weeks and received feedback about work preferences and personality type. The aim was to reduce perceptions of stress and interpersonal stress and to increase feelings of job satisfaction and interpersonal satisfaction. The data were analysed using two‐tailed t‐tests. No significant findings were observed for the total sample after training, however, interesting results were found for certain sub‐sample groups. Extravert‐thinking types, reported decreased stress levels (p > 0.018), and participants suffering high stress/interpersonal stress pre‐PAE, reported decreased stress levels (p > 0.010–0.018). Participants suffering low job/interpersonal satisfaction pre‐PAE, reported increased job satisfaction (p > 0.015–0.016). These results suggest that individuals who report high levels of stress and dissatisfaction are most likely to benefit from this type of intervention. Future PAE research might: (a) use pilot studies to meet the intervention preferences of employees that are reluctant to participate in SMIs; (b) include a wait‐list control group; use: (c) a follow up education/measures; (d) and organizational level (stressor directed) SMIs at the same time as response directed initiatives. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
963.
High-frequency respiratory impedance data measured noninvasively by the high-speed interrupter technique (HIT), particularly the first antiresonance frequency (f(ar,1)), is related to airway wall mechanics. The aim of this study was to evaluate the feasibility and repeatability of HIT in unsedated pre-term infants, and to compare values of f(ar,1) from 18 pre-term (post-conceptional age 32-37 weeks, weight 1,730-2,910 g) and 18 full-term infants (42-47 weeks, 3,920-5,340 g). Among the pre-term infants, there was good short-term repeatability of f(ar,1) within a single sleep epoch (mean (sd) coefficient of variance: 8 (1.7)%), but 95% limits of agreement for repeated measures of f(ar,1) after 3-8 h were relatively wide (-41 Hz; 37 Hz). f(ar,1) was significantly lower in pre-term infants (199 versus 257 Hz), indicating that wave propagation characteristics in pre-term airways are different from those of full-term infants. The present authors suggest that this is consistent with developmental differences in airway wall structure and compliance, including the influence of the surrounding tissue. Since flow limitation is determined by wave propagation velocity and airway cross-sectional area, it was hypothesised that the physical ability of the airways to carry large flows is fundamentally different in pre-term than in full-term infants.  相似文献   
964.
965.
OBJECTIVES: To investigate the specific complaints of physicians and technicians performing obstetric and gynecological ultrasound. METHODS: This was a cross-sectional retrospective survey. Questionnaires were distributed to members of the Israeli Society of Gynecological Ultrasound, including questions on gender and profession, number and type of scans performed, pain related to profession and any therapy undergone. Statistical analysis included chi-square or Fisher's exact test, Student's t-test, Pearson's correlation coefficient and logistic regression. RESULTS: Joint pain was reported by 51.7% (30/58) of the technicians compared with 25.3% (19/75) of the physicians (P = 0.002). It was more common in females than in males (P = 0.05) and it was more common among those who performed transabdominal sonography more frequently than they did transvaginal sonography (P = 0.004). There was a significant association between performing transabdominal ultrasound and back pain (P = 0.05). Although females reported pain more frequently, the rate of surgical procedures was higher among males (P < 0.05). CONCLUSIONS: A technician is 3.5 times more likely to report joint pain than is a physician. Transabdominal sonography is a risk for both joint and back pain. There may be gender differences in pain perception.  相似文献   
966.
967.
Positron emission tomography was performed on six patients with Rett syndrome to investigate cerebral blood flow and oxygen metabolism, and the results were compared with the concurrent clinical status of the patients. The cerebral metabolic rate of oxygen (CMRO2) was low in five patients, and oxygen extraction fraction was low in four patients; both had a tendency to decline with advancing age. Although the cause is unknown, it is suggested that impaired oxidative metabolism exists in Rett syndrome. An analysis of the distribution among brain regions showed that the ratios of values for the frontal cortex to those for the temporal cortex for both cerebral blood flow and CMRO2 were lower than those for the controls, which may indicate the loss of hyperfrontality in Rett syndrome.  相似文献   
968.
969.
Localization of ferritin using a pre-embedding diffusion technique and an indirect localization sequence has been made in 34 cases of human liver under normal and several pathological conditions. With light microscopic observation, positive immuno-staining for ferritin was demonstrated as diffuse deposits in the hepatocytes and Kupffer cells. Intensity of the positive immuno-staining for ferritin in these cells appeared to roughly coincide with serum ferritin levels of each patient, but showed no disease specificity, although hepatoma cells contained weak deposits or were negative from immuno-staining for ferritin. With electron microscopic studies, intracellular antigen was well preserved in the hepatocytes and Kupffer cells in most cases with the positive immuno-staining for ferritin being observed in cytosol and a few cisternae of rough endoplasmic reticulum. Content of the positive immuno-staining for ferritin differed considerably from one case to another and one cell to another even in the same case. There was no immuno-staining for ferritin in hemosiderin pigment, lysosome, most of rough endoplasmic reticulum, Golgi complexes, and nucleus in both cells.  相似文献   
970.
The authors performed a prospective study of the value of ultrasonography (US) and US-guided fine-needle aspiration cytology (FNAC) for assessment of N0 lesions in the neck. Preoperative US was performed in 107 patients with squamous cell carcinoma of the head and neck, who underwent 132 elective neck dissections. During the US examination of the last 54 patients, who underwent 70 elective neck dissections, US-guided FNAC was performed. US alone was found to be an unreliable method for detecting occult lymph node metastasis; the accuracy never exceeded 70% (93 of 132), with a sensitivity of 60% (32 of 53) and a specificity of 77% (61 of 79). In contrast, US-guided FNAC had an accuracy of 89% (62 of 70), a sensitivity of 76% (25 of 33), and a specificity of 100% (37 of 37). Because of the high sensitivity and specificity of US-guided FNAC for the assessment of the N0 neck, this modality may play an important role in directing treatment of these patients in the future.  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