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   129821篇
  免费   8424篇
  国内免费   2193篇
耳鼻咽喉   1197篇
儿科学   3829篇
妇产科学   2700篇
基础医学   18251篇
口腔科学   4268篇
临床医学   12815篇
内科学   27610篇
皮肤病学   2922篇
神经病学   11958篇
特种医学   3464篇
外国民族医学   21篇
外科学   11577篇
综合类   3951篇
现状与发展   5篇
一般理论   53篇
预防医学   12098篇
眼科学   2525篇
药学   9945篇
  34篇
中国医学   1819篇
肿瘤学   9396篇
  2024年   216篇
  2023年   1422篇
  2022年   3272篇
  2021年   4964篇
  2020年   3264篇
  2019年   3933篇
  2018年   4387篇
  2017年   3389篇
  2016年   3825篇
  2015年   4423篇
  2014年   5875篇
  2013年   6990篇
  2012年   10580篇
  2011年   11013篇
  2010年   6122篇
  2009年   5161篇
  2008年   8485篇
  2007年   8454篇
  2006年   7949篇
  2005年   7373篇
  2004年   6351篇
  2003年   5765篇
  2002年   5137篇
  2001年   993篇
  2000年   947篇
  1999年   1140篇
  1998年   1153篇
  1997年   1014篇
  1996年   810篇
  1995年   696篇
  1994年   636篇
  1993年   475篇
  1992年   483篇
  1991年   330篇
  1990年   321篇
  1989年   277篇
  1988年   279篇
  1987年   239篇
  1986年   251篇
  1985年   185篇
  1984年   165篇
  1983年   157篇
  1982年   177篇
  1981年   134篇
  1980年   134篇
  1979年   105篇
  1978年   90篇
  1977年   84篇
  1976年   73篇
  1974年   87篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This study investigates whether tissue recoil or patient intrinsic factors influence the final position of the nipple areola complex (NAC) after reduction mammoplasty. The age, pre-operative ptosis, BMI and weight of the tissue resected were recorded as patient intrinsic factors in 37 patients undergoing reduction mammoplasty. The “spring-back” value was defined as the distance from the sternal notch to a nipple landmark on the breast meridian with the patient sitting up, minus the same measurement repeated with the patient recumbent to eliminate the pull of gravity on the breast. Spring back was measured pre-operatively for the nipple and nipple mark then post-operative for the nipple. The difference in centimeters between the final post-operative distance from the sternal notch to the nipple and the level intended by the pre-operative nipple mark was termed the “judgment error.” The final position of the post-operative nipple and the judgment error was compared to the spring-back values and patient intrinsic factors. Pre-operative ptosis was statistically related to increasing patient BMI and mass of tissue resected per breast. Pre-operative spring-back values for the nipple increased with increasing ptosis, BMI and decreasing age. Spring-back values were greater in the lower pole of the breast than in the upper pole. The final position of the nipple was higher than the pre-operative mark in 65% of cases, lower in 8% and as marked in 27% of cases. The post-operative NAC was, on average, 0.6 cm higher than planned pre-operatively. The post-operative distance from the sternal notch to the nipple increased with increasing pre-operative ptosis, mass of breast tissue resected per breast and all three spring-back values. The difference between the level of the pre-operative mark and the final nipple position showed a weak correlation with post-operative spring-back values. The parameters of ptosis, BMI, weight of tissue resected per breast and pre-operative nipple spring back reflect body habitus and breast size. Spring-back values vary between the upper and lower pole of the breast. The final NAC position was higher than that intended at pre-operative marking in the majority of cases. The surgeon instinctively marks the nipple lower in patients with greater pre-operative ptosis and in whom a larger resection is anticipated. Judgment error did not relate to intrinsic factors nor to pre-operative spring-back values; hence, these parameters cannot be applied as predictive tools for more accurate pre-operative marking of the nipple position. This study suggests that the pre-operative nipple mark should be placed, with the patient sitting up, at least 23 cm from the sternal notch and 0.6 cm lower than the final position estimated using the inframammary crease as a landmark. An invited commentary on this paper is available at .  相似文献   
52.
53.
54.
OBJECTIVE: To determine the location in soft tissues of the calcifications, similar to calcified carotid atheromas, that can be observed radiographically in the cervical region in panoramic radiographs. STUDY DESIGN: In each anatomic cadaver specimen preserved in formol, consisting of the head and neck, radiopaque spheres (made from gutta-percha) were positioned in anatomic structures of the cervical region that can be sites of calcification. For each anatomic structure marked in this way, panoramic radiography was performed, consisting of 17 radiographs. The images obtained were analyzed by 24 examiners who indicated which radiographs, in their opinion, presented the radiopaque reference projected in the region of bifurcation of the carotid artery. Analysis of 2 proportions from agreement and disagreement was used to determine radiopacities that could be confused in panoramic radiographs with calcified atheromas in the carotid artery. RESULTS: The results showed that 75% (18) of the examiners correctly indicated the reference in the bifurcation of the carotid artery and 79.2% (19) indicated a triticeous cartilage as calcified atheroma of the carotid artery. CONCLUSIONS: Calcified atheromas of the carotid artery are not the only features that can produce radiopaque images lateral to the panoramic radiograph; the presence of calcification in the triticeous cartilage also can induce an erroneous diagnosis of calcified carotid atheroma.  相似文献   
55.
56.
Deficit in active and inhibitory avoidance behaviour has been found in pentylenetetrazole (PTZ)-kindled rats. This supports the view that memory deficit is an integral part of epilepsy. In the present study we examined the effect of the nootropic drugs piracetam and fipexide on memory deficit induced by PTZ-kindling in shuttle-box- and step-down-trained rats. The retention in piracetam- and fipexide-treated animals was significantly improved compared to the kindled controls. The mechanisms of action of the two drugs are considered. The favourable effects of nootropic drugs in cases of amnesia provoked by PTZ-kindling might be of interest in clinical practice.  相似文献   
57.
58.
采用SD大鼠一侧大脑中动脉阻断致局限性脑缺血模型。脑缺血后迅速断头置于液氮中,HPLC外标定量法测定各磷脂组分。观察脑缺血1、5、15、60、360min时脑细胞膜磷脂含量变化。结果显示,PI在缺血早期显著低于对照组(P<0.01~0.05);PE、PC早期仅呈下降趋势,PE在缺血60min组、PC缺血360min组显著低于对照组(P<0.01~0.05)。PS在缺血全过程中变化轻微(P>0.05)。提示磷脂降解与脑缺血存在一定关系,缺血早期首先出现脑细胞膜功能磷脂降解,膜结构磷脂则在缺血后期出现显著变化,且PE较PC优先降解。  相似文献   
59.
A computer-assisted method for the registration of food intakes in real time according to a concise and simple procedure was subjected to a series of controls in order to assess precision. The method employs the 'portion' of a composite dish as unit of measure. The constancy of the portion was tested. The results show that the recipes of the diet of a subject may be stored and utilized in deferred time without loss of precision: data to be recorded in real time are then very limited. The length of period of analysis was also studied. The time of investigation should not be shorter than two weeks to obtain precise information on the feeding habits of an individual subject, whereas for a group of subjects the diary of a single day provides information of sufficient precision.  相似文献   
60.
竹荪深层发酵菌丝体对小鼠免疫功能的影响及其抗肿瘤作用   总被引:12,自引:0,他引:12  
过对食药用真菌──竹荪深层发酵菌丝体提取液对小鼠免疫功能及S-180肿瘤细胞的作用观察,表明其发酵菌丝体可明显提高小鼠腹腔巨噬细胞的吞噬功能(P<0.01),并显著增加免疫器官的重量(P<0.05);对小鼠S-180肿瘤的抑瘤率为40.63%。  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