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   41425篇
  免费   4732篇
  国内免费   154篇
耳鼻咽喉   863篇
儿科学   1124篇
妇产科学   1009篇
基础医学   2925篇
口腔科学   3139篇
临床医学   5854篇
内科学   8485篇
皮肤病学   777篇
神经病学   3459篇
特种医学   1901篇
外国民族医学   25篇
外科学   6018篇
综合类   198篇
现状与发展   12篇
一般理论   6篇
预防医学   4673篇
眼科学   527篇
药学   1744篇
中国医学   62篇
肿瘤学   3510篇
  2024年   209篇
  2023年   1218篇
  2022年   556篇
  2021年   895篇
  2020年   1386篇
  2019年   720篇
  2018年   1618篇
  2017年   1508篇
  2016年   1757篇
  2015年   1863篇
  2014年   2339篇
  2013年   2909篇
  2012年   1551篇
  2011年   1547篇
  2010年   1799篇
  2009年   2390篇
  2008年   1504篇
  2007年   1237篇
  2006年   1413篇
  2005年   1197篇
  2004年   998篇
  2003年   950篇
  2002年   878篇
  2001年   938篇
  2000年   869篇
  1999年   868篇
  1998年   700篇
  1997年   631篇
  1996年   657篇
  1995年   540篇
  1994年   488篇
  1993年   514篇
  1992年   760篇
  1991年   695篇
  1990年   580篇
  1989年   440篇
  1988年   408篇
  1987年   399篇
  1986年   329篇
  1985年   367篇
  1984年   280篇
  1983年   239篇
  1982年   205篇
  1981年   189篇
  1979年   200篇
  1977年   170篇
  1976年   167篇
  1975年   171篇
  1974年   206篇
  1973年   171篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Little is known about oral health care behaviors of community-dwelling, cognitively impaired elderly (CIE) persons. Few studies have been conducted regarding the actual provision of oral care for CIE persons or the attitudes and concerns about oral health among their caregivers. The CIE person's ability to perform self-care decreases over time, and the role of the caregiver in daily oral care becomes increasingly important. The purpose of this pilot study was to explore the attitudes toward oral health and identify related concerns among caregivers who care for community-dwelling CIE persons. Caregivers were surveyed by means of a self-administered, mailed questionnaire. To maintain confidentiality, an intermediary was used for recruitment and data collection. Overall, 148 caregivers were invited by an intermediary to participate in the survey; only 21 (14%) consented to participate and returned the questionnaire. This paper discusses some of the numerous methodological challenges identified when an attempt was made to survey caregivers' attitudes toward and barriers to providing oral care for a dependent CIE.  相似文献   
52.
Electromyographic (EMG) recordings were obtained by concentric needle electrodes from the bulbocavernosus (BC) and ischiocavernosus (IC) muscles in 7 human volunteers during excitement to erection and subsequent ejaculation. Simultaneous registration of the time course and volume of each expressed spurt of semen was obtained using an aluminium pan suspended in front of the subject's penis on a force transducer the output of which was charted with the EMG activity. The BC and IC muscles showed no EMG activity during erection and detumescence cycles induced by visual sex stimulation. In 5 of 7 subjects, the first EMG burst of the BC in ejaculations induced by masturbation was not correlated with an expelled spurt of semen as were subsequent bursts. However, only 26 to 60% of the total number of EMG bursts were accompanied by expulsion of a spurt of semen. There thus appears to be a large safety factor in the striated muscle expulsive mechanism. Oral phenoxybenzamine treatment in 2 subjects did not significantly affect either the number of EMG bursts of the BC or the subjective pleasure of the orgasm but did significantly reduce the volume of semen expelled. Semen volume does not appear to be a unique determinant of the pleasure felt or the trigger for ejaculation.  相似文献   
53.
In a double-blind, randomized, placebo-controlled cross-over study, we investigated in seven patients with chronic renal failure the effect of conjugated estrogens (0.6 mg/kg/day for 5 days) on template bleeding time and on thromboxane A2 (TxA2), beta-thromboglobulin (beta-TG) and prostacyclin (PGI2) concentrations in blood emerging from the template bleeding time incisions. Administration of conjugated estrogens resulted in a significant shortening of the bleeding time in six out of seven patients with a maximum effect 7 and/or 14 days following treatment. Both TxA2 (measured as thromboxane B2, TxB2) and beta-TG release in bleeding time blood were significantly higher following administration of conjugated estrogens as compared to placebo administration. No difference was seen in endothelial PGI2 (measured as 6-keto-prostaglandin F1 alpha) formation when patients were treated with conjugated estrogens as compared to placebo administration over the 28 day observation period. We conclude that in patients with chronic renal failure, infusion of conjugated estrogens results in a significant shortening of the bleeding time together with an increase in platelet reactivity, as indicated by an increase of TxA2 and beta-TG concentration in the microvasculature. No effect was seen on PGI2 production, thereby excluding a major effect on vascular prostaglandin metabolism.  相似文献   
54.
55.
56.
The leading cause of postoperative morbidity in patients undergoing major head and neck surgical procedures is postoperative infection. This prospective randomized multi-institutional clinical trial was designed to compare the effectiveness of clindamycin phosphate and high-dose cefazolin sodium therapy in preventing postoperative wound sepsis in patients undergoing contaminated head and neck surgical procedures in which flap reconstruction was required. Either clindamycin phosphate (900 mg) or cefazolin sodium (2 g) therapy was instituted intravenously prior to surgery and continued every 8 hours, for a total of 24 hours. The patients received postoperative follow-up, and the wounds were graded according to the worst condition observed. One hundred cases were evaluated. Fifty-one patients received clindamycin and 49 patients received high doses of cefazolin; wound infection developed in 10 patients (19.6%) and 11 patients (21.6%), respectively. This difference was not statistically significant. The average duration of surgery was approximately 8 hours for both the infected and the noninfected groups of patients. High-dose cefazolin and clindamycin have similar efficacy when administered prophylactically under these circumstances. Reconstruction with free vascularized tissue may aid in reducing postoperative wound infection.  相似文献   
57.
Background: Investigators in the authors' laboratory previously established the critical participation of the cerulospinal noradrenergic pathway in muscular rigidity elicited by fentanyl. The identification of colocalization of glutamate with tyrosine hydroxylase in most locus ceruleus neurons suggests a role for cerulospinal glutamatergic neurotransmission in fentanyl-induced muscular rigidity. This suggestion and the subtype(s) of glutamate receptors involved were investigated here.

Methods: Electromyographic signals activated by bilateral microinjection of 2.5 micro gram fentanyl into the locus ceruleus were recorded differentially from the left sacrococcygeus dorsi lateralis muscle of adult male Sprague-Dawley rats. The effect of intrathecal administration at the lower lumbar spinal cord of various N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists or agonists on this index of muscular rigidity was studied. Rats were under mechanical ventilation, and intravenous infusion of ketamine (30 mg [center dot] kg sup -1 [center dot] h sup -1) was maintained until 10 min before fentanyl was administered.

Results: Microinjection of fentanyl bilaterally into the locus ceruleus increased the root mean square and decreased the mean power frequency values of electromyographic signals. The efficacy of fentanyl to elicit muscular rigidity in this manner was significantly reduced by previous intrathecal administration of either 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801), D-(-)-2-amino-5-phosphonovaleric acid (AP5), or (+/- (CPP). Intrathecal administration of kainic acid or NMDA also resulted in significant electromyographic activation.  相似文献   

58.
Epiderrnolysis bullosa (EB), a heterogeneous group of rare, inherited disorders, is manifested by recurrent blistering of the skin induced by the slightest trauma. Little information exists regarding the nutrition management of patients with EB. This study presents information on growth, identifies potential nutrition problems, and provides guidelines for nutrition management of persons with EB. Eighty patients attending a dermatology clinic for EB patients are described. Severity of disease ranged from mild blistering of the knees, elbows, and feet to extensive blistering and scarring of the skin and entire gastrointestinal tract. Of the 18 children with EB simplex, which is a mild form of the disease, 4 (22%) were at nutritional risk. None of the 13 adults with EB simplex were underweight and 8 (62%) were overweight. Of the patients with the more severe forms of EB, 27 of the 35 (77%) children with dystrophic EB and 4 of the 7 (57%) children with junctional EB were at risk for malnutrition. Of the 7 adults with dystrophic EB, 6 (86%) were underweight. Common nutrition problems included protein-energy malnutrition, chewing and swallowing problems, constipation, anemia, and vitamin/mineral deficiencies. When nutrition care protocols address these problems, growth, development, and nutritional status can improve. For those with severe nutrition problems, gastrostomy feeding or similar nutrition therapies should be considered. J Am Diet Assoc. 1995; 95:575-579.  相似文献   
59.
A 5-Year experience of 51 endoscopic transthoracic dorsal sympathectomies for idiopathic palmar hyperhidrosis in 26 patients is presented. Fifty-two percent complained of excessive sweating over their hands, 28% of axillary sweating and 20% over both areas, with a mean duration of 10 years. The second, third and fourth thoracic ganglia and their interconnecting fibres on the affected side were ablated using diathermy cautery. Over a mean follow up time of 26 months, this procedure was successful in curing or improving intractable sweating in 92%. However, axillary sweating was less well controlled than in the palms with 20% of patients describing residual wetness in the axilla. Compensatory sweating (75%) and gustatory sweating (48%) were the commonest side effects; despite this, most patients were satisfied with the functional and cosmetic outcome. Other complications included a temporary Horner's syndrome in one patient, a pneumothorax in the immediate post-operative period in another and a unilateral non-infective reactionary pleural effusion in a third. Two patients developed recurrence of palmar hyperhidrosis within 6 months of surgery. One has been successfully treated by re-operation on the affected side. All patients complained of mild to moderate interscapular chest pain which was easily controlled by non-steroidal anti-inflammatory agents, and resolved within 7–10 days post-operatively. The technique of endoscope transthoracic sympathectomy is effective, relatively simple to perform and usually requires only an overnight stay. It is recommended as the surgical treatment of choice for upper limb hyperhidrosis unresponsive to conservative measures.  相似文献   
60.
Perceptions of family cohesion and hierarchy structures were assessed by theFamily System Test (FAST), a clinically-derived figure placement technique. Parents (N=140) and their preadolescent offspring (N=70) completed typical and conflict representations in individual as well as group settings. Typical representations were characterized by balanced family structures (i.e. cohesive and moderately hierarchical) and those displaying conflict situations showed predominantly unbalanced patterns. FAST portrayals were related to respondent (mother vs. father vs. child). Fathers represented typical family relations as balanced more often than mothers. Regarding conflict representations, children were more likely than fathers to portray the family as unbalanced. However, analyses of representations of the same family (i.e. intra-family comparisons) indicated that all respondents differed in their perceptions and, that fathers' typical portrayals showed most often the same structure as those done by the family members as a group.  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