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   1278758篇
  免费   97807篇
  国内免费   1989篇
耳鼻咽喉   18423篇
儿科学   44351篇
妇产科学   35008篇
基础医学   182169篇
口腔科学   33585篇
临床医学   111248篇
内科学   258230篇
皮肤病学   28020篇
神经病学   100364篇
特种医学   51208篇
外国民族医学   660篇
外科学   196379篇
综合类   27048篇
现状与发展   1篇
一般理论   377篇
预防医学   95715篇
眼科学   27912篇
药学   94788篇
  2篇
中国医学   2424篇
肿瘤学   70642篇
  2018年   13133篇
  2017年   9962篇
  2016年   10897篇
  2015年   12372篇
  2014年   17164篇
  2013年   26214篇
  2012年   36020篇
  2011年   38052篇
  2010年   22798篇
  2009年   21806篇
  2008年   36635篇
  2007年   39246篇
  2006年   39505篇
  2005年   38441篇
  2004年   37592篇
  2003年   36446篇
  2002年   35794篇
  2001年   63988篇
  2000年   66497篇
  1999年   56412篇
  1998年   15128篇
  1997年   13755篇
  1996年   14196篇
  1995年   13455篇
  1994年   12767篇
  1993年   11791篇
  1992年   44556篇
  1991年   43467篇
  1990年   42219篇
  1989年   40112篇
  1988年   36898篇
  1987年   36236篇
  1986年   33620篇
  1985年   32279篇
  1984年   24138篇
  1983年   20269篇
  1982年   11725篇
  1981年   10692篇
  1980年   9517篇
  1979年   21344篇
  1978年   14821篇
  1977年   12532篇
  1976年   11693篇
  1975年   12623篇
  1974年   14662篇
  1973年   14118篇
  1972年   12946篇
  1971年   11729篇
  1970年   11050篇
  1969年   10025篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
Uniparental isodisomy (iUPD) is a rare genetic condition caused by non-disjunction during meiosis that ultimately leads to a duplication of either the maternal or paternal chromosome in the affected individual. Two types of disorders can result, those due to imprinted genes and those due to homozygosity of recessive disease-causing mutations. Here, we describe the third known case of complete chromosome 4 iUPD of maternal origin. This condition became apparent during whole genome linkage studies of psychiatric disorders in the Portuguese population. The proband is an adult female with normal fertility and no major medical complaints, but a history of major depressive disorder and multiple suicide attempts. The proband's siblings and parents had normal chromosome 4 genotypes and no history of mood disturbance. A brief review of other studies lends support for the possibility that genes on chromosome 4 might confer risk for mood disorders. We conclude that chromosome 4 maternal uniparental disomy (UPD) is a rare disorder that may present with a major depressive phenotype. The lack of a common disease phenotype between this and two other cases of chromosome 4 iUPD [Lindenbaum et al. [1991] Am J Med Genet 49(Suppl 285):1582; Spena et al. [2004] Eur J Hum Genet 12:891-898) would suggest that there is no vital maternal gene imprinting on chromosome 4. However, since there is no reported case of paternal chromosome 4 UPD, paternal gene imprinting on chromosome 4 cannot be excluded.  相似文献   
222.
OBJECTIVES: To identify and describe current women's thoughts about the menopause, hormone treatment (HT) and perceptions about breast cancer. METHODS: Between December 2004 and January 2005, 4201 postmenopausal women in seven European countries were interviewed via a standardized computer-aided telephone interview protocol. RESULTS: Almost all women reported to have experienced climacteric symptoms, and 63% of the women rated them as being severe. Only 52% of women were aware of the benefits of HT for relief of climacteric symptoms. Although 84% felt that severe symptoms should be treated, only 40% had used HT at some point in time. Thirty-four percent of the women preferring treatment with natural products did so because of the risk of breast cancer associated with HT. HT was recognized by 59% of the women as one of the most important contributors to an increased breast cancer risk. Most women received their information about HT and breast cancer risk from the media. CONCLUSIONS: This European survey reveals that the majority of women experience climacteric symptoms but that their decision whether or not to use HT is highly dependent on their concern about breast cancer risk. An increase in knowledge of the benefits and risks of HT is required for women to make appropriate decisions about hormone use.  相似文献   
223.
In order to assess the state and pathology of the woman's pelvis minor, a number of methods are commonly used among practitioners, encompassing clinical exploration, radiology, MRN, urodynamics, endoscopy and echography.

Echography has been poorly used in clinical pelvic exploration and its reliability is actually a matter of controversy 1. However, echographic surveys can provide us with valuable gynecological data on the state and pathologies of the soft pelvis, within the genital regions or even going beyond them, i.e. the rectal channel, bladder, urethra, anus, vascular plexuses, and all of their supporting tissues.

At our research unit, we have been employing Transvaginal Ultrasound echography (TVU) for a long time in conjunction with other pelvis-focused methods in order to study different kinds of pelvic alterations. TVU has proven to be friendly to use, fast, harmless and inexpensive, allowing serial explorations and producing high-quality dynamic images (loop-cinema, video-tape). Furthermore, this method is fairly aseptic in that the occurrence of faeces in the rectal ampolla is not a nuisance but a bonus in tracking the contours of the rectum walls and other topographical features which would be otherwise difficult to survey.

A complete pelvic floor TVU may add no longer than 5-8 minutes to a routine gynecological examination, can be implemented by the general gynecologist and generates data that can be further studied by the appropriate specialist for a more insightful evaluation 2.  相似文献   
224.
225.
Vascular malformation (AVM) in the gastrointestinal tract is an uncommon, but not rare, cause of bleeding and iron deficiency anemia, especially in an aging population. While endoscopic coagulative therapy is the method of choice for controlling bleeding, a substantial number of cases require additional therapy. Adjunctive or even primary phamacotherapy may be indicated in recurrent bleeding. However, there is little evidence-based proof of efficacy for any agent. The bulk of support is derived from anecdotal reports or case series. The present review compares the outcome of AVM after no intervention, coagulative therapy or focus on pharmacological agents. Most of the literature encompasses two common AVMs, angiodysplasia and hereditary hemorrhagic telangiectasia. Similarly, the bulk of information evaluates two therapies, hormones (estrogen and progesterone) and the somatostatin analogue octreotide. Of these, the former is the only therapy evaluated in randomized trials, and the results are conflicting without clear guidelines. The latter therapy has been reported only as case reports and case series without prospective trials. In addition, other anecdotally used medications are discussed.  相似文献   
226.
Conclusions Limitation of this analysis is participation of limited centers. Though all the regions of the country are represented total number of procedures reported are less. Isolated CABG is commonest procedure performed in 2004. Congenital surgical procedures are more than the valvular heart disease procedure. For appropriate categorization we need standard nomenclature for various congenital surgical procedures.  相似文献   
227.
Eighty-nine first-degree relatives of 22 patients with an established diagnosis of hypertrophic cardiomyopathy underwent electrocardiographic and echocardiographic screening. Scalar electrocardiogram was abnormal in 30/89 (33.7%) relatives. Of these thirty, eleven had definite evidence of hypertrophic cardiomyopathy at echo; one had borderline hypertrophy and was considered neither affected nor unaffected; four had questionable signs of hypertrophy. The remaining 14 relatives had normal echo-cardiograms. Fifty-nine relatives (66.3%) had normal electrocardiograms; at echo 3 were considered to have borderline hypertrophy, 16 had questionable signs of hypertrophy and 40 were normal. In relatives of patients with hypertrophic cardiomyopathy an abnormal electrocardiogram may reflect different morphologic conditions: a real hypertrophic cardiomyopathy or a myocardial hypertrophy of uncertain significance. Furthermore, in these categories of subjects, an abnormal electrocardiogram with normal echo must be considered with caution.  相似文献   
228.
229.
To assess the vascular involvement of renin-angiotensin system inhibition in human hypertension, acute effects of intravenous enalaprilat on brachial artery diameter, blood flow, and blood velocity were investigated in hypertensive patients by pulsed Doppler technique and compared with effects of saline vehicle. Compared with saline vehicle, enalaprilat reduced blood pressure (P less than 0.001) and increased brachial arterial diameter (P less than 0.01) and brachial blood flow (P less than 0.01). Enalaprilat effect on arterial pulse pressure was dependent on preinjection pulse pressure (r = -0.76; P less than 0.001), but its effect on mean blood pressure was not dependent on preinjection mean blood pressure. On the other hand, enalaprilat effect on arterial blood flow was negatively correlated with preinjection blood pressure (r = -0.64; P less than 0.02). The findings point to different responses of large and small arteries to intravenous enalaprilat.  相似文献   
230.
Summary To evaluate the potential effect of androgens on the development and growth of human colorectal adenomas, the prevalence and concentration of cytosolic androgen receptors (AR) were analysed in 26 adenomas and 19 samples of normal colonic mucosa by a hybrid ligand receptor-binding assay. AR were detected in 7 of the adenomas (26.9%), and in 6 of the normal mucosa samples (31.6%). In the adenomas, AR levels demonstrated were low, ranging from 6 to 31 fmol/mg cytosol protein, and dissociation constants (Kds) ranged from 0.17–2.7x10-9 M. Of 13 adenomas excised from men, 6 (46%) had positive receptor activity, whereas only 1 of 13 (7.7%) from women was positive (P=0.03, Fisher's exact test). There was no correlation between AR titre and patient age, or between adenoma size and histological type or degree of dysplasia. In normal mucosa, AR levels ranged from 7 to 33 fmol/mg and Kds ranges from 0.24–3.1x10-9 M. There was no significant difference between either AR prevalence or levels in the adenomas and normal mucosa. The sex difference was exclusive to the adenoma. Endogenous androgen may play a role in adenoma development early in the promotional process.  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