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   1749794篇
  免费   129241篇
  国内免费   4788篇
耳鼻咽喉   22783篇
儿科学   57148篇
妇产科学   47919篇
基础医学   265012篇
口腔科学   48403篇
临床医学   165231篇
内科学   332543篇
皮肤病学   36449篇
神经病学   141387篇
特种医学   63459篇
外国民族医学   423篇
外科学   248080篇
综合类   36190篇
现状与发展   1篇
一般理论   570篇
预防医学   145860篇
眼科学   39289篇
药学   131342篇
  6篇
中国医学   3989篇
肿瘤学   97739篇
  2019年   14312篇
  2018年   19949篇
  2017年   15109篇
  2016年   16401篇
  2015年   18709篇
  2014年   25650篇
  2013年   39760篇
  2012年   54397篇
  2011年   58099篇
  2010年   33827篇
  2009年   31203篇
  2008年   53720篇
  2007年   56855篇
  2006年   57271篇
  2005年   55199篇
  2004年   52961篇
  2003年   50372篇
  2002年   49038篇
  2001年   79523篇
  2000年   82076篇
  1999年   68490篇
  1998年   19035篇
  1997年   17130篇
  1996年   17214篇
  1995年   16247篇
  1994年   15157篇
  1993年   14294篇
  1992年   54079篇
  1991年   53674篇
  1990年   52541篇
  1989年   50054篇
  1988年   46399篇
  1987年   45385篇
  1986年   43223篇
  1985年   41307篇
  1984年   30953篇
  1983年   26342篇
  1982年   15550篇
  1979年   28607篇
  1978年   20496篇
  1977年   16871篇
  1976年   16502篇
  1975年   17406篇
  1974年   21156篇
  1973年   20435篇
  1972年   19268篇
  1971年   18119篇
  1970年   16753篇
  1969年   15500篇
  1968年   14664篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
931.
932.
933.
Ambient light affects pulse oximeters   总被引:1,自引:0,他引:1  
  相似文献   
934.
935.
Previously, we reported that short term administration of a highly potent GnRH agonist (GnRHa) for 1 month to patients with polycystic ovarian disease (PCO) resulted in complete suppression of ovarian steroidogenesis without measurable effects on adrenal steroid production. This new study was designed to evaluate the effects of long term GnRHa administration in PCO patients with respect to their hormone secretion patterns and clinical responses. Eight PCO patients and 10 ovulatory women with endometriosis were treated daily with sc injections of [D-His6-(imBzl]),Pro9-NEt]GnRH (GnRHa; 100 micrograms) for 6 months. Their results were compared to hormone values in 8 women who had undergone bilateral oophorectomies. In response to GnRHa, PCO and ovulatory women had rises of serum LH at 1 month, after which it gradually declined to baseline. In both groups FSH secretion was suppressed throughout treatment. Serum estradiol, estrone, progesterone, 17-hydroxyprogesterone, androstenedione, and testosterone levels markedly decreased to values found in oophorectomized women by 1 month and remained low thereafter. In contrast, serum pregnenolone and 17-hydroxypregnenolone were partially suppressed, and dehydroepiandrosterone, dehydroepiandrosterone sulfate, and cortisol levels did not change. Clinically, hyperplastic endometrial histology in three PCO patients reverted to an inactive pattern, and proliferative endometrium in two other PCO patients became inactive in one and did not change in the other. Regression of proliferative endometrial histology occurred in all ovulatory women. Vaginal bleeding occurred in all women studied during the first month of GnRHa administration, after which all but one PCO patient became amenorrheic. Hot flashes were noted by all ovulatory women and by four of eight PCO patients. All PCO patients noted subjective reduction of skin oiliness, and five had decreased hair growth. We conclude that in premenopausal women: 1) chronic GnRHa administration results in apparently complete persistent suppression of ovarian steroid secretion; 2) adrenal steroid secretion is not influenced directly or indirectly; and 3) its use may be helpful in the treatment of endometrial hyperplasia and ovarian androgen excess in women with PCO.  相似文献   
936.
The authors report a case of massive haemolytic anaemia with acute mitral valve regurgitation and left cardiac failure, which occurred one year after surgical reconstruction of the mitral valve for rupture of smaller leaflet chordae. Anaemia, mitral regurgitation and cardiac failure disappeared after mitral valve replacement, using a Carpentier Edwards No. 29 valve. Haemolytic anaemia following mitral valve reconstruction is exceptional. It seems to be due to the suture material lying in a turbulent regurgitation stream when mitral incompetence develops again.  相似文献   
937.
Positron emission tomography (PET) with fluorodeoxyglucose (FDG), magnetic resonance imaging (MRI), and CT were carried out in a patient with Alzheimer's disease 16 months before he died. At autopsy, the gross appearance of the brain correlated with MRI and CT, which showed some regional atrophy. These were much less revealing than PET, which correlated with microscopic findings of neuronal loss and proliferation of glia. In areas of moderately impaired local cerebral metabolic rate of glucose, as revealed by reduced FDG uptake, there was some gliosis, primarily around the numerous senile plaques. In areas of severe metabolic impairment, there was a profound loss of neurons, extensive gliosis, and a diminished appearance of plaques. PET-FDG is a better measure of the severity of Alzheimer's disease than MRI or CT, because it reflects the degree of neuronal pathology.  相似文献   
938.
The cellular mechanisms by which pepsinogen (PNG) secretion is controlled are not understood. The aim of this study was to explore whether modulation of PNG secretion is mediated by cAMP or calcium-calmodulin (C-C). PNG secretion in isolated rabbit gastric fundic glands (IGG) was tested, using agents believed to act via cAMP or C-C. IGG were stimulated for 30 minutes with histamine (H) 10(-5) M, isoproterenol (I) 10(-5) M, carbachol (C) 10(-5) M, cholecystokinin-octapeptide (CCK-8) 10(-7) M, forskolin (F) 10(-5) M, 8 bromo-cAMP (8B) 10(-3) M, and A23187 (A) 10(-6) M. PNG levels were determined by spectrophotometric assay of hemoglobin digestion products. PNG amounts secreted were (mean per cent above basal levels of total IGG PNG units +/- SEM): H, -0.02 +/- 0.30%; I, 3.5 +/- 0.9%; C, 5.1 +/- 2.2%; CCK-8, 5.3 +/- 1.5%; F, 10.6 +/- 3.8%; 8B, 13.8 +/- 4.5%; A, 2.1 +/- 1.1%. All secretagogues except H stimulated PNG release significantly above basal levels (p less than 0.05). A primary histaminergic mechanism for pepsinogen secretion is unlikely. Since two other adenylate cyclase activators, isoproterenol and forskolin and the 3':5'-cyclic adenosine monophosphate analog 8-bromo cAMP stimulated pepsinogen secretion, cAMP-dependence is probable. Since carbachol, CCK-8, and A23187, which are believed to act via calcium-calmodulin, also stimulated pepsinogen secretion, this system, too, presumably plays a substantial role. Thus the data support a dual 3':5'-cyclic adenosine monophosphate/calcium-calmodulin modulation of pepsinogen secretion.  相似文献   
939.
Sub-trigonal phenol injection ensures a satisfactory response in about 50% of patients with detrusor instability. When oral anticholinergic treatment is poorly tolerated or ineffective, this minimally invasive technique has been found, in our series of 11 patients, to be a useful adjunct, at least temporarily.  相似文献   
940.
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