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   11035篇
  免费   517篇
  国内免费   29篇
耳鼻咽喉   147篇
儿科学   165篇
妇产科学   150篇
基础医学   1547篇
口腔科学   331篇
临床医学   709篇
内科学   2386篇
皮肤病学   116篇
神经病学   716篇
特种医学   963篇
外科学   1708篇
综合类   61篇
预防医学   277篇
眼科学   130篇
药学   905篇
中国医学   16篇
肿瘤学   1254篇
  2022年   79篇
  2021年   152篇
  2020年   74篇
  2019年   116篇
  2018年   160篇
  2017年   116篇
  2016年   154篇
  2015年   162篇
  2014年   191篇
  2013年   260篇
  2012年   368篇
  2011年   463篇
  2010年   266篇
  2009年   255篇
  2008年   424篇
  2007年   450篇
  2006年   465篇
  2005年   495篇
  2004年   496篇
  2003年   483篇
  2002年   457篇
  2001年   459篇
  2000年   472篇
  1999年   434篇
  1998年   156篇
  1997年   119篇
  1996年   128篇
  1995年   91篇
  1994年   83篇
  1993年   68篇
  1992年   335篇
  1991年   288篇
  1990年   305篇
  1989年   329篇
  1988年   286篇
  1987年   289篇
  1986年   243篇
  1985年   243篇
  1984年   156篇
  1983年   104篇
  1982年   55篇
  1981年   48篇
  1979年   76篇
  1978年   69篇
  1977年   65篇
  1976年   44篇
  1974年   59篇
  1972年   55篇
  1970年   49篇
  1968年   44篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
In order to find the three-dimensional distribution of ventricular depolarization potentials in left anterior hemiblock (LAHB) diagnosed by the conventional scalar ECG, 7 subjects with LAHB aged 9 to 62 years old who were otherwise healthy were studied by computer graphic electrocardiography (CGECG).Two modes of the initial ventricular depolarization (IVD) were noted. (1) The IVD appeared irregularly and separately on the mid- to lower central region of the anterior body surface. (2) The IVD appeared in a form rather like a parallelogram on the central region of the anterior body surface. Both (1) and (2) potentials propagated toward the left middle, lower, and lateral regions of the anterior body surface as normally observed; however, they were far lower in voltage than those observed in intact subjects.From the results, it has been concluded that LAHB may be, not a block, but rather a defective ventricular septal conduction.Presented at the 34th Annual Congress, International College of Angiology, Budapest, Hungary, July 1992.  相似文献   
52.
A case of retroperitoneal venous aneurysm is reported. A 73-year-old woman was referred to us with the chief complaint of left abdominal mass. A giant abdominal mass was palpable and diagnostic imaging examination including ultrasound tomography, excretory pyelography, computed tomography, magnetic resonance imaging and angiography revealed a giant cystic mass encircled by calcification in the left retroperitoneal space. Operation for this cystic mass was performed under the preoperative diagnosis of a giant left renal cyst. During operation the mass was located between the left kidney and the left adrenal gland. Because it was difficult to separate the mass from the left kidney the mass was removed with the left kidney. The extirpated tumor measured 15.5 x 15.0 x 9.5 cm and contained old blood clots and red-yellow colored fluid. A histological examination revealed that the tumor wall was composed of smooth muscle and elastic fibers. Therefore, pathological diagnosis was retroperitoneal venous aneurysm. Retroperitoneal venous aneurysm is very rare. To our knowledge, this is the 8th case of retroperitoneal venous aneurysm reported in Japan.  相似文献   
53.
H Makino  S Nishimura  M Takaoka  Z Ota 《Nephron》1988,50(2):142-150
A model of hematuria was established in rabbits. An accelerated form of unilateral Masugi nephritis was induced in 10 New Zealand white rabbits by an intravenous injection of duck antirabbit kidney serum and by ligating the left renal artery immediately after the injection of the antibody. All 10 rabbits became hematuric 1-2 weeks after the injection of the antibody and red blood cell (RBC) casts were found in the urinary sediment of all these animals. An ultrastructural examination of renal glomeruli by transmission electron microscopy revealed the transcapillary passage of polymorphonuclear leukocytes through the gaps of the glomerular basement membrane (GBM). RBC were found in the urinary space in 50% of the glomeruli observed by scanning electron microscopy (SEM) and the passage of leukocytes and RBCs through the glomerular capillary wall was also observed. Gaps in the GBM became clearer after the removal of cellular components by detergents. In control rabbits, no RBCs could be observed in the urinary space, and isolated GBM were intact by SEM. These data further support the hypothesis that in rabbit Masugi nephritis hematuria is a result of the passage of RBCs through gaps in the GBM.  相似文献   
54.
The antiinflammatory activity of 4-acetylaminophenylacetic acid (MS-932) was investigated. MS-932 did not suppress the acute inflammation of carrageenin-induced paw edema in rats or of primary swelling in adjuvant arthritic rats. However, prophylactic treatment with MS-932 inhibited secondary inflammation in adjuvant arthritic rats. MS-932 also restored to normal the weight of the spleen and the serum albumin/globulin ratio of adjuvant arthritic rats. In addition to its prophylactic effect, MS-932 had a therapeutic effect on adjuvant arthritis. In in vitro tests, MS-932 did not inhibit prostaglandin E2 biosynthesis from arachidonic acid by sheep seminal vesicle microsomal enzyme or superoxide generation by guinea pig neutrophils stimulated with opsonized zymosan. MS-932 had no analgesic effect in mice and no antipyretic effect in rats. These results indicate that MS-932 suppresses adjuvant arthritis through modulation of the immune system.  相似文献   
55.
Ultrashort echo time (UTE) imaging is a technique that can visualize tissues with sub-millisecond T(2) values that have little or no signal in conventional MRI techniques. The short-T(2) tissues, which include tendons, menisci, calcifications, and cortical bone, are often obscured by long-T(2) tissues. This paper introduces a new method of long-T(2) component suppression based on adiabatic inversion pulses that significantly improves the contrast of short-T(2) tissues. Narrow bandwidth inversion pulses are used to selectively invert only long-T(2) components. These components are then suppressed by combining images prepared with and without inversion pulses. Fat suppression can be incorporated by combining images with the pulses applied on the fat and water resonances. Scaling factors must be used in the combination to compensate for relaxation during the preparation pulses. The suppression is insensitive to RF inhomogeneities because it uses adiabatic inversion pulses. Simulations and phantom experiments demonstrate the adiabatic pulse contrast and how the scaling factors are chosen. In vivo 2D UTE images in the ankle and lower leg show excellent, robust long-T(2) suppression for visualization of cortical bone and tendons.  相似文献   
56.
Detection of myocardial ischemia by the stress thallium scan has traditionally been performed using transient defect analysis on exercise, followed by redistribution studies. Worsening of the 201Tl myocardial image from exercise to redistribution is referred to as reverse redistribution. In this study, we found reverse redistribution in 10 (21%) of 48 angina pectoris patients who had undergone aortocoronary bypass surgery. The clinical significance of this phenomenon in these patients was investigated in relation to angiographic and surgical findings. Reverse redistribution was found to occur in regions which were supplied by bypass grafts. These areas showed increased coronary blood flow and rapid thallium washout. Our results indicate that a perfusion defect in the bypass region of the redistribution image might be caused by relatively rapid washout in the bypass graft region compared to the adjacent normal myocardium. These results should be considered in the clinical interpretation of stress thallium scans.  相似文献   
57.
A case of malignant fibrosarcoma originated from pericardium was reported. A 31 year-old female who complained of general fatigue and back pain showed dilated cardiac shadow in chest X-ray. Cardiac blood pool scan with 99mTc-RBC revealed avascular mass in pericardial cavity which push the heart up and left side. It was suspected to be malignant, since the mass had increased 67Ga uptake. CT and MRI also demonstrated that the tissue characterization of the pericardial mass was irregular, and the mass compressed venous return. The large mass originated from pericardium caused the right sided cardiac failure. In 12 years ago, she had a history of operation which resected benign hemangioma in the same space (pericardium). We could suspect the malignant transformation between the two rare pericardial tumors; benign hemangioma and malignant fibrosarcoma.  相似文献   
58.
Extracellular single-unit activity was recorded from 21 median preoptic nucleus (MnPO) neurones, antidromically identified as projecting to the hypothalamic paraventricular nucleus (PVN), in urethane-anaesthetized male rats. Of these identified MnPO neurones, 14 displayed an excitatory response in neuronal excitability following electrical stimulation (5 Hz, 600 microA) of the A1 noradrenergic region of the ventrolateral medulla, while the remaining neurones were unresponsive. The excitatory response of MnPO neurones was blocked by microiontophoretically applied phentolamine, an alpha-adrenoceptor antagonist, but not by timolol, a beta-adrenoceptor antagonist. These results suggest that the A1 region acts to enhance the activity of MnPO neurones projecting to the PVN via an alpha-adrenoceptor mechanism.  相似文献   
59.
As a part of our studies on cephalosporins bearing condensed-heterocyclic azolium methyl groups at the 3 position in the cephalosporin nucleus, we describe here the synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)2(Z)-methoxyiminoacetamido] cephalosporins (1-16, 7 beta-[2-(2-amino-5-chlorothiazol-4-yl)-2(Z)- methoxyiminoacetamido] cephalosporins (17,18) and 7 beta-[2-(5-amino- 1,2,4-thiadiazol-3-yl)-2(Z)-methoxyiminoacetamido) cephalosporins (19-23) containing a variety of condensed-heterocyclic triazolium methyl groups at the 3 position in the cephalosporin nucleus. These cephalosporins exhibited potent antibacterial activity, and it appears that condensed-heterocyclic triazolium as well as condensed-heterocyclic imidazolium rings are effective moieties for improving antibacterial activity and the spectrum of activity. Among the cephalosporins tested, 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(5- methyl[1,2,3]triazolo-[1,5-alpha]pyridinium-1-yl)methyl-3-cephem-4- carboxylate (9) and 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(6- methoxy[1,2,4]triazolo[1,5-alpha]pyridinium-1-yl)methyl-3-cephem-4- carboxylate (11) showed good antibacterial activity.  相似文献   
60.
Ectopic pituitary adenomas are very rare and only 17 cases have been reported. In this paper we present a case of large pituitary adenoma originating in the suprasellar region. A 26-year-old man was admitted to our clinic with a chief complaint of headaches. Neurological examination revealed slight disorientation and bilateral choked disk. Hormonal study revealed that the serum prolactin level was 3300ng/ml and serum growth hormone level was 29.5ng/ml. Computed tomography showed a large mass in the suprasellar region extending upward to the third ventricle and backward to the pons. T1-weighted MR imaging revealed that the intensity of the mass was the same as that of the cerebral cortex and the pituitary gland was showing high intensity in the pituitary fossa. The tumor was radically removed via the transpetrosal transtentorial approach. Histologically, the tumor was a prolactin-growth hormones producing pituitary adenoma. The literature was reviewed and the origin of the tumor was discussed.  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