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   15340篇
  免费   753篇
  国内免费   70篇
耳鼻咽喉   118篇
儿科学   182篇
妇产科学   172篇
基础医学   1883篇
口腔科学   358篇
临床医学   965篇
内科学   3454篇
皮肤病学   1089篇
神经病学   1557篇
特种医学   618篇
外科学   2517篇
综合类   94篇
预防医学   402篇
眼科学   136篇
药学   1431篇
中国医学   38篇
肿瘤学   1149篇
  2022年   117篇
  2021年   225篇
  2020年   130篇
  2019年   173篇
  2018年   243篇
  2017年   183篇
  2016年   257篇
  2015年   264篇
  2014年   339篇
  2013年   367篇
  2012年   605篇
  2011年   610篇
  2010年   357篇
  2009年   300篇
  2008年   622篇
  2007年   664篇
  2006年   630篇
  2005年   626篇
  2004年   663篇
  2003年   660篇
  2002年   635篇
  2001年   582篇
  2000年   654篇
  1999年   617篇
  1998年   237篇
  1997年   159篇
  1996年   158篇
  1995年   143篇
  1994年   116篇
  1993年   101篇
  1992年   439篇
  1991年   387篇
  1990年   399篇
  1989年   419篇
  1988年   397篇
  1987年   367篇
  1986年   318篇
  1985年   285篇
  1984年   168篇
  1983年   150篇
  1982年   82篇
  1979年   163篇
  1978年   81篇
  1977年   83篇
  1975年   68篇
  1974年   71篇
  1973年   80篇
  1972年   85篇
  1970年   75篇
  1969年   69篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Summary The authors describe an approach through the temporal horn of the lateral ventricle which proved to be useful for clipping of a large dorsal type basilar bifurcation aneurysms. It facilitates the preservation of the perforating arteries behind the aneurysm, because it gives sufficient working space to move the aneurysm dome. Furthermore this approach avoids many of the disadvantages of other approaches, especially the risk of iatrogenic injuries of the Sylvian or Labe's vein.  相似文献   
82.
C Kim  H Kikuchi  N Hashimoto  F Hazama 《Neurosurgery》1990,27(5):715-9; discussion 719-20
Five cynomolgus monkeys treated with unilateral carotid ligation, renal hypertension, and beta-aminopropionitrile feeding were studied repeatedly by cerebral angiography to clarify the growth process of saccular cerebral aneurysms. Repeated angiography demonstrated saccular cerebral aneurysms in three of five monkeys; two aneurysms were found 15 months and a third 12 months after the operation. At autopsy, one saccular aneurysm was found to be bilocular in shape, and the others were unilocular. Fusiform aneurysms were also observed in four monkeys. Microscopic studies revealed the walls of the saccular aneurysms were very thin and consisted of fibrous tissue. In one aneurysm, the aneurysmal sac was almost obstructed by a well-organized thrombus. No evidence of intramural hemorrhage was found in any of the saccular cerebral aneurysms. The conversion of early aneurysmal changes into saccular aneurysms was found to occur abruptly, and no consistent growth rate was noted. The multiloculation of saccular aneurysms was closely related to the size of an aneurysm. The present study indicates that a saccular cerebral aneurysm may grow abruptly from one of several different kinds of early aneurysmal changes.  相似文献   
83.
Pathological and experimental studies have shown that cerebral aneurysms develop in part as a result of injury to the blood vessel wall. One of the peculiar aspects of aneurysm development is a defective proliferative or healing response to such injury. To examine this phenomenon, blood coagulation Factor XIII, which is known to enhance the healing process of wounds in general, was given to rats to induce experimental cerebral aneurysms. The rats were subjected to ligation of one common carotid artery and induction of hypertension, and were fed beta-aminoproprionitrile. Two weeks thereafter, Factor XIII was injected intravenously daily for 5 days (10 U/100 gm body weight/day). Twelve days after the start of Factor XIII injections, the rats were sacrificed and examined under light and electron microscopy. In seven of 12 bifurcations which developed small aneurysms, prominent intimal thickening was observed in the aneurysm lumen. In the most advanced cases, the aneurysm lumen was completely filled with proliferated smooth-muscle cells and collagen. In five of nine bifurcations that showed no aneurysm development, apparent intimal thickening was found at the site where aneurysms might be expected to grow. In the group of rats studied for induction of cerebral aneurysms but not given Factor XIII, none of 11 bifurcations with or without aneurysms showed such intimal thickening. The results indicated that the proliferative response at the sites of aneurysm development was modified by exogenous Factor XIII.  相似文献   
84.
Previous studies using primary monolayer cultures of epithelial cells from the involved epidermis of patients with mammary and extramammary Paget's disease investigated whether Paget cells proliferate as other malignant cells do. Although epithelial monolayers from the involved skin were maintained for approximately 45 days, no permanent cell lines were established. The proportion of carcinoembryonic antigen (CEA)-positive cells did not increase in the long-term cultures. Herein, we report studies of whether there is a real reduction of Paget cell numbers or if this is merely a decrease in the expression of CEA by the cells. Furthermore, we investigated whether Paget cells survive longer when cultured free from any potential inhibitory keratinocytes or other epidermal cells. Skin samples were obtained from one patient with mammary Paget's disease and three with extramammary Paget's disease; epidermal cells were cultured in vitro. An enrichment of Paget cells was carried out from the cultured epidermal cells by combining an anti-epithelial membrane antigen monoclonal antibody, binding to immunobeads, and density gradient centrifugation in Nycodenz. The separated cells were re-cultured in Keratinocyte-SFM serum-free media. The proportion of CEA-positive cells did not increase in the cultures, and the purified cells did not show any increase in survival times compared to the non-purified cultured cells. These results suggest that the decrease of CEA-positive cells noted during culture results from a decline in expression of CEA in the Paget cells. Paget cells in the involved epidermis do not proliferate significantly and thus differ from many other malignant cells.  相似文献   
85.
Mycosis fungoides (M.F.) is a rare cutaneous malignancy of childhood and adolescence. The disease commonly presents with the classic sequence of erythematous patches and plaques. Hypopigmentation as the presenting symptom is distinctly rare. This is the 9th case report of M.F. presenting with hypopigmentation in a patient under 20 years of age. The disease was only partially controlled with PUVA therapy, necessitating nitrogen mustard treatment.  相似文献   
86.
A 42-year-old woman with progressive myelopathy and mononeuritis multiplex is reported. The neurological examination on admission revealed hyperreflexia of the four extremities with pathological reflexes and moderate muscle weakness of the lower extremities with spasticity. Sensory disturbance was distributed on the areas of the bilateral lateral cutaneous femoral, the superficial peroneal and sural nerves. The antibody to HTLV-I in the serum and cerebrospinal fluid was more than 8192X and 512X, respectively. No sensory potential was recorded in the sensory conduction study of bilateral lateral femoral cutaneous nerves. Corticosteroid therapy caused a marked improvement of the sensory and urinary disturbances and had a slight effect on the spastic gait. Our nerve conduction study found small sensory potentials with normal conduction velocities in the bilateral lateral femoral cutaneous nerves. These results suggested the presence of an axonal degeneration in the peripheral nerves in this case. There have been no reports in the literature regarding a case of HAM with mononeuritis multiplex.  相似文献   
87.
Intestinal dialysis of drugs by oral administration of activated charcoal has been compared with peritoneal dialysis in rats. The average amounts of theophylline transported over 120 min into the intestinal lumen and the peritoneal cavity were 15.7 and 16.5% of the intravenous dose (10 mg kg-1), respectively, showing no significant difference, whereas the amount of the same intravenous dose of phenobarbitone transported from the blood into the intestinal lumen (7.8%) was significantly smaller than that entering the peritoneal cavity (12.5%). The net water flux showed that secretion predominated in the peritoneal transport whilst absorption predominated in the intestinal transport for both drugs. However, the net water flux in the intestinal lumen after intravenous theophylline (as aminophylline) was significantly smaller than that following phenobarbitone. The differences in transport across the two membranes could be due to differences in the intrinsic properties of the could be due to differences in the intrinsic properties of the membranes, such as the surface area, the thickness of the membrane and the distribution of blood vessels. Differences could also be due to differences in the pharmacological effects of the drugs.  相似文献   
88.
A 10-year experience with 2,441 patients over 65 years of age undergoing operations for non-upper gastrointestinal tracts was reviewed to evaluate both the incidence of postoperative upper gastrointestinal bleeding and the clinical risk factors associated with the complication. A total of 18 (0.7%, 7 males and 11 females) patients had overt postoperative upper gastrointestinal bleeding of non-variceal origin documented by endoscopic findings or blood transfusions. Of these, the complication developed in 10 (1.5%) of 646 patients after an operation for biliary or pancreatic disease, 1 (1.5%) of 64 for aneurysmal or obstructive arterial disease, 5 (1.1%) of 43 for colorectal cancer and 2 (0.3%) of 916 for hernia. The incidences of bleeding after an operation for obstructive jaundice (3.8%), for biliary or pancreatic malignancy (4.5%), and of unavoidable diversion colostomy for colorectal anastomosis (3.1%) were significantly higher than for non-jaundice (0.6%), for non-malignancy (1.1%) and of postoperative upper gastrointestinal bleeding in the present study. The origins of bleeding were gastric ulcer in 11, acute gastric mucosal lesion in 4, duodenal ulcer in 1 and other in 2. All cases of bleeding were treated and met success in hemostasis using H2-blockers. Of these, however, 5 patients died of multiple organ failure despite discontinued hemorrhage, prophylactic use of H2-blockers showed a decrease in occurrence of postoperative upper gastrointestinal bleeding in the present study.  相似文献   
89.
OBJECTIVE: We aimed to determine whether or not the potential distribution of the sympathetic skin response (SSR) on the palm and dorsum of the hand can be described by an equivalent current dipole (ECD) as an SSR source model. METHODS: The SSR of 22 normal subjects were simultaneously obtained from two electrodes placed on the palm and the dorsum of hand, with an indifferent electrode on the thumbnail. We then measured the SSR potential distribution in 10 of the 20 subjects who had responded to stimulation with a clear dorsal SSR. To do this, 18 electrodes were attached to the palm and dorsum of the hand. SSR-evoking stimulation (sound, voice and rapid inspiration) were randomly delivered to the subject at time intervals of more than 1min to minimize the habituation effect. We estimated the ECD from the measured potential distribution. RESULTS AND CONCLUSIONS: The SSR-evoked by stimulation was negative in potential at the palmar sites of all 22 subjects, and was positive in potential at the dorsal sites of the hand in 20 of the 22 subjects. The SSR potential distribution, which was measured in 10 subjects, reached its maximum negative and positive potential near the base of the middle finger on the palm, and near the corresponding site on the dorsum of the hand, respectively. The SSR potential measured on the dorsum of the hand, however, was about 1/3 in amplitude of those on the palmar sites. These results suggest that the SSR source is located on the palm (probably the sweat glands) as confirmed by the estimated ECD (a negative pole on the palm and a positive pole on the dorsum of the hand). We speculate that the SSR may result from the potential difference caused by the Na(+) concentration gradient in the sweat, which results from intracanal reabsorption of Na(+). SIGNIFICANCE: The ECD resulting from the Na(+) concentration gradient within the canal of sweat glands is thought to be the source of the SSR from the negative pole on the palm to the positive pole on the dorsum.  相似文献   
90.
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