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   2368167篇
  免费   172399篇
  国内免费   5296篇
耳鼻咽喉   32036篇
儿科学   77961篇
妇产科学   65237篇
基础医学   336292篇
口腔科学   67725篇
临床医学   208738篇
内科学   466440篇
皮肤病学   53010篇
神经病学   185380篇
特种医学   91177篇
外国民族医学   562篇
外科学   363180篇
综合类   53825篇
现状与发展   4篇
一般理论   751篇
预防医学   175083篇
眼科学   56233篇
药学   172084篇
  7篇
中国医学   5670篇
肿瘤学   134467篇
  2019年   17980篇
  2018年   26075篇
  2017年   20020篇
  2016年   21833篇
  2015年   24917篇
  2014年   34960篇
  2013年   51871篇
  2012年   71176篇
  2011年   75242篇
  2010年   44963篇
  2009年   42260篇
  2008年   70627篇
  2007年   75177篇
  2006年   75723篇
  2005年   72918篇
  2004年   70245篇
  2003年   67211篇
  2002年   65262篇
  2001年   119051篇
  2000年   121979篇
  1999年   101606篇
  1998年   27132篇
  1997年   24043篇
  1996年   24085篇
  1995年   22930篇
  1994年   21268篇
  1993年   19712篇
  1992年   77625篇
  1991年   74768篇
  1990年   72259篇
  1989年   69530篇
  1988年   63743篇
  1987年   62320篇
  1986年   59115篇
  1985年   56057篇
  1984年   41554篇
  1983年   35297篇
  1982年   20315篇
  1979年   37190篇
  1978年   25793篇
  1977年   21916篇
  1976年   20444篇
  1975年   21942篇
  1974年   26485篇
  1973年   25481篇
  1972年   23768篇
  1971年   22026篇
  1970年   20709篇
  1969年   19405篇
  1968年   18215篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Eleven patients with lunatomalacia were treated by excision of the lunate and instillation of liquid silicone. The silicone vulcanised and formed an in-situ molded prosthesis. The patients were reexamined after a mean of 7.1 years. Four patients were pain-free and two had pain only at work; three had not been improved by the operation and two had undergone arthrodesis. The patients with good results all belonged to group IV pre-operatively. Surprisingly, no patient showed any sign of silicone synovitis, although all the prostheses except one had either fractured or deformed. The reasons for this are discussed and the indications for the operation established.  相似文献   
992.
We retrospectively reviewed our experience with immediate breast reconstruction in 103 consecutive patients with stage 0 or I breast carcinoma between May 1983 and April 1988. Two reconstructive techniques were used, that is, either tissue expansion with secondary prosthesis implantation (60%) or transverse rectus abdominis musculocutaneous (TRAM) flap (40%). Chemotherapy was administered in 22% of patients without delay or compromise. The mean length of follow-up is 30 months. The complication rate was equal for both groups (24%) with infection being most common in the group of patients with tissue expansion and partial flap necrosis being most common in the group of patients with TRAM flaps. Aesthetic results were superior with use of the TRAM flap. Our experience concurs with previous reports that documented satisfactory results with immediate breast reconstruction without compromising further therapy. We conclude that although the tissue expansion technique yields acceptable results, the TRAM flap yields superior aesthetic results in terms of both appearance and consistency.  相似文献   
993.
Summary Previous studies of Alcian blue-induced birefringence in adult avian cortical bone showed that a short period of intermittent loading rapidly produces an increased level of orientation of proteoglycans within the bone tissue. In the absence of further loading, this persists for over 24 hours. We have proposed that this phenomenon could provide a means for “capturing” the effects of transient strains, and so provide a persistent, constantly updated strain-related influence on osteocyte populations related to the bones' averaged recent strain history, in effect, a “strain memory” in bone tissue. In our present study, we use the Alcian blue-induced birefringence technique to demonstrate that proteoglycan orientation also occurs after intermittent loading of both cortical and cancellous mammalian bonein vivo andin vitro. We also show that the change in birefringence is proportional to the magnitude of the applied strain, and that the reorientation occurs rapidly, reaching a maximal value after only 50 loading cycles. Examination of electron micrographs of bone tissue after staining with cupromeronic blue allows direct visualization and quantification of the change in proteoglycan orientation produced by loading. This shows that intermittent loading is associated with a realignment of the proteoglycan protein cores, bringing them some 5 degrees closer to the direction of collagen fibrils in the bone matrix.  相似文献   
994.
995.
We have investigated anemia in patients at different stages of the evolution of three chronic renal diseases: Balkan endemic nephropathy (BEN), chronic pyelonephritis (PN) and chronic glomerulonephritis (GN). A total of 88 patients with creatinine clearances from 9 to 118 ml/min and hemoglobin concentrations from 70 to 160 g/l were studied with regard to the relationship, if any, between erythropoietin production and the type and stage of nephropathy. Anemia in BEN was a particular focus of interest since it had been stated that in BEN, anemia precedes renal failure. Our data neither prove nor disprove this statement. A significant positive correlation between creatinine clearance and hemoglobin concentration was found in all three nephropathies, indicating that in the patients studied the severity of anemia increased with the impairment of renal function regardless of the underlying disease. Serum levels of immunoreactive erythropoietin were in the normal range in 54 patients, moderately increased in 20 and slightly decreased in 14. The erythropoietin level appears to be unrelated to the stage of renal failure or the type of nephropathy. The only exception was the subgroup where the patients with glomerulonephritis and normal renal function had increased serum erythropoietin levels and significantly higher parameters of red blood cell concentration than the patients from the same subgroup with tubulointerstitial nephropathies. In patients with severe renal failure and anemia, serum erythropoietin levels were inappropriately low for the degree of anemia, indicating that erythropoietin plays a role in the pathogenesis of the anemia.  相似文献   
996.
This paper presents 14 examples of a distinctive cardiovascular lesion. The patients' ages ranged from 5 to 76 years (mean, 51 years). There were seven male patients and seven female patients. All of the lesions were small and represented incidental surgical findings. Ten were attached to the endocardium, three were free-floating in the pericardial cavity, and one was inside a dissecting aneurysm of the ascending aorta. Microscopically, the lesions were enclosed in a fibrinous network and composed of a solid proliferation of round to polygonal cells with centrally located nuclei. Immunohistochemically, the cells were negative for FVIII-related antigen and lysozyme, but they stained positively for keratin, especially when clustered in small micropapillary or tubule-like formations. The nature and pathogenesis of these lesions are uncertain. Their location and some of their microscopic features originally suggested a relationship with the entity described as histiocytoid (epithelioid) hemangioma. However, their intense immunoreactivity for keratin, occasional presentation in the pericardial sac, and marked morphologic similarities with nodular mesothelial hyperplasia as sometimes seen in hernia sacs point toward the alternative possibility of a reactive mesothelial nature. A possible pathogenetic mechanism for the endocardial cases is ingrowth of pericardial mesothelial cells along a perforation tract that may have developed at the time of a cardiac catheterization. There were no recurrences or metastases in any of the cases.  相似文献   
997.
The surgical treatment of 100 cases with congenital dilatation of bile duct with special reference to late complications was analyzed. There were no deaths nor occurrences of malignancy. Among 91 patients who had undergone the standard operation, namely total excision of the dilated extrahepatic bile duct and reconstruction after Roux-en-Y hepaticojejunostomy, there were one early complication (pancreatic juice leakage) and five late complications (four intrahepatic gallstones and one liver abscess). The cause of intrahepatic gallstone formation after a total excisional operation was attributed to the remaining intrahepatic bile duct dilatation and the stenosis located between the intrahepatic bile duct dilatation and the common hepatic duct. Accordingly, these results support the total excisional procedure for this condition; however, with regard to the cases associated with cystic dilatation of intrahepatic bile ducts, completely free bile drainage from the dilated intrahepatic biliary system should be performed at the radical operation.  相似文献   
998.
Cyanoacrylate-based glues have been reported as producing dermatitis and bronchial asthma. The paper describes the case of a patient occupationally exposed to Loctite 406, who developed irritation of the skin and mucosae of the face and late bronchial asthma. Preventive measures for subjects exposed to cyanoacrylic instant glues are discussed.  相似文献   
999.
In 570 patients with sporadic primary hyperparathyroidism, the age, sex, symptoms, and preoperative serum calcium values were related to the histopathologic diagnoses, operative findings, and the extent and outcome of parathyroid surgery. Renal stone formation was especially prevalent in younger patients with slight hypercalcemia and parathyroid chief cell hyperplasia, whereas neuromuscular and psychiatric disturbances were overrepresented among older women with higher serum calcium values. Serum calcium concentration was inversely correlated to the proportional incidence of chief cell hyperplasia and positively correlated to the glandular weight of both adenomas and hyperplasias. Glandular size was markedly irregular in chief cell hyperplasia, with increased gland weights of no more than two glands in 78% of patients. During follow-up, for as long as 27 years, normocalcemia was obtained in 91% of patients with adenomas, with failures mainly depending on difficulties in identifying the parathyroid glands. The rate of normocalcemia was lower (80%) among patients with hyperplasia, but an inability to visualize the glands was not a major cause of failure. In patients with hyperplasia with asymmetric and more markedly enlarged glands, it appeared sufficient to remove only the enlarged glands, whereas the findings advocated a subtotal 3- to 3.5-gland resection in patients with more symmetrically or less enlarged hyperplastic glands.  相似文献   
1000.
1. Effects of a novel imidazoindole derivative on cholinergic function were studied in isolated tissue preparations. 2. The compound demonstrated a dose-dependent (10(-11)-10(-9) potentiation (20-60%) of acetylcholine induced tension in guinea pig ileal tissue. 3. Increases in the size of end-plate potentials and nerve evoked muscle twitches were observed in frog nerve-skeletal muscle preparations. 4. Cholinesterase activity was not inhibited. 5. The results suggest that the compound has actions at the post-synaptic muscarinic receptor complex in smooth muscle and causes pre-synaptic increases in ACh release at the neuromuscular junction.  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