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   1405598篇
  免费   100361篇
  国内免费   7852篇
耳鼻咽喉   20144篇
儿科学   41119篇
妇产科学   39592篇
基础医学   195857篇
口腔科学   41003篇
临床医学   121976篇
内科学   273027篇
皮肤病学   31007篇
神经病学   110066篇
特种医学   56085篇
外国民族医学   476篇
外科学   215471篇
综合类   42761篇
现状与发展   23篇
一般理论   438篇
预防医学   96370篇
眼科学   33167篇
药学   107262篇
  78篇
中国医学   6640篇
肿瘤学   81249篇
  2018年   14156篇
  2017年   11607篇
  2016年   12603篇
  2015年   14964篇
  2014年   20672篇
  2013年   28699篇
  2012年   37806篇
  2011年   40479篇
  2010年   24152篇
  2009年   22913篇
  2008年   36996篇
  2007年   40152篇
  2006年   40843篇
  2005年   39486篇
  2004年   37304篇
  2003年   36224篇
  2002年   35382篇
  2001年   65122篇
  2000年   66922篇
  1999年   57237篇
  1998年   15917篇
  1997年   14839篇
  1996年   13998篇
  1995年   13151篇
  1994年   12277篇
  1992年   43345篇
  1991年   41783篇
  1990年   40984篇
  1989年   39910篇
  1988年   37267篇
  1987年   36673篇
  1986年   35130篇
  1985年   33262篇
  1984年   24921篇
  1983年   21130篇
  1982年   12709篇
  1981年   11631篇
  1979年   23978篇
  1978年   17084篇
  1977年   14853篇
  1976年   13404篇
  1975年   15277篇
  1974年   18090篇
  1973年   17565篇
  1972年   16814篇
  1971年   15720篇
  1970年   14915篇
  1969年   14348篇
  1968年   13462篇
  1967年   12020篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Sett  P. K.  Crockard  H. A.  Powell  M.  Lightman  S.  Jacobs  H. 《Acta neurochirurgica》1990,102(1-2):69-72
Summary Two cases of meningiomas, which are considered to have been caused by the preceding irradiation, are reported. In both cases, the cytokinetic study of the tumour using bromodeoxyuridine (BrdU) was performed. The percent of the tumour cells in the S phase of the cell cycle was less than 1% in both cases. The low labelling indices might suggest a relatively slow growing potential of these tumours, though the radiation-induced meningiomas were reported as being rapidly growing and malignant.  相似文献   
992.
A spinal cord injury model is described using chymopapain as a neurotoxic agent in rats. The trauma was evaluated by neurophysiological and morphological methods. Electrically evoked compound action potentials were used to quantify the neurophysiological effects caused by the injection of chymopapain into the lumbar dural theca in rats. A branch of the sciatic nerve was stimulated with voltage impulses of constant amplitude (40 V) and duration (0.1 ms) at the right external malleolus. The responses were recorded at the dorsal root entry zone L1. We used different doses of the enzyme (1000 i.u./ml; 2500 i.u./ml; 5000 i.u./ml). A total amount of 0.1 ml was injected into the rats' lumbar spinal canal intrathecally (n = 18). The control rate (n = 8) were subjected to exactly the same stimulus and recording procedures but the test solution was a corresponding volume of isotonic saline. Two hours after injection the animals were examined clinically and then sacrificed for histology. The prolongation of the latency of the electrically evoked potentials caused by the enzyme was very clear at the doses of 2500 i.u. and 5000 i.u. being about 10-15% relative to the mean latency before administration of the drug. The histological evaluation showed hemorrhage, vascular damage and indirect signs of myelin edema of the lumbar nerve tissue. Our study indicates that chymopapain injections into the lumbar spinal canal can be used as a reproducible model for spinal cord injury research.  相似文献   
993.
12 giant intracranial aneurysms were studied by MRI. Intraluminal thrombosis was observed in 9 aneurysms. Thrombosis was found more frequently in larger aneurysms. Thrombi were formed posteriorly or inferiorly in the lumen of 4 among 5 IC-cavernous aneurysms. Location of the neck of the aneurysms and stagnation of blood flow influenced by gravity may be causative factors determining the location of thrombi. In 6 aneurysms intraluminal thrombi were inhomogeneous on MRI, suggesting that the thrombi had been formed at different times. New thrombi were formed between the aneurysmal wall and the old thrombus in 3 cases. Dissection of the aneurysmal wall by residual blood flow in the lumen or hemorrhage in the aneurysmal wall may be one of the growth mechanisms of giant intracranial aneurysms.  相似文献   
994.
Studies were performed to evaluate the effect of unilateral nephrectomy on glycerol-induced acute renal failure in the rat. Normal rats were subjected to either sham uninephrectomy (n = 43) or right uninephrectomy (n = 53). The functional compensation of the remaining kidney was followed after 1 and 2 weeks. Fourteen days after the operation, acute renal failure was induced by injection of 50% glycerol solution to both groups. Uninephrectomised rats developed a lesser degree of renal failure compared to sham-operated rats. Forty-eight hours after glycerol injection, PCr of uninephrectomised rats was 260 +/- 22 mumol/l compared with 338 +/- 26 in sham-operated rats (P less than 0.0125) and CCr in uninephrectomised rats was greater (0.10 +/- 0.01 ml/min vs 0.07 +/- 0.01; P less than 0.025) in sham rats. Uninephrectomised rats had significantly greater recovery of CCr compared to sham rats at 24 h (20.1% +/- 2.3 vs 13.1% +/- 2.2, P less than 0.025) and at 48 h (32.1% +/- 3.3 vs 19.2% +/- 3.3, P less than 0.005) after glycerol injection. FENa was significantly less in uninephrectomised rats: 0.96 +/- 0.16% vs 2.25 +/- 0.05% (P less than 0.025) in sham rats 24 h post glycerol. Urinary excretion of K+ was greater in rats following uninephrectomy compared to sham rats both after 24 h and 48 h post glycerol (P less than 0.01), accompanied by lower plasma potassium (P less than 0.05). A correlation coefficient (r) of 0.793 was observed between urinary potassium excretion rate and percentage recovery of CCr.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
995.
Laparoscopic cholecystectomy (LC) using electrocoagulation was successfully performed in 56 out of 58 selected patients. Cholangiography was performed in 53 patients. Six patients had common duct stones; five were unsuspected preoperatively. After the gallbladder was removed, three patients underwent open common duct exploration. In another five cases, anatomical anomalies were discovered. Cholangiography performed via the cystic duct before any structures are divided can prevent the most serious complication--common duct injury. Cholangiography should be attempted on all patients undergoing LC.  相似文献   
996.
Using high resolution ultrasonography (US), diagnostic accuracy of thrombi in each venous segment of lower limbs and qualitative evaluation of thrombi in deep vein thrombosis (DVT) were investigated. The subjects were 106 lower limbs in 81 patients. The thrombi in common femoral vein (CFV), were diagnosed by compression technique and, were qualitatively analysed by echogenicity and consistency. Venography was performed in 18 limbs and histologic tests of thrombi were made in 6 limbs. The total accuracy of US was 100% for diagnosis of DVT, but was 83% for diagnosis of its extent. The total accuracy of US in each segment was greater than 90%, but the sensitivity of iliac veins was less than 90%. The thrombi in CFV were divided into 3 types and 8 sub-types. Type A was homogenous, type B was heterogenous, and type C was contracted echo. The types of us were consistent with results of histologic tests. We concluded that high resolution US is available for screening test for diagnosis of DVT and that qualitative evaluation of thrombi by US is a useful clinical test for selection of more adequate treatments.  相似文献   
997.
We present a case of acute bowel obstruction in an immunocompromised child, who also had lobar pneumonia and a giant unilateral pneumatocele. She was successfully managed with subarachnoid anaesthesia for exploratory laparotomy to relieve a colonic obstruction. This proved to be a safe alternative to general anaesthesia with tracheal intubation in this patient and should be considered in infants and children in selected cases whenever a contraindication to general anaesthesia exists.  相似文献   
998.
Nonocclusive mesenteric ischemia (NOMI) is a disorder with an extremely high mortality. Salvage of affected patients requires early recognition and aggressive intervention to prevent intestinal gangrene. Dialysis patients represent a group at particularly high risk for this condition. Clinicians should develop a high index of suspicion for NOMI in dialysis patients to lessen the risk of death. A high interventional posture must be maintained due to the notoriously unreliable signs and symptoms of this disorder.  相似文献   
999.
Bertalanffy  H.  Kretzschmar  H.  Gilsbach  J. M.  Ott  D.  Mohadjer  M. 《Acta neurochirurgica》1990,104(3-4):151-155
Summary This case report describes a patient presenting with symptoms of increased intracranial pressure, whose computerized tomographic (CT) scan was highly suggestive of a large low-grade glioma invading the basal ganglia. Magnetic resonance imaging (MRI) revealed a well-demarcated space-occupying mass of increased intensity in the left lateral ventricle and adjacent white matter. Following stereotactic biopsy, which yielded a homogeneous jelly-like material, the mass was removed microsurgically and was found to be most like a colloid cyst on histological examination. Discussion focusses on the clinical and differential diagnostic implications of this very unusual combination of findings.  相似文献   
1000.
A review of hip radiographs of patients with severe hemophilia showed Legg-Calvé-Perthes disease in four of 63 patients examined before the era of specific treatment. In another series of 44 patients receiving prophylactic treatment, there was no evidence of Legg-Calvé-Perthes disease. A case report of a boy with severe hemophilia with hip joint bleeding that caused joint capsule distention and greatly increased intracapsular pressure is presented. Based on our findings, and previously published results, we suggest that Legg-Calvé-Perthes disease in hemophilia is caused by increased intracapsular pressure secondary to hemarthrosis.  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