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   384034篇
  免费   21578篇
  国内免费   2799篇
耳鼻咽喉   5273篇
儿科学   8240篇
妇产科学   10145篇
基础医学   53440篇
口腔科学   11850篇
临床医学   30305篇
内科学   78729篇
皮肤病学   8584篇
神经病学   27371篇
特种医学   13976篇
外国民族医学   82篇
外科学   60813篇
综合类   9998篇
现状与发展   1篇
一般理论   64篇
预防医学   17568篇
眼科学   9513篇
药学   31165篇
  11篇
中国医学   2241篇
肿瘤学   29042篇
  2021年   2762篇
  2019年   2923篇
  2018年   4621篇
  2017年   3589篇
  2016年   3683篇
  2015年   4094篇
  2014年   5785篇
  2013年   7461篇
  2012年   10145篇
  2011年   10304篇
  2010年   6245篇
  2009年   5886篇
  2008年   9540篇
  2007年   10336篇
  2006年   10271篇
  2005年   9308篇
  2004年   8805篇
  2003年   8546篇
  2002年   8219篇
  2001年   28226篇
  2000年   28779篇
  1999年   23634篇
  1998年   5170篇
  1997年   4255篇
  1996年   3831篇
  1995年   3480篇
  1994年   3106篇
  1993年   2842篇
  1992年   16053篇
  1991年   14812篇
  1990年   14164篇
  1989年   13968篇
  1988年   12588篇
  1987年   12069篇
  1986年   11106篇
  1985年   10327篇
  1984年   6918篇
  1983年   5601篇
  1982年   2721篇
  1979年   5477篇
  1978年   3350篇
  1977年   2975篇
  1975年   2644篇
  1974年   3064篇
  1973年   2866篇
  1972年   2828篇
  1971年   2773篇
  1970年   2510篇
  1969年   2545篇
  1968年   2250篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Ovarian protein content and fat body protein synthesis were measured during the first gonotrophic cycle in virgin female Blaberus discoidalis cockroaches. Protein synthesis was measured for in vitro fat bodies from animals treated with combinations of a juvenile hormone analog (JHA = methoprene) and corpora cardiaca (CC) extracts. Ovarian protein content began to increase on Day 5 of adult life and reached its maximum at Days 20-22. Synthesis of proteins secreted by the in vitro fat body increased by 12-fold between emergence and its maximum on Day 18, then declined to nearly its original level by Day 33. Synthesis of nonsecreted, fat body proteins increased by 4-fold between emergence and a maximum on Day 21, then declined. CC extracts and JHA were administered to decapitated females to determine their regulative effects on fat body protein synthesis. The synthesis by the fat body of nonsecreted proteins was increased by both JHA and CC extracts. In contrast, synthesis of secreted proteins increased only in the presence of JHA. CC extracts, alone, had no effects on the synthesis of secreted proteins, but administration of CC extracts in combination with JHA increased the synthesis of the secreted proteins by 55% above that observed with JHA alone. SDS-PAGE of proteins secreted into the medium by the in vitro fat body demonstrated that JHA stimulated the synthesis of specific polypeptides, whereas CC extracts did not affect the synthesis of specific-secreted polypeptides. These results suggest that JH regulates specific protein synthesis by the fat body of B. discoidalis; neurohormones elevate the general capacity of the fat body for protein synthesis and amplify the specific effects of JH.  相似文献   
992.
993.
A 30-year-old female at 27 weeks' gestation, was hospitalized on September 24 1990 because of the premature rupture of the amniotic sac. She underwent Caesarean section on the same day with 700 ml blood loss, but no blood transfusion was required. For several days after the operation, her hemoglobin level remained 7.8 g/dl and did not increase significantly in spite of parenteral iron therapy. On the 9th postoperative day, chills and pyrexia developed with leukopenia. Bone-marrow aspiration revealed severe erythroblastopenia with giant proerythroblasts, suggesting recent HPV infection, which was confirmed by the presence of anti-HPV IgM and HPV antigen by ELISA. The hemoglobin level gradually decreased to 6.0 g/dl by the 21st day, then began to increase rapidly. The serum of acute-phase containing HPV antigens inhibited BFU-E and CFU-E but not CFU-GM. The serum of convalescent-phase inhibited neither erythroid colony growth nor myeloid colony growth. These results indicate that the inhibitory effect of HPV in colony assay is highly specific for erythropoiesis and that HPV play a role in transient cessation of erythropoiesis. The reason, however, for leukopenia in HPV infection remained unclear. This case shows that HPV infection may induce severe hematological disorders even in normal person under erythropoietic stress.  相似文献   
994.
Acute thoracic aortic dissection has a high mortality if untreated, so the diagnosis must be rapidly made if mortality is to be lowered significantly. Multiple imaging techniques are often used. This retrospective study from 1988 to 1993 assesses the usefulness in diagnosis of chest X-rays, computed tomography (CT) scanning, aortography, magnetic resonance imaging (MRI), trans-thoracic (TTE) and trans-oesophageal (TOE) echocardiography. Forty-two patients with a final clinical diagnosis of dissection were studied. The diagnosis was confirmed in 16 (13 at surgery and three at autopsy). Three died with dissection given as the only cause for death. Chest X-ray abnormalities were seen in all 19 patients with surgery or death from dissection, with a widened mediastinum and/or dilated aorta being present in 17. In the group of 16 patients with surgery or autopsy proof, CT scans found dissections in 9 of 12 patients studied and correctly classified the type in only five. Aortography was performed in five, with accurate depiction of dissection and type in all. TTE found dissections in three of eight patients imaged by this method. MRI and TOE were performed each on two patients, with accurate depiction of dissection and type in each. Because of the relatively low sensitivity of CT scanning in defining aortic dissections Westmead Hospital is currently assessing the use of TOE as the prime imaging modality prior to surgical intervention.  相似文献   
995.
996.
We have investigated the use of a cationic lipid preparation to enhance antisense oligonucleotide activity in human umbilical vein endothelial cells. A liposomal preparation containing the cationic lipid N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) was found to increase by at least 1000-fold the potency of an antisense oligonucleotide (ISIS 1570) that hybridizes to the AUG translation initiation codon of human intercellular adhesion molecule-1. In the presence of 8 microM DOTMA, 6-15-fold more 35S-ISIS 1570 associated with cells, at oligonucleotide concentrations from 0.01 to 5 microM, than did in the absence of DOTMA. Both 35S-ISIS 1570 association with cells and antisense activity were increased as a function of DOTMA concentration and with increasing time of incubation with the cationic lipid. Fluorescein-labeled ISIS 1570 was used to assess the intracellular distribution of the oligonucleotide in the presence and absence of DOTMA. In the absence of DOTMA, the oligonucleotide localized to discrete structures in the cytoplasm of the cell, resulting in a punctate fluorescence pattern. In the presence of DOTMA, cellular fluorescence markedly increased and the oligonucleotide localized within the nucleus, as well as to discrete structures in the cytoplasm. Accumulation of the oligonucleotide in the nucleus in the presence of DOTMA was time and temperature dependent. Nuclear accumulation was inhibited by preincubation of the cells with monensin but not chloroquine, NH4Cl, nocodazole, colcemid, or brefeldin A. These data demonstrate that cationic lipids increase antisense activity by increasing the amount of oligonucleotide associated with cells and altering intracellular distribution of the oligonucleotide.  相似文献   
997.
998.
We reported clinical and neuropathological observations of a 41-year-old man with Degos disease. He first noted painless skin lesions over the upper extremities in January, 1982. Three years later he was diagnosed as Degos disease by skin biopsy, and treatment with aspirin was started. In September, 1985, he complained of paresthesia on his right arm, followed by a series of new neurological manifestations suggesting multifocal spinal cord lesions. On October 28, examination of admission showed papules with central umblication over the whole body except the head, face, palms, soles and scrotum. Neurological examination revealed no weakness, diminished right biceps reflex, exaggerated patellar reflexes and Achilles reflexes, left extensor plantar reflex, hypesthesia and hypalgesia to the level of Th8, mild left spastic gait, and retention of urine. In November, he had paraparesis, loss of vibration sense of lower extremities, hypesthesia and hypalgesia to the level of TH4, and weakness of right upper extremity. In December, he showed tetraplegia, left-sided facial palsy, and hypesthesia and hypalgesia to the level of C5. In January, 1986, he showed right facial palsy, left facial hypesthesia, pseudobulbar palsy. In February, he had bilateral abducens nerve palsy and hiccups. On February 18, he died of intracranial hemorrhages. He had episodic abdominal pain several times during admission. His condition deteriorated progressively in four months after the first manifestation of neurological symptoms, despite the therapy with heparin, urokinase, ticlopidine, dipyridamole, and prednisolone. Laboratory studies showed gradual increase of CSF proteins (from 156 mg/dl to 602 mg/dl) and extremely increased platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
999.
A 54-year-old female presented with subarachnoid hemorrhage due to rupture of a small middle cerebral artery aneurysm, found to be thrombosed at surgery and not visualized on the preoperative angiograms. One major branch of the middle cerebral artery was found to be occluded near the trifurcation. The lumen of the branch proximal to the occlusion had appeared as the aneurysmal opacification on the preoperative angiograms.  相似文献   
1000.
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