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   47369篇
  免费   2227篇
  国内免费   227篇
耳鼻咽喉   782篇
儿科学   832篇
妇产科学   786篇
基础医学   6079篇
口腔科学   1387篇
临床医学   3354篇
内科学   11242篇
皮肤病学   651篇
神经病学   3881篇
特种医学   1533篇
外科学   8278篇
综合类   211篇
一般理论   2篇
预防医学   1687篇
眼科学   720篇
药学   3890篇
中国医学   103篇
肿瘤学   4405篇
  2023年   234篇
  2022年   489篇
  2021年   869篇
  2020年   428篇
  2019年   597篇
  2018年   716篇
  2017年   570篇
  2016年   735篇
  2015年   740篇
  2014年   963篇
  2013年   1292篇
  2012年   2080篇
  2011年   2241篇
  2010年   1323篇
  2009年   1132篇
  2008年   2107篇
  2007年   2309篇
  2006年   2309篇
  2005年   2316篇
  2004年   2245篇
  2003年   2166篇
  2002年   2122篇
  2001年   1667篇
  2000年   1838篇
  1999年   1571篇
  1998年   599篇
  1997年   497篇
  1996年   431篇
  1995年   358篇
  1994年   339篇
  1993年   291篇
  1992年   1132篇
  1991年   958篇
  1990年   920篇
  1989年   962篇
  1988年   852篇
  1987年   856篇
  1986年   793篇
  1985年   789篇
  1984年   534篇
  1983年   434篇
  1982年   230篇
  1979年   492篇
  1978年   288篇
  1977年   263篇
  1975年   214篇
  1974年   228篇
  1971年   230篇
  1969年   233篇
  1968年   217篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The effect of ketamine infusion to control the intractable pain which had not responded to ordinary procedures in 12 patients with advanced cancer were evaluated. Ketamine 250 mg or 500 mg in 500 ml of transfusion fluid with or without 10 to 20 mg of droperidol was administered intravenously at the rate of 3 to 20mg of ketamine per hour. The pain scores by VAS in most of the patients decreased significantly with an averaged value of 8.3 before the treatment to 1 during the procedure. The durations of this therapy lasted from over 6 hours to 48 days. Slight disorientation in one patient and drowsiness in 5 were seen during the infusion. No cardiovascular or respiratory complications were noted. These results indicate that ketamine infusion is a useful therapeutic procedure to treat cancer pain which resist ordinary pain therapies.  相似文献   
92.
Atrial natriuretic polypeptide (ANP) is composed of a family of peptides isolated from rat and human atria. In the present study, the relaxant effects of ANP, sodium nitroprusside and 8-bromo-cyclic guanosine monophosphate (GMP) were investigated in guinea-pig tracheal smooth muscle, and the tissue cyclic GMP and cyclic adenosine monophosphate (AMP) concentrations were measured. ANP, sodium nitroprusside and 8-bromo-cyclic GMP showed relaxant effects on the spontaneous tone in normal Krebs solution (5.9 mmol/l K(+)-2.4 mmol/l Ca++ solution). They diminished relaxant effects on 40 mmol/l K(+)-0.1 mmol/l Ca++ induced contraction, which was approximately the same tension as the spontaneous tone. Sodium nitroprusside and 8-bromo-cyclic GMP diminished less relaxant effects on 40 mmol/l K(+)-2.4 mmol/l Ca++ induced contraction, but ANP showed no relaxation. The tissue cyclic GMP levels following administration of ANP and sodium nitroprusside in normal Krebs solution, in 40 mmol/l K(+)-2.4 mmol/l Ca++ solution, and in 40 mmol/l K(+)-0.1 mmol/l Ca++ solution increased dose-dependently without regard to external Ca++ concentrations, while the tissue cyclic AMP levels did not change. These results suggest that ANP might be a novel potent relaxant in airway smooth muscle and the relaxant effect may be, at least in part, mediated by cyclic GMP. There was a difference in relaxant effects on tracheal smooth muscle between ANP and sodium nitroprusside.  相似文献   
93.
A 64-year-old man, who had an aneurysm of aortic arch associated with the aberrant right subclavian artery, was treated successfully. He was pointed out to have an aneurysm of aortic arch three years ago. Three years later angiograms and computed tomography revealed that it became larger compared with the initial finding. He underwent a replacement of the aortic arch using a woven Dacron graft under open distal method. Aberrant subclavian artery was not involved in the aneurysm. But because the left subclavian artery was involved in it, a woven Dacron graft was interposed between the ascending aorta and left subclavian artery. Postoperative course was uneventful and there were no complications.  相似文献   
94.
A nondestructive method using a combination of three 2D NMR techniques, DQF-COSY (double quantum filter correlation spectroscopy), HMQC (1H-detected multiple quantum coherence), and HMBC (heteronuclear multiple bond correlation), were developed for structural determination of microcystins, toxic heptapeptides produced by cyanobacteria. With this procedure we were able to assign all carbons and protons of microcystins LR (1) and RR (2), thus determining the constituent amino acid sequences. The procedure was also applied to the microcystin-associated nontoxic minor components, which have molecular weights and amino acid compositions similar to those of 1 and 2 and toxicities different from those of 1 and 2. From detailed analysis of these spectra we rapidly deduced that the minor components are geometrical isomers with respect to C-7 of the diene in Adda of the parent toxins. The structures were finally confirmed to be 3 and 4 by ROESY (rotating frame nuclear Overhauser and exchange spectroscopy) technique.  相似文献   
95.
A 67-year-old man with positive serum reaction for syphilis had been followed by cardiologist for his moderate-sized saccular ascending aortic aneurysm and small-sized abdominal aortic aneurysm. Because of his transient ischemic attack probably secondary to the thrombo-embolism of the aneurysm and rapid growing of its size, surgical treatment was recommended. Resection of the saccular aneurysm with patch plasty of the ascending aorta was performed under the cardiopulmonary bypass associated with right side cerebral perfusion. At the time of operation, the mildly dilated ascending aorta and arch with multiple intimal ulceration were noted. Although his postoperative hemodynamic condition was stable, he suffered from multiple cerebral infarction, probably due to embolism migrated from the fragile aortic intima. His neurological condition was improved promptly, trivial hemi-paralysis was remained. The specimen of resected aneurysmal wall revealed syphilitic changes microscopically. We concluded that the extent of the aortic replacement with prosthetic graft should be deceived not only with its external appearance, but also with the changes of its inside.  相似文献   
96.
The effect of complete unilateral ureteral obstruction (CUUO) on proximal tubular functions was studied in rats, using the K+-sensitive microelectrode technique and split oil drop method. In the control kidneys peritubular membrane potential (EMperi) and intracellular potassium activity (aKi) were -70.8 +/- 7.0 mV and 81.2 +/- 22.0 mEq/liter (mean +/- SD), respectively. In the CUUO kidneys both EMperi and aKi were progressively reduced with the duration of obstruction. However, in all tubules aKi values were still above the electrochemical equilibrium. In the three days' CUUO kidneys EMperi and aKi were -51.5 +/- 11.7 mV and 53.8 +/- 22.8 mEq/liter, respectively. Rate of fluid absorption (JVL;nl./sec. mm.) across the proximal tubular epithelium from Ringer solution in the control and three days' CUUO kidneys was 0.029 and 0.0065 respectively. In the CUUO kidneys there were wide variations in JVL and EMperi, but there was a clear correlation between these two variables. JVL from choline chloride solution was negligible in both control and CUUO kidneys. From above results, it was suggested that the proximal tubular reabsorption primarily depending on the Na+-K+ pump might be reduced but still working in the CUUO kidney, and thus the proximal tubular reabsorption might take part in preservation of glomerular filtration during the obstruction.  相似文献   
97.
A 48-year-old woman was admitted because of increased bloody sputum. Since she had had a history of repeated thrombotic episodes including venous thrombosis in the lower limbs (21 year old) and pulmonary emboli developing into pulmonary infarction (41 years old), the patient was treated with anti-coagulant therapy using Warfarin for 7 years. Warfarin was discontinued after admission and heparin was administered instead at a relatively low dose of 5,000 units daily, resulting in a considerable diminution of hemoptysis. Unfortunately however, it caused a relapse of active thrombosis associated not only with a significant increase of the product of fibrinolysis (FDP), LDH and GOT but with a concomitant decrease of the platelet count. Hematological examinations concerning coagulation and fibrinolysis remained within a normal range except for the serum concentration of antithrombin III (AT III) and its functional property with regard to the heparin cofactor, which were 8.8 mg/dl and 48%, respectively. Since the findings were consistent with congenital deficiency of AT III, some members of her family were also examined. The concentration of AT III and its activity in the patient's son and her daughter deteriorated in a similar manner, indicating that this was a definite case of congenital deficiency of AT III. The clinical manifestations of 87 cases with congenital AT III deficiency, belonging to 24 families reported in Japan were reviewed.  相似文献   
98.
The effects of testosterone (T) and 17 beta-estradiol (E2) on the prostate of castrated rats were investigated by histopathological and immunocytochemical procedures. A significant increase in prostatic weight occurred after 6 weeks treatment with T alone and in combination with E2. The greatest increase in prostatic weight occurred after the administration of T plus E2. Histopathologically, glandular hyperplasia of the prostate was noted, and the number of bromodeoxyuridine (BrdU)-positive cells showed a significant increase over that induced by testosterone alone.  相似文献   
99.
Cross-resistance to anticancer drugs, termed multidrug resistance (MDR), is functionally associated with the expression of a plasma membrane, energy-dependent, drug efflux pump termed P-glycoprotein (PGP), the product of the mdr1 gene. We have shown previously that MCF-7 breast carcinoma cells transfected with the human mdr1 gene (BC-19 cells) exhibit greater MDR when stably transfected with protein kinase C alpha (PKC alpha). We now demonstrate that transfection of BC-19 cells with the gamma isoform of PKC (BC-19/PKC gamma cells), which is not normally present in BC-19 cells, does not confer increased resistance to doxorubicin, despite a 19-fold increase in PKC activity. All of the increased PKC activity is accounted for by PKC gamma and it is rapidly down-regulated by phorbol dibutyrate, within 15 min of treatment. Endogenous PKC alpha and PKC epsilon activities are not affected by phorbol dibutyrate. The cytotoxicity of doxorubicin was similar in BC-19/neo or BC-19/PKC gamma cells after either 2-hr or continuous drug exposure, and co-treatment with phorbol dibutyrate increased resistance to doxorubicin 4-fold in both cell lines. Phosphorylation of PGP was similar in both cell lines and drug accumulation was not affected by overexpression of PKC gamma. These results demonstrate that transfection of PGP-expressing cells with an atypical isoform of PKC does not confer increased MDR, and they suggest that the regulation of PGP is phenotype specific with respect to the isoform of PKC.  相似文献   
100.
Magnetic resonance cholangiopancreatography (MRCP) was performed in 35 patients to evaluate the feasibility of its use as a postsurgical imaging technique after resection of the pancreas. The surgical procedures performed were: pancreatoduodenectomy in 22 patients, segmental pancreatectomy in 1, distal pancreatectomy in 7, and pyroluspreserving pancreatoduodenectomy in 5. The pancreatic duct was shown in its entirety in 24 of the 35 patients (68.6%) and was partially visualized in 8 patients (22.9%), but the intrahepatic and extrahepatic bile ducts were visualized completely in all patients. Furthermore, MRCP was able to demonstrate lesions in 3 of 6 patients who had shown clinical evidence of recurrence. The visualization of the pancreatic and bile duct system was satisfactory despite anatomical changes brought about by resection of the pancreas. Thus, we conclude that MRCP is an appropriate follow-up screening test for patients with suspected abnormalities of the biliary and pancreatic duct system.  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