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   11016篇
  免费   597篇
  国内免费   34篇
耳鼻咽喉   131篇
儿科学   327篇
妇产科学   182篇
基础医学   1421篇
口腔科学   403篇
临床医学   733篇
内科学   2512篇
皮肤病学   203篇
神经病学   757篇
特种医学   488篇
外科学   1952篇
综合类   57篇
一般理论   1篇
预防医学   300篇
眼科学   144篇
药学   763篇
中国医学   42篇
肿瘤学   1231篇
  2023年   61篇
  2022年   138篇
  2021年   222篇
  2020年   119篇
  2019年   169篇
  2018年   232篇
  2017年   178篇
  2016年   241篇
  2015年   236篇
  2014年   288篇
  2013年   318篇
  2012年   472篇
  2011年   498篇
  2010年   281篇
  2009年   254篇
  2008年   415篇
  2007年   465篇
  2006年   471篇
  2005年   490篇
  2004年   469篇
  2003年   468篇
  2002年   498篇
  2001年   429篇
  2000年   436篇
  1999年   354篇
  1998年   141篇
  1997年   102篇
  1996年   107篇
  1995年   98篇
  1994年   84篇
  1993年   67篇
  1992年   328篇
  1991年   277篇
  1990年   243篇
  1989年   266篇
  1988年   222篇
  1987年   189篇
  1986年   169篇
  1985年   196篇
  1984年   151篇
  1983年   93篇
  1979年   65篇
  1977年   48篇
  1974年   49篇
  1973年   49篇
  1971年   45篇
  1970年   41篇
  1969年   49篇
  1968年   45篇
  1966年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
OBJECTIVES: To evaluate the accuracy of sonographic identification of the site of umbilical cord insertion (CI) at 18-20 weeks of gestation, to compare the sensitivities for detection of a velamentous cord insertion (VCI) secondary to a CI into the anterior, posterior or fundal wall, and to compare the intrapartum complications secondary to VCI into the upper, middle or lower third of the uterus. METHODS: As part of the routine ultrasound scan at 18-20 weeks' gestation we evaluated abnormal CI (VCI and marginal CI) and the location of the CI in the uterus in 3446 pregnancies. In cases of abnormal CI, the location of the CI was further classified as being in the upper, middle or lower third of the uterus. After delivery, the placenta and the umbilical cord were examined and intrapartum complications were compared with the location of the CI. RESULTS: The values for antenatal detection of VCI were: sensitivity, 25 of 40 (62.5%); positive predictive value, 25 of 25 (100%); and negative predictive value, 3406 of 3421 (99.6%). The sensitivity for cases in which the CI was located on the anterior wall was 12 of 13 (92.3%); when it was located on the posterior wall, the sensitivity was 11 of 22 (50.0%); and when it was fundal the sensitivity was 2 of 5 (40.0%). Variable decelerations were frequently observed with a VCI. In lower VCI cases, non-reassuring fetal heart rate patterns and emergency Cesarean sections occurred with a higher frequency than in cases with upper or middle VCI (P < 0.01). After delivery, the length of the aberrant vessels in cases of VCI by pathologic examination was 3.9 +/- 3.3 cm in the upper third, 4.7 +/- 4.6 cm in the middle third, and 10.6 +/- 6.8 cm in the lower third; thus, the aberrant vessel length was significantly greater when the CI was in the lower third of the uterus (P = 0.024). CONCLUSION: We have demonstrated that VCI with a lower CI site and with longer aberrant vessels is associated with various intrapartum complications. This finding has the potential for improving perinatal outcome.  相似文献   
22.
Recently, a self‐expandable metallic stent has been recognized for treatment of malignant duodenal stenosis. But the complications by stenting are important problems even now. In the present study, we report our new method of duodenal stenting by using of double‐balloon enteroscopy considered safe and effective.  相似文献   
23.
Almost one tenth of more than 370 hepatectomies, mostly for tumors, involved resection of major parts of the caudate lobe, subsegment 1. Five of them were for tumors or hemangiomas here, compressing or invading the vena cava; two were for metastases of colorectal cancer located very close to the junctions of the right and middle hepatic veins with the vena cava. We would previously have deemed these tumors unresectable. In these patients the vein was banded above and below the liver, an internal shunt tube placed in preparation for shunting of blood, and the afferent liver blood flow controlled. Control of the vena cava by tightening of the bands was needed in two cases. Tumor-invaded parts of the vein wall were resected in two other cases, in whom the presence of the tube facilitated the resection but the bands did not have to be tightened. The procedure did not cause morbidity and we conclude that tumors close to the vena cava can often be resected without complex vascular exclusion techniques, even when they invade the vein.  相似文献   
24.
We investigated the effects of age and naftidrofuryl oxalate (Naftidrofuryl), a 5-HT2 antagonist, on neurotransmission and transduction systems in the gerbil hippocampus using quantitative autoradiography. [3H]Quinuclidinyl benzilate (QNB), [3H]cyclohexyl-adenosine (CHA), [3H]MK-801, and [3H]muscimol were used to label muscarinic acetylcholine, adenosine A1, N-methyl-d-aspartate (NMDA), and γ-aminobutyric acid-A (GABAA) receptors, respectively. [3H]PN200-110 labeled L-type Ca2+ channels. [3H]Forskolin, [3H]cyclic adenosine monophosphate (cAMP), [3H]phorbol 12,13-dibutyrate (PDBu), and [3H]inositol 1,4,5-triphosphate (IP3) were used to label adenylate cyclase, cAMP-dependent protein kinase, protein kinase C (PKC), and IP3 receptors, respectively. Approximately 20% reductions in [3H]QNB, [3H]forskolin, and [3H]PDBu binding were observed in the hippocampus of 9-month-old gerbils in comparison with 5-week-old gerbils. Treatment with Naftidrofuryl (10 mg/kg, i.p., once a day for 7 days) ameliorated these reductions. No changes were found in [3H]CHA, [3H]MK-801, [3H]muscimol, [3H]PN200-110, [3H]cAMP, and [3H]IP3 binding. The results suggest that Naftidrofuryl may have beneficial effects on the age-related alterations in signal transmission and transduction systems in the brain. Because the acetylcholine system, adenylate cyclase, and PKC are considered to be involved in learning and memory processes, the result may have clinical implications.  相似文献   
25.
Following cardiac surgery, approximation of sternum will produce systemic hypotension or elevation of left atrial and central venous pressures. A new criteria for delayed sternal closure is proposed. Sternal closure has to be delayed when mean left atrial or central venous pressures increased over 2 mmHg at the tentative closure. In seven cases (3.5%) of consecutive 201 patients was delayed the sternal closure under the above mentioned state, all survived and received the successful closure later. One of them died of congestive heart failure four months after the operation and one died of the rupture of the ascending aortic pseudoaneurysm eleven months after the initial operation. Microbiological examination of the mediastinal and pericardial contents obtained at the final sternal closure were negative in all cases. Comparing the total cardiopulmonary bypass time, ventricular fibrillation time, and myocardial ischemic time between in the secondary closure group and in the primary closure group, the total bypass time and the ventricular fibrillation time of the former were significantly longer than the latter, but the ischemic time revealed no difference. In conclusions, persistent elevation of left atrial or central venous pressures after cardiac surgery at the tentative sternal closure seems the reliable predictor for the delayed closure of the sternum. Careful post-operative management prevents serious mediastinal infection. Delayed sternal closure is preferable procedure for the patient with brittle hemodynamics after open heart surgery.  相似文献   
26.
Beta-core fragment (beta-CF), a fragment of the hCG beta-subunit missing its carboxyterminal peptide, can be detected in the urine of women throughout pregnancy or in trophoblastic disease. It is also found in the urine of patients with nontrophoblastic cancers. We examined the beta-CF level in urine samples from patients with cervical cancer and assessed its value as a tumor marker. beta-CF was measured by an enzyme immunoassay with hCG beta-core directed monoclonal antibody No. 229. Based on the cut-off value (0.2ng/ml) from control subjects, the overall positivity rate for urinary beta-CF in the cervical cancer group was 45% (57 of 128 patients), increasing from 32% (23 of 73) in stage I to 100% (2 of 2) in stage IV. These positivity rates exceeded or equaled those of the other markers, SCC, CEA, CA19-9 and CA125, simultaneously measured in the patients' serum. There was no significant difference between the positivity rates for the two histological types of cancer, squamous cell carcinoma and adenocarcinoma. Serial determination in 28 patients with increased urinary beta-CF prior to therapy showed that 24 patients had a decreased concentration after successful treatment, but 2 of 4 patients with still increased urinary beta-CF during or after treatment subsequently relapsed. The determination of urinary beta-CF may provide a useful tool in monitoring the response to treatment in patients with cervical cancer.  相似文献   
27.
28.
A case of Vibrio cholerae non-O1 septicemia is described in this paper. A 45-year-old male with a three year history of liver cirrhosis, was admitted to our division with hematemesis, abdominal pain, high fever and a loss of consciousness. Three days before onset of symptoms, he traveled to Ishigaki Island and ate a raw lobster. Two days after, his temperature rose to 39.7 degrees C and the blood pressure dropped to 36/- mmHg. By endoscopic examination, an ulcer was found in the stomach, and the bleeding was stopped by electrical coagulation. Blood culture showed growth of V. cholerae non-O1. The organism was found to be sensitive to OFLX, CZX, MINO, LMOX and CP. Although DIC, infections of fungus and MRSA occurred as complications, he recovered by adequate procedures. Subsequently, he left this division after eight weeks. There are various reports related to V. cholerae non-O1 septicemia in foreign countries, but few cases have been reported in Japan. And these cases had severe underlying diseases such as leukemia and liver cirrhosis.  相似文献   
29.
Electrogastrograms (EGGs) were recorded in patients both before and after receiving proximal gastrectomy plus jejunal interposition (PGJI) or just after receiving total gastrectomy plus jejunal interposition (TGJI). Intraluminal pressure was also recorded in some postoperative patients. The EGG 3 cpm component (2.5-4.9 cpm) remained after PGJI, but subsequently decreased with a significant reduction in the preoperative to postoperative ratio of the 3 cpm components (P<0.05). The mean frequency of the 3 cpm components increased significantly after PGJI (P<0.05) and its instability factor increased. The EGG 10 cpm components became relatively dominant compared to other frequency components in 2 out of 8 of patients having PGJI but the mean amplitude of 10 cpm decreased. In TGJI patients, only the 10 cpm component was conspicuous in EGG as in the case of total gastrectomy and Roux en Y anastomosis procedures. The spectral frequencies of intraluminal pressure in the interposed jejunum were similar to the EGG of 10 cpm components both in the case of PGJI and TGJI patients. In conclusion, surface EGG could record the electrical activities of the interposed jejunum more easily in patients having had TGJI than in PGJI.  相似文献   
30.
Aortic allograft valves were harvested from non-infected (bacterial or viral) cadavers within 24 hours of death with a family consent, and were sterilized by 4 degrees C antibiotic solution for 48 hours. Then, the allograft was preserved in the 4 degrees C nutrient medium (fresh; TC-199, calf serum and HEPES buffer) or in liquid nitrogen (-196 degrees C) after freezing to -80 degrees C by a programmed freezer. 10% dimethylsulfoxide (DMSO) was used for cryopreservation. Following germ-free confirmation, aortic allograft valves were implanted in 5 patients having aortic regurgitation with good results. Three fresh and two cryopreserved allograft valves were used. Although the follow-up term is very short (maximum 1 year) at the present time, the valve function is quite satisfactory, confirmed by cardiac catheterization and echocardiography. This is the first report in Japan with regard to cryopreservation of allograft valves and clinical use of fresh or cryopreserved valves. We believe that realization and progress of allograft preservation by cryo-technique and establishment of the tissue bank are important for the development of cardiovascular surgery in Japan.  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