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   4993篇
  免费   487篇
  国内免费   389篇
耳鼻咽喉   37篇
儿科学   32篇
妇产科学   42篇
基础医学   674篇
口腔科学   83篇
临床医学   713篇
内科学   740篇
皮肤病学   44篇
神经病学   243篇
特种医学   189篇
外科学   393篇
综合类   896篇
现状与发展   2篇
一般理论   2篇
预防医学   343篇
眼科学   202篇
药学   577篇
  5篇
中国医学   250篇
肿瘤学   402篇
  2024年   11篇
  2023年   76篇
  2022年   191篇
  2021年   304篇
  2020年   224篇
  2019年   158篇
  2018年   194篇
  2017年   186篇
  2016年   156篇
  2015年   245篇
  2014年   319篇
  2013年   284篇
  2012年   390篇
  2011年   453篇
  2010年   256篇
  2009年   206篇
  2008年   272篇
  2007年   230篇
  2006年   241篇
  2005年   250篇
  2004年   147篇
  2003年   159篇
  2002年   123篇
  2001年   102篇
  2000年   107篇
  1999年   112篇
  1998年   64篇
  1997年   36篇
  1996年   54篇
  1995年   46篇
  1994年   32篇
  1993年   27篇
  1992年   22篇
  1991年   29篇
  1990年   21篇
  1989年   27篇
  1988年   16篇
  1987年   13篇
  1986年   20篇
  1985年   14篇
  1984年   7篇
  1983年   7篇
  1982年   4篇
  1980年   4篇
  1979年   3篇
  1978年   4篇
  1975年   4篇
  1974年   3篇
  1971年   2篇
  1967年   2篇
排序方式: 共有5869条查询结果,搜索用时 15 毫秒
1.
This study investigated the hypocholesterolaemic effects of bitter melon aqueous extracts (BMAE) in vitro, the inhibitory effects of BMAE on pancreatic cholesterol esterase (CEase) and incorporation of cholesterol into micelles were investigated. BMAE decreased the in vitro micellar solubility of cholesterol in a dose-dependent manner. The conformation of CEase was investigated by means of circular dichroism (CD) and fluorescence. The result revealed the decrease of α-helix contents, increase of β-sheet and exposure of aromatic amino acid residuals. The incorporation of cholesterol into micelles was inhibited by BMAE. A complex was observed by transmission electron microscopy (TEM), which indicated interaction between cholesterol and BMAE. The result revealed that BMAE can play a role in decreased intestinal cholesterol absorption via inhibition of CEase, and of micelle formation.  相似文献   
2.
白纹伊蚊在竹林里孳生的阳性比为75.4%;而在竹林包围的居民区阳性比为15.3%。白纹伊蚊在居民区孳生密度布雷图指数为19.4,容器指数为6.2%。居民区孳生蚊虫的主要场所是泡菜坛,泡菜坛主要孳生蚊种是骚扰阿蚊,阳性比为73.7%,其次是淡色库蚊为20.2%,贪食库蚊为14.0%,白纹伊蚊最低,为9.1%。  相似文献   
3.
Our objective was to develop and evaluate 3 semiautomatic computer-aided diagnostic (CAD) schemes for distinguishing between benign and malignant pulmonary nodules by use of features extracted from CT, 18F-FDG PET, and both CT and 18F-FDG PET. METHODS: We retrospectively collected 92 consecutive cases of pulmonary nodules (<3 cm) in patients who underwent both thoracic CT and whole-body PET/CT. Forty-two of the nodules were malignant and 50 benign, as confirmed by pathologic examination and clinical follow-up. The interval between CT and PET was less than 1 mo. Four clinical parameters, including patient age, sex, smoking status, and history of previous malignancy, were used for the CAD schemes. Sixteen CT features based on size, shape, margin, and internal structure of nodules were independently rated subjectively by 2 chest radiologists. Four PET features were viewed on a PET/CT workstation. CAD schemes based on clinical parameters together with CT features, PET features, and both CT and PET features were then used to differentiate benign from malignant nodules. Finally, the output from the CAD schemes was evaluated by use of receiver-operating-characteristic analysis. RESULTS: When we used clinical parameters and CT features as input units (CAD scheme 1), the area under the receiver-operating-characteristic curve (A(z) value) of the CAD scheme was 0.83. When we used clinical parameters and PET features as input units (CAD scheme 2), the A(z) value for the computer output was 0.91. However, when we used all data as input units (CAD scheme 3), the A(z) value for the computer output was 0.95. The performance of CAD scheme 3 was better than that of CAD scheme 1 or 2. A statistically significant difference existed between the A(z) values of CAD schemes 3 and 2 (P = 0.037) and between those of CAD schemes 3 and 1 (P = 0.015). CONCLUSION: Our CAD scheme based on both PET and CT was better able to differentiate benign from malignant pulmonary nodules than were the CAD schemes based on PET alone and CT alone.  相似文献   
4.
Changes in T .lymphocyte subsets after severe traumatic brain inJury   总被引:2,自引:0,他引:2  
BACKGROUND: Besides local changes of cranial parenchymal cells, hemorrhage, etc., severe traumatic brain injuries also cause the changes of total body fluid and various functions, and the changes of lymphocytes and T lymphocyte subsets should be paid more attention to. OBJECTIVE: To reveal the changing laws of T lymphocyte subsets after severe traumatic brain injury, and compare with mild to moderate brain injury. DESIGN: A comparative observation. SETTINGS: Department of Neurosurgery, Longgang District Buji People's Hospital of Shenzhen City; Central Laboratory of Shenzhen Hospital of Prevention and Cure for Chronic Disease. PARTICIPANTS: All the subjects were selected from the Department of Neurosurgery, Longgang District Buji People's Hospital of Shenzhen City from August 2002 to August 2005. Thirty patients with severe brain injury, whose Glasgow coma score (GCS) was ≤ 8 points, were taken as the experimental group, including 21 males and 9 females, aging 16 - 62 years. Meanwhile, 30 patients with mild traumatic brain injury were taken as the control group (GCS ranged 14- 15 points), including 18 males and 12 females, aging 15 -58 years. All the subjects were in admission at 6 hours after injury, without disease of major organs before injury Informed consents were obtained from all the patients or their relatives. METHODS: (1) The T lymphocytes and the subsets in peripheral blood were detected with immunofluorescent tricolor flow cytometry at l, 3, 7 and 14 days after injury in both groups. (2) The conditions of pulmonary infections were observed at 4 days after injury. The differences of measurement data were compared with the t test. MAIN OUTCOME MEASURES: Changes of T lymphocytes subsets at 1 - 14 days after severe and mild or moderate traumatic injury. RESULTS: Finally, 28 and 25 patients with mild to moderate traumatic brain injury, whereas 25 and 21 patients with severe traumatic brain injury were analyzed at 7 and 14 days respectively, and the missed ones died due to the development of disease. (1) Changes of T lymphocyte subsets: At 1 and 3 days after injury, CD3, CD4, CD8, CD4/CD8 began to decrease, whereas CD8 increased in the experimental group, which were very significantly different from those in the control group (t =2.77 - 3.26, P 〈 0.01), and began to recover at 7 days, which were significantly different from those in the control group (t = 2.06 - 2.24, P 〈 0.05), and generally recovered to the normal levels at 14 days (P 〉 0.05). (2) Conditions of pulmonary infections: At 4 days after injury, the rate of pulmonary infection was significantly different between the experimental group and control group [73% (22/30), 0, x2=37.29, P 〈 0.01]. CONCLUSION: Patients with severe traumatic brain injury suffer from damages of cellular immune function at early period (within 7 days), and they are easily to be accompanied by pulmonary infections.  相似文献   
5.
谷氨酸诱导体外培养的鸡胚脊髓神经细胞释放NO   总被引:1,自引:0,他引:1  
用鸡胚脊髓神经细胞的原代培养,测定细胞中亚硝酸盐的含量,研究了谷氨酸(Glu)对原代培养神经细胞中NO的影响。结果表明,谷氨酸作用于原代培养的鸡胚脊髓神经细胞,在诱导神经细胞释放乳酸脱氢酶(LDH)的同时,还可诱导细胞释放一氧化氮(NO)。如先用NO合成酶抑制剂L-NOARG作用细胞,再加入Glu,则发现L-NOARG能降低Glu导致的培养液中LDH活性升高。提示NO可能参与介导Glu的神经毒性作用。  相似文献   
6.
目的 研究脑梗死急性期降压及在不同时间进行降压治疗对患者近期预后的影响.方法 据发病后是否降压及进行降压的时间,将198例急性脑梗死患者分为6组,观察各组患者神经功能缺损程度及心脑血管事件的再发生率和病死率.结果 在发病后进行降压治疗的患者中其心脑血管事件再发率和病死率明显低于未降压组(P<0.01) 3d后降压组患者神经功能恢复的程度明显好于未降压组(P<0.01).结论 降压治疗可以降低患者心脑血管事件的发生率和病死率3d后进行降压治疗的患者神经功能恢复明显要好.  相似文献   
7.
聂利民 《医药论坛杂志》2003,24(12):22-22,24
目的:探讨重症胆管(ACST)患者的临床特点及死亡原因。方法:分析我院近十五年来收治46例ACST的治疗情况。结果:手术41例.非手术5例,死亡9例,其中手术治疗死亡6例。结论:老年ACST患者,伴发病多,死亡率高,及时就诊,早期应用大量激素,选择适宜手术方法是降低死亡率的关键。  相似文献   
8.
We experienced two cases of left ventricular free wall rupture (LVFWR) following acute myocardial infarction (AMI). Case 1, with the blowout type of LVFWR was initially closed by direct suture, followed by hemostasis using a double patch sealing method (DPS) by which the tear was doubly sealed with large and small bovine pericardium patches to which GRF glue was applied. Case 2 with the oozing type of LVFWR was treated only using DPS. Complete hemostasis was achieved in both cases, and aneurysmal dilatation or constrictive heart failure were not detected by postoperative left ventriculography. Therefore, DPS may be useful for treating LVFWR following AMI.  相似文献   
9.
来自不同疟疾疫区——长沙、上海、郑州、武汉四地区的中华按蚊,分别以羊膜饲血法感染湖南慈利或湖北沔阳两地区的间日疟原虫,交叉对比其易感性。七次实验共解剖饲血蚊541只。实验结果显示:以腺感染率和阳性腺指数为主要指标,四地区中华按蚊对间日疟原虫的易感性基本相似:两地区间日疟原虫对中华按蚊的感染力也大致相同。并讨论了可能影响人工感染率的几个因素。  相似文献   
10.
报告335例退行性骨关节病变,均经 x 线摄影证实,用直流感应电治疗。痊愈62例,占18.51%;显效115例,占34.33%;好转139例,占41.49%;无效19例;占5.67%。总有效率94.33%。有复发者再经治疗仍可收到效果。并对作用机制进行了探讨。  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