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   7932篇
  免费   847篇
  国内免费   4篇
耳鼻咽喉   74篇
儿科学   189篇
妇产科学   129篇
基础医学   1117篇
口腔科学   286篇
临床医学   935篇
内科学   1581篇
皮肤病学   102篇
神经病学   599篇
特种医学   233篇
外科学   1200篇
综合类   208篇
一般理论   6篇
预防医学   807篇
眼科学   194篇
药学   633篇
中国医学   1篇
肿瘤学   489篇
  2021年   88篇
  2020年   59篇
  2019年   102篇
  2018年   118篇
  2017年   121篇
  2016年   121篇
  2015年   131篇
  2014年   132篇
  2013年   239篇
  2012年   353篇
  2011年   380篇
  2010年   228篇
  2009年   195篇
  2008年   310篇
  2007年   348篇
  2006年   342篇
  2005年   373篇
  2004年   298篇
  2003年   350篇
  2002年   305篇
  2001年   250篇
  2000年   280篇
  1999年   234篇
  1998年   91篇
  1997年   102篇
  1996年   86篇
  1995年   88篇
  1994年   98篇
  1993年   83篇
  1992年   194篇
  1991年   174篇
  1990年   162篇
  1989年   163篇
  1988年   155篇
  1987年   154篇
  1986年   138篇
  1985年   158篇
  1984年   114篇
  1983年   104篇
  1982年   73篇
  1981年   71篇
  1980年   59篇
  1979年   110篇
  1978年   69篇
  1977年   74篇
  1973年   85篇
  1972年   74篇
  1971年   73篇
  1970年   61篇
  1968年   59篇
排序方式: 共有8783条查询结果,搜索用时 15 毫秒
21.
22.
23.
关于欧洲联盟(欧盟,EU)2007年至2013年财政构架方面的持续论战使欧盟的公共卫生团体感到恐慌,他们认为这个构架对整个欧洲执行有效的公共卫生措施是一个威胁。[第一段]  相似文献   
24.
Twenty-one patients with advanced metastatic carcinoma of the prostate, no longer responsive to conventional therapy, were treated with weekly low-dose doxorubicin (Adriamycin). Twelve had an impressive subjective response in terms of pain relief and improved performance status and in nine this was maintained for 3 or more months.  相似文献   
25.
M Kaszkin  J Richards  V Kinzel 《Cancer research》1992,52(20):5627-5634
Epidermal growth factor (EGF) has been shown to cause an inhibition of A431 cells in G2 phase within approximately 10 min, i.e., shortly before mitosis (Kinzel et al., Cancer Res., 50: 7932-7936, 1990). This system has been used to study the proposed role phospholipid metabolites, particularly phosphatidic acid (PA), may play (Kaszkin et al., Cancer Res., 51: 4328-4335, 1991) in the extracellular control of cells at the physiological restriction site in G2 phase. A431 cells responded to EGF with a dose-dependent formation of phosphatidic acid (PA) which correlated with the dose-dependent G2 delay as well as with their time courses. The G2 delay induced by EGF as well as PA mobilization were effected in conditioned medium or in fresh medium containing bovine serum albimun instead of serum, i.e., under the conditions necessary for precursor studies to be carried out. The major pathway of PA formation was probably via phospholipase C-mediated breakdown of phosphatidylinositol and diacylglycerol kinase: (a) the dose response of PA formation correlated with that of total inositol phosphate accumulation; (b) little diacylglycerol was found and then only at a high EGF concentration; (c) prelabeling with [1-14C]arachidonic acid resulting in a large specific labeling of phosphatidylinositol led to an EGF-induced, dose-dependent formation of radioactive arachidonyl-PA (correlated with that of total PA and inositol phosphate), but in the presence of a primary alcohol not to the formation of radioactive phosphatidylalcohol; (d) prelabeling with [1-14C]oleic acid led to the EGF-induced formation of labeled PA, which in the presence of a primary alcohol was only slightly reduced to the advantage of very low levels of labeled phosphatidyl alcohol, thus demonstrating that an EGF-effected activation of phospholipase D did occur but contributed little to the general PA level. An alternative mobilization of PA was attempted with the phorbolester 12-O-tetradecanoylphorbol-13-acetate (TPA), which was shown to activate phospholipase D in A431 cells and to elicit PA from a phospholipid pool which was not significantly labeled with radioactive arachidonic acid. The TPA-induced degree of PA formation and of the G2 delay correlated. Both phenomena were considerably larger with fresh medium containing 0.5% bovine serum albumin instead of serum than in conditioned medium.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
26.
Despite the widespread use of liquid nitrogen, there are few reports of injuries caused by the use of this substance. We report a case in which a severe liquid nitrogen burn, requiring digital amputation, occurred despite the wearing of protective gloves. This case illustrates the potential dangers of working with liquid nitrogen, and raises questions as to whether adequate precautions are being taken to prevent such injuries.  相似文献   
27.
28.
Principal component analysis (PCA) and independent component analysis (ICA) were examined in their ability to recover dipole sources from simulated data. Datasets of EEG segments were generated that contained cortical sources that were temporally overlapping or non-overlapping, and dipole sources with varying degree of spatial orthogonality. For temporal overlapping sources, both PCA and ICA resulted in components that required multiple-source equivalent current dipole models. The spatially overlapping sources affected the PCA method more than ICA, resulting in single PCA components in which all non-orthogonal sources were represented. For both PCA and ICA, dipole models with fixed-location dipoles successfully accounted for most of the variance in the component weights, even when the spatial or temporal overlap of the generating sources required multiple-dipole models.  相似文献   
29.
30.
The sonographic appearances in postpartum thyroiditis.   总被引:2,自引:0,他引:2  
During the postpartum period about 50% of women with circulating thyroid autoantibodies develop a transient autoimmune thyroiditis. To determine the sonographic appearances in postpartum thyroiditis (PPT), serial ultrasound (US) scans of the thyroid were performed in 135 postpartum women who were divided into three clinical groups: Group 1, 37 antibody positive subjects who developed PPT; Group 2, 28 antibody positive subjects in whom thyroid function remained normal; Group 3, 70 antibody negative controls. Thyroid hypoechogenicity was observed in 14/31 patients (45%) who were scanned between 4 and 8 weeks postpartum and who subsequently developed PPT (Group 1) compared with 4/24 patients (17%) in Group 2 (P less than 0.05) and 1/65 patients (1.5%) in Group 3 (P less than 0.001). In antibody positive patients, the positive predictive value of an abnormal scan during this period was 78%. Between 15 and 25 weeks postpartum thyroid hypoechogenicity was present in 32/37 patients (86%) in Group 1 compared with 11/28 patients (39%) in Group 2 (P less than 0.001) and 2/70 patients (3%) in Group 3 (P less than 0.001). Sonographic abnormality persisted beyond 32 weeks postpartum in 36/41 antibody positive patients (87%) who had exhibited thyroid hypoechogenicity earlier during the study and who had late scans. The characteristic US appearance in PPT is thyroid hypoechogenicity. The role of sonography in the prediction, diagnosis and follow up of patients with PPT is discussed.  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