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   593篇
  免费   75篇
  国内免费   22篇
儿科学   73篇
妇产科学   14篇
基础医学   148篇
口腔科学   9篇
临床医学   68篇
内科学   133篇
皮肤病学   4篇
神经病学   13篇
特种医学   75篇
外科学   30篇
综合类   18篇
一般理论   1篇
预防医学   42篇
眼科学   1篇
药学   25篇
中国医学   6篇
肿瘤学   30篇
  2021年   6篇
  2018年   5篇
  2015年   8篇
  2014年   8篇
  2013年   18篇
  2012年   6篇
  2011年   14篇
  2010年   17篇
  2009年   8篇
  2008年   22篇
  2007年   34篇
  2006年   28篇
  2005年   19篇
  2004年   12篇
  2003年   8篇
  2002年   17篇
  2001年   5篇
  2000年   7篇
  1999年   14篇
  1998年   20篇
  1997年   25篇
  1996年   15篇
  1995年   17篇
  1994年   12篇
  1993年   13篇
  1992年   7篇
  1991年   8篇
  1990年   11篇
  1989年   22篇
  1988年   17篇
  1987年   11篇
  1986年   26篇
  1985年   9篇
  1984年   9篇
  1983年   13篇
  1982年   11篇
  1981年   8篇
  1980年   9篇
  1979年   8篇
  1978年   19篇
  1977年   17篇
  1976年   11篇
  1975年   10篇
  1974年   13篇
  1973年   12篇
  1972年   14篇
  1971年   11篇
  1970年   11篇
  1969年   9篇
  1967年   8篇
排序方式: 共有690条查询结果,搜索用时 15 毫秒
1.
Intratemporal vascular tumors: detection with CT and MR imaging   总被引:1,自引:0,他引:1  
The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.  相似文献   
2.
3.
Thirty-five patients hospitalized for recent angiographically documented arterial occlusion in the legs (27 femoropopliteal arteries and eight grafts) benefited from local fibrinolytic therapy delivered at the site of the occlusion with a 4- or 5-F catheter. This therapy combined a continuous urokinase (UK) infusion of 1,000 U/kg/hour and a lysyl plasminogen (LYS-PLG) infusion of 15 microkatals every 30 minutes. Angiographically confirmed lysis was obtained in 85% of the cases. Only 3% of the patients had major and 6% had minor groin hematomas. Only two patients had concentrations of fibrinogen as low as 100 mg/dl. Intravascular infusion of UK-LYS-PLG is as effective as streptokinase. Its excellent tolerance makes it a good alternative in the treatment of acute ischemia in the lower limbs.  相似文献   
4.
5.
Although nausea and vomiting are diagnostic migraine symptoms, most patients can take tablets by mouth and a few say they can eat some food. This study was conducted to determine the proportion who could eat or drink, what was consumable and with what effect. One-hundred-and-nine migraineurs were asked what they could eat or drink at the beginning or height of their attacks; 59 could not take any food by mouth, but 50 could eat during the headache phase of their migraine attacks. Four ate normally, 5 took smaller amounts of their normal dietary intake, and 3 took lighter meals. Dry, carbohydrate foods were consumable by the remaining 38: a few had specific cravings, most stated the precise variety which, when eaten, reduced nausea, headache, other symptoms or length of attacks. Patients should therefore be encouraged to eat what they can tolerate, with their tablets taken as early as possible after the onset of attacks. Simultaneous nausea, tolerance or even craving for specific foods occur in other conditions, particularly high altitude headaches which share other features of migraine attacks. The observations in this paper support the notion that migraine is a central neuronal metabolic disturbance.  相似文献   
6.
The CYP19 gene encodes for aromatase (P450arom), a key steroidogenic enzyme that catalyzes the final step of estrogen biosynthesis. Apart from rare mutations in CYP19 which result in severe phenotypes associated with estrogen insufficiency, little is known about whether common variation in CYP19 is associated with risk of hormone-related diseases. In this study, we employed a haplotype-based approach to search for common disease-associated variants in this candidate breast cancer susceptibility gene among African-American, Hawaiian, Japanese, Latina and White women in the Multiethnic Cohort Study (MEC). We utilized 74 densely spaced single-nucleotide polymorphisms (SNPs) (one every approximately 2.6 kb) spanning 189.4 kb of the CYP19 locus to characterize linkage disequilibrium (LD) and haplotype patterns among 69-70 individuals from each ethnic population. We detected four regions of strong LD (blocks 1-4) that were quite closely conserved across populations. Within each block there was a limited diversity of common haplotypes (5 to 10 with a frequency >/=5%) and most haplotypes were observed to be shared across populations. Twenty-five haplotype-tagging SNPs (htSNPs) were selected to predict the common haplotypes with high probability (average Rh2=0.92) and genotyped in a breast cancer case-control study in the MEC (cases, n=1355; controls, n=2580). We first performed global tests for differences in risk according to the common haplotypes and observed significant haplotype-effects in block 2 [P=0.01; haplotypes 2b (OR=1.23; 95% CI, 1.07-1.40), 2d (OR=1.28; 95% CI, 1.01-1.62)]. We also found a common long-range haplotype comprised of block-specific haplotypes 2b and 3c to be associated with increased risk of breast cancer (haplotype 2b-3c: OR=1.31; 95% CI, 1.11-1.54). Our findings suggest the hypothesis that women with the long-range CYP19 haplotype 2b-3c may be carriers of a predisposing breast cancer susceptibility allele.  相似文献   
7.
The dried leaves of Combretum and Terminalia species (Combretaceae) were extracted with acetone, hexane, dichloromethane and methanol. Thin layer chromatography (TLC) plates were developed under saturated conditions and sprayed with 0.2% 2,2-diphenyl-1-picryl hydrazyl (DPPH) in methanol for antioxidant screening. Visualization of separated bands exhibiting antioxidant activities enabled the localization and the subsequent identification of the potential active compounds. The acetone and methanol extracts displayed the presence of antioxidant activity after spraying the chromatogram with DPPH. Hexane and dichloromethane extracts did not have any antioxidant activity. C. hereroense had the highest number of active compounds, followed by C. collinum ssp. taborense, which were 16 and 10, respectively. Acetone extracts of all tested Combretum species had 53 active bands and methanol had 55. All Terminalia species extracted with acetone and methanol had antioxidant activity. T. gazensis and T. mollis methanol extracts had 11 and 14 active compounds respectively in one of the solvent systems used. The qualitative DPPH assay on TLC was successfully used in this study to systematically assess the total antioxidant activity of the Combretum and Terminalia species extracts.  相似文献   
8.
With combination of C and G banding techniques, three morphologically different types of isochromosome for the long arm of X (Xqi) have been identified, i.e. those with one C-band and symmetrical banding patterns of both arms, those with two C-bands and symmetrical banding patterns of two arms, and those with two C-bands but with asymmetrical banding patterns of two arms. The last type is a heterogeneous group with various different asymmetrical patterns. We have studied 6 cases of Xqi with C, G, and Q banding: 3 showed one C-band and symmetrical arms and all these were without 45,X mosaicism; the other 3 cases showed two C-bands, 2 of the cases having symmetrical arms and being mosaic for 45X/46,XXqi/47,XXqiXqi (those 2 were a pair of identical twins). One other had asymmetrical arms and was mosaic for 45,X/46,XXqi. Including our 6 cases, there have been a total of 30 reported cases of Xqi with C and G banding studies. Two-thirds of Xqi's were found to have 2 C-bands and one-third to have 1 C-band. Mosaicism was found in 85% of Xqi's with 2 C-bands and in only 44% of Xqi's with 1 C-band. Apparently, Xqi's with 2 C-bands have a greater tendency for anaphase lag and mitotic nondisjunction. Several possible mechanisms for the formation of the different types of Xqi's are discussed.  相似文献   
9.
The syndrome of ectrodactyly, ectodermal dysplasia and cleft lip and palate (EEC syndrome) is described in a mother and 3 of her 4 children. Autosomal dominant inheritance was suggested in this family. However, genetic heterogeneity may exist in this syndrome. The significance of associated finClings, incluCling carcinoma of the cervix uteri, lacrimal duct stenosis and urinary tract strictures in patients with ectodermal dysplasia is considered.  相似文献   
10.
Thymidine kinase-deficient syrian hamster cells were cotransfected with recombinant plasmids containing the thymidine kinase (TK) gene of Herpes Simplex Virus Type 1, and either intact or partially deleted SV40 T antigen-coding genes. The transformants were selected by their ability to grow in gHAT medium. After selection and cloning, the TK-positive transformants that also expressed T antigen were tested for the extent of their transformation with respect to a number of characteristics, which included saturation density, ability to grow in soft agar, resistance to butyrate and to dibutyryl-cAMP, and plating efficiency. The combined results of these various tests indicate that cells containing partially deleted SV40 T antigen-coding genes are less transformed than cells containing an intact SV40 T antigen-coding gene. However, the amounts of T antigen are lower in cells transformed by deletion mutants than in cells transformed by wild-type T antigen-coding gene. Our data indicate that both the quantity and the quality of T antigen may be important in determining the degree of transformation in Syrian hamster cells.  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