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   2793篇
  免费   131篇
  国内免费   11篇
耳鼻咽喉   5篇
儿科学   110篇
妇产科学   108篇
基础医学   334篇
口腔科学   32篇
临床医学   154篇
内科学   719篇
皮肤病学   31篇
神经病学   335篇
特种医学   169篇
外国民族医学   10篇
外科学   343篇
综合类   6篇
预防医学   83篇
眼科学   12篇
药学   121篇
中国医学   3篇
肿瘤学   360篇
  2022年   17篇
  2021年   53篇
  2020年   47篇
  2019年   43篇
  2018年   53篇
  2017年   27篇
  2016年   52篇
  2015年   63篇
  2014年   71篇
  2013年   91篇
  2012年   143篇
  2011年   164篇
  2010年   87篇
  2009年   87篇
  2008年   127篇
  2007年   130篇
  2006年   161篇
  2005年   133篇
  2004年   110篇
  2003年   113篇
  2002年   113篇
  2001年   95篇
  2000年   99篇
  1999年   96篇
  1998年   35篇
  1997年   22篇
  1996年   31篇
  1995年   25篇
  1994年   20篇
  1993年   14篇
  1992年   68篇
  1991年   49篇
  1990年   65篇
  1989年   42篇
  1988年   42篇
  1987年   43篇
  1986年   31篇
  1985年   30篇
  1984年   31篇
  1983年   15篇
  1981年   13篇
  1980年   13篇
  1979年   22篇
  1978年   12篇
  1977年   12篇
  1976年   15篇
  1975年   16篇
  1974年   12篇
  1973年   10篇
  1972年   13篇
排序方式: 共有2935条查询结果,搜索用时 46 毫秒
1.
2.
3.
Male Sprague-Dawley rats injected (i.p.) at 1500h with L-acetyl-carnitine in doses of 10, 30 or 90 mg/kg exhibited a notable increase in their pineal and serum melatonin content 1 hr later. Likewise, L-acetyl-carnitine administered in the same dose range induced a significant increase of pineal and serum melatonin content in rats treated at 0100h, following exposure of 30 min to bright white light to suppress endogenous melatonin. Under in vitro experimental conditions, however, 60 min of coincubation of isolated rat pineal glands with L-acetyl-carnitine (10(-5) M) did not result in an elevation in melatonin accumulated in the incubation medium. These results demonstrate that, in vivo, L-acetyl-carnitine can exert a modulatory action on synthesis and release of melatonin, possibly by modifying noradrenergic transmission and signal transduction in the pineal gland.  相似文献   
4.
Mariani  C.  Defendi  S.  Mailland  E.  Pomati  S. 《Neurological sciences》2006,27(1):s35-s36
Neurological Sciences - Frontotemporal dementia is a clinicopathological syndrome caused by progressive degeneration of the frontal lobes, anterior temporal lobes or both. A wide spectrum of...  相似文献   
5.
Bone scintigraphy plays a major role in the diagnosis of bone metastases. The clinical utility of new biochemical markers of bone metabolism has recently been investigated in various bone diseases. This study evaluated the role of some bone metabolism markers in comparison with bone scan in the follow-up of breast cancer patients. We studied 149 patients with breast cancer, 33 (22%) of whom had bone metastases. IRMAs were used for the evaluation of blood levels of osteocalcin, bone alkaline phosphatase (BAP), the C-terminal propeptide of type I procollagen and the C-terminal cross-linked telopeptide of type I collagen (ICTP). Multivariate regression analysis showed that menopausal status (P=0.007) and metastatic bone lesions (P=0.001) affected bone marker levels. When considering post-menopausal women, the only subset in which bone metabolism marker behaviour could be reliably investigated, we found a high degree of overlap in marker distribution for scan-positive and scan-negative patients. Discrimination between scan-negative and scan-positive patients based on the above markers, taken singly or jointly, was assessed by means of logistic discriminant analysis. The best discrimination was achieved with BAP, closely followed by ICTP. BAP and ICTP together gave a slight improvement over the use of the two markers separately. However, even in this case the degree of discrimination was poor and its clinical utility was limited. In fact, to achieve a specificity of 95%, the sensitivity of the test was about 20%; conversely, with a sensitivity of 95%, the specificity was below 10%. In conclusion, based on our findings, we believe that blood levels of the investigated markers cannot replace bone scintigraphy in the follow-up of breast cancer patients for the early detection of bone metastases. Received 14 April and in revised form 5 July 1997  相似文献   
6.
7.
The aim of this study was to analyze the characteristics of 17 women with renal-cell carcinoma (RCC) associated with other primary neoplasms occurring in steroid-hormone target tissues. The reproductive history of these patients and the use of exogenous hormones were taken into consideration. In all, 10 RCCs were associated with breast carcinoma; 4, with endometrial carcinoma; and 3, with ovarian carcinoma. The presentation of a second primary tumor was described as synchronous or metachronous by evaluation of the interval between the discovery of the two neoplasms. Hormone and surgical treatment as well as pathologic findings for each primary tumor were also reported. In these 17 RCCs the overall rate of disease-specific survival recorded after a mean follow-up period of 32.7 months (range 9–66 months) was 58.8%; 7 patients died of metastatic disease after surviving for a mean of 14.7 months. In terms of the pathologic stage of RCC, a significant difference in mean survival was found between pN0 (mean survival 22.1 ± 3.4 months) and pN 1 RCCs (mean survival 13.7 ± 3.5 months). A total of 13 (76.4%) women were postmenopausal at the time of diagnosis of the first primary tumor; the mean age of these women at menopause was 51.7 ± 1.2 years. No prior use of oral contraceptives was reported by 12 (70.5%) of the 17 patients. Plasma 17-beta-estradiol and estrone levels were determined in only 7 patients at the diagnosis of each of the primary tumors. High plasma estrogen levels were found in 4 women with RCC and breast carcinoma and in 1 patient with RCC and endometrial carcinoma; in the remaining 2 patients low-normal values were found. A relationship appears to exist between certain reproductive and hormone-related factors and the risk of developing these tumor associations. Data emerging from the present study do not provide strong support for the hypothesis of hormone dependency of RCC; however, a role for estrogens in cases in which RCC is associated with other primary tumors involving steroid-hormone target tissues can be hypothesized.  相似文献   
8.
The aim of the present study was to examine the phenotypic heterogeneity of murine and human melanoma cell lines with particular reference to anticancer drug sensitivity, growth pattern and susceptibility to lysis by lymphokine (rIL2) activated killer (LAK cells). Clones selected for a different drug sensitivity were tested to evaluate the stability of such properties after different in vitro passages. A possible relationship between drug sensitivity and LAK susceptibility was also analyzed. The results indicated a high heterogeneity in murine and in human melanoma clones for all the parameters. However, drug sensitivity, which was stable although for only a few passages in an untreated human melanoma, was highly unstable in murine naturally or drug-induced resistant cells. Finally, whereas human drug-resistant clones were sensitive to lysis by LAK cells and an inverse correlation was found with the level of drug resistance, murine clones appeared to be LAK sensitive, and no correlation was found between the level of drug resistance and LAK sensitivity. Our data indicate a different stability in drug response of human and murine cells and a different behaviour of human and murine drug-resistant cells in response to LAK lysis.  相似文献   
9.
Twenty-seven shoulders (in 26 patients) that had surgical repair of a rupture of the long head of the biceps tendon between 1962 and 1981 were evaluated at three to 22 years after injury (mean, 13 years). Thirty similar patients had been treated nonsurgically and were evaluated two to 15 years (mean, 4.6 years) after tendon rupture. Biomechanical testing was performed on ten patients in the surgical group and 13 in the nonsurgical group. Residual arm pain was infrequent in both surgically and nonsurgically treated groups. Residual subjective weakness at the elbow was reported in four of the surgical group and in 20 of the nonsurgical group. Surgically treated patients returned to work later than nonsurgical patients; however, 11 in the nonsurgical group were not able to return to full work capacity, versus only two in the surgical group. On biomechanical testing, the nonsurgical group had lost a mean of 21% of supination strength and 8% of elbow flexion strength but had no weakness in grip, pronation, or elbow extension. The surgical group had lost no strength in any of these testing modes.  相似文献   
10.
The synthesis of some N,N-disubstituted 4-amino-5,6-dihydro-3-phenyl-2H-[1]benzothiepino [5,4-b]pyran-2-ones by reaction of phenylchloroketene with a series of N,N-disubstituted (E)-4-aminomethylene-3,4-dihydro-1-benzothiepin-5(2H)-ones, followed by dehydrochlorination of the primary adducts with DBN, is described. The 4-methylphenylamino derivative showed a local anesthetic activity in mice superior to that of lidocaine and the 4-morpholino derivative showed an antiarrhythmic activity in rats comparable to that of quinidine.  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