全文获取类型
收费全文 | 3157篇 |
免费 | 229篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 113篇 |
儿科学 | 115篇 |
妇产科学 | 93篇 |
基础医学 | 403篇 |
口腔科学 | 111篇 |
临床医学 | 360篇 |
内科学 | 400篇 |
皮肤病学 | 51篇 |
神经病学 | 263篇 |
特种医学 | 274篇 |
外科学 | 270篇 |
综合类 | 62篇 |
一般理论 | 1篇 |
预防医学 | 195篇 |
眼科学 | 106篇 |
药学 | 227篇 |
肿瘤学 | 365篇 |
出版年
2021年 | 23篇 |
2019年 | 31篇 |
2018年 | 41篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 35篇 |
2014年 | 52篇 |
2013年 | 98篇 |
2012年 | 89篇 |
2011年 | 95篇 |
2010年 | 80篇 |
2009年 | 59篇 |
2008年 | 89篇 |
2007年 | 115篇 |
2006年 | 135篇 |
2005年 | 141篇 |
2004年 | 120篇 |
2003年 | 108篇 |
2002年 | 91篇 |
2001年 | 86篇 |
2000年 | 86篇 |
1999年 | 116篇 |
1998年 | 66篇 |
1997年 | 53篇 |
1996年 | 63篇 |
1995年 | 53篇 |
1994年 | 58篇 |
1993年 | 51篇 |
1992年 | 89篇 |
1991年 | 80篇 |
1990年 | 91篇 |
1989年 | 93篇 |
1988年 | 79篇 |
1987年 | 91篇 |
1986年 | 61篇 |
1985年 | 64篇 |
1984年 | 56篇 |
1983年 | 58篇 |
1982年 | 51篇 |
1981年 | 34篇 |
1980年 | 35篇 |
1979年 | 56篇 |
1978年 | 40篇 |
1977年 | 33篇 |
1976年 | 42篇 |
1975年 | 29篇 |
1974年 | 36篇 |
1973年 | 21篇 |
1971年 | 17篇 |
1970年 | 21篇 |
排序方式: 共有3409条查询结果,搜索用时 343 毫秒
1.
D J Enscore J L Osborne J E Shaw 《Methods and findings in experimental and clinical pharmacology》1989,11(3):173-178
The in vitro and in vivo functionality of Catapres-TTS, a transdermal therapeutic system that delivers the alpha adrenergic receptor agonist clonidine, is discussed in terms of the drug transport kinetics and resultant plasma drug concentration profiles. The design of Catapres-TTS is presented as an optimization by which the best combination of system performance characteristics is obtained within the inherent limitations of the transdermal drug transport properties and the known pharmacokinetic and pharmacodynamic properties of the drug. Clonidine is a potent antihypertensive agent with a relatively low therapeutic index. For Catapres-TTS, the majority of control over the drug input rate resides within the system, rather than within the skin, which significantly reduces the variability in drug input rate and resulting plasma drug concentration both within and between patients. Moreover, the presence of a rate-control element in the system allows for patterning of the drug release rate. An initial bolus of drug is placed in the contact adhesive layer, where its transport into the skin is not inhibited by the rate control element in the system, for reduction in the time needed to achieve steady state drug input. The selection of the loading dose of drug is described as an optimization between the minimization of the lag time and the maintenance of constant plasma drug concentrations during the crossover period between system applications in chronic therapy. 相似文献
2.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence. 相似文献
3.
Variation in opinions of medical experts is a problem for both the legal and medical profession. This is particularly relevant in breast imaging. BreastScreen Queensland and New South Wales have developed a review protocol to assess ‘reasonableness’ of radiological opinions. It is hoped that the protocol will be acceptable to the courts and will result in a fair outcome for all parties involved in a medico-legal dispute. 相似文献
4.
5.
The effect of substance P and other tachykinins on inositol phospholipid hydrolysis in rabbit retina, superior colliculus and retinal cultures 总被引:1,自引:0,他引:1
Substance P and eledoisin stimulate the accumulation of inositol phosphates in a dose-dependent manner in retinal and superior colliculus slices of the rabbit. The EC50 values for substance P and eledoisin in both tissues were of the same order (1.5-4.9 microM), suggesting that the receptors in the two tissues were alike with characteristics of the SP-P subtype rather than the SP-E subtype. These data suggest that the SP-immunoreactive material in the retinal ganglion and amacrine cells is identical. The effectiveness for a number of tachykinin substances at 10(-5) M for stimulating inositol phosphates accumulation was as follows: Substance P greater than eledoisin greater than neurokinin A greater than neurokinin B greater than substance P (octapeptide) greater than substance P (pentapeptide). Spantide [(D-Arg1, D-Try7.9, Leu11) substance P] and (D-Pro2, D-Try7.9) substance P did not stimulate inositol phospholipid hydrolysis. However, spantide, at a concentration of 10(-6) M, was an antagonist of the effect produced by substance P, but had no action on the effect produced by neurokinin A or neurokinin B. Substance P and other tachykinins were also effective in stimulating inositol phosphates accumulation in 3-5-day-old rabbit retinal cultures but did not elicit a response in the older (25-30-day-old) cultures which lacked neurones but contained Müller cells. Furthermore, substance P was only active in the younger cultures in stimulating an increase in internal calcium levels. It is therefore concluded that retinal tachykinin receptors linked to phosphoinositide turnover and calcium mobilisation are associated exclusively with neurones and not with Müller cells. 相似文献
6.
7.
Multiple genes encode nuclear factor 1-like proteins that bind to the promoter for 3-hydroxy-3-methylglutaryl-coenzyme A reductase. 总被引:37,自引:1,他引:36 下载免费PDF全文
8.
9.
N1303K is one of the most frequent non-delta F508 mutations causing cystic fibrosis in Central Europe. Since no restriction site is altered by this mutation and no other frequent mutations are known so far in exon 21, the detection requires a separate and laborious test. A mismatched primer was used to create an artificial Hin dIII site in amplified wildtype DNA, which is destroyed by the mutation. This allows for rapid and convenient detection by restriction enzyme digestion. 相似文献
10.
Declan Donovan BSc Dr. Judith H. Harmey PhD Deirdre Toomey BSc D. Henry Osborne MCh H. Paul Redmond MCh David J. Bouchier-Hayes MCh 《Annals of surgical oncology》1997,4(8):621-627
Background: Angiogenesis is essential for tumor growth and metastasis. Vascular endothelial growth factor (VEGF) is the most potent angiogenic
factor identified to date. TGFβ-1 acts as an indirect angiogenic agent.
Methods: VEGF and TGFβ-1 were measured in the serum of breast cancer patients and agematched controls and in tumor tissue of cancer
patients by ELISA. VEGF protein and mRNA expression by breast tumor cell lines were examined, and the effect of TGFβ-1 on
VEGF production in these cells was assessed.
Results: VEGF levels were significantly higher (P=.03) in the serum of patients with breast cancer compared to age-matched controls. A positive correlation was found between
serum (r=0.539) and tumor tissue (r=0.688) levels of VEGF and TGFβ-1. Metastatic MDA-MB-231 breast cancer cells produce more
VEGF than do the primary BT474 cells. TGFβ-1 significantly (P<.05) increased production of VEGF.
Conclusions: Breast cancer cells constitutively produce VEGF protein and mRNA. There is a relationship between VEGF and TGFβ-1 levels
in breast cancer patients, and TGFβ-1 regulates VEGF expression by breast cancer cells.
Presented at the 50th Annual Cancer Symposium of the Society of Surgical Oncology, Chicago, Illinois, March 20–23, 1997. 相似文献