全文获取类型
收费全文 | 1514篇 |
免费 | 82篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 10篇 |
儿科学 | 27篇 |
妇产科学 | 22篇 |
基础医学 | 189篇 |
口腔科学 | 7篇 |
临床医学 | 103篇 |
内科学 | 313篇 |
皮肤病学 | 26篇 |
神经病学 | 108篇 |
特种医学 | 47篇 |
外科学 | 329篇 |
综合类 | 5篇 |
一般理论 | 1篇 |
预防医学 | 55篇 |
眼科学 | 185篇 |
药学 | 113篇 |
肿瘤学 | 60篇 |
出版年
2021年 | 36篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 31篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 43篇 |
2013年 | 35篇 |
2012年 | 78篇 |
2011年 | 77篇 |
2010年 | 39篇 |
2009年 | 23篇 |
2008年 | 50篇 |
2007年 | 66篇 |
2006年 | 74篇 |
2005年 | 70篇 |
2004年 | 57篇 |
2003年 | 56篇 |
2002年 | 40篇 |
2001年 | 59篇 |
2000年 | 66篇 |
1999年 | 38篇 |
1998年 | 18篇 |
1997年 | 23篇 |
1996年 | 10篇 |
1995年 | 15篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 41篇 |
1991年 | 45篇 |
1990年 | 33篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 30篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 15篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 25篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1976年 | 16篇 |
1975年 | 9篇 |
1974年 | 19篇 |
1973年 | 12篇 |
1972年 | 10篇 |
1969年 | 10篇 |
排序方式: 共有1600条查询结果,搜索用时 15 毫秒
31.
Effect of polyamine deprivation on the survival of intracranial glioblastoma bearing rats 总被引:2,自引:0,他引:2
It has previously been shown that systematic polyamine deprivation results in the almost complete inhibition of the growth of several solid tumors. The same polyamine deficient diet (containing antibiotics for the decontamination of the gastrointestinal tract, the ornithine decarboxylase inhibitor 2-(difluoromethyl)ornithine, and the polyamine oxidase inhibitor N1, N4-bis-(2,3-butadienyl)putrescine; "drug-containing polyamine deficient chow", DC-PDC) was applied for the first time to the treatment of rats with an intracranial tumor. Rats received intracortical grafts of C6 rat glioblastoma cells, and the length of their survival was determined. Treatment with DC-PDC, starting four days after tumor cell inoculation, significantly prolonged the median survival of the glioblastoma-bearing rats. The results underline the general growth inhibitory effect of systematic polyamine deprivation. Since the effect of polyamine restriction on tumor growth is reversible, combinations with cytotoxic drugs have to be found which exploit the changed functions of polyamine deficient tumor cells. 相似文献
32.
Silent cerebral ischemia detected by diffusion-weighted MRI after carotid endarterectomy 总被引:6,自引:0,他引:6
Barth A Remonda L Lövblad KO Schroth G Seiler RW 《Stroke; a journal of cerebral circulation》2000,31(8):1824-1828
BACKGROUND AND PURPOSE: Small emboli arising from a friable plaque during carotid endarterectomy (CEA) constitute an important risk of perioperative ischemic complications. To evaluate the incidence and significance of silent cerebral ischemic lesions of embolic origin after CEA, we prospectively examined a series of surgical patients with high-grade carotid stenosis by using diffusion-weighted MRI (DWI). We also tried to correlate postoperative ischemic lesions with the occurrence of sonographic cerebral embolic signals, the presence of plaque ulcerations, and the use of intraoperative shunting. METHODS: Of a consecutive series of 53 patients undergoing elective CEA for high-grade carotid stenosis, 48 patients with unchanged postoperative neurological status were prospectively studied with DWI of the brain the day before and the day after the operation. The magnetic resonance images were analyzed by 2 neuroradiologists blinded to the clinical result of the operation. Any new hyperintense signal was interpreted as a postoperative ischemic lesion. RESULTS: Forty-six (95.8%) of 48 patients had unchanged postoperative brain DWI. In 2 patients (4.2%), a new single asymptomatic hyperintense signal was observed on the side of the operation. Both lesions were small and presumably of embolic origin. They were not related to sonographic embolic signals, plaque ulcerations, or intraoperative shunting. CONCLUSIONS: These results suggest that the incidence of silent ischemic brain lesions of embolic origin after CEA is low and does not correlate with the occurrence of intraoperative sonographic microemboli. They confirm that CEA is a safe procedure that carries a low risk of postoperative cerebral events. 相似文献
33.
Sperm number and condition affect the number of basal cells and their expression of macrophage antigen in the murine epididymis 总被引:1,自引:0,他引:1
Unilateral ligation of the mid-corpus epididymis, the proximal vas deferens and imposition of an abdominal temperature for 6 days as well as bilateral castration for 3, 6 or 14 days, resulted in a change in epithelial composition of the adult murine epididymis with regard to the number and antigen expression of basal cells. There were fewer basal cells per tubule cross-section with fewer expressing F4/80 antigen when spermatozoa were absent from the proximal lumen following short-term castration. Conversely, more basal cells with more of them demonstrating macrophage antigen expression were evident when more or damaged spermatozoa were in the proximal lumen after corpus ligation and exposure to abdominal temperature or in the cauda after long-term withdrawal of androgen support. By contrast, ligation of the vas deferens did not lead to tubule distension, and hence sperm accumulation, and did not alter the basal cell population in the cauda epididymis. The data suggest that epididymal basal cells respond in number and macrophage antigen expression to the presence of sperm autoantigens in the lumen with little dependence on circulating androgens. These changes may represent responses to minimise the interaction of sperm autoantigens with the immune system and the risk of immunological infertility. 相似文献
34.
Journal of Thrombosis and Thrombolysis - Simultaneous appearance of a pacemaker-lead associated thrombus and a left atrial appendage closure device related thrombus in a patient with urothelial... 相似文献
35.
36.
37.
38.
39.
40.
Nicolas Biais Dustin L. Higashi Jasna Bruji? Magdalene So Michael P. Sheetz 《Proceedings of the National Academy of Sciences of the United States of America》2010,107(25):11358-11363
Through evolution, nature has produced exquisite nanometric structures, with features unrealized in the most advanced man-made devices. Type IV pili (Tfp) represent such a structure: 6-nm-wide retractable filamentous appendages found in many bacteria, including human pathogens. Whereas the structure of Neisseria gonorrhoeae Tfp has been defined by conventional structural techniques, it remains difficult to explain the wide spectrum of functions associated with Tfp. Here we uncover a previously undescribed force-induced quaternary structure of the N. gonorrhoeae Tfp. By using a combination of optical and magnetic tweezers, atomic force microscopy, and molecular combing to apply forces on purified Tfp, we demonstrate that Tfp subjected to approximately 100 pN of force will transition into a new conformation. The new structure is roughly 3 times longer and 40% narrower than the original structure. Upon release of the force, the Tfp fiber regains its original form, indicating a reversible transition. Equally important, we show that the force-induced conformation exposes hidden epitopes previously buried in the Tfp fiber. We postulate that this transition provides a means for N. gonorrhoeae to maintain attachment to its host while withstanding intermittent forces encountered in the environment. Our findings demonstrate the need to reassess our understanding of Tfp dynamics and functions. They could also explain the structural diversity of other helical polymers while presenting a unique mechanism for polymer elongation and exemplifying the extreme structural plasticity of biological polymers. 相似文献