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   3433篇
  免费   148篇
  国内免费   28篇
耳鼻咽喉   10篇
儿科学   52篇
妇产科学   48篇
基础医学   338篇
口腔科学   89篇
临床医学   183篇
内科学   1229篇
皮肤病学   20篇
神经病学   195篇
特种医学   230篇
外科学   495篇
综合类   13篇
预防医学   59篇
眼科学   19篇
药学   178篇
中国医学   2篇
肿瘤学   449篇
  2023年   32篇
  2022年   52篇
  2021年   87篇
  2020年   43篇
  2019年   54篇
  2018年   70篇
  2017年   59篇
  2016年   58篇
  2015年   72篇
  2014年   113篇
  2013年   121篇
  2012年   237篇
  2011年   206篇
  2010年   110篇
  2009年   103篇
  2008年   162篇
  2007年   185篇
  2006年   180篇
  2005年   186篇
  2004年   180篇
  2003年   121篇
  2002年   142篇
  2001年   66篇
  2000年   65篇
  1999年   82篇
  1998年   58篇
  1997年   37篇
  1996年   39篇
  1995年   37篇
  1994年   39篇
  1993年   41篇
  1992年   81篇
  1991年   51篇
  1990年   56篇
  1989年   47篇
  1988年   41篇
  1987年   42篇
  1986年   34篇
  1985年   33篇
  1984年   25篇
  1983年   23篇
  1982年   14篇
  1981年   17篇
  1980年   12篇
  1979年   11篇
  1978年   11篇
  1977年   9篇
  1976年   7篇
  1974年   10篇
  1973年   9篇
排序方式: 共有3609条查询结果,搜索用时 15 毫秒
91.
This study examined the effect of synthetic porcine neuropeptide Y on the splanchnic blood flows and the exocrine pancreatic secretion in dogs. Graded doses of neuropeptide Y (0.1–5 g/kg, intravenous) caused dose-dependent reduction of the secretin-stimulated exocrine pancreatic secretion and of the blood flows in the superior mesenteric artery, the portal vein, and the pancreatic tissue. Neuropeptide Y at 5 g/kg reduced the blood flows to 45.9±13.3% (superior mesenteric artery), 63.0±10.5% (portal vein), and 77.9±4.8% (pancreatic tissue), respectively. This dose also reduced secretin-stimulated pancreatic juice volume and CCK-8 plus secretin-stimulated protein output to 65.2±9.3 and 63.3±14.0%, respectively. This study shows a potent vasoconstrictor effect of neuropeptide Y on splanchnic vessels. Neuropeptide Y also inhibited exocrine pancreatic secretion in a significant correlation with the reduction in pancreatic tissue blood flow, which suggests that reduction in the blood flow may be one of the possible mechanisms of the inhibitory action of neuropeptide Y on exocrine secretion.This work was supported by a grant from the Ministry of Education, Japan (A-61440060).  相似文献   
92.
BACKGROUND: Past studies have measured and described the length of life with disability before death, but there has been no study of the relationship between modifiable lifestyle factors and duration of disability. OBJECTIVE: To examine whether there are modifiable factors influencing the length of life with disability before death. METHODS: The study was designed as a retrospective observation of the deceased who had earlier been enrolled in a prospective cohort study.During the follow-up period (1996-1999), we documented 781 deaths among those who were 70-79 years of age at the baseline survey in 1994 (n=10,216). In 2000, we interviewed family members of the deceased about the duration of the subjects' disability before death (n=655). RESULTS: The median duration of disability before death was approximately 6 months. Both higher Body Mass Index (BMI) and shorter time spent walking were significantly associated with an increased risk of long-term disability (more than 6 months). The odds ratios of long-term disability were 1.3 in those with BMI 20-25 and 2.1 in those with BMI>25, compared with BMI<20. The odds ratios of long-term disability were 1.3 in those walking for 0.5-0.9 h/day and 1.7 in those walking for <0.5 h/day, compared with those walking for >1.0 h/day. These relationships were unchanged after stratification for causes of death. CONCLUSION: Weight control and walking in later life may shorten the length of life with disability before death.  相似文献   
93.
We report a case of severe hemolysis after distal splenorenal shunt. Hemolysis was suddenly recognized at the time splenorenal venous anastomosis was completed, and it continued on the operative day and the first postoperative day. After the shunt, the intraoperative splenic venous blood flow was approximately double its previous level, as measured by electromagnetic flowmeter. Angiographic partial splenic embolization was performed on the second postoperative day, and then hemolysis stopped suddenly. This suggested that hemolysis after distal splenorenal shunt was related to increased splenic blood flow and acceleration of erythrocyte destruction.  相似文献   
94.
95.
96.
97.
Formation of precise and high-resolution silica micropatterns on polymer substrates is of importance in surface structuring for flexible device fabrication of optics, microelectronic, and biotechnology. To achieve that, substrates modified with affinity-patterns serve as a strategy for site-selective deposition. In the present paper, vacuum ultraviolet (VUV) treatment is utilized to achieve spatially-controlled surface functionalization on a cyclo-olefin polymer (COP) substrate. An organosilane, 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS), preferentially deposits on the functionalized regions. Well-defined patterns of TMCTS are formed with a minimum feature of ∼500 nm. The secondary VUV/(O)-treatment converts TMCTS into SiOx, meanwhile etches the bare COP surface, forming patterned SiOx/COP microstructures with an average height of ∼150 nm. The resulting SiOx patterns retain a good copy of TMCTS patterns, which are also consistent with the patterns of photomask used in polymer affinity-patterning. The high quality SiOx patterns are of interests in microdevice fabrication, and the hydrophilicity contrast and adjustable heights reveal their potential application as a “stamp” for microcontact printing (μCP) techniques.

Patterned surface treatment on a polymer substrate is carried out by 172 nm VUV through a photomask. TMCTS pattern formation is guided by the resulting affinity-pattern. The secondary VUV treatment converted TMCTS patterns into silica patterns.  相似文献   
98.
Al foam has been used in a wide range of applications owing to its light weight, high energy absorption and high sound insulation. One of the promising processes for fabricating Al foam involves the use of a foamable precursor. In this study, ADC12 Al foams with porosities of 67%–78% were fabricated from Al alloy die castings without using a blowing agent by the friction stir processing route. The pore structure and tensile properties of the ADC12 foams were investigated and compared with those of commercially available ALPORAS. From X-ray computed tomography (X-ray CT) observations of the pore structure of ADC12 foams, it was found that they have smaller pores with a narrower distribution than those in ALPORAS. Tensile tests on the ADC12 foams indicated that as their porosity increased, the tensile strength and tensile strain decreased, with strong relation between the porosity, tensile strength, and tensile strain. ADC12 foams exhibited brittle fracture, whereas ALPORAS exhibited ductile fracture, which is due to the nature of the Al alloy used as the base material of the foams. By image-based finite element (FE) analysis using X-ray CT images corresponding to the tensile tests on ADC12 foams, it was shown that the fracture path of ADC12 foams observed in tensile tests and the regions of high stress obtained from FE analysis correspond to each other. Therefore, it is considered that the fracture behavior of ADC12 foams in relation to their pore structure distribution can be investigated by image-based FE analysis.  相似文献   
99.
100.
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