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   20783篇
  免费   1910篇
  国内免费   23篇
  22716篇
  2022年   141篇
  2021年   265篇
  2020年   141篇
  2019年   213篇
  2018年   271篇
  2017年   210篇
  2016年   397篇
  2015年   692篇
  2014年   771篇
  2013年   960篇
  2012年   1254篇
  2011年   1301篇
  2010年   787篇
  2009年   686篇
  2008年   997篇
  2007年   1107篇
  2006年   1020篇
  2005年   1008篇
  2004年   992篇
  2003年   972篇
  2002年   940篇
  2001年   235篇
  2000年   179篇
  1999年   229篇
  1998年   282篇
  1997年   207篇
  1996年   180篇
  1995年   216篇
  1994年   194篇
  1993年   181篇
  1992年   186篇
  1991年   164篇
  1990年   156篇
  1989年   143篇
  1988年   151篇
  1987年   157篇
  1986年   145篇
  1985年   170篇
  1984年   192篇
  1983年   164篇
  1982年   227篇
  1981年   238篇
  1980年   228篇
  1979年   153篇
  1978年   155篇
  1977年   148篇
  1976年   173篇
  1975年   133篇
  1974年   150篇
  1973年   166篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
During two years of passage, several myxamoebal strains of Physarum polycephalum changed with regard to their properties in crosses and plaque morphology. These changes have been correlated with increased nuclear deoxyribonucleic acid content.  相似文献   
72.
73.
Very high dielectric constants have been observed for bacteria at low frequencies. High dielectric constants such as these can be explained by a theory which has been developed for the low-frequency dielectric dispersion of porous charged particles and which has been tested successfully through measurements with ion exchange resins. The bacterial cell wall is electrically similar to an ion exchange resin. Observations show that the theory provides a quantitative explanation for the low-frequency dielectric dispersion of bacteria.  相似文献   
74.
A simple and safe procedure has been described for the preparation of short-chain aliphatic hydroxamic acids in quantities as large as 1 mole and as small as 0.01 mole. The procedure is equally suitable for the preparation of isotopically labeled hydroxamates, as has been demonstrated in the case of 1-14C-acetohydroxamic acid and 3H-acetohydroxamic acid. Some physical and chemical characteristics, including infrared spectra of formo-, aceto-, propiono-, and isobutyro-hydroxamic acids prepared by this method have been described.  相似文献   
75.
When head and blunt abdominal injuries are combined, the head injury is often afforded too much attention and the abdominal injury too little, especially when the patient is unconscious. If mismanaged, the abdominal injury is often the more serious threat to life. Except for extradural hemorrhage, neurosurgical intervention, when indicated, can be delayed until the patient has been thoroughly evaluated for the presence of extra cranial injuries with higher therapeutic priority.Abdominal examination of the unconscious or uncooperative patient is difficult. Tenderness as a sign of abdominal injury cannot be elicited. Abdominal rigidity (in the absence of rigid extremities), a silent abdomen, shock, and extreme restlessness may indicate intra-abdominal changes. Abdominal paracentesis is a valuable diagnostic aid, and the finding of blood, bile-stained fluid, intestinal contents or air is an indication for immediate laparotomy. Once all injuries are known, priorities for treatment can be assigned. Often head and abdominal injuries can be treated concomitantly.  相似文献   
76.
77.
78.
79.
80.
Significant alterations in the structure and functions of the kidney are caused by a number of metabolic disturbances and deficiencies of physiological substances. These include intercapillary glomerulosclerosis, gout, hypercalcemia, hereditary cystinuria, potassium depletion, pyrophosphates deficiency, vitamin D deficiency and liver disorders. Some of these metabolic disorders are secondary to drug ingestion.  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