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   20670篇
  免费   1739篇
  国内免费   61篇
  22470篇
  2022年   152篇
  2021年   239篇
  2020年   141篇
  2019年   199篇
  2018年   242篇
  2017年   200篇
  2016年   339篇
  2015年   624篇
  2014年   674篇
  2013年   1035篇
  2012年   1134篇
  2011年   1170篇
  2010年   717篇
  2009年   682篇
  2008年   1068篇
  2007年   1106篇
  2006年   1014篇
  2005年   1016篇
  2004年   949篇
  2003年   935篇
  2002年   908篇
  2001年   224篇
  2000年   183篇
  1999年   262篇
  1998年   265篇
  1997年   194篇
  1996年   208篇
  1995年   182篇
  1994年   198篇
  1993年   166篇
  1992年   179篇
  1991年   168篇
  1990年   145篇
  1989年   156篇
  1988年   172篇
  1987年   158篇
  1986年   147篇
  1985年   183篇
  1984年   199篇
  1983年   189篇
  1982年   205篇
  1981年   239篇
  1980年   207篇
  1979年   163篇
  1978年   191篇
  1977年   169篇
  1976年   141篇
  1975年   146篇
  1974年   164篇
  1973年   161篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Johnson  George  Bachman  Ronald  Roed  Terry  Riddervold  Peggy 《Human genetics》1977,35(3):353-356
Summary A girl with partial trisomy for the short arm of chromosome 10(p12pter) due to mal chromosome segregation in the father 46,XY,t(7;10)(p22;p12) is described. The major abnormalities in this case are: mottled skin, mid-facial hypoplasia, low percentiles for weight, length, and head circumference, and club feet.To whom offprint requests should be sent  相似文献   
102.
103.
Summary Total lipids were extracted from 161 redpolls (Acanthis spp.) collected each month of the year from October 1962 to September 1963, in interior Alaska. A lipid index (Weight of ether extract x100/live body weight) was calculated for each sample. Lipids were also extracted from sections of pectoral muscle, livers and hearts representing each month.Body weight and lipid index were significantly positively correlated being highest in January and lowest in September. Total lipid content was significantly inversely correlated with air temperature; the high autumn and spring pre-migratory lipid peaks of migratory species were only weakly expressed in the redpolls. Liver lipid showed a significant annual variation being highest in December and lowest in August, while lipid from heart and pectoral muscle did not vary seasonally.Five birds were held in captivity during spring and summer at a constant temperature of 22°C. Food consumption was 5.1 g/day or 22.4 kcal. The caloric value of the most extensively utilized natural food, birch seed (Betula papyrifera), was determined (5.4–5.5 kcal/g dry wt). When esophageal diverticulae are full (2.0 g wet wt) of birch seeds, the resulting energy yield may sustain an individual for only a fraction of a 24 h winter day in contrast to other arctic herbivores (e.g. ptarmigan, Lagopus sp.) in which a full crop may suffice for the full 24 h period.  相似文献   
104.
Dye sensitized photo-oxidation inactivates tyrosinases isolated from Neurospora and Agaricus. The rate of inactivation is enhanced by cyanide and is dependent on pH.  相似文献   
105.
106.
Therapy with anticonvulsant drugs reduces the frequency and severity of seizures in many but not all epileptic patients. Unfortunately, in a significant number control remains poor even when maximal doses of multiple anticonvulsant drugs are given. Some of these patients are candidates for surgical treatment of epilepsy. The operative management of convulsive disorders is a well-established technique and is available in some centers. In selected cases, such operations are both safe and effective, with good longterm improvement or complete control in 76 percent of patients. We have summarized the 24-year experience with surgical operation for epilepsy at the University of Washington Medical Center.  相似文献   
107.
Injections of arginine vasotocin into bullfrogs had no effect on plasma glucose after 30 min. but caused hyperplycemia after 120 min. Plasma levels of growth hormone were elevated earlier (30 min.) and returned to control levels after 120 min. Plasma free fatty acids were unaltered following vasotocin administration. It is suggested that the hyperglycemic effect of vasotocin may be mediated via growth hormone.  相似文献   
108.
The nematode Drilomermis leioderma n. gen., n. sp. (Merrnithidae) is described from larvae of Cybister fimbriolatus (Say) (Dytiscidae: Coleoptera) in Louisiana. Diagnostic characters of the genus Drilomermis are: medium-sized nematodes with the cuticle appearing smooth (lacking cross fibers) under the light microscope, six cephalic papillae, without mouth papillae, six hypodermal cords at midbody, 2 extremely long spicules (longer than 10 times body width at anus) which are separate and parallel (not twisted), an S-shaped vagina, medium-sized amphids located near head papillae, and postparasitic juvenile with a tail appendage. D. leioderma possesses a ventrally displaced mouth, very long vagina, and male genital papillae arranged in 3 double rows in the vicinity of the cloacal opening. Even when containing multiple parasites, about 40% of the hosts sulwived emergence of the memithids and lived several more days. In nature, some of these hosts may be able to continue their development, which is unusual since most mermithid-parasitized hosts die soon after the nematode emerges.  相似文献   
109.
Strains of a new flavivirus, for which the name Saumarez Reef Virus is proposed, were isolated from seabird ticks collected from four localities. Two strains were isolated from ticks of the species Ornithodoros capensis Neumann 1901 collected from the nests of Sooty Terns, Sterna fuscata Linnaeus 1766 on coral cays off the east coast of Queensland, Australia. The other three strains were isolated from ticks of the species Ixodes eudyptidis Maskell 1885 taken from two dead Silver Gulls Larus novaehollandiae Stephens 1826 in northern Tasmania. The new virus was compared serologically with 50 other flaviviruses at the Yale Arbovirus Research Unit and was found to be most closely related to Tyuleniy virus.  相似文献   
110.
C57BL/6J-bgJbgbg mice are reported to be less susceptible to tumor induction by threshold doses of Moloney murine sarcoma virus than their +/bg littermates, and there are no significant differences between bgbg and +/bg mice in which tumors were induced with respect to tumor latency, size, and regression rate. The difference in tumor frequency cannot be accounted for by M-MSV boosting of activity in bgbg mice or by depression of activity in +/bg animals.  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