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   332730篇
  免费   37168篇
  国内免费   190篇
  370088篇
  2018年   2839篇
  2017年   2700篇
  2016年   3869篇
  2015年   5331篇
  2014年   6234篇
  2013年   8754篇
  2012年   9979篇
  2011年   9956篇
  2010年   6797篇
  2009年   6132篇
  2008年   8849篇
  2007年   9293篇
  2006年   8585篇
  2005年   8276篇
  2004年   8000篇
  2003年   7757篇
  2002年   7764篇
  2001年   18141篇
  2000年   18369篇
  1999年   14098篇
  1998年   4225篇
  1997年   4494篇
  1996年   4299篇
  1995年   4002篇
  1994年   3939篇
  1993年   3779篇
  1992年   11478篇
  1991年   11121篇
  1990年   10675篇
  1989年   10239篇
  1988年   9477篇
  1987年   8838篇
  1986年   8077篇
  1985年   7959篇
  1984年   6389篇
  1983年   5562篇
  1982年   4104篇
  1981年   3592篇
  1980年   3352篇
  1979年   6110篇
  1978年   4568篇
  1977年   4124篇
  1976年   3759篇
  1975年   4329篇
  1974年   4497篇
  1973年   4389篇
  1972年   4090篇
  1971年   3498篇
  1970年   3168篇
  1969年   2968篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
973.
974.
The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium.  相似文献   
975.
Administration of high-dose Antide to ovariectomized monkeys results in rapid, prolonged, and reversible inhibition of gonadotropin secretion. The present study examined whether similar long-term control would be manifested in the menstrual cycle of intact primates. Antide administration at a dose of either 3.0 or 18.0 mg/kg induced rapid suppression of bioassayable LH concentrations, precipitating a concurrent fall in serum progesterone concentrations from 7.9 +/- 3.6 and 5.8 +/- 1.0 ng/ml (mean +/- SEM) on the day of injection to 0.6 +/- 0.2 and 0.5 +/- 0.1 ng/ml by 2 days post-treatment, respectively. This Antide-induced luteolysis was accompanied by the premature onset of menses within 3 days. The next menses following Antide administration was delayed. Ultimately, folliculogenesis culminating in normal follicular-phase estradiol production, ovulation, and subsequent normal luteal-phase progesterone production did occur in all treated monkeys. Menses resumed 54 +/- 9 and 75 +/- 13 days after treatment with 3.0 and 18.0 mg/kg Antide, respectively. No allergic cutaneous or peripheral reactions were seen, even at the highest dose of Antide. Thus, the long duration of action of high-dose Antide reported earlier in ovariectomized monkeys is also demonstrated in intact primates. These findings, along with the apparent absence of histamine-release effects even at high doses, suggest that Antide is a GnRH antagonist deserving clinical evaluation.  相似文献   
976.
977.
978.
979.
980.
Restriction fragment length polymorphisms (RFLPs) were described for the porcine loci for β-glucosidase (GBA) and the β-polypeptide 1 of the Na+, K+-transporting ATPase (ATP1B1). Linkage analyses using a three-generation pedigree provided evidence for the assignment of ATP1B1, GBA and two microsatellite loci (S0001 and S0067) to a previously described linkage group comprising the loci for blood group L (EAL) and an anonymous microsatellite (S0097). The linear order of the six markers was determined with confidence by multipoint analyses and the length of the linkage group was estimated at 88 CM. This linkage group was assigned to pig chromosome 4 on the basis of a previous physical localization of the ATP1B1 gene. In situ hybridization data for S0001 presented in this study were consistent with a localization on chromosome 4 and suggested a regional localization to 4pl2-pl3. The present study reveals conflicting data concerning the genetic localization of the K88 loci controlling the expression of the receptors for the E. coli pilus antigens. One group has reported data suggesting a loose linkage between K88 and EAL, now mapped to chromosome 4, whereas two other groups have found linkage between K88 and the transferrin locus (TF), mapped to chromosome 13 by in situ hybridization.  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