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   150880篇
  免费   7167篇
  国内免费   194篇
  2021年   1121篇
  2020年   849篇
  2019年   951篇
  2018年   2446篇
  2017年   2468篇
  2016年   4626篇
  2015年   8413篇
  2014年   8249篇
  2013年   8999篇
  2012年   9067篇
  2011年   6491篇
  2010年   4722篇
  2009年   4085篇
  2008年   4139篇
  2007年   4090篇
  2006年   3961篇
  2005年   9486篇
  2004年   8117篇
  2003年   6161篇
  2002年   3688篇
  2001年   2814篇
  2000年   2202篇
  1999年   2850篇
  1998年   944篇
  1992年   2687篇
  1991年   2754篇
  1990年   2770篇
  1989年   2655篇
  1988年   2581篇
  1987年   2376篇
  1986年   2164篇
  1985年   2183篇
  1984年   1582篇
  1983年   1288篇
  1982年   856篇
  1981年   807篇
  1979年   1565篇
  1978年   1125篇
  1977年   917篇
  1976年   900篇
  1975年   1246篇
  1974年   1333篇
  1973年   1327篇
  1972年   1310篇
  1971年   1234篇
  1970年   1072篇
  1969年   1106篇
  1968年   1030篇
  1967年   981篇
  1966年   770篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
61.
ESR spectra of gamma-irradiated and frozen at 77 K human oxyhemoglobin and partially denaturated methemoglobin solutions were analysed. The quartet signal ascribed to the anion-radical of proximal histidine was shown to dominate in the spectra of both solutions. The spectra of methemoglobin solution irradiated with relatively small doses have an intensive singlet ascribed to the stabilized electron. The formation mechanism of free radicals is discussed.  相似文献   
62.
The cause for infertility which affects about 10–15% of all couples may be found in approximately half of the cases in the male partners who usually exhibit reduced sperm counts in the ejaculate (i.e. oligozoospermia or azoospermia). The clinically most relevant genetic causes of spermatogenic failure are chromosomal aberrations including Klinefelter’s syndrome and Y chromosomal microdeletions of the AZF loci. Aside from the full clinical picture of cystic fibrosis, mutations in the CFTR gene can cause an isolated obstructive azoospermia without spermatogenic impairment. Genetic investigations should depend on the results of andrological examinations. Chromosomal aberrations are detected more frequently with decreasing sperm counts, where autosomes (e.g. translocations) are predominantly involved in men with oligozoospermia whereas in 10–15% azoospermia is caused by Klinefelter’s syndrome. Classical AZF deletions are found only in men with severe oligospermia or azoospermia and have a prognostic value. In contrast to men with AZFc deletions, carriers of complete AZFa and AZFb deletions have virtually no chance for testicular sperm extraction and a testicular biopsy is not advised. Rare cases of male infertility may be caused by specific syndromes or sperm defects (e.g. globozoospermia and disorders of ciliary structure).  相似文献   
63.
Interaction between cytotoxin of the Central Asia cobra venom and dimiristoylphosphatidylcholine bilayer depending on its phase state was studied by ESR with spin label. A conclusion can be drawn that the efficiency of cytotoxin effect on the membranes depends on their phase state. Cytotoxin molecules are incorporated into myophile region of the bilayer, only if the latter is in the liquid crystal state. The interaction between cytotoxins and lipids of the bilayer in a gel state is in the main conditioned by electrostatic forces.  相似文献   
64.
65.
We used self‐reported data from United Methodist clergy to assess the prevalence of obesity and having ever been told certain chronic disease diagnoses. Of all actively serving United Methodist clergy in North Carolina (NC) 95% (n = 1726) completed self‐report height and weight items and diagnosis questions from the Behavioral Risk Factor Surveillance Survey (BRFSS). We calculated BMI categories and diagnosis prevalence rates for the clergy and compared them to the NC population using BRFSS data. The obesity rate among clergy aged 35–64 years was 39.7%, 10.3% (95% CI = 8.5%, 12.1%) higher than their NC counterparts. Clergy also reported significantly higher rates of having ever been given diagnoses of diabetes, arthritis, high blood pressure, angina, and asthma compared to their NC peers. Health interventions that address obesity and chronic disease among clergy are urgently needed.  相似文献   
66.
67.
68.
69.
70.
Indomethacin and substance BW-755C in experiments on isolated myometrium striae of pregnant white rats exert an inhibiting effect on the contractile uterus function due to inhibition of cyclooxygenase or lipoxygenase ways of the arachidonic acid transformation. Prostaglandin F2 alpha is sensitive to functioning of the cyclooxygenase and lipoxygenase ways of the arachidonic acid transformation, while oxytocin--only lipoxygenase one. Conclusions rest on results from multiparametric analysis of the contractile uterus function suggested by authors and confirmed by the pattern recognition method--the Karunen-Loev orthogonal decomposition.  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