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   1175篇
  免费   153篇
  2021年   13篇
  2016年   23篇
  2015年   31篇
  2014年   27篇
  2013年   45篇
  2012年   48篇
  2011年   55篇
  2010年   40篇
  2009年   24篇
  2008年   38篇
  2007年   35篇
  2006年   41篇
  2005年   41篇
  2004年   32篇
  2003年   40篇
  2002年   33篇
  2001年   31篇
  2000年   30篇
  1999年   34篇
  1998年   10篇
  1997年   10篇
  1996年   13篇
  1995年   15篇
  1993年   14篇
  1992年   26篇
  1991年   23篇
  1990年   22篇
  1989年   22篇
  1988年   23篇
  1987年   28篇
  1986年   21篇
  1985年   29篇
  1984年   15篇
  1983年   15篇
  1982年   18篇
  1981年   14篇
  1980年   16篇
  1979年   22篇
  1978年   29篇
  1977年   16篇
  1976年   24篇
  1974年   14篇
  1973年   20篇
  1972年   15篇
  1971年   13篇
  1970年   14篇
  1969年   11篇
  1968年   9篇
  1967年   8篇
  1966年   15篇
排序方式: 共有1328条查询结果,搜索用时 15 毫秒
991.
With the cancellation of fenamiphos in the near future, alternative nematode management tactics for plant-parasitic nematodes (PPN) on golf courses need to be identified. The use of entomopathogenic nematodes (EPN) has been suggested as one possible alternative. This paper presents the results of 10 experiments evaluating the efficacy of EPN at managing PPN on turfgrasses and improving turf performance. These experiments were conducted at various locations throughout Florida over the course of a decade. In different experiments, different EPN species were tested against different species of PPN. Separate experiments evaluated multiple rates and applications of EPN, compared different EPN species, and compared single EPN species against multiple species of PPN. In a few trials, EPN were associated with reductions in certain plant-parasite species, but in other trials were associated with increases. In most trials, EPN had no effect on plant parasites. Because EPN were so inconsistent in their results, we conclude that EPN are not acceptable alternatives to fenamiphos by most turf managers in Florida at this time.  相似文献   
992.
The activity of sulfite oxidase increased in intact rat hepatic mitochondria and decreased in solubilized mitochondria during poisoning by CCl4. During acute damage the sulfite oxidase activity of the post-mitochondrial supernate increased, while the total activity in the hepatocyte declined. Thus, the outer membrane loses its selective permeability to macromolecules coincident with the decline of oxidative phosphorylation. In recovery, normal levels of activity in intact mitochondria and in the hepatocyte were restored, but a large proportion of the total activity remained in the cytoplasm. The data suggest that outer membrane repair and replacement of sulfite oxidase are involved in the restoration of mitochondrial structure and function.  相似文献   
993.
Human sperm motility response to three mechanical stimuli, gravity, fluid flow shear and rigid boundaries, was measured in a tube of 310 X 400 microns calibre. Data were gathered by cine recordings at various focussing levels d across the tube and analysed with a computerized image analysis system. The most influential stimulus was the tube wall near (more than 'at') which the swimmers tended to accumulate, leaving the fluid beyond 100 microns from the wall (d = 100) vacant of motile spermatozoa. The boundary effect was evident as soon as the spermatozoa could be viewed after loading, and accumulation, measured as frequency, as a function of d did not change with time t. This response was not significantly altered by the addition of laminar flow with a centre line velocity of about 400 microns/sec. In flow shear, spermatozoa aligned positively (in the flow direction) at the wall but negatively by about 30 microns from the wall where the velocity gradient (= shear rate) was about 3.5 sec-1. The response to gravity was relatively weak with 11 spermatozoa positive (swimming downwards) for each 9 negative. Neither the boundary effect nor the 'rheotaxic' effect were influenced by gravity as there was no statistical difference in orientation or distribution patterns between vertically and horizontally flowing suspensions. It is suggested that the boundary effect cannot be ignored in in-vitro manipulations, particularly when spermatozoa are observed or extracted. Its importance in vivo lies in the degree to which the tubes transporting motile spermatozoa seem to have mechanisms for reversing the wall accumulation tendency.  相似文献   
994.
Sex differences in the behavior of 2.5- to 4.5-year-old rhesus monkeys, living in two social groups approximating natural compositions, were studied over a period of 3 years. Both sexes interacted significantly more often with members of their own sex in agonistic and affiliative interactions even when total rates and durations for male and female subjects did not differ. Strong sexual segregation was also seen in proximity, nonspecific contact, and huddling partners. Males were more involved in play and sex than were females and engaged in these activities primarily with other males. Females did more grooming than males, but groomed both male and female partners. Females also appeared to interact with a wider age range of partners than did males. Although total participation in aggressive interactions did not differ between the two sexes, females used more active forms of agonistic expression than did males. These differences in the behavior of adolescent rhesus are hypothesized to lead to social bonding among adolescent males, while females remain bonded to their matri-lines, including younger males and some fully adult males associated with matrilineal relatives. Adolescent males emigrate from their natal groups but retain sociality and bond to males and females in new groups as they become adult. © 1993 Wiley-Liss, Inc.  相似文献   
995.
996.
A prospective randomized study of the treatment of postpartum endometritis was conducted with 43 patients. The bacterial origin of the infection was determined by uterine aspiration. Treatment was successful in 17 of the 19 patients receiving ampicillin (12 g/d) and in 21 of the 24 patients receiving clindamycin (2.4 g/d) plus gentamicin (5.1 mg/kg daily).  相似文献   
997.
998.
999.
The effect of estradiol-17-beta on lipids of the ventricular myocardium of mice has been studied with a cytochemical technique in which malachite green was added to glutaraldehyde. This malachite green-glutaraldehyde fixative enhances the visualization of certain phospholipid-related elements. Estrogen induces an affinity of ventricular cardiac lipid inclusions for the cationic dye malachite green. The staining affinity is evidenced only in the estrous female, not in diestrus. In oophorectomized animals, malachite green staining is seen only following estradiol injection, but this effect is blocked by progesterone. In the male, ventricular lipids do not stain, nor do they develop malachite green affinity with estrogen stimulation. These results imply a blockade of the estradiol-mediated dye affinity by progesterone and testosterone. This reinforces the concept of the heart as a target organ for sex steroids and expands the previously described estrogen effects on myocardium.  相似文献   
1000.
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