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   24006篇
  免费   2219篇
  国内免费   57篇
  2022年   165篇
  2021年   284篇
  2020年   166篇
  2019年   234篇
  2018年   275篇
  2017年   246篇
  2016年   390篇
  2015年   738篇
  2014年   788篇
  2013年   1185篇
  2012年   1315篇
  2011年   1327篇
  2010年   833篇
  2009年   791篇
  2008年   1209篇
  2007年   1214篇
  2006年   1127篇
  2005年   1137篇
  2004年   1067篇
  2003年   1031篇
  2002年   1016篇
  2001年   327篇
  2000年   287篇
  1999年   345篇
  1998年   314篇
  1997年   235篇
  1996年   249篇
  1995年   223篇
  1994年   236篇
  1993年   214篇
  1992年   255篇
  1991年   243篇
  1990年   212篇
  1989年   228篇
  1988年   246篇
  1987年   229篇
  1986年   193篇
  1985年   243篇
  1984年   266篇
  1983年   229篇
  1982年   242篇
  1981年   274篇
  1980年   242篇
  1979年   212篇
  1978年   223篇
  1977年   208篇
  1976年   186篇
  1975年   188篇
  1974年   201篇
  1973年   192篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Utilizing horseradish peroxidase as a tracer protein, it is shown that trichogen and tormogen cells have a secretory function. Protein tracer from the haemolymph enters these cells by endocytosis and is transported to the sensillum liquor cavity by transport vacuoles and multivesicular bodies. It is also suggested that closely associated pigment cells may be involved in macromolecular transport.  相似文献   
34.
George Gibson 《CMAJ》1931,24(1):143-144
  相似文献   
35.
36.
37.
Activation of the sympathetic system by phencyclidine (PCP) should result in catecholamine release from the adrenals. However, adrenalectomy does not reduce PCP-induced hypertension. In an attempt to rectify this inconsistency, the direct effects of PCP on the bovine adrenal medulla were examined. At (3×10?6M), PCP reduced the acetylcholine-(ACh)-induced catecholamine release by 50%. Surprisingly, barium-induced secretion of catecholamines was also reduced by PCP. ACh-induced catecholamine release was not altered by 10?3M 4-aminopyridine (4 AP), the potassium channel blocker. Thus, calcium antagonist actions of PCP and consequent block of catecholamine secretion from adrenal medulla may explain the lack of effect of adrenalectomy on PCP-induced hypertension. Possible contributions of calcium and/or potassium channel blockade to other manifestations of PCP overdosage are discussed.  相似文献   
38.
George Gibson 《CMAJ》1931,25(2):225-227
  相似文献   
39.
This study examined whether group progressive relaxation training was as effective as individual EMG biofeedback training in facilitating the academic achievement and self-control of 45 hyperactive elementary school children. Academic achievement was assessed with the Gates-MacGinities Reading Tests, and self-control was measured with the Nowicki-Strickland and the Teacher Rating scales. Eight sessions were scheduled at weekly intervals. Progressive relaxation was conducted in groups of seven or eight and was induced with a commercial audiocassette program. EMG training augmented frontalis biofeedback with those taped exercises. A placebo group listened to taped children's stories. Multivariate analysis of variance indicated no significant differences among the three contrast groups when all dependent variables were considered together. However, univariate F values and discriminant analysis disclosed locus of control to be significantly more internal for the progressive relaxation condition. Also, differences between the two relaxation and the placebo groups, though not statistically significant, were all in the expected direction. While the relative efficacy of group progressive relaxation could not be established conclusively, the data appeared sufficiently positive to warrant further investigation of this cost-effective prospective intervention.The opinions expressed by the authors are not necessarily those of their respective institutions.  相似文献   
40.
1. The properties of rhodopsin in solution have been examined in preparations from marine fishes, frogs, and mammals. 2. The bleaching of neutral rhodopsin in solution includes a photic and at least three thermal ("dark") processes. Thermal reactions account for approximately half the total fall in extinction at 500 mµ. 3. Bleaching has been investigated at various pH''s from 3.9 to about 11. With increase in pH the velocity of the thermal components increases rapidly. Though the spectrum of rhodopsin itself is scarcely affected by change in pH, the spectra of all product-mixtures following irradiation are highly pH-labile. 4. The spectrum of pure rhodopsin—or of the rhodopsin chromophore—is fixed within narrow limits. The extinction at 400 mµ lies between 0.20 to 0.32 of that at the maximum. 5. Within the limitations of available data, the spectrum of pure rhodopsin corresponds in form and position with the spectral sensitivity of human rod vision, computed at the retinal surface. 6. The nature of bleaching of rhodopsin in solution, its kinetics, and its significance in the retinal cycle are discussed.  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