全文获取类型
收费全文 | 2246篇 |
免费 | 144篇 |
专业分类
2390篇 |
出版年
2023年 | 11篇 |
2022年 | 18篇 |
2021年 | 24篇 |
2020年 | 25篇 |
2019年 | 30篇 |
2018年 | 33篇 |
2017年 | 35篇 |
2016年 | 43篇 |
2015年 | 78篇 |
2014年 | 99篇 |
2013年 | 126篇 |
2012年 | 145篇 |
2011年 | 144篇 |
2010年 | 95篇 |
2009年 | 83篇 |
2008年 | 124篇 |
2007年 | 112篇 |
2006年 | 108篇 |
2005年 | 113篇 |
2004年 | 120篇 |
2003年 | 123篇 |
2002年 | 98篇 |
2001年 | 44篇 |
2000年 | 31篇 |
1999年 | 48篇 |
1998年 | 35篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 34篇 |
1991年 | 27篇 |
1990年 | 14篇 |
1989年 | 20篇 |
1988年 | 10篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1979年 | 19篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1972年 | 9篇 |
排序方式: 共有2390条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
A N Mats E V Cheprasova S I Elkina E V Koriakin 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1987,(5):67-71
Nonspecific adhesiveness of lymphocytes to polyacrylonitrile fiber and the antigen-specific adhesiveness of T-lymphocytes to Shigella flexneri pellicular immunosorbent have been studied in dysentery patients. Short courses of treatment with indomethacin, but not with thymalin (the preparation of thymic hormones), used for immunomodulation, have accelerated the normalization of nonspecific lymphocyte adhesiveness during regression of the disease, while indomethacin, in contrast to thymalin, inhibits antigen-specific T-lymphocyte adhesiveness which increases with the development of immune response. 相似文献
6.
7.
8.
9.
The 76 kD cell-adhesion factor from crayfish haemocytes promotes encapsulation in vitro 总被引:2,自引:0,他引:2
Summary Semigranular cells from the crayfish, Pacifastacus leniusculus, were separated by Percoll gradient centrifugation and were used to study the encapsulation of foreign particles. The semigranular cells were found strongly to encapsulate glass beads coated with haemocyte lysate in which the prophenoloxidase-activating system had been activated with laminarin or with a low concentration of calcium ions. The granular cells only weakly encapsulated these particles. The encapsulationpromoting factor was purified from haemocyte lysates and found to be a 76 kD protein which was recognized by an antiserum to the previously described 76 kD cell-adhesion factor. After the last step in purification (Con A-Sepharose chromatography), the flowthrough consisted of several proteins, which had some, but less, encapsulation-promoting activity and contained a 30 kD band that was also recognized by the antiserum to the 76 kD cell-adhesion factor. If the haemocyte lysate prepared in low [Ca2+] was incubated with a -1,3-glucan prior to purification, no 76 kD protein could be isolated but only a 30 kD protein. The 30 kD protein thus seems to be a degradation product of the 76 kD cell-adhesion factor. We conclude that the 76 kD protein which is released from degranulating haemocytes, and to a lesser extent its 30 kD fragment, can promote encapsulation. Phenoloxidase did not have any encapsulation-promoting activity. 相似文献
10.
Mats H. Holmqvist Mandyam V. Srinivasan 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(4):451-459
Summary Flies (Musca domestica) avoid danger by initiating a rapid jump followed by flight. To identify the visual cues that trigger the escape response in the housefly, we measured the timing and probability of escapes when the fly was presented with a variety of visual stimuli created by moving targets toward it. Our results show that an escape response is triggered by an approaching dark disk, but not by a receding dark disk. On the other hand, a bright disk elicits escape only when it recedes. A disk with black and white rings is less effective at eliciting escape than is a dark solid disk of the same size. This indicates that the darkening contrast produced by an approaching stimulus is a more crucial parameter than expansion cues contained in the optical flow. Escape is also triggered by a horizontally moving dark edge, but not by a moving bright edge or by a grating. An examination of several visual parameters reveals that the darkening contrast, measured from the onset of stimulation to the start of escape is nearly constant for a variety of stimuli that trigger escape reliably. Thus darkening contrast, coupled with motion may be crucial in eliciting the visually evoked escape response. Other visual parameters such as time-to-contact or target angular velocity seem to be relatively unimportant to the timing of escapes.Abbreviations
P
s
Probability of successful escape
-
r
disk
radius of disk target
-
r
arena
radius of shielding arena
-
v
disk
linear velocity of disk target
-
v
edge
linear velocity of edge
-
d
disk
angular velocity of disk target boundary
-
edge
angular velocity of edge
-
escape
target distance at escape
-
d
start
target distance before onset of target movement
-
h
edge
height of the edge above fly
-
x
start
distance from corner of triangle to start position of edge (0 or 50 mm)
-
x
escape
distance from corner of triangle to the position of the edge when the fly escapes
-
x
center
distance from corner of triangle to point above the center of the pad
-
x
total
distance from the corner of the triangle to the base (height of triangle = base of triangle) 相似文献