全文获取类型
收费全文 | 389667篇 |
免费 | 22246篇 |
国内免费 | 974篇 |
专业分类
412887篇 |
出版年
2018年 | 15223篇 |
2017年 | 13918篇 |
2016年 | 11844篇 |
2015年 | 5221篇 |
2014年 | 6339篇 |
2013年 | 8949篇 |
2012年 | 14040篇 |
2011年 | 22832篇 |
2010年 | 19024篇 |
2009年 | 14314篇 |
2008年 | 18775篇 |
2007年 | 20519篇 |
2006年 | 9431篇 |
2005年 | 9083篇 |
2004年 | 9649篇 |
2003年 | 9376篇 |
2002年 | 8956篇 |
2001年 | 12928篇 |
2000年 | 12426篇 |
1999年 | 9587篇 |
1998年 | 3020篇 |
1997年 | 2902篇 |
1996年 | 2654篇 |
1995年 | 2419篇 |
1992年 | 7444篇 |
1991年 | 7645篇 |
1990年 | 7595篇 |
1989年 | 7377篇 |
1988年 | 6885篇 |
1987年 | 6496篇 |
1986年 | 5990篇 |
1985年 | 6144篇 |
1984年 | 4928篇 |
1983年 | 4141篇 |
1982年 | 2849篇 |
1981年 | 2506篇 |
1980年 | 2425篇 |
1979年 | 4598篇 |
1978年 | 3572篇 |
1977年 | 3256篇 |
1976年 | 3196篇 |
1975年 | 3840篇 |
1974年 | 4226篇 |
1973年 | 4274篇 |
1972年 | 4012篇 |
1971年 | 3793篇 |
1970年 | 3037篇 |
1969年 | 3007篇 |
1968年 | 2783篇 |
1967年 | 2513篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
M V Sauer 《The Western journal of medicine》1994,161(2):164-165
63.
A L Nevmiatullin O N Vorob'eva A N Maianski? 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(7):67-71
The neutrophil-stimulating properties of 38 S. aureus strains and 32 S. epidermidis strains were studied in the reaction of luminol-mediated chemiluminescence. All S. aureus strains and 29 S. epidermidis strains were found to possess neutrophil-stimulating activity, the mean activity index for S. aureus being significantly higher. The stimulating activity of the strains varied within a wide range (the variation coefficient was 120.0 +/- 21.9%) and did not correlate with the content of protein A in bacterial cells and the degree of their hydrophoby. The opsonization of staphylococci with normal human serum enhanced the neutrophil reaction 1.5- to 100-fold and simultaneously leveled out the chemiluminescence indices in experiments with different strains (the variation coefficient was 8.0 +/- 1.5%). The nature of the neutrophil-stimulating effect of staphylococci and its relationship to the exploratory reactions of phagocytes are discussed. 相似文献
64.
65.
We studied the impulse activity of neurons of the basal and lateral amygdalar nuclei generated when experimental animals (rats) performed fast stereotyped food-procuring movements by the forelimb. Within the basolateral amygdala, there are neurons whose activity is related to different stages of getting off the food, and according to the characteristics of their spiking these neurons should be divided into a number of subpopulations. Activation forestalling the movement initiation by 0.5-1.0 sec was observed in most neurons of the basolateral amygdala; this is considered a manifestation of excitation related to a motivation component of the food-procuring behavior. Activation of amygdalar neurons following movement initiation can result from generation in this structure of additional excitation necessary for successful performance of a complete food-procuring motor cycle. 相似文献
66.
Hugo R. Permingeat Maria V. Romagnoli Juliana I. Sesma Ruben H. Vallejos 《Plant Molecular Biology Reporter》1998,16(1):89-89
An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase. 相似文献
67.
E A Rybnikova V V Rakitskaia V G Shaliapina 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》1999,85(4):594-597
Intrastriatal corticotrophin-releasing hormone (CRH) was shown to induce a decrease in the plasma tectosterone concentration. Besides, the 6-OHDA pre-treatment completely prevented the suppression of plasma testosterone in response to intrastriatal CRH administration. The findings suggest that the striatum is involved in the extrahypothalamic regulation of the gonadal endocrine function. 相似文献
68.
V. G. Borkhvardt 《Russian Journal of Developmental Biology》2000,31(3):154-161
The development of the fin and limb buds involves a balance of centrifugal (active) and centripetal (passive) mechanical forces,
the first of which acts to move the walls of these structures away from each other and the second of which holds them together.
When the volume of the mesodermal core increases, the generated force meets with the resistance of the basal membrane, and
as a result, the limb bud has a tendency to acquire a cylindrical shape. Collagen fibers, individual mesenchymal cells, and
their groups hold together the dorsal and the ventral wall of the limb bud, prevent the movement of these walls away from
each other, and in this way direct bud growth along the proximodistal and the anteroposterior axes. The balance of the forces
which stretch the ectodermal layer and those which constrain it has also been observed in the development of other body parts. 相似文献
69.
A rational attempt to prepare FmocHis(piTrt)OH regiospecifically gave in fact the well-known tau-trityl isomer, and experiments with model systems indicate that the prospects for access to pi-trityl histidine derivatives, which would be of great value for the racemization-free synthesis of histidine-containing peptides, are poor. 相似文献
70.