全文获取类型
收费全文 | 61615篇 |
免费 | 5554篇 |
国内免费 | 36篇 |
出版年
2022年 | 613篇 |
2021年 | 1136篇 |
2020年 | 828篇 |
2019年 | 894篇 |
2018年 | 1257篇 |
2017年 | 1075篇 |
2016年 | 1739篇 |
2015年 | 2519篇 |
2014年 | 2482篇 |
2013年 | 3117篇 |
2012年 | 3729篇 |
2011年 | 3430篇 |
2010年 | 2110篇 |
2009年 | 2046篇 |
2008年 | 2570篇 |
2007年 | 2557篇 |
2006年 | 2316篇 |
2005年 | 2633篇 |
2004年 | 2588篇 |
2003年 | 2210篇 |
2002年 | 1808篇 |
2001年 | 1680篇 |
2000年 | 1612篇 |
1999年 | 1451篇 |
1998年 | 669篇 |
1997年 | 643篇 |
1996年 | 691篇 |
1995年 | 563篇 |
1994年 | 574篇 |
1993年 | 549篇 |
1992年 | 1108篇 |
1991年 | 995篇 |
1990年 | 917篇 |
1989年 | 899篇 |
1988年 | 890篇 |
1987年 | 802篇 |
1986年 | 764篇 |
1985年 | 762篇 |
1984年 | 699篇 |
1983年 | 538篇 |
1982年 | 435篇 |
1981年 | 399篇 |
1980年 | 377篇 |
1979年 | 507篇 |
1978年 | 433篇 |
1977年 | 367篇 |
1976年 | 320篇 |
1975年 | 370篇 |
1974年 | 379篇 |
1973年 | 378篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A preliminary electron microscope study of human neuromuscular junction is presented. The biopsy material was taken from the palmarus longus, and fixed routinely in osmium tetroxide and embedded in methacrylate. The structure of the motor endings and the relationship of the synaptic vesicles to the axolemmal membrane are described. The synaptic clefts are filled with an homogeneous material in continuity with the basement membrane covering the muscle fiber. The subneural apparatus is described, and special attention is paid to a vesicular component present in the sarcoplasm of the junctional area, which differs from synaptic vesicles and is presumed to be a derivate of the sarcoplasmic reticulum. 相似文献
992.
Prof. Dr. A. Mäde 《International journal of biometeorology》1959,3(1):311-319
Ohne Zusammenfassung 相似文献
993.
The present-day practices of electrocardiography and vectorardiography are based upon the theory that the surface potential
differences can be assumed to be due to a single dipole inside the body. It is shown in this paper that a dipole cannot account
for all the surface potentials due to realistic current generators, and hence the determination of the current generator from
surface potential measurements based upon such a theory will lead to inconsistent representations of the heart for one and
the same subject.
To demonstrate this point two eccentric dipoles of different strengths and locations representing two muscle fibers are taken
to be the current generator in a homogeneous spherical conductor. The exact surface potentials are then expressed by means
of the “interior sphere theorem” of the authors. With these expressions the magnitude, direction, and location of the resultant
dipole are determined by the method of D. Gabor and C. V. Nelson (J. App. Physics,25, 413–16, 1954). The surface potentials due to this resultant dipole are again exactly expressed by means of the “interior
sphere theorem” and compared with those due to the eccentric dipoles assumed. It can be seen that the differences can be considerable.
It is suggested that the multipole model of the authors (Bull. Math. Biophysics,20, 203–16, 1958) be used as a more accurate and the only unique representation of the heart.
This investigation was supported by the National Heart Institute under a research grant H-2263(c). 相似文献
994.
995.
996.
997.
998.
A pad-plate method of assaying residual amounts of chlortetracycline (CTC) and oxytetracycline (OTC) using Bacillus cereus 213 was used to determine amounts of antibiotic left in tissues and eggs of poultry fed 1,000 and 200 ppm of CTC and OTC in basal feed mixtures. The effects of various methods of cooking the tissues and eggs and the potentiating effect of terephthalic acid (TPA) were studied. It was found that normal methods of roasting, frying, and autoclaving poultry tissue destroyed all residual CTC and OTC, even with the potentiating effect of TPA. The largest amounts of residual antibiotic were found in the liver, then breast, and then thigh tissue when assayed for CTC. Tissue assays for CTC revealed that it was not taken up as extensively as CTC and the largest amounts were found in the liver, then breast. OTC residue was seldom found in the thigh tissue. Terephthalic acid in 0.5% concentration increased the concentration found in all cases. Cooking by poaching and scrambling eggs did not destroy the antibiotic in all cases. 相似文献
999.
1000.