全文获取类型
收费全文 | 228967篇 |
免费 | 14977篇 |
国内免费 | 45篇 |
专业分类
243989篇 |
出版年
2021年 | 1773篇 |
2018年 | 3125篇 |
2017年 | 3024篇 |
2016年 | 3666篇 |
2015年 | 3201篇 |
2014年 | 4438篇 |
2013年 | 6322篇 |
2012年 | 7581篇 |
2011年 | 8163篇 |
2010年 | 5749篇 |
2009年 | 4877篇 |
2008年 | 7281篇 |
2007年 | 7579篇 |
2006年 | 7266篇 |
2005年 | 6810篇 |
2004年 | 6952篇 |
2003年 | 6696篇 |
2002年 | 6650篇 |
2001年 | 9384篇 |
2000年 | 9100篇 |
1999年 | 7106篇 |
1998年 | 2132篇 |
1997年 | 1959篇 |
1996年 | 1820篇 |
1992年 | 5624篇 |
1991年 | 5881篇 |
1990年 | 5866篇 |
1989年 | 5819篇 |
1988年 | 5442篇 |
1987年 | 5068篇 |
1986年 | 4635篇 |
1985年 | 4850篇 |
1984年 | 3819篇 |
1983年 | 3146篇 |
1982年 | 2056篇 |
1981年 | 1761篇 |
1980年 | 1757篇 |
1979年 | 3439篇 |
1978年 | 2665篇 |
1977年 | 2446篇 |
1976年 | 2429篇 |
1975年 | 2951篇 |
1974年 | 3252篇 |
1973年 | 3233篇 |
1972年 | 2888篇 |
1971年 | 2707篇 |
1970年 | 2322篇 |
1969年 | 2243篇 |
1968年 | 2141篇 |
1967年 | 1895篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
972.
A. V. Timofeev 《Plasma Physics Reports》2009,35(11):912-923
A previously developed method for analyzing the plasma processing of spent nuclear fuel is generalized to a plasma containing
multicharged fuel ions. In such a plasma, ion cyclotron resonance heating of nuclear ash ions should be carried out in two
monochromatic RF fields of different frequencies, provided that the fraction of ξ multicharged ions is small, ξ ≤ 0.1, a condition
that substantially restricts the productivity of systems for processing spent nuclear fuel. Ways of overcoming this difficulty
are discussed. 相似文献
973.
J.J. Virgen-Ortíz V. Ibarra-Junquera P. Escalante-Minakata J.A. Osuna-Castro J. de J. Ornelas-Paz N.A. Mancilla-Margalli R.L. Castañeda-Aguilar 《Analytical biochemistry》2013
This work presents a rapid and simple freeze centrifugation method to concentrate dilute protein solutions for detection by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) Coomassie blue staining. Moreover, a simple way to assemble a cryoconcentration device is presented, and its use is discussed. Commercial purified protein standard and an enzyme with high fructosyltransferase (FTase) activity, coming from target fractions obtained by chromatographic separation, were used as an example. FTase, coming directly from the chromatographic fractions, was difficult to view through SDS–PAGE analysis; however, it was easily visualized, and its activity was enhanced, after the application of the freeze centrifugation protocol presented here. 相似文献
974.
975.
Measurements of the coefficient of water molecules self-diffusion (D) and the time of spin-lattice relaxation (T
1) in prosenchyme (elongated) plant cells, whose length significantly exceeding their transverse size, show that the orientation of plant tissues in the H
0field significantly affects the measured parameters. We conclude that this effect should be taken into account in experiments on the measurement of self-diffusion coefficients and time of proton spin-lattice relaxation in plant tissues containing prosenchyme cells. 相似文献
976.
V. V. Galat 《Russian Journal of Developmental Biology》2000,31(1):1-8
Recent success in assisted fertilization mainly depended on the development of sperm microinjection methods: intracytoplasmic
sperm injection and subzonal insemination. Some basic mechanisms that under-lie fertilization were revealed by using intracytoplasmic
sperm injection. In respect to this, problems of fertility, oocyte activation, formation of pronuclei and practical aspects
of intracytoplasmic sperm injection are discussed. 相似文献
977.
978.
F. Giuliano K. Mac Kenna S. Droupy O. Rampin V. Izard G. Benoit A. Jardin 《Andrologie》1999,9(2):226-246
Seminal emission and sperm expulsion are under the control of both the sympathetic and parasympathetic outflows and also of the somatic innervation conveyed by the pudendal nerve. The 2 phases of ejaculation are reflexive with the reflexes handled at the thoraco-lumbar and sacral levels of the spinal cord. Such a spinal organization remains widely unknown. The role of various peripheral neurotransmitters has been evidenced including norepinephrine and acetylcholine and also peptidergic, purinergic i.e. ATP and nitric oxide. Stimulation of the seminal tract afferents play a crucial in the onset of ejaculatory mechanisms. Except for the dorsal nerve of the penis, there is a lack of information concerning these afferents. Several supraspinal centers i.e. hypothalamus, medial amygdala, pons and nucleus paragigantocellularis exert descending and ascending inhibitory and excitatory influences on spinal nuclei controlling emission and expulsion of sperm. Central neurotransmission responsible for this supraspinal control could involve serotonin, oxytocin and norepinephrine. In the light of the available anatomical and neurophysiological data, pathophysiological aspects of ejaculatory disorders are futher discussed. Premature ejaculation could be related to a periheral and central hypersentivity. Most of the other ejaculation abnormalities are likely mainly related to an impairment of the central mechanisms. 相似文献
979.
980.