全文获取类型
收费全文 | 4233篇 |
免费 | 222篇 |
出版年
2022年 | 22篇 |
2021年 | 40篇 |
2020年 | 25篇 |
2019年 | 54篇 |
2018年 | 57篇 |
2017年 | 51篇 |
2016年 | 65篇 |
2015年 | 105篇 |
2014年 | 136篇 |
2013年 | 380篇 |
2012年 | 200篇 |
2011年 | 220篇 |
2010年 | 122篇 |
2009年 | 136篇 |
2008年 | 219篇 |
2007年 | 254篇 |
2006年 | 253篇 |
2005年 | 228篇 |
2004年 | 234篇 |
2003年 | 254篇 |
2002年 | 216篇 |
2001年 | 100篇 |
2000年 | 109篇 |
1999年 | 102篇 |
1998年 | 75篇 |
1997年 | 61篇 |
1996年 | 45篇 |
1995年 | 40篇 |
1994年 | 30篇 |
1993年 | 33篇 |
1992年 | 49篇 |
1991年 | 47篇 |
1990年 | 39篇 |
1989年 | 43篇 |
1988年 | 26篇 |
1987年 | 26篇 |
1986年 | 28篇 |
1985年 | 36篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 18篇 |
1981年 | 19篇 |
1980年 | 19篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 11篇 |
1975年 | 25篇 |
1974年 | 13篇 |
1973年 | 18篇 |
1966年 | 10篇 |
排序方式: 共有4455条查询结果,搜索用时 15 毫秒
101.
Two new non-protein amino acids, Nδ-benzoyl-l-ornithine and Nδ-benzoyl-l-γ-hydroxyornithine have been characterized from the seeds of Vicia pseudo-orobus. 相似文献
102.
Catharanthine and akuammicine, together with ajmalicine and strictosidine, were isolated from a culture strain of Catharanthus roseus suspension cells. The biosynthetic capability of the cultured cells to produce akuammicine, catharanthine and vindoline was confirmed by feeding experiments with dl-tryptophan-[3-14C] to yield the radioactive alkaloids. 相似文献
103.
104.
The physiological action of CCC for leaves of Kyoho grapes wasstudied. Leaves from the lower to upper positions of the primaryshoots and (primary) lateral shoots showed uneven photosyntheticactivities with peaks. The photosynthetic activity of each leaffrom both shoots was increased by treatment with CCC, whereasrespiratory activity was not affected with CCC. In the primaryshoots, CCC treatment increased the contents of chlorophylla and b in the leaves, but in the lateral shoots only chlorophyllb contents were increased. Dry weights of the leaves from thelateral shoots increased with CCC, but those of leaves locatedin the vicinity of nodes bearing the fruit clusters varied slightlyor were almost the same as the dry weight of non-treated leaves.Leaf thickness was increased by CCC and paralleled the variationin dry weight. The leaf area was decreased by CCC. (Received April 19, 1980; ) 相似文献
105.
106.
Hajime Tokuda Tsutomu Unemoto 《Biochemical and biophysical research communications》1981,102(1):265-271
The membrane potential generated at pH 8.5 by K+-depleted and Na+-loaded is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na+-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na+ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na+-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na+ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na+ chemical gradient. 相似文献
107.
108.
Hajime Iizuka Keniji Adachi Kenneth M. Halprin Victor Levine 《Biochimica et Biophysica Acta (BBA)/General Subjects》1976,444(3):685-693
Adenosie, AMP, ADP and ATP activated adenylate cyclase in pig skin (epidermis) slices resulting in the accumulation of cyclic AMP. This effect was highly potentiated by the addition of the cyclic AMP-phophodiesterase inhibitor, papaverine. But another inhibitor, theophylline, strongly blocked the activation of adenylate cyclase by adenosine and adenine nucleotides. Theophylline apparently competed with adenosine for the cell suface receptor. Like theophylline, the addition of adenine alone caused no accumulation of cyclic AMP, but it significantly inhibited the stimulatory effect of adenosine. Guanosine, or guanine, cytidine, uridine, or thymidine nucleotides has no effect on the accumulation of cyclic AMP. Among other adenine nucleotides was tested, adenosine 5′-monophosphoramidate, but not adenosine 5′-monosulfate, significantly increased cyclic AMP especially with the addition of papaverine. Neither 2′- nor 3′-adenylic acid were effective. Our data indicate that pig epidermis has four specific and independent adenylate cyclase systems for adenosine (and adenine nucleotides), histamine, epinephrine and prostaglandin E. 相似文献
109.
110.
A male infant with monosomy 21. 总被引:2,自引:0,他引:2
A male infant with total monosomy 21 identified by Q-, G- and R-banding is described. His main symptoms are hypertonia, micrognathia, microphthalmus, imperforate anus, ambiguous external genitalia, floating and malopposed thumbs, overlying fingers, right clubfoot and growth retardation. Both parents are phenotypically as well as karotypically normal. 相似文献