全文获取类型
收费全文 | 303335篇 |
免费 | 36870篇 |
国内免费 | 1275篇 |
出版年
2016年 | 3385篇 |
2015年 | 5010篇 |
2014年 | 5871篇 |
2013年 | 8043篇 |
2012年 | 9101篇 |
2011年 | 8905篇 |
2010年 | 6038篇 |
2009年 | 5647篇 |
2008年 | 7715篇 |
2007年 | 7804篇 |
2006年 | 7413篇 |
2005年 | 7252篇 |
2004年 | 7017篇 |
2003年 | 7037篇 |
2002年 | 6722篇 |
2001年 | 11300篇 |
2000年 | 11377篇 |
1999年 | 9408篇 |
1998年 | 3711篇 |
1997年 | 3852篇 |
1996年 | 3843篇 |
1995年 | 3578篇 |
1994年 | 3590篇 |
1993年 | 3507篇 |
1992年 | 8257篇 |
1991年 | 8022篇 |
1990年 | 7818篇 |
1989年 | 7735篇 |
1988年 | 7296篇 |
1987年 | 7227篇 |
1986年 | 6695篇 |
1985年 | 6829篇 |
1984年 | 5733篇 |
1983年 | 5136篇 |
1982年 | 4100篇 |
1981年 | 3930篇 |
1980年 | 3567篇 |
1979年 | 5920篇 |
1978年 | 4626篇 |
1977年 | 4431篇 |
1976年 | 4231篇 |
1975年 | 4576篇 |
1974年 | 5032篇 |
1973年 | 4925篇 |
1972年 | 4581篇 |
1971年 | 4132篇 |
1970年 | 3642篇 |
1969年 | 3664篇 |
1968年 | 3267篇 |
1967年 | 2820篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
151.
Shira Weingarten-Gabbay Susan Klaeger Siranush Sarkizova Leah R. Pearlman Da-Yuan Chen Kathleen M.E. Gallagher Matthew R. Bauer Hannah B. Taylor W. Augustine Dunn Christina Tarr John Sidney Suzanna Rachimi Hasahn L. Conway Katelin Katsis Yuntong Wang Del Leistritz-Edwards Melissa R. Durkin Christopher H. Tomkins-Tinch Pardis C. Sabeti 《Cell》2021,184(15):3962-3980.e17
- Download : Download high-res image (225KB)
- Download : Download full-size image
152.
J H Richardson L L Steinmetz S B Deutscher W A Bookless W L Schmelzinger 《Analytical biochemistry》1979,97(1):17-23
A synchronously pumped krypton ion dye laser fluorescence system is shown to provide tunable, polarized, subnanosecond pulses at high repetition rates, modest peak powers, and low energy. Such a source is uniquely suited to fluorescence investigations of biochemical mechanisms. Applications of this fluorescence excitation source to analysis, life-time determination, and depolarization effects are discussed. 相似文献
153.
Study of the posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β-gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot-pad, shows a pattern of histogenesis directly comparable to that of β-glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis. 相似文献
154.
155.
A double antibody radioimmunoassay technique is described for the measurement of anti-zona antibodies in the peripheral plasma of marmosets actively immunized against intact cow zonae pellucidae. The method has been shown to be a reliable, repeatable indicator of antibody titer, enabling direct comparison of the response obtained between marmosets. This is the first report of a procedure describing the active immunization of a primate against zona antigens, and the first time a radioimmunoassay technique has been used to monitor profiles of anti-cow zona antibody production following active immunization. The method should prove to be a useful tool in the evaluation of zona antigens as agents for immunocontraception. 相似文献
156.
A microcomputer mainframe linked system is described which allows video camera data capture and storage of one-dimensional whole-cell protein electrophoresis gel images, processing of normalized traces to produce a similarity matrix, and analysis of the matrix using the commercial cluster analysis program CLUSTAN. A new similarity coefficient is introduced which takes into account both band position and intensity. Forty-five strains of Haemophilus influenzae, including the eight biotypes and six serotypes, were analyzed using this system. Results demonstrated groupings which are consistent with known genetic relationships. 相似文献
157.
158.
159.
Self-splicing of group II introns in vitro: lariat formation and 3' splice site selection in mutant RNAs 总被引:10,自引:0,他引:10
Deletion or substitution of the branch A residue in group II intron bl1 significantly reduces splicing activity; yet, residual exon ligation is correct, and lariats have their branch points at the normal distance from the 3' end of the intron. Mutations in the sequence facing the branch point also allow residual lariat formation; however, free 3' exons are generated with false 5' termini, all of which are within a UCACA consensus sequence located upstream or downstream of the normal 3' splice site. These results indicate that both the conserved 3' splice site APy and the spatial arrangements in stem 6 are crucial for correct 3' splice site selection. 相似文献
160.
Guangjie Li Futian Peng Lin Zhang Xingzheng Shi Zhaoyan Wang 《Molecular biology reports》2010,37(2):947-954
Sucrose non-fermenting-1-related protein kinase-1 (SnRK1) plays an important role in metabolic regulation in plant. To understand
the molecular mechanism of amino acids and carbohydrate metabolism in Malus hupehensis Rehd. var. pinyiensis Jiang (Pingyi Tiancha, PYTC), a full-length cDNA clone encoding homologue of SnRK1 was isolated from PYTC by Rapid Amplification
of cDNA Ends (RACE). The clone, designated as MhSnRK1, contains 2063 nucleotides with an open reading frame of 1548 nucleotides. The deduced 515 amino acids showed high identities
with other plant SnRK1 genes. Quantitative real-time PCR analysis revealed this gene was expressed in roots, stems and leaves. Exposing seedlings
to nitrate caused and initial decrease in expression of the MhSnRK1 gene in roots, leaves and stems in short term. Ectopic expression of MhSnRK1 in tomato mainly resulted in higher starch content in leaf and red-ripening fruit than wild-type plants. This result supports
the hypothesis that overexpression of SnRK1 causes the accumulation of starch in plant cells. All the results suggest that
MhSnRK1 may play important roles in carbohydrate and amino acid metabolisms. 相似文献