全文获取类型
收费全文 | 1940篇 |
免费 | 333篇 |
国内免费 | 4篇 |
专业分类
2277篇 |
出版年
2022年 | 17篇 |
2021年 | 23篇 |
2019年 | 21篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 42篇 |
2015年 | 79篇 |
2014年 | 66篇 |
2013年 | 94篇 |
2012年 | 105篇 |
2011年 | 96篇 |
2010年 | 71篇 |
2009年 | 45篇 |
2008年 | 75篇 |
2007年 | 77篇 |
2006年 | 68篇 |
2005年 | 75篇 |
2004年 | 73篇 |
2003年 | 73篇 |
2002年 | 76篇 |
2001年 | 76篇 |
2000年 | 49篇 |
1999年 | 42篇 |
1998年 | 38篇 |
1997年 | 25篇 |
1996年 | 18篇 |
1995年 | 25篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 33篇 |
1991年 | 51篇 |
1990年 | 51篇 |
1989年 | 56篇 |
1988年 | 38篇 |
1987年 | 36篇 |
1986年 | 36篇 |
1985年 | 27篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1978年 | 22篇 |
1977年 | 17篇 |
1974年 | 23篇 |
1973年 | 17篇 |
1972年 | 15篇 |
1970年 | 17篇 |
1968年 | 16篇 |
排序方式: 共有2277条查询结果,搜索用时 0 毫秒
1.
2.
3.
E. coli cells containing a temperature-sensitivednaE mutation, in the α-subunit of holoenzyme DNA polymerase III, do not survive at the restrictive temperature. Such cells may
survive in the presence of thepcbA1 mutation, an allele of thegyrB gene. Such survival is dependent on an active DNA polymerase I. Evidence indicates that DNA polymerase I interacts directly
in the replisome (REP·A). Despite normal survival for cells using thepcbA replication pathway after some type of DNA damage, we have noted a failure of damage-induced mutagenesis. Here we present
evidence supporting a model of replisome pausing in cells dependent upon thepcbA replication pathway. The model argues that the (REP·A) complex pauses longer at the site of the lesion, allowing excision
repair to occur completely. In the normal replication pathway (REP·E) bypass of the lesion occurs, fixing the mutation. 相似文献
4.
5.
M Zeviani M Nakagawa J Herbert M I Lomax L I Grossman A A Sherbany A F Miranda S DiMauro E A Schon 《Gene》1987,55(2-3):205-217
6.
7.
H. Barton Grossman Gary Wedemeyer Judith Stein 《Cancer immunology, immunotherapy : CII》1988,26(3):269-272
Summary The autologous serologic reactivity of 13 patients with bladder cancer was evaluated using cell lines derived from each individual's own tumor as targets. Protein A and immune adherence assays were employed to determine antibody binding to the tumor targets at varying passage numbers. Autologous reactivity was found in 6 of the 13 cell lines tested. However, the titer was usually low regardless of the passage number. Seven autologous serum/cell line combinations were tested using both low and high passage cells as targets. In six of these combinations, the degree of antibody binding was similar with both low and high passage target cells. The incidence of autologous reactivity in the 12 patients with urothelial tumors was 50%.This investigation was supported by PHS Grant number CA36933, awarded by the National Cancer Institute, DHHS. 相似文献
8.
Vered Barenholz-Paniry Jacob S. Ishay Zvi Grossman 《Bulletin of mathematical biology》1988,50(6):661-679
Rhythmic “circa-second” contrations of larvae of the hornetVespa orientalis, believed to serve as hunger signals, were studied. A considerable degree of coordination among individual larvae, both in
frequency and phase of these contractions, has been observed. The oscillations of singly isolated larvae are of short duration,
non-constant, with increasing intervals in between and there is a substantial variability in the patterns shown by different
larvae. In contrast, the association of two or more larvae leads to enhancement of their periodic behaviour and to (partial)
entrainment. Communication among larvae may perhaps be mediated by the sound pulses (“scratching” noises) which are generated
by these contractions. We have subjected individual and grouped larvae to external sound pulses and were able to demonstrate:
(a) enhancement of rhythmic activity; (b) phase resetting; (c) entrainment to an external oscillator within a range of frequencies;
(d) the existence of a subharmonic mode of entrainment. We propose a simple phenomenologic model to account for these larvae
responses. Our model assumes the existence of an “energy” variable which declines with time but is upgraded, in a phase-dependent
way, by external stimuli.
Based in part on work performed by V. Barenholz-Paniry in partial fulfillment of the requirements for the M.Sc. degree from
the Sackler Faculty of Medicine, Tel Aviv University, 1986. 相似文献
9.
Formation of double-walled microtubules and multilayered tubulin sheets by basic proteins 总被引:1,自引:0,他引:1
E Unger K J B?hm H Müller H Grossman H Fenske W Vater 《European journal of cell biology》1988,46(1):98-104
Some basic proteins enable microtubule protein to form special assembly products in vitro, known as double-walled microtubules. Using histones (H1, core histones) as well as the human encephalitogenic protein to induce the formation of double-walled microtubules, we made the following electron microscopic observations: (1) Double-walled microtubules consist of an "inner" microtubule which is covered by electron-dense material, apparently formed from the basic protein, and by a second tubulin wall. (2) The tubulin of the second wall seems to be arranged as protofilaments, surrounding the inner microtubule in a helical or ring-like manner. (3) The surface of double-walled microtubules lacks the projections of microtubule-associated proteins, usually found on microtubules. (4) In the case of protofilament ribbons (incomplete microtubules), H1 binds exclusively to their convex sides that correspond to the surface of microtubules. Zn2+-induced tubulin sheets, consisting in contrast to microtubules of alternately arranged protofilaments, are covered by H1 on both surfaces. Furthermore, multilayered sheet aggregates appeared. The results indicate that the basic proteins used interact only with that protofilament side which represents the microtubule surface. In accordance with this general principle, models on the structure of double-walled microtubules and multilayered tubulin sheets were derived. 相似文献