全文获取类型
收费全文 | 888318篇 |
免费 | 83540篇 |
国内免费 | 1054篇 |
出版年
2018年 | 18661篇 |
2017年 | 17206篇 |
2016年 | 17534篇 |
2015年 | 14345篇 |
2014年 | 16725篇 |
2013年 | 24029篇 |
2012年 | 30456篇 |
2011年 | 38906篇 |
2010年 | 29399篇 |
2009年 | 24650篇 |
2008年 | 33116篇 |
2007年 | 35382篇 |
2006年 | 24030篇 |
2005年 | 23340篇 |
2004年 | 23516篇 |
2003年 | 22693篇 |
2002年 | 21930篇 |
2001年 | 35060篇 |
2000年 | 34393篇 |
1999年 | 27705篇 |
1998年 | 10323篇 |
1997年 | 10360篇 |
1996年 | 9921篇 |
1995年 | 9131篇 |
1994年 | 8804篇 |
1993年 | 8845篇 |
1992年 | 22418篇 |
1991年 | 21997篇 |
1990年 | 21431篇 |
1989年 | 20863篇 |
1988年 | 19144篇 |
1987年 | 18366篇 |
1986年 | 17124篇 |
1985年 | 16990篇 |
1984年 | 13977篇 |
1983年 | 12228篇 |
1982年 | 9261篇 |
1981年 | 8390篇 |
1980年 | 7797篇 |
1979年 | 12977篇 |
1978年 | 10224篇 |
1977年 | 9212篇 |
1976年 | 8816篇 |
1975年 | 9831篇 |
1974年 | 10502篇 |
1973年 | 10370篇 |
1972年 | 9706篇 |
1971年 | 8719篇 |
1970年 | 7400篇 |
1969年 | 7261篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The paper submits the results of studies on the kinetics of spermatogenous epithelium cell number after exposure to fast neutrons (60-300 cGy) and gamma-radiation (200-600 cGy). It was shown that a relative decrease in the quantity of spermatocytes is determined by an exponential dose-response curve with D0 of 35 and 120 cGy for neutrons and gamma-radiation respectively. For spermatides and spermatozoa a single D0 value of 20 and 55 cGy was obtained for neutrons and gamma-radiation respectively. As the radiation dose increases the recovery process in the epithelium is substantially decelerated. The equation T1/2 = T1/2(0)e0.0009D well describes the dependence of the half-recovery period T1/2 upon the equivalent dose. 相似文献
992.
993.
994.
995.
996.
The cytotoxic and radiosensitizing effects of hyperthermia was shown on Ehrlich ascites tumor cells heated in vitro. The effect of hyperthermia resulted in the formation of local lesions in membranes of dying cells. 相似文献
997.
998.
THERE are two principal groups of theories of ageing—those which hold that random cell damage is chiefly responsible for the events characteristic of ageing, which culminate in death and those which hold that ageing and death are genetically controlled. It is too soon to decide between these points of view and in any case Bullough1 has shown that they are not mutually exclusive. So far experiments to test the random error theories of ageing, involving exposure of organisms to unnaturally large or even small amounts of agents such as X-rays and mutagenic agents (for reviews, see refs. 2 and 3), have been controversial and inconclusive. 相似文献
999.
Molecular dynamics (MD) simulations of phosphatidylinositol (4,5)-bisphosphate (PIP2) and phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers indicate that the inositol rings are tilted ∼40° with respect to the bilayer surface, as compared with 17° for the P-N vector of POPC. Multiple minima were obtained for the ring twist (analogous to roll for an airplane). The phosphates at position 1 of PIP2 and PIP3 are within an Ångström of the plane formed by the phosphates of POPC; lipids in the surrounding shell are depressed by 0.5-0.8 Å, but otherwise the phosphoinositides do not substantially perturb the bilayer. Finite size artifacts for ion distributions are apparent for systems of ∼26 waters/lipid, but, based on simulations with a fourfold increase of the aqueous phase, the phosphoinositide positions and orientations do not show significant size effects. Electrostatic potentials evaluated from Poisson-Boltzmann (PB) calculations show a strong dependence of potential height and ring orientation, with the maxima on the −25 mV surfaces (17.1 ± 0.1 Å for PIP2 and 19.4 ± 0.3 Å for PIP3) occurring near the most populated orientations from MD. These surfaces are well above the background height of 10 Å estimated for negatively charged cell membranes, as would be expected for lipids involved in cellular signaling. PB calculations on microscopically flat bilayers yield similar maxima as the MD-based (microscopically rough) systems, but show less fine structure and do not clearly indicate the most probable regions. Electrostatic free energies of interaction with pentalysine are also similar for the rough and flat systems. These results support the utility of a rigid/flat bilayer model for PB-based studies of PIP2 and PIP3 as long as the orientations are judiciously chosen. 相似文献
1000.
V T Kondakov A B Okulov M A Filippkin R Z Tandilava I U Artamonov O A Voronenko A N Sazonov 《Vestnik rentgenologii i radiologii》1991,(4):31-35
The paper is concerned with analysis of the results of intraoperative phlebotesticulography, performed in 50 patients with varicocele of degree I-II during Ivanissevich's operation. The effect of surgical intervention was shown to depend upon the quality of ligation of the testicular vein, some parts of which are anastomosed between themselves. The localization of this anastomosis is revealed by means of intraoperative phlebotesticulography, which permits increasing the results of surgical treatment and predicting a course of a postoperative period. 相似文献