全文获取类型
收费全文 | 956篇 |
免费 | 11篇 |
国内免费 | 3篇 |
专业分类
化学 | 492篇 |
晶体学 | 6篇 |
力学 | 13篇 |
数学 | 43篇 |
物理学 | 371篇 |
综合类 | 45篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 35篇 |
2012年 | 38篇 |
2011年 | 37篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 53篇 |
2007年 | 72篇 |
2006年 | 55篇 |
2005年 | 70篇 |
2004年 | 56篇 |
2003年 | 46篇 |
2002年 | 40篇 |
2001年 | 31篇 |
2000年 | 29篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 9篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1970年 | 4篇 |
1966年 | 3篇 |
排序方式: 共有970条查询结果,搜索用时 0 毫秒
91.
92.
93.
Cryopreservation of Drosophila melanogaster embryos 总被引:3,自引:0,他引:3
P L Steponkus S P Myers D V Lynch L Gardner V Bronshteyn S P Leibo W F Rall R E Pitt T T Lin R J MacIntyre 《Nature》1990,345(6271):170-172
There is an urgent need to preserve the ever-increasing number (greater than 30,000) of different genetic strains of D. melanogaster that are maintained in national and international stock centres and in the laboratories of individual investigators. In all cases, the stocks are maintained as adult populations and require transfer to fresh medium every two to four weeks. This is not only costly in terms of materials, labour and space, but unique strains are vulnerable to accidental loss, contamination, and changes in genotype that can occur during continuous culture through mutation, genetic drift or selection. Although cryopreservation of Drosophila germ-plasm would be an enormous advantage, many attempts using conventional procedures have been unsuccessful. D. melanogaster embryos are refractory to conventional cryopreservation procedures because of the contravening conditions required to minimize mortality resulting from both intracellular ice formation and chilling injury at subzero temperatures. To overcome these obstacles, we have developed a vitrification procedure that precludes intracellular ice formation so that the embryos can be cooled and warmed at ultra-rapid rates to minimize chilling injury, and have recovered viable embryos following storage in liquid nitrogen. In a series of 53 experiments, a total of 3,711 larvae emerged from 17,280 eggs that were cooled in liquid nitrogen (18.4 +/- 8.8%). Further, using a subset from this population, approximately 3% of the surviving larvae (24/800) developed into adults. These adults were fertile and produced an F1 generation. 相似文献
94.
Summary The method of iterative target transformation factor analysis (ITTFA) used in conjunction with second derivative peak finding
has shown to be a practical method for the peak deconvolution and reconstruction of HPLC chromatograms and spectra. The second
derivative method of peak finding is acceptable for resolutions above 0.5 for peaks of similar heights. Above 0.5 resolution
the labelling gives correct results where the spectra are substantially different and also when reasonably similar. Below
this value the peak labelling was still accurate where the spectra were different. Solvent effects on the spectra of the compounds
studied are small and do not hinder the peak labelling process. Thus small “local” libraries are feasible.
Presented at the 17th International Symposium on Chromatography, September 25–30, 1988. Vienna, Austria. 相似文献
95.
A. Factor J. C. Lynch F. H. Greenberg 《Journal of polymer science. Part A, Polymer chemistry》1987,25(12):3413-3422
Previous studies of the photodegradation of bisphenol A polycarbonate (BPA PC) indicate that both alkyl side chain and ring oxidation play significant roles. In order to determine the relative importance of these two pathways in the photoyellowing that accompanies photodegradation, side chain free polycarbonates based on 3,3′-dihydroxydiphenyl ether were synthesized and tested. Both accelerated weathering experiments using a QUV test apparatus and outdoor weathering indicated that these polymers photoyellowed faster than BPA PC. This suggests that ring oxidation is an important source of photoyellowing of aromatic polycarbonates. 相似文献
96.
M. Bonesini E. Bonvin R. Bopp L. J. Carroll A. J. Cass D. Cavalli G. Costa S. U. Chung M. Donnat P. A. Dorsaz M. Feliks J. R. Fischer L. Fluri F. Gianotti S. Jack J. N. Jackson M. N. Kienzle-Focacci J. G. Lynch L. Mandelli M. Martin L. Mathys A. Maxwell M. Mazzanti P. J. Negus S. Pensotti-Rancoita L. Perini D. Perrin R. W. Poultney W. H. Range L. Rosselet S. W. Snow A. S. Thompson R. M. Turnbull J. Wells M. Werlen WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1989,44(1):71-78
The structure of events associated with the production of direct photons in π? p, π+ p andpp reactions of 280 GeV/c has been studied using data from the WA 70 experiment at the CERN SPS. Results are presented on the distributions of the fractional momenta of the colliding partons and on the fragmentation of the recoil jet and a comparison is made with predictions using the structure functions of Duke and Owens in the Lund Monte Carlo with string fragmentation. 相似文献
97.
Lees JP Poireau V Tisserand V Garra Tico J Grauges E Martinelli M Milanes DA Palano A Pappagallo M Eigen G Stugu B Brown DN Kerth LT Kolomensky YG Lynch G Koch H Schroeder T Asgeirsson DJ Hearty C Mattison TS McKenna JA So RY Khan A Blinov VE Buzykaev AR Druzhinin VP Golubev VB Kravchenko EA Onuchin AP Serednyakov SI Skovpen YI Solodov EP Todyshev KY Yushkov AN Bondioli M Kirkby D Lankford AJ Mandelkern M Stoker DP Atmacan H Gary JW Liu F Long O Vitug GM Campagnari C Hong TM Kovalskyi D 《Physical review letters》2011,107(22):221803
We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Υ(2S) or Υ(3S) meson, Υ→γA(0). The data have been recorded by the BABAR experiment at the Υ(3S) and Υ(2S) center-of-mass energies and include (121.3±1.2)×10(6) Υ(3S) and (98.3±0.9)×10(6) Υ(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Υ(nS)→γA(0))B(A(0)→hadrons) (n=2 or 3) that range from 1×10(-6) for an A(0) mass of 0.3 GeV/c(2) to 8×10(-5) at 7 GeV/c(2). 相似文献
98.
Margriet V. D. Z. Park Iseult Lynch Sonia Ram��rez-Garc��a Kenneth A. Dawson Liset de la Fonteyne Eric Gremmer Wout Slob Jacob J. Bried�� Andreas Elsaesser C. Vyvyan Howard Henk van Loveren Wim H. de Jong 《Journal of nanoparticle research》2011,13(12):6775-6787
The biological response to four well-characterized amorphous silica nanoparticles was investigated in RAW 264.7 macrophages in view of their potential application as drug carriers to sites of inflammation. All silica nanoparticles-induced cell membrane damage, reduced metabolic activity, generated ROS and released various cytokines, but to different extents. Two silica nanoparticles of 34 nm (A and B) with different zetapotentials were more cytotoxic than (aggregated) 11 and 248 nm nanoparticles, while cytokines were mostly induced by the (aggregated) 11 nm and only one of the 34 nm nanoparticles (34A). The results indicate that specific silica nanoparticles may have counterproductive effects, for example when used as carriers of anti-inflammatory drugs. The physicochemical properties determining the response of nanoparticles vary for different responses, implying that a screening approach for the safe development of nanoparticles needs to consider the role of combinations of (dynamic) physicochemical properties and needs to include multiple toxicity endpoints. 相似文献
99.
Recently, high concentrations of intracellular trehalose (>200mM) were employed to enhance the cryoprotection and desiccation protection of human erythrocytes. However, significant challenges must be overcome if this advancement is to be translated into clinical practice. It is here demonstrated that 247 ± 5 mM intracellular trehalose caused the lysis of 60 ± 2 percent of erythrocytes upon resuspension in PBS of physiological osmolality (300 mOsm) and caused surviving cells to swell up to 140 ± 2 percent of isotonic cell volume. Trehalose loaded cells also exhibited 24 ± 1 percent incidence of phosphatidylserine translocation upon resuspension in 300 mOsm PBS, likely due to loading induced cell swelling. Un-loading of trehalose from erythrocytes using the membrane-permeabilizing biopolymer PP-50 was investigated as a technique to mitigate these damaging effects. After erythrocyte un-loading from 247 ± 5 mM to 39 ± 2 mM intracellular trehalose, cell lysis at 300 mOsm PBS was reduced from 60 ± 2 percent to 17 ± 3 percent. Un-loading also reduced cellular incidence of PS translocation in resuspended cells from 24 ± 1 percent to 13 ± 1 percent. 相似文献
100.
Daniel E. Lynch Ian McClenaghan 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):e535-e535
The structure of the title compound, C22H18N6O4, (I), comprises two unique molecules that separately form hydrogen‐bonded polymer chains via N—H?N interactions. Molecular independence arises due to a difference in the dihedral angles between the linked rings, i.e. 52.19 (4) and 46.17 (5)°. 相似文献