全文获取类型
收费全文 | 706篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
化学 | 327篇 |
晶体学 | 5篇 |
力学 | 20篇 |
数学 | 88篇 |
物理学 | 287篇 |
出版年
2021年 | 7篇 |
2020年 | 7篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 5篇 |
2013年 | 23篇 |
2012年 | 41篇 |
2011年 | 45篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 32篇 |
2007年 | 33篇 |
2006年 | 34篇 |
2005年 | 36篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 14篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 20篇 |
1994年 | 27篇 |
1993年 | 25篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1970年 | 3篇 |
1938年 | 5篇 |
1934年 | 5篇 |
1868年 | 4篇 |
排序方式: 共有727条查询结果,搜索用时 15 毫秒
171.
Johnson CF Brown CS Wheeler RM Sager JC Chapman DK Deitzer GF 《Photochemistry and photobiology》1996,63(2):238-242
Oat (Avena sativa cv Seger) seedlings were irradiated with IR light-emitting diode (LED) radiation passed through a visible-light-blocking filter. Infrared LED irradiated seedlings exhibited differences in growth and gravitropic response when compared to seedlings grown in darkness at the same temperature. Thus, the oat seedlings in this study were able to detect IR LED radiation. These findings call into question the use of IR LED as a safe-light for some photosensitive plant response experiments. These findings also expand the defined range of wavelengths involved in radiation-gravity (light-gravity) interactions to include wavelengths in the IR region of the spectrum. 相似文献
172.
Swartz M Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gatto C Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R Harral B 《Physical review letters》1990,64(24):2877-2880
173.
Kral JF Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gatto C Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R Harral B 《Physical review letters》1990,64(11):1211-1214
174.
Burchat PR King M Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gatto C Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R Harral B 《Physical review D: Particles and fields》1990,41(11):3542-3545
175.
Abachi S Derrick M Kooijman P Musgrave B Price L Repond J Sugano K Blockus D Brabson BB Brom J Jung C Ogren H Rust DR Snyder A Cork B Akerlof C Chapman J Errede D Ken MT Kesten P Meyer DI Neal H Nitz D Thun R Tschirhart R Baringer P Bylsma BG Debonte R Low EH McIlwain RL Miller DH Ng CR Rangan K Shibata E 《Physical review D: Particles and fields》1990,41(7):2045-2056
176.
Kathy E. Yokobata John M. Jordan Orvrlle Chapman Curt Krerl 《Photochemistry and photobiology》1986,43(4):391-401
Abstract— We have developed a procedure called a plaque reduction assay to assess the biological activity of duplex circular DNA modified by covalent adduct formation with psoralen derivatives. The replicating form (RF) of bacteriophage DNA modified by photochemical addition of a psoralen derivative was introduced into bacterial cells using the CaCI2 transfection method. The transfected cells. plated upon a confluent lawn of cells permissive for the bacteriophage in the inoculum, provided a measure of the reduction in infectivity of the RF DNA which resulted from its covalent modification. Use of this assay is illustrated in studies which screened and compared the activities of several recently synthesized psoralen derivatives. We describe two new compounds. β-(8-psoralenoxy)-ethanol and β-(8-psoralenoxy)ethylamine that are significantly more active than either 8-methoxypsoralen or trioxsalen in the biological assay 相似文献
177.
J. M. Lynch S. H. T. Harper S. J. Chapman D. A. Veal 《Applied biochemistry and biotechnology》1984,9(4):379-380
Production of composts on the farm from surplus straw might provide a low-cost biotechnological approach for increasing the
value of this lignocellulosic waste. Successful composting depends on the conversion of the polysaccharides (cellulose and
hemicelluloses) of straw by inoculated microorganisms to products that can promote plant growth when applied to the land.
None of the potentially useful products we have identified are produced by cellulolytic organisms. We have therefore studied
mixed populations in which noncellulolytic bacteria depend for growth on the products of fungal cellulolysis. The nature and
yield of bacterial products depends not only on conditions within the compost, but also on the microbial inoculants used.
Under defined laboratory conditions, using pure cellulose, N2 is fixed by the anaerobic bacteriumClostridium butyricum in association with a cellulolytic fungus such asTrichoderma sp. A similar association has been achieved on straw withPenicillium corylophilum as the cellulolytic fungus.
Cellulolytic fungi can also provide available substrates for the production of bacterial polysaccharides that can improve
the structure of unstable soils. The yield of polysaccharide and its efficacy in soil aggregate stabilization again varies
with the inoculants used.
Such composts can thus contribute to plant nutrition and to soil structure. The adoption ofTrichoderma spp. as the cellulolytic inoculants would further extend the potential value of the compost to include the biocontrol of
plant pathogens. 相似文献
178.
Puskar L Barran PE Duncombe BJ Chapman D Stace AJ 《The journal of physical chemistry. A》2005,109(1):273-282
Using a pickup technique in association with high-energy electron impact ionization, complexes have been formed in the gas phase between Pb(2+) and a wide range of ligands. The coordinating atoms are oxygen, nitrogen, sulfur, and phosphorus, together with complexes consisting of benzene and argon in association with Pb(2+). Certain ligands are unable to stabilze the metal dication, the most obvious group being water and the lower alcohols, but CS(2) is also unable to form [Pb(CS(2))(N)](2+) complexes. Unlike many other metal dication complexes, those associated with lead appear to exhibit very little chemical reactivity following collisional activation. Such reactions are normally promoted via charge transfer and are initiated using the energy difference between M(2+) + e(-) --> M(+) and L --> L(+) + e(-), which is typically approximately 5 eV. In the case of Pb(2+), this energy difference usually leads to the appearance of L(+) and the loss of a significant fraction of the remaining ligands as neutral species. In many instances, Pb(+) appears as a charge-transfer product. The only group of ligands to consistently exhibit chemical reactivity are those containing sulfur, where a typical product might be PbS(+)(L)(M) or PbSCH(3)(+)(L)(M). 相似文献
179.
B. D. Hirsch N. C. Walz B. E. Meeker M. R. Arnfield J. Tulip M. S. McPhee J. D. Chapman 《Photochemistry and photobiology》1987,46(5):847-852
Abstract The administration of misonidazole (MISO) to Fischer x Copenhagen rats whose R3327-H prostate tumors were treated with photodynamic therapy (PDT) produced enhanced tumor growth delays and cures. This potentiation of PDT by MISO was previously observed with R3327-AT tumors and was postulated to result from drug cytotoxicity of naturally-occurring and PDT-induced hypoxic cells. Radioactively-labelled MISO has been developed as a marker for tissue p02 at the cellular level and [3 H]MISO was administered to R3327-AT and R3327-H tumor-bearing rats before and after standard PDT treatments. The amount of 3 H in tissues 24 h after drug administration was a measure of'bound MISO'which reflects average tissue oxygenation. [3 H]MISO retained in R3327-AT tumors was ˜4x and in liver tissue ˜2x that retained in muscle, heart, brain and R3327-H tumors (1x). Tumors treated with Photofrin II and lased with 1000 J showed a 6-fold increase in retained [3 H]MISO in R3327-H tumors and a 2-fold increase in retained [3 H]MISO in R3327-AT tumors. The absolute levels of retained 3 H in both tumors after PDT were similar. These data provide direct evidence that PDT induces rapid hypoxia in both tumors. When the gastrocnemius muscle of the rat leg was similarly treated, the amount of [3 H]MISO retained was ˜4x greater than that in untreated muscle. This result suggests that PDT-induced hypoxia is not selective to just tumor tissue. These data suggest that the hypoxia-inducing property of PDT might be exploited in combination with hypoxic cell cytotoxins to produce improved tumor responses and cures. 相似文献
180.
Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R Harral B Harris FA 《Physical review letters》1989,63(22):2447-2451