全文获取类型
收费全文 | 4890篇 |
免费 | 83篇 |
国内免费 | 17篇 |
专业分类
化学 | 2723篇 |
晶体学 | 22篇 |
力学 | 104篇 |
数学 | 519篇 |
物理学 | 1622篇 |
出版年
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 28篇 |
2016年 | 69篇 |
2015年 | 56篇 |
2014年 | 62篇 |
2013年 | 200篇 |
2012年 | 172篇 |
2011年 | 205篇 |
2010年 | 115篇 |
2009年 | 94篇 |
2008年 | 187篇 |
2007年 | 247篇 |
2006年 | 209篇 |
2005年 | 221篇 |
2004年 | 226篇 |
2003年 | 159篇 |
2002年 | 133篇 |
2001年 | 109篇 |
2000年 | 108篇 |
1999年 | 62篇 |
1998年 | 46篇 |
1997年 | 61篇 |
1996年 | 68篇 |
1995年 | 55篇 |
1994年 | 68篇 |
1993年 | 82篇 |
1992年 | 109篇 |
1991年 | 72篇 |
1990年 | 82篇 |
1989年 | 67篇 |
1988年 | 49篇 |
1987年 | 64篇 |
1986年 | 66篇 |
1985年 | 104篇 |
1984年 | 92篇 |
1983年 | 73篇 |
1982年 | 70篇 |
1981年 | 82篇 |
1980年 | 61篇 |
1979年 | 68篇 |
1978年 | 69篇 |
1977年 | 62篇 |
1976年 | 53篇 |
1975年 | 69篇 |
1974年 | 70篇 |
1973年 | 80篇 |
1972年 | 57篇 |
1971年 | 41篇 |
1970年 | 40篇 |
排序方式: 共有4990条查询结果,搜索用时 15 毫秒
81.
Abe F Albrow M Amidei D Anway-Wiese C Apollinari G Atac M Auchincloss P Azzi P Bacchetta N Baden AR Badgett W Bailey MW Bamberger A de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Bartalini P Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Beretvas A Berge JP Bertolucci S Biery K Bhadra S Binkley M Bisello D Blair R Blocker C Bodek A Bolognesi V Booth W Boswell C Brandenburg G Brown D Buckley-Geer E Budd HS Busetto G 《Physical review D: Particles and fields》1994,50(9):5562-5579
82.
T. M. Brown R. W. Pitz C. F. Hess C. P. Wood 《Applied physics. B, Lasers and optics》1994,59(3):351-356
Pulsed Photothermal Laser Deflection (PLD) is developed to make temporally and spatially resolved measurements of NO2 and smoke. The rapid response PLD signal is produced when a HeNe probe beam is deflected by a thermal lens produced by a pulsed XeCl-excimer laser pumped dye laser. The fast time response (30 ns) and good spatial resolution make the PLD method a candidate for future in situ measurements in turbulent engine exhausts. The PLD signals, measured in a sample cell, exhibit a linear response for NO2 concentrations from 3 ppm to 208 ppm and for smoke concentrations from 0.3 mg/m3 to 10 mg/m3. With a low pulse energy of 4 mJ, single-shot PLD measurements in a sample cell have accuracies of ± 14 ppm for NO2 indicating accuracies of ±0.7 mg/m3 for smoke. With increased pulse energy and multi-shot averaging, sensitivities of ± 0.4 ppm of NO2 or ± 20 µg/m3 of smoke are expected. 相似文献
83.
84.
85.
86.
87.
Gribble GW Switzer FL Bushweller JH Jewett JG Brown JH Dion JL Bushweller CH Byrn MP Strouse CE 《The Journal of organic chemistry》1996,61(13):4319-4327
The (1)H NMR spectra of 10-benzyl-9,11-diphenyl-10-azatetracyclo[6.3.0.0.(4,11)0.(5,9)]undecane (BnPh(2)()) and 10-methyl-9,11-diphenyl-10-azatetracyclo[6.3.0.0.(4,11)0.(5,9)]undecane (MePh(2)()) decoalesce due to slowing inversion at nitrogen and to slowing isolated bridgehead phenyl rotation. The high nitrogen inversion barriers in MePh(2)() (DeltaG() = 12.2 +/- 0.1 kcal/mol at 250 K) and BnPh(2)() (DeltaG() = 10.6 +/- 0.1 kcal/mol at 215 K) are typical of tertiary amines in which at least one C-N-C bond angle is constrained to a small value. Compared to the minuscule rotation barriers about sp(2)-sp(3) carbon-carbon bonds in simple molecular systems, the bridgehead phenyl rotation barriers in MePh(2)() (DeltaG() = 9.8 +/- 0.1 kcal/mol at 210 K) and BnPh(2)() (DeltaG() = 9.8 +/- 0.1 kcal/mol at 210 K) are unusually high. Molecular mechanics calculations (MMX force field) suggest that the origin of the high phenyl rotation barriers lies in the close passage of an o-phenyl proton and a methyl (or benzylmethylene) proton in the transition state. BnPh(2)() crystallized from hexane as white needles in the monoclinic system Pn. Unit cell dimensions are as follows: a = 12.198(1) ?, b = 6.1399(6) ?, c = 14.938(2) ?, beta = 107.470(4) degrees, V = 1067.1(2) ?(3), Z = 2. In the crystal molecular structure, the imine bridge CNC bond angle in BnPh(2)() is constrained to a small value (96 degrees ). The benzylic phenyl group is oriented gauche to the nitrogen lone pair. 相似文献
88.
89.
Alverson G Baker WF Ballocchi G Benson R Berg D Blusk S Bromberg C Brown D Carey D Chand T Chandlee C Choudhary BC Chung WH de Barbaro L DeSoi W Dlugosz W Dunlea J Easo S Engels E Faissler W Fanourakis G Ferbel T Garelick D Ginther G Glass G Glaubman M Gutierrez P Hartman K Huston J Johnstone C Kapoor V Kourbanis L Lanaro A Lirakis C Lobkowicz F Lukens P Mani S Maul A Mansour J Miller R Nelson CA Oh BY Orris D Pothier E Prebys E Rajaram BM Roser R Ruddick K Shepard P Shivpuri RK Sinanidis A 《Physical review D: Particles and fields》1993,48(1):5-28
90.
Abe F Albrow M Amidei D Anway-Wiese C Apollinari G Atac M Auchincloss P Azzi P Baden AR Bacchetta N Badgett W Bailey MW Bamberger A de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Beretvas A Berge JP Bertolucci S Biery K Bhadra S Binkley M Bisello D Blair R Blocker C Bodek A Bolognesi V Booth AW Boswell C Brandenburg G Brown D Buckley-Geer E Budd HS Busetto G Byon-Wagner A 《Physical review D: Particles and fields》1993,48(3):998-1008