全文获取类型
收费全文 | 73246篇 |
免费 | 12784篇 |
国内免费 | 7446篇 |
专业分类
化学 | 51086篇 |
晶体学 | 669篇 |
力学 | 4737篇 |
综合类 | 316篇 |
数学 | 8450篇 |
物理学 | 28218篇 |
出版年
2024年 | 174篇 |
2023年 | 1566篇 |
2022年 | 1956篇 |
2021年 | 2596篇 |
2020年 | 3120篇 |
2019年 | 2886篇 |
2018年 | 2525篇 |
2017年 | 2308篇 |
2016年 | 3522篇 |
2015年 | 3367篇 |
2014年 | 4034篇 |
2013年 | 5253篇 |
2012年 | 6712篇 |
2011年 | 6871篇 |
2010年 | 4553篇 |
2009年 | 4356篇 |
2008年 | 4692篇 |
2007年 | 4213篇 |
2006年 | 3855篇 |
2005年 | 3224篇 |
2004年 | 2490篇 |
2003年 | 1972篇 |
2002年 | 1805篇 |
2001年 | 1521篇 |
2000年 | 1403篇 |
1999年 | 1590篇 |
1998年 | 1333篇 |
1997年 | 1329篇 |
1996年 | 1331篇 |
1995年 | 1080篇 |
1994年 | 938篇 |
1993年 | 787篇 |
1992年 | 703篇 |
1991年 | 605篇 |
1990年 | 522篇 |
1989年 | 394篇 |
1988年 | 344篇 |
1987年 | 284篇 |
1986年 | 257篇 |
1985年 | 212篇 |
1984年 | 152篇 |
1983年 | 108篇 |
1982年 | 90篇 |
1981年 | 71篇 |
1980年 | 68篇 |
1979年 | 36篇 |
1978年 | 33篇 |
1977年 | 41篇 |
1976年 | 34篇 |
1973年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
991.
纳米CoHCF修饰电极的制备及其对血红蛋白的电化学测定研究 总被引:1,自引:0,他引:1
A cobalt hexacyanoferrate (CoHCF) nanoparticle (size ca. 60 nm) chemically modified electrode (CME) was fabricated and the electrochemical behavior of hemoglobin (Hb) at this nanosized CoHCF CME was studied. In comparison with a bare glassy carbon electrode (GCE) and a general CoHCF CME electrodeposited in a traditional manner, the present nanosized CoHCF CME performed efficiently electrocatalytic reduction for Hb with relatively high sensitivity, stability, and longlife, Combined with liquid chromatography (LC), the nanosized CoHCF CME was used as the electrochemical detector of Hb in the established flow injection analysis-electrochemical determination (FIA-ECD) system. The peak current was a linear function of concentrations in the range from 2.5×10^-8 to 5.0×10^-6mol/L for Hb, with detection limit of 1.4×10^-8 mol/L. The FIA-ECD system has been successfully applied to assess the Hb content of clinic blood samples with advantages of sensitiveness, speediness, easy control and small sample-consumption. 相似文献
992.
B. Hlavőček J. Šestők L. Koudelka P. Mošner J. J. Mareš 《Journal of Thermal Analysis and Calorimetry》2005,80(2):271-283
Summary The forms of vibrations and displacements of particles in amorphous structures have been investigated. The particles, moving on highly non-linear amplitude, are responsible for the creation of disordered structures of amorphous bodies. The non-linear oscillators, even if 'few' in concentration, are characterized by unpredictable trajectories in phase space. The non-linear oscillators are fully developed in the liquid state above the crossover temperature Tcr and between Tcr and Tg their number decreases. Under Tg they completely disappear. The interconnection between the linear oscillators in blocks plays the most important role in the characteristic time spectra in liquid state. Using the additive properties of elements polarizibilities, the number of acoustical units in individual blocks at Tcr is estimated to be about 600 units. The diameter of blocks at Tcr was estimated to be about 1.8 nm. Even if the non-linear high amplitude motions disappear at solidification, the remnants of structural irregularity remain and the disordered structure of glass is formed. 相似文献
993.
本文描述了一个倾斜交叉、差分式激光热透镜光谱法。采用本方法可消除较高的溶剂空白的影响。文章讨论了调制频率和泵浦光功率对热透镜信号的影响,给出了检测Cu~(2+)的工作曲线,讨论了影响方法灵敏度的诸因素,提出了可能的改进方案。 相似文献
994.
A complete assignment of the 1H, 13C and 19F NMR spectra of 1,1,4,4-tetrafluoro-2-propylidene-3-methyl-6-tert-butyl-1,4-disila-5-cyclohexene 3, the product of the cycloaddition reaction between tetrafluorodisilacyclobutene 1 and cis, trans-2,4-hexadiene mediated by (n5-C5H5)Mn(CO)3, has been made by means of various 2D NMR chemical shift correlation methods and selective heteronuclear decoupling techniques. An analysis of the three bond 13C-1H coupling constants and two bond 13C-19F coupling constants and the molecular modeling results enabled the determination of the conformation and configuration of compound 3. The conformation of 3 provides insight into mechanistic details of the Mn-mediated cycloaddition. 相似文献
995.
The dependence of the frequency factor on the temperature (A=A
0
T
m) has been examined and the errors involved in the activation energy calculated from some integral methods without considering
such dependence have been estimated. Investigated integral methods are the Coats-Redfern method, the Gorbachev-Lee-Beck method,
the Wanjun-Yuwen method and the Junmeng-Fusheng method. The results have shown that the error in the determination of the
activation energy calculated ignoring the dependence of the frequency factor on the temperature can be rather large and it
is dependent on x=E/RT and the exponent m. 相似文献
996.
IntroductionIthasbccndcmonstratcdthatmcthancrcformingt"ithcarbondioxidcpr0ducessynthcsisgasrichincarbonmonoxidc-x"hichisuscfulforthcs}nthcsisofaccticacid'dimcthylcthcrando.o-alcoholsll'2].Carbondioxidcref0rmingismorccndothcrmicthanstcamrcformingfCH4 CO2,'2CO 2H2Ai/'2,,=2473kJ..ol-1(l)Accordingl\"thisrcact1onnccdshighcrtcmpcraturcandlimitsspaccvclocityoffccdgas,Wehavcprct'ious1\studicdmcthancrcformingt"lthC02inthcmonotubcproccssl3J.Inordertoconvcrtmcthancinfccdgascomplctcl}',thcspaccvcloci… 相似文献
997.
研究了熔盐被覆铬碳化物的工艺过程,着重探讨了稀土对T12A钢熔盐渗铬的催渗及微合金化作用机理。结果表明,在加入稀土的熔盐中渗中提高渗速30%-56%,同时还能提高工件表面的抗氧化和耐腐蚀性能以及工件的使用寿命。 相似文献
998.
Zhengbin Zhang Liansheng Liu Hongbin Zhao Youjun Fu Fengyun Cheng Weihong Zhao 《中国科学B辑(英文版)》1997,40(4):353-364
A new method for the study of ternary surface complexes at liquid-solid interface, theE(%) -pH curve method, was proposed. Four types ofE(%)-pH curves, namely, phenomenon of left-right shifts of S-shaped curve, V-shaped curve, monodirection shift curve and X-shaped
curve, were discovered. Correspondingly, apart from type (I) ternary surface complex
and type (II) ternary surface complex
, a new type of ternary surface complex
was discovered.
Project supported by the National Natural Science Foundation of China and the Fund of Doctoral Degree’s Spot. 相似文献
999.
Small gold nanoparticles can mimic dehydrogenase activity to catalyze estradiol (E2) oxidation to estrone (E1), extending the range of nanozyme catalysis to environmentally and biologically important substrates. 相似文献
1000.
A novel mode of affinity chromatography (AC) based on an open tubular capillary column (OTAC) is demonstrated. The OTAC column is prepared by immobilizing Cibacron blue F3GA onto the inner surface of a 50-microm-i.d. capillary column. The AC experiment is performed on a capillary electrophoresis instrument by using its pressure system as the driving force. Bovine serum albumin and lysozyme (Lys) are successfully separated with stepwise gradient elution. The relative standard deviation (RSD) for the elution time of the retained Lys is 0.08%, and good repeatability of its peak area and peak height with an RSD value lower than 2.12% for 10 consecutive runs is observed. The loading capacity and detection limit for the retained Lys are approximately 36 ng and 8.6 ng, respectively. It is also found that the amount of protein adsorbed is unaffected by the flow rate of the loading buffer, and OTAC can be used for the fast determination of biopolymers. Some of the advantages of OTAC over conventional modes of open tubular capillary liquid chromatography are that the detection sensitivity and loading capacity of a sample can be greatly improved, because the relatively large inner diameter of the capillary can be adopted and the whole capillary column can be used to adsorb the solute in OTAC. 相似文献