全文获取类型
收费全文 | 367267篇 |
免费 | 2747篇 |
国内免费 | 861篇 |
专业分类
化学 | 195056篇 |
晶体学 | 5793篇 |
力学 | 16924篇 |
综合类 | 11篇 |
数学 | 39074篇 |
物理学 | 114017篇 |
出版年
2018年 | 4625篇 |
2017年 | 4662篇 |
2016年 | 6383篇 |
2015年 | 3563篇 |
2014年 | 5982篇 |
2013年 | 14635篇 |
2012年 | 10718篇 |
2011年 | 13033篇 |
2010年 | 9822篇 |
2009年 | 9853篇 |
2008年 | 12128篇 |
2007年 | 12170篇 |
2006年 | 11274篇 |
2005年 | 10097篇 |
2004年 | 9521篇 |
2003年 | 8555篇 |
2002年 | 8627篇 |
2001年 | 10342篇 |
2000年 | 7834篇 |
1999年 | 6124篇 |
1998年 | 5194篇 |
1997年 | 5061篇 |
1996年 | 4866篇 |
1995年 | 4454篇 |
1994年 | 4328篇 |
1993年 | 4243篇 |
1992年 | 4708篇 |
1991年 | 4890篇 |
1990年 | 4816篇 |
1989年 | 4889篇 |
1988年 | 4725篇 |
1987年 | 4764篇 |
1986年 | 4398篇 |
1985年 | 5763篇 |
1984年 | 5806篇 |
1983年 | 4925篇 |
1982年 | 5161篇 |
1981年 | 5012篇 |
1980年 | 4722篇 |
1979年 | 5166篇 |
1978年 | 5569篇 |
1977年 | 5501篇 |
1976年 | 5512篇 |
1975年 | 5176篇 |
1974年 | 5094篇 |
1973年 | 5270篇 |
1972年 | 3872篇 |
1971年 | 3397篇 |
1968年 | 3552篇 |
1967年 | 3728篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
O. I. Reinov 《Journal of Mathematical Sciences》2003,115(2):2243-2250
We investigate Banach spaces possessing (or not possessing) the approximation properties AP s, 0 < s ≤ 1, in connection with the following known question in the geometric theory of operators: under which conditions on Banach spaces X and Y and on positive numbers r and p does the p-nuclearity of the second adjoint of a continuous operator T from X to Y imply the p-nuclearity of T? Actually, we give necessary and sufficient conditions under which this question is answered affirmatively. In addition, the corresponding counterexamples are obtained in the maximally strong form. For instance, it is shown (and this statement is a significant strengthening of the previous results of that sort) that there exists a pair of separable Banach spaces Z and W such that the spaces Z ** and W have Schauder bases, while for every p, 1 ≤ p < 2, there is a non-p-nuclear operator from W to Z with a p-nuclear second adjoint. Earlier, in similar examples, the corresponding spaces did not possess even the Grothendieck approximation property. The technique developed in this paper does not allow us to treat the case p > 2. That case will be studied in a forthcoming paper of the author. Bibliography: 11 titles. 相似文献
112.
We prove new theorems on the justification of the averaging method for multifrequency oscillation systems with pulse influence at fixed times. 相似文献
113.
We prove that the sufficient conditions for the asymptotic stability of impulsive systems obtained by Gurgula and Perestyuk are also necessary conditions. 相似文献
114.
P L Melgarejo M Ternero I Gracia 《International journal of environmental analytical chemistry》1986,24(4):283-295
A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels. 相似文献
115.
A simple procedure for the synthesis of an important standard, isotopically enriched methylmercury, which is not commercially available, has been established successfully. The isotopically enriched standard synthesized is utilized in conventional isotope dilution mass spectrometry (IDMS), as well as in speciated IDMS (SIDMS), for determination of the true concentration of methylmercury in environmental samples. The CH3201Hg+ standard has been synthesized from commercially available 201HgO and tetramethyltin. The synthesis time required is 1 h at 60°C. The product is highly pure, yielding more than 90% as 201Hg in CH3201Hg+. Hazardous dimethylmercury does not occur during this synthesis procedure. The product synthesized was analyzed using high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP‐MS) and ICP‐MS alone in order to determine its concentration, isotopic composition and purity. The stability of the product was also evaluated for over 6 months and found to be stable at 4°C in the dark. The isotopically enriched methylmercury synthesized can be used in SIDMS and IDMS analyses as a standard. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
116.
117.
I. L. Bataronov A. M. Roshchupkin 《Journal of Applied Mechanics and Technical Physics》1991,32(2):259-265
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 127–134, March–April, 1991. 相似文献
118.
H. -Q. Liu 《manuscripta mathematica》1995,87(1):159-166
This article was processed by the author using the IATEX style filecljourl from Springer-Verlag. 相似文献
119.
Nikulin S. S. Akatova I. N. Kondrat'eva N. A. 《Russian Journal of Applied Chemistry》2003,76(4):652-655
The influence of the charge of a metal cation and the nature of a coagulant on the recovery of butadiene-styrene rubber and properties of rubber stocks and vulcanizates was examined. 相似文献
120.
Numerical studies were conducted to investigate the natural convection heat transfer around a uniformly heated thin plate
with arbitrary inclination in an infinite space. The numerical approach was based on the finite volume technique with a nonstaggered
grid arrangement. For handling the pressure–velocity coupling the SIMPLE-algorithm was used. QUICK scheme and first order
upwind scheme were employed for discretization of the momentum and energy convective terms respectively. Plate width and heating
rate were used to vary the modified Rayleigh number over the range of 4.8×106 to 1.87×108. Local and average heat transfer characteristics were compared with regarding to the inclination angle. The empirical expressions
for local and average Nusselt number were correlated. It has been found that for inclination angle less than 10∘, the flow and heat transfer characteristics are complicated and the average Nusselt number can not be correlated by one equation
while for inclination angle larger than 10∘, the average Nusselt number can be correlated into an elegant correlation.
Received on 18 April 2001 / Published online: 29 November 2001 相似文献