全文获取类型
收费全文 | 1359篇 |
免费 | 31篇 |
国内免费 | 4篇 |
专业分类
化学 | 937篇 |
晶体学 | 6篇 |
力学 | 55篇 |
数学 | 166篇 |
物理学 | 230篇 |
出版年
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 15篇 |
2019年 | 18篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 23篇 |
2015年 | 26篇 |
2014年 | 30篇 |
2013年 | 62篇 |
2012年 | 81篇 |
2011年 | 80篇 |
2010年 | 47篇 |
2009年 | 42篇 |
2008年 | 64篇 |
2007年 | 65篇 |
2006年 | 64篇 |
2005年 | 60篇 |
2004年 | 66篇 |
2003年 | 35篇 |
2002年 | 47篇 |
2001年 | 25篇 |
2000年 | 19篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 18篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1990年 | 15篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1985年 | 17篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 7篇 |
1977年 | 24篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1972年 | 15篇 |
1971年 | 10篇 |
1967年 | 7篇 |
排序方式: 共有1394条查询结果,搜索用时 312 毫秒
81.
82.
Rigid macroporous copolymers of styrene and divinylbenzene have been designed for large-scale preparative and process-scale purification of synthetic peptides and recombinant proteins. The polymeric particles are mechanically stable and hence able to operate at the required high linear velocities. The pore size and pore morphology has been optimised to enable unhindered solute diffusion whilst providing maximum available surface area to enhance loading capacity. A 100 A pore size has been developed for synthetic peptides and a 300 A pore size for recombinant proteins. Precise control of particle size, within the range 10 to 20 microm, is possible which together with the very narrow particle size distribution enables maximum resolution/loading to be obtained within the pressure limits of the instrumentation being used. The chemical stability of the polymer enables cleaning in place with 1 M sodium hydroxide without particle dissolution or a deterioration in selectivity. These materials can be packed into compression hardware and are manufactured as single lots up to 100 kg (300 l) batch size. 相似文献
83.
Molecular electronics is, relatively speaking, a young field. Even so, there have been many significant advances and a much greater understanding of the types of materials that will be useful in molecular electronics, and their properties. The purpose of this review is to provide a broad basis for understanding the areas where new advances might arise, and to provide introduction to the subdisciplines of molecular electronics. This review is divided into two major parts; an historical examination of the development of conventional electronics, which should provide some understanding of the push towards molecular electronics. The problems associated with continuing to shrink conventional systems are presented, along with references to some of the efforts to solve them. This section is followed by an in-depth look at the most important research into the types of behaviors that molecular systems have been found to display. 相似文献
84.
Thermal grating and broadband degenerate four-wave mixing spectroscopy of OH in high-pressure flames
H. Latzel A. Dreizler T. Dreier J. Heinze M. Dillmann W. Stricker G.M. Lloyd P. Ewart 《Applied physics. B, Lasers and optics》1998,67(5):667-673
2 ∑–X2Π(0,0) band of OH has been studied in premixed methane/air flames using a cw Ar+ laser probe. Measurements of flame temperature and pressure were derived from fits of theoretical simulations to the observed
time variation of signals over a pressure range of 10 to 40 bar and for different stoichiometry that were in agreement with
independent measurements using N2 CARS and predictions of a one-dimensional flame calculation. Broadband DFWM spectra in the same band of OH were observed
up to a pressure of 9 bar, above which signals were obtained only from scattering from thermal gratings.
Received: 10 November 1997/Revised version: 28 May 1998 相似文献
85.
The asymptotic solution of the linear quadratic state regulator problem is obtained as the cost of the control tends to zero. Matrix Riccati gains are obtained via singular perturbations theory and are used to asymptotically calculate the optimal control and the corresponding trajectories. Several cases are distinguished and applications are discussed. 相似文献
86.
Using a triple plasma device, strong double layers (Δ 20 Te/e) have been produced in an axial magnetic field of 50 G. Numerical results indicate that suppression of plasma generation in the region of a double layer is necessary for its existence. 相似文献
87.
88.
Samuel G. Davis Lloyd A. Swanson 《The Journal of the Operational Research Society》1978,29(6):559-564
The reduction in bank float requires that cheque processing procedures be upgraded in order to reduce the elapsed time between the receipt of a cheque and its presentation for collection at the bank upon which it is drawn. Traditionally, attempts to reduce float have focussed on the procedures for receiving checks and processing steps in preparation for clearing. Although the transporting of cheques from receiving locations to the processing location would most likely be the most significant factor in the elapsed time between receipt and eventual presentation for clearance, the float implications has largely been ignored in the development of transportation schedules in commercial banks. In attempting to maximize cheques processed, the timing of branch pickups should be based upon branch volume available and proof and transit processing capacity as well as travel time considerations. A heuristic model described in this paper represents the first methodology providing the opportunity for simultaneously evaluating these variables to develop schedules which offer opportunities for improvements in bank funds flow. 相似文献
89.
90.
Robert E. Linder Günter Barth Edward Bunnenberg Carl Djerassi Lloyd Seamans Albert Moscowitz 《Chemical physics letters》1974,28(4):490-493
The MCD spectrum of formaldehyde in the vapor phase has been measured and analyzed. Triplet bands occur with unusually high ellipticity, allowing identification of several new singlet-triplet bands. Also, an additional singlet progression, based on two quanta of the out-of-plane band and a single quantum of the antisymmetric CH stretch, has been identified. 相似文献