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991.
We used micropipette aspiration of giant unilamellar vesicles to directly measure the areal expansion of gel (Lβ′) phase 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers induced by exposure to ethanol/water mixtures. Areal expansion began in 7 vol% ethanol and increased monotonically as the concentration of ethanol was increased to 15 vol% at which point areal expansion reached a plateau of 50%. This ethanol concentration range is in good agreement with that of the interdigitated phase (LβI) of DPPC, therefore, we believe that this is the first direct measurement of the areal expansion accompanying interdigitation of gel-phase lipids. Our observations are consistent with the presence of coexisting LβI and Lβ′ phases in ethanol concentrations between 7% and 15 vol% and 100% LβI phase in 15 vol% ethanol and higher. We observed a bimodal distribution of areal expansion (0% and 20%) induced by 7 vol% ethanol indicating that at the threshold concentration, interdigitation is induced in only a portion of DPPC vesicles. Areal expansion could not be easily reversed, consistent with kinetic trapping of the LβI phase. DPPC vesicles exposed to butanol at the known threshold and plateau concentrations for the LβI phase displayed areal expansion behavior consistent with our ethanol observations. However, the area expanded significantly faster for DPPC bilayers exposed to butanol vs. ethanol, which we attribute to enhanced partitioning of the longer-chained butanol into the lipid headgroups. Ethanol-induced areal expansion of DPPC bilayers was inhibited by inclusion of 10 mol% and 25 mol% cholesterol in the bilayer. However, areal expansion could be induced by application of tensions (∼8 mN/m) similar to the phenomena of interdigitation induced by high pressure. The presence of 20 vol% ethanol significantly decreased surface cohesion of DPPC bilayers containing 25 mol% cholesterol as evidenced by a decreased area compressibility modulus and lysis tension. 相似文献
992.
1 Inttoductlon and Preliminary KnowledgeThe generalized inverse is an important tool for researching the singular matrix problems,ac-POSed problems, optimication and statistics problems. The inverse order rule for generalizedinverse playS an forportant role on the theoretical research and numerical computations in theOf generaled inverse is(see [2) [6][8j). Another sufficient and neceSSary condition isIn this paper we generalize the above resultS to the case of the weighted generalized inv… 相似文献
993.
K. Yu. Nagulin A. Kh. Gil’mutdinov O. R. Badrutdinov 《Journal of Applied Spectroscopy》2000,67(1):14-21
The spatial distribution of the intensity of radiation from high-frequency electrodeless discharge lamps of LV-2 and VSB-2
types, used as radiation sources in atomic absorption spectrometry, was investigated. Radiation intensity distributions over
the cross section of the lamps were measured on the atomic and ionic lines of a buffer gas and a filler element. It is shown
that in a lamp filled with buffer gas only the distribution of the intensity of atomic and ionic lines is dome-shaped, and
that it is determined by the electron density distribution in the plasma as well as by the mechanism of excitation and ionization
of the buffer gas. The distribution of the intensity of radiation from the filler element is strongly nonuniform, with a maximum
that is concentric with the bulb walls and a minimum on the lamp axis. The observed spatial intensity distributions are explained
by the redistribution of filler-element atoms over the volume of the lamp under the conditions of high electron concentrations.
The time dynamics of the spatial intensity distributions during warm-up of the lamps was investigated. It is shown that the
process of establishment of stationary distributions goes on nonmonotonically, which is due to the redistribution of energy
among different components of the discharge plasma.
Translated from Zhurnal Prikladnoi Spektroskopi, Vol. 67, No. 1, pp. 15–20, January–February, 2000. 相似文献
994.
We have performed atomistic Grand Canonical Monte-Carlo (GCMC) simulations of adsorption of xenon in a Vycor-like matrix at 195 K. The disordered mesoporous network is obtained by applying a numerical 3D off-lattice reconstruction procedure to a simulation box originally containing silicon and oxygen atoms of a non-porous silica solid. In order to reduce the computational cost, we have applied a homothetic decrease of the simulation box dimensions which preserves the morphology and the topology of the pore network (the average pore dimension is then around 30 Å). The surface chemistry is obtained in a realistic fashion by saturating all dangling bonds with hydrogen atoms. Small angle scattering spectra calculated on different numerical samples have evidenced a departure from Porod's law due to surface roughness. The simulated isotherms calculated on such disordered connected porous networks, show the capillary condensation phenomenon. The shape of the adsorption curves differs from that obtained for simple pore geometries. The analysis of the adsorbed quantity distribution indicates partial molecular-film formation depending on the local surface curvature and roughness. 相似文献
995.
土壤淋溶柱色谱中有机调节剂对保留的影响 总被引:1,自引:0,他引:1
摘要:系统考察了55种非离子型化合物(包括11个氯代苯类、14个烷基苯类、22个多苯和多环芳烃类化合物、8个农药)在土壤淋溶柱色谱和较宽的淋洗剂(甲醇-水)组成范围内容量因子(k')与甲醇体积分数(ψ)的关系。用自制加压装柱机将标准土壤干法装填成10mmi.d.×100mm的液相色谱柱,ψ=00.80的等度淋洗剂的流速1mL·min-1,柱温(25.0±0.1)℃,用UV检测器在线检测。实验表明,logk'=logkw+aψ+bψ2和logk'=logkw-Sψ两式均可以用来描述保留规律,但后者因其计算简 相似文献
996.
基于移动Agent的分布式网管系统设计与实现 总被引:3,自引:0,他引:3
提出了一种运用移动Agent技术实现分布式网管的方案,它结合了Java和coRBA等分布式计算技术,并采用基于规则的方法来实现对网络的智能化管理.文中首先研究了基于移动Agent的分布式网管结构,然后深入地讨论了它的系统实现,包括移动Agent的运行环境、结构设计、通信机制以及基于Web的图形用户界面. 相似文献
997.
Core quantum postulates including the superposition principle and the unitarity of evolutions are natural and strikingly simple. I show that—when supplemented with a limited version of predictability (captured in the textbook accounts by the repeatability postulate)—these core postulates can account for all the symptoms of classicality. In particular, both objective classical reality and elusive information about reality arise, via quantum Darwinism, from the quantum substrate. This approach shares with the Relative State Interpretation of Everett the view that collapse of the wavepacket reflects perception of the state of the rest of the Universe relative to the state of observer’s records. However, our “let quantum be quantum” approach poses questions absent in Bohr’s Copenhagen Interpretation that relied on the preexisting classical domain. Thus, one is now forced to seek preferred, predictable, hence effectively classical but ultimately quantum states that allow observers keep reliable records. Without such (i) preferred basis relative states are simply “too relative”, and the ensuing basis ambiguity makes it difficult to identify events (e.g., measurement outcomes). Moreover, universal validity of quantum theory raises the issue of (ii) the origin of Born’s rule, , relating probabilities and amplitudes (that is simply postulated in textbooks). Last not least, even preferred pointer states (defined by einselection—environment—induced superselection)—are still quantum. Therefore, unlike classical states that exist objectively, quantum states of an individual system cannot be found out by an initially ignorant observer through direct measurement without being disrupted. So, to complete the ‘quantum theory of the classical’ one must identify (iii) quantum origin of objective existence and explain how the information about objectively existing states can appear to be essentially inconsequential for them (as it does for states in Newtonian physics) and yet matter in other settings (e.g., thermodynamics). I show how the mathematical structure of quantum theory supplemented by the only uncontroversial measurement postulate (that demands immediate repeatability—hence, predictability) leads to preferred states. These (i) pointer states correspond to measurement outcomes. Their stability is a prerequisite for objective existence of effectively classical states and for events such as quantum jumps. Events at hand, one can now enquire about their probability—the probability of a pointer state (or of a measurement record). I show that the symmetry of entangled states—(ii) entanglement—assisted invariance or envariance—implies Born’s rule. Envariance also accounts for the loss of phase coherence between pointer states. Thus, decoherence can be traced to symmetries of entanglement and understood without its usual tool—reduced density matrices. A simple and manifestly noncircular derivation of follows. Monitoring of the system by its environment in course of decoherence typically leaves behind multiple copies of its pointer states in the environment. Only pointer states can survive decoherence and can spawn such plentiful information-theoretic progeny. This (iii) quantum Darwinism allows observers to use environment as a witness—to find out pointer states indirectly, leaving systems of interest untouched. Quantum Darwinism shows how epistemic and ontic (coexisting in epiontic quantum state) separate into robust objective existence of pointer states and detached information about them, giving rise to extantons—composite objects with system of interest in the core and multiple records of its pointer states in the halo comprising of environment subsystems (e.g., photons) which disseminates that information throughout the Universe. 相似文献
998.
We have investigated the influence of the average degree
\langle k \rangle of network on the location of an order--disorder
transition in opinion dynamics. For this purpose, a variant of
majority rule (VMR) model is applied to Watts--Strogatz (WS)
small-world networks and Barab\'{a}si--Albert (BA) scale-free
networks which may describe some non-trivial properties of social
systems. Using Monte Carlo simulations, we find that the
order--disorder transition point of the VMR model is greatly
affected by the average degree \langle k \rangle of the networks;
a larger value of \langle k \rangle results in a more ordered state of
the system. Comparing WS networks with BA networks, we find WS
networks have better orderliness than BA networks when the average
degree \langle k \rangle is small. With the increase of \langle k
\rangle, BA networks have a more ordered state. By implementing
finite-size scaling analysis, we also obtain critical exponents
\beta/\nu, \gamma/\nu and 1/\nu for several values of average
degree \langle k \rangle. Our results may be helpful to understand
structural effects on order--disorder phase transition in the
context of the majority rule model. 相似文献
999.
A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections (TCSs) for electrons scattering from several molecules (CF4, CCl4, CFCl3, CF2 Cl2, and CF3 Cl) over an incident energy range 30 ~ 5000 eV using the additivity rule model at Hartree-Fock level. The quantitative TCSs are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV.It is shown that the modified potential can successfully calculate the TCSs of electron-molecule scattering over a wide energy range, especially at lower energies. 相似文献
1000.