全文获取类型
收费全文 | 5916篇 |
免费 | 194篇 |
国内免费 | 37篇 |
专业分类
化学 | 3714篇 |
晶体学 | 18篇 |
力学 | 301篇 |
数学 | 943篇 |
物理学 | 1171篇 |
出版年
2023年 | 48篇 |
2022年 | 48篇 |
2021年 | 167篇 |
2020年 | 143篇 |
2019年 | 117篇 |
2018年 | 113篇 |
2017年 | 105篇 |
2016年 | 230篇 |
2015年 | 175篇 |
2014年 | 178篇 |
2013年 | 322篇 |
2012年 | 308篇 |
2011年 | 364篇 |
2010年 | 233篇 |
2009年 | 194篇 |
2008年 | 346篇 |
2007年 | 326篇 |
2006年 | 296篇 |
2005年 | 303篇 |
2004年 | 215篇 |
2003年 | 223篇 |
2002年 | 164篇 |
2001年 | 98篇 |
2000年 | 97篇 |
1999年 | 87篇 |
1998年 | 49篇 |
1997年 | 45篇 |
1996年 | 65篇 |
1995年 | 58篇 |
1994年 | 58篇 |
1993年 | 59篇 |
1992年 | 42篇 |
1991年 | 44篇 |
1990年 | 36篇 |
1989年 | 46篇 |
1988年 | 36篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 57篇 |
1984年 | 56篇 |
1983年 | 30篇 |
1982年 | 33篇 |
1981年 | 33篇 |
1980年 | 38篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 35篇 |
1976年 | 24篇 |
1975年 | 25篇 |
1974年 | 23篇 |
排序方式: 共有6147条查询结果,搜索用时 265 毫秒
1.
Journal of Optimization Theory and Applications - Pollution management models of Shallow Lake type identify a well-known class of infinite horizon optimal control problems, characterized by the... 相似文献
2.
3.
Numerical Algorithms - We introduce a modulus-based formulation for vertical linear complementarity problems (VLCPs) with an arbitrary number ? of matrices. This formulation can be used to... 相似文献
4.
Francesco Segatta David M. Rogers Naomi T. Dyer Ellen E. Guest Zhuo Li Hainam Do Artur Nenov Marco Garavelli Jonathan D. Hirst 《Molecules (Basel, Switzerland)》2021,26(2)
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains. 相似文献
5.
Vito Gigante Laura Aliotta Maria Beatrice Coltelli Patrizia Cinelli Luigi Botta Francesco Paolo La Mantia Andrea Lazzeri 《Journal of polymer science. Part A, Polymer chemistry》2020,58(23):3264-3282
The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheological perspective. An optimized PLA/PBAT ratio was chosen as the polymeric basis to obtain a biodegradable formulation by adding a biobased plasticizer and appropriate fillers to produce a micrometer film with tailored flexibility and tear resistance. The processing technology involved flat-die extrusion, followed by calendering. The tearing resistance of the produced film was investigated, and the results were compared with literature data. A study on the essential work of fracture was implemented to explore the mode III out-of-plane fracture resistance starting from a trouser tear test. 相似文献
6.
7.
Let Ψ(x,y) (resp. Ψm(x,y)) denote the number of integers not exceeding x that are y-friable, i.e. have no prime factor exceeding y (resp. and are coprime to m). Evaluating the ratio Ψm(x/d,y)/Ψ(x,y) for 1≤slantd≤slantx, m≥slant 1, x≥slant y≥slant 2, turns out to be a crucial step for estimating arithmetic sums over friable integers. Here, it is crucial to obtain formulae with a very wide range of validity. In this paper, several uniform estimates are provided for the aforementioned ratio, which supersede all previously known results. Applications are given to averages of various arithmetic functions over friable integers which in turn improve corresponding results from the literature. The technique employed rests mainly on the saddle-point method, which is an efficient and specific tool for the required design.2000 Mathematics Subject Classification: Primary—11N25; Secondary—11K65, 11N37 相似文献
8.
Journal d'Analyse Mathématique - 相似文献
9.
W M Niessen M A de Kraa E R Verheij P J Bergers G F La Vos U R Tjaden J van der Greef 《Rapid communications in mass spectrometry : RCM》1989,3(1):1-4
On-line sample pretreatment by means of the phase-system switching approach is an interesting technique for the analysis of aqueous samples, e.g., plasma, by means of supercritical-fluid chromatography. In order to analyse plasma samples the following analytical procedure is used. The plasma sample is injected on to a short precolumn, which is washed with water and subsequently dried with nitrogen. Next, the solutes are desorbed with the supercritical mobile phase, analysed with packed-column supercritical-fluid chromatography and detected with either a UV detector or a mass spectrometer, equipped with a moving-belt interface. The herbicide diuron is selected as a test compound to study the feasibility of this approach. Using a selective detector the procedure is sufficiently sensitive to detect diuron in plasma, but not appropriate to detect the diuron metabolites in a post-mortem plasma sample. These have been identified with liquid chromatography/mass spectrometry. The detection limit of diuron in plasma using the procedure described is about 30 ng/mL. 相似文献
10.
The concept of strong interactions need not be limited to the sector of physics taken by QCD. While this domain is investigated by RHIC, LHC will be able to probe potential new strong interactions simultaneously: Finding the precise mechanism for electroweak symmetry breaking is one of the prime problems of physics. Intricately linked to this point is the question after the true nature or even the existence of the Higgs boson. Here, we present stronly interacting theories providing an explanation for the hierarchy problem and leading to a light composite Higgs boson, favoured by experimental data. Our variation of the standard model is consistent with precision data. We achieve this accordance by using technifermions in a higher representation of their gauge group. Anomaly conditions require at least one extra lepton family for some of the theories whereby they contain a natural dark matter candidate. We can accurately determine the masses of said leptons from experimental data. 相似文献