全文获取类型
收费全文 | 6180篇 |
免费 | 55篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 42篇 |
综合类 | 2篇 |
化学工业 | 360篇 |
金属工艺 | 40篇 |
机械仪表 | 49篇 |
建筑科学 | 82篇 |
矿业工程 | 6篇 |
能源动力 | 68篇 |
轻工业 | 260篇 |
水利工程 | 10篇 |
石油天然气 | 25篇 |
无线电 | 230篇 |
一般工业技术 | 328篇 |
冶金工业 | 4538篇 |
原子能技术 | 15篇 |
自动化技术 | 182篇 |
出版年
2022年 | 19篇 |
2021年 | 24篇 |
2020年 | 27篇 |
2019年 | 31篇 |
2018年 | 29篇 |
2017年 | 35篇 |
2016年 | 41篇 |
2015年 | 19篇 |
2014年 | 31篇 |
2013年 | 82篇 |
2012年 | 67篇 |
2011年 | 93篇 |
2010年 | 57篇 |
2009年 | 71篇 |
2008年 | 72篇 |
2007年 | 62篇 |
2006年 | 45篇 |
2005年 | 49篇 |
2004年 | 63篇 |
2003年 | 60篇 |
2002年 | 37篇 |
2001年 | 32篇 |
2000年 | 43篇 |
1999年 | 165篇 |
1998年 | 1351篇 |
1997年 | 824篇 |
1996年 | 529篇 |
1995年 | 291篇 |
1994年 | 272篇 |
1993年 | 272篇 |
1992年 | 40篇 |
1991年 | 76篇 |
1990年 | 60篇 |
1989年 | 67篇 |
1988年 | 65篇 |
1987年 | 62篇 |
1986年 | 77篇 |
1985年 | 65篇 |
1984年 | 32篇 |
1983年 | 35篇 |
1982年 | 52篇 |
1981年 | 58篇 |
1980年 | 73篇 |
1979年 | 30篇 |
1978年 | 35篇 |
1977年 | 153篇 |
1976年 | 314篇 |
1975年 | 19篇 |
1974年 | 19篇 |
1973年 | 14篇 |
排序方式: 共有6237条查询结果,搜索用时 8 毫秒
1.
A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid
meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising
the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model
is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated
by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation.
The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest.
Sponsored by The Research Council of Norway, project number 125676/410
Dedicated to the memory of Prof. Mike Crisfield, a respected colleague 相似文献
2.
Decreasing carboxyl retention in deposits from the glow region of an acrylic acid plasma was measured by X-ray photoelectron spectroscopy and chemical derivatisation as the collection distance from the monomer vapour inlet was increased. Volatilisation of plasma polymerised acrylic acid was detected after trifluoroethanol derivatisation; this is correlated with evaporation of low molecular weight components observed previously. 相似文献
3.
4.
JF Favarel-Garrigues F Sztark ME Petitjean M Thico?pé P Lassié P Dabadie 《Canadian Metallurgical Quarterly》1996,82(2):312-316
Protective immunity against infection with Mycobacterium tuberculosis is imparted by T cells rather than antibodies, but B cells can play a role as antigen-presenting cells and in granuloma formation. We re-evaluated the role of B cells in the course of tuberculous infection in mu-chain knock-out (Ig-) mice. Surprisingly, the organs of M. tuberculosis-infected Ig- mice were found to have three- to eight-fold elevated counts of viable bacilli compared with normal littermates at 3-6 weeks post-infection. Splenic interferon-gamma responses to whole antigen were unimpaired, whilst proliferation to certain mycobacterial peptides was found to be diminished. However, bacille Calmette-Guérin (BCG) vaccination significantly reduced the infection in Ig- mice. The mechanisms by which B cells can influence primary tuberculous infection need further study. 相似文献
5.
SG Rijpkema RG Herbes N Verbeek-De Kruif JF Schellekens 《Canadian Metallurgical Quarterly》1996,117(3):563-566
Epiglottic disruption is an uncommon injury usually associated with significant supraglottic trauma. This injury may be overlooked because of the difficulty in examining the larynx or other associated severe injuries. We present two cases of clinically unsuspected epiglottic disruption that were first seen on MR images of the neck. 相似文献
6.
BS Kendrick BS Chang T Arakawa B Peterson TW Randolph MC Manning JF Carpenter 《Canadian Metallurgical Quarterly》1997,94(22):11917-11922
Understanding the mechanism for sucrose-induced protein stabilization is important in many diverse fields, ranging from biochemistry and environmental physiology to pharmaceutical science. Timasheff and Lee [Lee, J. C. & Timasheff, S. N. (1981) J. Biol. Chem. 256, 7193-7201] have established that thermodynamic stabilization of proteins by sucrose is due to preferential exclusion of the sugar from the protein's surface, which increases protein chemical potential. The current study measures the preferential exclusion of 1 M sucrose from a protein drug, recombinant interleukin 1 receptor antagonist (rhIL-1ra). It is proposed that the degree of preferential exclusion and increase in chemical potential are directly proportional to the protein surface area and that, hence, the system will favor the protein state with the smallest surface area. This mechanism explains the observed sucrose-induced restriction of rhIL-1ra conformational fluctuations, which were studied by hydrogen-deuterium exchange and cysteine reactivity measurements. Furthermore, infrared spectroscopy of rhlL-1ra suggested that a more ordered native conformation is induced by sucrose. Electron paramagnetic resonance spectroscopy demonstrated that in the presence of sucrose, spin-labeled cysteine 116 becomes more buried in the protein's interior and that the hydrodynamic diameter of the protein is reduced. The preferential exclusion of sucrose from the protein and the resulting shift in the equilibrium between protein states toward the most compact conformation account for sucrose-induced effects on rhIL-1ra. 相似文献
7.
8.
9.
Existence conditions are given for maximum likelihood (ML) parameter estimates for several families of 2-parameter software-reliability Poisson-process models. For each such model, the ML equations can be expressed in terms of one equation in one unknown. Bounds are given on solutions to these one equation problems to serve as initial intervals for search algorithms like bisection. Uniqueness of the solutions is established in some cases. Solutions are also tabulated for certain simple cases. Results are given for ungrouped failure data (exact times are available for all failures). ML estimation problems for such a situation are treated as limiting cases of problems based on failure times grouped into intervals of decreasing mesh 相似文献
10.
Tracheobronchial stent insertion is a relatively new technique used to palliate or cure central airways obstruction. When performed by experienced thoracic endoscopists, this procedure is both safe and effective, even if complications of indwelling stents may require repeat endoscopic intervention. Although proven clinically beneficial to many patients, airway prostheses have not yet been the subject of large comparative case studies or randomized controlled investigations. Reports are often experiential and anecdotal. Further research is needed to determine the effects of stenting on survival in patients with malignant airway disease and its degree of success in patients with benign airway strictures. Only then will airway stents truly deserve their place alongside other therapies for tracheobronchial obstruction. 相似文献