全文获取类型
收费全文 | 33088篇 |
免费 | 871篇 |
国内免费 | 64篇 |
专业分类
电工技术 | 368篇 |
综合类 | 35篇 |
化学工业 | 6790篇 |
金属工艺 | 858篇 |
机械仪表 | 623篇 |
建筑科学 | 1841篇 |
矿业工程 | 247篇 |
能源动力 | 1016篇 |
轻工业 | 2762篇 |
水利工程 | 337篇 |
石油天然气 | 207篇 |
武器工业 | 2篇 |
无线电 | 2150篇 |
一般工业技术 | 5204篇 |
冶金工业 | 6642篇 |
原子能技术 | 323篇 |
自动化技术 | 4618篇 |
出版年
2022年 | 196篇 |
2021年 | 386篇 |
2020年 | 335篇 |
2019年 | 399篇 |
2018年 | 488篇 |
2017年 | 509篇 |
2016年 | 522篇 |
2015年 | 463篇 |
2014年 | 736篇 |
2013年 | 2132篇 |
2012年 | 1241篇 |
2011年 | 1590篇 |
2010年 | 1169篇 |
2009年 | 1258篇 |
2008年 | 1436篇 |
2007年 | 1466篇 |
2006年 | 1256篇 |
2005年 | 1172篇 |
2004年 | 1052篇 |
2003年 | 1023篇 |
2002年 | 1031篇 |
2001年 | 634篇 |
2000年 | 615篇 |
1999年 | 575篇 |
1998年 | 600篇 |
1997年 | 499篇 |
1996年 | 604篇 |
1995年 | 546篇 |
1994年 | 532篇 |
1993年 | 534篇 |
1992年 | 486篇 |
1991年 | 321篇 |
1990年 | 438篇 |
1989年 | 424篇 |
1988年 | 379篇 |
1987年 | 425篇 |
1986年 | 382篇 |
1985年 | 515篇 |
1984年 | 491篇 |
1983年 | 443篇 |
1982年 | 464篇 |
1981年 | 445篇 |
1980年 | 353篇 |
1979年 | 365篇 |
1978年 | 329篇 |
1977年 | 307篇 |
1976年 | 268篇 |
1975年 | 318篇 |
1974年 | 243篇 |
1973年 | 279篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
41.
Joseph c. Richmond John B. Peterson Winslow H. Herschel 《Journal of the American Ceramic Society》1943,26(4):127-131
A volumcnometer of improved design has been developed for measuring the solid volumes of specimens varying in size up to that of standard refractory bricks. The chief feature of the new design is the use of a closed-cistern, altitude-type mercurial barometer to replace the simple manometer previously used. The barometer is de signed for use in a constant temperature room (21.1°C.) where the acceleration of gravity is 980.1 cm. per sec.2. Under these conditions, pressure readings are auto matically corrected to standard conditions. A vernier permits rapid readings to 0.1 mm. of mercury. 相似文献
42.
A black glass was made by melting a soda-lime-silica glass under a reducing atmosphere with the addition of 0.6% of selenium and 0.1% of cobalt carbonate, CoCOs. The light absorption of a specimen about 0.01 inch thick in the range of 400 to 750 mp was superior to that of commercial black glass. The maximum transmission was 27% at 750 mp. The use of nickel and iron oxides is less effective than cobalt oxide for obtaining selenium black glass. 相似文献
43.
Journal of the American Oil Chemists' Society - 相似文献
44.
45.
46.
Mauro Giuffr Silvia Gazzin Caterina Zoratti John Paul Llido Giuseppe Lanza Claudio Tiribelli Rita Moretti 《International journal of molecular sciences》2022,23(24)
Celiac disease (CD) is a complex multi-organ disease with a high prevalence of extra-intestinal involvement, including neurological and psychiatric manifestations, such as cerebellar ataxia, peripheral neuropathy, epilepsy, headache, cognitive impairment, and depression. However, the mechanisms behind the neurological involvement in CD remain controversial. Recent evidence shows these can be related to gluten-mediated pathogenesis, including antibody cross-reaction, deposition of immune-complex, direct neurotoxicity, and in severe cases, vitamins or nutrients deficiency. Here, we have summarized new evidence related to gut microbiota and the so-called “gut-liver-brain axis” involved in CD-related neurological manifestations. Additionally, there has yet to be an agreement on whether serological or neurophysiological findings can effectively early diagnose and properly monitor CD-associated neurological involvement; notably, most of them can revert to normal with a rigorous gluten-free diet. Moving from a molecular level to a symptom-based approach, clinical, serological, and neurophysiology data might help to disentangle the many-faceted interactions between the gut and brain in CD. Eventually, the identification of multimodal biomarkers might help diagnose, monitor, and improve the quality of life of patients with “neuroCD”. 相似文献
47.
Albraa A. Jaber Ahmad Abu Obaid Suresh G. Advani John W. Gillespie Jr 《应用聚合物科学杂志》2024,141(10):e55058
The feasibility of measuring the surface potential decay of polystyrene (PS) film is investigated at room temperature by using Kelvin probe force microscopy (KPFM). The PS film was charged by an ion injection method utilizing Bruker's atomic force microscope (AFM) Nanoman module with a pulse duration of 1 ms, SCM-PIT electrically conductive probe, and a voltage pulse of −250 mV. The surface potential decayed linearly on a semi-log scale with time, where the time decay constant was quantified for relative humidity (RH) = 5% by KPFM at room temperature. The surface potential decayed due to the interaction of the PS film with the hydronium ions available in the environment. Furthermore, the effect of the material forms (film vs. microspheres) on the time decay constant at RH = 5% was investigated. The time decay constants measured using different methods exhibited excellent correlation with the AFM-KPFM. This also confirmed that the results are independent of the material form (microspheres vs. film form). As a result, the proposed method can be used to measure the effect of RH for any PS surface (i.e., particles of various sizes and films) exposed to these environmental conditions. 相似文献
48.
John C. Bell 《Lubrication Science》1990,2(3):195-217
There are numerous wear problems associated with the use of pivoted cam follower valve train systems in modern high-speed automotive engines. These problems have led to the introduction of an increasing number of engines of this type as specification tests to assess the antiwear performance of lubricants. Critical conditions for wear in these systems have been identified by the application of a steady-wear process model to the kinematic analysis of the cam/follower contact cycle. The positions of maximum wear identified by this technique showed better agreement with worn engine components than the more commonly used criteria of maximum contact pressure and oil film thickness. 相似文献
49.
The Ewers method for starch determination is currently the Official EEC method for measurement of starch purity. In this communication we demonstrate that the use of trifluroacetic acid for solubilisation of starch prior to polarimetric measurements is preferred over the use of mineral acids since the degree of hydrolytic degradation observed with this reagent was minimal compared to mineral acids, thereby giving improved starch purity values. Of particular concern we demonstrate that the Ewers method is non-specific in that the addition of an epichlorohydrin cross-linked dextran as an adulterant enhances the value of starch purity obtained. The Ewers method however was able to detect agarose and carboxymethyl cellulose added to starch as adulterants. It is concluded that the Ewers method is not an acceptably satisfactory method for starch purity measurement on which to base quality control or eligibility for rebate and refund schemes. 相似文献
50.
Solmaz Abdolrahimzadeh Martina Formisano Mariachiara Di Pippo Manuel Lodesani Andrew John Lotery 《International journal of molecular sciences》2022,23(14)
Stargardt disease is the commonest juvenile macular dystrophy. It is caused by genetic mutations in the ABCA4 gene. Diagnosis is not always straightforward, and various phenocopies exist. Late-onset disease can be misdiagnosed with age-related macular disease. A correct diagnosis is particularly critical because of emergent gene therapies. Stargardt disease is known to affect retinal pigment epithelium and photoreceptors. Many studies have also highlighted the importance of the choroid in the diagnosis, pathophysiology, and progression of the disease. The choroid is in an integral relationship with the retinal pigment epithelium and photoreceptors, and its possible involvement during the disease should be considered. The purpose of this review is to analyze the current diagnostic tools for choroidal evaluation and the extrapolation of useful data for ophthalmologists and researchers studying the disease. 相似文献