全文获取类型
收费全文 | 303953篇 |
免费 | 3681篇 |
国内免费 | 1140篇 |
专业分类
电工技术 | 5454篇 |
综合类 | 817篇 |
化学工业 | 48301篇 |
金属工艺 | 12872篇 |
机械仪表 | 9278篇 |
建筑科学 | 7427篇 |
矿业工程 | 2119篇 |
能源动力 | 6911篇 |
轻工业 | 26832篇 |
水利工程 | 3545篇 |
石油天然气 | 8150篇 |
武器工业 | 103篇 |
无线电 | 32426篇 |
一般工业技术 | 60763篇 |
冶金工业 | 52909篇 |
原子能技术 | 8127篇 |
自动化技术 | 22740篇 |
出版年
2021年 | 2424篇 |
2018年 | 4050篇 |
2017年 | 4051篇 |
2016年 | 4347篇 |
2015年 | 2943篇 |
2014年 | 4764篇 |
2013年 | 12726篇 |
2012年 | 7484篇 |
2011年 | 9862篇 |
2010年 | 8103篇 |
2009年 | 9188篇 |
2008年 | 9430篇 |
2007年 | 9329篇 |
2006年 | 8269篇 |
2005年 | 7663篇 |
2004年 | 7170篇 |
2003年 | 6992篇 |
2002年 | 7223篇 |
2001年 | 7044篇 |
2000年 | 6468篇 |
1999年 | 6406篇 |
1998年 | 14861篇 |
1997年 | 11143篇 |
1996年 | 8682篇 |
1995年 | 6632篇 |
1994年 | 6010篇 |
1993年 | 5890篇 |
1992年 | 4597篇 |
1991年 | 4574篇 |
1990年 | 4424篇 |
1989年 | 4471篇 |
1988年 | 4403篇 |
1987年 | 3762篇 |
1986年 | 3770篇 |
1985年 | 4348篇 |
1984年 | 4161篇 |
1983年 | 3804篇 |
1982年 | 3604篇 |
1981年 | 3722篇 |
1980年 | 3588篇 |
1979年 | 3554篇 |
1978年 | 3698篇 |
1977年 | 4154篇 |
1976年 | 5266篇 |
1975年 | 3389篇 |
1974年 | 3273篇 |
1973年 | 3305篇 |
1972年 | 2900篇 |
1971年 | 2696篇 |
1970年 | 2302篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
A Veldman G J Borggreve E J Mulders D van de Lagemaat 《Food Additives & Contaminants》1992,9(6):647-655
The mycotoxin contamination of feed components used by the Dutch cooperative feed industry was surveyed to estimate the risk for animal production losses. Of 89 randomly and 6 selectively taken samples of raw materials harvested in 1988 and 1989 27% were contaminated with ochratoxin A (OCHRA), 31% with zearalenone (ZEA) and 20% with deoxynivalenol (DON). The mean content (microgram/kg) of all positive randomly taken samples was 18 (OCHRA), 62 (ZEA) and 630 (DON). The highest level (microgram/kg) for all samples was 120 (OCHRA) in barley, 3100 (ZEA) in corn cob mix and 1900 (DON) in maizegluten feed. The results of this survey show that feed components are often contaminated with mycotoxins. However, the contamination level could only sporadically cause production losses in animal husbandry. 相似文献
942.
We have localized gene MSS51 on chromosome XII of Saccharomyces cerevisiae between the RDN1 and CDC42 loci. 'Head to head' with MSS51 is another gene, QRI5, the function of which is unknown. However, the proximity of these genes, the structure of the intergenic region and the presence of an ABF1 binding site right in the middle of this region suggest that the MSS51 and QRI5 expressions are submitted to a common regulatory process. 相似文献
943.
D Piazzalunga P Fenaroli A Giovanelli R Sacco G Cassinelli 《Canadian Metallurgical Quarterly》1995,50(1-2):139-142
The authors describe a case of one patient who underwent duodenocephalopancreasectomy for CBD cancer 6 years ago and developed gastrointestinal bleeding caused by a fistula between the hepatic artery and the jejunal stump. They discuss the differential diagnosis problem in the gastrointestinal bleeding syndrome caused by this rare pathology. 相似文献
944.
Zirconia-supported alkali ions, containing Na, from 0.74 to 3.61 wt.%, and K, from 0.91 to 4.76 wt.%, have been studied by X-Ray Photoelectron Spectroscopy, X-ray diffraction and chemical analyses. The results show that the alkali ions remain dispersed on the zirconia surface. After treatment at 773 K in air, 5h, the Na containing samples maintain a good dispersion at low Na content, whereas for the more concentrated samples, agglomeration and incorporation in solid solution have been detected. The K based system shows neither agglomeration nor incorporation in solid solution of potassium ions. The XPS intensity ratios are compared with calculated values, according to different models, to account for the changes in surface morphology. 相似文献
945.
946.
947.
Intelligent assistance for software development and maintenance 总被引:2,自引:0,他引:2
An environment is described, called Professor Marvel, that provides early error checking and answers questions about the program under development. The environment has a certain understanding of the systems being developed and how to use tools to produce software. It aids individual programmers and helps coordinate programming teams. The key components of Marvel are a database that stores data represented as objects, as in object-oriented languages, and a model of the development process that imposes a structure on programming activities. Marvel's support of insight and of opportunistic processing is discussed at length, as is the handling of side effects. A sample session is described 相似文献
948.
949.
Frank G. Pagan 《Software》1988,18(6):509-527
There is an effective and quite general method of manually deriving compilers from programming-language interpreters without dealing directly with machine language. The method is an implementation of the largely theoretical and under-appreciated concept of partial computation, but can be understood on its own terms. It involves the translation of a source program's intermediate form into the interpreter's implementation language. This paper shows how the method can be used to transform both a sample iterative interpreter and a sample recursive interpreter into compilers. The result can be a large gain in program execution speed. Other advantages of the method, including the ease and practicality of applying it, are discussed. 相似文献
950.
A. G. Davidson 《Drug development and industrial pharmacy》1995,21(19):2167-2186
The results of a multinational survey of the quality of carbamazepine tablets are reported. A total of 22 laboratories in nineteen countries worldwide participated in the study conducted under the auspices of the Official Laboratories and Medicines Control Services (OLMCS) Section of FIP. The results of tests conducted on 86 samples representing at least 34 different products, comprising the innovator's product Tegretol, 13 other branded products and 20 generic products, are presented. Most products fulfilled the requirements of pharmacopoeial quality standards. However, there were marked differences in dissolution behaviour which suggest that not all products are bioequivalent with each other. Most of the products tested would not comply with a requirement for the percentage of carbamazepine released at 15 minutes, that is proposed for inclusion in the USP monograph for Carbamazepine Tablets. 相似文献