全文获取类型
收费全文 | 846024篇 |
免费 | 10761篇 |
国内免费 | 2642篇 |
专业分类
电工技术 | 15597篇 |
综合类 | 940篇 |
化学工业 | 129006篇 |
金属工艺 | 33515篇 |
机械仪表 | 24638篇 |
建筑科学 | 21081篇 |
矿业工程 | 3736篇 |
能源动力 | 21937篇 |
轻工业 | 77661篇 |
水利工程 | 8107篇 |
石油天然气 | 13482篇 |
武器工业 | 71篇 |
无线电 | 95167篇 |
一般工业技术 | 158759篇 |
冶金工业 | 168572篇 |
原子能技术 | 16499篇 |
自动化技术 | 70659篇 |
出版年
2021年 | 7170篇 |
2020年 | 5226篇 |
2019年 | 6741篇 |
2018年 | 11277篇 |
2017年 | 10991篇 |
2016年 | 11764篇 |
2015年 | 8156篇 |
2014年 | 13462篇 |
2013年 | 38286篇 |
2012年 | 21616篇 |
2011年 | 29914篇 |
2010年 | 23781篇 |
2009年 | 26572篇 |
2008年 | 27567篇 |
2007年 | 27406篇 |
2006年 | 24325篇 |
2005年 | 22120篇 |
2004年 | 21269篇 |
2003年 | 20934篇 |
2002年 | 20374篇 |
2001年 | 20177篇 |
2000年 | 18903篇 |
1999年 | 20028篇 |
1998年 | 51027篇 |
1997年 | 35864篇 |
1996年 | 27750篇 |
1995年 | 20926篇 |
1994年 | 18298篇 |
1993年 | 17960篇 |
1992年 | 13058篇 |
1991年 | 12393篇 |
1990年 | 12149篇 |
1989年 | 11786篇 |
1988年 | 11244篇 |
1987年 | 9829篇 |
1986年 | 9783篇 |
1985年 | 11176篇 |
1984年 | 10396篇 |
1983年 | 9290篇 |
1982年 | 8737篇 |
1981年 | 8884篇 |
1980年 | 8471篇 |
1979年 | 8138篇 |
1978年 | 7987篇 |
1977年 | 9612篇 |
1976年 | 13032篇 |
1975年 | 6995篇 |
1974年 | 6567篇 |
1973年 | 6722篇 |
1972年 | 5595篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Pigmented vulvar lesions were observed in a child during a sexual abuse evaluation. Gross examination of the lesions appeared most consistent with bowenoid papulosis; however, biopsy confirmed the lesions to be pigmented apocrine hamartomas. To our knowledge, these rare and benign tumors have never been described as pigmented, but should be added to the differential diagnosis of pigmented vulvar lesions. 相似文献
102.
M Camilleri 《Canadian Metallurgical Quarterly》1996,25(2):361-378
Gastrointestinal symptoms are often encountered in patients with diabetes mellitus. Symptoms may arise in any region of the alimentary tract; common symptoms are heartburn, nausea, vomiting, diarrhea, constipation, fecal incontinence, and abdominal pain. This article reviews practical approaches to the identification of the pathophysiologic mechanisms involved in diabetic enteropathies and their complications and briefly outlines strategies to treat these symptoms. Particular emphasis is placed on applied physiologic tests and the choice of pharmacotherapy (e.g., cisapride, erythromycin, or octeotide). The current role of pancreatic transplantations also is briefly reviewed. 相似文献
103.
LW Seymour H Soyez A De Marre MA Shoaibi EH Schacht 《Canadian Metallurgical Quarterly》1996,11(5):351-365
Prodrugs of mitomycin C (MMC) based on soluble poly-[N-(2-hydroxyethyl)-L-glutamine] (pHEG) polymers have been evaluated as tumour-targeted drugs. These materials are designed to exploit the enhanced permeability of tumour vasculature, combining a passive tumour tropism with decreased systemic liberation of free MMC. A tri- or tetrapeptide linkage (e.g. Gly-Phe-Ala-Leu) between pHEG and the aziridine nitrogen of MMC can combine good hydrolytic stability with rapid cleavage by lysosomal enzymes, releasing free MMC. The conjugates showed decreased systemic toxicity and could be administered to mice at a total MMC dose of 15 mg/kg i.v., compared with just 6 mg/kg for free MMC. Conjugates also showed better activity against animal models of established tumours, achieving up to 77% increased life span (ILS) against solid P388 leukaemia, compared with only 23% for free MMC, and up to 121% ILS against solid C26 colorectal carcinoma, compared with no activity for the free drug. Improving the therapeutic index of anticancer drugs by combining tumour tropism with decreased systemic toxicity is a versatile approach that should produce a new generation of improved anticancer agents. 相似文献
104.
The impact of crosstalk in an arrayed-waveguide N×N wavelength multiplexer is investigated precisely in relation to its application to wavelength-routing N×N all optical networks. In such systems multiple crosstalk light which has the same wavelength as the signal results in signal-crosstalk beat noise. We confirm that the noise is Gaussian and obtain the relation between crosstalk and power penalty. It is shown that the crosstalk must be less than -38 dB for a 16×16 system to keep the power penalty below 1 dB at a bit error rate of 10-9 相似文献
105.
In summary, recent literature indicates that the complications of chronic otitis media have been decreasing. However, even with the advent of modern and more powerful antimicrobials and aggressive surgical eradication of disease, the morbidity and mortality are still high. Some complications may initially be quite obvious and some complications may be quite subtle. Therefore, the most important tools in making early diagnosis are careful history and physical examination, and a high index of suspicion for impending complications. 相似文献
106.
D Sternberg A Peled E Shezen O Abramsky W Jiang F Bertolero D Zipori 《Canadian Metallurgical Quarterly》1996,2(1):29-38
The immunological agglutination reactions of physically absorbed F(ab')2 molecules onto anionic and cationic latex particles have been investigated by means of optical absorbance measurements. These measurements have been conducted under different conditions to determine the most influential factors. Surface F(ab')2 and BSA densities, particle concentration in the reaction medium and polyethylene glycol concentration are some of these factors. Sensitized cationic and anionic latexes differ considerably with respect to their colloidal stability and reactivity. As a general rule, the sensitized cationic latex has a relatively higher colloidal stability and hence, it provides reagents with a better optical response. Less than 0.025 microgram/ml of C-reactive protein has been detected using this particle enhanced optical immunoassay. 相似文献
107.
The thermal expansion of tellurides of germanium, bismuth, and intermetallic compounds is investigated over the temperature range 293-973 K.Belarusian Agricultural Technical University, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 5, pp. 612–616, May 1994. 相似文献
108.
In a prospective study we found good results concerning postoperative complications (21%), perioperative lethality (3.2%) and lethality during hospital stay (6.5%) after implantation of dynamic hip screws (DHS) in patients with per- and subtrochanteric fractures of the femur. The ability to walk, as well as housing and social care postoperatively and follow-up for at least six months after dismissal demonstrates the importance of these fractures for the elderly. One of three patients needs professional care, 21% at home, 13% in nursing homes. Six months after operation the lethality is nearly 20%, i.e. three times higher than in hospital. These are the essential data for all techniques of osteosynthesis used in patients with these fractures, which could only be documented in prospective studies. 相似文献
109.
110.