全文获取类型
收费全文 | 51161篇 |
免费 | 1402篇 |
国内免费 | 189篇 |
专业分类
电工技术 | 642篇 |
综合类 | 668篇 |
化学工业 | 6728篇 |
金属工艺 | 801篇 |
机械仪表 | 1040篇 |
建筑科学 | 1422篇 |
矿业工程 | 411篇 |
能源动力 | 682篇 |
轻工业 | 2863篇 |
水利工程 | 695篇 |
石油天然气 | 91篇 |
武器工业 | 5篇 |
无线电 | 2467篇 |
一般工业技术 | 4770篇 |
冶金工业 | 21915篇 |
原子能技术 | 242篇 |
自动化技术 | 7310篇 |
出版年
2023年 | 276篇 |
2022年 | 316篇 |
2021年 | 437篇 |
2020年 | 198篇 |
2019年 | 250篇 |
2018年 | 728篇 |
2017年 | 904篇 |
2016年 | 1355篇 |
2015年 | 1001篇 |
2014年 | 751篇 |
2013年 | 1035篇 |
2012年 | 2573篇 |
2011年 | 3007篇 |
2010年 | 1079篇 |
2009年 | 1227篇 |
2008年 | 1039篇 |
2007年 | 1020篇 |
2006年 | 887篇 |
2005年 | 3607篇 |
2004年 | 2805篇 |
2003年 | 2283篇 |
2002年 | 1026篇 |
2001年 | 865篇 |
2000年 | 407篇 |
1999年 | 723篇 |
1998年 | 6268篇 |
1997年 | 3926篇 |
1996年 | 2591篇 |
1995年 | 1524篇 |
1994年 | 1141篇 |
1993年 | 1179篇 |
1992年 | 300篇 |
1991年 | 360篇 |
1990年 | 362篇 |
1989年 | 340篇 |
1988年 | 340篇 |
1987年 | 266篇 |
1986年 | 247篇 |
1985年 | 219篇 |
1984年 | 130篇 |
1983年 | 124篇 |
1982年 | 165篇 |
1981年 | 212篇 |
1980年 | 230篇 |
1979年 | 91篇 |
1978年 | 131篇 |
1977年 | 641篇 |
1976年 | 1357篇 |
1975年 | 137篇 |
1973年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Erik Jan Marinissen 《Journal of Electronic Testing》2002,18(4-5):435-454
Modular testing is an attractive approach to testing large system ICs, especially if they are built from pre-designed reusable embedded cores. This paper describes an automated modular test development approach. The basis of this approach is that a core or module test is dissected into a test protocol and a test pattern list. A test protocol describes in detail how to apply one test pattern to the core, while abstracting from the specific test pattern stimulus and response values. Subsequent automation tasks, such as the expansion from core-level tests to system-chip-level tests and test scheduling, all work on test protocols, thereby greatly reducing the amount of compute time and data involved. Finally, an SOC-level test is assembled from the expanded and scheduled test protocols and the (so far untouched) test patterns. This paper describes and formalizes the notion of test protocols and the algorithms for test protocol expansion and scheduling. A running example is featured throughout the paper. We also elaborate on the industrial usage of the concepts described. 相似文献
33.
The expression of cytokeratins (CK), involucrin, vimentin, CD34, and alpha-smooth-muscle actin was studied in fetal and adult hair follicles. The first stage of the developing hair follicle is characterized by palisaded, elongated epithelial cells budding from the epidermal basal layer. These cells express CK5/6, CK14, CK17, CK19, and vimentin. During the following weeks of gestation, different structures in the developing hair follicle can be identified and characterized. The matrical cells display only CK19. The keratinocytes of the outer root sheath express CK5/6, CK14, CK17, CK19, and involucrin; those of the inner root sheath, CK4, CK18, and involucrin; those of the isthmus, the same profile as the ORS. In the infundibulum, the basal-layer keratinocytes express CK5/6, CK14, CK17, and CK19, whereas in the suprabasal layers CK1, CK4, CK10, CK14, and CK17 are seen. The adult hair follicle in anagen fails to express CK19 in the matrical cells and isthmus and both CK17 and CK19 in the infundibulum. These profiles of intermediate filaments and other markers appear to be potentially useful in categorizing neoplasms with apparent follicular differentiation. 相似文献
34.
35.
Phospholamban (PLN) was expressed in Escherichia coli as a protein fusion with glutathione S-transferase (GST). GST-PLN was mostly present in the insoluble protein fraction and accounted for approximately 50% of total insoluble protein. Attempts to suppress inclusion body formation or to use GST as an affinity-purification tag failed. A successful purification method is based on preparative SDS/PAGE and electrodialysis. From 1 g cells we typically purified 13.5 mg fusion protein with a PLN content of 2.8 mg. We genetically inserted an enterokinase (EK) protease site just in front of the PLN sequence and demonstrated the proteolytical liberation of PLN from the carrier protein. The approach described represents a substantial advancement in PLN expression and purification. 相似文献
36.
We report a 20 month old female patient with diploid-triploid mixoploidy (46,XX/69,XXX) syndrome with hypothyroidism and precocious puberty. The triploid cell line was only expressed in the fibroblast culture and comprised the majority (95%) of the cells. Chromosome analysis of the fetal blood sample and peripheral blood sample were normal. The patient shows typical features of full triploidy (growth and severe mental retardation, cranial and facial dysmorphism, complete syndactyly of fingers 3/4, partial syndactyly of toes 2/3) and facial but no body asymmetry. At the age of 5 months central hypothyroidism and precocious puberty were diagnosed. Thin pigmented streaks were visible on the wrists and legs of the patient at the age of 16 months. This is the first patient reported so far with 46,XX/69,XXX mixoploidy suffering from hypothyroidism and precocious puberty. 相似文献
37.
M Souquet T Restle R Krebs SF Le Grice RS Goody BM W?hrl 《Canadian Metallurgical Quarterly》1998,37(35):12144-12152
38.
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
39.
This study was done to determine the occurrence of disease in retained ovaries after hysterectomy. A retrospective analysis of patient charts was performed, comparing the patient reports of women who had secondary ovarian lesions with those whose ovaries showed no pathologic findings during the ten year period of observation (1980 to 1990). The study included 1,265 women with at least one ovary saved after hysterectomy for benign indications. Main outcome measures were ovarian pathologic findings after hysterectomy requiring repeat operation. The overall incidence of lesions in retained ovaries was 3.95 percent. There was a 3 percent risk of having secondary ovarian pathologic findings within three years after hysterectomy, with a decreased risk for the following seven years (mean follow-up time of 60 months, range of three to 120 months). Histologic findings at reoperation included common benign conditions of the ovary. No instance of carcinoma of the ovary was found. The risk of having pathology in the retained ovaries after hysterectomy was significantly higher in women who had only one ovary saved, compared with those who had both ovaries saved (7.63 versus 3.47 percent; p < 0.05). The mean age at hysterectomy was significantly lower in women who had ovarian disorders subsequent to hysterectomy than in those who did not (39.3 versus 43.9 years; p < 0.001). In the group of women with secondary ovarian lesions, mean parity was significantly lower than in those without reoperation (1.22 versus 1.94; p < 0.0001). Women with unilateral oophorectomy at the time of hysterectomy had twice the risk of secondary ovarian lesions, compared with those without oophorectomy at hysterectomy. Determinants, such as age, parity and gravidity must be considered when deciding whether or not to perform oophorectomy at hysterectomy. 相似文献
40.
IH Bjerkli R Myklebust S R?is?nen S Telimaa LE Stenfors 《Canadian Metallurgical Quarterly》1996,36(3):205-213
Dopaminergic agents and carbidopa/levodopa have become the preferred treatment for both the restless legs (RL) syndrome and for periodic limb movements in sleep (PLMS). For once-nightly treatments with carbidopa/ levodopa, a problem with morning end-of-dose rebound increases in leg movements has been reported to occur in the about one-fourth of the patients. In our clinical studies a previously unreported but far more significant problem of markedly augmented RL symptoms occurred in the afternoon and the evening prior to taking the next nightly dose. A systematic prospective evaluation of this augmentation in 46 consecutive patients treated with carbidopa/ levodopa for RL syndrome or PLMS disorder found this augmentation to be the major adverse effect of treatment. Augmentation occurred for 31% of PLMS patients and 82% of all RL patients. It was greater for subjects with more severe RL symptoms and for patients on higher doses (> or = 50/200 mg carbidopa/levodopa) but was unrelated to gender, age or baseline severity of PLMS. This augmentation was severe enough to require medication change for 50% of the RL patients and 13% of PLMS patients. Augmentation resolved with cessation of the medication and could be minimized by keeping the dose low. 相似文献