全文获取类型
收费全文 | 1943篇 |
免费 | 0篇 |
专业分类
化学工业 | 10篇 |
机械仪表 | 1篇 |
轻工业 | 5篇 |
无线电 | 1篇 |
一般工业技术 | 1篇 |
冶金工业 | 1921篇 |
自动化技术 | 4篇 |
出版年
2022年 | 1篇 |
2013年 | 1篇 |
2011年 | 1篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
1999年 | 65篇 |
1998年 | 580篇 |
1997年 | 309篇 |
1996年 | 186篇 |
1995年 | 101篇 |
1994年 | 116篇 |
1993年 | 113篇 |
1992年 | 6篇 |
1991年 | 19篇 |
1990年 | 21篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 19篇 |
1980年 | 21篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 66篇 |
1976年 | 160篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1943条查询结果,搜索用时 0 毫秒
11.
12.
Antisera made against whole cells of Bordetella avium protected turkeys against disease signs of turkey coryza, but antiserum against the dermonecrotic heat-labile toxin (DHLT) did not. Neither antiserum against whole cells nor antiserum against DHLT protected turkeys against colonization of the trachea by B. avium. At least 25 bands in whole cell lysate of B. avium separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) reacted in immunoblots with protective antiserum. These bands occurred at < 40 kDa and > 105.3 kDa. DHLT had an isoelectric point (pI) in the range pH 6.3-6.7. Following SDS-PAGE of isoelectric-focused fractions, two bands were recognized by anti-DHLT with immunoblots of pI 6.3, pI 6.5, and pI 6.7 fractions separated by SDS-PAGE. 相似文献
13.
RB Jones PR Pomrehn RE Mecklenburg EA Lindsay M Manley JK Ockene 《Canadian Metallurgical Quarterly》1993,124(9):92-104; discussion 106-8
The National Cancer Institute's program to help dentists reduce tobacco use among their patients is part of the Community Intervention Trial for Smoking Cessation, a 22-community, randomly controlled trial of an intervention program for smoking cessation. Results of COMMIT baseline surveys of dentists in the 11 intervention communities are presented. 相似文献
14.
Basal cell carcinoma (BCC) is the most common type of skin cancer and the incidence of BCC is expected to rise, with increased demand on dermatology resources. Little is known of the effect on people's lives of having skin cancer. The aim of this study was to quantify the handicap caused gy basal cell carcinomas before and after therapy. Forty-four patients (22 males, mean age = 65 yrs, range = 35-81 yrs) with 48 BCCs were recruited and 37 patients completed the study. Each patient completed the UK Sickness Impact Profile (UKSIP) and the Dermatology Life Quality Index (DLQI) at the initial visit to the dermatology clinic, 1 week after treatment and 3 months after treatment. Lesions had been present for a mean of 25 months (range = 1-240 months), their mean diameter was 9.6mm (range = 3-35mm) and the sites were head and neck (79%), trunk (17%) and limbs (4%). There was no relationship between the quality of life score and size of lesion. Overall the scores at presentation were very low, rising 1 week after treatment and falling to below the initial scores at 3 months (mean UKSIP 0.4%, 0.7%, 0.13%; mean DLQI 5.3% 8.7%, 1.2%). BCCs cause little handicap. This may explain the delay in seeking medical attention and should be considered in planning public health education about BCCs. 相似文献
15.
RB Hudson 《Canadian Metallurgical Quarterly》1994,34(6):743-748
The analysis of genomic DNA fragment patterns has revealed as a powerful tool for strain discrimination in Staphylococcus aureus; for use as an epidemiological marker, stability during the course of an outbreak is an essential prerequisite. Genomic DNA fragment patterns (SmaI restriction, pulsed-field electrophoresis) of four different epidemic MRSA strains were compared along with intra- and interhospital and country-wide spread over more than 12 months in Germany. Strain I was isolated from infections in 8 hospitals. In one hospital a subclone arised which differed from the original strain by 4 fragments. Strain II was spread among 4 hospitals, isolates from three of these hospitals exhibited a variability of one to three fragments in the 150-200 kb range. Two hospitals in the Hannover-area were affected by strain III; in 17 isolates of this strain a variability up to three fragments was found in the 170-200 kb range. Strain IV was isolated from 19 cases of infections in 3 hospitals in Berlin. The fragment patterns were completely stable. When S. aureus strains are typed by genomic DNA fragment patterns, a variability in a definite range of molecular masses during the course of an epidemic should be taken into consideration. 相似文献
16.
17.
CONTEXT: Adolescent smoking prevalence is tracked annually and has increased since 1991. In contrast, little is known about trends in smoking among college students, a group that has previously been more resistant to tobacco use than other young adults. OBJECTIVE: To examine changes in cigarette smoking among college students between 1993 and 1997 and among different types of students and colleges. DESIGN: Self-administered survey (Harvard School of Public Health College Alcohol Study). SETTING: One hundred sixteen nationally representative 4-year colleges. SUBJECTS: A total of 15103 randomly selected students in 1993 (70% response rate) and 14251 students in 1997 (60% response rate). MAIN OUTCOME MEASURES: Self-reports of cigarette smoking in the past 30 days and in the past year, age at smoking first cigarette, and number of attempts to quit. RESULTS: Over 4 years, the prevalence of current (30-day) cigarette smoking rose by 27.8%, from 22.3% to 28.5% (P<.001). The increase was observed in 99 of 116 colleges and was statistically significant (P<.05) in 27 (23%) of them. Current smoking increased across all student subgroups (defined by sex, race/ethnicity, and year in school) and in all types of colleges. Smoking is rising faster in public schools (from 22.0% to 29.3%) than in private schools (from 22.9% to 26.8%). Eleven percent of college smokers had their first cigarette and 28% began to smoke regularly at or after age 19 years, by which time most were already in college. Half of current smokers tried to quit in the previous year; 18% had made 5 or more attempts to quit. CONCLUSIONS: Cigarette use is increasing on campuses nationwide in all subgroups and types of colleges. Substantial numbers of college students are both starting to smoke regularly and trying to stop. National efforts to reduce smoking should be extended to college students. 相似文献
18.
RB Singh H Mori J Chen S Mendis M Moshiri S Zhu SH Kim RG Sy AM Faruqui 《Canadian Metallurgical Quarterly》1996,3(6):489-494
PURPOSE: Two types of glass wool were used to remove leukocytes in semen for evaluation of reactive oxygen species production by spermatozoa in oligozoospermic patients with leukocytospermia. METHODS: Semen samples were prepared using fine-structure glass wool (SpermFertil) and coarse-structure glass wool. In each treatment group, native semen was evaluated for sperm concentration, percentage motility, viability, leukocyte concentration, and production of reactive oxygen species. RESULTS: Electron microscopically, SpermFertil showed a higher number of leukocytes attached to the fibers compared to coarse-structure glass wool. Leukocytes in native semen and after glass wool filtration as determined by peroxidase cytochemistry confirmed this observation. Reactive oxygen species decreased from 45.303 counts/10(7) viable cells in native semen to 15.806 counts/10(7) cells in coarse structure wool and 7.465 counts/10(7) cells in Spermfertil, respectively. CONCLUSIONS: Removal of leukocytes from semen of oligozoospermic patients by means of glass wool filtration is a useful method to distinguish production of reactive oxygen species by leukocytes versus sperm cells. 相似文献
19.
20.
RB Nagle 《Canadian Metallurgical Quarterly》1996,15(4):473-482
The human prostate is composed of a series of tubular-alveolar glands and their ducts surrounded by a fibro-muscular stroma. The parenchymal glands secrete the seminal fluid and are anatomically arranged into the central, peripheral, and transitional zones. In this chapter the pattern of intermediate filament expression by the various epithelial components of the ducts, tubuloalveolar glands, and stroma are described. The changes which occur during malignant transformation from normal glands to prostatic intraepithelial neoplasia and subsequent invasive carcinoma are presented. The usefulness of cytokeratin markers in the diagnosis of prostate carcinoma is also discussed. 相似文献