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101.
102.
The present review has attempted to summarize the classic symptoms and signs of aortic valve stenosis, especially in an adult. It is emphasized that all the classic signs rarely are present and their absence may mislead an unwary clinician. The diagnostic help provided by noninvasive tests, including echocardiography and phonocardiography, has been emphasized. A need for cardiac catheterization and angiography in most patients prior to corrective surgery is stressed. The natural history of the disease without operative intervention is dim and a significant risk of sudden death exists. The current surgical approach with immediate and long-term results is summarized. Finally, attention has been drawn to the special clinical circumstances when the aortic valve stenosis provides a strinkingly different clinical picture. We cannot find a better way to end this review than by quoting a warning note given by Thomas Lewis in 1920: "It is the faint cry of an anguished and fast failing muscle, which, when it comes, all should strain to hear, for it is not long repeated. A few months, a few years at most, and the end comes." 相似文献
103.
J.K. Lancaster 《Tribology International》1979,12(2):65-75
Hertzian line contact stresses between a rotating metal cylinder and a reciprocating flat strip of the bearing material are used in an accelerated wear test described in this paper. The test readily demonstrates differences in the wear behaviour between different PTFE-based dry bearing materials. For one widely-used woven PTFE fibre composite, the relationships between wear and stress, temperature, counterface roughness and fluid contamination were shown to be similar to those found in long-term bearing tests 相似文献
104.
Alonso-González P González L Martín-Sánchez J González Y Fuster D Sales DL Hernández-Maldonado D Herrera M Molina SI 《Nanoscale research letters》2010,5(12):1913-1916
In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum
dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming
the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy.
The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric
or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process,
the density of quantum dot molecules finally obtained is low enough (2 × 108 cm−2) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure
level are required. 相似文献
105.
Adherent macrophage populations derived from monocytes isolated from peripheral blood were evaluated for their ability to "shed" the membrane-associated receptor for TNF-alpha (TNFR) following exposure to a calcium ionophor (A23187) and a synthetic chemotactic peptide (fMLP) reagent. A soluble fraction of TNFR was detected in "cell-free" supernatant produced by stimulated macrophage populations applying 125I-TNF-alpha and biotinylated TNF-alpha ligand-binding analysis (96-well format) in combination with conventional autoradiographic techniques. Approximate molecular weight of the shed TNFR glycoprotein fraction was estimated to be 75 kDa based on interpretation of nondenaturing PAGE gels transferred laterally onto sheets of nitrocellulose membrane subsequently probed by ligand-binding analysis applying 125I-TNF-alpha and biotinylated TNF-alpha as detection modalities. Immunorecognition techniques were also employed to detect TNFR fragments shed from macrophages using biotinylated anti-TNFR Type II (75 kDa) monoclonal antibody in combination with conjugated strepavidin:HRPO and a chemiluminescent substrate reagent. In an effort to identify the class of enzyme directly mediating TNFR Type II (75 kDa) shedding, a spectrum of carboxyl- (e.g., aspartate), hydroxyl- (e.g., serine), thiol (e.g., cysteine), and metalo- (e.g., Ca2+, Mg2+) protease-inhibiting agents were evaluated. Experimental findings implied that a carboxy (aspartate) peptidase, and possibly to a lesser extent, serine (hydroxyl), and thiol (cysteine) peptidases participate in macrophage TNFR Type II (75 kDa) shedding phenomena. Subsequent investigations demonstrated that the carboxy (aspartate) peptidase cathepsin-D promoted liberation of TNFR Type II (75 kDa) in unactivated populations of adherent macrophages. In an effort to complement these observations, a protein fraction with presumed carboxy (aspartate) protease activity was isolated from the cell-free supernatant generated by activated populations of adherent macrophages using immobilized pepstatin-A beaded agarose. Exposure of unstimulated populations of adherent macrophages to the partially purified pepstatin-A binding protein fractions resulted in the liberation of a soluble TNFR Type II (75 kDa) fragment based on interpretation of ligand-binding and immunorecognition analysis of samples developed by SDS-PAGE/PAGE format and transferred onto sheets of nitrocellulose membrane. The molecular weight of the macrophage pepstatin-A binding protein fraction was estimated to be 47-52 kDa with lesser bands also visible at approximately 26-32 kDa, and 100 kDa based on SDS-PAGE analysis. Nondenaturing hemoglobin-PAGE substrate gel analysis of protein fractions possessing pepstatin-A binding-avidity detected a protease with a molecular weight of approximately 47-52 kDa that proteolytically digested hemoglobin, in addition to a synthetic cathepsin-D specific peptide substrate. Collective interpretation of these experimental findings directly corresponds with many of the physical (molecular) and functional (biochemical) characteristics known to be associated with the leukocyte carboxy (aspartate) peptidase cathepsin-D, which is a non-metaloprotease known to exert relatively limited proteolytic activity. 相似文献
106.
OBJECTIVE: Many benign breast lesions revealed by mammography show features indicating that the lesions have a high, but not complete, likelihood of being benign. The Breast Imaging Reporting and Data System (BI-RADS) allows radiologists to classify these mammograms as "probably benign finding-short interval follow-up suggested" (category 3). We explored whether certain factors are associated with the use of category 3 in a national cancer detection program. MATERIALS AND METHODS: We analyzed data from the National Breast and Cervical Cancer Early Detection Program, a comprehensive nationwide program that provides cancer screening for low-income and medically underserved women. The study population included all women at least 40 years old who had undergone mammography on or before September 30, 1996 (n = 372,760). RESULTS: Of the 372,760 mammograms, 7.7% were classified as category 3. The probability of receiving a category 3 classification decreased as patients' ages increased. Women who were symptomatic were nearly twice as likely as women who were asymptomatic to receive a category 3 classification, and women whose clinical breast examinations had abnormal findings were more than twice as likely as women with examinations having normal findings to receive a category 3 classification. The percentage of mammograms classified as category 3 by state or tribal organization ranged from 1.4% to 14.0%. CONCLUSION: Several patient variables, including patient symptomatology, were associated with the probability of having a mammogram classified as category 3. One of the most important determinants was where the patient underwent mammography, which suggests that variability exists among radiologists themselves in using this BI-RADS code for "probably benign" mammographic lesions. 相似文献
107.
We report a fully automated mid-IR difference-frequency spectrometer with a spectral resolution under 70 MHz pumped by a pair of conventional room-temperature 800-900-nm diode lasers. 0.1 muW of tunable cw radiation is produced from incident-diode powers of 120 and 75 mW. The system has computer-controlled beam alignment with compact CCD cameras, motorized mirrors and positioners to obtain 0.01 degrees crystal-angle positioning, 4-mum beam overlap at the nonlinear crystal, and automated diode laser beam collimation. Computer-operated frequency control uses temperature tuning and current tuning of the free-running diode lasers. The system has been demonstrated by successfully scanning, without any human intervention, 64 randomly selected acetylene absorption lines between 12 and 15 mum. Spectral scans of ammonia are also presented. This mid-IR spectrometer is suitable for fully automated spectroscopy of an unlimited list of mid-IR frequencies and has the potential to detect any trace gas that has an acceptable absorption line within the large tuning range. 相似文献
108.
Spectroscopic analysis of fire suppressants and refrigerants by laser-induced breakdown spectroscopy 总被引:3,自引:0,他引:3
Laser-induced breakdown spectroscopy is evaluated as a means of detecting the fire suppressants CF(3)Br, C(3)F(7)H, and CF(4) and the refrigerant C(2)F(4)H(2). The feasibility of employing laser-induced breakdown spectroscopy for time- and space-resolved measurement of these agents during use, storage, and recharge is discussed. Data are presented that demonstrate the conditions necessary for optimal detection of these chemicals. 相似文献
109.
GS Cooper A Chak AF Connors DL Harper GE Rosenthal 《Canadian Metallurgical Quarterly》1998,36(4):462-474
OBJECTIVES: The effectiveness of upper endoscopy in unselected patients with upper gastrointestinal hemorrhage has not been well studied. This study was undertaken to identify factors associated with the performance of early endoscopy (ie, within 1 day of hospitalization) and, after adjusting for these factors, to determine associations between early endoscopy and in-hospital mortality, length of stay, and performance of surgery. METHODS: Subjects in this observational cohort study were 3,801 consecutive admissions with upper gastrointestinal hemorrhage to 30 hospitals in a large metropolitan region. Demographic and clinical data were abstracted from hospital records. A multivariable model based on factors that potentially could relate to the decision to perform endoscopy was developed to determine the propensity (0 to 100%) for early endoscopy in each patient. RESULTS: Early endoscopy was performed in 2,240 patients (59%), and although it was not associated with mortality after adjusting for severity of illness among all patients, it was associated with a higher risk of death for patients in the lowest propensity group. Early endoscopy was associated with a lower likelihood of upper gastrointestinal surgery in all patients and in the two highest propensity groups and with a shorter length of stay in the entire cohort and in all subgroups. CONCLUSIONS: In the absence of specific contraindications, early endoscopy should be considered because of associated reductions in length of stay and surgical intervention. Further studies are needed to identify subgroups in whom the procedure may be associated with adverse effects on survival. 相似文献
110.