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981.
Concentrations of native and gold defects in HgCdTe from first principles calculations 总被引:1,自引:0,他引:1
We have studied the defect formation energies of the various native (vacancies, interstitials, and antisites) and Au defects
in Hg1−xCdxTe using density functional-based total energy calculations with ultrasoft pseudo-potentials. These studies are important
for infrared (IR) detection technology where the device performance can be severely degraded because of defects. To calculate
formation energies, we modeled the neutral and charged defects using supercells containing 64 atoms. From the formation energies,
we have determined the defect concentrations as a function of stoichiometry and temperature. We find the prevalent neutral
defects to be Au at the Hg site (AuHg
), Hg vacancies (VHg
), and Te antisites (TeHg
). We have also explicitly studied charged defects and have found Te
Hg
2+
, Au
Hg
1−
, V
Hg
1−
, V
Hg
2−
, and V
Te
2+
to have low formation energies. We have identified AuHg
to be the prevalent Au defect, having concentrations several orders of magnitude greater than the other Au defects. We find
that the charge state of VHg is primarily (1−) or (2−) depending on the electronic chemical potential. 相似文献
982.
Gerald J. Smith Cara L. Dunford Anthony D. Woolhouse Timothy G. Haskell Thomas H. Barnes 《Optical Materials》2002,19(4):395-401
New transient volume holographic recording materials are described in this report. These consist of either coronene or 1,2;5,6-dibenzanthracene incorporated into polymethylmethacrylate. The largely amplitude, volume holograms formed as a result of triplet-state absorption have lifetimes of 6.4 and 0.9 s respectively and diffraction efficiencies close to the predicted values of 10−4. Production of permanent holograms has been prevented by careful control of the polymerization conditions to produce a matrix of sufficient rigidity to prevent reactions between the triplet states and the polymer. By using spectrally well separated write and read wavelengths, erasure of the holograms by the read beam is avoided. 相似文献
983.
984.
Scientists and engineers are currently moving into a new era to develop precise and intelligent mini-structures and microsystems. The study of mini-structures and microsystems is a rapidly growing area of research with a great potential to accomplish useful tasks in numerous applications. In this paper, a new fabrication technology for microstructures based on the chemical liquid deposition (CLD) is presented. This technology is based on the following principles: micro-droplets of a cold (room temperature) solution or liquid reactant are sprayed from a nozzle and make contact with a hot substrate, the droplets will evaporate, decompose, or react, and then the reacted solid products will deposit on the substrate. By controlling the motion of the nozzle and the spray time, a desired 3D microstructure of the deposited material can be formed through a layer-by-layer scanning technique. The working principle, available materials as well as the process control and modeling is discussed and some preliminary results are presented. 相似文献
985.
JA Fernández JH Griffin GT Chang J Stam PH Reitsma RM Bertina BN Bouma 《Canadian Metallurgical Quarterly》1998,24(2):101-12; discussion 113
Human protein S binds to C4b-binding protein (C4BP) both in plasma and in a system using purified proteins. Amino acid residues 420-434 of the first disulfide loop of the sex hormone binding globulinlike domain of protein S are involved in the interaction of protein S with C4BP. To define the involvement of specific polar amino acids within residues 420-434, we studied in parallel synthetic protein S peptides and recombinant protein S variants containing the same amino acid replacements, K423E, E424K, Q427E and K429E. Synthetic peptide analogs of peptide PSP-420 (residues 420-434) were assayed for binding C4BP and as inhibitors of complex formation. The PSP-420 peptide and the analogous peptide with the substitution E424K, but not the peptides containing the substitutions K423E and K429E, were able to bind C4BP. Recombinant proteins with mutations of K423E, Q427E and K429E showed reduced affinity for C4BP compared to plasma protein S, recombinant wild type protein S, or E424K-protein S. These results suggest that Lys-423, Gln-427 and Lys-429 of protein S are important for normal binding to C4BP. The anti-protein S monoclonal antibody LJ-56, raised against peptide PSP-420, recognizes only free protein S and inhibits complex formation with C4BP. Antibody LJ-56 recognized the E424K and Q427E peptides but not the K423E or K429E peptides. Similarly, the E424K and Q427E protein S mutants were recognized by LJ-56, whereas the K423E and K429E protein S mutants were not recognized. This suggests that both in the peptide PSP-420 and in protein S, Lys-423 and Lys-429 significantly contribute to binding to antibody LJ-56. These results demonstrate that protein S residues 423, 427 and 429, but not residue 424, are involved in binding to both the antibody LJ-56 and to C4BP. When peptides PSP 420 and SL-6 (residues 447-460) with carboxyterminal amide or carboxylate moieties were compared to their ability to inhibit C4BP-protein S complexation, PSP-420-amide was the most potent. This finding together with the other results described here supports the hypothesis that the residues 420 and 434 in protein S provides a major binding site for C4BP. 相似文献
986.
987.
BACKGROUND: Spirituality is receiving greater attention in the medical literature, especially in the family practice journals. A widely applicable instrument to assess spirituality has been lacking, however, and this has hampered research on the relationship between spirituality and health in the clinical setting. METHODS: A new instrument, called the Spiritual Involvement and Beliefs Scale, was designed to be widely applicable across religious traditions, to assess actions as well as beliefs to address key components not assessed in other available measures, and to be easily administered and scored. The instrument is a questionnaire containing 26 items in a modified Likert-type format. Following careful pretesting, the instrument was administered to 50 family practice patients and 33 family practice educators. The validity and reliability of the instrument were then evaluated. RESULTS: By several measures, instrument reliability and validity are very good, with high internal consistency (Cronbach's alpha = .92); strong test-retest reliability (r = .92); a clear four-factor structure; and a high correlation (r = .80) with another established measure of spirituality, the Spiritual Well-Being Scale. CONCLUSIONS: The Spiritual Involvement and Beliefs Scale (SIBS) appears to have good reliability and validity. Compared with other instruments that assess spirituality, the SIBS has several theoretical advantages, including broader scope, use of terms that avoid cultural-religious bias, and assessment of both beliefs and actions. More testing is underway to further assess its usefulness. 相似文献
988.
RM Pitti SA Marsters DA Lawrence M Roy FC Kischkel P Dowd A Huang CJ Donahue SW Sherwood DT Baldwin PJ Godowski WI Wood AL Gurney KJ Hillan RL Cohen AD Goddard D Botstein A Ashkenazi 《Canadian Metallurgical Quarterly》1998,396(6712):699-703
Fas ligand (FasL) is produced by activated T cells and natural killer cells and it induces apoptosis (programmed cell death) in target cells through the death receptor Fas/Apol/CD95. One important role of FasL and Fas is to mediate immune-cytotoxic killing of cells that are potentially harmful to the organism, such as virus-infected or tumour cells. Here we report the discovery of a soluble decoy receptor, termed decoy receptor 3 (DcR3), that binds to FasL and inhibits FasL-induced apoptosis. The DcR3 gene was amplified in about half of 35 primary lung and colon tumours studied, and DcR3 messenger RNA was expressed in malignant tissue. Thus, certain tumours may escape FasL-dependent immune-cytotoxic attack by expressing a decoy receptor that blocks FasL. 相似文献
989.
We describe the isolation of a variant of Mu transposase (MuA protein) which can recognize altered att sites at the ends of Mu DNA. No prior knowledge of the structure of the DNA binding domain or its mode of interaction with att DNA was necessary to obtain this variant. Protein secondary structure programs initially helped target mutations to predicted helical regions within a subdomain of MuA demonstrated to harbor att DNA binding activity. Of the 54 mutant positions examined, only two showed decreased affinity for att DNA, while eight others affected assembly of the Mu transpososome. A variant impaired in DNA binding [MuA(R146V)], and predicted to be in the recognition helix of an HTH motif, was challenged with altered att sites created from degenerate oligonucleotides to select for novel DNA binding specificity. DNA sequences bound to MuA(R146V) were detected by gel-retardation, and following several steps of PCR amplification/enrichment, were identified by cloning and sequencing. The strategy allowed recovery of an altered att site for which MuA(R146V) showed higher affinity than for the wild-type site, although this site was bound by wild-type MuA as well. The altered association between MuA(R146V) and an altered att site target was competent in transposition. We discuss the strengths and limitations of this methodology, which has applications in dissecting the functional role of specific protein-DNA associations. 相似文献
990.
H Nakanishi RM Taylor AL Hawkins CA Griffin GR Martin A Passaniti 《Canadian Metallurgical Quarterly》1994,58(4):592-601
Three stable carcinoma cell lines, designated RM22-F5, RM17-5R, and RM1-4, were established from spontaneously occurring mammary carcinomas in old, outbred, female Wistar rats. The RM22-F5 and RM17-5R cells were keratin-positive and formed epithelial monolayers, whereas RM1-4 cells exhibited a spindle-like morphology and intense vimentin staining. When injected into nude mice, RM22-F5, RM17-5R and RM1-4 cells formed well-differentiated, poorly differentiated and undifferentiated carcinomas, respectively. The relative growth rates of the tumor cells in vitro were RM1-4 > RM22-F5 > RM17-5R. The growth of RM22-F5, but not of RM17-5R and RM1-4 cells, was significantly stimulated by insulin, epidermal growth factor, dexamethasone, 17 beta-estradiol and progesterone in vitro. Ovariectomy reduced the growth of RM22-F5 cells in vivo and these cells (but not RM1-4 or RM17-5R) were estrogen-receptor (ER)-positive. None of the lines were positive for the progesterone receptor (PR). Spontaneous lung and lymph-node metastases were observed in nude mice injected with RM22-F5 or RM17-5R cells, respectively. In contrast, RM1-4 cells were non-metastatic but invasive. Karyotype analysis revealed that RM22-F5 cells were hyperdiploid, RM17-5R were hypotetraploid, and RM1-4 were diploid with a sizeable insertion in chromosome 1. A point mutation in codon 12 (G to A transition) and loss of the normal allele of the H-ras-1 gene was detected in the DNA from RM22-F5 cells. No p53 mutations were apparent in any of the cell lines. The results indicate that RM22-F5 cells are hormone-dependent with an ER+/PR- phenotype, while the RM17-5R and RM1-4 lines are hormone-independent and ER-/PR-. These cell lines exhibit the spectrum of biological properties and genetic alterations observed in human breast cancers and may, therefore, be novel and useful models for understanding sporadic breast cancer in post-menopausal women. 相似文献